Dejan Vasic

Small power step-up converter for driving flapping wings of the micro robotic insects

The main purpose of this study is to design the power electronics to drive a 1 W piezoelectric actuator for micro-robotic applications, such as flapping-wing robotic insects. The voltage requirement of the piezoelectric actuators is about 200 V, but most of the energy sources do not exceed 5 V. In this paper, we propose a two stages converter suitable to drive this kind of actuators. The first stage of the proposed converter is a DC/DC converter which can have lightweight and high voltage gain for the biasing of the piezoelectric actuator. The second stage of the proposed converter is a DC/AC converter which is capable of producing an arbitrary unipolar AC voltage to supply the piezoelectric actuator. Because the switching loss is frequently the dominant loss in high-voltage/low-power switching amplifiers, a wideband zero-voltage-switching (ZVS) half-bridge circuit is introduced. In our design, two auxiliary shunt circuits are connected to the input terminal in order to ensure the ZVS condition in a wide bandwidth. Each auxiliary shunt circuit includes a diode, a switch and an inductor. The auxiliary inductor exhibits a small inductance and is not in the path of the major power flow, thus it can be implemented by the parasitic inductance of the connection wires or by PCB tracks.

Modeling of a multi-electrodes traveling-wave piezoelectric transformer

This paper proposes a compact electromechanical modeling of multi-electrode piezoelectric transformer. This modeling can be applied to the study of standing or traveling flexural wave in piezoelectric systems and especially for ring type piezoelectric transformers. This modelling is based on the Euler-Bernoulli beam theory and from this theory and piezoelectric equations, transfer matrixes linking stresses, velocities and voltages for a beam are determined. In piezoelectric systems with no mechanical boundary in the propagation direction of the wave, for example a ring, an admittance matrix is obtained from the modeling linking all the currents and voltages. This modelling allows moreover the representation and electrical simulation of a piezoelectric element subjected to a traveling wave.

Comparison of bistable magnetic non-linear piezoelectric energy harvester with traditional linear technique

In this paper, a piezoelectric energy harvesting device with bistable non-linear vibration combined with a switching-type interface (SSHI) are compared to the traditional linear technique. The voltage switching techniques are used to increase the output power of energy harvesting devices for low-coupled structures. However, these devices are efficient only at the resonance. The bistable non-linear technique can broaden the available bandwidth. We used the power flow and work-cycles to simplify the analysis of the non-linear vibration with switching techniques. Numerical simulations of the equivalent circuit of bistable device are shown. Finally, experimental results presented for the SSHI circuit combined with the bistable technique show more energy can be harvested and larger bandwith.

Comparison of Piezoelectric Structural Damping Based on Velocity Controlled Switching and Pulse Width Modulation Switching Circuits

Two novel piezoelectric damping techniques (VSD and PWMD) are compared in this paper to the traditional resonant shunt damping technique and SSDV technique. In VSD, the switching shunt circuit turns ON or OFF according to the polarity of the vibration velocity of the host structure to shift the piezoelectric voltage phase. An external voltage source is connected to enlarge the voltage amplitude across the piezoelectric element and to optimize the dissipated power. The PWM shunt technique not only can decrease the audible noises more efficiently but also ensure the stability of the control system with a constant voltage source. The theoretical and the experimental results show that the piezoelectric voltage can be adaptive to the vibration displacement by the pulse widths variation, so the PWMD can stay in stable state with a constant voltage source and can still provide a very good performance.Copyright