Electrically controlled hydraulic valve calibration method and system

• US 7,997,117 B2
• Filed: 05/12/2008
• Issued: 08/16/2011
• Est. Priority Date: 05/12/2008
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Yoo, Benjamin, Egelja, Aleksandar M., Beschorner, Matthew James, Zhang, Jiao, Shang, Tonglin
• Primary Examiner(s): Raevis; Robert R
• Application Number:
  US12/149,992
• Publication Number:
  US 20090277243A1
• Time in Patent Office: 1,191 Days
• Field of Search: None
• US Class Current: 73/1.79
• CPC Class Codes: F15B 19/002 Calibrating
• CPC Class Codes: F15B 2211/30535 the pressure compensating valve is arranged between pressure source and directional control valve
• CPC Class Codes: F15B 2211/30575 in a Wheatstone Bridge arrangement (also half bridges)
• CPC Class Codes: F15B 2211/31511 having a single pressure source
• CPC Class Codes: F15B 2211/327 electrically or electronically
• CPC Class Codes: F15B 2211/6309 the pressure being a pressure source supply pressure
• CPC Class Codes: F15B 2211/6313 the pressure being a load pressure
• CPC Class Codes: F15B 2211/665 Methods of control using electronic components
• CPC Class Codes: F15B 2211/6652 Control of the pressure source, e.g. control of the swash plate angle
• CPC Class Codes: F15B 2211/6654 Flow rate control
• CPC Class Codes: F16K 37/0083 by measuring valve parameters
• CPC Class Codes: G01F 15/005 Valves valves in general F16K

Abstract

A method of calibrating an electrically controlled hydraulic valve having a known relationship between flow rate through the valve and displacement of a valve element is disclosed. The method includes ascertaining a first current level for actuating the electrically controlled hydraulic valve to move the valve element to a position adjacent an inlet port, and a first displacement of the valve element responsive to the first current level. The method also includes ascertaining a second current level for actuating the electrically controlled hydraulic valve to move the valve element from the position adjacent the inlet port to a position permitting flow through the inlet port, and ascertaining a second displacement of the valve element responsive to the second current level. The method further includes establishing a relationship between current and displacement associated with the electrically controlled hydraulic valve.

Claims

1. A method of calibrating an electrically controlled hydraulic valve having a known relationship between flow rate through the valve and displacement of a valve element, comprising:

pumping hydraulic fluid from a fluid source through a first electrically controlled hydraulic valve, and through a second electrically controlled hydraulic valve to be calibrated;

actuating the second electrically controlled hydraulic valve to be calibrated to move the valve element to a position adjacent an inlet port so that the valve just opens enough to permit flow through the inlet port;

ascertaining a first current level for actuating the second electrically controlled hydraulic valve to move the valve element to the position adjacent the inlet port, and a first displacement of the valve element responsive to the first current level;

actuating the second electrically controlled hydraulic valve to move the valve element to a position permitting flow through the inlet port;

ascertaining a second current level for actuating the second electrically controlled hydraulic valve to move the valve element from the position adjacent the inlet port to the position permitting flow through the inlet port;

ascertaining a first flow rate through the first electrically controlled hydraulic valve to determine a second flow rate through the second electrically controlled hydraulic valve;

correlating the determined second flow rate through the second electrically controlled hydraulic valve with a second displacement of the valve element thereof based on the known relationship between flow rate through the valve and displacement of the valve element; and

establishing a relationship between current and displacement associated with the second electrically controlled hydraulic valve based on at least the first and the second current levels and the first and the second displacements.

2. The method of claim 1, further including pumping hydraulic fluid from the fluid source at a determined pump flow rate through the first and the second electrically controlled hydraulic valves.

3. The method of claim 1, wherein ascertaining the first flow rate through the first electrically controlled hydraulic valve includes:

setting a determined target flow rate through the first electrically controlled hydraulic valve;

ascertaining a target current associated with the first electrically controlled hydraulic valve and a target pressure of a pump when it is pumping fluid through the first electrically controlled hydraulic valve at the determined target flow rate; and

ascertaining the first flow rate through the first electrically controlled hydraulic valve based on at least the target flow rate.

4. The method of claim 2, further including determining the second flow rate through the second electrically controlled hydraulic valve by a controller based on at least the determined pump flow rate and the first flow rate through the first electrically controlled hydraulic valve.

5. The method of claim 3, further including:

ascertaining a first initial current associated with the first electrically controlled hydraulic valve;

ascertaining a second initial current associated with the second electrically controlled hydraulic valve based on at least a determined pump flow rate, the target flow rate through the first electrically controlled hydraulic valve, and a determined quantity relating displacement and current;

applying the first initial current to the first electrically controlled hydraulic valve; and

applying the second initial current to the second electrically controlled hydraulic valve.

6. The method of claim 5, further including:

adjusting the first initial current applied to the first electrically controlled hydraulic valve according to a determined adjustment process; and

adjusting the second initial current applied to the second electrically controlled hydraulic valve according to the determined adjustment process.

7. The method of claim 6, wherein the determined adjustment process includes adjusting the first initial current applied to the first electrically controlled hydraulic valve until the pressure of the hydraulic fluid pump is within a determined tolerance range of the target pump pressure.

8. The method of claim 7, wherein the determined adjustment process further includes adjusting the second initial current applied to the second electrically controlled hydraulic valve based on at least the adjusted first initial current applied to the first electrically controlled hydraulic valve according to a determined relation.

9. The method of claim 6, further including:

terminating the adjustment process when the adjusted first initial current applied to the first electrically controlled hydraulic valve is within a determined tolerance range of the target current associated with the first electrically controlled hydraulic valve, and pump pressure is within a determined tolerance range of the target pump pressure; and

ascertaining, based on at least the adjusted second initial current, the second current level for actuating the second electrically controlled hydraulic valve to move the valve element from the position adjacent the inlet port to the position permitting flow through the inlet port.

10. A system for calibrating an electrically controlled hydraulic valve having a known relationship between flow rate through the valve and displacement of a valve element, comprising:

a first and a second electrically controlled hydraulic valve disposed in parallel with each other, wherein the second electrically controlled hydraulic valve is to be calibrated;

a hydraulic fluid pump configured to pump hydraulic fluid from a fluid source through the first and second electrically controlled hydraulic valves; and

a controller configured to;

actuate the second electrically controlled hydraulic valve to be calibrated to move the valve element to a position adjacent the inlet port so that the valve just opens enough to permit flow through the inlet port;

actuate the second electrically controlled hydraulic valve to move the valve element to a position permitting flow through the inlet port;

ascertain a first current level for actuating the second electrically controlled hydraulic valve to move the valve element to the position adjacent the inlet port, and a first displacement of the valve element responsive to the first current level;

ascertain a second current level for actuating the second electrically controlled hydraulic valve to move the valve element from the position adjacent the inlet port to the position permitting flow through the inlet port;

ascertain a first flow rate through the first electrically controlled hydraulic valve to determine a second flow rate through the second electrically controlled hydraulic valve;

correlate the determined second flow rate through the second electrically controlled hydraulic valve with a second displacement of the valve element thereof based on the known relationship between flow rate through the valve and displacement of the valve element; and

establish a relationship between current and displacement associated with the second electrically controlled hydraulic valve based on at least the first and the second current levels, and the first and the second displacements.

11. The system of claim 10, wherein the hydraulic fluid pump is further configured to pump hydraulic fluid from the fluid source at a determined pump flow rate through the first and the second electrically controlled hydraulic valves.

12. The system of claim 10, wherein the controller is further configured to ascertain a target current associated with the first electrically controlled hydraulic valve and a target pump pressure when the fluid pump is pumping fluid to the first electrically controlled hydraulic valve at a target flow rate.

13. The system of claim 11, wherein the controller is further configured to determine the second flow rate through the second electrically controlled hydraulic valve based on at least the determined pump flow rate and the first flow rate through the first electrically controlled hydraulic valve.

14. The system of claim 12, wherein the controller is further configured to:

ascertain a first initial current associated with the first electrically controlled hydraulic valve;

ascertain a second initial current associated with the second electrically controlled hydraulic valve based on at least a determined pump flow rate, the first flow rate through the first electrically controlled hydraulic valve, and a determined quantity relating displacement and current;

apply the first initial current to the first electrically controlled hydraulic valve; and

apply the second initial current to the second electrically controlled hydraulic valve.

15. The system of claim 14, wherein the controller is further configured to:

adjust the first initial current applied to the first electrically controlled hydraulic valve according to a determined adjustment process; and

adjust the second initial current applied to the second electrically controlled hydraulic valve according to the determined adjustment process.

16. The system of claim 15, wherein the controller is further configured to adjust the first initial current applied to the first electrically controlled hydraulic valve until the pressure of the hydraulic fluid pump is within a determined tolerance range of the target pump pressure.

17. The system of claim 16, wherein the controller is further configured to adjust the second initial current applied to the second electrically controlled hydraulic valve based on at least the adjusted first initial current applied to the first electrically controlled hydraulic valve according to a determined relation.

18. The system of claim 17, wherein the controller is further configured to:

terminate the adjustment process when the adjusted first initial current applied to the first electrically controlled hydraulic valve is within a determined tolerance range of the target current associated with the first electrically controlled hydraulic valve, and pump pressure is within a determined tolerance range of the target pump pressure; and

ascertain the second current level for actuating the second electrically controlled hydraulic valve to move the valve element from the position adjacent the inlet port to the position permitting flow through the inlet port based on at least the adjusted second initial current.

19. A machine, comprising:

an engine;

a hydraulic system;

an implement system; and

a system for calibrating an electrically controlled hydraulic valve having a known relationship between flow rate through the valve and displacement of a valve element, the system including;

a first electrically controlled hydraulic valve having a known correlation between current and flow rate;

a second electrically controlled hydraulic valve to be calibrated and disposed in parallel with the first electrically controlled hydraulic valve;

a hydraulic fluid pump configured to pump hydraulic fluid from a fluid source through the first and second electrically controlled hydraulic valve; and

a controller configured to;

actuate the second electrically controlled hydraulic valve to move the valve element to a position adjacent the inlet port so that the valve just opens enough to permit flow through the inlet port;

actuate the second electrically controlled hydraulic valve to move the valve element to a position permitting flow through the inlet port;

ascertain a first current level for actuating the second electrically controlled hydraulic valve to move the valve element to the position adjacent the inlet port;

ascertain a first displacement of the valve element of the second electrically controlled hydraulic valve in response to the first current level;

ascertain a second current level for actuating the second electrically controlled hydraulic valve to move the valve element from the position adjacent the inlet port to the position permitting flow through the inlet port;

ascertain a first flow rate through the first electrically controlled hydraulic valve;

determine a second flow rate through the second electrically controlled hydraulic valve;

correlate the determined second flow rate through the second electrically controlled hydraulic valve with a second displacement of the valve element thereof based on the known relationship between flow rate through the valve and displacement of the valve element; and

establish a relationship between current and displacement associated with the second electrically controlled hydraulic valve based on at least one of the first and the second current levels, and the first and the second displacements.

20. The machine of claim 19, wherein the hydraulic fluid pump is further configured to pump hydraulic fluid from the fluid source to the first and the second electrically controlled hydraulic valves at a determined flow rate.