A review of biodynamic feedthrough mitigation techniques
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paper_title: Theory for Roll-Ratchet Phenomenon in High-Performance Aircraft

paper_content:

Roll ratchet refers to a high-frequency oscillation that can occur in pilot-in-the-loop control of roll attitude in high-performance aircraft. The frequencies of oscillation typically are well beyond those associated with the more familiar pilot-induced oscillation. A structural model of the human pilot, which has been employed to provide a unie ed theory for aircraft handling qualities and pilot-induced oscillations, is employed here to provide a theory for the existence of roll ratchet. It is hypothesized and demonstrated using the structural model that the pilot’ s inappropriate use of vestibular acceleration feedback can cause this phenomenon, a possibility that has been discussed by other researchers. The possible ine uence of biodynamic feedback on roll ratchet also is discussed.
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paper_title: Dynamical analysis and suppression of human hunting in the excavator operation

paper_content:

The paper deals with human hunting phenomena, which is one of the coupled vibration phenomena between the vehicle and the operator on board, appearing at the operation of the small-sized excavator and degrades operativity. This phenomena is related not only to the vehicle dynamical characteristic but also to human-operator's dynamical characteristic. To analyze this phenomenon, it is necessary to consider the vehicle-operator dynamic model. We first derived a mathematical model, which has six degrees of freedom to analyze this phenomenon. Up and down motion of the excavator-boom is simulated, and it agrees with the phenomenon well. The linearized mathematical model shows that some control lever parameters are related to a stability criterion. By simulation, it is confirmed that the proper selected control parameters can suppress the human hunting phenomena.
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paper_title: Identification of intrinsic and reflexive components of human arm dynamics during postural control

paper_content:

Abstract In this study a new methodology to quantify reflexive feedback gains from the mechanical behavior of the human arm during posture maintenance is proposed. Disturbance experiments were carried out on human subjects using continuous random force inputs. The task instruction was ‘minimize displacements’, prescribing a maximum performance task. For the separation of intrinsic and reflexive components, system identification in the frequency domain is applied. From the time records of position and force, frequency response functions (FRFs) are estimated. Given a model structure and an appropriate estimate of the intrinsic component, an estimate of the reflex gains for length and velocity are obtained from the FRFs. The feedback gains vary considerably with the frequency content of the disturbance signal. The results show that reflexive dynamics are substantial for narrow-band and especially low-frequency input signals. It is likely that high reflex gains are most effective for low-frequency inputs ( 1.5 Hz). It is concluded that this new methodology can offer interesting insights into the ability of the central nervous system to modulate reflexive feedback gains.
---
paper_title: Relating biodynamic feedthrough to neuromuscular admittance

paper_content:

When an operator in a moving vehicle is performing a manual control task, the accelerations to which the operator is subjected can result in unintentional control inputs. This biodynamic feedthrough (BDFT) depends on the properties of the control device and of the control limb. Humans can adjust the dynamics properties of their limbs, effectively changing the limb admittance. Previous studies of BDFT did not consider the effect of this adjustment. This paper describes a model for BDFT and an experiment in a moving base simulator with subjects performing a control task with a side stick. During the experiment the neuromuscular admittance was varied by using different control tasks, each requiring a different neuromuscular setting. The non-parametric results of this experiment show that the level of feedthrough is strongly dependent on both the frequency of the disturbance and the neuromuscular admittance. The results furthermore suggest that a relationship can be established between admittance and biodynamic feedthrough.
---
paper_title: Identification of intrinsic and reflexive components of human arm dynamics during postural control

paper_content:

Abstract In this study a new methodology to quantify reflexive feedback gains from the mechanical behavior of the human arm during posture maintenance is proposed. Disturbance experiments were carried out on human subjects using continuous random force inputs. The task instruction was ‘minimize displacements’, prescribing a maximum performance task. For the separation of intrinsic and reflexive components, system identification in the frequency domain is applied. From the time records of position and force, frequency response functions (FRFs) are estimated. Given a model structure and an appropriate estimate of the intrinsic component, an estimate of the reflex gains for length and velocity are obtained from the FRFs. The feedback gains vary considerably with the frequency content of the disturbance signal. The results show that reflexive dynamics are substantial for narrow-band and especially low-frequency input signals. It is likely that high reflex gains are most effective for low-frequency inputs ( 1.5 Hz). It is concluded that this new methodology can offer interesting insights into the ability of the central nervous system to modulate reflexive feedback gains.
---
paper_title: Identification of intrinsic and reflexive components of human arm dynamics during postural control

paper_content:

Abstract In this study a new methodology to quantify reflexive feedback gains from the mechanical behavior of the human arm during posture maintenance is proposed. Disturbance experiments were carried out on human subjects using continuous random force inputs. The task instruction was ‘minimize displacements’, prescribing a maximum performance task. For the separation of intrinsic and reflexive components, system identification in the frequency domain is applied. From the time records of position and force, frequency response functions (FRFs) are estimated. Given a model structure and an appropriate estimate of the intrinsic component, an estimate of the reflex gains for length and velocity are obtained from the FRFs. The feedback gains vary considerably with the frequency content of the disturbance signal. The results show that reflexive dynamics are substantial for narrow-band and especially low-frequency input signals. It is likely that high reflex gains are most effective for low-frequency inputs ( 1.5 Hz). It is concluded that this new methodology can offer interesting insights into the ability of the central nervous system to modulate reflexive feedback gains.
---
paper_title: Relating biodynamic feedthrough to neuromuscular admittance

paper_content:

When an operator in a moving vehicle is performing a manual control task, the accelerations to which the operator is subjected can result in unintentional control inputs. This biodynamic feedthrough (BDFT) depends on the properties of the control device and of the control limb. Humans can adjust the dynamics properties of their limbs, effectively changing the limb admittance. Previous studies of BDFT did not consider the effect of this adjustment. This paper describes a model for BDFT and an experiment in a moving base simulator with subjects performing a control task with a side stick. During the experiment the neuromuscular admittance was varied by using different control tasks, each requiring a different neuromuscular setting. The non-parametric results of this experiment show that the level of feedthrough is strongly dependent on both the frequency of the disturbance and the neuromuscular admittance. The results furthermore suggest that a relationship can be established between admittance and biodynamic feedthrough.
---
paper_title: Suppression of biodynamic disturbances and pilot-induced oscillations by adaptive filtering

paper_content:

A method for reducing the effects of biodynamic interferences due to whole-body vibrations is described. Manual control tasks are particularly addressed. The method, based on adaptive filtering, enables a substantial attenuation of additive stick involuntary control commands due to pilot body vibrations (stick feedthrough). By means of computer simulations the feasibility of the proposed filtering method is demonstrated for two examples 1) adaptive filtering of biodynamic interferences due to stick feedthrough in manual vehicular control, 2) suppression of pilot-induced oscillations (PIO) due to stick feedthrough. This form of PIO is particularly anticipated for flexible aircraft having a high-gain, stiff stick. It is demonstrated that adaptive filtering is capable of suppressing the biodynamic interferences without substantially affecting the control characteristics of the aircraft/pilot system.
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paper_title: Review of the effects of translational whole-body vibration on continuous manual control performance

paper_content:

A review of the literature concerned with experimental studies of the effects of translational whole-body vibration on continuous manual control performance is presented. Results from studies of the effects of vibration variables (vibration frequency, magnitude, axis, random vibration and multi-axis vibration) are compared. Evidence of the influence of control system variables (physical characteristics of the control, control gain, system dynamics and display variables) is also provided. Studies of the effects of vibration duration on manual control performance are reviewed separately. A behavioural model is presented to summarize the mechanisms (including vibration breakthrough, visual impairment, neuro-muscular interference and central effects) by which whole-body vibration may interfere with the performance of continuous manual control tasks. The model emphasizes the adaptive ability of the human operator.
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paper_title: A rigorous model of reflex function indicates that position and force feedback are flexibly tuned to position and force tasks

paper_content:

This study aims to quantify the separate contributions of muscle force feedback, muscle spindle activity and co-contraction to the performance of voluntary tasks (“reduce the influence of perturbations on maintained force or position”). Most human motion control studies either isolate only one contributor, or assume that relevant reflexive feedback pathways during voluntary disturbance rejection tasks originate mainly from the muscle spindle. Human ankle-control experiments were performed, using three task instructions and three perturbation characteristics to evoke a wide range of responses to force perturbations. During position tasks, subjects (n = 10) resisted the perturbations, becoming more stiff than when being relaxed (i.e., the relax task). During force tasks, subjects were instructed to minimize force changes and actively gave way to imposed forces, thus becoming more compliant than during relax tasks. Subsequently, linear physiological models were fitted to the experimental data. Inhibitory, as well as excitatory force feedback, was needed to account for the full range of measured experimental behaviors. In conclusion, force feedback plays an important role in the studied motion control tasks (excitatory during position tasks and inhibitory during force tasks), implying that spindle-mediated feedback is not the only significant adaptive system that contributes to the maintenance of posture or force.
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paper_title: Suppression of biodynamic disturbances and pilot-induced oscillations by adaptive filtering

paper_content:

A method for reducing the effects of biodynamic interferences due to whole-body vibrations is described. Manual control tasks are particularly addressed. The method, based on adaptive filtering, enables a substantial attenuation of additive stick involuntary control commands due to pilot body vibrations (stick feedthrough). By means of computer simulations the feasibility of the proposed filtering method is demonstrated for two examples 1) adaptive filtering of biodynamic interferences due to stick feedthrough in manual vehicular control, 2) suppression of pilot-induced oscillations (PIO) due to stick feedthrough. This form of PIO is particularly anticipated for flexible aircraft having a high-gain, stiff stick. It is demonstrated that adaptive filtering is capable of suppressing the biodynamic interferences without substantially affecting the control characteristics of the aircraft/pilot system.
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paper_title: Suppressing operator-induced oscillations in manual control systems with movable bases

paper_content:

There are many manual control tasks in which the operator's action is fed back to the input device, usually a joystick, through the operator's body dynamics excited by the base motion. This can lead to instability and reduced performance. This paper proposes a novel approach to the cancellation of such "biodynamic feedthrough". A prototype single-degree-of-freedom task in which the operator uses a force-reflecting joystick to position his/her base is considered here. A model-based approach is used to formulate /spl mu/-synthesis-based controllers that coordinate the motions of the joystick and the base. The solution is obtained by D-K iterations. The resultant controllers are robustly stable with respect to variations in the arm/joystick and biodynamic feedthrough parameters. They also provide a desired level of performance based upon position tracking between the joystick and the base and admittance shaping of the joystick. Experimental studies demonstrate the effectiveness of the proposed methods in the suppression of feedthrough induced oscillations. The approach developed in this paper, with some modifications, can be generalized to teleoperation from movable bases.
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paper_title: CANCELLATION OF FEEDTHROUGH DYNAMICS USING A FORCE-REFLECTING JOYSTICK

paper_content:

This paper reports on a set of theoretical and experimental investigations into the use of force reflection to enhance the dynamic behavior of human piloted vehicles, especially joystickcontrolled vehicles such as fly-by-wire jets, bulldozers, and powered wheelchairs. Briefly, force reflection is used in the manual controls to cancel the effects of feedthrough dynamics. Feedthrough dynamics refers to generation of inadvertent steering or speed command inputs due to the action of inertia forces between the pilot’s hand and manual controls. These inertia forces arise in the pilot’s body in response to vehicle accelerations. To eliminate feedthrough dynamics, a canceling force is produced on the force-reflecting joystick using a model of the pilot dynamics and the known vehicle accelerations. A custom motion platform and a commercial force-reflecting joystick are used in a set of experiments to test the idea. Parameter values for an assumed model are estimated by observing the response of the pilot’s body to known platform accelerations. Cancellation of feedthrough dynamics is demonstrated for a human subject.
---
paper_title: Identification of intrinsic and reflexive components of human arm dynamics during postural control

paper_content:

Abstract In this study a new methodology to quantify reflexive feedback gains from the mechanical behavior of the human arm during posture maintenance is proposed. Disturbance experiments were carried out on human subjects using continuous random force inputs. The task instruction was ‘minimize displacements’, prescribing a maximum performance task. For the separation of intrinsic and reflexive components, system identification in the frequency domain is applied. From the time records of position and force, frequency response functions (FRFs) are estimated. Given a model structure and an appropriate estimate of the intrinsic component, an estimate of the reflex gains for length and velocity are obtained from the FRFs. The feedback gains vary considerably with the frequency content of the disturbance signal. The results show that reflexive dynamics are substantial for narrow-band and especially low-frequency input signals. It is likely that high reflex gains are most effective for low-frequency inputs ( 1.5 Hz). It is concluded that this new methodology can offer interesting insights into the ability of the central nervous system to modulate reflexive feedback gains.
---
paper_title: Suppressing operator-induced oscillations in manual control systems with movable bases

paper_content:

There are many manual control tasks in which the operator's action is fed back to the input device, usually a joystick, through the operator's body dynamics excited by the base motion. This can lead to instability and reduced performance. This paper proposes a novel approach to the cancellation of such "biodynamic feedthrough". A prototype single-degree-of-freedom task in which the operator uses a force-reflecting joystick to position his/her base is considered here. A model-based approach is used to formulate /spl mu/-synthesis-based controllers that coordinate the motions of the joystick and the base. The solution is obtained by D-K iterations. The resultant controllers are robustly stable with respect to variations in the arm/joystick and biodynamic feedthrough parameters. They also provide a desired level of performance based upon position tracking between the joystick and the base and admittance shaping of the joystick. Experimental studies demonstrate the effectiveness of the proposed methods in the suppression of feedthrough induced oscillations. The approach developed in this paper, with some modifications, can be generalized to teleoperation from movable bases.
---
paper_title: Identification of intrinsic and reflexive components of human arm dynamics during postural control

paper_content:

Abstract In this study a new methodology to quantify reflexive feedback gains from the mechanical behavior of the human arm during posture maintenance is proposed. Disturbance experiments were carried out on human subjects using continuous random force inputs. The task instruction was ‘minimize displacements’, prescribing a maximum performance task. For the separation of intrinsic and reflexive components, system identification in the frequency domain is applied. From the time records of position and force, frequency response functions (FRFs) are estimated. Given a model structure and an appropriate estimate of the intrinsic component, an estimate of the reflex gains for length and velocity are obtained from the FRFs. The feedback gains vary considerably with the frequency content of the disturbance signal. The results show that reflexive dynamics are substantial for narrow-band and especially low-frequency input signals. It is likely that high reflex gains are most effective for low-frequency inputs ( 1.5 Hz). It is concluded that this new methodology can offer interesting insights into the ability of the central nervous system to modulate reflexive feedback gains.
---
paper_title: Relating biodynamic feedthrough to neuromuscular admittance

paper_content:

When an operator in a moving vehicle is performing a manual control task, the accelerations to which the operator is subjected can result in unintentional control inputs. This biodynamic feedthrough (BDFT) depends on the properties of the control device and of the control limb. Humans can adjust the dynamics properties of their limbs, effectively changing the limb admittance. Previous studies of BDFT did not consider the effect of this adjustment. This paper describes a model for BDFT and an experiment in a moving base simulator with subjects performing a control task with a side stick. During the experiment the neuromuscular admittance was varied by using different control tasks, each requiring a different neuromuscular setting. The non-parametric results of this experiment show that the level of feedthrough is strongly dependent on both the frequency of the disturbance and the neuromuscular admittance. The results furthermore suggest that a relationship can be established between admittance and biodynamic feedthrough.
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Title: A Review of Biodynamic Feedthrough Mitigation Techniques

Section 1: INTRODUCTION
Description 1: Introduce the concept of biodynamic feedthrough (BDFT) and outline the goals and structure of the paper.

Section 2: THE BIODYNAMIC FEEDTHROUGH SYSTEM
Description 2: Describe the general biodynamic feedthrough system, its components, and how BDFT occurs.

Section 3: Minimizing platform accelerations (#1)
Description 3: Discuss the approach of minimizing platform accelerations to reduce BDFT and its implications.

Section 4: PLF-HO interface design (#2)
Description 4: Explore the design of the interface between the platform and human operator to mitigate BDFT, including seat damping and isolation techniques.

Section 5: Neuromuscular adaptation (#3)
Description 5: Describe how neuromuscular adaptation can mitigate BDFT, with examples and its pros and cons.

Section 6: HO-CD interface design (#4)
Description 6: Discuss the design of the interface between the human and the control device to reduce BDFT, such as using arm rests and other supporting measures.

Section 7: Control device design (#5)
Description 7: Explain how the design of control devices can reduce BDFT, including reducing responsiveness and misalignment of axes.

Section 8: Signal filtering (#6)
Description 8: Discuss the use of signal filtering to mitigate BDFT, including static and adaptive filtering techniques.

Section 9: Model-based cancellation (#7)
Description 9: Describe the model-based cancellation approach to mitigate BDFT, including force cancellation and signal cancellation methods.

Section 10: CONCLUSIONS
Description 10: Summarize the findings on BDFT mitigation techniques and discuss the most promising solutions.