Control Strategy for the Discharge Phase of an Ultra-High Voltage (>7kV) Bi-Directional Flyback Converter Driving Capacitive Actuators

Dielectric Elastomer Actuators (DEAs) require ultra high voltages in the order of several kilo volts to operate. To supply such voltages, a DC-DC flyback converter topology was selected. One of the main advantage of using such a structure is the possibility to modify it to work bidirectionally. Meaning that electrical energy can not only flow from the power supply to the actuator, but also from the actuator back to the power supply. This characteristic is of significant importance because of the need to recuperate the electrical energy stored in DEAs to improve the overall efficiency of the system instead of dissipating it as heat. Indeed, due to their capacitive nature, DEAs can store an important amount of energy when fully deformed which needs to be removed to bring the actuator back to its original shape. This paper focuses on the control aspect to remove the stored energy when using a bi-directional flyback converter capable to supply a voltage of up to 7 kV to the load from a 12V power supply. After a brief presentation of the working principle of the discharge procedure, the implemented control strategy is detailed in depth with the presentation of the hardware used and the control algorithm put in place. Experimental results then show that the control strategy works well with an output voltage of up to 7 kV but is nonetheless close to its limits because of increasingly small measuring time spans going down to several micro seconds.