In this paper, we propose a novel three-ring capacitive angular position sensor with an absolute zero position feature based on microelectromechanical system (MEMS) technology. The sensor utilizes an inner absolute zero position detection ring to provide easily analyzable zero position information within a 15° angular range. The sensor also incorporates an outer precise angular position detection ring to offer high-precision measurements. The excitation-coupling electrode ring provides a carrier signal and enables noncontact measurement between the stator and the rotor. To validate the design, we fabricated a sensor with a sensing structure outer diameter of 21.3 mm and a thickness of less than 1 mm, and we then tested the sensor with a traveling wave micromotor rotating platform. Experimental results show that the sensor achieved an angular resolution of 0.003° and an online detection accuracy of 0.029° for angular position. The abrupt change in the voltage amplitude caused by the absolute zero position feature exhibited good repeatability and periodicity, and this feature helped the micromotor successfully achieve zero self-calibration with a precision of 0.73°. Our results validate the practicality of the absolute zero position and break through the bottleneck of current MEMS-based capacitive angular position sensors that can only detect angular increments.

The piezoelectric thin-film traveling-wave micro-motor based on the microelectromechanical systems (MEMS) process has the advantages of compact size, easy integration and batch production. However, the piezoelectric thin-film micro-motor still exits a serious shortcoming of very small output torque. This paper proposes a novel lead zirconate titanate (PZT) piezoelectric thin-film motor with stator teeth to improve the output torque. Firstly, theoretical analysis and finite element simulations were performed to determine the design parameters of the stator teeth. The device preparation is completed by combining with wafer-scale MEMS fabrication techniques, in which the base Si layer of PZT-SOI wafer is thinned and etched to form the stator tooth structure based on the deep reactive ion etching (DRIE) process. Finally, the performance testing results showed that the novel motor achieved a large output torque of 39.4 $\mu$ N $\cdot$ m under a low driving voltage of 4.5 Vpp. The large output torque is 2.65 times higher than that of the previously reported piezoelectric thin-film motor with a much higher driving voltage of 11 Vpp. 2023-0099

Piezoelectric traveling wave microactuator based on micro-electromechanical systems (MEMS) technology has the advantages of miniaturization and easy to integrate. However, the lack of angle sensing function limits their application in aspect of microstructural rotation closed-loop control. Here, we present a self-sensing piezoelectric traveling wave microactuator. By integrating the capacitive encoder with the microactuator, high-precision step angle rotation can be achieved, facilitating rotation closed-loop control of various MEMS microstructures. The prototype size of the self-sensing microactuator is 5mm×5mm. The angle detection accuracy and the resolution can reach up to 0.06° and 0.01°, respectively, which ensure the microacutor complete adaptive angle adjustments. This work is expected to pave a new way for in-situ calibration of inertial sensors, micro robot movement, control of optical devices, and light path manipulation.

This study proposes a high-resolution rotation-measuring system for miniaturized MEMS ultrasonic motors using tunneling magnetoresistance (TMR) sensors for the first time. Initially, the architecture and principle of the rotation-measuring system are described in detail. Then, the finite element simulation is implemented to determine the miniaturized permanent magnet’s residual magnetization, dimensions, and TMR sensor position. Finally, the experiments are implemented to evaluate the performance. Using calibration based on a high-precision servo motor, it is found that the relationship between the output and rotational angle is highly linear and immune to the rotor’s out-of-plane movement. Meanwhile, the angle-detecting resolution is higher than 0.1°. After the calibration, the continuous rotation of the MEMS ultrasonic motor is tested. It is found that the angle testing result varies with a period close to 360°, which indicates that the rotation-measuring system has successfully detected the motor’s rotation.