Time Invariant Motion Controller for Physical Human Robot Interaction

2019 ◽  
Author(s):  
Juan D. Muñoz Osorio ◽  
Felipe Castañeda ◽  
Felix Allmendinger ◽  
Uwe E. Zimmermann
Keyword(s):  
Impedance Control ◽  
Maximum Velocity ◽  
Breast Cancer Diagnosis ◽  
Human Robot Interaction ◽  
Control Law ◽  
Ultrasound Scanning ◽  
Motion Controller ◽  
Robot Interaction ◽  
Human Disturbances ◽  
Time Invariant

Abstract In this paper, a new method to perform time-invariant motion is proposed. The approach uses the advantages of variable impedance control to have full interactivity with the human while tracing a desired path. The path is followed at maximum velocity while the human can disturb the robot at any instant and manipulate it far from the desired path without changing the control law. The method was proven in simulation and on a real torque-controlled serial manipulator (KUKA LWR iiwa). The chosen paths were designed to perform robotic assisted ultrasound scanning for breast cancer diagnosis. Results show that interactivity is allowed while keeping a low kinetic energy of the robot. Despite of human disturbances, the robot can keep tracing the path after the interaction is finished.

scholarly journals A Human-Robot Cooperative and Personalized Compliant Joint Controller for Upper-Limb Rehabilitation Robots: The Elbow Joint Validation

2021 ◽  
Author(s):  
Stefano Dalla Gasperina ◽  
Valeria Longatelli ◽  
Francesco Braghin ◽  
Alessandra Laura Giulia Pedrocchi ◽  
Marta Gandolla
Keyword(s):  
Upper Limb ◽  
Human Robot Interaction ◽  
Control Law ◽  
Robot Interaction ◽  
Activation Patterns ◽  
Upper Limb Rehabilitation ◽  
Control Framework ◽  
High Level ◽  
Limb Rehabilitation ◽  
Muscular Activation

Abstract Background: Appropriate training modalities for post-stroke upper-limb rehabilitation are key features for effective recovery after the acute event. This work presents a novel human-robot cooperative control framework that promotes compliant motion and renders different high-level human-robot interaction rehabilitation modalities under a unified low-level control scheme. Methods: The presented control law is based on a loadcell-based impedance controller provided with positive-feedback compensation terms for disturbances rejection and dynamics compensation. We developed an elbow flexion-extension experimental setup, and we conducted experiments to evaluate the controller performances. Seven high-level modalities, characterized by different levels of (i) impedance-based corrective assistance, (ii) weight counterbalance assistance, and (iii) resistance, have been defined and tested with 14 healthy volunteers.Results: The unified controller demonstrated suitability to promote good transparency and render compliant and high-impedance behavior at the joint. Superficial electromyography results showed different muscular activation patterns according to the rehabilitation modalities. Results suggested to avoid weight counterbalance assistance, since it could induce different motor relearning with respect to purely impedance-based corrective strategies. Conclusion: We proved that the proposed control framework could implement different physical human-robot interaction modalities and promote the assist-as-needed paradigm, helping the user to accomplish the task, while maintaining physiological muscular activation patterns. Future insights involve the extension to multiple degrees of freedom robots and the investigation of an adaptation control law that makes the controller learn and adapt in a therapist-like manner.

Impedance control of a cable-driven SEA with mixed H2/H∞ synthesis

2017 ◽  
Vol 37 (3) ◽  
pp. 296-303 ◽  
Author(s):  
Ningbo Yu ◽  
Wulin Zou
Keyword(s):  
Control Strategy ◽  
Control Method ◽  
Impedance Control ◽  
Low Frequency ◽  
Human Robot Interaction ◽  
Control Input ◽  
Robot Interaction ◽  
Content Type ◽  
Series Elastic Actuator ◽  
Series Elastic

Purpose This paper aims to present an impedance control method with mixed H2/H∞ synthesis and relaxed passivity for a cable-driven series elastic actuator to be applied for physical human–robot interaction. Design/methodology/approach To shape the system’s impedance to match a desired dynamic model, the impedance control problem was reformulated into an impedance matching structure. The desired competing performance requirements as well as constraints from the physical system can be characterized with weighting functions for respective signals. Considering the frequency properties of human movements, the passivity constraint for stable human–robot interaction, which is required on the entire frequency spectrum and may bring conservative solutions, has been relaxed in such a way that it only restrains the low frequency band. Thus, impedance control became a mixed H2/H∞ synthesis problem, and a dynamic output feedback controller can be obtained. Findings The proposed impedance control strategy has been tested for various desired impedance with both simulation and experiments on the cable-driven series elastic actuator platform. The actual interaction torque tracked well the desired torque within the desired norm bounds, and the control input was regulated below the motor velocity limit. The closed loop system can guarantee relaxed passivity at low frequency. Both simulation and experimental results have validated the feasibility and efficacy of the proposed method. Originality/value This impedance control strategy with mixed H2/H∞ synthesis and relaxed passivity provides a novel, effective and less conservative method for physical human–robot interaction control.

scholarly journals Human-Robot Interaction and Demonstration Learning Mode Based on Electromyogram Signal and Variable Impedance Control

2018 ◽  
Vol 2018 ◽  
pp. 1-11
Author(s):  
Rui Wu ◽  
He Zhang ◽  
Tao Peng ◽  
Le Fu ◽  
Jie Zhao
Keyword(s):  
Impedance Control ◽  
Gain Scheduling ◽  
Human Robot Interaction ◽  
Physical Interaction ◽  
Learning From Demonstration ◽  
Robot Interaction ◽  
End Effector ◽  
Demonstration Experiment ◽  
2D Space ◽  
Control Interaction

In this research, properties of variable admittance controller and variable impedance controller were simulated by MATLAB firstly, which reflected the good performance of these two controllers under trajectory tracking and physical interaction. Secondly, a new mode of learning from demonstration (LfD) that conforms to human intuitive and has good interaction performances was developed by combining the electromyogram (EMG) signals and variable impedance (admittance) controller in dragging demonstration. In this learning by demonstration mode, demonstrators not only can interact with manipulator intuitively, but also can transmit end-effector trajectories and impedance gain scheduling to the manipulator for learning. A dragging demonstration experiment in 2D space was carried out with such learning mode. Experimental results revealed that the designed human-robot interaction and demonstration mode is conducive to demonstrators to control interaction performance of manipulator directly, which improves accuracy and time efficiency of the demonstration task. Moreover, the trajectory and impedance gain scheduling could be retained for the next learning process in the autonomous compliant operations of manipulator.

Model reference adaptive impedance control for physical human-robot interaction

2016 ◽  
Vol 14 (1) ◽  
pp. 68-82 ◽  
Author(s):  
Bakur Alqaudi ◽  
Hamidreza Modares ◽  
Isura Ranatunga ◽  
Shaikh M. Tousif ◽  
Frank L. Lewis ◽  
...  
Keyword(s):  
Impedance Control ◽  
Human Robot Interaction ◽  
Robot Interaction ◽  
Model Reference ◽  
Adaptive Impedance Control ◽  
Model Reference Adaptive

A Robust Impedance Controller for Improved Safety in Human-Robot Interaction

2021 ◽  
Author(s):  
Curt Laubscher ◽  
Jerzy T. Sawicki
Keyword(s):  
Impedance Control ◽  
Inequality Constraint ◽  
Human Robot Interaction ◽  
Control Signal ◽  
Tracking Performance ◽  
Continuous Control ◽  
Control Parameters ◽  
Normal Operating Condition ◽  
Robot Interaction ◽  
Bounded Disturbances

Abstract This paper presents a novel impedance controller modified with a switching strategy for the purpose of improving safety in human-robot interactions. Under normal operating condition, an impedance controller is enabled when adequate tracking performance is maintained in the presence of bounded disturbances. However, if disturbances are greater than anticipated such that tracking performance is degraded, the proposed controller temporarily switches modes to a control strategy better apt to limit control inputs. With disturbances returning to the prescribed bounds, tracking performance will restored and the impedance controller will resume for nominal operation. The control parameters are constrained by a few conditions necessary for smooth operation. First, a pair of equality constraints is required for the control signal to be continuous when switching control modes. Second, a Lyapunov analysis is performed to formulate an equality constraint on the control parameters to ensure only a single switch occurs when changing control modes to avert control chatter. Third, a matrix inequality constraint is necessary to ensure a robust positive invariant set is formed for when impedance control is active. Numerical simulations are provided to illustrate the controller and conditions. The simulation results successfully validate the presented theory, demonstrating how the constraints yield a continuous control signal, eliminate switching chatter, and permit robustness to disturbances.

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