The signal-processing module, as shown in Fig. 2(B),
consists primarily of three parts: an amplifier, a low-pass filter,
and a analog-to-digital converter. In order to receive a tiny
signal from position sensors, a high performance
instrumentation amplifier (AD620) is used in this system. The
gain of the amplifier is set at 500. A second order low-pass
RC filter of 2Hz is designed for the system, the low-pass
filtering can be used to reduce the acceleration effects and
remove the noise frequency. The 12 bits analog-to-digital
converter is used in digitized the signals of the position
sensors.