Sensitivity of task space performance to null space control in presence of model uncertainties

Abstract

This paper investigates the sensitivity of the task space tracking errors to null space tracking errors in the face of model uncertainties for several operational space controllers (OSCs). Under the same inaccurate robot model and digital control effects, experimental data on different OSCs indicated that the sensitivity of task space performance to its null space controller varies for different OSCs based on the way the controllers make use of the inaccurate robot model. Analysis of the error equations of different OSCs reveal several reasons of why some OSCs can give better performance than others. Also from the discussion, it is suggested that the inaccurate model should be used in joint space rather than in task space to avoid magnifying the model uncertainties through the kinematic chain.