Importance

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Abstract

An improved method and servo control apparatus (C) is provided for controlling the motion of a linear electric motor (A) which in turn generates motion command signals to various apparatus such as a hydraulic steering system (B). Preferably, the servo control apparatus (C) includes a power supply circuit (60), a servo amplifier circuit (62), a pulse width modulation circuit (64), an H-bridge drive circuit (66) and an inductive position sense circuit (68). The voltage at a node (42) between coil pairs (38, 40) in the motor (A) is sensed and synchronously demodulated using transmission gates (222, 224) to develop a DC signal representative of armature (30) position from a center location. The signal on a current shunt resistor (200) is synchronously demodulated by transmission gates (208, 209)to generate a signal, the phase of which is determined with respect to the motor drive signal. The phase signal directly indicates whether the armature is off center towards drive coil 38 or drive coil 40.

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First Claim