Issues in Robot Adaptive Control

This paper compares several adaptive control algorithms which have been proposed for robotic manipulators. The methods which are investigated are the indirect method of adaptive control, and two versions of direct adaptive control. The direct adaptive control methods which are investigated are those proposed by Craig, Hsu and Sastry [3] and Slotine and Li [16]. The paper derives the adaptation laws and highlights the differences in the derivations. Each method has been simulated on the same trajectories and the performance is evaluated based on the tracking accuracy, the trajectory error dynamics and on the parameter estimation. Both persistently and non-persistently exciting trajectories are examined. In the case of indirect adaptive control, a regression vector reduction algorithm is proposed to guarantee identifiability of the parameters.