Control system with variable pulse rate

Claim 2

A feedback control system comprising an on-off control device for maintaining a variable quantity at a predetermined value, means for developing a signal voltage corresponding to the value of said variable quantity, means for developing a carrier voltage, means responsive to the signal voltage and the carrier voltage for developing a switching voltage having a repetition rate which varies inversely with the deviation of the signal voltage from a desired value thereof, means for comparing said switching voltage with a reference voltage and producing a voltage pulse having a duration corresponding to the time the switching voltage is greater than the reference voltage, and means responsive to said voltage pulse for energizing said control device so that it is maintained in an on condition for the duration of said pulse and in an off condition in the absence of said pulse whereby said control device is operated at a variable rate between the on and off conditions, said rate being relatively low when the deviation is high and being relatively high when said deviation is low.

Claim 3

A feedback control system comprising; an on-off control device adapted to maintain a variable quantity at a regulated value, a pulse width modulator responsive to a switching voltage for producing control pulses each of which has a duration corresponding to the time the switching voltage exceeds a predetermined amplitude, means for producing an error voltage corresponding to the deviation of the variable quantity from a desired value, means for producing a carrier voltage having a gaussian random amplitude distribution and a substantially uniform spectral density over a limited bandwidth, and means for combining the error voltage and the carrier voltage to produce said switching voltage whereby said control pulses have a pulse repetition rate which increases as the error voltage decreases and whereby said switching voltage exceeds said predetermined amplitude by an amount which increaSes with the value of said error voltage.

Claim 4

A feedback control system comprising; an on-off control device adapted to maintain a variable quantity at a regulated value, a pulse width modulator responsive to a switching voltage for producing control pulses each of which has a duration corresponding to the time the switching voltage exceeds a predetermined amplitude, means for producing an error voltage corresponding to the deviation of the variable quantity from a desired value, means for producing a carrier voltage having a gaussian random amplitude distribution and a substantially uniform spectral density over a limited bandwidth, and means for combining the error voltage and the carrier voltage to produce said switching voltage whereby said control pulses have a pulse repetition rate which increases as the error voltage decreases and whereby said switching voltage exceeds said predetermined amplitude by an amount which increaSes with the value of said error voltage.

Claim 5

The invention as defined in claim 2 wherein said control device is an electromechanical contactor having a useful life limited by the number of switching cycles, said cycle rate being dependent upon the pulse rate of said modulator.

Claim 6

The invention as defined in claim 3 wherein said variable quantity is the temperature of a furnace or the like and the means for producing the error voltage includes a thermocouple in said furnace.

Claim 7

For use in a control system, a pulse width modulator responsive to a switching voltage for producing control pulses each having a duration corresponding to the time the switching voltage exceeds a predetermined amplitude, means for producing a signal voltage corresponding to the value of temperature of a controlled medium, selective means for amplifying the noise voltage generated by said thermocouple, means for developing a set point voltage corresponding to the desired value of said temperature, means for combining said signal voltage and said set point voltage for developing an error voltage corresponding to the deviation of the temperature from said desired value, and means responsive to the error voltage and said amplified noise voltage and adapted to produce an output when the summation thereof exceeds a reference voltage whereby said control pulses therefrom will have a pulse rate which increases as the error voltage decreases.

Claim 8

For use in a control system, a pulse width modulator responsive to a switching voltage for producing control pulses each having a duration corresponding to the time the switching voltage exceeds a predetermined amplitude, means for producing a signal voltage corresponding to the value of temperature of a controlled medium, selective means for amplifying the noise voltage generated by said thermocouple, means for developing a set point voltage corresponding to the desired value of said temperature, means for combining said signal voltage and said set point voltage for developing an error voltage corresponding to the deviation of the temperature from said desired value, and means responsive to the error voltage and said amplified noise voltage and adapted to produce an output when the summation thereof exceeds a reference voltage whereby said control pulses therefrom will have a pulse rate which increases as the error voltage decreases.

Claim 9

The invention as defined in claim 5 wherein said noise has a gaussian random amplitude distribution over a limited bandwidth.

Claim 10

A feedback control system comprising an on-off control device for maintaining the temperature of a controlled medium at a predetermined value, a thermocouple in said medium for producing a signal voltage corresponding to the temperature thereof, selective amplifying means connected to said thermocouple for amplifying the inherent noise of said thermocouple, means for developing a set point voltage corresponding to the desired value of said temperature, means for combining said signal voltage and said set point voltage for developing an error voltage corresponding to the deviation of the temperature from the desired value, means responsive to the error voltage and said amplified noise voltage and adapted to produce an output pulse when the summation thereof exceeds a reference voltage whereby the pulse rate generated by said last-named means increases as said error voltage decreases, and means connected with said last-mentioned means for energizing said control device to cause it to assume an on condition for the duration of each said pulse and an off position condition in the absence of said pulse.

Claim 11

A feedback control system comprising an on-off control device for maintaining the temperature of a controlled medium at a predetermined value, a thermocouple in said medium for producing a signal voltage corresponding to the temperature thereof, selective amplifying means connected to said thermocouple for amplifying the inherent noise of said thermocouple, means for developing a set point voltage corresponding to the desired value of said temperature, means for combining said signal voltage and said set point voltage for developing an error voltage corresponding to the deviation of the temperature from the desired value, means responsive to the error voltage and said amplified noise voltage and adapted to produce an output pulse when the summation thereof exceeds a reference voltage whereby the pulse rate generated by said last-named means increases as said error voltage decreases, and means connected with said last-mentioned means for energizing said control device to cause it to assume an on condition for the duration of each said pulse and an off position condition in the absence of said pulse.

Claim 12

the invention as defined in claim 7 wherein said control device is an electromechanical contactor having a useful life determined by the number of cycles of operation.

Claim 13

In a control system, means for developing a signal voltage corresponding to the value of a variable quantity, means for developing a set point voltage corresponding to the desired value of said variable quantity, means for combining said signal voltage and said set point voltage to develop an error voltage corresponding to the deviation from the desired value, a variable frequency oscillator for developing a carrier voltage, means responsive to the error voltage and connected with the oscillator for varying the frequency thereof inversely with the error voltage, and means for comparing said carrier voltage with said error voltage and producing a voltage pulse having a duration corresponding to the time the carrier voltage plus said error voltage is greater than a reference voltage.

Claim 14

In a control system, means for developing a signal voltage corresponding to the value of a variable quantity, means for developing a set point voltage corresponding to the desired value of said variable quantity, means for combining said signal voltage and said set point voltage to develop an error voltage corresponding to the deviation from the desired value, a variable frequency oscillator for developing a carrier voltage, means responsive to the error voltage and connected with the oscillator for varying the frequency thereof inversely with the error voltage, and means for comparing said carrier voltage with said error voltage and producing a voltage pulse having a duration corresponding to the time the carrier voltage plus said error voltage is greater than a reference voltage.

Claim 15

A feedback control system comprising an on-off control device for maintaining a variable quantity at a regulated value, means for producing a signal voltage corresponding to the value of the variable quantity, means for developing a set point voltage corresponding to the desired value of said variable quantity, means for combining said signal voltage and said set point voltage for Developing an error voltage corresponding to the deviation of the variable quantity from said desired value, a voltage controlled variable frequency oscillator adapted to produce a carrier voltage, means including a nonlinear circuit device for applying said error voltage to said voltage controlled oscillator whereby said carrier voltage has a frequency which varies in a nonlinear fashion and inversely as a function of said error voltage, comparator means having one input connected to the said variable frequency oscillator and another input connected with said error voltage and adapted to produce an output pulse having a duration corresponding to the time the carrier voltage plus said error voltage is greater than a reference voltage whereby said output pulses have a pulse rate which increases as said error voltage decreases and means connected with said comparator means for energizing said control means to cause it to assume an on condition throughout the duration of each pulse and to assume an off position in the absence of a pulse.

Claim 16

A feedback control system comprising an on-off control device for maintaining a variable quantity at a regulated value, means for producing a signal voltage corresponding to the value of the variable quantity, means for developing a set point voltage corresponding to the desired value of said variable quantity, means for combining said signal voltage and said set point voltage for Developing an error voltage corresponding to the deviation of the variable quantity from said desired value, a voltage controlled variable frequency oscillator adapted to produce a carrier voltage, means including a nonlinear circuit device for applying said error voltage to said voltage controlled oscillator whereby said carrier voltage has a frequency which varies in a nonlinear fashion and inversely as a function of said error voltage, comparator means having one input connected to the said variable frequency oscillator and another input connected with said error voltage and adapted to produce an output pulse having a duration corresponding to the time the carrier voltage plus said error voltage is greater than a reference voltage whereby said output pulses have a pulse rate which increases as said error voltage decreases and means connected with said comparator means for energizing said control means to cause it to assume an on condition throughout the duration of each pulse and to assume an off position in the absence of a pulse.