Active Impedance Control of Bioinspired Motion Robotic Manipulators: An Overview

Abstract

There are two main categories of force control schemes: hybrid position-force control and impedance control. However, the former does not take into account the dynamic interaction between the robot's end effector and the environment. In contrast, impedance control includes regulation and stabilization of robot motion by creating a mathematical relationship between the interaction forces and the reference trajectories. It involves an energetic pair of a flow and an effort, instead of controlling a single position or a force. A mass-spring-damper impedance filter is generally used for safe interaction purposes. Tuning the parameters of the impedance filter is important and, if an unsuitable strategy is used, this can lead to unstable contact. Humans, however, have exceptionally effective control systems with advanced biological actuators. An individual can manipulate muscle stiffness to comply with the interaction forces. Accordingly, the parameters of the impedance filter should be time varying rather than value constant in order to match human behavior during interaction tasks. Therefore, this paper presents an overview of impedance control strategies including standard and extended control schemes. Standard controllers cover impedance and admittance architectures. Extended control schemes include admittance control with force tracking, variable impedance control, and impedance control of flexible joints. The categories of impedance control and their features and limitations are well introduced. Attention is paid to variable impedance control while considering the possible control schemes, the performance, stability, and the integration of constant compliant elements with the host robot.

Hybrid Impedance-Admittance Control for Upper Limb Exoskeleton Using Electromyography

“…The impedance and admittance controls are opposed in concept. The former aims to prevent the environment from disturbing the trajectory, whereas the latter aims to allow interaction [22,30].…”

“…The impedance control establishes a dynamic relationship between the interaction force and the position error, correcting the robot's position errors by increasing the force exerted [22]. This control is defined by (1)…”

“…Among these techniques, we can highlight the impedance and admittance controls, which perform position control through the forces/torques applied to the mechanical structure. At the impedance level, the actuator reacts to the environment, changes its position, and corrects the error generated by the interaction with the environment [22]. Admittance control acts in favor of this change of position, facilitating the user's interaction with the robotic structure.…”

FAT-based adaptive backstepping control of an electromechanical system with an unknown input coefficient

“…Different loop configurations are possible, see Sec. 5 of [2] for more details. However, feedback gains for cascade control should be tuned carefully to get high motion performance with ensured stability [3][4][5].…”

Impact Behavior of a Rotating Rigid Body with Impact and Viscous Friction

“…Using the computer controlled wheelchair people with special needs can be supported also by a robotic arm picking up objects, turning on or off switches, opening or closing doors, making tea, and pulling drawers [42]. Taking into account the particularities of such applications, it is necessary to take into account the mechanical impact when designing robotic structures.…”