Design, development, and testing of a radial-flux permanent magnet micromotor based on 3D solenoid MEMS in-chip coils

Rotary micromotors are widely used in micro rotating actuators, such as microscale aerial vehicles, scanners, and chip cooling fans. Owing to the high power density, electromagnetic rotary micromotors fabricated using micro electro-mechanical systems (MEMS) have significant application potential. This paper presents the design and development of a millimeter-scale permanent magnet (PM) electromagnetic rotary micromotor based on three-dimensional (3D) iron-core solenoid micro coils, which are fabricated using MEMS processes. A method of power supply connection for the stator is proposed to facilitate the assembly, and the micromotor rotates successfully with the control strategy. The micromotor achieved a rotational speed of 6745 rpm with a speed fluctuation about ± 5 rpm. Test results show a maximum torque of approximately 250 μN·m at 1 A, and a peak-to-peak back electromotive force (EMF) of 90 mV at a constant speed of 3120 rpm. To measure the output power and the maximum torque at various speeds, a method of tiny torques providing and load measuring for micromotors was proposed and validated. With 470 mA current applied, the torque ranges from 20 μN·m to 110 μN·m, and the maximum output power is 30 ± 2 mW.