Dynamic Modeling and Anti-Disturbing Control of an Electromagnetic MEMS Torsional Micromirror Considering External Vibrations in Vehicular LiDAR

Micromirrors based on micro-electro-mechanical systems (MEMS) technology are widely employed in different areas, such as optical switching and medical scan imaging. As the key component of MEMS LiDAR, electromagnetic MEMS torsional micromirrors have the advantages of small size, a simple structure, and low energy consumption. However, MEMS micromirrors face severe disturbances due to vehicular vibrations in realistic use situations. The paper deals with the precise motion control of MEMS micromirrors, considering external vibration. A dynamic model of MEMS micromirrors, considering the coupling between vibration and torsion, is proposed. The coefficients in the dynamic model were identified using the experimental method. A feedforward sliding mode control method (FSMC) is proposed in this paper. By establishing the dynamic coupling model of electromagnetic MEMS torsional micromirrors, the proposed FSMC is evaluated considering external vibrations, and compared with conventional proportion-integral-derivative (PID) controls in terms of robustness and accuracy. The simulation experiment results indicate that the FSMC controller has certain advantages over a PID controller. This paper revealed the coupling dynamic of MEMS micromirrors, which could be used for a dynamic analysis and a control algorithm design for MEMS micromirrors.

Active Disturbance Rejection Control of a 2D MEMS Micromirror with Sidewall Electrodes

This study proposes the active disturbance rejection control (ADRC) for a second degree of freedom (2D) electrostatic torsional micromirror with sidewall electrodes. The main idea is to use the linear extended state observer (LESO) to estimate the external disturbance and the angular velocity of the micromirror, and a feedback controller is further applied to achieve the position control of the micromirror. The effectiveness of the LESO in the estimation of the external disturbance and angular velocity is demonstrated. The proposed novel control scheme provides the micromirror with high positioning accuracy and disturbance rejection.

Design and Simulation of a MEMS Torsional Micromirror

In this paper, we designed an electrostatic driving MEMS torsional micromirror. The operation principle of the torsional micromirror is analyzed. Based on the analysis, a set of optimized design parameters of the micromirror is suggested. The design optimization of the micromirror is also performed with MathCAD software. At last an ANSYS simulation is achieved in the paper, which proves that the micromirror can provide a maximum workable torsional angle rotation of ±0.55º with corresponding driving voltage of 17.5V.

Modeling and Active Control of Circular Electrostatic Torsional Micromirror

Three main obstacles in modeling electrostatic torsional micromirror are hard to calculate – damping coefficient, mechanical spring constant and electrostatic torsion accurately. Because that parameter variations and model uncertainty of the torsional micromirror resulting from fabrication imperfections are inevitable, it is another problem to seek a control scheme for achieving accurate positioning and trajectory tracking of an electrostatic torsional micromirror. In this paper, aimed at a real prototype of circular electrostatic torsional micromirrorr, both static and dynamic behaviors are modeled and studied. A novel nonlinear Proportional, Integral and Derivative (PID) control are proposed in succession. Simulation results show that the system model derived is more accurate to the micromirror and the nonlinear PID can eliminate the static deviation.