# US 10,119,705 B2 · Water/fuel ratio control using complementary filtering between valve and flowmeter feedback signals > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,119,705 B2 - Document ID: US10119705B2 - Status: Granted - Kind: B2 - Application number: 15/130,739 - Filed: 2016-04-15 - Published: 2017-10-19 - Granted: 2018-11-06 - Earliest claimed: 2016-04-15 - Assignees: United Technologies Corporation - Applicants: United Technologies Corporation - Inventors: Andrew B. Thompson - Web page: https://patentgrep.com/patent/US10119705B2 ## CPC - F23R 3/36: Supply of different fuels - F02M 25/0227: {Control aspects; Arrangement of sensors; Diagnostics; Actuators} - F23D 99/002: {Burners specially adapted for specific applications} - F23N 1/002: {using electronic means (F23N1/04 - F23N1/10 take precedence)} - F23R 3/28: characterised by the fuel supply (burners F23D) - G05B 15/02: electric - G05D 11/132: {by controlling the flow of the individual components (G05D11/133 takes precedence)} - Y02T 10/12: Improving ICE efficiencies - F23R: GENERATING COMBUSTION PRODUCTS OF HIGH PRESSURE OR HIGH VELOCITY, e.g. GAS-TURBINE COMBUSTION CHAMBERS (fluidised bed combustion apparatus specially adapted for operation at superatmospheric pressures F23C10/16) - F02M: SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF - F23D: BURNERS - F23N: REGULATING OR CONTROLLING COMBUSTION (control devices specially adapted for combustion apparatus in which combustion takes place in a fluidised bed of fuel or other particles F23C10/28; condition responsive controls for regulating combustion in domestic stoves with open fires for solid fuel F24B1/187) - G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G) - G05D: SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract Systems and methods for use with water-fuel supply to industrial engines are provided. A method for controlling water supplied to an engine may include using both a desired water-fuel ratio, and a compensated fuel flow. This compensated fuel flow may be calculated by a controller-implemented complementary filter, which may include receiving, by the controller, a first signal and a second signal. The complementary filter may subtract the second signal from the first signal to create an error signal, lag the error signal to create a lagged error signal, and add the lagged error signal to the second signal to create a compensated signal. The controller may calculate a water flow request using a desired water-fuel ratio and the compensated signal. ## Claims ### Claim 1 A method for determining fuel supplied to an engine comprising: receiving, by a controller, a first signal; receiving, by the controller, a second signal, wherein a response bandwidth frequency of the first signal is less than the response bandwidth frequency of the second signal; subtracting, by the controller, the second signal from the first signal to create an error signal; lagging, by the controller, the error signal to create a lagged error signal using a first-order filter utilizing a time constant; adding, by the controller, the lagged error signal to the second signal to create a compensated signal; receiving, by the controller, a switch control signal, the compensated signal, and the second signal; determining, by the controller, the controller implementing a switch logic, whether to send at least one of the compensated signal or the second signal; sending, by the controller, at least one of the compensated signal or the second signal to a water-fuel ratio system. ### Claim 2 (depends on 1) The method of claim 1, wherein the first signal is received by the controller from a fuel flowmeter. ### Claim 3 (depends on 2) The method of claim 2, wherein the second signal is received by the controller from a fuel valve. ### Claim 4 (depends on 3) The method of claim 3, wherein the controller determines to send the second signal in response to at least one of the time constant comprising a value of less than or equal to zero or a reset signal being true. ### Claim 5 A water-fuel control system for an engine comprising: a controller, the controller implementing a complementary filter, configured to: receive a first signal and a second signal, wherein a response bandwidth frequency of the first signal is less than the response bandwidth frequency of the second signal; calculate an error signal using the first signal and the second signal; lag the error signal to create a lagged error signal; add the lagged error signal and the second signal to create a compensated signal; receive a switch control signal, the compensated signal, and the second signal; determine the controller implementing a switch logic, whether to send at least one of the compensated signal or the second signal; calculate a water flow request, wherein the calculating is performed using a desired water-fuel ratio and the at least one of the compensated signal or the second signal; and send the water flow request to a water control system, wherein the water flow request is used to at least one of open or close a water valve. ### Claim 6 (depends on 5) The water-fuel control system of claim 5, wherein the lagging the error signal is performed using a first-order filter utilizing a time constant. ### Claim 7 (depends on 6) The water-fuel control system of claim 6, wherein the first signal comprises a low frequency signal relative to the second signal and the second signal comprises a high frequency signal relative to the first signal. ### Claim 8 (depends on 7) The water-fuel control system of claim 7, wherein the error signal is calculated by subtracting the second signal from the first signal. ### Claim 9 (depends on 8) The water-fuel control system of claim 8, wherein the first signal is based upon a fuel flow rate determined by a flowmeter and the second signal is based upon a fuel valve position. ### Claim 10 (depends on 9) The water-fuel control system of claim 9, wherein the switch control signal is true in response to at least one of a reset signal being true or the time constant comprising a non-positive value. ### Claim 11 (depends on 10) The water-fuel control system of claim 10, wherein the switch control signal is false in response to both the reset signal being false and the time constant comprising a positive value. ### Claim 12 (depends on 11) The water-fuel control system of claim 11, wherein the controller sends the compensated signal in response to the switch control signal being false and wherein the controller sends the second signal in response to the switch control signal being true.