Importance

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Abstract

A control system that increases apparent linear motor stiffness and faster frequency for a digital electronic drive of one or more brushless DC linear motors. It comprises a position transducer providing an analog electrical signal indicative of the linear position of a movable part of the linear motor and being induced from an electrical signal supplied to or derived from the motor field winding; a converter for changing the analog signal to an acceleration feedback signal; a processor for providing a position error electrical signal derived by computing the difference between the actual position feedback signal and a position reference signal; and a processor for providing a velocity error electrical signal derived from the difference between the first derivative of the position error electrical signal and the actual velocity feedback signal to produce a velocity command signal, and for providing an acceleration error electrical signal derived from the difference between the second derivative of the position feedback signal and the actual acceleration feedback signal to produce a motor command signal to the field winding of the motor. A method of using such control system comprises providing a positioning apparatus having stacked movable members interconnected by linear motors to promote three-axis movement of a ram acting as the last of said movable members and carrying out the functions of the control for each linear motor.

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First Claim