Trajectory Tracking Controller for flexible robot arm

The most important benefits of flexible link manipulator include high payload-to-arm weight ratio. The reduction of weight leads to increase of the link elasticity that significantly complicates the control of the manipulator. The difficulty in control is caused by the fact that the link model is a distributed parameter plant. In this case, several elastic modes are required to achieve sufficiently high accuracy. Plus, the plant has several uncertain parameters (payload mass, hub and structural damping factors, etc.) that influence the systems performance. In this paper, Trajectory Tracking Controller is suggested by utilizing the hybrid controller approach to overcome the problem of vibration of tip position through motion which is a characteristic of the flexible link system. A modified version of the proportional-derivative rigid controller to track the hub position while sliding mode control was used for vibration damping. Also, a second controller (a fuzzy logic based proportional integral plus derivative control scheme was developed for both vibration damping and trajectory tracking. Results are illustrated in the robust performance of the proposed tip position tracking controllers over the payload variation. A good performance is obtained for the trajectory tracking. The stability of these controllers is also proved.