Improving the transient performance in robotics force control using nonlinear damping

Robotics force control is increasingly being used in the manufacturing industry, to perform surface polishing, deburring, parts mating etc. However, to avoid the high impact force which could damage the workpiece, a common strategy is to command the robot to approach the workpiece slowly, which increases the overall cycle time. In this paper, we propose a nonlinear damping control scheme which reduces the force overshoot without compromising on the dynamic response. The controller design and the parameter tuning are relatively straightforward because of the clear physical meanings of the parameters. Finally, the effectiveness of the proposed controller is verified through simulation studies.

I. Introduction

In recent years, industrial robots are increasingly being used to perform operations which require a contact between the robot (tool) and the workpiece, such as surface polishing, deburring and part mating [1], [2], in contrast to their “more traditional” tasks of spray painting or arc welding which require little or no contact at all. To ensure the success of the afore-mentioned contact-type operations, robotics force control is crucial because it not only prevents excessive contact force which could damage the workpiece, but also regulates the machining force to obtain a consistent surface quality or smoothened edge across the whole workpiece.