A theoretical and experimental investigation of position based force and impedance control for industrial robots

In this paper we present the experimental results of the real time performance of basic force and impedance control algorithms. The control design is based on linear system modelling and analysis such that the closed loop system meets basic design requirements. Additionally, in the impedance control, the aim is to achieve a specific target impedance. The experiments show the performance of both compliant control concepts in performing a relatively simple contact task with a conventional industrial robot. The impacts of target impedance on contact stability and force transient and steady-state behaviours are also investigated. Our initial experiments have proven the theoretical analysis based on the linearised industrial robot and environment models. However, it is also shown that several nonlinearities inherent in real robotic systems, such as Coulomb friction and control quantisations, can jeopardise the performance of position-based force and impedance control causing limit-cycles.