Fault detection circuit for the feedback of a control system

Claim 2

A motor control system which controls the speed of a drive motor in response to the output of a speed sensor coupled to the motor, and fault detection circuit means comprising, in combination: a. switching means coupled to said motor control system and means for maintaining said switching means in a first energization state during the normal operation of said motor control system to enable power to be applied to said motor; b. the speed sensor having an output circuit; c. means for establishing first and second electrical potential levels; d. means for connecting a first side of said output circuit to said first potential level and rectifier means for connecting a second side of said output circuit to said means for energizing said switching means, said rectifier means normally conducting during the normal operation of the motor control system prior to startup of said motor so as to connect said means for maintaininG said switching means through said output circuit to said first potential level; e. electrical conductor means having a substantially higher impedance than said output circuit, means for connecting one side of said electrical conductor to said second electrical potential level and means for connecting said second side of said output circuit to the other side of said electrical conductor, said second potential level having such a value that in the event that said rectifier is forward biased but is not connected through said output circuit to said first potential level, said second potential level causes said means for maintaining said switching means to maintain said switching means in a second energization state so that power is unable to be applied to the motor.

Claim 3

A motor control system which includes a drive motor, a voltage supply for applying energy to said motor in proportion to the desired speed of said motor, and speed sensor means coupled to said motor for providing a speed signal which varies as a function of the actual speed of said motor, and an improved fault detection circuit, comprising, in combination: a. switching means coupled to said motor control system and means for maintaining said switching means in a first energization state during the normal operation of said motor control system to enable the motor to be energized by said motor control system; b. means for coupling a first signal from said voltage supply to said fault detection circuit, said fist signal varying as a function of the energy applied to said motor by said voltage supply; c. means for coupling the speed signal to said fault detection circuit; d. comparison circuit means connected to said means for maintaining said switching means, said comparison circuit responding to the difference between the signal levels of the first signal and the speed signal to cause said means for maintaining said switching means to change the energization state of said switching means when the level of the first signal is at least about a preselected amount greater than the level of the speed signal, thereby causing said motor to decelerate.

Claim 4

A motor control system which includes a drive motor, a voltage supply for applying energy to said motor in proportion to the desired speed of said motor, and speed sensor means coupled to said motor for providing a speed signal which varies as a function of the actual speed of said motor, and an improved fault detection circuit, comprising, in combination: a. switching means coupled to said motor control system and means for maintaining said switching means in a first energization state during the normal operation of said motor control system to enable the motor to be energized by said motor control system; b. means for coupling a first signal from said voltage supply to said fault detection circuit, said fist signal varying as a function of the energy applied to said motor by said voltage supply; c. means for coupling the speed signal to said fault detection circuit; d. comparison circuit means connected to said means for maintaining said switching means, said comparison circuit responding to the difference between the signal levels of the first signal and the speed signal to cause said means for maintaining said switching means to change the energization state of said switching means when the level of the first signal is at least about a preselected amount greater than the level of the speed signal, thereby causing said motor to decelerate.

Claim 5

The improved motor control system according to claim 2 in which said means for coupling a speed signal includes a capacitor circuit for preventing transient changes in the speed signal level from affecting said comparison circuit.

Claim 6

The improved motor control system according to claim 2 which also includes means responsive to the level of the speed signal and connected to said means for maintaining said switching means to cause said switching means to be maintained in the second energization state when the speed signal is greater than a preselected level.

Claim 7

The improved motor control system according to claim 2 wherein said speed sensor has an output circuit having a first side and a second side and said motor control system includes means for establishing first and second electrical potential levels, means for connecting the first side of said output circuit to said first source of electrical potential, and rectifier means for connecting the second side of said output circuit to said means for maintaining said switching means, said rectifier means normally conducting during normal operation of said motor control system prior to startup of said motor so as to connect said means for maintaining switching means through said output circuit to said first potential level; electrical conductor means having a substantially higher impedance than said output circuit, means for connecting one side of said electrical conductor to said second electrical potential level and means for connecting said second side of said output circuit to the other side of said electrical conductor, said second potential level having such a value that in the event that said rectifier is forward biased but is not connected through said output circuit to said first potential level, said second potential level causes said means for maintaining said switching meaNs to maintain said switching means in a second excitation state so that power is unable to be applied to said motor.

Claim 8

For use in a closed-loop, regulated control system which controls a preselected parameter of a load in response to the output of a sensor of this parameter, the output normally varying as a function of the preselected parameter as the energization level of the load changes, fault detection circuit means comprising, in combination: a. switching means coupled to the motor control system and means for maintaining the switching means in a first excitation state during the normal operation of the control system to enable power to be applied to the load; b. means for sensing a preselected parameter of the load, said means for sensing having an output circuit, c. means for establishing first and second electrical potential levels; d. first means for connecting a first side of the output circuit to said first potential level and second means for connecting a second side of said output circuit to said means for energizing said switching means, said second means normally conducting current during the normal operation of the control system prior to the energization of the load so as to connect said means for maintaining said switching means through said output circuit to said first potential level; e. electrical conductor means having a substantially higher impedance than said output circuit, third means for connecting one side of said electrical conductor to said second potential level and fourth means for connecting said second side of said output circuit to the other side of said electrical conductor means, said second potential level having such a value that in the event said second means is conducting current but said output circuit has been interrupted, said second potential level causes said means for maintaining said switching means to maintain said switching means in a second excitation state at which electrical energy is unable to be applied to the load.

Claim 9

For use in a closed-loop, regulated control system which controls a preselected parameter of a load in response to the output of a sensor of this parameter, the output normally varying as a function of the preselected parameter as the energization level of the load changes, fault detection circuit means comprising, in combination: a. switching means coupled to the motor control system and means for maintaining the switching means in a first excitation state during the normal operation of the control system to enable power to be applied to the load; b. means for sensing a preselected parameter of the load, said means for sensing having an output circuit, c. means for establishing first and second electrical potential levels; d. first means for connecting a first side of the output circuit to said first potential level and second means for connecting a second side of said output circuit to said means for energizing said switching means, said second means normally conducting current during the normal operation of the control system prior to the energization of the load so as to connect said means for maintaining said switching means through said output circuit to said first potential level; e. electrical conductor means having a substantially higher impedance than said output circuit, third means for connecting one side of said electrical conductor to said second potential level and fourth means for connecting said second side of said output circuit to the other side of said electrical conductor means, said second potential level having such a value that in the event said second means is conducting current but said output circuit has been interrupted, said second potential level causes said means for maintaining said switching means to maintain said switching means in a second excitation state at which electrical energy is unable to be applied to the load.

Claim 10

For use in a closed-loop, regulated control system which includes a load, a voltage supply for applying electrical energy to said load in proportion to the level of a preselected parameter of said load, and means for providing a feedback signal which varies as a function of the preselected parameter of the load, an improved fault detection circuit, comprising, in combination: a. switching means coupled to said control system and means for maintaining said switching means in a first excitation state during the normal operation of said control system to enable said load to be energized by said control system; b. means for coupling a first signal from said voltage supply to said fault detection circuit, said first signal varying as a function of the energy applied to the load by said voltage supply; c. means for coupling a feedback signal to said fault detection circuit; and d. comparison circuit means connected to said means for maintaining said switching means, said comparison circuit responding to the difference between the signal levels of the first signal and the feedback signal to cause said means for maintaining said switching means to change the excitation state of said switching means when the level of said first signal is at least a preselected amount greater than the level of the feedback signal, thereby decreasing the energization of the load.

Claim 11

For use in a closed-loop, regulated control system which includes a load, a voltage supply for applying electrical energy to said load in proportion to the level of a preselected parameter of said load, and means for providing a feedback signal which varies as a function of the preselected parameter of the load, an improved fault detection circuit, comprising, in combination: a. switching means coupled to said control system and means for maintaining said switching means in a first excitation state during the normal operation of said control system to enable said load to be energized by said control system; b. means for coupling a first signal from said voltage supply to said fault detection circuit, said first signal varying as a function of the energy applied to the load by said voltage supply; c. means for coupling a feedback signal to said fault detection circuit; and d. comparison circuit means connected to said means for maintaining said switching means, said comparison circuit responding to the difference between the signal levels of the first signal and the feedback signal to cause said means for maintaining said switching means to change the excitation state of said switching means when the level of said first signal is at least a preselected amount greater than the level of the feedback signal, thereby decreasing the energization of the load.

Claim 12

In a drive system including a motor and a motor control system for controlling power input to the motor so as to thereby control the speed of the motor, a fault detection system comprising: a. switching means shiftable between a first condition interconnecting the control system and the motor to permit normal operation of the motor in response to the motor control system and a second condition in which energization of the motor is prevented, means biasing said switching means to aid second condition, means responsive to current flow therein to shift said switching means to said first cOndition, means responsive to the actual speed of the motor for producing a first fault detection signal proportional to the speed of the motor, means responsive to the output of said motor control system for producing a second fault detection signal proportional to the magnitude of said output, a power supply, and circuit means interconnecting said power supply, said current responsive means, said actual speed responsive means, and said motor control system output responsive means such that current flows through said current responsive means to permit operation of the motor only so long as the impedance of said actual speed responsive means remains below a predetermined level and the steady state second fault detection signal does not exceed the first fault detection signal by more than a predetermined amount.

Claim 13

In a drive system including a motor and a motor control system for controlling power input to the motor so as to thereby control the speed of the motor, a fault detection system comprising: a. switching means shiftable between a first condition interconnecting the control system and the motor to permit normal operation of the motor in response to the motor control system and a second condition in which energization of the motor is prevented, means biasing said switching means to aid second condition, means responsive to current flow therein to shift said switching means to said first cOndition, means responsive to the actual speed of the motor for producing a first fault detection signal proportional to the speed of the motor, means responsive to the output of said motor control system for producing a second fault detection signal proportional to the magnitude of said output, a power supply, and circuit means interconnecting said power supply, said current responsive means, said actual speed responsive means, and said motor control system output responsive means such that current flows through said current responsive means to permit operation of the motor only so long as the impedance of said actual speed responsive means remains below a predetermined level and the steady state second fault detection signal does not exceed the first fault detection signal by more than a predetermined amount.