A bi-directional short stroke permanent magnet linear DC Motor

The structure and features of a bi-directional short stroke linear DC motor with permanent magnets were presented. The magnetic field was produced by the two concentric ring permanent magnets embedded on the stator. The moving coil mounted on the shaft was a tubular coil situated within a radially oriented magnetic field and balanced by the two opposing forces generated by two springs along with the central axis and supported by the two linear bearings. The linear guide prevented the moving coil from rotating around on the central axis and carries with the linear optical encoder of 1μm resolution. The required controlled travel was limited in a ±5-mm displacement range. The prototype specifications were given. The experimental results show that between the electromagnetic force and the coil electric current exists a linear relation. When the frequency of control command is the 30Hz sine wave, the peak current, the peak force, the max velocity and the max acceleration are, respectively, ±2.56A, ±30.9N, ±0.86m/s and±16.5g.