This article presents a structure-compacted single-gimbal control moment gyroscope, which is directly driven by an ultrasonic motor. The momentum wheel and the ultrasonic motor are designed and optimized based on software simulation. Considering the gyroscope's dynamic disturbance and the nonlinearities of the ultrasonic motor, an expert control algorithm combining a two-degree-of-freedom pole placement controller with a pattern reasoning controller is designed for the gimbal servo system. The presented controller realizes a wide-range closed-loop speed control of the gimbal from 0.2 mrad/s to 1.6 rad/s, which is the base of the high stability and high precision of the control moment gyroscope. The presented control moment gyroscope and its controller board are manufactured and assembled for experiments. The experimental results show that the momentum wheel has almost no impact on the gimbal servo system at high speeds, but with the decrease in the gimbal speed the impact increases gradually.
A dynamic beam shaping system requires a variable beam expander. Three optical lenses form the core of the proposed beam expander, and two hollow ultrasonic motors are used to adjust the positions of two of the lenses. A polymer-based stator is introduced in the ultrasonic motors to decrease their weight, whereupon a prototype is machined and its performance is assessed. The beam expander starts and stops within 0.05 s, and the minimum positioning error is 0.03 µm by adjusting the motor speed. The presented expander can continuously expand a laser beam by between threefold and fivefold, and nanoscale positioning and high-precision beam shaping are realized by using ultrasonic motors as its actuators.
The rotor deformation of an ultrasonic motor is an important factor affecting its performance. However, little research focuses on the relationship between the rotor deformation and motor performance. This paper provides an approach to improve the ultrasonic motor's output properties by changing the rotor's size from the view of proper rotor deformation and better stress distribution on the interface. First, a thin shell structure is introduced to study the deformation of the rotor. A finite element model of the motor is built in COMSOL Multiphysics software for the contact analysis of the stress distribution. Then, the optimized ranges of parameters are determined by simulation. Frictional experiments are conducted to verify the feasibility of the rotor under the optimized size. Finally, the performance experiments of a stator corresponding to different sizes of rotor are carried out. The experimental results show that the speed, the power and the efficiency of the optimized rotor are all increase. These results prove the effectivity of the new approach to improving the performance of the ultrasonic motor.
With the advantages of high accuracy and fast response, piezoelectric actuators are used to drive optical image stabilizers. As a piezoelectric stack is not tensile, preload voltage is required for a traditional piezoelectric driven optical image stabilizer, which wastes electricity and adversely affects the stack’s performance. In this paper, we propose a double gimbal optical image stabilizer, whereupon a prototype is machined and its performance is assessed. Two piezoelectric stacks are used to produce the forward and reverse actuation, respectively, in which case the preload voltage is not essential. Owing to the isolation of the gimbal, the output coupling of the two piezoelectric actuators is less than 1%. The presented stabilizer has the actuation range of ±50 µm and effectively tracks the sinusoidal signals with the frequency below 46 Hz.
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