Supervisory Control for a Switched Mode Hydraulic Transformer

A supervisory control for a hydraulic transformer is developed. The hydraulic transformer being controlled is configured in a traditional manner where a pair of hydraulic pump/motors are mechanically coupled together. This transformer can be configured in three distinct modes depending on how each port is connected. A supervisory control determines, for the desired output pressure and output flow, the mode and shaft speed that the transformer should operate in order to minimize the power loss. The resulting controller structure ensures that the transformer provides the desired flow while following the desired mode and shaft speed. The supervisory control is further modified to avoid high frequency switching and to achieve bumpless transfer between modes. Experimental results demonstrate the efficacy of the supervisory controller to increase the efficiency of the hydraulic transformer driven system.