Force-Amplifying Compliant Mechanism for Closed-Loop MEMS Accelerometer

Compliant mechanisms have been effectively utilized in microelectromechanical systems (MEMS) accelerometers to enhance the sensitivity of open-loop accelerometers. Traditionally, these mechanisms have been employed for displacement amplification. However, in this letter, a compliant mechanism is used to amplify the control force within the MEMS accelerometer. The structure incorporates a pair of compound lever-type mechanisms to amplify control forces acting in both forward and backward directions along the sensing axis. Closed-loop control is crucial for maintaining the linear characteristics of the MEMS accelerometer across a wide measurement range. Electrostatic force feedback is applied by providing dc voltage to the respective comb fingers for closed-loop implementation. As the input acceleration increases, the control voltage also rises. However, microlevel circuits have limitations on the maximum voltage that can be applied. The proposed force amplification strategy reduces the voltage required for position control. Consequently, the linear behavior of the MEMS accelerometer, the displacement of the proof mass, and the change in capacitance are maintained without the need for high voltage in electrostatic control.