Improvement of Low-Speed Precision Control of a Butterfly-Shaped Linear Ultrasonic Motor

Abstract

The control performance of a butterfly-shaped linear ultrasonic motor is not good when the target speed is less than 1 mm/s by traditional methods. To improve low-speed controlling characteristics of linear ultrasonic motor, a closed-loop control strategy by using both the step control and the fuzzy PID control was proposed. The controller was constructed with the function of providing a closed-loop control of the speed by adjusting the driving voltage amplitude in stepping driving mode. The corresponding step controlling parameters were determined by experiments. Comprehensive experiments on the developed control strategy were conducted under different target speeds. There was a maximum of 24.5% speed error at the target speed of 10 μm/s, meanwhile, the coefficient of variation and the response time were 16.3% and 0.11 s, respectively. With the triangular or sinusoidal waves speed tracking curves at amplitude of 1 mm/s, the maximum speed tracking error were 0.1 mm/s and 0.15 mm/s respectively. Thus, a good speed tracking performance was obtained. These results support the functional ability and potential of the proposed method as a low-speed precision control method for linear ultrasonic motors. INDEX TERMS linear ultrasonic motor, step control, fuzzy PID control, low speed NOMENCLATURE Coefficient of variation Maximum speed error of the platform Speed error of the platform Change of speed error of the platform Proportional coefficient of the PID controller Initial value of proportional coefficient Change of proportional coefficient Integral coefficient of the PID controller Initial value of integral coefficient Change of integral coefficient Differential coefficient of the PID controller Initial value of differential coefficient Change of differential coefficient Number of driving waves of the driving signal Set speed of the platform Coefficient of determination Driving period of the driving signal Average speed of the platform Actual position of the platform Actual speed of the platform Standard deviation of the platform speed

Research on Low-Speed Driving Model of Ultrasonic Motor Based on Beat Traveling Wave Theory

“…As shown in Figure 27b, the beating wave period obtained from the vibration measurement experiment is t q = 0.19 ms, which is close to the calculation result of Equation (15). It verifies the correctness of the theory that, when standing waves of different frequencies and amplitudes are applied to the two phases of the motor, the beating traveling wave will be generated on the stator surface.…”

“…According to Equation ( 15), the period of the beat wave is as follows: According to the experimental measurement, the vibration frequency of the stator tooth particle point (point M in Figure 24), before the outage time point, t o f f , is the driving frequency, ω q (45 kHz), while after the outage time point t o f f , the envelope of the longitudinal velocity and amplitude of the particle point is displayed as a beat wave contour. According to Equation (15), the period of the beat wave is as follows:…”

“…Therefore, the ability of the ultrasonic motor to work at an ultralow speed becomes the prerequisite to replacing the electromagnetic motor and to accurately adjusting the attitude of the satellite. To achieve this goal, some scholars have proposed a microstepping driving method to control the ultrasonic motor [14][15][16][17][18]. Omura et al [14] realized the low-speed control of the traveling wave ultrasonic motor by adjusting the voltage and phase.…”

“…Omura et al [14] realized the low-speed control of the traveling wave ultrasonic motor by adjusting the voltage and phase. Shi et al [15] selected the driving voltage of the motor as the control variable and adopted a fuzzy PID control to adjust it in real time to realize the low-speed control of the linear motor. Senjyu et al [16] adopted the motor speed control method, combining frequency conversion speed regulation and DC power PWM control to achieve the highest efficiency speed regulation control.…”

Iterative Learning‐Based PID Precision Control for Sports Performance Analysis

“…In different applications, due to the different control purposes, the controller's choice of performance indicators is often different [17,18]. Different control parameters are formulated for different performance indexes, which is of great significance in practical applications.…”