Trajectory Tracking Control Using a Hydraulic Transformer

Throttling loss of a hydraulic system is a major contributor to the low system efficiency. Hydraulic transformers can potentially be used as an energy efficient, throttle-less control approach for multi-actuators systems powered by a common pressure rail (CPR). The transformer transforms the input CPR pressure to the desired pressure of the actuator instead of throttling it. Regenerative energy can also be captured. This paper presents a trajectory tracking controller for a hydraulic actuator driven by a transformer consisting of two mechanically coupled variable displacement pump/motors. In addition to controlling the motion of the actuator, the transformer speed is also controlled. The control method can be adapted for all 3 hydraulic transformer configurations that differ by port connections. Simulation results show the validity of the proposed control strategy and that transformer with an appropriate control strategy can significantly reduce energy use relative to throttling valve. It is also shown that optimizing transformer configuration for bucking or boosting, and optimizing the transformer speed can further improve efficiency.