This paper investigates a novel structure voice coil motor (VCM), which is used in ventilator. The VCM controls on and off of the valve of ventilator, so steady thrust and fast response are needed. The influences of structure parameters to the performance are investigated by finite element analysis. The methods for increasing thrust and improving smoothness of force-displacement curves are proposed. A prototype is designed according to the optimized parameters. And the results of the prototype show that the thrust fluctuation is 3.4%.

voice coil motor， electromagnetic field， finite element analysis， thrust fluctuation