A MEMS torsional resonant magnetometer for the attitude determination in space

We present a MEMS torsional resonance magnetometer based on Lorentz force, which consists of torsional structures, torsional beams, metal plates, a coil, and a glass substrate. The Lorentz force, introduced by the interaction of a current in the MEMS coil and an external horizontal magnetic field, leading to the displacement of the torsional structure, which can be detected by two sensing capacitors according to the differential change. Based on the comparison between the test and the simulation of the fabricated chip, a novel structure of folded torsional beam and double-layer excitation coil is introduced. To increase the sensitivity and the quality of the sensor, the step-height is decreased and a CMP process is employed. The improved MEMS processes, including fabrication, scribing, pressure welding and packaging, are accomplished after the optimization of the structure parameters. Also we analyzed the influences of the beam shape, the damping hole size, the coil turns and the double-layer coils on the sensor's performances. The prototype's performances including sensitivity, repeatability, resonant frequency and quality factor are tested in the low pressure environment. The results indicate that this micro magnetometer can meet the requirements of the attitude determination and control system employed in spacecrafts.