Adaptive Control of a Manipulator When the Mass of the Load is Unknown

Abstract In this paper an adaptive controller for a robotic manipulator is presented. In the control system, the computed torque technique is used to linearize and decouple the dynamic model. The computed torque technique requires the complete dynamic model to be known. Normally, this model is known except maybe for a few parameters, e.g. load inertia and center of gravity and friction co-efficients. In this paper, the unknown parameters, which all represent physical quantities, are estimated with a recursive prediction error method. The most recent parameter estimate is then used in the computed torque technique. The control system is applied to the positioning part of an industrial robot in a simulation experiment where the unknown parameter is the mass of the load. The controller performs well, and the mass of the load can even be estimated when the manipulator is accelerating and the control deviation is large.