Active Damping Control of Piezoelectric Transducers
Date Issued
2015
Date
2015
Author(s)
Cheng, Li-Chen
Abstract
This dissertation proposes an active damping control method for the piezoelectric transducer in a distance measurement system of a vehicle. In recent years, automotive electronics have become more and more popular and important. Among the devices of automotive electronics, the piezoelectric transducer is one of essential sensors. It utilizes ultrasound to detect the objects surrounding a vehicle to prevent possible collision. However, the detectable range of the measurement system with piezoelectric transducer is restricted by the decay rate of its mechanical vibration, and thus the active damping controls are introduced to enhance the decay rate of the vibration. The process of transmitting ultrasound with active damping controls includes driving and damping a piezoelectric transducer. The optimum operating frequency of a piezoelectric transducer should be determined by the resonant frequencies according to the operation of the driving circuit. Moreover, because a piezoelectric transducer is usually highly frequency-dependent, and its characteristics are easily influenced by the variation of environment, it is difficult to continuously operate a piezoelectric transducer efficiently at a constant frequency. Therefore, the resonant frequencies of the piezoelectric transducer should be tracked before the transmitting process starts. To realize the proposed active damping controls on a piezoelectric transducer, several prototype driving circuits of the piezoelectric transducer were constructed. The first circuit drives the piezoelectric transducer with square-wave voltage to track the serial resonance frequency. As for the second circuit, the frequency at which zero-voltage-switch is achieved is detected to track the parallel resonance frequency. Finally, the active damping control is implemented in the third circuit to transmit ultrasound. The experimental results show that the theoretical time constant of the decay rate is improved from 368.86 μs to 117.37 μs with active damping control.
Subjects
Piezoelectric transducer
active damping control
resonant frequency tracking
current-fed converter
bi-directional energy transferring.
Type
thesis
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