Robust controller design via μ-synthesis for high-performance micromachined tunneling accelerometers

This paper presents a μ-synthesis based, robust controller design for high-performance micromachined accelerometers based on electron tunneling. These accelerometers are intended for underwater acoustics applications, and are required to feature submicro-g resolution at frequencies between 5 Hz and 1 kHz, and must be packaged in an 8 cm³ volume with a total mass of 8 grams. An important characteristic of the tunneling transducer is that the tunneling current only occurs when the electrodes are separated by a gap of order 10 Å. A controller is designed to maintain the 10 Å tunneling gap to a very high degree of accuracy over the wide signal bandwidth for a very lightly-damped and highly flexible proof mass in the accelerometer. The even more challenging aspect is that this controller must be robust for accelerometers with parametric variations from sensor to sensor, as is common for micro-electromechanical systems