Variable structure control for variable pump controlling variable motor

Variable structure control for variable pump controlling variable motor (VPCVM) systems based on feedback linearization was presented to overcome the defects, such as huge overflow losses, slow speed regulating and poor full capacity utilization, arisen from the conventional independent control of variable pump or variable motor in the systems. The mathematical model of VPCVM was established, and the multiplicative nonlinear property existing in the system caused trouble for the motor speed controlling. To improve the VPCVM performance, the VPCVM nonlinear model was transformed into a linear system by feedback linearization. For the closed hydraulic speed controlling system with double-variable, the variable pump displacement can be deduced from motor expected speed and variable motor displacement. The variable structure controller was designed to control variable motor speed and its stability was proved according to Lyapunov theory. Simulations show that our approach has the capacity for speeding up system response and reducing overshoot of VPCVM system, and features with robust performance.