tailieunhanh - AUTOMATION & CONTROL - Theory and Practice Part 6

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 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 . 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 .