Velocity field control and adaptive virtual plant disturbance compensation for planar contour following tasks

In contour following applications, contour error reduction is a subject of much concern. In order to attenuate the influence of modelling uncertainty and external disturbance so that satisfactory contouring accuracy can be achieved, this article develops an integrated motion control scheme that consists of a pre-defined velocity field, a velocity field controller and the proposed Adaptive Virtual Plant Disturbance Compensation (AVPDC) scheme. First, a velocity field is constructed for a free-form curve and its associated controller is also developed. Moreover, to improve the contouring accuracy, this article proposes an AVPDC to compensate for the uncertainties because of the inaccurate modelling and external disturbances. The main advantage of the proposed AVPDC is that the compensator gains can be adaptively adjusted according to the current state error. Subsequently, in order to investigate the stability of the proposed AVPDC, a Lyapunov-based analysis is performed. Finally, a free-form contour following experiment is conducted to verify the effectiveness of the proposed approach. Experimental results show that the proposed approach exhibits satisfactory performance.