A nonlinear disturbance observer for two link robotic manipulators

A nonlinear disturbance observer for two link robotic manipulators is derived in the paper. The global exponential stability of the proposed disturbance observer is guaranteed by selecting design parameters which depend on the maximum velocity and the physical parameters of robotic manipulators. This observer overcomes the disadvantages of existing disturbance observers which are designed or analysed by linear system techniques. It can be applied in robotic manipulators for various purposes such as friction compensation, independent joint control, torque sensorless control and fault diagnosis. The performance of the proposed observer is demonstrated by friction estimation and compensation.