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AUTOMATION & CONTROL - Theory and Practice Part 6
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Tham khảo tài liệu 'automation & control - theory and practice part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 116 AUTOMATION CONTROL - Theory and Practice transformation from the Nyquist hodograph from the frequency domain to a parameter model - the transfer function of the transducer s impedance is presented. In the third paragraph a second parameter estimation method is based on an automatic measurement of piezoelectric transducer impedance using a deterministic convergence scheme with a gradient method with continuous adjustment. In the end the chapter provides a method for frequency control at ultrasonic high power piezoelectric transducers using a feedback control systems based on the first derivative of the movement current. 2. Ultrasonic piezoelectric transducers 2.1 Constructive and functional characteristics The ultrasonic piezoelectric transducers are made in a large domain of power from ten to thousand watts in a frequency range of 20 kHz - 2 MHz. Example of characteristics of some commercial transducers are given in Tab. 1. Transducer type P W fs KHz fp KHz m Kg I mA Constr. type C0 nF TGUS 100-020-2 100 20 1 22 2 0 65 300 2 4 2 0 6 TGUS 100-025-2 100 25 1 27 2 0 6 300 2 4 2 0 6 TGUS 150-040-1 150 40 2 43 2 0 26 300 1 2 4 1 0 6 TGUS 500-020-1 500 20 1 22 2 1 1 500 1 5 8 0 6 Table 1. Characteristics of some piezoelectric transducers made at I.F.T.M. Bucharest The 1st type is for general applications and the 2nd type is for ultrasonic cleaning to be mounted on membranes. Two examples of piezoelectric transducers TGUS 150-040-1 and TGUS 500-25-1 are presented in Fig. 1. Fig. 1. Piezoelectric transducer of 150 W at 40 kHz left and 500 W at 20 kHz right They have small losses a good coupling coefficient kef a good quality mechanical coefficient Qm0 and a high efficiency q0 Methods for parameter estimation and frequency control of piezoelectric transducers 117 Q n fp 1 - 2 Itg Qm0 10 1 f f Qm0 1 in normal operating conditions of temperature humidity and atmospheric pressure. 3. Electrical characteristics The high power ultrasonic installations have as components .