High gain null-balance servo system

Claim 2

An improved null-balance servo system for measuring an unknown electrical quantity in the form of an input signal, said servo system having a first loop providing overall system feedback and second and third loops forming sub-loops within said first loop, said system comprising: a means for producing an error signal related to the difference between an input signal and a signal for restoring balance to said system; a DC pre-amplifier for amplifying said error signal; a DC post-amplifier coupled to the output of said pre-amplifier; an adjustable circuit element having an output coupled to said means for producing an error signal; a DC motor coupled between the output of said post-amplifier and said adjustable circuit element to generate said restoring signal in response to movement of said adjustable circuit element; a proportional plus derivative means coupled to the output of said adjustable circuit element for producing a feedback signal including a velocity component, said last named means being interposed between said adjustable circuit element and said means for producing an error signal, and a reactive feedback means coupled between said proportional plus derivative means and the input of said post-amplifier to establish said second and third loops, said second loop including said pre-amplifier, and said third loop including said post-amplifier, said motor, said adjustable circuit element, said proportional plus derivative means and said reactive means, said third loop acting like an integrator with respect to said second loop.

Claim 3

The null-balance servo system of claim 1 wherein said post-amplifier includes an output, a non-inverting input, and an inverting input and said null-balance servo system further comprises another reactive feedback means from the output of said post-amplifier to the inverting input of said post-amplifier, said post-amplifier and said reactive feedback path acting like an integrator with an integrator gain sufficiently high for the third loop to act like an integrator with respect to the second loop.

Claim 4

The null-balance servo system of claim 2 wherein a first integrator time constant for said third loop is proportional to said reactive feedback means.

Claim 5

The null-balance servo system of claim 3 wherein a second integrator time constant for said post-amplifier in combination with said second reactive feedback means is proportional to said other reactive feedback means, said integrator gain being inversely proportional to said second integrator time constant.

Claim 6

The null-balance servo system of claim 4 wherein said second integrator time constant is less than said first integrator time constant.

Claim 7

The null-balance servo system of claim 1 further comprising resistive means coupling the output of said pre-amplifier to the input of said post-amplifier.

Claim 8

The null-balance servo system of claim 6 wherein said reactive feedback means includes a capacitive means.

Claim 9

The null-balance servo system of claim 7 including shunt capacitive means in combination with said resistive means to form a low pass filter at the input of said post-amplifier.

Claim 10

The null-balance servo system of claim 6 wherein said reactive feedback means comprises inductive means.

Claim 11

The null-balance servo system of claim 1 wherein said reactive feedback means comprises capacitive means.

Claim 12

The null-balance servo system of claim 1 wherein said reactive feedback means comprises inductive means.

Claim 13

The null-balaNce servo system of claim 1 wherein said proportional plus derivative means comprises a feedback amplifier and lag network in the feedback of said amplifier.

Claim 14

The null-balance servo system of claim 1 wherein said third loop includes at least one integrator in cascade with said DC motor.

Claim 15

A high-speed null-balance servo system having optimal small signal response for measuring an unknown electrical quantity in the form of an input signal comprising: a means for producing an error signal related to the difference between an input signal and a signal for restoring balance to said system; a DC pre-amplifier for amplifying said error signal; a DC post-amplifier coupled to the output of said pre-amplifier; an adjustable circuit element having an output coupled to said means for producing an error signal; a DC motor connected to the output of said post-amplifier and mechanically coupled to said adjustable circuit element to generate said restoring signal in response to movement of said adjustable circuit element; a proportional plus derivative means coupled to the output of said adjustable circuit element for producing a feedback signal including a velocity component, said proportional plus derivative means establishing a first dominant system time constant; and a reactive means coupling said feedback signal to the input of said post-amplifier so as to establish a second dominant system time constant proportional to said reactive means.

Claim 16

A high-speed null-balance servo system having optimal small signal response for measuring an unknown electrical quantity in the form of an input signal comprising: a means for producing an error signal related to the difference between an input signal and a signal for restoring balance to said system; a DC pre-amplifier for amplifying said error signal; a DC post-amplifier coupled to the output of said pre-amplifier; an adjustable circuit element having an output coupled to said means for producing an error signal; a DC motor connected to the output of said post-amplifier and mechanically coupled to said adjustable circuit element to generate said restoring signal in response to movement of said adjustable circuit element; a proportional plus derivative means coupled to the output of said adjustable circuit element for producing a feedback signal including a velocity component, said proportional plus derivative means establishing a first dominant system time constant; and a reactive means coupling said feedback signal to the input of said post-amplifier so as to establish a second dominant system time constant proportional to said reactive means.

Claim 17

The null-balance servo system of claim 14 wherein said first dominant time constant established by said proportional plus derivative means and said second dominant system time constant established by said reactive means are substantially equal.

Claim 18

A null-balance servo system having an optimal small signal response for measuring an unknown electrical quantity in the form of an input signal comprising: a means for producing an error signal relating to the difference between an input signal and an overall feedback signal for restoring balance to said system; a DC pre-amplifier for amplifying said error signal; a DC post-amplifier coupled to the output of said pre-amplifier; a means for producing feedback signals comprising a DC motor and associated circuitry connected to the output of said post-amplifier and an adjustable circuit element mechanically coupled to said motor; an outer loop feedback means coupling said adjustable circuit element of said means for producing feedback signal to said means for producing an error signal so as to apply said overall system feedback signal to said means for producing an error signal; and an inner loop feedback means including reactive means for coupling said means for producing feedback signals to the input of said post-amplifier and applying a velocity feedback signal component to the input of said post-amplifier and an acceleration feedback signal component to the input of said post-amplifier, said acceleration feedback signal component being substantially free of the voltage drop across the motor resistance.

Claim 19

A null-balance servo system having an optimal small signal response for measuring an unknown electrical quantity in the form of an input signal comprising: a means for producing an error signal relating to the difference between an input signal and an overall feedback signal for restoring balance to said system; a DC pre-amplifier for amplifying said error signal; a DC post-amplifier coupled to the output of said pre-amplifier; a means for producing feedback signals comprising a DC motor and associated circuitry connected to the output of said post-amplifier and an adjustable circuit element mechanically coupled to said motor; an outer loop feedback means coupling said adjustable circuit element of said means for producing feedback signal to said means for producing an error signal so as to apply said overall system feedback signal to said means for producing an error signal; and an inner loop feedback means including reactive means for coupling said means for producing feedback signals to the input of said post-amplifier and applying a velocity feedback signal component to the input of said post-amplifier and an acceleration feedback signal component to the input of said post-amplifier, said acceleration feedback signal component being substantially free of the voltage drop across the motor resistance.

Claim 20

The system of claim 16 wherein said means for producing feedback signals further comprises a proportional plus derivative means connected to the output of said adjustable circuit element, said outer loop feedback means being coupled to the output of said proportional plus derivative means.

Claim 21

The system of claim 17 wherein said inner loop feedback means is also coupled to the output of said proportional plus derivative means.

Claim 22

The system of claim 16 wherein said inner loop feedback means is coupled to said associated circuitry of said DC motor and said adjustable circuit element so as to apply said velocity and acceleration feedback signal components to the input of said post-amplifier.

Claim 23

The system of claim 19 wherein said inner loop feedback means comprises a first reactive feedback path from said adjustable circuit element to said post-amplifier for said velocity signal component And a second reactive feedback path from said associated circuitry of said DC motor to said post-amplifier for said acceleration signal component.

Claim 24

The system of claim 20 wherein said associated circuitry comprises a bridge including said motor as an arm in said bridge, said second reactive feedback path being connected to said bridge.

Claim 25

The system of claim 19 wherein said reactive means of said inner loop feedback means comprises a single reactive feedback path coupled to said adjustable circuit element and said associated circuitry of said motor.

Claim 26

The system of claim 16 further comprising a phase switching circuit wherein said associated circuitry comprises switching transistors coupled to and controlled by said switching circuit for providing a switch mode operation of said motor.

Claim 27

An improved null-balance servo system for measuring an unknown electrical quantity in the form of an input signal having an overall positional feedback loop, a velocity feedback inner loop and an acceleration feedback inner loop of high sub-loop bandwidth for significantly reducing the effect of variations of motor resistance and significantly reducing the effect of variations of motor torque sensitivity, comprising: means for producing an error signal relating to the difference between an input signal and an overall feedback signal for restoring balance to said system; a DC pre-amplifier for amplifying said error signal; a DC post-amplifier coupled to the output of said pre-amplifier; means for producing feedback signals including a DC motor having an electrical input connected to the output of said post-amplifier, and an adjustable circuit element having a mechanical input coupled to the mechanical output of said motor and a variable electrical output producing an overall positional feedback signal; overall positional feedback loop means coupling the output of said adjustable circuit element to the input of said pre-amplifier; and inner loop feedback means coupling the output of said adjustable circuit element in said velocity feedback inner loop and said motor electrical input to the input of said post-amplifier in said acceleration feedback inner loop so as to respectively apply a velocity feedback signal component and an acceleration feedback signal component to the input of said post-amplifier, said acceleration feedback signal component being substantially independent of the voltage drop across the motor resistance.

Claim 28

An improved null-balance servo system for measuring an unknown electrical quantity in the form of an input signal having an overall positional feedback loop, a velocity feedback inner loop and an acceleration feedback inner loop of high sub-loop bandwidth for significantly reducing the effect of variations of motor resistance and significantly reducing the effect of variations of motor torque sensitivity, comprising: means for producing an error signal relating to the difference between an input signal and an overall feedback signal for restoring balance to said system; a DC pre-amplifier for amplifying said error signal; a DC post-amplifier coupled to the output of said pre-amplifier; means for producing feedback signals including a DC motor having an electrical input connected to the output of said post-amplifier, and an adjustable circuit element having a mechanical input coupled to the mechanical output of said motor and a variable electrical output producing an overall positional feedback signal; overall positional feedback loop means coupling the output of said adjustable circuit element to the input of said pre-amplifier; and inner loop feedback means coupling the output of said adjustable circuit element in said velocity feedback inner loop and said motor electrical input to the input of said post-amplifier in said acceleration feedback inner loop so as to respectively apply a velocity feedback signal component and an acceleration feedback signal component to the input of said post-amplifier, said acceleration feedback signal component being substantially independent of the voltage drop across the motor resistance.

Claim 29

The system of claim 24 wherein said means for producing feedback signals further comprises a bridge wherein said motor forms one leg of said bridge on one side of said bridge, said inner loop feedback means including a reactive means coupled to a terminal on the opposite side of said bridge so as to apply said acceleration feedback signal component to the input of said post-amplifier.

Claim 30

The system of claim 24 wherein said means for producing feedback signals further comprises a differential amplifier means and an impedance connected in series with said motor for generating a signal representing the voltage drop across the motor resistance, said differential amplifier means coupled to said motor and said impedance for generating a velocity signal representative of the motor voltage minus the voltage drop across the motor resistance, said inner loop feedback means including reactive means coupling the output of said differential amplifier means to the input of said post-amplifier to apply said acceleration feedback signal component to the input of said post-amplifier.

Claim 31

The system of claim 24 wherein said means for producing feedback signals further comprises a plurality of interconnected switching transistors and pulse generating means having an output coupled to said post-amplifier and an input coupled to said switching transistors for generating a pulsed output from said switching transistors which is a function of the output from said post-amplifier, said pulsed output being applied to said motor.

Claim 32

The system of claim 27 wherein said means for producing said feedback signal further comprises a bridge wherein said motor forms one leg of said bridge, said inner loop feedback means including reactive means coupled between said bridge and the input of said post-amplifier so as to apply said acceleration feedback signal component to the input of said post-amplifier.

Claim 33

The system of claim 27 wherein said switching transistors form a bridge, said means for producing said feedback signals further comprising an impedance connected in series with said motor and across said bridge and differential amplifier means coupled to said motor and said impedance for generating a velocity signal representative of the motor voltage minus the voltage drop across the motor impedance, said inner loop feedback means including a reactive means coupling the output of said differential amplifier to the input of said post-amplifier for applying said acceleration signal components thereto.