Investigation of Electromagnetic Angle Sensor Integrated in FR4-Based Scanning Micromirror

Abstract

This paper performs a detailed investigation on the electromagnetic angle sensor integrated in the flame retardant 4 (FR4)-based scanning micromirror. An accurate theoretical model is presented, especially considering the coupling effect between the driving and sensing coils. Experimental results agree well with the theoretical results, and show a sensitivity of 55.0 mVp/° and a high signal-to-noise ratio (SNR) of 71.9 dB. Moreover, the linearity of the angle sensor can still reach 0.9995, though it is affected slightly by the coupling effect. Finally, the sensor’s good feasibility for feedback control has been further verified through a simple closed-loop control circuit. The micromirror operated with closed-loop control possesses better long-term stability and temperature stability than that operated without closed-loop control.

A Compound Control System for FR4-Based Electromagnetic Scanning Micrograting

“…The 12 × 12 mm platform with integrated driving coil and angle sensing coils is suspended by a pair of serpentine beams. Two NdFeB permanent magnets are assembled in parallel so that a nearly uniform magnetic field is formed near the FR4 platform [14]. Figure 1b,c shows the schematic of the top and bottom layouts of the scanning micrograting.…”

“…In recent years, most of the scanning micrograting has been developed and fabricated using MEMS technology. The actuation mechanisms can be mainly divided into four categories: electrostatic [9], electrothermal [10,11], electromagnetic [12][13][14][15], and piezoelectric [16]. The electromagnetic actuation mechanism is widely used for its large driving torque, linear mechanical properties, and low driving voltage.…”

“…Electromagnetic coils are more suitable for integration into the flame-retardant 4 (FR4)-based electromagnetic scanning micrograting, due to its excellent process compatibility with printed circuit boards (PCBs). Because of the shortcomings of the silicon MEMS scanning micrograting, such as high manufacturing cost, fragility, and poor shock and vibration [17], we developed the FR4-based electromagnetic scanning micrograting [13][14][15].…”

“…In our previous works, we demonstrated the feasibility of a closed-loop control system using an integrated electromagnetic angle sensor with an analog proportional-integral-derivative (PID) control system [1] and a simple analog difference closed-loop control system [14]. The controlled objects of the two control systems are the MOEMS scanning micrograting and the FR4-based electromagnetic scanning micromirror with the structure of the straight beams, respectively.…”

“…The controlled objects of the two control systems are the MOEMS scanning micrograting and the FR4-based electromagnetic scanning micromirror with the structure of the straight beams, respectively. The simple analog difference closed-loop control system proposed in [14] is just a control system operating based on the error between the set angle and the actual angle. The control output of this system is the angular error multiplied by a multiple.…”