Novel band-pass sliding mode control for driving MEMS-based resonators

This paper describes the application of a novel band-pass sliding mode control (SMC) to the driving mode of MEMS-based resonators and resonant sensors (e.g. vibrating gyroscopes). The proposed technique relies on binary electrostatic actuation of the movable mass, dependent on the dynamics of the sliding/switching surface, in such a way that the generated actuation tracks possible changes in the mechanical resonant frequency induced by external factors (humidity, temperature, pressure, etc.). The core of the proposed adaptive method is the implementation in hardware of an adaptive behavioral reference model used by the controller, able to track the sensed changes in dynamics. The architecture has a low hardware complexity and is suitable for VLSI implementation, in addition to a robust tracking behavior for large variations in the parameters of the resonator (e.g. temperature-induced changes in the stiffness coefficient). Simulation results demonstrate the effectiveness of the proposed technique by maintaining the actuation of the system at its resonance frequency even in the presence of variations of the stiffness coefficient (step, linear)or of applied external forces (external acceleration and noise). Simulations results suggest that the novel SMC-based oscillator offers an advantageous alternative to more complex phase-locked loop (PLL) architectures, traditionally used for the driving of MEMS resonator structures.