Robust controller design for a variable displacement hydraulic motor

Presents the robust control of a variable displacement hydraulic motor (VDHM). A feedback control structure consisting of two nested loops is employed. The inner feedback loop controls the position of the rocker arm which actuates the wobbler plate of the motor. The outer feedback loop regulates the motor shaft velocity such that shaft speed is guaranteed at steady state despite external torque loads. The control loops are closed in succession closing the inner loop first. For each loop design, step response data is collected from a VDHM laboratory test stand to generate analytical systems level models. Based on these models, feedback controllers are designed using classical loop shaping techniques. Feedback control, as opposed to feedforward control, maintains motor shaft velocity under nonpredictive torque loading conditions. In addition, the feedback structure eliminates the need for extensive system calibration when considering system parameter changes that result from component aging