PROJECTION METHOD FOR HYDRAULIC PISTON MOTOR TORQUE CONTROL

Hydraulic systems are mostly known for their high-power density and their ability to precisely modulate the ratio of the power transmission between a prime mover and other actuators. This power modulation is generally achieved by controlling the displacement of the pump/motors implemented in the hydraulic system. Several component architectures and/or control strategies have been developed in this sense, as described in [1]. However, for hydrostatic transmissions, beyond the displacement control, a precise and efficient torque control of hydraulic motors is often preferable in order to optimize the driveability and/or the energy consumption. This constitutes a major technological problem, which could be addressed step-by-step by simplifying the architecture of the hydraulic motor studied and dividing the control in elementary bricks. The paper presents an application of this early torque control strategy to a three-piston hydraulic motor. A simplified model of such a motor leads to a state-space representation, which is then transformed using specific change of variables that enable a direct torque control. Both torque and internal dynamics are then splitted in two different submodels that facilitate the motor torque control. Simulation results illustrate the potential of this approach before concluding.