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研究生:鄭立誠
研究生(外文):Li-Chen Cheng
論文名稱:壓電換能器之主動減振控制
論文名稱(外文):Active Damping Control of Piezoelectric Transducers
指導教授:陳秋麟陳秋麟引用關係
口試委員:劉昌煥林志隆吳文中羅有綱李昆銘邱煌仁
口試日期:2015-06-12
學位類別:博士
校院名稱:國立臺灣大學
系所名稱:電子工程學研究所
學門:工程學門
學類:電資工程學類
論文種類:學術論文
論文出版年:2015
畢業學年度:103
語文別:英文
論文頁數:116
中文關鍵詞:壓電換能器主動減振控制共振頻率追蹤電流驅動轉換器雙向能量傳送。
外文關鍵詞:Piezoelectric transduceractive damping controlresonant frequency trackingcurrent-fed converterbi-directional energy transferring.
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本論文提出一主動減振控制方案,其適用於車用距離偵測系統之壓電換能器。近年來車用電子領域已日益受到重視。壓電換能器為此領域中一種重要的感測器,其利用超音波來偵測車輛周遭的物體以避免可能發生的碰撞。但是壓電換能器的偵測範圍會受到其本身機械振盪衰減速度的限制,故本論文希望藉由引入主動減振控制來提升此感測器振動的衰減速度。
發送超音波的過程包含了對壓電換能器的驅動以及減振。壓電換能器的最佳操作頻率可根據驅動電路的操作由其共振頻率來決定。此外,由於壓電換能器通常具有極高的頻率選擇性且其特性容易因環境變化而改變,使得要持續有效操作壓電換能器在同一頻率有所困難。因此壓電換能器在進行操作前需先行追蹤其共振頻率。
為了實踐所提出的主動減振控制方案,在本論文中製作了數個驅動電路。第一個電路使用方波電壓來驅動壓電換能器以追蹤其串聯共振頻率。第二個電路則是藉由偵測其可達到零電壓切換的頻率區間來追蹤並聯共振頻率。最後主動減振控制被實現於第三個電路中。透過實驗結果可知,藉由使用主動減振控制,壓電換能器振動衰減速率的理論時間常數可由368.86 μs 改善為117.37 μs。


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.


口試委員會審定書 #
誌謝 I
摘要 II
ABSTRACT III
TABLE OF CONTENTS V
LIST OF FIGURES IX
LIST OF TABLES XIV
Chapter 1 Introduction 1
1.1 Background 1
1.2 Ultrasonic Distance Measurement System 2
1.3 Motivations and Objectives 4
1.4 Dissertation Organization 8
Chapter 2 Piezoelectric Transducer 9
2.1 Piezoelectricity 9
2.2 Equivalent Circuit 11
2.3 Resonance Frequencies 13
2.4 Applications in an Ultrasonic Measurement System 16
Chapter 3 Conventional Damping Control 19
3.1 Passive Damping 19
3.2 Active Damping 21
3.2.1 Synchronized Switch damping on Inductor (SSDI) 22
3.2.2 Synchronized Electrical Charge Extraction (SECE) 27
Chapter 4 Theoretical Analysis on Driving Methods 31
4.1 Driving with an Ideal AC Source 31
4.1.1 Ideal Sinusoidal Voltage Waveform 31
4.1.2 Ideal Sinusoidal Current Waveform 33
4.2 Driving with a Switching Power Supply 34
4.3 Harmonic Currents of the Pulse Waveform Driving 35
4.3.1 Pulse Current Waveform 36
4.3.2 Pulse Voltage Waveform 37
Chapter 5 Resonance-Frequency-Tracking Circuit for Low-Coupling-Coefficient Piezoelectric Transducers 39
5.1 Input Capacitance Compensation with Square Voltage Waveform 39
5.2 Circuit Implementation 42
5.2.1 Half-Bridge Inverter Configuration 42
5.2.2 Current Direction Sensing Circuit 43
5.3 Operation Principles 45
5.3.1 Key Waveforms 45
5.3.2 Tracking Strategy 45
5.4 Experimental Results 48
5.5 Summary 54
Chapter 6 Resonance-Frequency-Tracking Method for Current-Fed Piezoelectric Transducers 55
6.1 Resonance-Frequency Detection with Zero-Voltage-Switch Technique 55
6.1.1 Input Pulse Current and Mechanical Current 57
6.1.2 Boundary Condition of Achieving Zero-Voltage-Switch 58
6.1.3 Ideal Zero-Voltage-Switch Frequency Range 60
6.1.4 Comparison with Conventional Detecting Method 61
6.2 Circuit Implementation 63
6.2.1 Current-fed Inverter Topology 63
6.2.2 Configuration of Diodes 64
6.3 Operation Principles 66
6.3.1 Key Waveforms 66
6.3.2 Tracking Strategy 69
6.3.3 Power Losses Analysis 72
6.4 Experimental Results 73
6.5 Summary 81
Chapter 7 Realization of Active Damping Control 83
7.1 Analysis on the Proposed Active Damping Control Approach 83
7.1.1 Operation with Pulse Currents at Resonant Frequency 83
7.1.2 Effectiveness of the Proposed Active Damping Control 85
7.1.3 Phase Deviation of Active Damping Control 88
7.2 Bi-directional Flyback Converter Topology 88
7.3 Operation Principles 90
7.3.1 Driving Operation 91
7.3.2 Active Damping Operation 92
7.3.3 Determination of Operating Frequency 95
7.4 Experimental Results 96
7.5 Summary 104
Chapter 8 Conclusions and Future Work 106
8.1 Dissertation Conclusions 106
8.2 Future Work 108
Reference 109

LIST OF FIGURES

Fig. 1.1 Configuration of an ultrasonic distance measurement system. 3
Fig. 1.2 Voltage waveform of a piezoelectric transducer as a transceiver in distance measurement system. 5
Fig. 2.1 Piezoelectric Effect. (a) Simple molecule model. (b) Molecule with pressure. (c) Material with pressure. 10
Fig. 2.2 Reverse piezoelectric effect. 11
Fig. 2.3 Equivalent circuit of a PT. (a) Original simple version. (b) Reflected
version. 12
Fig. 2.4 Different vibration modes. 13
Fig. 2.5 Equivalent circuit with different resonant modes. 13
Fig. 2.6 Bode plot of the PT. 14
Fig. 2.7 Circle of (a) impedance. (b) admittance. 15
Fig. 2.8 Structure of a PT. 16
Fig. 2.9 Configuration of a PT as (a) a transmitter. (b) a receiver. 17
Fig. 3.1 Configuration of PT. (a) Open-circuit. (b) Short-circuit. 20
Fig. 3.2 Configurations of (a) serial-SSHI. (b) parallel-SSHI. 23
Fig. 3.3 Ideal waveform of (a) serial-SSHI. (b) parallel-SSHI. 24
Fig. 3.4 Configuration of SSDI. 26
Fig. 3.5 Ideal waveform of SSDI. 26
Fig 3.6 Different configurations of SECE. (a) Flyback converter. (b) Switch with an inductor. (c) Discharge through the short-circuited path. 28
Fig. 3.7 Operating waveforms of SECE. 29
Fig. 4.1 PT with a sinusoidal driving source. 32
Fig. 4.2 Pulse waveform. 36
Fig. 5.1 Driving waveforms at fs when Vin is (a) a sine wave. (b) a square wave. 40
Fig. 5.2 Ideal relationship between Vin and Im at (a) f < fs. (b) f > fs. 41
Fig. 5.3 Configuration of the proposed circuit. 42
Fig. 5.4 Configuration of current flowing direction sensing circuit. 43
Fig. 5.5 Parasitic components configuration. 44
Fig. 5.6 Key waveforms at (a) f < fs. (b) f > fs. 46
Fig. 5.7 Tracking flowchart. 47
Fig. 5.8 Prototype of the implemented circuit. (a) PT. (b) half-bridge inverter.
(c) current sensing circuit. 48
Fig. 5.9 Waveforms for f < fs. 50
Fig. 5.10 Waveforms for f > fs. 51
Fig. 5.11 Resonant frequency tracked waveforms. 52
Fig. 5.12 Waveforms of the tracked frequencies: (a) 57.86 kHz (b) 58.03 kHz. 53
Fig. 6.1 Driving process of ZVS. 56
Fig. 6.2 Phase difference between Iin and Im. (a) fn = 1. (b) fn < 1. (c) fn > 1. 59
Fig. 6.3 Upper bound frequency versus quality factor and normalized current. 61
Fig. 6.4 Contour maps of characteristics of a PT. 62
Fig. 6.5 Topology of current-fed full-bridge inverter with the PT. 63
Fig. 6.6 Energy transfer in resonant tanks. 64
Fig. 6.7 Different configurations for blocking the reverse current. (a) Two diodes.
(b) One diode. 65
Fig. 6.8 Key waveforms for proposed current-fed full-bridge inverter at fn = 1. 67
Fig. 6.9 Key waveforms at (a) fn < 1. (b) fn > 1. 67
Fig. 6.10 Operations in intervals (a) t0-t1. (b) t1-tu1. (c) tu1-t2. 69
Fig. 6.10 Operations in intervals (d) t2-t3. (e) t2a-t3. 70
Fig. 6.11 Tracking flowchart for microcontroller (MCU). 71
Fig. 6.12 Samples of PTs. 73
Fig. 6.13 Prototype of the proposed circuit and experimental setup. (a) Proposed transmitting circuit. (b) The PT as a transmitter. (c) The PT as a receiver. 74
Fig. 6.14 Measured waveforms at frequency detected for tmag = 2 μs. 76
Fig. 6.15 Receiving signal waveform. 77
Fig. 6.16 Resonant frequency tracking waveforms. 77
Fig. 6.17 Measured waveforms for different operating frequencies. (a) Lower than the ZVS region. (b) Higher than the ZVS region. 79
Fig. 6.18 Experimental results of operating frequency versus receiving voltage with different additional capacitances. 80
Fig. 7.1 The PT applied active damping control. (a) Configuration. (b) Ideal waveforms. 85
Fig. 7.2 Topology of the bi-directional flyback converter with the PT. 89
Fig. 7.3 Key waveforms in driving operation. 90
Fig. 7.4 Key waveforms in active damping operation. 91
Fig. 7.5 Driving operation in interval (a) ta0-ta1. (b) ta1-ta2. (c) ta2-ta3. (d) ta3-ta4. 93
Fig. 7.6 Active damping operation in interval (a) tb0-tb1. (b) tb1-tb2. (c) tb2-tb3.
(d) tb3- tb4. 94
Fig. 7.7 Prototype of the implemented circuit. 97
Fig. 7.8 Measured waveforms in driving operation. 98
Fig. 7.9 Measured waveforms in active damping operation. 99
Fig. 7.10 (a) Waveforms in transmitting operation with active damping. (b) Enlarged waveform of VPT. 100

Fig. 7.11 (a) Waveforms in transmitting operation without active damping.
(b) Enlarged waveform of VPT. 101
Fig. 7.12 Measured amplitude of VPT with active damping control. 103

LIST OF TABLES

Table 5.1 Specification of the PT 49
Table 5.2 Part Number of the Components 49
Table 6.1 Specification of PTs 75
Table 6.2 Ideal Specification for Transmitting Circuit 75
Table 6.3 Parameters of PTs with Different Additional Capacitances 80
Table 7.1 Specification of PT 97


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