Exploiting null space potentials to control arm robots compliantly performing nonlinear tactile tasks

Carina Micheler,Constantin von Deimling,Jan Lang,Nikolas Wilhelm,Rainer Burgkart

doi:10.1177/1729881419885473

Abstract

In this article, two new compliant control architectures are introduced that utilize null space solutions to decouple force and position control. They are capable to interact with uncertain surfaces and environments with varying materials and require fewer parameters to be tuned than the common architectures – hybrid or impedance control. The general concept behind these approaches allows to consider manipulators with six degrees of freedom as redundant by creating a virtual redundancy with a reduced work space. It will be demonstrated that the introduced approaches are superior regarding orthogonal separation of the Cartesian degrees of freedom and avoid inner singularities. To demonstrate their performance, the controllers are tested on a standard industrial robot (Stäubli, RX90B, six degrees of freedom) that actuates two different biomechanically inspired models of the human knee joint.

Highlights

Due to the industrial need of robots performing tactile tasks, extensive research has been conducted on robot– object interaction in the past decades.[1]
Two broad categories of compliant or tactile control strategies deal with this task: hybrid position and force control methods
While the first experiment is designed to investigate the positionprioritized contact control, the second one is concentrated on the evaluation of the multi-force control and its force/ position prioritization

Summary

Introduction

Due to the industrial need of robots performing tactile tasks, extensive research has been conducted on robot– object interaction in the past decades.[1] the key control strategies were established in the 1980s, the improvement of their accuracy, stability and robustness still challenges the robotic community today. Two broad categories of compliant or tactile control strategies deal with this task: hybrid position and force control methods. They divide the Cartesian task in force-regulated and position-controlled degrees of freedom (DOFs)[2] and impedance control methods. The latter relate loads and displacements by a diagonal mass matrix combined with a regular damping and a stiffness matrix.[3]

Objectives

Methods

Results

Conclusion