A novel miniature azimuth-level detector based on MEMS

Abstract

Exact knowledge of the attitude is a fundamental factor in steering vehicles. This paper proposes a novel MEMS azimuth-level detector, which is a combination of MEMS accelerometers and MEMS magnetometers, which takes advantage of the solid-state configuration, small size (<62/spl times/40/spl times/14 mm), lightweight (<18 g), high reliability, low power consumption (<300 mW), rapid start-up, and relatively low cost. Using silicon surface micromachining technology, we integrate a dual-axis accelerometer and a single-axis accelerometer rather than a three-axis accelerometer to make up an orthogonal placement. The accelerometers detect the three orthogonal components of the gravity, by which the vehicle tilt including pitch and roll can be derived. Otherwise a dual-axis magnetometer and a single-axis magnetometer, which are also assembled as an orthogonal placement to measure the three components of the Earth's magnetic field, form a compass on the basis of the tilt information. The calculation method of the three attitude angles is introduced. By virtue of adopting an absolute measurement of cosines matrix conversion instead of the conventional relative integral measurement, the system exhibits an excellent long-term performance. However, there are various error sources existing in the measurement, the nonorthogonal assembling error being dominant. We analyze the representative features of this error, establish a mathematical model for it, and successfully compensate this error via arithmetic. The results of testing indicate that our azimuth-level detector can measure the freewill attitude in three-dimensional space, the measurement accuracy has achieved /spl plusmn/0.5(deg) for tilt and /spl plusmn/0.7(deg) for azimuth. It is expected that this novel miniature attitude detector will be adopted in many fields, and is especially favorable for miniature vehicles.