Pulse width modulated servo clutch driver

• US 7,430,102 B2
• Filed: 01/04/2006
• Issued: 09/30/2008
• Est. Priority Date: 01/04/2006
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Smith, Jeremy D., Groh, Robert M., Sundquist, Robert S.
• Primary Examiner(s): Sherry; Michael J
• Assistant Examiner(s): MAI, TIEN HUNG
• Application Number:
  US11/324,216
• Publication Number:
  US 20070153444A1
• Time in Patent Office: 1,000 Days
• Field of Search: 361/160
• US Class Current: 361/160
• CPC Class Codes: F16D 2500/1022 Electromagnet
• CPC Class Codes: F16D 2500/3022 Current
• CPC Class Codes: F16D 2500/3028 Voltage
• CPC Class Codes: F16D 2500/501 Relating the actuator
• CPC Class Codes: F16D 2500/70418 Current
• CPC Class Codes: F16D 2500/7109 Pulsed signal; Generating or processing pulsed signals; PWM, width modulation, frequency or amplitude modulation
• CPC Class Codes: F16D 48/064 Control of electrically or electromagnetically actuated clutches F16D48/062, F16D48/068 take precedence
• CPC Class Codes: H01F 2007/1888 using pulse width modulation
• CPC Class Codes: H01F 7/1844 Monitoring or fail-safe circuits for relays H01H47/002
• CPC Class Codes: H02P 15/00 Arrangements for controlling dynamo-electric brakes or clutches controlling speed of dynamo-electric motors by means of a separate brake H02P29/04, vector control H02P21/00 see provisionally also H02K49/00 and H02P29/0022

Abstract

Disclosed is a system and method for controlling a clutch associated with a solenoid using a pulse width modulated (PWM) signal, which keeps the current through the coil constant over a wide temperature range and fluctuations in line voltage. The system may include a voltage source, a switch (such as a FET), a current sensor, and a processor. The system controls the clutch by sampling the voltage source, sampling the current measured by the current sensor, and computing a duty cycle, which is then used to generate a PWM control signal.

Claims

1. A system for controlling a solenoid, comprising:

a voltage source connected to the solenoid;

a current sensor for sensing a current through the solenoid;

a switch for controlling the current through the solenoid;

a processor connected to the voltage source, the current sensor, and the switch, wherein the processor is configured to maintain a substantially constant current through the solenoid to compensate for changes to the voltage source or the solenoid resistance by generating a PWM signal for controlling the current through the solenoid, and wherein the PWM signal is based on a first signal associated with the voltage source and a second signal associated with the current sensor, wherein the processor comprises a computer readable medium encoded with a program for;

acquiring a line signal from the voltage source;

acquiring a sense signal from the current sensor;

computing a duty cycle based on the line signal and the sense signal; and

computing an intermediate resistance based on the line signal, the sense signal, a sense resistance, and a previous duty cycle; and

a switch driver connected between the processor and the switch.

2. The system of claim 1, wherein the computer readable medium is further encoded with a program for sending the duty cycle to the switch driver.

3. The system of claim 1, wherein the computer readable medium is further encoded with a program for estimating a resistance based on a previously estimated resistance, the previous duty cycle, and a gain factor.

4. The system of claim 3, wherein the program for computing the duty cycle includes a program for computing the duty cycle based on the estimated resistance.

5. The system of claim 3, wherein the computer readable medium is further encoded with a program for storing the duty cycle and the estimated resistance.

6. The system of claim 1, further comprising a clutch coupled to the solenoid.

7. The system of claim 6, further comprising a motor coupled to the clutch.

8. The system of claim 1, wherein the current sensor comprises:

a sense resistor; and

an amplifier for amplifying a voltage across the sense resistor.

9. A method for controlling a solenoid, comprising:

acquiring a line signal corresponding to a line voltage;

acquiring a sense signal corresponding to a current flowing through the solenoid;

estimating a resistance based on the line signal, the sense signal, and a previous duty cycle;

computing a duty cycle based on the estimated resistance; and

generating a pulse width modulated signal corresponding to the duty cycle.

10. The method of claim 9, further comprising providing the pulse width modulated signal to a switch connected to the solenoid.

11. The method of claim 10, wherein providing the pulse width modulated signal comprises providing the duty cycle to a switch driver connected to the switch.

12. The method of claim 9, wherein estimating the resistance comprises filtering an intermediate resistance.

13. The method of claim 9, wherein acquiring the sense signal comprises sampling the sense signal at a sample rate based on a time constant corresponding a solenoid coil.

14. The method of claim 13, wherein the sample rate is greater than two times the reciprocal of the time constant.

15. The method of claim 9, wherein estimating the resistance comprises computing a square of the previous duty cycle.

16. The method of claim 9, further comprising storing the estimated resistance and the duty cycle.

17. A system for controlling a solenoid, comprising:

means for providing a voltage;

means for sensing a current flowing through the solenoid;

means for switching current through the solenoid;

means for computing a duty cycle based on the voltage, the current, an estimated resistance, a previously estimated resistance, and a previous duty cycle; and

means for supplying a pulse width modulated signal to the means for switching current, wherein the pulse width modulated signal is based on the duty cycle.