Stability analysis for feedforward approximations in the control of flexible joint robots

For the case of a controller composed of a model-dependent feedforward and a model-independent feedback for flexible joint robots, a stability analysis for different types of feedforward is presented. For feedforwards which differ in the amount of required model information and state measurements, and from the knowledge of a Lyapunov function for a specific choice of the feedforward, it is possible to deduce the type of stability, local exponential or Lagrange, of the other forms of feedforward without explicitly searching for new Lyapunov functions. These results, together with the asymptotic (global) stabilization results constitute a step in the control of flexible joint robots