Abstract: This paper changes sliding surface into sliding zone and presents a new velocity observer for robotic track-ing control.This robotic observer is quite different from regular observer and can guarantee that the observa-tion error is uniformly bounded.By means of it,a robust controller is derived.The control accuracy is alsoirrelevant to motion trajectory.This observer based control scheme is easy to implement and robust to robot-ic uncertainty.Experiments have been carried out to illustrate the efficiency of the algorithm.