REAL-TIME IMPLEMENTATION OF AN INDIRECT ADAPTIVE ROBOT CONTROLLER

Adaptive controllers applied to high-speed and high-precision robot ma nipulators give excellent tracking performances because they take into account the full dynamics of the robot. Recent publications have show n that on-line estimation of the dynamic constant parameters can be ob tained by the joint tracking error (direct adaptive control) or by the torque prediction error (indirect adaptive control). In direct adapti ve controllers the estimation law is derived from Lyapunov stability o r Popov hyperstability methods. These controllers are simple and their real-time implementation is easy; however, the estimation is not so a ccurate. In indirect adaptive controllers the estimation law is based on a least squares algorithm. These controllers give accurate estimate s of the manipulator parameters; however, they involve much more compu tation than the direct approach. Therefore no real-time implementation s of indirect adaptive tracking controllers for robots have been repor ted in the literature until now. This paper describes a real-time impl ementation of an indirect adaptive scheme applied to a two-degree-of-f reedom (2DOF) direct-drive SCARA robot. The controller is implemented at low cost by the use of a single-chip digital signal processor (DSP) .