Robot Collisions: A Survey on Detection, Isolation, and Identification
---
paper_title: Collision detection, isolation and identification for humanoids

paper_content:

High-performance collision handling, which is divided into the five phases detection, isolation, estimation, classification and reaction, is a fundamental robot capability for safe and sensitive operation/interaction in unknown environments. For complex humanoid robots collision handling is obviously significantly more complex than for classical static manipulators. In particular, the robot stability during the collision reaction phase has to be carefully designed and relies on high fidelity contact information that is generated during the first three phases. In this paper, a unified realtime algorithm is presented for determining unknown contact forces and contact locations for humanoid robots based on proprioceptive sensing only, i.e. joint position, velocity and torque, as well as force/torque sensing along the structure. The proposed scheme is based on nonlinear model-based momentum observers that are able to recover the unknown contact forces and the respective locations. The dynamic loads acting on internal force/torque sensors are also corrected based on a novel nonlinear compensator. The theoretical capabilities of the presented methods are evaluated in simulation with the Atlas robot. In summary, we propose a full solution to the problem of collision detection, collision isolation and collision identification for the general class of humanoid robots.
---
paper_title: Residual-based contacts estimation for humanoid robots

paper_content:

The residual method for detecting contacts is a promising approach to allow physical interaction tasks with humanoid robots. Nevertheless, the classical formulation, as developed for fixed-base robots, cannot be directly applied to floating-base systems. This paper presents a novel formulation of the residual based on the floating-base dynamics modeling of humanoids. This leads to the definition of the internal and external residual. The first estimates the joints effort due to the external perturbation acting on the robot. The latter is an estimation of the external forces acting on the floating-base of the robot. The potential of the method is shown proposing a simple internal residual-based reaction strategy, and a procedure for estimating the contact point that combines both the internal and external residuals.
---
paper_title: Pushing a robot along - A natural interface for human-robot interaction

paper_content:

Humans use direct physical interactions to move objects and guide people, and the same should be done with robots. However, most of today's mobile robots use non-backdrivable motors for locomotion, making them potentially dangerous in case of collision. This paper presents a robot, named AZIMUT-3, equipped with differential elastic actuators that are backdrivable and torque controlled, capable of being force-guided. Real world results demonstrate that AZIMUT-3 can move efficiently in response to physical commands given by a human pushing the robot in the intended direction.
---
paper_title: An atlas of physical human-robot interaction

paper_content:

Abstract A broad spectrum of issues have to be addressed in order to tackle the problem of a safe and dependable physical Human–Robot Interaction (pHRI). In the immediate future, metrics related to safety and dependability have to be found in order to successfully introduce robots in everyday enviornments. 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, our discussion focuses on the peculiar aspects of “physical” interaction with robots. In particular, safety and dependability are the underlying evaluation criteria for mechanical design, actuation, and control architectures. Mechanical and control issues are discussed with emphasis on techniques that provide safety in an intrinsic way or by means of control components. Attention is devoted to dependability, mainly related to sensors, control architectures, and fault handling and tolerance. Suggestions are provided to draft metrics for evaluating safety and dependability in pHRI, and references to the works of the scientific groups involved in the pHRI research complete the study. The present atlas is a result of the EURON perspective research project “Physical Human–Robot Interaction in anthropic DOMains (PHRIDOM)”, aimed at charting the new territory of pHRI, and constitutes the scientific basis for the ongoing STReP project “Physical Human–Robot Interaction: depENDability and Safety (PHRIENDS)”, aimed at developing key components for the next generation of robots, designed to share their environment with people.
---
paper_title: Simultaneous estimation of aerodynamic and contact forces in flying robots: Applications to metric wind estimation and collision detection

paper_content:

In this paper, we extend our previous external wrench estimation scheme for flying robots with an aerodynamic model such that we are able to simultaneously estimate aerodynamic and contact forces online. This information can be used to identify the metric wind velocity vector via model inversion. Noticeably, we are still able to accurately sense collision forces at the same time. Discrimination between the two is achieved by identifying the natural contact frequency characteristics for both “interaction cases”. This information is then used to design suitable filters that are able to separate the aerodynamic from the collision forces for subsequent use. Now, the flying system is able to correctly respond to typical contact forces and does not accidentally “hallucinate” contacts due to a misinterpretation of wind disturbances. Overall, this paper generalizes our previous results towards significantly more complex environments.
---
paper_title: An approach to collision detection and recovery motion in industrial robot

paper_content:

The authors describe a method of collision detection and the following continued avoidance motion. In an industrial robot, if there is an unknown obstacle on the trajectory, it is required to detect the collision against the obstacle and to avoid it autonomously. In the proposed method, an extra sensor such as the tactile sensor or the visual sensor for detecting the collision is not necessary. Instead of these sensors, the collision is detected by the signal of the disturbance observer. The algorithm for how the robot knows the collision is coming and avoids the obstacle is shown. This algorithm is simple and easy to apply to the robot controller. Several experimental results are shown. >
---
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.
---
paper_title: Robot Motion Planning

paper_content:

1 Introduction and Overview.- 2 Configuration Space of a Rigid Object.- 3 Obstacles in Configuration Space.- 4 Roadmap Methods.- 5 Exact Cell Decomposition.- 6 Approximate Cell Decomposition.- 7 Potential Field Methods.- 8 Multiple Moving Objects.- 9 Kinematic Constraints.- 10 Dealing with Uncertainty.- 11 Movable Objects.- Prospects.- Appendix A Basic Mathematics.- Appendix B Computational Complexity.- Appendix C Graph Searching.- Appendix D Sweep-Line Algorithm.- References.
---
paper_title: Artificial Skin in Robotics

paper_content:

Artificial Skin - A comprehensive interface for system-environment interaction - This thesis investigates a multifunctional artificial skin as touch sensitive whole-body cover for robotic systems. To further the evolution from tactile sensors to an implementable artificial skin a general concept for the design process is derived. A standard test procedure is proposed to evaluate the performance. The artificial skin contributes to a safe and intuitive physical human robot interaction.
---
paper_title: OpenRAVE : A Planning Architecture for Autonomous Robotics

paper_content:

One of the challenges in developing real-world autonomous robots is the need for integrating and rigorously testing high-level scripting, motion planning, perception, and control algorithms. For this purpose, we introduce an open-source cross-platform software architecture called OpenRAVE, the Open Robotics and Animation Virtual Environment. OpenRAVE is targeted for real-world autonomous robot applications, and includes a seamless integration of 3-D simulation, visualization, planning, scripting and control. A plugin architecture allows users to easily write custom controllers or extend functionality. With OpenRAVE plugins, any planning algorithm, robot controller, or sensing subsystem can be distributed and dynamically loaded at run-time, which frees developers from struggling with monolithic code-bases. Users of OpenRAVE can concentrate on the development of planning and scripting aspects of a problem without having to explicitly manage the details of robot kinematics and dynamics, collision detection, world updates, and robot control. The OpenRAVE architecture provides a flexible interface that can be used in conjunction with other popular robotics packages such as Player and ROS because it is focused on autonomous motion planning and high-level scripting rather than low-level control and message protocols. OpenRAVE also supports a powerful network scripting environment which makes it simple to control and monitor robots and change execution flow during run-time. One of the key advantages of open component architectures is that they enable the robotics research community to easily share and compare algorithms.
---
paper_title: Elastic Strips: A Framework for Motion Generation in Human Environments

paper_content:

Robotic applications are expanding into dynamic, unstructured, and populated environments. Mechanisms specifically designed to address the challenges arising in these environments, such as humanoid robots, exhibit high kinematic complexity. This creates the need for new algorithmic approaches to motion generation, capable of performing task execution and real-time obstacle avoidance in high-dimensional configuration spaces. The elastic strip framework presented in this paper enables the execution of a previously planned motion in a dynamic environment for robots with many degrees of freedom. To modify a motion in reaction to changes in the environment, real-time obstacle avoidance is combined with desired posture behavior. The modification of a motion can be performed in a task-consistent manner, leaving task execution unaffected by obstacle avoidance and posture behavior. The elastic strip framework also encompasses methods to suspend task behavior when its execution becomes inconsistent with other const...
---
paper_title: A depth space approach to human-robot collision avoidance

paper_content:

In this paper a real-time collision avoidance approach is presented for safe human-robot coexistence. The main contribution is a fast method to evaluate distances between the robot and possibly moving obstacles (including humans), based on the concept of depth space. The distances are used to generate repulsive vectors that are used to control the robot while executing a generic motion task. The repulsive vectors can also take advantage of an estimation of the obstacle velocity. In order to preserve the execution of a Cartesian task with a redundant manipulator, a simple collision avoidance algorithm has been implemented where different reaction behaviors are set up for the end-effector and for other control points along the robot structure. The complete collision avoidance framework, from perception of the environment to joint-level robot control, is presented for a 7-dof KUKA Light-Weight-Robot IV using the Microsoft Kinect sensor. Experimental results are reported for dynamic environments with obstacles and a human.
---
paper_title: Safe human-robot-cooperation: image-based collision detection for industrial robots

paper_content:

This paper analyzes the problem of sensor-based collision detection for an industrial robotic manipulator. A method to perform collision tests based on images taken from several stationary cameras in the work cell is presented. The collision test works entirely based on the images, and does not construct a representation of the Cartesian space. It is shown how to perform a collision test for all possible robot configurations using only a single set of images taken simultaneously.
---
paper_title: Force/tactile sensor for robotic applications

paper_content:

Abstract The paper describes the detailed design and the prototype characterization of a novel tactile sensor 1 for robotic applications. The sensor is based on a two-layer structure, i.e. a printed circuit board with optoelectronic components below a deformable silicon layer with a suitably designed geometry. The mechanical structure of the sensor has been optimized in terms of geometry and material physical properties to provide the sensor with different capabilities. The first capability is to work as a six-axis force/torque sensor; additionally, the sensor can be used as a tactile sensor providing a spatially distributed information exploited to estimate the geometry of the contact with a stiff external object. An analytical physical model and a complete experimental characterization of the sensor are presented.
---
paper_title: Real-time collision avoidance in teleoperated whole-sensitive robot arm manipulators

paper_content:

The problem of generating collision-free motion in an operator-assisted teleoperated robot arm manipulator system is discussed. The concentration is on several system requirements: a real real-time operation, a guarantee of collision-free motion for the entire body of the arm manipulator, and an ability to handle obstacles of arbitrary shapes. The suggested methodology draws on recent work on motion planning with incomplete information for whole-sensitive robots. >
---
paper_title: Real-time optimization-based planning in dynamic environments using GPUs

paper_content:

We present a novel algorithm to compute collision-free trajectories in dynamic environments. Our approach is general and does not require a priori knowledge about the obstacles or their motion. We use a replanning framework that interleaves optimization-based planning with execution. Furthermore, we describe a parallel formulation that exploits a high number of cores on commodity graphics processors (GPUs) to compute a high-quality path in a given time interval. We derive bounds on how parallelization can improve the responsiveness of the planner and the quality of the trajectory.
---
paper_title: Directions Toward Effective Utilization of Tactile Skin: A Review

paper_content:

A wide variety of tactile (touch) sensors exist today for robotics and related applications. They make use of various transduction methods, smart materials and engineered structures, complex electronics, and sophisticated data processing. While highly useful in themselves, effective utilization of tactile sensors in robotics applications has been slow to come and largely remains elusive today. This paper surveys the state of the art and the research issues in this area, with the emphasis on effective utilization of tactile sensors in robotic systems. One specific with the use of tactile sensing in robotics is that the sensors have to be spread along the robot body, the way the human skin is-thus dictating varied 3-D spatio-temporal requirements, decentralized and distributed control, and handling of multiple simultaneous tactile contacts. Satisfying these requirements pose challenges to making tactile sensor modality a reality. Overcoming these challenges requires dealing with issues such as sensors placement, electronic/mechanical hardware, methods to access and acquire signals, automatic calibration techniques, and algorithms to process and interpret sensing data in real time. We survey this field from a system perspective, recognizing the fact that the system performance tends to depend on how its various components are put together. It is hoped that the survey will be of use to practitioners designing tactile sensing hardware (whole-body or large-patch sensor coverage), and to researchers working on cognitive robotics involving tactile sensing.
---
paper_title: CHOMP: Gradient optimization techniques for efficient motion planning

paper_content:

Existing high-dimensional motion planning algorithms are simultaneously overpowered and underpowered. In domains sparsely populated by obstacles, the heuristics used by sampling-based planners to navigate “narrow passages” can be needlessly complex; furthermore, additional post-processing is required to remove the jerky or extraneous motions from the paths that such planners generate. In this paper, we present CHOMP, a novel method for continuous path refinement that uses covariant gradient techniques to improve the quality of sampled trajectories. Our optimization technique both optimizes higher-order dynamics and is able to converge over a wider range of input paths relative to previous path optimization strategies. In particular, we relax the collision-free feasibility prerequisite on input paths required by those strategies. As a result, CHOMP can be used as a standalone motion planner in many real-world planning queries. We demonstrate the effectiveness of our proposed method in manipulation planning for a 6-DOF robotic arm as well as in trajectory generation for a walking quadruped robot.
---
paper_title: Reactive mobile manipulation using dynamic trajectory tracking

paper_content:

A solution to the trajectory tracking problem for mobile manipulators is proposed, that allows for the base to be influenced by a reactive, obstacle avoidance behavior. Given a trajectory for the gripper to follow, a tracking algorithm for the manipulator is designed, and at the same time the base motions are generated in such a way that the base is coordinated with the gripper. Furthermore, it is shown that the method allows arbitrary upper and lower bounds on the gripper-base distance to be set and this can be achieved without introducing deadlocks into the system. The solution also ensures that the control effort, spent on slow base motions, is kept small.
---
paper_title: A Human-Aware Manipulation Planner

paper_content:

With recent advances in safe and compliant hardware and control, robots are close to finding their places in our homes. As the safety barrier between humans and robots is beginning to fade, the necessity to design pertinent robot behavior in human environments is becoming a crucial step. In order to obtain a safe, comfortable, and socially acceptable interaction, the robot should be engineered from top to bottom by considering the presence of the human. In this paper, we present a manipulation planning framework and its implementation human-aware manipulation planner. This planner generates paths not only safe but comfortable and “socially acceptable” as well by reasoning explicitly on human's kinematics, vision field, posture, and preferences. The planner, which is applied into “robot handing over an object” scenarios, breaks the human centric interaction that depends mostly on human effort and allows the robot to take initiative by computing automatically where the interaction takes place, thus decreasing the cognitive weight of interaction on human side.
---
paper_title: Collision detection system for manipulator based on adaptive impedance control law

paper_content:

In this paper, we propose a collision detection system based on a nonlinear adaptive impedance control law. The collision detection detects collisions of a manipulator with its environment without using external sensors. The adaptive impedance control law is employed to estimate the dynamic parameters of the manipulators, and allows the manipulator to have interaction with its environment. The system detects collisions based on the difference between the actual input torque to the manipulator and the reference input torque, which is calculated based on the estimated parameters of the manipulator dynamics. The manipulator stops when a collision detection system is implemented in an industrial manipulator and experimental results illustrate the validity of the proposed system.
---
paper_title: Real-Time Obstacle Avoidance for Manipulators and Mobile Robots

paper_content:

This paper presents a unique real-time obstacle avoidance approach for manipulators and mobile robots based on the artificial potential field concept. Collision avoidance, tradi tionally considered a high level planning problem, can be effectively distributed between different levels of control, al lowing real-time robot operations in a complex environment. This method has been extended to moving obstacles by using a time-varying artificial patential field. We have applied this obstacle avoidance scheme to robot arm mechanisms and have used a new approach to the general problem of real-time manipulator control. We reformulated the manipulator con trol problem as direct control of manipulator motion in oper ational space—the space in which the task is originally described—rather than as control of the task's corresponding joint space motion obtained only after geometric and kine matic transformation. Outside the obstacles' regions of influ ence, we caused the end effector to move in a straight line with an...
---
paper_title: STOMP: Stochastic trajectory optimization for motion planning

paper_content:

We present a new approach to motion planning using a stochastic trajectory optimization framework. The approach relies on generating noisy trajectories to explore the space around an initial (possibly infeasible) trajectory, which are then combined to produced an updated trajectory with lower cost. A cost function based on a combination of obstacle and smoothness cost is optimized in each iteration. No gradient information is required for the particular optimization algorithm that we use and so general costs for which derivatives may not be available (e.g. costs corresponding to constraints and motor torques) can be included in the cost function. We demonstrate the approach both in simulation and on a mobile manipulation system for unconstrained and constrained tasks. We experimentally show that the stochastic nature of STOMP allows it to overcome local minima that gradient-based methods like CHOMP can get stuck in.
---
paper_title: Human-robot collaborative manipulation planning using early prediction of human motion

paper_content:

In this paper we present a framework that allows a human and a robot to perform simultaneous manipulation tasks safely in close proximity. The proposed framework is based on early prediction of the human's motion. The prediction system, which builds on previous work in the area of gesture recognition, generates a prediction of human workspace occupancy by computing the swept volume of learned human motion trajectories. The motion planner then plans robot trajectories that minimize a penetration cost in the human workspace occupancy while interleaving planning and execution. Multiple plans are computed in parallel, one for each robot task available at the current time, and the trajectory with the least cost is selected for execution. We test our framework in simulation using recorded human motions and a simulated PR2 robot. Our results show that our framework enables the robot to avoid the human while still accomplishing the robot's task, even in cases where the initial prediction of the human's motion is incorrect. We also show that taking into account the predicted human workspace occupancy in the robot's motion planner leads to safer and more efficient interactions between the user and the robot than only considering the human's current configuration.
---
paper_title: Global path planning using artificial potential fields

paper_content:

The author describes a path planning technique for robotic manipulators and mobile robots in the presence of stationary obstacles. The planning consists of applying potential fields around configuration-space obstacles and using these fields to select a safe path for the robot to follow. The advantage of using potential fields in path planning is that they offer a relatively fast and effective way to solve for safe paths around obstacles. In the proposed method of path planning, a trial path is chosen and then modified under the influence of the potential field until an appropriate path is found. By considering the entire path, the problem of being trapped in a local minimum is greatly reduced, allowing the method to be used for global planning. The algorithm was tried with success on many different realistic planning problems. By way of illustration, the algorithm is applied to a two-dimensional revolute manipulator, a mobile robot capable of translation only, and a mobile robot capable of both translation and rotation. >
---
paper_title: Fast vision-based minimum distance determination between known and unkown objects

paper_content:

We present a method for quickly determining the minimum distance between multiple known and multiple unkown objects within a camera image. Known objects are objects with known geometry, position, orientation, and configuration. Unkown objects are objects which have to be detected by a vision sensor but with unkown geometry, position, orientation and configuration. The known objects are modeled and expanded in 3D and then projected into a camera image. The camera image is classified into object areas including known and unknown objects and into non-object areas. The distance is conservatively estimated by searching for the largest expansion radius where the projected model does not intersect the object areas classified as unknown in the camera image. The method requires only minimal computation times and can be used for surveillance and safety applications.
---
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.
---
paper_title: Sensorless Robot Collision Detection and Hybrid Force/Motion Control

paper_content:

We consider the problem of real-time detection of collisions between a robot manipulator and obstacles of unknown geometry and location in the environment without the use of extra sensors. The idea is to handle a collision at a generic point along the robot as a fault of its actuating system. A previously developed dynamic FDI (fault detection and isolation) technique is used, which does not require acceleration or force measurements. The actual robot link that has collided can also be identified. Once contact has been detected, it is possible to switch to a suitably defined hybrid force/motion controller that enables to keep the contact, while sliding on the obstacle, and to regulate the interaction force. Simulation results are shown for a two-link planar robot.
---
paper_title: The role of the robot mass and velocity in physical human-robot interaction - Part II: Constrained blunt impacts

paper_content:

Accidents occurring with classical industrial robots often lead to fatal injuries. Presumably, this is to a great extent caused by the possibility of clamping the human in the confined workspace of the robot. Before generally allowing physical cooperation of humans and robots in future applications it is therefore absolutely crucial to analyze this extremely dangerous situation. In this paper we will investigate many aspects relevant to this sort of injury mechanisms and discuss the importance to domestic environments or production assistants. Since clamped impacts are intrinsically more dangerous than free ones it is fundamental to discuss and evaluate metrics to ensure safe interaction if clamping is possible. We compare various robots with respect to their injury potential leading to a main safety requirement of robot design: Reduce the intrinsic injury potential of a robot by reducing its weight.
---
paper_title: Using tactile sensation for learning contact knowledge: Discriminate collision from physical interaction

paper_content:

Detecting and interpreting contacts is a crucial aspect of physical Human-Robot Interaction. In order to discriminate between intended and unintended contact types, we derive a set of linear and non-linear features based on physical contact model insights and from observing real impact data that may even rely on proprioceptive sensation only. We implement a classification system with a standard non-linear Support Vector Machine and show empirically both in simulations and on a real robot the high accuracy in off- as well as on-line settings of the system. We argue that these successful results are based on our feature design derived from first principles.
---
paper_title: Exploiting robot redundancy in collision detection and reaction

paper_content:

We present a method that allows automatic reaction of a robot to physical collisions, while preserving as much as possible the execution of a Cartesian task for which the robot is kinematically redundant. The work is motivated by human-robot interaction scenarios, where ensuring safety is of primary concern whereas preserving task performance is an appealing secondary goal. Unexpected collisions may occur anywhere along the manipulator structure. Their fast detection is realized using our previous momentum-based method, which does not require any external sensing. The reaction torque applied to the joints reduces the effective robot inertia seen at the contact and lets the robot safely move away from the collision area. If we wish, however, to continue the execution of a Cartesian trajectory, robot redundancy can be exploited by projecting the reaction torque into the null space of a dynamic task matrix so as not to affect the original end-effector motion. This leads to the use of the so-called dynamically consistent approach to redundancy resolution, which is further elaborated in the paper. A partial task relaxation strategy can also be devised, with the objective of keeping contact forces below a user-defined safety threshold. Simulation results are reported for the 7R KUKA/DLR lightweight robot arm.
---
paper_title: Modular state-based behavior control for safe human-robot interaction: A lightweight control architecture for a lightweight robot

paper_content:

In this paper we present a novel control architecture for realizing human-friendly behaviors and intuitive state based programming. The design implements strategies that take advantage of sophisticated soft-robotics features for providing reactive, robust, and safe robot actions in dynamic environments. Quick access to the various functionality of the robot enables the user to develop flexible hybrid state automata for programming complex robot behaviors. The real-time robot control takes care of all safety critical aspects and provides reactive reflexes that directly respond to external stimuli.
---
paper_title: Collision detection and reaction: A contribution to safe physical Human-Robot Interaction

paper_content:

In the framework of physical human-robot interaction (pHRI), methodologies and experimental tests are presented for the problem of detecting and reacting to collisions between a robot manipulator and a human being. Using a lightweight robot that was especially designed for interactive and cooperative tasks, we show how reactive control strategies can significantly contribute to ensuring safety to the human during physical interaction. Several collision tests were carried out, illustrating the feasibility and effectiveness of the proposed approach. While a subjective ldquosafetyrdquo feeling is experienced by users when being able to naturally stop the robot in autonomous motion, a quantitative analysis of different reaction strategies was lacking. In order to compare these strategies on an objective basis, a mechanical verification platform has been built. The proposed collision detection and reactions methods prove to work very reliably and are effective in reducing contact forces far below any level which is dangerous to humans. Evaluations of impacts between robot and human arm or chest up to a maximum robot velocity of 2.7 m/s are presented.
---
paper_title: External force estimation using joint torque sensors and its application to impedance control of a robot manipulator

paper_content:

This paper proposes an algorithm to estimate external forces exerted on the end-effector of a robot manipulator using information from joint torque sensors (JTS). The algorithm is the combination of Time Delay Estimation (TDE) and input estimation technique where the external force is considered as an unknown input to the robot manipulator. Based on TDE's idea, the estimator which does not require an accurate dynamics model of the robot manipulator is developed. The simultaneous input and state estimation (SISE) is used to reduce not only nonlinear uncertainties of the robot dynamics but also the noise of measurements. The performance of the proposed estimation algorithm is evaluated through an application to impedance control of a four degree-of-freedom manipulator.
---
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.
---
paper_title: An adapt-and-detect actuator FDI scheme for robot manipulators

paper_content:

An adaptive scheme is presented for actuator fault detection and isolation (FDI) in robotic systems, based on the use of generalized momenta and of a suitable overparametrization of the uncertain robot dynamics. This allows to obtain an accurate and reliable detection and isolation of possibly concurrent faults also during the parameter adaptation phase. Experimental results are reported for a planar robot under gravity, considering partial, total, or bias-type failures of the motor torques.
---
paper_title: Simultaneous estimation of aerodynamic and contact forces in flying robots: Applications to metric wind estimation and collision detection

paper_content:

In this paper, we extend our previous external wrench estimation scheme for flying robots with an aerodynamic model such that we are able to simultaneously estimate aerodynamic and contact forces online. This information can be used to identify the metric wind velocity vector via model inversion. Noticeably, we are still able to accurately sense collision forces at the same time. Discrimination between the two is achieved by identifying the natural contact frequency characteristics for both “interaction cases”. This information is then used to design suitable filters that are able to separate the aerodynamic from the collision forces for subsequent use. Now, the flying system is able to correctly respond to typical contact forces and does not accidentally “hallucinate” contacts due to a misinterpretation of wind disturbances. Overall, this paper generalizes our previous results towards significantly more complex environments.
---
paper_title: Collision detection and reaction: A contribution to safe physical Human-Robot Interaction

paper_content:

In the framework of physical human-robot interaction (pHRI), methodologies and experimental tests are presented for the problem of detecting and reacting to collisions between a robot manipulator and a human being. Using a lightweight robot that was especially designed for interactive and cooperative tasks, we show how reactive control strategies can significantly contribute to ensuring safety to the human during physical interaction. Several collision tests were carried out, illustrating the feasibility and effectiveness of the proposed approach. While a subjective ldquosafetyrdquo feeling is experienced by users when being able to naturally stop the robot in autonomous motion, a quantitative analysis of different reaction strategies was lacking. In order to compare these strategies on an objective basis, a mechanical verification platform has been built. The proposed collision detection and reactions methods prove to work very reliably and are effective in reducing contact forces far below any level which is dangerous to humans. Evaluations of impacts between robot and human arm or chest up to a maximum robot velocity of 2.7 m/s are presented.
---
paper_title: Cartesian contact force estimation for robotic manipulators using Kalman filters and the generalized momentum

paper_content:

Estimating contact forces and torques in Cartesian space enables force-controlled robotic applications as well as collision detection without costly additional sensing. A new approach towards online estimation of contact forces and torques at the tool center point from motor torques as well as joint angles and speeds is presented, which is based on analyzing the generalized momentum of the manipulator. Existing generalized momentum based methods are extended by designing a Kalman filter to estimate the generalized momentum as well as contact forces and torques simultaneously. This approach introduces additional degrees of freedom in the design of the estimator that are exploited to increase robustness with respect to disturbances such as uncertainty in joint friction. The method is verified by simulation results obtained from a dynamic model of an ABB YuMi, a dual-arm collaborative robot with 7DOF each arm.
---
paper_title: A Mathematical Introduction to Robotic Manipulation

paper_content:

INTRODUCTION: Brief History. Multifingered Hands and Dextrous Manipulation. Outline of the Book. Bibliography. RIGID BODY MOTION: Rigid Body Transformations. Rotational Motion in R3. Rigid Motion in R3. Velocity of a Rigid Body. Wrenches and Reciprocal Screws. MANIPULATOR KINEMATICS: Introduction. Forward Kinematics. Inverse Kinematics. The Manipulator Jacobian. Redundant and Parallel Manipulators. ROBOT DYNAMICS AND CONTROL: Introduction. Lagrange's Equations. Dynamics of Open-Chain Manipulators. Lyapunov Stability Theory. Position Control and Trajectory Tracking. Control of Constrained Manipulators. MULTIFINGERED HAND KINEMATICS: Introduction to Grasping. Grasp Statics. Force-Closure. Grasp Planning. Grasp Constraints. Rolling Contact Kinematics. HAND DYNAMICS AND CONTROL: Lagrange's Equations with Constraints. Robot Hand Dynamics. Redundant and Nonmanipulable Robot Systems. Kinematics and Statics of Tendon Actuation. Control of Robot Hands. NONHOLONOMIC BEHAVIOR IN ROBOTIC SYSTEMS: Introduction. Controllability and Frobenius' Theorem. Examples of Nonholonomic Systems. Structure of Nonholonomic Systems. NONHOLONOMIC MOTION PLANNING: Introduction. Steering Model Control Systems Using Sinusoids. General Methods for Steering. Dynamic Finger Repositioning. FUTURE PROSPECTS: Robots in Hazardous Environments. Medical Applications for Multifingered Hands. Robots on a Small Scale: Microrobotics. APPENDICES: Lie Groups and Robot Kinematics. A Mathematica Package for Screw Calculus. Bibliography. Index Each chapter also includes a Summary, Bibliography, and Exercises
---
paper_title: Variable impedance actuators: A review

paper_content:

Variable Impedance Actuators (VIA) have received increasing attention in recent years as many novel applications involving interactions with an unknown and dynamic environment including humans require actuators with dynamics that are not well-achieved by classical stiff actuators. This paper presents an overview of the different VIAs developed and proposes a classification based on the principles through which the variable stiffness and damping are achieved. The main classes are active impedance by control, inherent compliance and damping actuators, inertial actuators, and combinations of them, which are then further divided into subclasses. This classification allows for designers of new devices to orientate and take inspiration and users of VIA's to be guided in the design and implementation process for their targeted application.
---
paper_title: The KUKA-DLR Lightweight Robot arm - a new reference platform for robotics research and manufacturing

paper_content:

Transforming research results into marketable products requires considerable endurance and a strong sense of entrepreneurship. The KUKA Lightweight Robot (LWR) is the latest outcome of a bilateral research collaboration between KUKA Roboter, Augsburg, and the Institute of Robotics and Mechatronics at the German Aerospace Center (DLR), Wessling. The LWR has unique characteristics including a low mass-payload ratio and a programmable, active compliance which enables researchers and engineers to develop new industrial and service robotics applications with unprecedented performance, making it a unique reference platform for robotics research and future manufacturing. The stages of product genesis, the most innovative features and first application examples are presented.
---
paper_title: An Acceleration-based State Observer for Robot Manipulators with Elastic Joints

paper_content:

Robots that use cycloidal gears, belts, or long shafts for transmitting motion from the motors to the driven rigid links display visco-elastic phenomena that can be assumed to be concentrated at the joints. For the design of advanced, possibly nonlinear, trajectory tracking control laws that are able to fully counteract the vibrations due to joint elasticity, full state feedback is needed. However, no robot with elastic joints has sensors available for its whole state, i.e., for measuring positions and velocities of both motors and links. Several nonlinear observers have been proposed in the past, assuming different reduced sets of measurements. We introduce here a new observer which uses only motor position sensing, together with accelerometers suitably mounted on the links of the robot arm. Its main advantage is that the error dynamics on the estimated state is independent from the dynamic parameters of the robot links, and can be tuned with standard decentralized linear techniques (locally to each joint). We present an experimental validation of this observer for the three base joints of a KUKA KR15/2 industrial robot and illustrate the control use of the obtained results.
---
paper_title: Collision detection and reaction: A contribution to safe physical Human-Robot Interaction

paper_content:

In the framework of physical human-robot interaction (pHRI), methodologies and experimental tests are presented for the problem of detecting and reacting to collisions between a robot manipulator and a human being. Using a lightweight robot that was especially designed for interactive and cooperative tasks, we show how reactive control strategies can significantly contribute to ensuring safety to the human during physical interaction. Several collision tests were carried out, illustrating the feasibility and effectiveness of the proposed approach. While a subjective ldquosafetyrdquo feeling is experienced by users when being able to naturally stop the robot in autonomous motion, a quantitative analysis of different reaction strategies was lacking. In order to compare these strategies on an objective basis, a mechanical verification platform has been built. The proposed collision detection and reactions methods prove to work very reliably and are effective in reducing contact forces far below any level which is dangerous to humans. Evaluations of impacts between robot and human arm or chest up to a maximum robot velocity of 2.7 m/s are presented.
---
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.
---
paper_title: Sensorless Robot Collision Detection and Hybrid Force/Motion Control

paper_content:

We consider the problem of real-time detection of collisions between a robot manipulator and obstacles of unknown geometry and location in the environment without the use of extra sensors. The idea is to handle a collision at a generic point along the robot as a fault of its actuating system. A previously developed dynamic FDI (fault detection and isolation) technique is used, which does not require acceleration or force measurements. The actual robot link that has collided can also be identified. Once contact has been detected, it is possible to switch to a suitably defined hybrid force/motion controller that enables to keep the contact, while sliding on the obstacle, and to regulate the interaction force. Simulation results are shown for a two-link planar robot.
---
paper_title: A modified newton-euler method for dynamic computations in robot fault detection and control

paper_content:

We present a modified recursive Newton-Euler method for computing some dynamic expressions that arise in two problems of fault detection and control of serial robot manipulators, and which cannot be evaluated numerically using the standard method. The two motivating problems are: i) the computation of the residual vector that allows accurate detection of actuator faults or unexpected collisions using only robot proprioceptive measurements, and ii) the evaluation of a passivity-based trajectory tracking control law. The modified Newton-Euler algorithm generates factorization matrices of the Coriolis and centrifugal terms that satisfy the skew-symmetric property. The computational advantages with respect to numerical evaluation of symbolically obtained dynamic expressions is illustrated on a 7R DLR lightweight manipulato
---
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.
---
paper_title: Collision detection and reaction: A contribution to safe physical Human-Robot Interaction

paper_content:

In the framework of physical human-robot interaction (pHRI), methodologies and experimental tests are presented for the problem of detecting and reacting to collisions between a robot manipulator and a human being. Using a lightweight robot that was especially designed for interactive and cooperative tasks, we show how reactive control strategies can significantly contribute to ensuring safety to the human during physical interaction. Several collision tests were carried out, illustrating the feasibility and effectiveness of the proposed approach. While a subjective ldquosafetyrdquo feeling is experienced by users when being able to naturally stop the robot in autonomous motion, a quantitative analysis of different reaction strategies was lacking. In order to compare these strategies on an objective basis, a mechanical verification platform has been built. The proposed collision detection and reactions methods prove to work very reliably and are effective in reducing contact forces far below any level which is dangerous to humans. Evaluations of impacts between robot and human arm or chest up to a maximum robot velocity of 2.7 m/s are presented.
---
paper_title: Localizing external contact using proprioceptive sensors: The Contact Particle Filter

paper_content:

In order for robots to interact safely and intelligently with their environment they must be able to reliably estimate and localize external contacts. This paper introduces CPF, the Contact Particle Filter, which is a general algorithm for detecting and localizing external contacts on rigid body robots without the need for external sensing. CPF finds external contact points that best explain the observed external joint torque, and returns sensible estimates even when the external torque measurement is corrupted with noise. We demonstrate the capability of the CPF to track multiple external contacts on a simulated Atlas robot, and compare our work to existing approaches.
---
paper_title: Collision detection, isolation and identification for humanoids

paper_content:

High-performance collision handling, which is divided into the five phases detection, isolation, estimation, classification and reaction, is a fundamental robot capability for safe and sensitive operation/interaction in unknown environments. For complex humanoid robots collision handling is obviously significantly more complex than for classical static manipulators. In particular, the robot stability during the collision reaction phase has to be carefully designed and relies on high fidelity contact information that is generated during the first three phases. In this paper, a unified realtime algorithm is presented for determining unknown contact forces and contact locations for humanoid robots based on proprioceptive sensing only, i.e. joint position, velocity and torque, as well as force/torque sensing along the structure. The proposed scheme is based on nonlinear model-based momentum observers that are able to recover the unknown contact forces and the respective locations. The dynamic loads acting on internal force/torque sensors are also corrected based on a novel nonlinear compensator. The theoretical capabilities of the presented methods are evaluated in simulation with the Atlas robot. In summary, we propose a full solution to the problem of collision detection, collision isolation and collision identification for the general class of humanoid robots.
---
paper_title: Localizing external contact using proprioceptive sensors: The Contact Particle Filter

paper_content:

In order for robots to interact safely and intelligently with their environment they must be able to reliably estimate and localize external contacts. This paper introduces CPF, the Contact Particle Filter, which is a general algorithm for detecting and localizing external contacts on rigid body robots without the need for external sensing. CPF finds external contact points that best explain the observed external joint torque, and returns sensible estimates even when the external torque measurement is corrupted with noise. We demonstrate the capability of the CPF to track multiple external contacts on a simulated Atlas robot, and compare our work to existing approaches.
---
paper_title: Estimation of contact forces using a virtual force sensor

paper_content:

Physical human-robot collaboration is character- ized by a suitable exchange of contact forces between human and robot, which can occur in general at any point along the robot structure. If the contact location and the exchanged forces were known in real time, a safe and controlled collaboration could be established. We present a novel approach that allows localizing the contact between a robot and human parts with a depth camera, while determining in parallel the joint torques generated by the physical interaction using the so-called resid- ual method. The combination of such exteroceptive sensing and model-based techniques is sufficient, under suitable conditions, for a reliable estimation of the actual exchanged force at the contact, realizing thus a virtual force sensor. Multiple contacts can be handled as well. We validate quantitatively the proposed estimation method with a number of static experiments on a KUKA LWR. An illustration of the use of estimated contact forces in the realization of collaborative behaviors is given, reporting preliminary experiments on a generalized admittance control scheme at the contact point.
---
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.
---
paper_title: Nonlinear decoupled motion-stiffness control and collision detection/reaction for the VSA-II variable stiffness device

paper_content:

Variable Stiffness Actuation (VSA) devices are being used to jointly address the issues of safety and performance in physical human-robot interaction. With reference to the VSA-II prototype, we present a feedback linearization approach that allows the simultaneous decoupling and accurate tracking of motion and stiffness reference profiles. The operative condition that avoids control singularities is characterized. Moreover, a momentum-based collision detection scheme is introduced, which does not require joint torque sensing nor information on the time-varying stiffness of the device. Based on the residual signal, a collision reaction strategy is presented that takes advantage of the proposed nonlinear control to rapidly let the arm bounce away after detecting the impact, while limiting contact forces through a sudden reduction of the stiffness. Simulations results are reported to illustrate the performance and robustness of the overall approach. Extensions to the multidof case of robot manipulators equipped with VSA-II devices are also considered.
---
paper_title: Friction observer and compensation for control of robots with joint torque measurement

paper_content:

In this paper we introduce a friction observer for robots with joint torque sensing (in particular for the DLR medical robot) in order to increase the positioning accuracy and the performance of torque control. The observer output corresponds to the low-pass filtered friction torque. It is used for friction compensation in conjunction with a MIMO controller designed for flexible joint arms. A passivity analysis is done for this friction compensation, allowing a Lyapunov based convergence analysis in the context of the nonlinear robot dynamics. For the complete controlled system, global asymptotic stability can be shown. Experimental results validate the practical efficiency of the approach.
---
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.
---
paper_title: Inertial Properties in Robotic Manipulation: An Object-Level Framework

paper_content:

Consideration of dynamics is critical in the analysis, design, and control of robot systems. This article presents an extensive study of the dynamic properties of several important classes of robotic structures and proposes a number of general dynamic strategies for their coordination and control. This work is a synthesis of both previous and new results developed within the task-oriented operational space formulation. Here we in troduce a unifying framework for the analysis and control of robotic systems, beginning with an analysis of inertial prop erties based on two models that independently describe the mass and inertial characteristics associated with linear and angular motions. To visualize these properties, we propose a new geometric representation, termed the belted ellipsoid, that displays the magnitudes of the mass/inertial properties directly rather than their square roots. Our study of serial macro/mini structures is based on two models of redundant mechanisms. The first is a description of th...
---
paper_title: Collision detection and reaction: A contribution to safe physical Human-Robot Interaction

paper_content:

In the framework of physical human-robot interaction (pHRI), methodologies and experimental tests are presented for the problem of detecting and reacting to collisions between a robot manipulator and a human being. Using a lightweight robot that was especially designed for interactive and cooperative tasks, we show how reactive control strategies can significantly contribute to ensuring safety to the human during physical interaction. Several collision tests were carried out, illustrating the feasibility and effectiveness of the proposed approach. While a subjective ldquosafetyrdquo feeling is experienced by users when being able to naturally stop the robot in autonomous motion, a quantitative analysis of different reaction strategies was lacking. In order to compare these strategies on an objective basis, a mechanical verification platform has been built. The proposed collision detection and reactions methods prove to work very reliably and are effective in reducing contact forces far below any level which is dangerous to humans. Evaluations of impacts between robot and human arm or chest up to a maximum robot velocity of 2.7 m/s are presented.
---
paper_title: The KUKA-DLR Lightweight Robot arm - a new reference platform for robotics research and manufacturing

paper_content:

Transforming research results into marketable products requires considerable endurance and a strong sense of entrepreneurship. The KUKA Lightweight Robot (LWR) is the latest outcome of a bilateral research collaboration between KUKA Roboter, Augsburg, and the Institute of Robotics and Mechatronics at the German Aerospace Center (DLR), Wessling. The LWR has unique characteristics including a low mass-payload ratio and a programmable, active compliance which enables researchers and engineers to develop new industrial and service robotics applications with unprecedented performance, making it a unique reference platform for robotics research and future manufacturing. The stages of product genesis, the most innovative features and first application examples are presented.
---

Title: Robot Collisions: A Survey on Detection, Isolation, and Identification

Section 1: Introduction
Description 1: Introduce the topic of robot collisions and the motivation behind studying detection, isolation, and identification of these collisions.

Section 2: Collision Event Pipeline and State of the Art
Description 2: Discuss the proposed collision event pipeline, detailing the phases from precollision to postcollision, and review the current state of the art in robot collision handling.

Section 3: Contribution
Description 3: Outline the unique contributions of the paper, including the proposed collision event pipeline, developed methods, and experimental comparisons.

Section 4: Robot Dynamics and Properties
Description 4: Summarize the dynamic modeling and relevant properties of rigid and flexible joint robots, incorporating collision dynamics.

Section 4.1: Rigid Robots
Description 4.1: Discuss the dynamics and properties specific to rigid robots.

Section 4.2: Robots with Flexible Joints
Description 4.2: Discuss the dynamics and properties specific to robots with flexible joints.

Section 5: Collision Monitoring Methods
Description 5: Describe various collision monitoring methods such as energy observers, torque estimations, and momentum-based observers, highlighting their advantages and disadvantages.

Section 5.1: Estimation of Power via Energy Observer
Description 5.1: Explain the use of energy observers to estimate external joint torque during collisions.

Section 5.2: Direct Estimation of External Joint Torque
Description 5.2: Discuss methods for algebraic estimation of external joint torque.

Section 5.3: Monitoring via Inverse Dynamics
Description 5.3: Outline the method of using inverse dynamics to monitor collisions.

Section 5.4: Estimation via Joint Velocity Observer
Description 5.4: Detail the use of joint velocity observers for collision detection.

Section 5.5: Estimation via Momentum Observer
Description 5.5: Explain the momentum observer approach to collision detection and the advantages this method offers.

Section 5.6: Computational Issues
Description 5.6: Discuss computational considerations for implementing the discussed monitoring methods.

Section 6: Detection, Isolation, and Identification
Description 6: Review methods for collision detection, isolation, and identification explaining how each phase can be addressed and the role of monitoring signals.

Section 6.1: Detection
Description 6.1: Explain how collision detection is determined using monitoring functions and address robustness issues.

Section 6.2: Isolation
Description 6.2: Detail the process of identifying the specific robot link involved in a collision.

Section 6.3: Identification
Description 6.3: Discuss techniques to estimate the collision joint torques and contact wrenches acting on the robot structure.

Section 7: Comparison of Methods for Rigid Robots
Description 7: Provide a systematic comparison of various collision monitoring methods, considering their computational effort, required measurements, and performance.

Section 8: Extension to Robots with Flexible Joints
Description 8: Explain how the collision monitoring methods can be extended to robots with flexible joints and discuss the different types of flexible joint robot implementations.

Section 9: Experimental Evaluation
Description 9: Present experimental results to validate the theoretical findings and compare the performance of different monitoring methods.

Section 9.1: Observer Dynamics
Description 9.1: Compare the dynamics and performance of velocity and momentum observers.

Section 9.2: Observer Errors and Thresholding
Description 9.2: Discuss the impact of various errors and the process of threshold tuning for robust collision detection.

Section 9.3: Performance of the Link Momentum Observer
Description 9.3: Analyze the performance, timing properties, and practical aspects of the link momentum observer for collision detection.

Section 9.4: Collision Detection with an Energy Observer
Description 9.4: Showcase the performance of the energy observer in detecting collisions during various robot activities.

Section 9.5: Collision Detection/Isolation with a Link Momentum Observer
Description 9.5: Validate the effectiveness of the link momentum observer for both detecting and isolating collisions through experimental setups.

Section 9.6: Estimating the External Force and Contact Point
Description 9.6: Demonstrate the capability of estimating external forces and the exact contact point during collisions.

Section 10: Conclusion
Description 10: Summarize the findings, emphasize the significance of the collision event pipeline, and highlight the practical implications of the developed methods for real-world applications.