A Vertically Supported Ring-Type MEMS Gyroscope Utilizing Electromagnetic Actuation and Sensing C. N. Yeh, J. J. Tsai, R. J. Shieh, F. G. Tseng, C. J. Li, and Y. C. Su Abstract – In this paper, we present the design and fabrication of a ring-type MEMS gyroscope, which is composed of a soft polymer-structure and 8 separate driving and sensing coils. The bottom side of the ring structure is mounted, while the upper portion vibrated freely by the actuation of electromagnetic and inertial forces. For the prototype demonstration, a polymer molding, metal printing, and multilayer packaging process is developed. Realized by the highly flexible structure, the device is expected to greatly amplify the vibratory motion and therefore the resulting output signal. As such, the proposed device could be low cost and readily serve as a motion detector for a variety of applications. I. INTRODUCTION Gyroscopes, which measure the rate and angle of rotation, have a wide range of applications in many fields, such as military, automotive, leisure, and robotics. The applications of traditional gyroscopes are limited, mainly due to its structural complexity, high cost, and bearing- wear problems. Because of their great potential for wide- spread application, MEMS gyroscopes have received great attention in recent years [1-5]. Among the various types of MEMS gyroscopes, almost all of them are vibratory ones, which use vibrating structures (instead of complicated spinning and lubricated assemblies) to sense rotation. For the driving and sensing of vibration, electrostatic and piezoelectric forces are widely utilized to actuate the structures, while the variations in measured capacitance and piezoresistance are commonly employed to monitor the motion. It seems that silicon-based MEMS gyroscopes are advantageous, for example, they can be batch- processed with IC fab technology while their sizes and costs could be reduced significantly. However, there might be some remaining problems related to the fabrication of MEMS gyroscopes. In order to improve their sensitivity, many devices employ narrow gaps, 3D structures, or vacuum packaging, which make the fabrication process complicated, high cost, and usually low yield. In this paper, we present a novel ring-type MEMS gyroscope, which utilize electromagnetic forces to drive a soft polymer structure and sense its rotation by monitoring the variation in induced electro-motive forces. The device is easy to fabricate and expected to amplify the induced vibration and therefore the resulting output signal. As such, the proposed device could be low cost and readily serve as a motion detector for a variety of applications. Fig. 1. Schematic illustration of the gyroscope. Fig. 2. Operating scheme of the gyroscope. II. OPERATING PRINCIPLE A vibratory gyroscope takes advantage of the Coriolis effect to measure the angular motion of an object. It consists of a proof mass and a pair of driving and sensing elements. The proof mass is forced to harmonically vibrate by the driving element. When the mass is subjected to rotation, the induced Coriolis force would cause the mass to vibrate along the sensing direction. One can obtain the angular velocity by detecting the vibration in the sensing direction. Figure 1 is a schematic illustration of the proposed MEMS gyroscope, which is composed of a soft ring- structure and 8 separate driving and sensing coils C. N. Yeh, F. G. Tseng and Y. C. Su are with the National Tsing Hua University, J. J. Tsai and R. J. Shieh are with the Chung-Shan Institute of Science and Technology, and C. J. Li is with the National Kaohsiung First University of Science and Technology, all in Taiwan. Contact author: Y. C. Su, 101, Sec. 2 Kuang-Fu Rd., Hsinchu, Taiwan, Email: ycsu@ess.nthu.edu.tw