Exponential predictor and sampled-data systems

Claim 2

In a control system wherein the magnitude of a variable process condition is sampled at intervals and a sampled-data signal is generated thereby, said sampled-data signal then being utilized to control condition-changing means which is effective to institute a change in the magnitude of said variable process condition, an improved means for anticipating the change in the process condition which is occurring between sample times, comprising: a predictor network connected to receive said sampled-data signal as an input and having a time-diminishing output connected to said condition-changing means, the time constant of said network being of the order of the response time of said control system and the process being controlled thereby; and reset means connected to reset said network to the new sampleddata signal at each sample time.

Claim 3

A control system as defined in claim 1 wherein the time constant of said network provides a time-diminishing output having a decreasing value which approaches the expected value of the sampled-data signal at the next sample time.

Claim 4

A control system as defined in claim 2 wherein the time internal between said sampled-data signals is of the order of, or longer than, the response time of said control system.

Claim 5

A control system as defined in claim 3 wherein said predictor network includes an R-C differentiating network.

Claim 6

A control system as defined in claim 4 wherein said reset means includes switch means connected in parallel with said capacitor.

Claim 7

A control system as defined in claim 5 wherein closing of said switch means at each sample time discharges said capacitor and restores the output of said differentiating network to a magnitude related to the magnitude of said sampled-data signal existing at the sample time.

Claim 8

A control system as defined in claim 6 wherein said sampled-data signal is a variable analog signal.

Claim 9

In a closed-loop control apparatus for use in controlling the magnitude of a physical phenomena which is geneRated by a process, wherein said process includes phenomena-changing means controlled by said control apparatus; and wherein said control apparatus includes means for sensing the magnitude of said physical phenomena, the closed-loop represented by said control apparatus, said phenomena-changing means, said process and said means for sensing the magnitude of said physical phenomena having a known time constant of response; the improvement comprising: a predictor network connected to receive as an input a sampled-data signal which is derived from said sensing means, said signal being representative of the magnitude of said physical phenomena at or during the time of sampling, said predictor network being constructed and arranged to provide a time-diminishing output whose instantaneous magnitude between sampling times is a prediction of the instantaneous magnitude of said physical phenomena and whose time-diminishing characteristic is of the order of said known time constant of response, and means operable at the time of sampling to reset said predictor network to a new signal representing the then existing magnitude of said physical phenomena.

Claim 10

In a closed-loop control apparatus for use in controlling the magnitude of a physical phenomena which is geneRated by a process, wherein said process includes phenomena-changing means controlled by said control apparatus; and wherein said control apparatus includes means for sensing the magnitude of said physical phenomena, the closed-loop represented by said control apparatus, said phenomena-changing means, said process and said means for sensing the magnitude of said physical phenomena having a known time constant of response; the improvement comprising: a predictor network connected to receive as an input a sampled-data signal which is derived from said sensing means, said signal being representative of the magnitude of said physical phenomena at or during the time of sampling, said predictor network being constructed and arranged to provide a time-diminishing output whose instantaneous magnitude between sampling times is a prediction of the instantaneous magnitude of said physical phenomena and whose time-diminishing characteristic is of the order of said known time constant of response, and means operable at the time of sampling to reset said predictor network to a new signal representing the then existing magnitude of said physical phenomena.

Claim 11

A control apparatus as defined in claim 8 wherein said predictor network includes an R-C network whose capacitor charge is adjusted to be indicative of said physical phenomena at the time of each sampling.

Claim 12

A control apparatus as defined in claim 9 wherein said R-C network is a differentiator and wherein the charge on said capacitor is adjusted by switch means which is effective to momentarily close and thereby discharge said capacitor.

Claim 13

In combination, an information source having a nominal content, being variable from said nominal content and having a known time constant; sampler means effective at times to sample the information content of said information source at times which are variable from an aperiodic to a periodic condition; a predictor network having an input connected to said sampler means to receive the information content of said information source as an input signal at each of said sample times, said predictor network including modifier means having a time constant of the order of said known time constant and operating on said information content to produce a time-diminishing output approaching the nominal content of said information source; and reset means controlled by said sampler means and effective at each of said sample times to restore the output of said predictor network to the then existing information content of said information source.

Claim 14

In combination, an information source having a nominal content, being variable from said nominal content and having a known time constant; sampler means effective at times to sample the information content of said information source at times which are variable from an aperiodic to a periodic condition; a predictor network having an input connected to said sampler means to receive the information content of said information source as an input signal at each of said sample times, said predictor network including modifier means having a time constant of the order of said known time constant and operating on said information content to produce a time-diminishing output approaching the nominal content of said information source; and reset means controlled by said sampler means and effective at each of said sample times to restore the output of said predictor network to the then existing information content of said information source.

Claim 15

The combination defined in claim 11 wherein the times of sampling are variable for a relatively long aperiodic condition to a shorter periodic condition, and wherein the time interval of said periodic condition is of the order of, or longer than, the response time of said control system.

Claim 16

The combination defined in claim 12 wherein said modifier means includes an R-C network, the voltage across the resistor thereof being adjusted in accordance with the value of said information content at each of said sample times.

Claim 17

The combination defined in claim 13 wherein said reset means is effective at each of said sample times to restore the charge of the capacitor thereof to substantially zero.

Claim 18

The combination defined in claim 14 wherein said reset means includes normally open switch means connected in parallel with said capacitor, and means effective at each of said sample times to momentarily close said switch means.

Claim 19

A hybrid digital-analog speed servomechanism for controlling the speed of a motor, comprising: digital means, including means responsive to motor speed, to derive a digital signal indicative of motor speed-error at sample times; a digital-to-analog converter having an input connected to receive said digital signal; a predictor network having an input connected to the output of said digital-to-analog converter, said predictor network including analog-signal modifYing means having an output whose magnitude reduces with time; reset means controlled by means including said digital means and effective to control said modifying means at each sample time such that the output thereof is reset to the value of the output of said digital-to-analog converter at each sample time; and means connected to receive the output of said modifying means and effective to analog-control the energization of said motor.

Claim 20

A hybrid digital-analog speed servomechanism for controlling the speed of a motor, comprising: digital means, including means responsive to motor speed, to derive a digital signal indicative of motor speed-error at sample times; a digital-to-analog converter having an input connected to receive said digital signal; a predictor network having an input connected to the output of said digital-to-analog converter, said predictor network including analog-signal modifYing means having an output whose magnitude reduces with time; reset means controlled by means including said digital means and effective to control said modifying means at each sample time such that the output thereof is reset to the value of the output of said digital-to-analog converter at each sample time; and means connected to receive the output of said modifying means and effective to analog-control the energization of said motor.

Claim 21

A servomechanism as defined in claim 16 wherein the closed-loop defined by said servomechanism and said motor has a known time constant of response, and wherein said predictor network has a time constant of the order of said known time constant.

Claim 22

A servomechanism as defined in claim 17 wherein said modifying means is a differentiating network.

Claim 23

A servomechanism as defined in claim 18 wherein said differentiating network includes a resistor and a capacitor, with the output thereof being taken from the junction of said capacitor and said resistor.

Claim 24

A servomechanism as defined in claim 19 for controlling the speed of said motor at a nominal value, wherein the output of said signal modifying means has a known nominal value when the speed of said motor is equal to said nominal, wherein said resistor is connected to a potential representative of the nominal output of said digital-to-analog converter, that is, the output thereof when the speed of said motor is at said nominal value; and wherein said reset means is effective to reset the charge of said capacitor to zero at each sample time.

Claim 25

A servomechanism as defined in claim 20 wherein said means responsive to motor speed is a digital tachometer providing an output pulse for each distance unit of movement of said motor, and wherein said digital means includes means to compare the actual period output of said tachometer to a desired period indicative of said nominal motor speed.

Claim 26

A servomechanism as defined in claim 21 wherein said reset means includes normally open switch means connected in parallel with said capacitor, and means controlled by said tachometer to momentarily close said switch means upon the occurrence of each of said tachometer output pulses.

Claim 27

A servomechanism as defined in claim 22 wherein the output pulses of said tachometer occur at relatively long aperiodic intervals during acceleration of said motor, and occur at shorter periodic intervals when the speed of said motor is at nominal, and wherein the voltage at the junction of said capacitor and said resistor during said aperiodic operation decays to the nominal output of said digital-to-analog converter prior to the end of the aperiodic interval.

Claim 28

A servomechanism as defined in claim 23 wherein said periodic interval is of the order of, or longer than, said known time constant.

Claim 29

A servomechanism as defined in claim 24 wherein the time constant of said predictor network is such as to produce a voltage at the junction of said capacitor and said resistor during said periodic operation which approaches said nominal DAC output at the instant of occurrence of a tachometer output pulse.