Abstract
Model of ultrasonic motor is the foundation of the design of ultrasonic motor′s speed and position controller. A two‐input and one‐output dynamic Takagi‐Sugeno model of ultrasonic motor driving system is worked out using fuzzy reasoning modeling method in this paper. Many fuzzy reasoning modeling methods are sensitive to the initial values and easy to fall into local minimum, and have a large amount of calculation. In order to overcome these defects, equalized universe method is used in this paper to get clusters centers and obtain fuzzy clustering membership functions, and then, the unknown parameters of the conclusions of fuzzy rules are identified using least‐square method. Different experimental data that are tested with different operational conditions are used to examine the validity of the fuzzy model. Comparison between experimental data and calculated data of the model indicates that the model can well describe the nonlinear characteristics among the frequency, amplitude of driving voltage and rotating speed. The proposed fuzzy model can be used to analyze the performance of ultrasonic motor driving system, and also can be used to design the speed and position controller of ultrasonic motor.
Highlights
The model of ultrasonic motor system is the foundation of analyzing ultrasonic motor’s performance and is an important premise of designing motor controller and trying to improve the control performance
From the viewpoint of the driving circuit, the ultrasonic motor is a kind of capacitive load
The controllable variables that can be used for rotating speed control are the amplitude of driving voltage, frequency, and phase difference of the two-phase voltages
Summary
The model of ultrasonic motor system is the foundation of analyzing ultrasonic motor’s performance and is an important premise of designing motor controller and trying to improve the control performance. Because of the nonlinear and time-varying operation of piezoelectric material and friction, the strong nonlinear characteristics and complex coupling relations of ultrasonic motor are brought out by the complicated energy conversion processes and nonlinearity of material [2]. Because of these reasons, the accurate theoretical model of ultrasonic motor is difficult to obtain. Phase difference is used as the controlled variable in [15], and a kind of fuzzy Hammerstein model is worked out This model is made up of steady nonlinear part and dynamic linear transfer function. The two-input and one-output Takagi-Sugeno model of ultrasonic motor system is established, and the model can well show the nonlinear dynamic relationship among the amplitude of driving voltage, frequency, and rotating speed
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