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Digital robot control having an improved pulse width modulator

  • US 4,894,598 A
  • Filed: 08/05/1988
  • Issued: 01/16/1990
  • Est. Priority Date: 11/20/1986
  • Status: Expired due to Term
First Claim
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1. A digital pulse width modulator circuit for operating power amplifiers and joint motors during positive, negative and non-forcing motor drive requests by measuring the motor current in an associated sense resistor for each joint motor in a robot control comprising:

  • up/down counter means for generating a sawtooth waveform, having positive and negative apexes adapted for timing the current measurement within a control pulse interval, by counting up to and down from an upper endpoint to a lower endpoint as a function of time;

    means for comparing the count of the counter means for the sawtooth waveform to a signal representing a control command so as to define a time span needed to operate a power amplifier and energize an associated joint drive motor in accordance with the control command;

    means for generating a first output control pulse for power amplifier switching when one drive polarity is commanded, said first output control pulse having a width corresponding to the defined time span and based on a count comparison referenced to the upper endpoint of the sawtooth waveform; and

    means for generating a second output control pulse for power amplifier switching when the other polarity is commanded, said second output control pulse having a width corresponding to the defined time span and based on a count comparison referenced to the lower endpoint of the sawtooth waveform.

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