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

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).

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.

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).

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.