Importance

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Abstract

A stepping motor system is shown wherein a method is employed for determining the optimum amplitude of the current supplied to the stator winding of the motor. A series of different currents are applied to the motor. First, the stator windings are energized with currents of certain base magnitudes. Then the current in one winding is increased by a small amount and the current in the adjacent winding is decreased by a small amount so that the rotor tends to move towards its new equilibrium position. When the rotor reaches its maximum displacement the current changes in the windings are reversed so that not only will the rotor 'hunt' for its new equilibrium position but it overshoots with twice the magnitude. This process continues for a certain period of time during which the oscillation magnitudes rapidly grow. In one embodiment, after a maximum amplitude is reached, the current changes are applied out of phase with the oscillations to now try to decrease their amplitude. After another period of time, the current changes are terminated, the residual oscillations are monitored and all oscillations greater than a given amplitude are recorded. As this process can be repeated for different base currents, that current which yields the minimum number of 'over' oscillations during the monitoring period is selected as the current amplitude for subsequent use in positioning the rotor. In another embodiment, the damping portions of the method is not performed. Then, the base current is selected which results in the greatest number of 'over' oscillations.

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First Claim