Experiment toward speed-tracking controller designs for planar linkage

In most machine design, planar linkage is often synthesized to achieve a specific trajectory of motion. However, due to kinetic energy stored in the links as they move, large variation in the input torque, particularly at high speed, would be required; thus, severe speed fluctuation caused by this torque variation would be inevitable. Here, two robust controller design schemes are presented to suppress this undesirable fluctuation. In the first design method, nonlinear compensation scheme is proposed to cancel the nonlinear dynamics of the linkage; since the nonlinear compensation is closely related to the generalized inertia (Paul, 1979) of the linkage, procedures to obtain the inertia under vagueness are presented. For the second method, repetitive control based on the internal model principle given by Francis (1975) is applied to the linkage system; it has been known by its usefulness for control systems with periodic reference/disturbance inputs. Experimental studies were performed in a four-bar linkage system to demonstrate the effectiveness of the proposed methods