 Moving Coil and Moving Magnet non-commutated linear motors provide short strokes with constant force over the full stroke in both directions. The motors provide a very fast response because of a low (<<1msec) electric time constant.
Non-commutated DC linear motors operate at very high speeds without cogging or force ripple and with infinite resolution. For closed loop operation, the motor is coupled with an appropriate feedback device, motor control and motion controller.
The Moving Coil model consists of a cylindrical coil that moves within an annular air gap of the magnet assembly. The poles are magnetized by rare earth magnets. When DC voltage is applied, the coil is caused to move with constant force. When polarity is reversed, the direction of travel is reversed. Magnetic-attractive forces and hysteresis loss are eliminated. Also, eddy currents can be eliminated by utilizing a plastic bobbin.
The Moving Magnet model is like a piston moving within a cylinder. The piston consists of permanent magnets with steel pole pieces and a shaft that passes axially through its center. Endcaps with bearings on both ends of the cylinder support the shaft. The cylinder contains a bobbin to support the coil and an outside steel tube for containing the magnetic flux. DC voltage applied to the coil causes the assembly to move and when the polarity is reversed the direction of travel is reversed.
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