A surface micromachined cantilever beam rotation sensor

An innovative, alternative, yet feasible way of angular motion sensing is presented in this dissertation. A novel MEMS surface micromachined non-contact high-speed rotation sensor with total surface area under 4mm2 was developed using the MCNC Multi-User MEMS Process (MUMPs). This dissertation discusses the background, design criteria, and characteristics of this sensor. Six versions of sensor with variations in beam and platform dimensions are designed. Comparisons with existing methods and angular sensing devices are also addressed. A simplified mathematical model of this sensor was built. Responses of the sensors were simulated and predicted to a certain extend under different angular speeds and other physical parameters. Surface roughness and curvature of the sensor platform in both transverse and longitudinal directions due to residual stress induced during the fabrication were measured. Platform lifting experiments were conducted to find out the relation between the change in beam resistance and estimated platform deflection angles. An experimental setup with electric motor, speed controller, power supply, wireless transmitting and receiving circuits, computer interface circuit for data acquisition and storage, and all necessary mechanical components made by rapid prototyping (RP) machine were built. Spinning experiments were conducted to find out the direct effect on receiver frequency due to change in angular speed. Initial results indicate that this piezoresistive sensor is capable of transmitting angular speed data wirelessly at sensitivity around 2Hz/rpm/V with 5V input in the 100 to 6000rpm rotation range. We believe this groundwork will not only give the MEMS community the advantages of using MUMPs-compatible foundry services to design simple, reliable, and batch fabricated high-speed rotation sensors that can be interfaced with commercial wireless chips for signal transmission, but also provide potentially integration with ICs as a single-chip smart rotation sensor solution.