Importance

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Abstract

A method and apparatus for controlling stepmotors having a broad range of applications including fuel control for gas-turbine engines, and operating powered automatically controlled doors for mass transit vehicles is disclosed. Step motor control through analysis of the motor winding currents during application of controlled voltage pulse provides a basis for evaluating shaft torque conditions at the motor load without return or feedback signals from the driven load. This type of current analysis utilizing digital techniques provides a convenient, reliable, and economical means for detecting stepmotor output shaft position and loading. Detection and recognition of output shaft load or drive requirements is then utilized in a control system wherein functional requirements of the system including motion and/or torque requirements of the shaft output load can be controlled in accordance with desired system operation. A control algorithm based on earlier determined stepper current characteristics is utilized in evaluating any particular stepper motor at any time during operation. Digital techniques utilize the aforementioned algorithm sample stepper motor current, measure and detect predetermined time based values of motor current, thereby providing a basis for evaluating stepper motor shaft loading during each step corresponding to and initiated by a voltage pulse.

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First Claim