Sliding observers for robot manipulators

Abstract High precision measurements of the joint displacements are available on robot manipulators. By contrast, the velocity measurements obtained through tachometers are in many cases contaminated by noise. It is therefore economically and technically interesting to investigate the possibility of accurately estimating the speed from available measurements. This paper presents a new approach for estimating the state vector of a robot manipulator, using nonlinear sliding mode observers. Robot models with and without friction are analysed. In both cases, convergence conditions for the observed state vector are given. The results are strongly based on the physical properties of the robot, such as energy conservation and the quadratic nature of the Coriolis and centripetal forces.