Method and system for controlling fluid flow in an electrohydraulic system having multiple hydraulic circuits

• US 6,282,891 B1
• Filed: 10/19/1999
• Issued: 09/04/2001
• Est. Priority Date: 10/19/1999
• Status: Expired due to Term

• Current Assignee: Caterpillar Sarl (Caterpillar Incorporated)
• Original Assignee: Caterpillar Incorporated
• Inventors: Rockwood, Brian D.
• Primary Examiner(s): Ryznic, John E.
• Application Number:
  US09/421,185
• Time in Patent Office: 686 Days
• Field of Search: 604/22, 604/26, 604/27
• US Class Current: 60/422
• CPC Class Codes: F15B 11/163 for sharing the pump output equally amongst users or groups of users, e.g. using anti-saturation, pressure compensation
• CPC Class Codes: F15B 21/087 Control strategy, e.g. with block diagram
• CPC Class Codes: F15B 2211/3057 having two valves, one for each port of a double-acting output member
• CPC Class Codes: F15B 2211/327 electrically or electronically
• CPC Class Codes: F15B 2211/6336 representing a state of the output member, e.g. position, speed or acceleration
• CPC Class Codes: F15B 2211/6654 Flow rate control
• CPC Class Codes: F15B 2211/7142 the output members being arranged in multiple groups
• CPC Class Codes: F15B 2211/78 Control of multiple output members

Abstract

A method and system for controlling fluid flow from a hydraulic fluid supply via a single hydraulic pump in an electrohydraulic system having multiple hydraulic cylinders connected to the hydraulic pump and corresponding work implements includes input devices for generating input signals representative of a desired amount of movement of at least two of the work implements. A controller, coupled to the input devices and the cylinders, determines a scaling factor for each of the hydraulic circuits associated with each of the cylinders for compensating the hydraulic circuit for receiving less than maximum fluid flow from the pump. The controller also determines a desired percentage of fluid flow to each of the hydraulic circuits based on the desired amount of movement of the work implements and the corresponding scaling factors and controls the fluid flow from the fluid supply to each of the hydraulic circuits based on the desired percentages of fluid flow to allow for maximum fluid flow to each of the hydraulic circuits.

Claims

1. A method for controlling fluid flow from a hydraulic fluid supply (28) via a single hydraulic pump (22) in an electrohydraulic system having multiple hydraulic cylinders (12) each connected to the hydraulic pump (22) and a corresponding work implement (14), wherein each of the cylinders (12) have at least two hydraulic circuits (16,18) for receiving the fluid supply (28) and moving the cylinders (12), the method comprising:

determining a scaling factor (50) for each of the hydraulic circuits (16,18) for compensating the hydraulic circuit (16,18) for receiving less than maximum fluid flow from the pump (22) wherein the determination of the scaling factor includes averaging of fluid flows at selected input conditions for each of the hydraulic circuits (16,18) to account for hysteresis associated with the hydraulic circuit (16,18);

receiving an input signal (62) representative of a desired amount of movement of at least two of the work implements (14);

determining a desired percentage of fluid flow (66) to each of the hydraulic circuits (16,18) associated with each of the cylinders (12) based on the desired amount of movement of the work implements (14) and the scaling factor of the corresponding hydraulic circuits (16,18); and

controlling the amount of fluid flow (68) from the hydraulic fluid supply (28) to each of the hydraulic circuits (16,18) based on the corresponding desired percentage of fluid flow so as to allow for maximum fluid flow to each of the hydraulic circuits (16,18).

2. The method as recited in claim 1 wherein determining each of the scaling factors comprises:

determining a plurality of fluid flows corresponding to a plurality of current values for each of the hydraulic circuits;

determining a maximum fluid flow for each hydraulic circuit from the plurality of fluid flows and a maximum overall fluid flow from all of the maximum fluid flows of all the hydraulic circuits; and

determining the scaling factor for each of the hydraulic circuits based on the maximum fluid flow for the corresponding hydraulic circuit and the maximum overall fluid flow.

3. The method as recited in claim 2 wherein each of the hydraulic circuits (16,18) has a known area, and wherein determining the plurality of fluid flows comprising:

applying the plurality of currents (52) to each of the hydraulic circuits (16,18), each of the currents having a different value;

sensing a position (54) of the cylinder (12) associated with each of the hydraulic circuits (16,18) in response to application of each of the currents; and

determining the plurality of fluid flows (56) associated with each of the currents based on the position of the associated cylinder (12) and the known area of the hydraulic circuit (16,18).

4. The method as recited in claim 2 wherein determining the scaling factor includes determining a percentage of fluid flow for each of the fluid flows based on the maximum fluid flow for each of the hydraulic circuits, and wherein controlling the amount of fluid flow to each of the hydraulic circuits includes applying a current to the hydraulic circuit based on the desired percentage of fluid flow and the current values associated with each of the determined percentages of fluid flows.

5. The method as recited in claim 1 wherein each of the hydraulic circuits have a known area and wherein determining the desired percentage of fluid flow comprises:

determining a desired relative velocity for each of the cylinders to be moved based on the desired amount of movement of the work implements; and

determining each of the desired percentages of fluid flow based on each of the relative velocities and the known area of each of the hydraulic circuits associated with the cylinders.

6. The method as recited in claim 5 wherein determining each of the desired relative velocities comprises:

determining a desired velocity for moving each of the cylinders associated with the work implements based on the desired amount of movement; and

determining the relative velocities based on each of the desired velocities and a total desired velocity for moving all of the cylinders.

7. The method as recited in claim 1 wherein controlling the amount of fluid flow further comprises:

sensing a position of each of the cylinders as they move; and

controlling the amount of fluid flow based on the position of each of the cylinders and the desired percentage of fluid flow to each of the hydraulic circuits associated with the cylinders.

8. The method as recited in claim 7 wherein controlling the amount of fluid flow further comprises:

determining an actual flow of fluid to each of the hydraulic circuits based on the position of the cylinders;

determining an actual percentage of fluid flow to each of the hydraulic circuits based on the actual flow and the total fluid flow to all of the hydraulic circuits; and

comparing the actual percentage of fluid flow of each of the hydraulic circuits with the corresponding desired percentage of fluid flow.

9. A method for controlling fluid flow from a hydraulic fluid supply (28) via a single hydraulic pump (22) in an electrohydraulic system having multiple hydraulic cylinders (12) each connected to the hydraulic pump (22) and a corresponding work implement (14), wherein each of the cylinders (12) have at least two hydraulic circuits (16,18) of a known area for receiving the fluid supply (28) and moving the cylinders (12), the method comprising:

applying the plurality of currents (52) to each of the hydraulic circuits (16,18), each of the currents having a different value;

sensing a position (54) of the cylinder (12) associated with each of the hydraulic circuits (16,18) in response to application of each of the currents;

determining the plurality of fluid flows (56) associated with each of the currents based on the position of the associated cylinder (12), on the known area of the hydraulic circuit (16,18), and on an average of fluid flow over selected current values for each of the hydraulic circuits (16,18) to account for hysteresis associated the hydraulic circuit (16,18);

determining a maximum fluid flow for each hydraulic circuit (16,18) from the plurality of fluid flows and a maximum overall fluid flow from all of the maximum fluid flows of all the hydraulic circuits (16,18);

determining the scaling factor (60) for each of the hydraulic circuits (16,18) based on the maximum fluid flow for the corresponding hydraulic circuit (16,18) and the maximum overall fluid flow for compensating the hydraulic circuit (16,18) for receiving less than maximum fluid flow from the pump (22);

receiving an input signal (62) representative of a desired amount of movement of at least two of the work implements (14);

determining a desired percentage of fluid flow (66) to each of the hydraulic circuits (16,18) associated with each of the cylinders (12) based on the desired amount of movement of the work implements (14) and the scaling factor of the corresponding hydraulic circuits (16,18); and

controlling the amount of fluid flow (68) from the hydraulic fluid supply (28) to each of the hydraulic circuits (16,18) based on the corresponding desired percentage of fluid flow so as to allow for maximum fluid flow to each of the hydraulic circuits (16,18).

10. A method for controlling fluid flow from a hydraulic fluid supply (28) via a single hydraulic pump (22) in an electrohydraulic system having multiple hydraulic cylinders (12) each connected to the hydraulic pump (22) and a corresponding work implement (14), wherein each of the cylinders (12) have at least two hydraulic circuits (16,18) for receiving the fluid supply (28) and moving the cylinders (12), the method comprising:

determining a plurality of fluid flows (52,54,56) corresponding to a plurality of current values for each of the hydraulic circuits (16,18);

determining a maximum fluid flow for each hydraulic circuit (16,18) from the plurality of fluid flows and a maximum overall fluid flow from all of the maximum fluid flows of all the hydraulic circuits (16,18);

determining the scaling factor (60) for each of the hydraulic circuits (16,18) based on the maximum fluid flow for the corresponding hydraulic circuit (16,18), on the maximum overall fluid flow, and on a percentage of fluid flow for each of the fluid flows based on the maximum fluid flow for each of the hydraulic circuits (16,18) for compensating the hydraulic circuit (16,18) for receiving less than maximum fluid flow from the pump (22);

receiving an input signal (62) representative of a desired amount of movement of at least two of the work implements (14);

determining a desired percentage of fluid flow (66) to each of the hydraulic circuits (16,18) associated with each of the cylinders (12) based on the desired amount of movement of the work implements (14) and the scaling factor of the corresponding hydraulic circuits (16,18); and

controlling the amount of fluid flow (68) from the hydraulic fluid supply (28) to each of the hydraulic circuits (16,18) based on the corresponding desired percentage of fluid flow so as to allow for maximum fluid flow to each of the hydraulic circuits (16,18) and by applying a current to the hydraulic circuit (16,18) based on the desired percentage of fluid flow and the current values associated with each of the determined percentages of fluid flows and performing an interpolation on the current values if the desired percentage of fluid flow falls between any two determined percentages of fluid flow.

11. A system (10) for controlling fluid flow from a hydraulic fluid (28) supply via a single hydraulic pump (22) in an electrohydraulic system having multiple hydraulic cylinders (12) each connected to the hydraulic pump (22) and a corresponding work implement (14), wherein each of the cylinders (12) have at least two hydraulic circuits (16,18), each of a known area, for receiving the fluid supply (28) and moving the cylinders (12), the system (10) comprising:

at least two input devices (34) for generating at least two corresponding input signals representative of a desired amount of movement of at least two of the work implements (14);

a controller (36), coupled to the input devices (34) and the hydraulic circuits (16,18), for determining a scaling factor for each of the hydraulic circuits (16,18) for compensating the hydraulic circuit for receiving less than maximum fluid flow from the pump (22), determining a desired percentage of fluid flow to each of the hydraulic circuits (16,18) associated with each of the cylinders (12) based on the desired amount of movement of the work implements (14) and the scaling factor of the corresponding hydraulic circuits (16,18), and controlling the amount of fluid flow from the hydraulic fluid supply to each of the hydraulic circuits (16,18) based on the corresponding desired percentage of fluid flow so as to allow for maximum fluid flow to each of the hydraulic circuits (16,18); and

further wherein;

the controller (36), in determining each of the scaling factors, is further operative to determine a plurality of fluid flows corresponding to a plurality of current values and an average of fluid flow over selected current values for each of the hydraulic circuits (16,18) to account for hysteresis associated the hydraulic circuit and to apply the plurality of currents to each of the hydraulic circuits (16,18) wherein each of the currents have a different value, to determine a maximum fluid flow for each hydraulic circuit (16,18) from the plurality of fluid flows and a maximum overall fluid flow from all of the maximum fluid flows of all the hydraulic circuits (16,18), and to determine the scaling factor for each of the hydraulic circuits (16,18) based on the maximum fluid flow for the corresponding hydraulic circuit (16,18)and the maximum overall fluid flow; and

the system (10) further comprising a position sensor (40) coupled to each of the cylinders (12) and the controller (36), for sensing a position of the cylinder (12) associated with each of the hydraulic circuits (16,18) in response to application of each of the currents and generating corresponding position signals, and wherein the controller (36) is further operative to determine the plurality of fluid flows associated with each of the currents based on the position of the associated cylinder (12) and the known area of the hydraulic circuit (16,18).

12. A system (10) for controlling fluid flow from a hydraulic fluid (28) supply via a single hydraulic pump (22) in an electrohydraulic system having multiple hydraulic cylinders (12) each connected to the hydraulic pump (22) and a corresponding work implement (14), wherein each of the cylinders (12) have at least two hydraulic circuits (16,18) for receiving the fluid supply (28) and moving the cylinders (12), the system (10) comprising:

at least two input devices (34) for generating at least two corresponding input signals representative of a desired amount of movement of at least two of the work implements (14);

a controller (36), coupled to the input devices (34) and the hydraulic circuits (16,18), for determining a scaling factor for each of the hydraulic circuits (16,18) for compensating the hydraulic circuit for receiving less than maximum fluid flow from the pump (22), determining a desired percentage of fluid flow to each of the hydraulic circuits (16,18) associated with each of the cylinders (12) based on the desired amount of movement of the work implements (14) and the scaling factor of the corresponding hydraulic circuits (16,18), and controlling the amount of fluid flow from the hydraulic fluid supply to each of the hydraulic circuits (16,18) based on the corresponding desired percentage of fluid flow so as to allow for maximum fluid flow to each of the hydraulic circuits (16,18); and

further wherein;

the controller (36), in determining each of the scaling factors, is further operative to determine a plurality of fluid flows corresponding to a plurality of current values for each of the hydraulic circuits (16,18), determine a maximum fluid flow for each hydraulic circuit (16,18) from the plurality of fluid flows and a maximum overall fluid flow from all of the maximum fluid flows of all the hydraulic circuits (16,18), determine the scaling factor for each of the hydraulic circuits (16,18) based on the maximum fluid flow for the corresponding hydraulic circuit (16,18)and the maximum overall fluid flow, and determine a percentage of fluid flow for each of the fluid flows based on the maximum fluid flow for each of the hydraulic circuits (16,18) and wherein the controller (36), in controlling the amount of fluid flow to each of the hydraulic circuits (16,18), is further operative to apply a current to the hydraulic circuit (16,18) based on the desired percentage of fluid flow and the current values associated with each of the determined percentages of fluid flows, and in applying the current, is further operative to perform an interpolation on the current values if the desired percentage of fluid flow falls between any two determined percentages of fluid flow.

13. A system for controlling fluid flow from a hydraulic fluid supply via a single hydraulic pump in an electrohydraulic system having multiple hydraulic cylinders each connected to the hydraulic pump and a corresponding work implement, wherein each of the cylinders have at least two hydraulic circuits for receiving the fluid supply and moving the cylinders, the system comprising:

at least two input devices for generating at least two corresponding input signals representative of a desired amount of movement of at least two of the work implements;

a controller, coupled to the input devices and the hydraulic circuits, for determining a scaling factor for each of the hydraulic circuits for compensating the hydraulic circuit for receiving less than maximum fluid flow from the pump, determining a desired percentage of fluid flow to each of the hydraulic circuits associated with each of the cylinders based on the desired amount of movement of the work implements and the scaling factor of the corresponding hydraulic circuits, and controlling the amount of fluid flow from the hydraulic fluid supply to each of the hydraulic circuits based on the corresponding desired percentage of fluid flow so as to allow for maximum fluid flow to each of the hydraulic circuits.

14. The system as recited in claim 13 wherein the controller, in determining each of the scaling factors, is further operative to determine a plurality of fluid flows corresponding to a plurality of current values for each of the hydraulic circuits, determine a maximum fluid flow for each hydraulic circuit from the plurality of fluid flows and a maximum overall fluid flow from all of the maximum fluid flows of all the hydraulic circuits, and determine the scaling factor for each of the hydraulic circuits based on the maximum fluid flow for the corresponding hydraulic circuit and the maximum overall fluid flow.

15. The system as recited in claim 14 wherein each of the hydraulic circuits has a known area, and wherein the controller, in determining the plurality of fluid flows, is further operative to apply the plurality of currents to each of the hydraulic circuits, wherein each of the currents having a different value, and wherein the system further comprising a position sensor, coupled to each of the cylinders and the controller, for sensing a position of the cylinder associated with each of the hydraulic circuits in response to application of each of the currents and generating corresponding position signals, and wherein the controller is further operative to determine the plurality of fluid flows associated with each of the currents based on the position of the associated cylinder and the known area of the hydraulic circuit.

16. The system as recited in claim 15 wherein the each of the cylinder further comprise a valve coupled to the corresponding hydraulic circuits and a solenoid coupled to the valve and the controller for causing the valve to move and allow fluid flow therein and wherein the controller, in applying the plurality of currents, is operative to apply the plurality of currents to each of the solenoids.

17. The system as recited in claim 15 wherein the controller, in controlling the amount of fluid flow, is further operative to receive the position signals of each of the cylinders as they move, and control the amount of fluid flow based on the position of each of the cylinders and the desired percentage of fluid flow to each of the hydraulic circuits associated with the cylinders.

18. The system as recited in claim 17 wherein the controller, in controlling the amount of fluid flow, is further operative to determine an actual flow of fluid to each of the hydraulic circuits based on the position of the cylinders, determine an actual percentage of fluid flow to each of the hydraulic circuits based on the actual flow and the total fluid flow to all of the hydraulic circuits, and compare the actual percentage of fluid flow of each of the hydraulic circuits with the corresponding desired percentage of fluid flow.

19. The system as recited in claim 14 wherein the controller, in determining the scaling factor, is further operative to determine a percentage of fluid flow for each of the fluid flows based on the maximum fluid flow for each of the hydraulic circuits and wherein the controller, in controlling the amount of fluid flow to each of the hydraulic circuits, is further operative to apply a current to the hydraulic circuit based on the desired percentage of fluid flow and the current values associated with each of the determined percentages of fluid flows.

20. The system as recited in claim 13 wherein each of the hydraulic circuits has a known area and wherein the controller, in determining the desired percentage of fluid flow, is further operative to determine a desired relative velocity for each of the cylinders to be moved based on the desired amount of movement of the work implements, and determine each of the desired percentages of fluid flow based on each of the relative velocities and the known area of each of the hydraulic circuits associated with the cylinders.

21. The system as recited in claim 20 wherein the controller, in determining each of the desired relative velocities, is further operative to determine a desired velocity for moving each of the cylinders associated with the work implements based on the desired amount of movement, and determine the relative velocities based on each of the desired velocities and a total desired velocity for moving all of the cylinders.