Design and Implementation of Plastic Deformation Behavior by Cartesian Impedance Control Based on Maxwell Model

Jie Zhao,Le Fu

doi:10.1155/2018/6752752

Abstract

Compliance has become one prerequisite of robots designed to work in complex operation environment where dynamic and uncertain physical contact or impact takes place frequently and even intentionally. Impedance control is a typical complaint control methodology. Standard impedance control is based on dynamics described by a spring and damper model connected in parallel way, which endues the robot an elastic behavior. In contrast, plastic deformation can be realized by Maxwell model in which spring and damper connect in series. In this study, a novel Cartesian impedance controller is constructed based on the Maxwell model. Implementation in a robot manipulator is executed to validate and analyze the proposed control law. A plastic deformation behavior of the robot manipulator is produced and certain extent compliance is achieved under the unpredictable impact or contact force exerted by human or other environment objects.

Highlights

A rapid increase in the opportunity of robots’ physical interaction with complex environment, including humans, other robots, and operational objects has occurred because of the tendency that robots break through the confined spaces and structured environments
A plastic deformation behavior of the robot manipulator is produced and certain extent compliance is achieved under the unpredictable impact or contact force exerted by human or other environment objects
A novel Cartesian impedance controller based on Maxwell model is designed and implemented practically in a robot manipulator platform

Summary

Introduction

A rapid increase in the opportunity of robots’ physical interaction with complex environment, including humans, other robots, and operational objects has occurred because of the tendency that robots break through the confined spaces and structured environments. A DMPbased framework for robot learning and generalization of humanlike variable impedance skills is formulated in [16] These impedance control methods mentioned above are based on a kind of viscoelastic model [17] which is called Voigt model that connects a spring and damper in parallel way. A shock absorber is constructed by a spring-based passive elastic body and a damping controlled joint connected in series This 2-DOF robot receives the impact of a rolling down object without repelling it, which is called plastic behavior. We propose a Cartesian impedance control scheme based on Maxwell model and implement it in a scenario where unknown contact between robot and other objects exists. A Cartesian impedance control law based on Maxwell model for multiple links robotic arms is proposed to achieve a plastic deformation behavior. Attached video (available here) is given as a demonstration of our work

Comparison of Two Models

Modeling

Controller Design

Experiments

Conclusions