An experimental validation of a nonlinear velocities observer

High precision measurements of the joint displacement are available to control the robot manipulators. However the signal delivered by sensors velocities are often contaminated by noise and not so useful in contol laws. To overcome this problem velocities observers are used. In this paper we demonstrate experimentaly the applicability of the method. The estimated velocities by the observer are compared with the estimated velocities obtained by numerical derivation of the filtered positions with a F.I.R. The observer used is a nonlinear high gain one based on the notion of uniform observability. As control law we use the linearizing and decoupling computed torque law. The experiencies are conducted on a SCARA robot manipulator built at the laboratory.