Exact observer for flexible joint robots

This paper deals with a problem of state observation of robot manipulators having elastic joints. The authors treat the case when one assumes that the global outputs of the system are link positions and their time derivatives (velocities). The authors propose an exact nonlinear observer based on some properties of the robot and on the known theory of linear observers. This observer reconstructs exponentially all the robot variables. The dynamic behavior of the observation algorithm is illustrated by simulation tests on a two revolute elastic joints robot manipulator