The Safety of Domestic Robotics: A Survey of Various Safety-Related Publications
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paper_title: Design of human symbiotic robot TWENDY-ONE

paper_content:

In this paper, we propose a sophisticated design of human symbiotic robots that provide physical supports to the elderly such as attendant care with high-power and kitchen supports with dexterity while securing contact safety even if physical contact occurs with them. First of all, we made clear functional requirements for such a new generation robot, amounting to fifteen items to consolidate five significant functions such as “safety”, “friendliness”, “dexterity”, “high-power” and “mobility”. In addition, we set task scenes in daily life where support by robot is useful for old women living alone, in order to deduce specifications for the robot. Based on them, we successfully developed a new generation of human symbiotic robot, TWENDY-ONE that has a head, trunk, dual arms with a compact passive mechanism, anthropomorphic dual hands with mechanical softness in joints and skins and an omni-wheeled vehicle. Evaluation experiments focusing on attendant care and kitchen supports using TWENDY-ONE indicate that this new robot will be extremely useful to enhance quality of life for the elderly in the near future where human and robot co-exist.
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paper_title: Towards the Development of International Safety Standards for Human Robot Interaction

paper_content:

This paper is an overview of the work being performed by the ISO committee TC184/SC2 “Robots and Robotic Devices”. SC2 is developing safety standards for robotic applications in personal and medical care, as well as revising existing industrial robot standards with requirements for new applications. A key driver of the new standards is the need for safety guidelines for human robot interaction, as the new applications involve much more extensive HRI behavior than previous generations of industrial robots. The paper summarizes the content of a revision to ISO 10218 for industrial robots, the development of a new standard ISO/NP 13482 for service robots in personal care, and discusses future work in standards for medical care robots and other areas.
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paper_title: An Overview of the DDT Project

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The DDT Project on rescue robots and related technologies was carried out in Japan’s fiscal years 2002–2006 by nationwide researchers, and was organized by International Rescue System Institute. The objective of this project was to develop practical technologies related to robotics as a countermeasure against earthquake disasters, and include robots, intelligent sensors, information equipment, and human interfaces that support emergency responses such as urban search and rescue, particularly victim search, information gathering, and communication. Typical technologies are teleoperated robots for victim search in hazardous disaster areas, and robotic systems with distributed sensors for gathering disaster information to support human decision making. This chapter introduces the objective of this project, and a brief overview of the research results.
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paper_title: Novel activity on international safety standardization for personal care robots

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The authors introduce an activity of a new working group under ISO/TC184/SC2 which is approved to formulate a new international safety standard “Robots and robotic devices — Safety requirements — Non-medical personal care robot” associated with robots that are allowed to coexist in human environments for the purpose of providing humans with various services. The standard includes risk assessment and risk elimination/reduction information for the design stage of personal care robots. The paper briefly delivers the points in the risk assessment and risk elimination/reduction processes, which have been discussed in the working group: Beginning with the scope, the main framework and roadmap of formulating the standard are also described.
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paper_title: Safety and reliability assessment techniques in robotics

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A robot has to be safe and reliable. An unreliable robot may become the cause of unsafe conditions, high maintenance costs, inconvenience, etc.Over the years, in general safety and reliability areas various assessment methods have been developed, e.g. failure mode and effects analysis, fault tree analysis, and Markovian analysis. In view of these, this paper presents an overview of the most suitable robot safety and reliability assessment techniques.
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paper_title: Safe and dependable physical human-robot interaction in anthropic domains: State of the art and challenges

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In the immediate future, metrics related to safety and dependability have to be found in order to successfully introduce robots in everyday environments. The crucial issues needed to tackle the problem of a safe and dependable physical human-robot interaction (pHRI) were addressed in the EURON Perspective Research Project PHRIDOM (Physical Human- Robot Interaction in Anthropic Domains), aimed at charting the new "territory" of pHRI. While there are certainly also "cognitive" issues involved, due to the human perception of the robot (and vice versa), and other objective metrics related to fault detection and isolation, the discussion in this paper will focus on the peculiar aspects of "physical" interaction with robots. In particular, safety and dependability will be the underlying evaluation criteria for mechanical design, actuation, and control architectures. Mechanical and control issues will be discussed with emphasis on techniques that provide safety in an intrinsic way or by means of control components. Attention will be devoted to dependability, mainly related to sensors, control architectures, and fault handling and tolerance. After PHRIDOM, a novel research project has been launched under the Information Society Technologies Sixth Framework Programme of the European Commission. This "Specific Targeted Research or Innovation" project is dedicated to "Physical Human-Robot Interaction: depENDability and Safety" (PHRIENDS). PHRIENDS is about developing key components of the next generation of robots, including industrial robots and assist devices, designed to share the environment and to physically interact with people. The philosophy of the project proposes an integrated approach to the co-design of robots for safe physical interaction with humans, which revolutionizes the classical approach for designing industrial robots – rigid design for accuracy, active control for safety – by creating a new paradigm: design robots that are intrinsically safe, and control them to deliver performance. This paper presents the state of the art in the field as surveyed by the PHRIDOM project, as well as it enlightens a number of challenges that will be undertaken within the PHRIENDS project.
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paper_title: Towards a personal robotics development platform: Rationale and design of an intrinsically safe personal robot

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The most critical challenge for Personal Robotics is to manage the issue of human safety and yet provide the physical capability to perform useful work. This paper describes a novel concept for a mobile, 2-armed, 25-degree-of- freedom system with backdrivable joints, low mechanical impedance, and a 5 kg payload per arm. System identification, design safety calculations and performance evaluation studies of the first prototype are included, as well as plans for a future development.
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paper_title: Strategy on Safety Function Implementation : Case Study Involving Risk Assessment and Functional Safety Analysis for a Power Assist System

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Power assist systems are expected to bring many benefits in various fields, and some of them have already been introduced in the welfare and manufacturing industries. As power assist systems demand manual contact with a human operator, it is important to prevent hazards that originate from system faults. The objectives of this paper are to introduce a strategy on safety function implementation by means of a case study for a power assist system and to propose an approach for safety function design. This paper describes details of the strategy for Skill-Assist — the power assist system adopted as the experimental platform. First, the safety integrity level (SIL) required for Skill-Assist was determined, following which top-down and bottom-up risk assessments were conducted. A safety-related system (SRS) with a fail-safe fault detection device and dual-channel voting architecture was then constructed based on the risk assessment result. A functional safety analysis was performed for the SRS and we found that...
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paper_title: Mechanical system of a small biped entertainment robot

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SDR-4X is the latest prototype model, which is a small humanoid type robot. We reported the outline of this robot last year. In this paper we discuss more about mechanical system, which is important and original for a small biped entertainment robot, which will be used, in home environment. One technology is the design of actuators alignment in the body, which enables dynamic motion performance. Another technology is the actuator technology, which we originally developed, named intelligent servo actuator (ISA). We explain the specification and the important technical points. Next technology is the sensor system, which supports the high performance of the robot, especially the detection of outside objects, ability of stable walking motion and safe interaction with human. The robot is used in normal home environment, so we should strongly consider the falling-over of the robot. We propose the ideas against falling-over which makes the robot as safe as possible.
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paper_title: Safe robot arm with safe joint mechanism using nonlinear spring system for collision safety

paper_content:

Collision safety between humans and robots has drawn much attention since service robots are increasingly being used in human environments. A safe robot arm based on passive compliance can usually provide faster and more reliable responses for dynamic collision than an active one involving sensors and actuators. Since both positioning accuracy and collision safety of the robot arm are equally important, a robot arm should have very low stiffness when subjected to a collision force greater than the injury tolerance, but should otherwise maintain very high stiffness. To implement these requirements, a novel safe joint mechanism (SJM-II) which has much smaller size and lighter weight than the previous model, is proposed in this research. The SJM-II has the advantage of nonlinear spring which is achieved using only passive mechanical elements such as linear springs and a double-slider mechanism. Various analyses and experiments on static and dynamic collisions show that stiffness of the SJM-II is kept very high against an external torque less than the predetermined threshold torque, but abruptly drops when the input torque exceeds this threshold, thereby guaranteeing positioning accuracy and collision safety. Furthermore, a robot arm with two SJM-IIs is verified to achieve collision safety in 2D space.
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paper_title: A truly safely moving robot has to know what injury it may cause

paper_content:

Enabling robots to safely interact with humans is an essential goal of robotics research. The developments achieved over the last years in mechanical design and control made it possible to have active cooperation between humans and robots in rather complex situations. In these terms, safe behavior of the robot even under worst-case situations is crucial and forms also a basis for higher level decisional aspects. In order to quantify what safe behavior really means, the definition of injury, as well as understanding its general dynamics are essential. This insight can then be applied to design and control robots such that injury due to robot-human impacts is explicitly taken into account. In this paper we approach the problem from a medical injury analysis point of view in order to formulate the relation between robot mass, velocity, impact geometry, and resulting injury qualified in medical terms. We transform these insights into processable representations and propose a motion supervisor that utilizes injury knowledge for generating safe robot motions. The algorithm takes into account the reflected inertia, velocity, and geometry at possible impact locations. The proposed framework forms a basis for generating truly safe velocity bounds that explicitely consider the dynamic properties of the manipulator and human injury.
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paper_title: Playing it safe

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Play has physical, social, emotional and cognitive benefits for children.1 It has been suggested that opportunity for spontaneous play may be all that is needed to increase young children’s levels of physical activity,2 an appealing concept in view of our …
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paper_title: How Safe the Human-Robot Coexistence Is? Theoretical Presentation

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It is evident that industrial robots are able to generate forces high enough to injure a human. To prevent this, robots have to work within a restricted space that includes the entire region reachable by any part of the robot. However, more and more robot applications require human intervention due to superior abilities for some tasks performance. In this paper we introduce danger/safety indices which indicate a level of the risk during interaction with robots, which are based on a robot's critical characteristics and on a human's physical and mental constrains. Collision model for a 1 DOF robot and "human" was developed. Case study with further simulations was provided for the PUMA 560 robot.
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paper_title: Safety Analysis for a Human-Friendly Manipulator

paper_content:

The DLR Lightweight Robot III (LWR-III) developed at the German Aerospace Center (DLR) is characterized by low inertial properties, torque sensing in each joint, and a load to weight ratio similar to humans. These properties qualify it for applications requiring high mobility and direct interaction with human users or uncertain environments. An essential requirement for such a robot is that it must under no circumstances pose a threat to the human operator. To actually quantify the potential injury risk emanating from the manipulator, impact test were carried out using standard automobile crash-test facilities at the ADAC (German automobile club). Furthermore, we introduce our analysis for soft-tissue injury based on swine experiments with the LWR-III. This paper gives an overview about the variety of investigations necessary to provide a safety analysis of a human-friendly robot based on biomechanical injury results. We believe this paper can provide a guideline for the robotics community for future qualifications of other robots and thus serve as a key component to bring robots in our everyday life.
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paper_title: Design and Control of a Bio-inspired Human-Friendly Robot

paper_content:

A hermetic refrigeration compressor has a flat valve plate closing off a cylinder bore. The valve plate has an elongated recess on the outer side around the discharge port and a discharge valve assembly, comprising a flat reed valve and backing spring, fits within the recess beneath an overlying valve stop which engages the bottom of the recess at each end. The recess, the reed valve, the backing spring, and the valve stop are so configured that they can be assembled only in the correct configuration. The valve stop is held in place by an arcuate retaining spring having ends engaging notches in the valve plate and a projecting boss on a cylinder head defining a discharge valve plenum engages the retaining spring to press the spring and the valve plate into position within the recess to retain all of the parts in operating position.
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paper_title: A hybrid actuation approach for human-friendly robot design

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Safety is a critical characteristic for robots designed to operate in human environments. This paper presents the concept of hybrid actuation for the development of human- friendly robotic systems. The new design employs inherently safe pneumatic artificial muscles augmented with small electrical actuators, human-bone-inspired robotic links, and newly designed distributed compact pressure regulators. The modularization and integration of the robot components enable low complexity in the design and assembly. The hybrid actuation concept has been validated on a two-degree-of-freedom prototype arm. The experimental results show the significant improvement that can be achieved with hybrid actuation over an actuation system with pneumatic artificial muscles alone. Using the manipulator safety index (MSI), the paper discusses the safety of the new prototype and shows the robot arm safety characteristics to be comparable to those of a human arm.
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paper_title: Collision analysis and evaluation of collision safety for service robots working in human environments

paper_content:

Collision safety between humans and robots has drawn much attention because service robots are increasingly being used in human environments. The design of a service robot usually requires reliable collision analysis based on appropriate safety criterion. Previous safety criteria are too restrictive or generous with respect to collision injury. This paper proposes a new safety criterion for physical human-robot interaction. Injury tolerance related to the fracture force of the thyroid and cricoid cartilage in the neck is more suitable to measure injury to humans from robots than criteria representing serious injury in car crash tests. To accurately evaluate robot collision safety, a novel collision model between a human and a robot is established which include the stiffness of the neck and covering, and the input torque of the robot. The injury criteria suggested in this paper were verified to estimate the safety of service robots. Various collision analyses based on this criterion are conducted, and thus the design parameters of robot arms can be adjusted to enhance safety.
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paper_title: Safety Analysis for a Human-Friendly Manipulator

paper_content:

The DLR Lightweight Robot III (LWR-III) developed at the German Aerospace Center (DLR) is characterized by low inertial properties, torque sensing in each joint, and a load to weight ratio similar to humans. These properties qualify it for applications requiring high mobility and direct interaction with human users or uncertain environments. An essential requirement for such a robot is that it must under no circumstances pose a threat to the human operator. To actually quantify the potential injury risk emanating from the manipulator, impact test were carried out using standard automobile crash-test facilities at the ADAC (German automobile club). Furthermore, we introduce our analysis for soft-tissue injury based on swine experiments with the LWR-III. This paper gives an overview about the variety of investigations necessary to provide a safety analysis of a human-friendly robot based on biomechanical injury results. We believe this paper can provide a guideline for the robotics community for future qualifications of other robots and thus serve as a key component to bring robots in our everyday life.
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paper_title: Safety Evaluation Method of Design and Control for Human-Care Robots

paper_content:

We propose the world's first general method of evaluating safety for human-care robots. In the case of a careless collision between a robot and a human, impact force and impact stress are chosen as evaluation measures, and a danger-index is defined to quantitatively evaluate the effectiveness of each safety strategy used for design and control. As a result, this proposed method allows us to assess the contribution of each safety strategy to the overall safety performance of a human-care robot. In addition, a new type of three-dimensional robot simulation system for danger evaluation is constructed on a PC. The system simplifies the danger evaluation of both the design and control of various types of human-care robots to quantify the effectiveness of various safety strategies.
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paper_title: Quantitative Safety Guarantees for Physical Human-Robot Interaction

paper_content:

If robots are to be introduced into the human world as assistants to aid a person in the completion of a manual task two key problems of today's robots must be solved. The human-robot interface must be intuitive to use and the safety of the user with respect to injuries inflicted by collisions with the robot must be guaranteed. In this paper we describe the formulation and implementation of a control strategy for robot manipulators which provides quantitative safety guarantees for the user of assistant-type robots. We propose a control scheme for robot manipulators that restricts the torque commands of a position control algorithm to values that comply to preset safety restrictions. These safety restrictions limit the potential impact force of the robot in the case of a collision with a person. Such accidental collisions may occur with any part of the robot and therefore the impact force not only of the robot's hand but of all surfaces is controlled by the scheme. The integration of a visual control inter...
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paper_title: Infant Skull and Suture Properties: Measurements and Implications for Mechanisms of Pediatric Brain Injury

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The mechanical properties of the adult human skull are well documented, but little information is available for the infant skull. To determine the age-dependent changes in skull properties, we tested human and porcine infant cranial bone in three-point bending. The measurement of elastic modulus in the human and porcine infant cranial bone agrees with and extends previous published data [McPherson, G. K., and Kriewall, T. J. (1980), J. Biomech., 13, pp. 9‐16] for human infant cranial bone. After confirming that the porcine and human cranial bone properties were comparable, additional tensile and three-point bending studies were conducted on porcine cranial bone and suture. Comparisons of the porcine infant data with previously published adult human data demonstrate that the elastic modulus, ultimate stress, and energy absorbed to failure increase, and the ultimate strain decreases with age for cranial bone. Likewise, we conclude that the elastic modulus, ultimate stress, and energy absorbed to failure increase with age for sutures. We constructed two finite element models of an idealized one-month old infant head, one with pediatric and the other adult skull properties, and subjected them to impact loading to investigate the contribution of the cranial bone properties on the intracranial tissue deformation pattern. The computational simulations demonstrate that the comparatively compliant skull and membranous suture properties of the infant brain case are associated with large cranial shape changes, and a more diffuse pattern of brain distortion than when the skull takes on adult properties. These studies are a fundamental initial step in predicting the unique mechanical response of the pediatric skull to traumatic loads associated with head injury and, thus, for defining head injury thresholds for children. @S0148-0731~00!00904-3#
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paper_title: Systems safety for robots: An energy barrier analysis

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Abstract Rahimi, M., 1986. Systems safety for robots: An energy barrier analysis. Journal of Occupational Accidents , 8: 127–138. The need for a comprehensive study of hazards caused by robot work environments is stressed. Based on previous data and robot accident reports, major factors contributing to robot accidents are classified and listed. System safety is introduced as an appropriate approach to analyze safety of semiautomated and automated robot systems. A general procedure for conducting system safety analysis is presented. Energy Barrier Analysis (EBA), a qualitative system safety technique, is applied to a general model of human—robot system. Major concepts of EBA are integrated in a stepwise approach for evaluating and designing robot safety systems. As the result of this application, specific solutions and recommendations are discussed.
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paper_title: A Proposed New Biomechanical Head Injury Assessment Function - the Maximum Power Index

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Recently, several cases of mild traumatic brain injury (MTBI) to American professional football players have been reconstructed using instrumented Hybrid III anthropomorphic test dummies (ATDs). The translational and rotational acceleration responses of injured and uninjured players' heads have been documented. The acceleration data have been processed according to all current head injury assessment functions including the Gadd Severity Index (GSI), Head Injury Criterion (HIC) and GAMBIT among others. In this study, a new hypothesis is propounded that the threshold for head injury will be exceeded if the rate of change of kinetic energy of the head exceeds some limiting value. A functional relation is proposed, which includes all six degrees of motion and directional sensitivity characteristics, relating the rate of change of kinetic energy to the probability of head injury. The maximum value that the function achieves during impact is the maximum power input to the head and serves as an index by which the probability of head injury can be assessed. (A) For the covering abstract of the conference see ITRD E203843.
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paper_title: Rescue robotics - a crucial milestone on the road to autonomous systems

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Rescue robotics is an important steppingstone in the scientific challenge to create autonomous systems. There is a significant market for rescue robots, which have unique features that allow a fruitful combination of application-oriented developments and basic research. Unlike other markets for advanced robotics systems like service robots, the rescue robotics domain benefits from the fact that there is a human in the loop, which allows a stepwise transition from dumb teleoperated devices to truly autonomous systems. Current teleoperated devices are already very useful in this domain and they benefit from any bit of autonomy added. Human rescue workers are a scarce resource at disaster scenarios. A single operator should, hence, ideally supervise a multitude of robots. We present results from the rescue robots at the International University Bremen in a core area supporting autonomy, i.e., mapping.
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paper_title: Human head-neck biomechanics under axial tension.

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A significant majority of cervical spine biomechanics studies has applied the external loading in the form of compressive force vectors. In contrast, there is a paucity of data on the tensile loading of the neck structure. These data are important as the human neck not only resists compression but also has to withstand distraction due to factors such as the anatomical characteristics and loading asymmetry. Furthermore, evidence exists implicating tensile stresses to be a mechanism of cervical spinal cord injury. Recent advancements in vehicular restraint systems such as air bags may induce tension to the neck in adverse circumstances. Consequently, this study was designed to develop experimental methodologies to determine the biomechanics of the human cervical spinal structures under distractive forces. A part-to-whole approach was used in the study. Four experimental models from 15 unembalmed human cadavers were used to demonstrate the feasibility of the methodology. Structures included isolated cervical spinal cords, intervertebral disc units, skull to T3 preparations, and intact unembalmed human cadavers. Axial tensile forces were applied, and the failure load and distraction were recorded. Stiffness and energy absorbing characteristics were computed. Maximum forces for the spinal cord specimens were the lowest (278 N +/- 90). The forces increased for the intervertebral disc (569 N +/- 54). skull to T3 (1555 N +/- 459), and intact human cadaver (3373 N +/- 464) preparations, indicating the load-carrying capacities when additional components are included to the experimental model. The experimental methodologies outlined in the present study provide a basis for further investigation into the mechanism of injury and the clinical applicability of biomechanical parameters.
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paper_title: A failure-to-safety "Kyozon" system with simple contact detection and stop capabilities for safe human-autonomous robot coexistence

paper_content:

In this paper, we discuss a method to achieve safe autonomous robot system coexistence (or Kyozon in Japanese). First, we clarify human pain tolerance and point out that a robot working next to an operator should be covered with a soft material. Thus, we propose a concept and a design method of covering a robot with a viscoelastic material to achieve both impact force attenuation and contact sensitivity, keeping within the human pain tolerance limit. We stress the necessity of a simple robot system from the viewpoint of reliability. We provide a method of sensing contact force without any force sensors by monitoring the direct drive motor current and velocity of the robot. Finally, we covered a two-link arm manipulator with the optimum soft covering material, and applied the developed manipulator system to practical coexistence tasks.
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paper_title: Towards a novel safety norm for domestic robotics

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Safety is a critical success factor for consumer acceptance of domestic robotic products. Some researchers have adopted the head injury criterion (HIC) as absolute safety norm. However, this norm covers only part of the safety risk. In many cases skin damage (e.g. cuts, wounds, etc) can be a more serious risk. This article shows how to work towards a novel absolute safety measure for evaluating the shape and material choices of a robotic design w.r.t. skin damage. The proposed safety norm evaluates the situation of an unintended uncontrolled collision of a robotic part against a human. Maximum curvatures of the exterior robotic shape are approximated as a sphere in contact with the human skin (locally approximated as a flat surface). This local spheric approximation of the impact contact is used to predict maximum tensile stress during impact of the robotic part on the human. Robotic designs that include points for which the tensile strength of the skin is exceeded will cause at least skin fracture and are therefore considered intrinsically unsafe. While in general applicable, this paper specifically addresses how to apply the proposed norm in the case of safety evaluation of robotic manipulators.
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paper_title: On making robots understand safety: Embedding injury knowledge into control

paper_content:

Enabling robots to safely interact with humans is an essential goal of robotics research. The developments achieved over recent years in mechanical design and control made it possible to have active cooperation between humans and robots in rather complex situations. For this, safe robot behavior even under worst-case situations is crucial and forms also a basis for higher-level decisional aspects. For quantifying what safe behavior really means, the definition of injury, as well as understanding its general dynamics, are essential. This insight can then be applied to design and control robots such that injury due to robot-human impacts is explicitly taken into account. In this paper we approach the problem from a medical injury analysis point of view in order to formulate the relation between robot mass, velocity, impact geometry and resulting injury qualified in medical terms. We transform these insights into processable representations and propose a motion supervisor that utilizes injury knowledge for generating safe robot motions. The algorithm takes into account the reflected inertia, velocity, and geometry at possible impact locations. The proposed framework forms a basis for generating truly safe velocity bounds that explicitly consider the dynamic properties of the manipulator and human injury.
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paper_title: Industrial robot and human operator collision

paper_content:

Our work is focused on cooperation of a small industrial robot and human operator where collision is expected only between the robot end-effector and the lower arm of the human worker. To study the effect of the impact between the robot and man, a passive mechanical lower arm (PMLA) was developed. The investigation presented in this paper evaluates whether the PMLA is a sufficiently accurate emulation system of a passive human lower arm. The same experiments were performed with the PMLA and with human volunteers. The results of both investigations were compared and evaluated to determine whether the PMLA can competently replace human volunteers in dangerous future investigations.
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paper_title: Designing optimally safe robot surface properties for minimizing the stress characteristics of human-robot collisions

paper_content:

Modeling of low severity soft-tissue injury due to unwanted collisions of a robot in collaborative settings is an important aspect to be treated in safe physical Human-Robot Interaction (pHRI). Up to now, safety evaluations for pHRI were mainly conducted by using safety criteria related with impact forces and head accelerations. These indicate severe injury in the robotics context and leave out low severity injury such as contusions and lacerations. However, for the design of an intrinsically safer robot arm, a reliable evaluation of the collision between a human and a robot that is based on skin injury criteria is essential. In this paper, we propose a novel human-robot collision model with and without covering, which is based on the impact stress distribution. The reliability of the proposed collision model is verified by a comparison with various cadaver experiments taken from existing biomechanical literature. Since the stress characteristics acting on the human head can be analyzed with this new collision model, the occurrence of certain soft-tissue injury can be estimated. Furthermore, the method serves for selecting the appropriate covering parameters, as e.g. elastic modulus and thickness, by evaluating the chosen skin injury indices.
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paper_title: A failure-to-safety "Kyozon" system with simple contact detection and stop capabilities for safe human-autonomous robot coexistence

paper_content:

In this paper, we discuss a method to achieve safe autonomous robot system coexistence (or Kyozon in Japanese). First, we clarify human pain tolerance and point out that a robot working next to an operator should be covered with a soft material. Thus, we propose a concept and a design method of covering a robot with a viscoelastic material to achieve both impact force attenuation and contact sensitivity, keeping within the human pain tolerance limit. We stress the necessity of a simple robot system from the viewpoint of reliability. We provide a method of sensing contact force without any force sensors by monitoring the direct drive motor current and velocity of the robot. Finally, we covered a two-link arm manipulator with the optimum soft covering material, and applied the developed manipulator system to practical coexistence tasks.
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paper_title: Implementation of variable joint stiffness through antagonistic actuation using rolamite springs

paper_content:

Abstract The addition of variable joint stiffness to an upper limb prosthesis can restore an important function of the natural arm. Design goals for the stiffness and force performance of prosthetic elbow joints are presented. This paper develops configurations of antagonistic actuators, for use in prosthetic arms, with improved energy efficiency, controllability, interaction properties, and size. Implementation of the required quadratic stiffness elements is investigated using rolamites. The rolamite band geometry is designed to generate the required force function. Rolamite design equations are extended to include effects of high force generation and stress concentrations. The effect of using rolamites to generate the spring forces is examined with respect to restrictions placed on the performance of the joint. The performance of this approach to the implementation of a variable stiffness joint is found to be marginally useful in a prosthetic application. Further design improvements are suggested.
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paper_title: Feedforward/Feedback Laws for the Control of Flexible Robots

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We present a survey of the nominal motion generation schemes and of the associated simple control solutions for robots displaying flexibility effects. Two model classes are considered: robots with elastic joints but rigid links, and robots with flexible links. Model-based feedforward laws are derived for the two basic motion tasks of state-to-state transfer in given time and exact trajectory execution. In particular, we present a new solution to the finite-time reconfiguration problem for a one-link flexible arm. Finally, we use the developed commands into a simple feedback scheme that requires only standard sensors on the motors.
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paper_title: The DLR hand arm system

paper_content:

An anthropomorphic hand arm system using variable stiffness actuation has been developed at DLR. It is aimed to reach its human archetype regarding size, weight and performance. The main focus of our development is put on robustness, dynamic performance and dexterity. Therefore, a paradigm change from impedance controlled, but mechanically stiff joints to robots using intrinsic variable compliance joints is carried out.
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paper_title: Mechanical Design for Whole-Arm Manipulation

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This paper describes the performance requirements and mechanical design of an arm designed and built at MIT for whole-arm manipulation. Whole-arm manipulation began as a research objective to explore the benefits of manipulating objects with all surfaces of a robotic manipulator — not just the fingertips of an attached robotic hand. The need for robust environment contact by all surfaces of the robotic hardware prompted a re-evaluation of traditional manipulator design requirements and spurred the invention of new transmission mechanisms for robots.
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paper_title: Integration of active and passive compliance control for safe human-robot coexistence

paper_content:

In this paper we discuss the integration of active and passive approaches to robotic safety in an overall scheme for real-time manipulator control. The active control approach is based on the use of a supervisory visual system, which detects the presence and position of humans in the vicinity of the robot arm, and generates motion references. The passive control approach uses variable joint impedance which combines with velocity control to guarantee safety in worst-case conditions, i.e. unforeseen impacts. The implementation of these techniques in a 3-dof, variable impedance arm is described, and the effectiveness of their functional integration is demonstrated through experiments.
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paper_title: New insights concerning intrinsic joint elasticity for safety

paper_content:

In this paper we present various new insights on the effect intrinsic joint elasticity has on safety in pHRI. We address the fact that the intrinsic safety of elastic mechanisms has been discussed rather one sided in favor of this new designs and intend to give a more differentiated view on the problem. An important result is that intrinsic joint elasticity does not reduce the Head Injury Criterion or impact forces compared to conventional actuation with some considerable elastic behavior in the joint, if considering full scale robots. We also elaborate conditions under which intrinsically compliant actuation is potentially more dangerous than rigid one. Furthermore, we present collision detection and reaction schemes for such mechanisms and verify their effectiveness experimentally.
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paper_title: Safe robot arm with safe joint mechanism using nonlinear spring system for collision safety

paper_content:

Collision safety between humans and robots has drawn much attention since service robots are increasingly being used in human environments. A safe robot arm based on passive compliance can usually provide faster and more reliable responses for dynamic collision than an active one involving sensors and actuators. Since both positioning accuracy and collision safety of the robot arm are equally important, a robot arm should have very low stiffness when subjected to a collision force greater than the injury tolerance, but should otherwise maintain very high stiffness. To implement these requirements, a novel safe joint mechanism (SJM-II) which has much smaller size and lighter weight than the previous model, is proposed in this research. The SJM-II has the advantage of nonlinear spring which is achieved using only passive mechanical elements such as linear springs and a double-slider mechanism. Various analyses and experiments on static and dynamic collisions show that stiffness of the SJM-II is kept very high against an external torque less than the predetermined threshold torque, but abruptly drops when the input torque exceeds this threshold, thereby guaranteeing positioning accuracy and collision safety. Furthermore, a robot arm with two SJM-IIs is verified to achieve collision safety in 2D space.
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paper_title: Passive mechanical gravity compensation for robot manipulators

paper_content:

A simple mechanical method for passively compensating for gravitationally induced joint torques is presented. This energy-conservative gravity-compensation method is suitable for a variety of manipulator designs. With cables and appropriate pulley profiles, changes in potential energy associated with link motion through a gravity field can be mapped to changes in strain energy storage in spring elements. The resulting system requires significant energy input only for acceleration and deceleration or to resist external forces. A testbed with both single- and double-link configurations has demonstrated the efficiency and accuracy of this gravity compensation method, as well as its robustness under dynamic loading conditions. >
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paper_title: Active stiffness control of a manipulator in cartesian coordinates

paper_content:

A method of actively controlling the apparent stiffness of a manipulator end effecter is presented. The approach allows the programmer to specify the three transnational and three rotational stiffness of a frame located arbitrarily in hand coordinates. Control of the nominal position of the hand then permits simultaneous position and force control. Stiffness may be changed under program control to match varying task requirements. A rapid servo algorithm is made possible by transformation of the problem into joint space at run time. Applications examples are given.
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paper_title: A new actuation approach for human friendly robot design

paper_content:

Many successful robotic manipulator designs have been introduced. However, there remains the challenge of designing a manipulator that possesses the inherent safety characteristics necessary for human-centered robotics. In this paper, we present a new actuation approach that has the requisite characteristics for inherent safety while maintaining the performance expected of modern designs. By drastically reducing the effective impedance of the manipulator while maintaining high frequency torque capability, we show that the competing design requirements of performance and safety can be successfully integrated into a single manipulation system.
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paper_title: The DLR lightweight robot: design and control concepts for robots in human environments

paper_content:

Purpose – The paper seeks to present a new generation of torque‐controlled light‐weight robots (LWR) developed at the Institute of Robotics and Mechatronics of the German Aerospace Center.Design/methodology/approach – An integrated mechatronic design approach for LWR is presented. Owing to the partially unknown properties of the environment, robustness of planning and control with respect to environmental variations is crucial. Robustness is achieved in this context through sensor redundancy and passivity‐based control. In the DLR root concept, joint torque sensing plays a central role.Findings – In order to act in unstructured environments and interact with humans, the robots have design features and control/software functionalities which distinguish them from classical robots, such as: load‐to‐weight ratio of 1:1, torque sensing in the joints, active vibration damping, sensitive collision detection, compliant control on joint and Cartesian level.Practical implications – The DLR robots are excellent rese...
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paper_title: A Robot Actuator Development With High Backdrivability

paper_content:

We propose a new robot actuator, especially a robot actuator gear which has a very effective feature of backdrivability. We show the study of the new definition of backdrivability of an actuator gear which has the quantitative definition. From this definition we propose the method of making the gear which has a good backdrivability. Based on this method, the actuator gear was developed and we show the result from the experiment. The comparisons with the other types of actuator gear which are Harmonic drive gear and normal planetary gear are described. Finally the comparison has proved that the developed actuator gear has very effective backdrivability.
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paper_title: Design and Control of a Bio-inspired Human-Friendly Robot

paper_content:

A hermetic refrigeration compressor has a flat valve plate closing off a cylinder bore. The valve plate has an elongated recess on the outer side around the discharge port and a discharge valve assembly, comprising a flat reed valve and backing spring, fits within the recess beneath an overlying valve stop which engages the bottom of the recess at each end. The recess, the reed valve, the backing spring, and the valve stop are so configured that they can be assembled only in the correct configuration. The valve stop is held in place by an arcuate retaining spring having ends engaging notches in the valve plate and a projecting boss on a cylinder head defining a discharge valve plenum engages the retaining spring to press the spring and the valve plate into position within the recess to retain all of the parts in operating position.
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paper_title: 3-DOF Cartesian Force Limiting Device Based on the Delta architecture for safe physical human-robot interaction

paper_content:

This paper presents a device that significantly improves the safety of ceiling-mounted robots whose end effector orientation remains constant with respect to the vertical direction (e.g. Scara-type robots). The device consists of a three-degree-of-freedom (DOF) parallel mechanism with the Delta architecture on which the revolute actuators have been replaced with torque limiters. The resulting Cartesian force limiting device (CFLD) is implemented as a mechanical connection between the robot and the effector. It is rigid unless excessive forces are applied on the end effector, for example during a collision. The magnitude of force that activates the mechanism is set by properly adjusting the threshold of the torque limiters. Furthermore, a collision can be rapidly detected with a limit switch placed on one of the links of the mechanism and a signal can be sent directly to brakes that will stop the robot, without passing through a controller and thus improving the reliability and reaction-time of the safety system. By mechanically disconnecting the robot from its end effector, the device ensures that the person involved in the collision is only subjected to the inertia of the end effector and thus potential injuries are greatly reduced. This work is the extension of a previous 2-DOF CFLD that was sensitive only to horizontal forces. The new architecture reacts to collisions occuring in any direction and is geometrically optimized for the proposed application.
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paper_title: Passive compliance versus active compliance in robot‐based automated assembly systems

paper_content:

Industrial robots have found great potential in applications to assembly‐line automation. Programmable robot‐based assembly systems are often needed, in particular for circumstances in which special assembly equipments is not available or well‐trained operators could not be employed economically. Robots with enough compliance can perform not only classic automation tasks, such as spot welding, cargo carrying, etc., but also can operate those tasks which demand the compliant motion capacity of robots. Therefore, the research on robot compliance is especially important for parts assembly by robots, where robot compliant motions and manipulations are essential requirements. This paper presents a number of important issues in robot compliance research, including the specification of robot end‐effector compliance; properties of a robot compliance matrix at its end‐effector; discussions on passive compliance and active compliance and their comparisons; and derivation of the compliance at the end‐effector required for tasks.
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paper_title: A new variable stiffness design: Matching requirements of the next robot generation

paper_content:

Facing new tasks, the conventional rigid design of robotic joints has come to its limits. Operating in unknown environments current robots are prone to failure when hitting unforeseen rigid obstacles. Moreover, safety constraints are a major aspect for robots interacting with humans. In order to operate safely, existing robotic systems in this field are slow and have a lack of performance. To circumvent these limitations, a new robot joint with a variable stiffness approach (VS-Joint) is presented. It combines a compact and highly integrated design with high performance actuation. The VS- Joint features a highly dynamic stiffness adjustment along with a mechanically programmable system behavior. This allows an easy adaption to a big variety of tasks. A benefit of the joint is its intrinsic robustness against impacts and hard contacts, which permits faster trajectories and handling. Thus, it provides excellent attributes for the use in shoulder and elbow joints of an anthropomorphic robot arm.
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paper_title: A hybrid actuation approach for human-friendly robot design

paper_content:

Safety is a critical characteristic for robots designed to operate in human environments. This paper presents the concept of hybrid actuation for the development of human- friendly robotic systems. The new design employs inherently safe pneumatic artificial muscles augmented with small electrical actuators, human-bone-inspired robotic links, and newly designed distributed compact pressure regulators. The modularization and integration of the robot components enable low complexity in the design and assembly. The hybrid actuation concept has been validated on a two-degree-of-freedom prototype arm. The experimental results show the significant improvement that can be achieved with hybrid actuation over an actuation system with pneumatic artificial muscles alone. Using the manipulator safety index (MSI), the paper discusses the safety of the new prototype and shows the robot arm safety characteristics to be comparable to those of a human arm.
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paper_title: On impact decoupling properties of elastic robots and time optimal velocity maximization on joint level

paper_content:

Designing intrinsically elastic robot systems, making systematic use of their properties in terms of impact decoupling, and exploiting temporary energy storage and release during excitative motions is becoming an important topic in nowadays robot design and control. In this paper we treat two distinct questions that are of primary interest in this context. First, we elaborate an accurate estimation of the maximum contact force during simplified human/obstacle-robot collisions and how the relation between reflected joint stiffness, link inertia, human/obstacle stiffness, and human/obstacle inertia affect it. Overall, our analysis provides a safety oriented methodology for designing intrinsically elastic joints and clearly defines how its basic mechanical properties influence the overall collision behavior. This can be used for designing safer and more robust robots. Secondly, we provide a closed form solution of reaching maximum link side velocity in minimum time with an intrinsically elastic joint, while keeping the maximum deflection constraint. This gives an analytical tool for determining suitable stiffness and maximum deflection values in order to be able to execute desired optimal excitation trajectories for explosive motions.
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paper_title: Towards a personal robotics development platform: Rationale and design of an intrinsically safe personal robot

paper_content:

The most critical challenge for Personal Robotics is to manage the issue of human safety and yet provide the physical capability to perform useful work. This paper describes a novel concept for a mobile, 2-armed, 25-degree-of- freedom system with backdrivable joints, low mechanical impedance, and a 5 kg payload per arm. System identification, design safety calculations and performance evaluation studies of the first prototype are included, as well as plans for a future development.
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paper_title: Human-like Compliance for Dexterous Robot Hands

paper_content:

This paper describes the Active Electromechanical Compliance (AEC) system that was developed for the Jau-JPL anthropomorphic robot. The AEC system imitates the functionality of the human muscle's secondary function, which is to control the joint's stiffness: AEC is implemented through servo controlling the joint drive train's stiffness. The control strategy, controlling compliant joints in teleoperation, is described. It enables automatic hybrid position and force control through utilizing sensory feedback from joint and compliance sensors. This compliant control strategy is adaptable for autonomous robot control as well. Active compliance enables dual arm manipulations, human-like soft grasping by the robot hand, and opens the way to many new robotics applications.
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paper_title: On a new generation of torque controlled light-weight robots

paper_content:

The paper describes the recent design and development efforts in DLR Robotics Lab towards the second generation of light-weight robots. The design of the light weight mechanics, integrated sensors and electronics is outlined. The fully sensory joint, with motor and link position sensors as well as joint torque sensors enables the implementation of effective vibration damping and advanced control strategies for compliant manipulation. The mechatronic approach incorporates a tight collaboration between mechanics, electronics and controller design. The authors hope that important steps towards a new generation of service and personal robots have been achieved.
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paper_title: Series elastic actuators

paper_content:

It is traditional to make the interface between an actuator and its load as stiff as possible. Despite this tradition, reducing interface stiffness offers a number of advantages, including greater shock tolerance, lower reflected inertia, more accurate and stable force control, less inadvertent damage to the environment, and the capacity for energy storage. As a trade-off, reducing interface stiffness also lowers zero motion force bandwidth. In this paper, the authors propose that for natural tasks, zero motion force bandwidth isn't everything, and incorporating series elasticity as a purposeful element within the actuator is a good idea. The authors use the term elasticity instead of compliance to indicate the presence of a passive mechanical spring in the actuator. After a discussion of the trade-offs inherent in series elastic actuators, the authors present a control system for their use under general force or impedance control. The authors conclude with test results from a revolute series-elastic actuator meant for the arms of the MIT humanoid robot Cog and for a small planetary rover.
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paper_title: Design and Control of a Variable Stiffness Actuator for Safe and Fast Physical Human/Robot Interaction

paper_content:

This paper is concerned with the design and control of actuators for machines and robots physically interacting with humans, implementing criteria established in our previous work [1] on optimal mechanical-control co-design for intrinsically safe, yet performant machines. In our Variable Impedance Actuation (VIA) approach, actuators control in real-time both the reference position and the mechanical impedance of the moving parts in the machine in such a way to optimize performance while intrinsically guaranteeing safety. In this paper we describe an implementation of such concepts, consisting of a novel electromechanical Variable Stiffness Actuation (VSA) motor. The design and the functioning principle of the VSA are reported, along with the analysis of its dynamic behavior. A novel scheme for feedback control of this device is presented, along with experimental results showing performance and safety of a one-link arm actuated by the VSA motor.
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paper_title: Human Safety Mechanisms of Human-Friendly Robots: Passive Viscoelastic Trunk and Passively Movable Base

paper_content:

We would like to give robots the ability to secure human safety in human-robot collisions capable of arising in our living and working environments. However, unfortunately, not much attention has been paid to the technologies of human robot symbiosis to date because almost all robots have been designed and constructed on the assumption that the robots are physically separated from humans. A robot with a new concept will be required to deal with human-robot contact. In this article, we propose a passively movable human-friendly robot that consists of an elastic material-covered manipulator, passive compliant trunk, and passively movable base. The compliant trunk is equipped with springs and dampers, and the passively movable base is constrained by friction developed between the contact surface of the base and the ground. During unexpected collisions, the trunk and base passively move in response to the produced collision force. We describe the validity of the movable base and compliant trunk for collision ...
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paper_title: Dynamic hybrid position/force control of robot manipulators--Description of hand constraints and calculation of joint driving force

paper_content:

For the application of robot manipulators to complex tasks, it is often necessary to control not only the position of a manipulator but also the force exerted by the hand on an object. For this purpose, Raibert and Craig have proposed the hybrid position/force control method. In this method, however, the manipulator dynamics has not been taken into account rigorously. The dynamic hybrid control method is proposed, which takes the manipulator dynamics into consideration. Constraints on the end effector are described by a set of constraint hypersurfaces. Then the basic equations for dynamic hybrid control are derived. It is shown that if the manipulator is not in a singular configuration, the desired position and force at the end effector can be simultaneously realized. Finally, a basic structure of the dynamic hybrid control system with a servo compensator is given.
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paper_title: Toward the implementation of hybrid position/force control in industrial robots

paper_content:

With the goal of filling the gap between theory and industrial applications, an implicit hybrid control scheme is proposed in this paper, designed to fit as much as possible the conventional industrial robot control architecture. The dynamic effects due to joint compliance, which are a major source of performance degradation in industrial robots, are fully taken into account. The scheme is based on a task description particularly suited for a direct integration in conventional robot programming tools and aims at exerting the force control action without affecting the trajectory tracking. Only the differential kinematic model (Jacobian) of the robot is needed in the design of the force control law, while the force control loop is charged with rejecting dynamic disturbances due to motion. A thorough experimental validation of the strategy, both in terms of force regulation and trajectory tracking capabilities, is discussed, based on experiments performed on an industrial robot, endowed with a six-axis wrist force/torque sensor and with a laser distance sensor.
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paper_title: On adaptive impedance control of robot manipulators

paper_content:

Impedance control specifications for robot manipulators are given in terms of a desired motion trajectory and a desired dynamic relationship between position errors and interaction forces. An adaptive implementation is proposed as an alternative to reduce the design sensitivity due to model-manipulator parameter mismatch. Two adaptive controllers that globally achieve the impedance objective for the general nonlinear dynamic model are presented. The controller structures consist of a nonlinear feedback of positions, velocities, and end-effector applied forces. Computer simulations were carried out to demonstrate stability and performance control. >
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paper_title: Collision Detection and Safe Reaction with the DLR-III Lightweight Manipulator Arm

paper_content:

A robot manipulator sharing its workspace with humans should be able to quickly detect collisions and safely react for limiting injuries due to physical contacts. In the absence of external sensing, relative motions between robot and human are not predictable and unexpected collisions may occur at any location along the robot arm. Based on physical quantities such as total energy and generalized momentum of the robot manipulator, we present an efficient collision detection method that uses only proprioceptive robot sensors and provides also directional information for a safe robot reaction after collision. The approach is first developed for rigid robot arms and then extended to the case of robots with elastic joints, proposing different reaction strategies. Experimental results on collisions with the DLR-III lightweight manipulator are reported.
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paper_title: Safe human robot interaction via energy regulation control

paper_content:

This paper presents an energy-based control strategy to be used in robotic systems working closely or cooperating with humans. The presented method bounds the dangerous behavior of the robot during the first instants of the impact by limiting the energy stored into the system to a maximum imposed value.Two critical physical human robot interaction (pHRI) cases are studied, these are the collision either against a free or a clamped head. Safe energy values that can be used as reference were retrieved by analysing experimental data of energy absorption to failure of cranium bones and cervical spinal cords.The energy regulation control is implemented in a series elastic actuator prototype joint. The model and the control scheme of the system are analysed. The proposed control scheme is a position-based controller that adjusts the position trajectory reference in function of the maximum energy value imposed by the user. Preliminary results are presented to show that the actuator unit and this control scheme are capable of limiting the energy to a maximum imposed value.
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paper_title: Passivity-based Object-Level Impedance Control for a Multifingered Hand

paper_content:

Holding an object and manipulating it in 6D is a key application for multifingered robot hands. In the past many algorithms were proposed based on a weighted pseudoinverse of the grasp map combined with an internal force control. The majority of these algorithms require robust contact detection/tracking and switching controllers. Employing the virtual object introduced by Stramigioli we present an object-level control law. We define a novel virtual object frame based on the robot hand configuration. Our control law takes a desired object frame and desired grasping forces as input, it is passive, has an intuitive physical meaning, and stability is even given in case a finger looses contact with the object. A damping design as a function of the desired object stiffness and the combined hand-object inertia is presented. The performance of the controller is proven in two experiments implemented on the DLR Hand II.
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paper_title: Interconnection and damping assignment passivity-based control of port-controlled Hamiltonian systems

paper_content:

Passivity-based control (PBC) is a well-established technique that has shown to be very powerful to design robust controllers for physical systems described by Euler-Lagrange (EL) equations of motion. For regulation problems of mechanical systems, which can be stabilized ''shaping'' only the potential energy, PBC preserves the EL structure and furthermore assigns a closed-loop energy function equal to the difference between the energy of the system and the energy supplied by the controller. Thus, we say that stabilization is achieved via energy balancing. Unfortunately, these nice properties of EL-PBC are lost when used in other applications which require shaping of the total energy, for instance, in electrical or electromechanical systems, or even some underactuated mechanical devices. Our main objective in this paper is to develop a new PBC theory which extends to a broader class of systems the aforementioned energy-balancing stabilization mechanism and the structure invariance. Towards this end, we depart from the EL description of the systems and consider instead port-controlled Hamiltonian models, which result from the network modelling of energy-conserving lumped-parameter physical systems with independent storage elements, and strictly contain the class of EL models.
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paper_title: Learning variable impedance control

paper_content:

One of the hallmarks of the performance, versatility, and robustness of biological motor control is the ability to adapt the impedance of the overall biomechanical system to different task requirements and stochastic disturbances. A transfer of this principle to robotics is desirable, for instance to enable robots to work robustly and safely in everyday human environments. It is, however, not trivial to derive variable impedance controllers for practical high degree-of-freedom (DOF) robotic tasks. In this contribution, we accomplish such variable impedance control with the reinforcement learning (RL) algorithm PI2 (Policy Improvement with Path Integrals). PI2 is a model-free, sampling-based learning method derived from first principles of stochastic optimal control. The PI 2 algorithm requires no tuning of algorithmic parameters besides the exploration noise. The designer can thus fully focus on the cost function design to specify the task. From the viewpoint of robotics, a particular useful property of PI2 is that it can scale to problems of many DOFs, so that reinforcement learning on real robotic systems becomes feasible. We sketch the PI2 algorithm and its theoretical properties, and how it is applied to gain scheduling for variable impedance control. We evaluate our approach by presenting results on several simulated and real robots. We consider tasks involving accurate tracking through via points, and manipulation tasks requiring physical contact with the environment. In these tasks, the optimal strategy requires both tuning of a reference trajectory and the impedance of the end-effector. The results show that we can use path integral based reinforcement learning not only for planning but also to derive variable gain feedback controllers in realistic scenarios. Thus, the power of variable impedance control is made available to a wide variety of robotic systems and practical applications.
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paper_title: The DLR lightweight robot: design and control concepts for robots in human environments

paper_content:

Purpose – The paper seeks to present a new generation of torque‐controlled light‐weight robots (LWR) developed at the Institute of Robotics and Mechatronics of the German Aerospace Center.Design/methodology/approach – An integrated mechatronic design approach for LWR is presented. Owing to the partially unknown properties of the environment, robustness of planning and control with respect to environmental variations is crucial. Robustness is achieved in this context through sensor redundancy and passivity‐based control. In the DLR root concept, joint torque sensing plays a central role.Findings – In order to act in unstructured environments and interact with humans, the robots have design features and control/software functionalities which distinguish them from classical robots, such as: load‐to‐weight ratio of 1:1, torque sensing in the joints, active vibration damping, sensitive collision detection, compliant control on joint and Cartesian level.Practical implications – The DLR robots are excellent rese...
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paper_title: On making robots understand safety: Embedding injury knowledge into control

paper_content:

Enabling robots to safely interact with humans is an essential goal of robotics research. The developments achieved over recent years in mechanical design and control made it possible to have active cooperation between humans and robots in rather complex situations. For this, safe robot behavior even under worst-case situations is crucial and forms also a basis for higher-level decisional aspects. For quantifying what safe behavior really means, the definition of injury, as well as understanding its general dynamics, are essential. This insight can then be applied to design and control robots such that injury due to robot-human impacts is explicitly taken into account. In this paper we approach the problem from a medical injury analysis point of view in order to formulate the relation between robot mass, velocity, impact geometry and resulting injury qualified in medical terms. We transform these insights into processable representations and propose a motion supervisor that utilizes injury knowledge for generating safe robot motions. The algorithm takes into account the reflected inertia, velocity, and geometry at possible impact locations. The proposed framework forms a basis for generating truly safe velocity bounds that explicitly consider the dynamic properties of the manipulator and human injury.
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paper_title: Impedance Control of Flexible Robot Manipulators

paper_content:

Force control is very important for many practical manipulation tasks of robot manipulators, such as, assembly, grinding, deburring that associate with interaction between the end-effector of the robot and the environment. Force control of the robot manipulator can be break down into two categories: Position/Force Hybrid Control and Impedance Control. The former is focused on regulation of both position and manipulation force of the end-effector on the tangent and perpendicular directions of the contact surface. The later, however, is to realize desired dynamic characteristics of the robot in response to the interaction with the environment. The desired dynamic characteristics are usually prescribed with dynamic models of systems consisting of mass, spring, and dashpot. Literature demonstrates that various control methods in this area have been proposed during recent years, and the intensive research has mainly focused on rigid robot manipulators. On the research area of force control for flexible robots, however, only a few reports can be found. Regarding force control of the flexible robot, a main body of the research has concentrated on the position/force hybrid control. A force control law was presented based on a linearized motion equation[l]. A quasi-static force/position control method was proposed for a two-link planar flexible robot [2]. For serial connected flexible-macro and rigid-micro robot arm system, a position/force hybrid control method was proposed [3]. An adaptive hybrid force/position controller was resented for automated deburring[4]. Two-time scale position/force controllers were proposed using perturbation techniques[5],[6]. Furthermore, a hybrid position-force control method for two cooperated flexible robots was also presented [7]. The issue on impedance control of the flexible robot attracts many attentions as well. But very few research results have been reported. An impedance control scheme was presented for micro-macro flexible robot manipulators [8]. In this method, the controllers of the micro arm (rigid arm) and macro arm (flexible arm) are designed separately, and the micro arm is controlled such that the desired local impedance characteristics of end-effector are achieved. An adaptive impedance control method was proposed for n-link flexible robot manipulators in the presence of parametric uncertainties in the dynamics, and the effectiveness was confirmed by simulation results using a 2-link flexible robot [9].
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paper_title: Robust impedance control

paper_content:

Industrial robots are confronted with performing tasks where a contact with their environment occurs. Therefore, there is a need for control algorithms with position tracking performance and force control ability. Up to date many algorithms have been proposed which deal with robot motion and force control. In this paper a robust impedance control law based on an attractive theory of sliding mode is proposed. The control law guarantees a robot predefined impedance and therefore a force regulation based on the possessed impedance properties is feasible. The proposed impedance controller is used in a force-tracking task. Experimental results on a simple 1-DOF mechanism and 3-DOF direct drive robot mechanism are reported.
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paper_title: Cartesian impedance control on five-finger dexterous robot hand DLR-HIT II with flexible joint

paper_content:

This paper presents an impedance controller for five-finger dexterous robot hand DLR-HIT II, which is derived in Cartesian space. By considering flexibility in finger joints and strong mechanical couplings in differential gear-box, modeling and control of the robot hand are described in this paper. The model-based friction estimation and velocity observer are carried out with an extended Kalman filter, which is implemented with parameters estimated by Least Squares Method. The designed estimator demonstrates good prediction performance, as shown in the experimental results. Stability analysis of the proposed impedance controller is carried out and described in this paper. Impedance control experiments are conducted with the five-finger dexterous robot hand DLR-HIT II in Cartesian coordinates system to help study the effectiveness of the proposed controller with friction compensation and hardware architecture.
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paper_title: Quantitative Safety Guarantees for Physical Human-Robot Interaction

paper_content:

If robots are to be introduced into the human world as assistants to aid a person in the completion of a manual task two key problems of today's robots must be solved. The human-robot interface must be intuitive to use and the safety of the user with respect to injuries inflicted by collisions with the robot must be guaranteed. In this paper we describe the formulation and implementation of a control strategy for robot manipulators which provides quantitative safety guarantees for the user of assistant-type robots. We propose a control scheme for robot manipulators that restricts the torque commands of a position control algorithm to values that comply to preset safety restrictions. These safety restrictions limit the potential impact force of the robot in the case of a collision with a person. Such accidental collisions may occur with any part of the robot and therefore the impact force not only of the robot's hand but of all surfaces is controlled by the scheme. The integration of a visual control inter...
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paper_title: A novel passivity-based control law for safe human-robot coexistence

paper_content:

This paper presents a new control law for robotic manipulators in unstructured environments which guarantees the achievement of the goal position without incurring in local minima. The passivity of the closed-loop system renders this control scheme well-suited for human-robot coexistence, especially when the robot is supposed to share its workspace with humans. The given control law has been implemented and experimentally tested in a realistic scenario, demonstrating the effectiveness in driving the robot to a given configuration in a cluttered environment without any offline planning phase.
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paper_title: Cartesian impedance control for dexterous manipulation

paper_content:

In this work, a cartesian impedance controller purposely designed for dexterous manipulation is described. Based on the main features of the DLR Hand II, concerning kinematic structure and sensory equipment of fingers, this control strategy allows to overcome the main problems encountered in fine manipulation, namely: effects of the friction (and unmodeled dynamics) on robot performances and occurrence of singularity conditions. The achieved control scheme bas been experimentally validated by testing it on a finger of the DLR Hand.
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paper_title: An overview of robot force control

paper_content:

This paper reports on the existing robot force control algorithms and their composition based on the review of 75 papers on this subject. The objective is to provide a pragmatic exposition with speciality on their differences and different application conditions, and to give a guide of the existing robot force control algorithms. The previous work can be categorized into discussion, design and/or application of fundamental force control techniques, stability analysis of the various control algorithms, and the advanced methods. Advanced methods combine the fundamental force control techniques with advanced control algorithms such as adaptive, robust and learning control strategies.
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paper_title: Adaptive impedance control for safe robot manipulator

paper_content:

In this paper, we proposed an algorithm that can move robot manipulator with constant velocity in robust stability. The moving velocity of arm is controlled by an algorithm of the adaptive impedance control, which increases operation efficiency and keeps the advantages of the impedance control. This control algorithm will satisfy practical and efficient applications, such as manipulator control that assist safely in feeding impaired patients. The manipulator is firstly based on 1 DOF robot arm which rotates in the vertical plane. The effect of gravity was eliminated by robust control. The algorithm of robust adaptive impedance control increases operation efficiency and operation stability. Furthermore, the impedance with the robust control design eliminates the steady state error which is caused by the static friction, and the reaction torque observer reduces the ripple of torque and smoothes the output of velocity.
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paper_title: Control of Interactive Robotic Interfaces: A Port-Hamiltonian Approach (Springer Tracts in Advanced Robotics)

paper_content:

When two physical systems (e.g. a robot and its environment) interact they exchange energy through localized ports and, in order to control their interaction, ::: it is necessary to control the exchanged energy. ::: The port-Hamiltonian formalism provides a general framework for modeling physical systems based on the concepts of energy, interconnection and power ports which describe the phenomena of energy storage, energy exchange and external interaction respectively. ::: This monograph deals with energy based control of interactive robotic interfaces and the port-Hamiltonian framework is exploited both for modeling and controlling interactive robotic interfaces. Using the port-Hamiltonian ::: framework, it is possible to identify the energetic properties that have to be controlled in order to achieve a desired interactive behavior and it is possible to build a port-Hamiltonian controller that properly regulates the robotic interface by shaping its energetic properties. ::: Thanks to its generality, the port-Hamiltonian formalism allows to model and control also complex interactive robotic interfaces in a very natural way. ::: In this book, a port-Hamiltonian approach for regulating the interaction between a robot and a local environment, a virtual environment (i.e. haptic interfaces) and a remote environment (i.e. bilateral telemanipulation systems) is developed.
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paper_title: The “DLR crash report”: Towards a standard crash-testing protocol for robot safety - Part II: Discussions

paper_content:

After analyzing fundamental impact characteristics of robot-human collisions in our previous work, the intention in the present paper is to augment existing knowledge in this field, verify previously given statements with standardized equipment of the German Automobile Club (ADAC), and provide a crash-test report for robots in general. Various new insights are achieved and a systematic and extensive set of data is provided. The presented work is divided into two papers. The main purpose of Part I is to give, similarly to reports known from the automobile world1, a fact based and result oriented view on our newest robot crash-test experiments. In Part II detailed discussions of the results listed in the present paper and recommendations towards a standard crash-test protocol for robot safety are carried out.
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paper_title: The “DLR Crash Report”: Towards a standard crash-testing protocol for robot safety - Part I: Results

paper_content:

After analyzing fundamental impact characteristics of robot-human collisions in our previous work, the intention in the present paper is to augment existing knowledge in this field, verify previously given statements with standardized equipment of the German Automobile Club (ADAC), and provide a crash-test report for robots in general. Various new insights are achieved and a systematic and extensive set of data is provided. The presented work is divided into two papers. The main purpose of Part I is to give, similarly to reports known from the automobile world1, a fact based and result oriented view on our newest robot crash-test experiments. In Part II detailed discussions of the results listed in the present paper and recommendations towards a standard crash-test protocol for robot safety are carried out.
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Title: The Safety of Domestic Robotics: A Survey of Various Safety-Related Publications
Section 1: Safety in Domestic Robots
Description 1: Discuss the background, significance, and general safety requirements of domestic robots, highlighting key issues and standard safety guidelines.

Section 2: Safety Criteria and Metrics
Description 2: Explain the meaningful criteria and metrics necessary for analyzing safety and defining injury levels of potential hazardous conditions in domestic robotics.

Section 3: Acceleration Based
Description 3: Explore acceleration-based safety metrics, such as the head injury criteria (HIC), and their relevance to injury prediction in the event of a collision.

Section 4: Force Based
Description 4: Investigate force-based safety metrics which consider excessive force as the main cause of injury and discuss related safety models and indices.

Section 5: Energy/Power Based
Description 5: Outline energy and power-based safety metrics, including those evaluating the rate and transfer of kinetic energy during an impact.

Section 6: Other Parameter Based
Description 6: Examine alternative safety metrics based on different parameters like pain tolerance, maximum stress, and energy density limits.

Section 7: Mechanical Design and Actuation
Description 7: Detail the various mechanical design and actuation strategies employed to enhance the intrinsic safety of domestic robots, including compliance and lightweight design.

Section 8: Controller Design
Description 8: Discuss the control schemes and strategies necessary for safe interaction between the robot and its environment, including impedance control and passivity-based controllers.

Section 9: Conclusions
Description 9: Summarize the key insights from the survey, emphasizing the importance of safety metrics, mechanical design, actuation, and controller interactions in domestic robotics.