Closed loop stepper motor circuitry without encoder
First Claim
1. In combination,an electrical stepping motor having a plurality of motor coils and a rotatable armature,a driver including switching circuitry and connected with said motor coils for consecutively applying an EMF to said motor coils on switching of the driver to cause rotation of said armature,an oscillator,a phase locked loop circuit driven by said oscillator and including a voltage controlled wave generator having a plurality of output connections to said driver to drive the driver so that the driver causes consecutive energization of said motor coils for driving said armature,a control connection connected with one of said motor coils for providing a voltage which is the composite of the back EMF in said motor coil and the drive EMF applied to said coil from said driver,a multiplier circuit having said control connection and one of said loop circuit output connections connected to it as inputs to thereby provide an error output signal, andmeans for applying said error output signal to a point in said phase locked loop circuit so that said driver effectively holds the speed of said armature within close limits.
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Accused Products
Abstract
Stepper motor control circuitry including a phase locked loop circuit formed by a phase detector outputted to a filter and a voltage controlled triangular and square wave generator which has a frequency control input terminal connected to the output of the filter and which provides a square wave on an output thereof connected as an input to the phase detector. An oscillator drives the phase detector, and the outputs of the generator are connected as inputs to a pulse width modulated driver which has its outputs connected to the coils of the stepper motor. A differential amplifier is connected across one of the coils of the motor, and a balanced modulator synchronous detector or multiplier has two inputs one of which constitutes an output of the differential amplifier and the other of which is a connection to the square wave output of the generator. The output of the multiplier constitutes an error signal which is supplied to a summing junction between the filter and generator so that, upon the application of an instantaneous load to the stepper motor, the error signal causes a very quick return to normal speed of the motor.
53 Citations
15 Claims
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1. In combination,
an electrical stepping motor having a plurality of motor coils and a rotatable armature, a driver including switching circuitry and connected with said motor coils for consecutively applying an EMF to said motor coils on switching of the driver to cause rotation of said armature, an oscillator, a phase locked loop circuit driven by said oscillator and including a voltage controlled wave generator having a plurality of output connections to said driver to drive the driver so that the driver causes consecutive energization of said motor coils for driving said armature, a control connection connected with one of said motor coils for providing a voltage which is the composite of the back EMF in said motor coil and the drive EMF applied to said coil from said driver, a multiplier circuit having said control connection and one of said loop circuit output connections connected to it as inputs to thereby provide an error output signal, and means for applying said error output signal to a point in said phase locked loop circuit so that said driver effectively holds the speed of said armature within close limits.
Specification