Pulse counting phase modulation method and apparatus for controlling a servo-mechanism

Claim 2

Apparatus for controlling the output of a servomotor comprising: a cyclically driven digital counter having an output providing a periodic reference waveform at a frequency which is a submultiple of the digital counting rate; a digital command signal register having an input through which a single, complete digital command signal for positioning the servomotor output at one discrete position is received for temporary storage until another discrete position is commanded; input means connected with the input of the command signal register for loading new command signals into the register; comparator means connected between the digital counter and the command signal register for comparing the digital counts and the digital command signals and producing coincidence signals at each coincidence of the digital count and the digital command signals; timing means connected with the digital counter, the input means and the comparator means for stepping the digital countEr, loading the command signal register and comparing the digital counts and the command signals respectively at distinctly different times; generating means connected to the comparator means and responsive to the coincidence signals for producing a periodic command signal waveform having the same period or frequency as the reference waveform and a phase relationship with the reference waveform uniquely related to the command signal in the register; the comparator means and the generating means cooperating whenever operating to continuously produce the periodic command signal waveform in response to a single and complete digital command signal stored in the command signal register; and phase responsive motor control means connected with the servomotor, the generating means and the digital counter and including a phase detector responsive to the reference waveform provided by the digital counter and the command signal waveform produced by the generating means for positioning the output of the servomotor in accordance with the phase relationship of the periodic waveforms.

Claim 3

Apparatus for controlling as defined in claim 1 wherein the command signal register is a digital up/down counter.

Claim 4

Apparatus for controlling as defined in claim 1 wherein the command signal register comprises a digital register having a given plurality of bit stages for storing digital commands and the digital counter has a plurality of bit stages equal to the plurality of bit stages in the register.

Claim 5

Apparatus as defined in claim 3 wherein the generating means comprises a one shot multivibrator generating a pulse having a duration equal to one half the period of the periodic reference wave.

Claim 6

Apparatus for controlling as defined in claim 3 wherein the bit stages in the digital register are binary coded bit stages and the comparator means is connected to each of the bit stages in the digital register and the corresponding bit stages in the digital counter to produce one timing signal upon the identity of the bits in the register and the corresponding bits in the counter and another timing signal one half of a count cycle of the counter after the one timing signal.

Claim 7

Apparatus as defined in claim 5 wherein the generating means comprises a flip-flop set by the one of the timing signals from the comparator means and reset by the other of the timing signals to provide the phased and periodic command signal waveform.

Claim 8

Apparatus for controlling as defined in claim 1 wherein the digital counter is a multiple bit counter and the output of the digital counter providing the reference waveform is connected to the most-significant bit stage of the counter.

Claim 9

Apparatus for controlling as defined in claim 7 wherein the digital counter is a binary counter having outputs from both the most significant bit and the second most-significant bit stages; and wherein a waveform inverter and a frequency divider are connected to the output from the second most-significant stage.

Claim 10

Apparatus for controlling as defined in claim 8 wherein the phase responsive motor control means includes a feedback position resolver connected with the output of the servomotor and having field windings connected respectively to the most-significant bit stage of the digital counter and the frequency divider, and a rotor winding connected to the phase detector.

Claim 11

Apparatus for controlling as defined in claim 1 wherein the phase responsive motor control means further includes a cyclically rotatable position feedback sensor connected for cyclic rotation to the output of the servomotor.

Claim 12

Apparatus as defined in claim 10 wherein the position feedback sensor comprises a resolver having at least one field winding connected to the output of the digital counter providing the reference waveform and a rotor winding connected to the phase detector.

Claim 13

In a phase responsive servomechanism having a movable output member, an improved digital control apparatus for producing phased control signals to move tHe output member between a plurality of discrete positions comprising: a digital counter having a count capacity corresponding with the plurality of discrete positions of the movable member; a multiphase clock having multiple outputs providing time-phased pulse trains, each train having the same predefined pulse rate, a first of the outputs being connected in driving relationship with the counter to establish a digital counting rate corresponding to the predefined pulse rate; reference means connected to the stage of the counter for the most-significant digit to produce a periodic reference waveform at the same frequency as the counting cycles of the digital counter; a digital command register having a digital capacity corresponding to that of the counter; gated input means connected to the command register and responsive to a second of the outputs of the multiphase clock for loading commands into the register; comparing means gated into operation by a third of the outputs of the clock and connected to the digital counter and to the digital register for producing phased timing signals, the phases of the timing signals being referenced to the counting cycles and a function of the command signals in the register; and generating means connected to the comparing means and responsive to the phased timing signals for producing periodic command waveforms in phased relationship with the reference waveform, the phase relationships of the respective command waveforms with the reference waveform corresponding to the phase relationships of the respective timing signals and the counting cycles; the comparator means and the generating means cooperating at all times during the controlling operation to continuously produce the periodic command waveform with a given phase relationship in response to a complete digital command and without changing the digits stored temporarily in the command register.

Claim 14

In a phase responsive servomechanism having a movable output member, an improved digital control apparatus for producing phased control signals to move tHe output member between a plurality of discrete positions comprising: a digital counter having a count capacity corresponding with the plurality of discrete positions of the movable member; a multiphase clock having multiple outputs providing time-phased pulse trains, each train having the same predefined pulse rate, a first of the outputs being connected in driving relationship with the counter to establish a digital counting rate corresponding to the predefined pulse rate; reference means connected to the stage of the counter for the most-significant digit to produce a periodic reference waveform at the same frequency as the counting cycles of the digital counter; a digital command register having a digital capacity corresponding to that of the counter; gated input means connected to the command register and responsive to a second of the outputs of the multiphase clock for loading commands into the register; comparing means gated into operation by a third of the outputs of the clock and connected to the digital counter and to the digital register for producing phased timing signals, the phases of the timing signals being referenced to the counting cycles and a function of the command signals in the register; and generating means connected to the comparing means and responsive to the phased timing signals for producing periodic command waveforms in phased relationship with the reference waveform, the phase relationships of the respective command waveforms with the reference waveform corresponding to the phase relationships of the respective timing signals and the counting cycles; the comparator means and the generating means cooperating at all times during the controlling operation to continuously produce the periodic command waveform with a given phase relationship in response to a complete digital command and without changing the digits stored temporarily in the command register.

Claim 15

An improved digital control apparatus as defined in claim 12 wherein the digital command register is another counter having the same digital capacity as the digital counter.

Claim 16

An improved digital control apparatus as defined in claim 12 wherein the digital counter comprises an up counter and the digital command register comprises a digital up/down counter.

Claim 17

An improved digital control apparatus as defined in claim 12 wherein the counter is a binary counter and the reference means further includes an inverter connected to the second most-significant digit stage of the counter and a frequency divider connected to the inverter, the divider having the characteristic of reducing frquencies by a factor of two whereby two phased reference waveforms are generated.

Claim 18

A control apparatus receiving digital commands and producing two periodically varying waveforms phased in accordance with the digital commands received comprising: a digital command register having a selected number of bit stages for receiving a single and complete digital command corresponding uniquely to a specific and desired phase of the waveforms and for storing the command temporarily until a new phase is desired; a cyclically driven digital counter having bit stages corresponding to the bit stages of the command register and an output from one of the bit stages regularly providing one of the periodic waveforms as a reference at a frequency which is a sub-multiple of the digital counting rate of the counter; gated digital comparator means connected to the bit stages of the command register and the digital counter for producing coincidence signals at each coincidence of the digital count in the counter and the digital command in the register and at each coincidence of the digital count and the digital command in all but the most significant bit stages of the counter and the register; shaping means connected to the comparator and responsive to the coincidence signals from the comparator for producing the other periodic waveform phased with the reference waveform in accordancE with the digital command in the register; and gated input means connected to the digital command register for controlling the entry of new commands into the register; and a multiphase clock having three outputs providing three time-phase trains of non-overlapping pulses, the outputs being connected with the cyclically driven counter, the gated comparator means and the gated input means for driving the counter, gating the comparator means on and entering new commands in the command register at respectively different times.

Claim 19

A control apparatus receiving digital commands and producing two periodically varying waveforms phased in accordance with the digital commands received comprising: a digital command register having a selected number of bit stages for receiving a single and complete digital command corresponding uniquely to a specific and desired phase of the waveforms and for storing the command temporarily until a new phase is desired; a cyclically driven digital counter having bit stages corresponding to the bit stages of the command register and an output from one of the bit stages regularly providing one of the periodic waveforms as a reference at a frequency which is a sub-multiple of the digital counting rate of the counter; gated digital comparator means connected to the bit stages of the command register and the digital counter for producing coincidence signals at each coincidence of the digital count in the counter and the digital command in the register and at each coincidence of the digital count and the digital command in all but the most significant bit stages of the counter and the register; shaping means connected to the comparator and responsive to the coincidence signals from the comparator for producing the other periodic waveform phased with the reference waveform in accordancE with the digital command in the register; and gated input means connected to the digital command register for controlling the entry of new commands into the register; and a multiphase clock having three outputs providing three time-phase trains of non-overlapping pulses, the outputs being connected with the cyclically driven counter, the gated comparator means and the gated input means for driving the counter, gating the comparator means on and entering new commands in the command register at respectively different times.

Claim 20

Apparatus for controlling the output of a servo-motor as defined in claim 1 wherein the timing means is a multiphase clock having different clock outputs in time-phased relationship connected respectively to the digital counter, the input means and the comparator means.

Claim 21

Apparatus for controlling as defined in claim 17 wherein the multiphase clock has four outputs providing time-phased pulse trains, two of outputs being connected to the comparator means for comparing the digital counts and the command signals before and after a step of the digital counter and a loading of a new command signal into the digital register.