Microstepping bipolar stepping motor controller for document positioning
First Claim
1. A controller for operating a stepping motor having a plurality of motor coils and defining rotor and stator poles, the controller comprising:
- at least one processor having control inputs for receiving operational commands, data and program memory means including random access memory for storage of information defining at least one stepping motor operation;
a digital memory addressable by the processor and a digital to analog converter coupled to an output of the digital memory, the digital memory storing data values representing sinusoidally varying current levels in the motor coils over at least 90°
of a passage of rotor and stator poles, and the digital to analog converter being operable to convert data values selected in the digital memory by the processor to analog levels simultaneously for a plurality of outputs of the digital to analog converter at least equal in number to the motor coils;
a plurality of power stages coupled to said outputs of the digital to analog converter and operable to produce currents in the motor coils corresponding to the analog levels; and
,wherein the processor is operable selectively to read out the data values in the digital memory for accomplishing the stepping motor operation.
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Accused Products
Abstract
A controller for operating a stepping motor to a resolution defined by plural inter-pole motor positions includes a digital processor for communication with an external host system for controlling operation of the stepping motor, at least in a microstep mode. The processor selects Sine/Cosine driving current values for the motor windings from a table covering at least 90°, to define the inter-pole positions, stored in a RAMDAC or combination digital memory and digital to analog converter. The processor also controls scaling of the output of the digital to analog converter for different modes of operation, such as normal, hold and shutdown. The RAMDAC also can be loaded by the processor. Power stages are coupled to two analog outputs of the RAMDAC amplify the RAMDAC output signals, and provide a high power output to the windings using bridge drivers. The bridge drivers are enabled by analog comparators responsive to the analog input and to a current sense feedback, for enabling the bridge drivers until motor coil current reaches the value defined by the analog input, whereupon the driver is disabled and a one-shot is triggered to lock out the driver for preventing current overshoot.
60 Citations
13 Claims
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1. A controller for operating a stepping motor having a plurality of motor coils and defining rotor and stator poles, the controller comprising:
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at least one processor having control inputs for receiving operational commands, data and program memory means including random access memory for storage of information defining at least one stepping motor operation; a digital memory addressable by the processor and a digital to analog converter coupled to an output of the digital memory, the digital memory storing data values representing sinusoidally varying current levels in the motor coils over at least 90°
of a passage of rotor and stator poles, and the digital to analog converter being operable to convert data values selected in the digital memory by the processor to analog levels simultaneously for a plurality of outputs of the digital to analog converter at least equal in number to the motor coils;a plurality of power stages coupled to said outputs of the digital to analog converter and operable to produce currents in the motor coils corresponding to the analog levels; and
,wherein the processor is operable selectively to read out the data values in the digital memory for accomplishing the stepping motor operation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13)
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10. A controller for operating a stepping motor having a plurality of motor coils and defining rotor and stator poles, the controller comprising:
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at least one processor having control inputs for receiving operational commands, data and program memory means including random access memory for storage of information defining at least one stepping motor operation; a digital memory addressable by the processor and a digital to analog converter coupled to an output of the digital memory, the digital memory storing data values representing sinusoidally varying current levels in the motor coils over at least 90°
of a passage of rotor and stator poles, and the digital to analog converter being operable to convert data values selected in the digital memory by the processor to analog levels simultaneously for a plurality of outputs of the digital to analog converter at least equal in number to the motor coils;a plurality of power stages coupled to said outputs of the digital to analog converter and operable to produce currents in the motor coils corresponding to the analog levels, the power stages each comprising a comparator and a driver responsive to the comparator, a drive current level produced in a respective one of the motor coils being sensed and fed back to one input of the comparator, and an analog level from the RAMDAC being coupled to another input of the comparator, such that the comparator energizes the driver until the drive current level reaches the analog level from the RAMDAC; means coupled to an output of the comparator and to the driver, operable to disable the driver for a predetermined period following a time at which the drive current level reaches the analog level; and
,wherein the driver comprises a bridge driver having phase control inputs coupled to outputs of the processor, and operable for reversing an output polarity of the bridge driver.
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Specification