Method of compensation for flux control of an electromechanical actuator

• US 6,285,151 B1
• Filed: 11/05/1999
• Issued: 09/04/2001
• Est. Priority Date: 11/06/1998
• Status: Expired due to Fees

• Current Assignee: Siemens Automotive Corporation (Siemens AG)
• Original Assignee: Siemens Automotive Corporation (Siemens AG)
• Inventors: Czimmek, Perry Robert, Wright, Danny Orlen
• Primary Examiner(s): IP, SHIK LUEN PAUL
• Application Number:
  US09/434,513
• Time in Patent Office: 669 Days
• Field of Search: 318/139, 318/560, 318/129, 318/135, 318/561-699, 361/167, 361/210, 361/154, 361/160, 361/159, 361/170, 361/199, 361/187, 123/90.11, 123/490, 123/90.12, 335/256, 335/266, 251/129.01
• US Class Current: 318/560
• CPC Class Codes: F01L 2201/00 Electronic control systems; Apparatus or methods therefor
• CPC Class Codes: F01L 2800/00 Methods of operation using a variable valve timing mechanism
• CPC Class Codes: F01L 9/20 by electric means
• CPC Class Codes: F02D 2041/001 for engines with variable valve actuation
• CPC Class Codes: F02D 2041/2037 for preventing bouncing of the valve needle
• CPC Class Codes: H01F 2007/1894 minimizing impact energy on closure of magnetic circuit
• CPC Class Codes: H01F 7/123 by ancillary coil
• CPC Class Codes: H01F 7/1844 Monitoring or fail-safe circuits for relays H01H47/002

Abstract

A method of controlling velocity of an armature of an electromagnetic actuator as the armature moves from a first position towards a second position is provided. The electromagnetic actuator includes a coil and a core at the second position. The coil generates a magnetic force to cause the armature to move towards and land at the second position. A control method is provided to ensure a near zero velocity landing of the armature in the second position while compensating for non-ideal external influences on the system.

Claims

1. A method of controlling velocity of an armature in an electromagnetic actuator as the armature moves from a first position towards a second position, the electromagnetic actuator including a coil and a core at the second position, the coil conducting a current and generating a magnetic force to cause the armature to move towards and land at the second position, and a spring structure acting on the armature to bias the armature from the second position, the method comprising the steps of:

generating magnetic flux in the coil such that the flux increases linearly at a first rate, the first rate being proportional to a crossover time from a previous cycle;

sensing the current passing through the coil;

detecting a near peak value of the current corresponding to the crossover time for the present cycle;

changing the rate of linear flux increase from the first rate to a second rate at the crossover time, the second rate being proportional to the derivative of the current during the previous cycle evaluated at a gamma time from the previous cycle, and the gamma time corresponding to the occurrence of a predetermined ratio between the current and the derivative of the current during a cycle; and

sensing the current and the derivative of the current and allowing the flux to increase rapidly without constraint upon the occurrence of the predetermined ratio between the current and the derivative of the current so as to capture and hold the armature in the second position.

2. The method of controlling velocity of an armature in an electromagnetic actuator according to claim 1, wherein the step of generating magnetic flux in the coil further includes the step of placing a current generator under servo control to generate the linearly increasing flux in the coil.

3. The method of controlling velocity of an armature in an electromagnetic actuator according to claim 1, wherein the first rate, the second rate and the gamma time are dynamically optimized to provide a near zero velocity landing of the armature in the second position.

4. The method of controlling velocity of an armature in an electromagnetic actuator according to claim 3, wherein the step of detecting a near peak value of the current corresponding to the crossover time for the present cycle further includes the step of sensing a predetermined decrease in current from a maximum value.

5. The method of controlling velocity of an armature in an electromagnetic actuator according to claim 4, wherein the dynamic optimization of the first rate, the second rate and the gamma time compensates for variations in supply voltage, mechanical vibration, temperature changes, changing friction, exhaust back pressure, armature center variation, or positive valve lash to maintain a near zero velocity armature landing speed.

6. The method of controlling velocity of an armature in an electromagnetic actuator according to claim 5, wherein the dynamic optimization of the first rate, the second rate and the gamma time ensures an armature landing velocity of less than 0.04 meters per second at 600 engine RPM and less than 0.4 meters per second at 6000 engine RPM.

7. The method of controlling velocity of an armature in an electromagnetic actuator according to claim 1, further including the steps of comparing the crossover time with a first nominal value and adjusting the first rate to decrease the difference between the crossover time and the first nominal value during the next armature cycle.

8. The method of controlling velocity of an armature in an electromagnetic actuator according to claim 7, further including the steps of comparing the derivative of the current at the gamma time with a second nominal value and adjusting the second rate to decrease the difference between the derivative of the current and the second nominal value during the next armature cycle.

9. The method of controlling velocity of an armature in an electromagnetic actuator according to claim 8, further including the step of dynamically optimizing the predetermined ratio between the current and the derivative of the current during every armature stroke such that an armature landing velocity of less than 0.04 meters per second at 600 engine RPM and less than 0.4 meters per second at 6000 engine RPM is achieved.

10. A method of determining if an armature in an electromagnetic actuator is moving properly as the armature moves from a first position towards a second position, the electromagnetic actuator including a coil and a core at the second position, the coil conducting a current and generating a magnetic force to cause the armature to move towards and land at the second position, and a spring structure acting on the armature to bias the armature from the second position, the method comprising the steps of:

generating magnetic flux in the coil such that the flux increases linearly at a first rate, wherein the first rate is proportional to a crossover time from a previous cycle;

sensing the current passing through the coil;

searching for a peak value in the current waveform;

concluding the armature is not moving if no peak value in the current waveform is detected.

11. An apparatus for controlling velocity of an armature in an electromagnetic actuator as the armature moves from a first position towards a second position, the electromagnetic actuator including a coil and a core at the second position, the coil conducting a current and generating a magnetic force to cause the armature to move towards and land at the second position, and a spring structure acting on the armature to bias the armature from the second position, the apparatus comprising:

a means for generating magnetic flux in the coil such that the flux increases linearly at a first rate, wherein the first rate is proportional to a crossover time from a previous cycle;

a means for sensing the current passing through the coil;

a means for detecting a near peak value of the current corresponding to the crossover time for the present cycle;

a means for changing the rate of linear flux increase from the first rate to a second rate at the crossover time, wherein the second rate is proportional to the derivative of the current during the previous cycle evaluated at a gamma time from the previous cycle, and wherein the gamma time corresponds to the occurrence of a predetermined ratio between the current and the derivative of the current during a cycle; and

a means for sensing the current and the derivative of the current and allowing the flux to increase rapidly without constraint upon the occurrence of the predetermined ratio between the current and the derivative of the current so as to capture and hold the armature in the second position.

12. The apparatus for controlling velocity of an armature in an electromagnetic actuator according to claim 11 wherein a current generating means under control of a servo means generates the current to produce a linearly increasing flux in the coil.