System for control of an electromagnetic actuator

• US 6,249,418 B1
• Filed: 01/27/1999
• Issued: 06/19/2001
• Est. Priority Date: 01/27/1999
• Status: Expired due to Fees

• Current Assignee: Gary Bergstrom
• Original Assignee: Gary Bergstrom
• Inventors: Bergstrom, Gary
• Primary Examiner(s): Leja, Ronald W.
• Application Number:
  US09/238,344
• Time in Patent Office: 874 Days
• Field of Search: 361/139, 361/143, 361/144, 361/146, 361/152, 361/153, 361/159, 361/160, 361/170, 361/171, 361/178, 361/154, 123/490, 123/494, 123/90.11, 307/86, 307/87, 307/101, 307/143, 307/145, 307/142
• US Class Current: 361/152
• CPC Class Codes: F01L 2009/4086 Soft landing, e.g. applying braking current; Levitation of armature close to core surface
• CPC Class Codes: F01L 9/20 by electric means
• CPC Class Codes: F02D 13/0253 Fully variable control of valve lift and timing using camless actuation systems such as hydraulic, pneumatic or electromagnetic actuators, e.g. solenoid valves
• CPC Class Codes: F02D 2041/001 for engines with variable valve actuation
• CPC Class Codes: F02D 41/20 Output circuits, e.g. for controlling currents in command coils
• CPC Class Codes: F16C 32/0446 Determination of the actual position of the moving member, e.g. details of sensors
• CPC Class Codes: F16C 32/0451 Details of controllers, i.e. the units determining the power to be supplied, e.g. comparing elements, feedback arrangements with P.I.D. control
• CPC Class Codes: H01F 7/1844 Monitoring or fail-safe circuits for relays H01H47/002
• CPC Class Codes: H01H 47/325 by switching regulator

Abstract

A system for controlling the force and/or motion of an electromagnetic actuator. The actuator could be a solenoid, relay, or levitating device. The drive to the coil can be linear or switching, voltage or current and the sensors measuring the system can be as simple as just a current sensor monitoring the coil current or a flux sensor. Continuous control of position can be achieved allowing magnetic levitation or the soft landing of the moving element.

Claims

1. A measurement system for detecting translational position of a moving element of an electrically actuated electromagnetic transducer, said measurement system comprising:

drive means, for setting an electrical drive signal that is applied to a coil of said transducer, said drive signal having a known response to an input signal, and said drive signal causing an electromagnetic actuation force on said moving element;

sense means, for sensing a single electromagnetic parameter of said transducer, wherein said single electromagnetic parameter is responsive to said electromagnetic actuation force and to said position; and

computation means, for determining a measure of said position from said drive signal and said single electromagnetic parameter.

2. The system of claim 1, wherein:

said electrical drive signal is a voltage; and

,

said single electromagnetic parameter is a current.

3. The system of claim 2, wherein:

said drive means includes switching means for generating a pulse width modulated output; and

said computation means includes means for computing said electrical drive signal from a duty cycle thereof and a known power supply voltage.

4. The system of claim 2, wherein:

a resistive impedance associated with said transducer and said drive means is known;

said computation means includes means to compute an inductive voltage associated with change in a magnetic flux in said transducer,

using said voltage, said current, and said resistive impedance;

said computation means further includes means to integrate said change in said magnetic flux over time to compute a total magnetic flux; and

said determining said measure of said position includes computing a ratio of said current and said total magnetic flux.

5. The system of claim 1, wherein:

said electrical drive signal is a voltage; and

,

said single electromagnetic parameter is a magnetic flux.

6. The system of claim 1, wherein:

said electrical drive signal is a current; and

,

said single electromagnetic parameter is a voltage.

7. The system of claim 1, wherein:

said electrical drive signal is a current; and

said single electromagnetic parameter is a magnetic flux.

8. The system of claim 1, wherein said computation means further includes means for determining, from said electrical drive signal and said single electromagnetic parameter, a measure of electromagnetic force in said transducer.

9. The system of claim 8, further comprising a control system for controlling said position, including:

error signal generation means for comparing a desired controlled position to said measure of said position; and

feedback means, using said error signal in setting said measure of electromagnetic force in the setting of said input signal, for causing said position to be driven towards said desired controlled position.

10. The system of claim 9, wherein when said position reaches a position of mechanical contact said control system causes the step of reaching said position of mechanical contact to take place at a controlled impact velocity.

11. The system of claim 9, wherein said control system further includes a closed loop controller associated with said error signal generation means and said feedback means.

12. The system of claim 1, further comprising a control system for controlling said position, including:

error signal generation means for comparing a desired controlled position to said measure of said position; and

feedback means, using said error signal in setting said input signal, for causing said position to be driven towards said desired controlled position.

13. The system of claim 12, wherein when said position reaches a position of mechanical contact said control system causes the step of reaching said position of mechanical contact to take place at a controlled impact velocity.

14. The system of claim 1, further comprising:

an error function, based on proper operation of said system in conjunction with a specific instance of said transducer, said error function describing a departure of a computed parameter of the system from a value of said computed parameter that is consistent with said proper operation; and

,

means for correcting said computed parameter to reduce the magnitude of said error function.

15. The system of claim 14, wherein:

said computed parameter is magnetic flux;

said magnetic flux is computed in the short term from time-integration of an inductive voltage;

said error function indicates drift of said magnetic flux from a correct value, due to error in said time-integration; and

,

said means for correcting reduces said error in said time-integration.

16. The system of claim 15 wherein:

said error function is a difference between a desired value of said input signal and the actual value of said input signal as determined by feedback through said system near equilibrium; and

,

a multiple of said error function is summed with said inductive voltage at the input for said time-integration.

17. The system of claim 15, wherein:

said error function is a difference between a desired value of said input signal and the actual value of said input signal as determined by feedback through said system near equilibrium; and

said error function is used to correct an estimate of electrical resistance, said estimate being used to estimate said inductive voltage.

18. A system for actuation and control of a mechanical motion in an electromagnetic transducer, said system comprising:

drive means, responsive in a known way to an input signal by setting an electrical drive signal that is applied to said transducer, causing an electromagnetic actuation force;

sense means, for sensing a single electromagnetic parameter of said transducer responsive to said electromagnetic actuation force and said mechanical motion;

computation means for determining, from said electrical drive signal and said single electromagnetic parameter, a measure of said mechanical motion;

control means, utilizing said measure of said mechanical motion to generate said input signal, for controlling said mechanical motion;

an error function, based on proper operation of said system in conjunction with a specific instance of said transducer, said error function describing a departure of a computed parameter of said system from a value of said computed parameter that is consistent with said proper operation; and

,

means for correcting said computed parameter to reduce the magnitude of said error function.

19. The system of claim 18, wherein:

said computed parameter is said magnetic flux;

said magnetic flux is computed in the short term from time-integration of an inductive voltage;

said error function indicates drift of said magnetic flux from a correct value, due to error in said time-integration; and

,

said means for correcting reduces said error in said time-integration.

20. The system of claim 19, wherein:

said error function is a difference between a desired value of said input signal and the actual value of said input signal as determined by feedback through said system near equilibrium; and

,

a multiple of said error function is summed with said inductive voltage at the input for said time-integration.

21. The system of claim 19, wherein:

said error function is a difference between a desired value of said input signal and the actual value of said input signal as determined by feedback through said system near equilibrium; and

said error function is used to correct an estimate of electrical resistance, said estimate being used to estimate said inductive voltage.

22. A system for actuation and control of a mechanical motion in an electromagnetic transducer, said system comprising:

drive means, responsive in a known way to an input signal by setting an electrical drive signal that is applied to said transducer, causing an electromagnetic actuation force;

sense means, for sensing a single electromagnetic parameter of said transducer responsive to said electromagnetic actuation force and said mechanical motion;

computation means for determining, from said electrical drive signal and said single electromagnetic parameter, a measure of said mechanical motion;

control means, utilizing said measure of said mechanical motion to generate said input signal, for controlling said mechanical motion;

a mechanical limit of said mechanical motion;

detection means, for determining a value of said input signal when said mechanical motion approaches said mechanical limit under approximate force-balance conditions; and

,

latching means, for holding said mechanical motion in the vicinity of said mechanical limit with a fixed said input signal based on said value.