Experimental H∞ control of a single flexible link with a shoulder joint

In this paper, H_∞ control of a single flexible link with a shoulder joint is discussed. The cross-section of the flexible link is such that only horizontal vibrations are possible. Simulations were performed using a simplified model. An H_∞ controller was designed that provides a fast step response with low overshoot, but inadequate disturbance rejection. Experiments were performed using a five-bar robot with one side joint locked. Using linear transfer functions obtained via system identification for several beam inclinations, an H_∞ controller was found that has a good step response with the exception of large overshoot. Trajectory tracking is also shown. The performance is compared to that of a conventional PID controller