State-space speed control of two-mass mechanical systems: Analytical tuning and experimental evaluation

This paper proposes a model-based two-degree-of-freedom (2DOF) state-space speed controller design for a two-mass mechanical system. Analytical tuning rules for a feedback gain, the reduced-order state observer, full-order state observer, and prefilter are derived. The proposed design rules enable the automatic tuning of the controller if the mechanical parameters are known. The prefilter is designed for step, ramp, and parabolic command tracking. The effects of the time delay, measurement noise, and parameter variations on controller tuning and control performance are studied by means of Nyquist diagrams, noise transfer functions, and time-domain simulations. It is shown that the full-order-observer-based controller is a preferable choice, particularly if the feedback loop is delayed and noisy. The proposed controller design is experimentally evaluated using two 4-kW servo motors coupled with a toothed belt; good reference tracking for step and dynamic commands, as well as robust and fast load-torque rejection, is demonstrated.