Stepper motor shaft position sensor
AssigneeAllied-Signal Inc.
InventorTerry J. Ahrendt
Life of this patent
Estimating the term…
Abstract
A stepper motor shaft position sensor differentiates the current provided when the stepper motor is excited as by a step command voltage. The differentiated current is, in effect, a signature indicative of whether or not the motor shaft has taken a step. If the differentiated current falls below a predetermined level within a predetermined interval the motor shaft has taken a step as indicated by a sensor output at a predetermined logic level. Otherwise, the sensor output is at another predetermined logic level indicating that a step has not been taken and the motor is in a stalled condition. The sensor output is applied to a utilizing means which provides a continuous verification of the steppper motor shaft position.
Claims28
A stepper motor shaft position sensor, comprising:
- means for sensing the current developed by the stepper motor when said motor is excited and for providing a motor current signal;
- means for differentiating the motor current signal and for providing a differnetiated signal including a first operational amplifier connected to the means for sensing the motor current, and a second operational amplifier connected to the first operational amplifier and providing the differentiated signal;
- means for providing a reference signal at a predetermined level;
- means for comparing the differential motor current signal and the signal at a predetermined level and for providing a comparison signal;
- means for providing a signal during a predetermined internal;
- means connected to the comparing means and the means for providing a signal during a predetermined interval and responsive to the comparision signal and the signal during the predetermined interval for providing an output signal, the output signal being at a first logic level when the motor shaft has taken a step and being at a second logic level when the motor shaft is stalled;
- and
- means connected to the means for providing the signals at the first and second logic levels for indicating the step status of the stepper motor shaft.
For use with a stepper motor of the type which is energized by a motor shaft step command signal to provide a motor current, a sensor for sensing the motor current and for verifying if the motor shaft has taken a step in response to the step command signal, comprising:
- means for sensing the motor current icnluding a resistor arranged with said stepper motor and having one leg connected to ground, and a motor current signal provided at the other leg of said resistor;
- means for differentiating hte sensed motor current and for providing a differentiated motor current signal including a first operational amplifier connected at an input terminal thereof ot the other leg of the resistor;
- and
- a second operational ampilifier connected at an input terminal thereof to an output terminal of the first operational amplifier;
- means for providing a reference signal at a predetermined level;
- means for comparing the differentiated signal at a predetermined level;
- means for comparing the differentiated motor current signal and the signal at the predetermined level and for providing a comparison signal;
- means for providing a signal during a predetermined internal;
- means connected to the comparing means and the means for provding a signal during a predetermined interval and responsive to the signals therefrom for providing a first output signal at a first logic level when the comparison signal falls below the predetermined level during the predetermined interval, said first output signals being indicative that the motor shaft has taken a step, and for otherwise providing a second output signal, said second output signal being indicative that the motor shaft is stalled;
- and
- means connected to the means for providing the first and second signals for verifying the position of the stepper motor shaft.
With a stepper motor of the type which is energized by a motor shaft step command signal to provided a motor current, and including means for sensing the motor current to determine if the motor shaft has taken a step in response to the step command signal, the improvement comprising:
- means for differentiating the sensed motor current and for providing a differentiated signal including a first operational amplifier connected to the means for sensing the motor current, and a second operational amplifier connected to the first operational amplifier and providing the differentiated signal.
With a stepper motor of the type which is energized by a motor shaft step command signal to provide as motor current, and including means for sensing the motor current to determine if the motor shaft has taken a step in response to the step command signal, the improvement comprising:
- means for differentiating the sensed motor current and for providing a differentiated signal;
- means for providing a reference signal at a predetermined level;
- means for providing a signal during a predetermined interval;
- a first monostable multivibrator;
- a clock for providing driving pulses, the first monostable multivibrator conencted to the clock and driven by the pulses therefrom;
- and;
- a second monostable mutlivibrator connected to the first monostable multivibrator and driven thereby for providing the signal during the predetermined interval;
- means for comparing the differentiated signal and the reference signal at the predetermined level and for providing a comparision signal;
- and
- means connected to the comparing means and to the predetermined interval signal means and responsive to the signals therefrom for providing a signal indicative of the step status of the motor shaft.
Dependencies are inferred from the claim text.