Interpolating across the impedance/admittance spectrum with Unified Interaction Control

Abstract

Impedance Control (IC) and Admittance control (AC) are two control methods for robot-environment interaction which have opposing performance and stability characteristics. Previous research has proposed that the two controllers define a spectrum of controllers. This paper quantifies the IC/AC spectrum as a trade-off between the suppression of force sensor error and modelling error. Unified Interaction Control (UIC) is introduced, which can interpolate across this spectrum of controllers by using a periodic state-reset and an inner-loop gain weighting parameter. The UIC is verified through simulation, experiment, and an eigenvalue analysis. Interpolating across the spectrum allows one to choose an ideal controller given the nature of the robot and environment. This is demonstrated in two case studies: adapting the level of interpolation to optimize performance with a changing environment, and using a static level of interpolation to mitigate the worst-case effects in both IC and AC.