# US 6,725,131 B2 · System and method for controlling hydraulic flow > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,725,131 B2 - Document ID: US6725131B2 - Status: Granted - Kind: B2 - Application number: 10/029,243 - Filed: 2001-12-28 - Published: 2003-07-03 - Granted: 2004-04-20 - Earliest claimed: 2001-12-28 - Assignees: Caterpillar Inc.; Shin Caterpillar Mitsubishi Ltd. - Inventors: Stephen V. Lunzman - Web page: https://patentgrep.com/patent/US6725131B2 ## CPC - G05D 7/0635: {by action on throttling means (G05D7/0688, G05D7/0694 take precedence)} - Y10T 137/0318: Processes - Y10T 137/0379: By fluid pressure - G05D: SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract A method is provided for controlling hydraulic flow through a valve in fluid communication with a pump and a hydraulic actuator. The method includes monitoring load pressure of the valve, and selecting a flow limit and a pressure limit of the valve. A flow-pressure relationship in the valve is determined based on the flow limit, the pressure limit, and a desired flow-pressure characteristic. A hydraulic flow rate command is computed based on the determined flow pressure relationship and the monitored load pressure of the valve. ## Claims ### Claim 1 A method for controlling hydraulic flow through a valve in fluid communication with a pump and a hydraulic actuator, comprising: monitoring load pressure of the valve; selecting a flow limit and a pressure limit of the valve; determining a flow-pressure relationship in the valve based on the flow limit, the pressure limit, and a desired flow-pressure characteristic, wherein the flow-pressure relationship is represented by a flow-pressure control diagram, and the flow-pressure characteristic is represented by at least one of a slope and a shape of the diagram; and computing a hydraulic flow rate command based on the determined flow-pressure relationship and the monitored load pressure of the valve. ### Claim 2 (depends on 1) The method of claim 1, further including transforming a cylinder velocity limit and a cylinder force limit set by an operator input into the flow limit and the pressure limit of the valve. ### Claim 3 (depends on 2) The method of claim 2, further including modulating the operator input into the cylinder velocity limit and the cylinder force limit. ### Claim 4 (depends on 1) The method of claim 1, wherein the load pressure of the valve is monitored at an outlet port of the valve. ### Claim 5 (depends on 1) The method of claim 1, further including determining a pressure drop across the valve, and computing a command signal to actuate the valve based on the pressure drop and the hydraulic flow rate command. ### Claim 6 (depends on 5) The method of claim 5, the pressure drop across the valve is determined by monitoring an inlet port pressure and an outlet port pressure of the valve. ### Claim 7 A method for providing a plurality of flow-pressure relationships in a valve in fluid communication with a pump and a hydraulic actuator, comprising: selecting a flow limit and a pressure limit of the valve; determining a first flow-pressure relationship of the plurality of flow-pressure relationships in the valve based on the flow limit, the pressure limit, and a first desired flow-pressure characteristic; and determining a second flow-pressure relationship of the plurality of flow-pressure relationships in the valve based on the flow limit, the pressure limit, and a second desired flow-pressure characteristic different from the first desired flow-pressure characteristic, wherein the flow-pressure relationship is represented by a flow-pressure control diagram, and the flow-pressure characteristic is represented by at least one of a slope and a shape of the diagram. ### Claim 8 A system for controlling hydraulic flow in a valve in fluid communication with a pump and a hydraulic actuator, the valve having an inlet port and an outlet port, the system comprising: a pressure sensor assembly for monitoring load pressure; and a flow controller electrically coupled to the pressure sensor assembly, the controller including a flow-pressure control unit configured to determine a flow-pressure relationship in the valve based on a flow limit and a pressure limit of the valve and a desired flow-pressure characteristic, wherein the flow-pressure relationship is represented by a flow-pressure control diagram, and the flow-pressure characteristic is represented by at least one of a slope and a shape of the diagram. ### Claim 9 (depends on 8) The system of claim 8, wherein the flow-pressure control unit is configured to compute a hydraulic flow rate command based on the determined flow-pressure relationship and the monitored load pressure of the valve. ### Claim 10 (depends on 9) The system of claim 9, wherein the controller includes a cylinder transform unit coupled to the flow-pressure control unit, the cylinder transform unit being configured to transform a cylinder velocity limit and a cylinder force limit into the flow limit and the pressure limit of the valve. ### Claim 11 (depends on 10) The system of claim 10, wherein the controller includes a modulation control unit coupled to the cylinder transform unit, the modulation control unit being configured to modulate an operator input into the cylinder velocity limit and the cylinder force limit. ### Claim 12 (depends on 9) The system of claim 9, wherein the controller includes an electronic flow control unit coupled to the flow-pressure control unit and the pressure sensor assembly, the pressure sensor assembly being configured to monitor a pressure drop across the valve, the electronic flow control unit being configured to compute a command signal to actuate the valve based on the pressure drop and the hydraulic flow rate command. ### Claim 13 (depends on 8) The system of claim 8, wherein the controller is preprogrammed with the desired flow-pressure characteristic. ### Claim 14 (depends on 13) The system of claim 13, wherein the controller is preprogrammed with a second desired flow-pressure characteristic. ### Claim 15 (depends on 8) The system of claim 8, wherein the flow-pressure relationship is represented by a flow-pressure control diagram, and the flow-pressure characteristic is represented by a shape of the diagram. ### Claim 16 A system for controlling hydraulic flow, comprising: an independent metering valve having an inlet port and an outlet port; a pressure sensor assembly for monitoring load pressure of the independent metering valve; and a flow controller electrically coupled to the pressure sensor assembly, the controller including: a flow-pressure control unit configured to determine a flow-pressure relationship in the independent metering valve based on a flow limit and a pressure limit of the valve and a desired flow-pressure characteristic; and a flow-pressure control unit configured to compute a hydraulic flow rate command based on the determined flow-pressure relationship and the monitored load pressure of the independent metering valve, the controller being preprogrammed with the desired flow-pressure characteristic, wherein the flow-pressure relationship is represented by a flow-pressure control diagram, and the flow-pressure characteristic is represented by at least one of a slope and a shape of the diagram. ### Claim 17 (depends on 16) The system of claim 16, wherein the flow-pressure control unit is configured to determine a second flow-pressure relationship in the independent metering valve based on the flow limit and the pressure limit of the independent metering valve and a second desired flow-pressure characteristic. ### Claim 18 A method for controlling movement of a hydraulic actuator, comprising: storing predetermined valve operational characteristics; generating input signals based on movement of an input device; simulating a flow-pressure relationship based on the input signals and the predetermined valve operational characteristics, wherein the flow-pressure relationship is represented by a flow-pressure control diagram, and the flow-pressure characteristic is represented by at least one of a slope and a shape of the diagram; generating a valve command based on the flow-pressure simulation; and causing movement of the actuator through communication of the valve command with a control valve in fluid communication with the actuator. ### Claim 19 (depends on 18) The method for claim 18, wherein the flow-pressure simulation provides is a flow-pressure relationship of an open center system.