System and method for pump control and fault detection

• US 6,092,992 A
• Filed: 10/24/1996
• Issued: 07/25/2000
• Est. Priority Date: 10/24/1996
• Status: Expired due to Term

• Current Assignee: Mine Safety Appliances Co LLC (MSA Safety, Inc.)
• Original Assignee: Mine Safety Appliances Company (MSA Safety, Inc.)
• Inventors: Frank, William R., Imblum, Gregory G., Etheridge, Charles H.
• Primary Examiner(s): FREAY, CHARLES GRANT
• Application Number:
  US08/736,466
• Time in Patent Office: 1,370 Days
• Field of Search: 417/42, 417/44.11, 417/45, 417/53
• US Class Current: 417/42
• CPC Class Codes: F04B 2203/0202 Voltage
• CPC Class Codes: F04B 2203/0209 Rotational speed
• CPC Class Codes: F04B 49/06 Control using electricity regulating by means of floats actuating electric switches F04B49/04

Abstract

The present invention provides a system and a method for controlling and detecting faults in a pump system for use in a gas detection device. The system comprises a power source and a switch in operative or electrical connection with the power source. The system further comprises a pump motor in operative connection with the switch such that the pump motor receives energy from the power source when the switch in a first state, and the pump motor does not receive energy from the power source when the switch in a second state. The system preferably also comprises regeneration circuitry in operative connection with the pump motor. The regeneration circuitry operates to redirect energy produced from momentum of the pump motor while the switch is in the second state back to the pump motor. Transmitting circuitry is preferably provided to transmit a motor signal proportional to the speed of the pump motor during the second state of the switch. Preferably, the switch is modulated between the first state and the second state using a processing or control unit such as a microprocessor. The processing unit preferably controls the modulation of switch in response to the motor signal received from the transmitting circuitry.

Claims

1. A system for controlling a pump for use in a gas detection device, the system comprising:

a. a power source;

b. a switch in operative connection with the power source,

c. a pump motor in operative connection with the switch such that the pump motor receives energy from the power source when the switch is in a first state, and the pump motor does not receive energy from the power source when the switch is in a second state;

d. transmitting circuitry adapted to transmit a motor signal proportional to a speed of the pump motor; and

e. a processing unit in operative connection with the switch and the transmitting circuitry, the processing unit adapted to modulate the switch between the first state and the second state, the processing unit being further adapted to control the modulation of the switch in response to the motor signal received from the transmitting circuitry to control the motor;

the processing unit being further adapted to compare the motor signal with a predetermined range of acceptable values to determine if a fault condition exists.

2. The system of claim 1 wherein the processing unit is a microcontroller.

3. The system of claim 1, further comprising regeneration circuitry in operative connection with the pump motor, the regeneration circuitry adapted to redirect energy produced from momentum of the pump motor while the switch is in the second state back to the pump motor.

4. The system of claim 1 wherein the motor signal is approximately the voltage across the pump motor at a predetermined point of time during the second state of the switch.

5. The system of claim 1 wherein the motor signal is approximately the average voltage across the pump motor during the second state of the switch.

6. The system of claim 1 wherein the motor signal is approximately the average voltage across the pump motor during the first state and the second state of the switch.

7. The system of claim 6 wherein the transmitting circuitry comprises a low pass filter adapted to approximately average voltage across the pump motor.

8. The system of claim 1 wherein the processing unit is further adapted to periodically cause the switch to be in the second state for a period of time sufficiently long to cause a stall of the pump motor, the processing unit further being adapted to restart modulation of the switch after the period of time at a predetermined duty cycle, the motor signal during restart of the pump motor providing an indication of whether a fault condition is present.

9. The system of claim 1 wherein the processing unit is adapted to measure a rate of change of modulation required to control the pump motor and to compare the measured rate of change with a predetermined value to determine whether a fault condition is present.

10. The system of claim 1 wherein the processing unit is adapted to compare a duty cycle of modulation required to control the pump motor with at least one of a predetermined maximum duty cycle and a predetermined minimum duty cycle to determine whether a fault condition is present.

11. A method of controlling a pump motor for use in a gas detection instrument, the method comprising the steps of:

a. supplying energy to the pump motor from a power source;

b. modulating a switch connected between the power source and the pump motor between a first state in which the pump motor receives energy from the power source and a second state in which the pump motor does not receive energy from the power source,

c. measuring a motor signal proportional to a speed of the pump motor; and

d. controlling the modulation of the switch in response to the motor signal to control the pump motor.

12. The method of claim 11 further comprising the step of comparing the motor signal with a predetermined range of acceptable values to determine in a fault condition is present.

13. The method of claim 11 further comprising the steps of:

e. periodically causing the switch to be in the second state for a period of time sufficiently long to cause a stall of the pump motor;

f. restarting modulation of the switch after the period of time at a predetermined duty cycle; and

g. measuring the motor signal at a predetermined time after restarting modulation of the switch to determine if a fault condition is present.

14. The method of claim 11, further comprising the steps of:

e. measuring a rate of change of modulation required to control the pump motor; and

f. comparing the measured rate of change with a predetermined value to determine whether a fault condition is present.

15. The method of claim 11, further comprising the step of:

e. comparing a duty cycle of modulation required to control the pump motor with at least one of a predetermined maximum duty cycle and a predetermined minimum duty cycle to determine whether a fault condition is present.

16. The method of claim 11 wherein the motor signal is approximately the voltage across the pump motor at a predetermined point of time during the second state of the switch.

17. The method of claim 11 wherein the motor signal is approximately the average voltage across the pump motor during the second state of the switch.

18. The method of claim 11 wherein the motor signal is approximately the average voltage across the pump motor during the first state and the second state of the switch.

19. The method of claim 11, further comprising the step of redirecting energy produced from rotation of the pump motor when the switch is in the second state back to the pump motor.

20. A system for controlling a pump comprising:

a. a power source;

b. a switch in operative connection with the power source,

c. a pump motor in operative connection with the switch such that the pump motor receives energy from the power source when the switch is in a first state, and the pump motor does not receive energy from the power source when the switch is in a second state;

d. transmitting circuitry adapted to transmit a motor signal proportional to a speed of the pump motor;

e. a processing unit in operative connection with the switch and the transmitting circuitry, the processing unit adapted to modulate the switch between the first state and the second state, the processing unit being further adapted to control the modulation of the switch in response to the motor signal received from the transmitting circuitry to control the motor; and

f. regeneration circuitry in operative connection with the pump motor, the regeneration circuitry adapted to redirect energy produced from momentum of the pump motor while the switch is in the second state back to the pump motor.