Method and apparatus for controlling stepper motors
First Claim
1. A method for critically damping the natural resonance of a stepper motor, said method comprising the steps of:
- (a) generating position signals;
(b) generating a digital velocity signal representing the velocity of the stepper motor shaft;
(c) generating a digital error signal functionally related to said position signals and said digital velocity signal; and
(d) generating command currents for driving the stepper motor and critically damping the natural resonance of the stepper motor in response to said digital error signal.
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Abstract
A method and apparatus for controlling a stepper motor involves the generation of command currents which drive the stepper motor and provided critical damping of the natural resonance of the stepper motor. Digital error signals are developed by selectively combining a position signal and a digital velocity signal which is derived from a feedback signal proportional to velocity. In one embodiment, the digital error signals are converted into command currents for driving the stepper motor in such a manner as to achieve damping of the motor'"'"'s natural resonance. In an anternative embodiment, the digital error signals and feed forward acceleration signals and/or feed forward velocity signals are converted into command currents for driving the stepper motor so as to achieve damping of the motor'"'"'s natural resonance, as well as correction for positional errors induced by either velocity or acceleration.
25 Citations
12 Claims
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1. A method for critically damping the natural resonance of a stepper motor, said method comprising the steps of:
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(a) generating position signals; (b) generating a digital velocity signal representing the velocity of the stepper motor shaft; (c) generating a digital error signal functionally related to said position signals and said digital velocity signal; and (d) generating command currents for driving the stepper motor and critically damping the natural resonance of the stepper motor in response to said digital error signal.
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2. A method for critically damping the natural resonance of a stepper motor and compensating for lag comprising the steps of:
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(a) generating position signals; (b) generating a digital velocity signal representing the velocity of the stepper motor shaft; (c) combining said position signal and said digital velocity signal in a digital subtractor and generating a digital error signal that is related to said position signal and said velocity signal; (d) generating a digital feed forward signal; and (e) generating command currents for driving the stepper motor and critically damping the natural resonance of the stepper motor in response to said digital error signal generated by said digital subtractor and said digital feed forward signal. - View Dependent Claims (5)
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3. A method for critically damping the natural resonance of a stepper motor and for anticipating lag due to acceleration comprising the steps of:
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(a) generating position signals; (b) generating a velocity signal representing the velocity of the stepper motor shaft; (c) combining said position signal and said velocity signal in a digital subtractor and generating a digital error signal related to said position signal and said velocity signal; (d) generating a digital feed forward acceleration signal; and (e) generating command currents for driving the stepper motor and critically damping the natural resonance of the stepper motor in response to said digital error signal generated by said digital subtractor and said digital feed forward acceleration signal.
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4. A method for critically damping the natural resonance of a stepper motor and for compensating for positional lag due to feedback comprising the steps of:
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(a) generating position signals; (b) generating a velocity signal representing the velocity of the stepper motor shaft; (c) combining said position signal and said velocity signal in a digital subtractor and generating a digital error signal related to said position signal and said velocity signal; (d) generating a digital feed forward velocity signal which is proportional to velocity; and (e) generating command currents for driving the stepper motor and critically damping the natural resonance of the stepper motor in response to said digital error signal generated by said digital subtractor and said digital feed forward velocity signal.
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6. An apparatus for controlling a stepper motor and for critically damping the natural resonance of the stepper motor, said apparatus comprising:
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(a) digital processing means for developing a digital error signal related to a digital velocity signal representing the shaft velocity of the stepper motor and a digital position signal applied to the stepper motor; and (b) means responsive to said digital error signal for generating command currents for driving the stepper motor and critically damping the natural resonance of the stepper motor.
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7. An apparatus for controlling a stepper motor and critically damping the natural resonance of the stepper motor and for compensating for lag, said apparatus comprising:
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(a) means for generating a position signal; (b) means for generating a digital velocity signal representing the shaft velocity of the stepper motor; (c) processing means for receiving said velocity signal and said position signal, said processing means generating a digital error signal related to said velocity signal and said position signal; (d) digital means for generating a feed forward signal; and (e) means responsive to said digital error signal and said feed forward signal for generating command currents for driving the stepper motor. - View Dependent Claims (8, 9, 10, 11, 12)
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Specification