Patent ID: 7211974

Claim:
A motor drive system comprising: a movable body with a plurality of permanent magnets, alternately magnetized at opposite poles, continuously disposed thereon; a plurality of stators each consisting of an array of electromagnetic coils disposed so that they do not come into contact with said movable body, said electromagnetic coil arrays having a plurality of phases, there being phase difference between the electromagnetic coils of the respective phases; and a drive circuit that moves said movable body based on the attraction—repulsion between said movable body and electromagnetic coils generated by supplying an excitation current to each electromagnetic coil array to alternately magnetize the electromagnetic coils in each electromagnetic coil array at opposite poles, wherein said drive circuit includes: sensors that each detect the periodic magnetic field change caused by the movement of said permanent magnets to output an analog value, said sensors having the same phase differences as the electromagnetic coils; a gain controller that adjusts the peak value of the analog output value of each sensor and outputs the peak value; a movement direction instruction unit for the motor; a reversal circuit that reverses the movement direction of said movable body by reversing the polarity of output from each sensor based on the output from the movement direction instruction unit; and a PWM control unit that creates a pattern for exciting said electromagnetic coils by amplifying the output of said gain controller and then performing PWM control on the output of said gain controller, and that directly supplies said electromagnetic coils with that pattern as a waveform for driving said electromagnetic coils; and wherein said movable body is constructed to have a plurality of constitutions in which the same heteropolar arrangement of a plurality of different permanent magnets constitutes a pair, and, when the position between said heteropolar arrangement constituting a pair is 2π, said each sensor is able to linearly detect an arbitrary position between said 2π.