Development Of Converter For Driving Piezoelectric Bimorph For Flapping-wing Small Air Vehicles

The flapping-wing aircraft is an unmanned aerial vehicle(UAV)that imitate the flight of birds or insects.It has the vast applied foreground in both military and civilian fields.The flapping-wing aircraft consists of a body,a wing,an actuator,a driver,a drive circuit,and a lithium polymer battery.At present,micro-motors have been used as drive devices to create bionic"insect aircrafts".As a low power application,it is essential for flapping-wing small air vehicles to have a driver with good performance and a drive circuit with high efficiency and power density.In this paper,high-performance piezoelectric bimorph driver is used as a drive device to develop a high-efficiency drive circuit for a small flapping-wing UAV.The main work is as follows:1.Equivalent circuit model and drive schemes of piezoelectric bimorph driver.Firstly,the equivalent circuit model of the piezoelectric bimorph material was studied,and the piezoelectric bimorph material samples were modeled.Secondly,the drive requirements and schemes of the piezoelectric actuator are introduced,and the most reasonable drive scheme is selected according to the structure of the bimorph.2.Overall structure design and control strategy of the drive circuit.Using the“simultaneous drive”method,a RCD passive snubber flyback DC/DC step-up converter cascaded with a bi-directional active half-bridge drive stage is designed.The flyback converter is controlled by PWM under the condition of DCM to ensure the stability of the output high voltage.The half-bridge drive stage takes the approach that comparing the output voltage signal with an ideal waveform lookup table to generate pulses to control the high and the low side switches.The drive stage is able to generate arbitrary unipolar signals that drive the piezoelectric bimorph materials.3.Optimization and simulation of the drive circuit.Firstly,the PID optimization control simulation is performed on the DC/DC flyback boost circuit to avoid the voltage fluctuation caused by the energy loss and oscillation of the equivalent load and ensure the stability of the output.Secondly,through overall simulation of the circuit,the waveforms of the boost-flyback and drive stage are obtained.By comparing with the theoretical waveforms,the feasibility of the principle is verified.4.System verification and experimentation for drive circuit.According to a reasonable selection of devices,a drive circuit PCB having a weight of 586mg,a size of 169(13×13)mm~2,a maximum output power of 500mW,and a maximum conversion efficiency of 64.5%was fabricated.The output waveforms of the circuit were verified by an oscilloscope.The energy efficiency experiment of the flyback converter under different circuit parameters was carried out and the optimization results were obtained.Finally,a piezoelectric bimorph material driving experiment was performed to observe the displacement generated by the driver.The actual test results are basically consistent with the theoretical analysis,which is able to confirm the feasibility and practicality of the design.