An observer design for constrained robot systems

An asymptotic observer is constructed for constrained robot systems. Since a constrained robot, in general, involves a set of differential equations and a set of algebraic equations, both differential and algebraic variables must be estimated. This gives rise to difficulty in estimating the algebraic variables which are the contact forces. The difficulty is eased by introducing the reduced model of constrained systems developed by N.H. McClamroch and D. Wang (1988). By using this model, the observer design is similar to that for an unconstrained nonlinear system. Thus both the contact force and the motion of the robot can be directly estimated