Study of stability variations in reaction torque observer based force controllers

Abstract

An effective method for determining the environmental impedance is to use a reaction torque observer (RTOB), which is a variant of the disturbance observer (DOB) concept. A robust yet accurate force controller can be developed by implementing both RTOB and DOB. This study examines the potential instability of force controllers based on RTOB. Traditionally, a RTOB-based force controller is examined under the presumption that the two cut-off frequencies for DOB and RTOB should always be equal to one another. But in some circumstances, it fails to maintain stability. The stability of the system is determined by the interactions between the mechanical, environmental, and controller dynamics, which also add to design constraints. There has not been any analysis of unstable scenarios in terms of system dynamics. In this paper, a novel stability constraint is derived as a result of the new stability assessment approach that is proposed. A new stability guideline is also suggested. The simulation results are used to confirm the validity of the proposals.