WORK MACHINE AND METHOD FOR CALIBRATING AN ELECTROHYDRAULIC PUMP IN AN OPEN-CENTER HYDRAULIC SYSTEM

Abstract

A working machine and a method for a working machine with an open-center hydraulic system for controlling the actuation of an attachment comprise an attachment control valve, an electro-hydraulically controlled pump, a hydraulic circuit coupled to the attachment actuator, and a pressure transducer positioned between the pump and the attachment control valve for measuring pressure in the hydraulic circuit.A calibration system for calibrating the pump comprises a controller having a non-volatile, computer-readable medium containing program instructions that cause a processor to calibrate a first pump threshold for the pump in a pump flow curve, wherein the first pump threshold includes a minimum pump control signal to actuate the pump; determine a hysteresis band in the pump flow curve; and calibrate a second pump threshold for the pump in the pump flow curve, wherein the second pump threshold includes a maximum pump control signal to actuate the pump below a relief setpoint.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This patent application is a continuation-in-part of U.S. patent application Serial No. 17 / 651,920, "Work Machine and Method for Calibrating an Electrohydraulic Pump in an Open Center Hydraulic System," filed on February 22, 2022, in the United States Patent and Trademark Office, the contents of which are incorporated herein by reference. AREA OF REVELATION

[0002] The present disclosure relates to a work machine and a method for calibrating an electro-hydraulic pump in an open-center hydraulic system. BACKGROUND

[0003] Industrial or construction machinery often uses a system of hydraulic pumps, valves, and actuators to effect movement of an attachment. Various technologies exist for managing the control of these hydraulic devices. Systems can be developed that combine elements of any available technology. Some systems rely solely on hydromechanical means to control pumps, valves, and actuators (commonly referred to as manually or pilot-operated controls). However, other systems incorporate electronic control devices (commonly known as electro-hydraulic controls). Electro-hydraulic devices can be used to control hydraulic pumps and valves. These devices can take various designs.One embodiment of an electrohydraulic control device is the use of an electromagnet to induce electromagnetic forces, either directly or indirectly, on a valve spool by applying a given current to the electromagnet. The actuation of the valve spool by the electromagnet is used to induce a given hydraulic pressure, which can then be used to pilot a valve spool or main-stage pump. This provides the ability to electronically control the flow or pressure within a hydraulic circuit, making it ideal for implementation in complex control systems employing microcontrollers. Depending on the application of electrohydraulic devices to a given system, a process for calibrating components is often required to optimize system performance.A nominal input / output relationship for a device can be determined based on the component design. However, manufacturing tolerances can cause the system to deviate from theoretical nominal performance from one component to the next. Calibration routines are often developed to account for such variations. One possibility is to develop a calibration routine optimized to account for the variations in pump performance in an open-center hydraulic system. SUMMARY

[0004] This Summary is provided to introduce a selection of concepts that are described in more detail below in the Detailed Description and the accompanying drawings. This Summary is not intended to identify key factors or essential features of the appended claims, nor should it be relied upon to determine the scope of the appended claims.

[0005] The present disclosure relates to a work machine having a calibration system and a method for calibrating the pump in an open-center hydraulic system. The open-center hydraulic system controls the actuation of the attachment. The open-center hydraulic system includes an attachment control valve configured to control a flow ratio of fluid through the hydraulic circuit between a tank and an attachment actuator in response to a valve control signal. The hydraulic system further includes an electro-hydraulically controlled pump for controlling an outlet flow of fluid through the hydraulic circuit in response to a pump control signal. This hydraulic circuit is coupled to the attachment actuator. A pressure transducer is arranged for measuring a flow pressure in the hydraulic circuit between the pump and the attachment control valve. The calibration system calibrates the pump to control fluid flow through the open-center hydraulic system.The calibration system includes a controller having a non-transitory computer-readable medium with program instructions for performing the following steps. The program instructions calibrate a first pump threshold and a second pump threshold in the pump flow curve. From the first pump threshold, a minimum pump control signal is extrapolated to actuate the pump. From the second pump threshold, a maximum pump control signal is extrapolated to actuate the pump below a relief setpoint. The program instructions further include controlling actuation of the attachment by transmitting the calibrated pump control signals to the electro-hydraulically controlled pump.

[0006] Calibrating the first pump threshold in the pump flow curve may include setting the pump to a constant flow rate, recording the flow pressure, and increasing the valve control signal by a pump calibration step point until the flow pressure changes by a defined value. The defined flow pressure change value indicates the fluid flow restricted to the tank. Calibrating the first pump threshold further includes maintaining the valve control signal at the restriction setting, neutralizing the pump control signal, and increasing the pump control signal by a pump calibration step point. The program instruction correlates a flow pressure change with the change in the pump control signal to identify a point on the pump flow curve and iteratively repeats increasing the pump control signal until the flow pressure increases by a target value.

[0007] The program instructions may further include determining a hysteresis band in the pump flow curve. The program instructions include setting the valve control signal to the restriction setting from calibrating the first pump threshold, setting the pump control signal to the full pump command, recording the flow pressure, and reducing the valve control signal until the flow pressure drops by a defined value. The program instructions for determining a hysteresis band further include correlating the flow pressure with the pump control signal to identify a point on the pump flow curve and iteratively repeating reducing the pump control signal and correlating the flow pressure with the pump control signal until the pressure drops by a second target value.

[0008] Calibrating the second pump threshold for the pump in the pump flow curve may include: adjusting the adjusted valve control signal indicating that fluid flow to the tank is restricted; adjusting the pump control signal to the full pump command; recording the flow pressure at the full pump command; adjusting the pump control signal toward the minimum pump control signal; incrementing the pump control signal by one calibration step point; and determining whether the flow pressure is within a defined range of the recorded flow pressure at the full pump command. Incrementing the pump control signal by one calibration step point is repeated iteratively until the flow pressure is within a defined range of the recorded flow pressure at the full pump command.

[0009] The program instructions include checking whether the fluid is within an operating temperature range before continuing with calibration.

[0010] The program instructions include checking whether the engine speed is within an operating speed range before continuing the calibration.

[0011] In another embodiment, the program instructions for calibrating the second pumping threshold in the pumping flow curve include: setting the valve control signal to a restriction setting, the restriction setting indicating restricted fluid flow to the tank, setting the pump control signal to the full pumping command, recording the flow pressure at the full pumping command, adjusting the pump control signal toward the minimum pump control signal, and incrementing the pump control signal by one calibration step point. The program instructions further include determining whether the flow pressure is within a defined range of the recorded flow pressure at the full pumping command and iteratively repeating the incrementing of the pump control signal by one calibration step point until the flow pressure is within a defined range of the recorded flow pressure.Further features and aspects of the disclosure will become apparent upon consideration of the detailed description and the accompanying drawings.

[0012] The method for calibrating an electro-hydraulically controlled pump on a work machine with an open-center hydraulic system for actuating an attachment coupled to the work machine comprises the following steps. In a first step, the method comprises calibrating a first pump threshold in a pump flow curve for the pump, wherein a minimum pump control signal for actuating the pump is extrapolated from the first pump threshold. In a next step, the method comprises calibrating a second pump threshold in the pump flow curve for the pump, wherein a maximum pump control signal for actuating the pump below an unloading setpoint is extrapolated from the second pump threshold. The method then comprises controlling actuation of the attachment actuator by transmitting the calibrated pump control signal to the electro-hydraulically controlled pump.

[0013] Further features and aspects of the disclosure will become apparent upon consideration of the detailed description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 illustrates one embodiment of an open-center hydraulic valve system diagram; Fig. 2 illustrates an embodiment of a pump flow curve; Fig. 3 shows an overview diagram for calibrating the pump; Fig. Figure 4A illustrates a scheme for calibrating the first pump threshold; Fig. Figure 4B is a more detailed schematic of a portion of the flowchart for calibrating the first pump threshold; Fig. Figure 5A shows a scheme for calibrating the hysteresis; Fig. Figure 5B is a more detailed schematic of a portion of the hysteresis calibration flow chart; Fig. 6A illustrates a scheme for calibrating the second pump threshold; Fig. 6B is a more detailed schematic of a portion of the flowchart for calibrating the second pump threshold; and Fig. Figure 6B is a method for calibrating an electro-hydraulic pump in an open-center hydraulic system.

[0014] Before embodiments are explained in detail, it is to be understood that the disclosure is not limited in its application to the details of construction and arrangement of components set forth in the following description or illustrated in the following drawings. The disclosure is capable of other embodiments and may be practiced or carried out in various ways. Furthermore, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be considered limiting. DETAILED DESCRIPTION

[0015] As used herein, unless otherwise limited or modified, lists of items separated by conjunctive terms (e.g., "and") and also preceded by the phrase "one or more of" or "at least one of" refer to configurations or arrangements that may include individual items of the list or any combination thereof. For example, "one or more of A, B, and C" or "at least one of A, B, and C" respectively indicate the possibilities of only A, only B, only C, or any combination of two or more of A, B, and C (e.g., A and B; B and C; A and C; or A, B, and C).

[0016] As used herein, the term "controller" represents a computing device that includes a processor and memory. The "controller" may be a single device or, alternatively, multiple devices. Further, the controller may refer to any hardware, software, firmware, electronic control component, processing logic, or processing device, individually or in any combination, including, but not limited to, an application-specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or in a group), and memory executing one or more software or firmware programs, linking logic circuitry, and / or other suitable components that provide the described functionality.

[0017] The term "processor" is described and shown as a single processor. However, two or more processors may be used according to particular needs, desires, or particular implementations of the controller and the described functionality. The processor may be a component of the controller, a sub-controller for actuation, or alternatively, a part of another device. In general, the processor may execute program instructions and may manipulate data to perform the operations of the controller, including operations using algorithms, methods, functions, processes, histories, and workflows as described in the present disclosure.

[0018] With reference to Fig. 1 and Fig. 2, the present disclosure is directed to a work machine for calibrating an electro-hydraulic pump 105 having an open-center hydraulic system 110, the system for controlling an attachment actuator 115 coupled to the work machine. The electro-hydraulically controlled pump 105 outputs an outlet fluid flow (represented as the flow from the inlet 125) through the hydraulic circuit in response to a pump control signal 150. In the Fig. 1, the system 110 includes an electro-hydraulically controlled main attachment control valve 120 coupled to an independent electro-hydraulically controlled pump 105. The attachment control valve 120 is configured to control a flow ratio of fluid through the hydraulic circuit between the tank 135 and the attachment actuator 115 in response to a valve control signal 145. The attachment control valve 120 in this system 110 is of an "open-center" type, meaning that when the valve 120 is in the neutral position, a passage is opened to allow unobstructed flow of hydraulic fluid between the inlet 125 and the tank 135. In this system, the pressure in the hydraulic circuit 160 between the pump 105 and the valve 120 is measured by a pressure transducer 140. The pressure transducer 140 is arranged to measure a flow pressure in the hydraulic circuit 160 between the pump 105 and the attachment control valve 120.The position of pump 105 is controlled by hydraulic pressure piloted by an electro-hydraulic valve 152. The pressure that pilots pump 105 is proportional to the electrical current supplied to the control solenoid, hereinafter also referred to as pump control signal 150. A minimum pump control signal 205 begins to move the pump, and a maximum pump control signal 210 achieves full actuation of pump 105. A hysteresis band 212 may be present, dictating the difference between the "upward" flow curve 215 (as indicated by the dotted line) and the downward flow curve 220 (as indicated by the solid line). Fig. 2, the pump control signal 150 correlates with the pressure 153 measured downstream by the pressure transducer 140, whereby a precise change in flow as a function of a pressure change can be identified. The calibration system and method include identifying two calibration points (222a, 222b) and a hysteresis band 212. The two calibration points (222a, 222b) include the first pump threshold 222a for the pump in the pump flow curve 200, from which a minimum pump control signal 205 for actuating the pump 105 can be extrapolated, and the second pump threshold 222b for the pump 105 in the pump flow curve 200, from which a maximum pump control signal 210 for actuating the pump 105 can be extrapolated.

[0019] The central passage 155 of the open-center hydraulic valve 120 is typically closed at some rate when one of the working circuit passages 160 is opened. The timing of this transition can vary from valve to valve. Typically, the central passage 155 is not fully closed until the working circuit passages are at least partially open. This ensures that there is always a flow path, and the ratio of the openings formed in the central passage 155 and the working circuit passage dictates the flow split. However, there is a point in the valve spool's range of travel where the central passage 155 begins to narrow (often considerably) before the working circuit passage 160 is open.This restriction setting can be used to create a known restrictive path to the tank for fluid flow in hydraulic circuit 160, providing a method 300 for calibrating the first pump threshold 222a and the second pump threshold 222b for the pump 105, from which the minimum pump control signal 205 and the maximum pump control signal 210 can be extrapolated. Pump calibration establishes an area open downstream of the pump 105. Since the downstream area remains constant for the duration of the calibration, the precise fluid flow change is identifiable as a function of a change in the pressure 153 measured by the pressure transducer 140.

[0020] With reference to Fig. 3 with continued reference to Fig. 2 schematically illustrates an overview diagram for calibrating the electro-hydraulic pump 105 in an open-center hydraulic system 110. A controller 165 includes a non-transitory computer-readable medium with program instructions to cause a processor(s) to perform the following steps. Some conditions are required to optimize accuracy and / or precision during calibration. At step 305, the condition includes checking, before calibration, whether the engine speed is within an operating speed range. The engine speed must be sufficiently fixed to achieve consistent pump flow with respect to the pump control signal 150. This may include idle or a wide-open throttle based on the form of the program instructions. If the minimum engine speed condition is not met (i.e.within a normal operating range), the program instructions proceed to step 309 to halt the calibration routine and continue modifying the engine speed in step 307 before repeating step 305. Step 306 discloses another condition that includes checking, prior to calibration, whether the fluid in hydraulic circuit 160 is within an operating temperature range. Generally, fluid that is outside of normal operating temperature ranges may have a different viscosity and could potentially impact the accuracy of the calibration. For example, performing the calibration routine when the fluid temperature is below the normal operating temperature range may result in calibration results that reflect fluid properties that are different from normal operating conditions.As illustrated in steps 309 and 308, the program instructions require a delay in initiating calibration until the fluid has warmed to a temperature within the normal operating temperature range. Furthermore, the program instructions do not necessarily identify the exact minimum pump control signal 205, the maximum pump control signal 210, or an amount of hysteresis 212 in the pump flow curve 200. However, the program instructions identify calibration points, such as the first pump threshold 222a and the second pump threshold 222b along the pump flow curve 200, from which the minimum pump control signal 205 and the maximum pump control signal 210 can be extrapolated. After the engine speed and temperature are within defined ranges reflecting normal operating conditions, the program instructions proceed to calibration.At step 310, the method 300 includes calibrating a first pump threshold 222a for the pump 105 in the pump flow curve 200. At step 320, the method 300 then calibrates a second pump threshold 222b for the pump 105 in the pump flow curve 200. Finally, at step 330, the method 300 may further include determining a hysteresis band 212 in the pump flow curve 200. The calibration of the thresholds and the identification of the hysteresis may be rearranged or omitted and do not necessarily have to follow the described steps. The calibration is then completed in step 340. At step 350, the work machine may then proceed to control actuation of the attachment actuator by transmitting the calibrated pump control signals.

[0021] Fig. 4A and Fig. 4B illustrate the program instructions for calibrating the first pump threshold 222a in step 315, wherein FIG. 4B is a detailed diagram of steps 460 to step 480 in Fig. 4A. In a first step 410, the program instructions include causing a processor to set the pump control signal 150 to a low flow rate within a nominal control range. In a next step 420, the flow pressure 153 is recorded. Then, in step 430, the processor gradually increases the valve control signal until the flow pressure 153 changes by a defined value. The defined flow pressure change value indicates restricted fluid flow to the tank. The pressure transducer 140 observes a sudden increase in the flow pressure 153, reflecting this restriction setting.The program instructions for calibrating the first pump threshold 222a in the pump flow curve 200, from which the minimum pump control signal 205 can be extrapolated, further include steps 440 and 450, in which the valve control signal 145 is maintained at this constraint setting and the pump control signal 150 is neutralized. In one embodiment, for example, neutral may be defined as setting the valve control signal 145 to 0 mA.

[0022] The pressure 142 from pressure transducer 140 is recorded in step 412. Next, in step 420, the program instructions determine whether the restriction setting has been reached. After this restrictive path for pump flow has been established, the measurement of flow pressure 152 can be used to derive a relationship correlating the pump control signal 150 with a fluid flow change. In step 460, the pump control signal is incremented by a calibration step point. The calibration step point, in one embodiment, may be when the flow pressure 153 changes by a defined minimum value. Since the valve 155 has already established a restrictive path to the tank 135, any fluid flow generated by the pump 105 should produce an increase in the flow pressure 153 and a known point on the pump flow curve 200.Step 470 involves correlating the change in flow pressure 153 with a change in pump control signal 150. In step 480, these program instructions iteratively repeat increasing pump control signal 150 until flow pressure 153 increases by a target value. A target value may be defined by the design of the open-center hydraulic system. The target value must be sufficiently large to ensure that flow changes correspond to measurable changes in flow pressure 153. This can be accomplished by a first pass using "coarse increments" and "fine increments," as shown in box 490 in FIG. Fig. 4B. In step 491, the program instructions include setting the pump control signal to a calibration step point. If the flow pressure 153 does not change within a defined range, the pump control signal is increased by 10 mA in step 493. If the flow pressure 153 changes within a defined range, the pump control signal 150 is set to a different calibration step point in step 494. The program instructions use a fine increment, such as 1 mA, if the flow pressure 153 is not near or within the defined range, as illustrated in step 495. If the flow pressure 153 is near or within a defined range in step 496, then the calibration point for the first pump threshold 222a has been found. The speed of the pump 105 may dictate a pump outlet flow.

[0023] With reference to Fig. 5A and Fig. 5B, hysteresis 330 can be found in a similar manner. The hysteresis correlates better when the pump servo is fully actuated. In one embodiment, the program instructions in step 510 would set or maintain the valve control signal 145 at the restriction setting. Next, in step 520, the pump control signal 150 is set to the full pump command. This condition should generate a significant pressure drop across valve 155 due to the restriction setting. If the valve control signal 145 generates excessive flow pressure 153 at the restriction setting, a relief valve in hydraulic circuit 160 opens. The processor then records the flow pressure in step 530.In step 540, the program instructions cause the valve control signal 145 to slowly reduce, gradually opening the central passage 155 until the flow pressure 153 begins to fall below a relief setpoint. The reduction in the flow pressure 153 serves as a proxy for a fluid flow reduction. The recorded pressure drop indicates that the flow reduction has begun, and this is the hysteresis band 212 for the pump 105. In step 560, the program instructions include reducing the pump control signal 150 by a calibration step point and correlating the flow pressure 153 with the pump control signal 150 to identify a point on the pump flow curve 200. Reducing the pump control signal 150 and correlating the flow pressure 153 with the pump control signal 150 is repeated iteratively until the pressure drops by a second target value and continues to map the descent 220 of the pump flow curve 200.Similar to the first target value, the second target value is defined by the design of the open-center hydraulic system. Fig. 5B illustrates a detailed embodiment of steps 560 through 580. After the pump control signal 150 is set to the calibration step point in step 561, the program instructions estimate whether the flow pressure 153 is decreasing by a second target value. If not, the full pump command is neutralized, and the calibration step point is reduced by 10 mA in step 563. If the criterion is met, the pump control signal 150 continues to cycle on and off in 1 mA decrements with "fine" adjustments (steps 565-565) until the calibration point(s) are found in step 568.

[0024] With reference to Fig. 6A and Fig. 6B are the program instructions for finding a maximum pump control signal 210 from step 320 in Fig. 3, wherein the maximum pump control signal 210 is extrapolated from a second pump threshold 222b. Calibration of the second pump threshold 210 includes: adjusting the adjusted valve control signal 145 in step 610 to indicate that fluid flow to the tank 135 is restricted; setting the pump control signal 150 to the full pump command in step 620; and recording the flow pressure 153 in step 630. Next, in step 640, the program instructions include adjusting the pump control signal toward the minimum pump control signal 205 and increasing the pump control signal 150 by one calibration step point in step 650. The program instructions then check whether the flow pressure 153 is within a defined range of the recorded flow pressure 153 at the full pump command from step 630.The program instructions then iteratively repeat increasing the pump control signal by one calibration step point until the flow pressure 153 is within a defined range of the recorded flow pressure at the full pump command. Similar to the first pump threshold 222a, the program instructions adjust through "coarse" increments and "fine" increments.

[0025] With reference to Fig.7, a method 700 is shown for calibrating an electro-hydraulically controlled pump 105 on a work machine having an open-center hydraulic system 110. The system is for actuating an attachment coupled to the work machine (i.e., via an attachment actuator 115). The open-center hydraulic system 110 includes an attachment control valve 120 configured to control a flow ratio of fluid through a hydraulic circuit 160 between a tank 135 and an attachment actuator 115 in response to a valve control signal 145. The system also includes a pump 105 for controlling the outlet flow of fluid through the hydraulic circuit 160 in response to a pump control signal 150; a pressure transducer 140 disposed between the pump and the attachment control valve 120 for measuring a flow pressure 153 in the hydraulic circuit 160.

[0026] In a first step 710, the method includes calibrating a first pump threshold 222a in a pump flow curve 200 for the pump 105, wherein a minimum pump control signal 205 for actuating the pump 105 may be extrapolated from the first pump threshold 222a. At step 720, the method 700 may then determine a hysteresis band 212 in the pump flow curve 200. In a next step 730, the method 700 includes calibrating a second pump threshold 222b in the pump flow curve 200 for the pump 105, wherein a maximum pump control signal 210 for actuating the pump 105 below an unloading setpoint is extrapolated from the second pump threshold 222b. Finally, in step 740, the method 700 includes controlling actuation of the attachment actuator 115 by transmitting the calibrated pump control signals (222a, 222b) to the electro-hydraulically controlled pump 105.

[0027] One or more of the steps or acts in any of the methods, processes, or systems discussed herein may be omitted, repeated, or rearranged and are within the scope of the present disclosure.

[0028] While the foregoing describes exemplary embodiments of the present disclosure, these descriptions are not to be construed as limiting or restrictive. Rather, various variations and modifications may be made without departing from the scope of the appended claims. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 17 / 651,920

[0001]

Claims

[1] A work machine having an open-center hydraulic system for operating an attachment coupled to the work machine, the work machine comprising: a hydraulic circuit, an attachment control valve configured to control a flow ratio of a fluid through a hydraulic circuit between a tank and an attachment actuator in response to a valve control signal, an electro-hydraulically controlled pump for controlling an outlet flow of the fluid through the hydraulic circuit in response to a pump control signal, the hydraulic circuit being coupled to the attachment actuator, and a pressure transducer arranged to measure a flow pressure in the hydraulic circuit between the pump and the attachment control valve, and a calibration system for calibrating the pump to control the outlet flow of fluid through the open-center hydraulic system, the calibration system comprising a controller having a non-transitory computer-readable medium having a program instruction that causes a processor to: Checking whether a fluid temperature is within an operating temperature range before calibration, Check whether an engine speed is within an operating speed range before calibration, Calibrating a first pump threshold for the pump in a pump flow curve, wherein a minimum pump control signal for actuating the pump is extrapolated from the first pump threshold, Calibrating a second pump threshold for the pump in the pump flow curve, wherein a maximum pump control signal for actuating the pump below a relief setpoint is extrapolated from the second pump threshold, and Controlling an operation of the attachment actuator by transmitting the calibrated pump control signal to the electro-hydraulically controlled pump. [2] The work machine of claim 1, wherein the program instructions for calibrating the first pump threshold in the pump flow curve include: Setting the pump control signal to a low flow rate, Recording the flow pressure, Increasing the valve control signal by one pump calibration step point until the flow pressure changes by a defined value, wherein the defined flow pressure change value indicates a restricted fluid flow to the tank, Maintaining the valve control signal in a restriction setting, Neutralizing the pump control signal, Increase the pump control signal by the pump calibration step point, Correlating a flow pressure change with the change in the pump control signal to identify a point on the pump flow curve, and iteratively repeating the increase of the pump control signal until the flow pressure increases by a target value. [3] The work machine of claim 2, wherein the program instructions further comprise: Determining a hysteresis band in the pump flow curve, wherein the program instructions for determining a hysteresis band comprise: Setting the valve control signal to the restriction setting from calibrating the first pump threshold, Setting the pump control signal to full pump command, Recording the flow pressure, Reducing the valve control signal until the flow pressure drops by a defined value, Neutralize the full pump command, Reducing the pump control signal by one calibration step point, Correlating the flow pressure with the pump control signal to identify a point on the pump flow curve, and iteratively repeating the reduction of the pump control signal and correlating the flow pressure with the pump control signal until the pressure drops by a second target value. [4] The work machine of claim 3, wherein the program instructions for calibrating the second pump threshold in the pump flow curve include: Setting the adjusted valve control signal indicating that fluid flow to the tank is restricted, Setting the pump control signal to full pump command, Recording the flow pressure at the full pump command, Adjusting the pump control signal towards the minimum pump control signal, Increasing the pump control signal by one calibration step point, checking whether the flow pressure is within a defined range of the recorded flow pressure at the full pump command, and Iteratively repeating the process of increasing the pump control signal by one calibration step point until the flow pressure is within a defined range of the recorded flow pressure at the full pump command. [5] A work machine according to any one of claims 1 to 3, wherein the program instructions for calibrating the second pump threshold in the pump flow curve comprise: Setting the valve control signal to a restriction setting, the restriction setting indicating restricted fluid flow to the tank, Setting the pump control signal to the full pump command, Recording the flow pressure at the full pump command, Adjusting the pump control signal towards the minimum pump control signal, Increasing the pump control signal by one calibration step point, checking whether the flow pressure is within a defined range of the recorded flow pressure at the full pump command, and iteratively repeating the increase of the pump control signal by one calibration step point until the flow pressure is within a defined range of the recorded flow pressure. [6] A computer-readable medium for calibrating an electro-hydraulically controlled pump on a work machine having an open-center hydraulic system for actuating an attachment coupled to the work machine, the open-center hydraulic system including an attachment control valve configured to control a flow ratio of a fluid through a hydraulic circuit between a tank and an attachment actuator in response to a valve control signal, the pump for controlling an outlet flow of the fluid through the hydraulic circuit in response to a pump control signal, the hydraulic circuit including a pressure transducer arranged to measure a flow pressure in the hydraulic circuit between the pump and the attachment control valve, the computer-readable medium comprising a program instruction causing a processor of a controller to: Calibrating a first pump threshold for the pump in a pump flow curve, wherein a minimum pump control signal for actuating the pump is extrapolated from the first pump threshold, Calibrating a second pump threshold for the pump in the pump flow curve, wherein a maximum pump control signal for operating the pump below a relief setpoint is extrapolated from the second pump threshold, Controlling an operation of the attachment actuator by transmitting the calibrated pump control signal to the electro-hydraulically controlled pump. [7] The computer-readable medium of claim 6, wherein the program instructions for calibrating the first pump threshold in the pump flow curve comprise: Setting the pump control signal to a low flow rate, Recording the flow pressure, Increase the valve control signal by one pump calibration step point, Correlating a flow pressure change with the valve control signal to identify a point on the pump flow curve, and iteratively repeating the increase of the pump control signal until the flow pressure increases by a target value. [8] The computer-readable medium of claim 7, wherein the program instructions further comprise: Check that a fluid temperature is within an operating temperature range before calibration, Check that an engine speed is within an operating speed range before calibrating, Determining a hysteresis band in the pump flow curve, wherein the program instructions for determining a hysteresis band comprise: Setting the valve control signal to the restriction setting from calibrating the first pump threshold, Setting the pump control signal to full pump command, recording the flow pressure, Reducing the valve control signal until a flow pressure drops by a defined value, Reducing the pump control signal until the flow pressure changes by the defined value, Neutralize the full pump command, Reducing the pump control signal by one calibration step point, Correlating the flow pressure with the pump control signal to identify a point on the pump flow curve, and Iteratively repeating the calculation of the adjustment amount based on repeatedly reducing the pump control signal until the adjustment amount falls within a defined range. [9] The computer-readable medium of claim 8, wherein the program instructions for calibrating the second pump threshold in the pump flow curve comprise: Setting the adjusted valve control signal indicating that fluid flow to the tank is restricted, Setting the pump control signal to full pump command, Recording the flow pressure at the full pump command, Adjusting the pump control signal towards the minimum pump control signal, Increasing the pump control signal by one calibration step point, checking whether the flow pressure is within a defined range of the recorded flow pressure at the full pump command, and Iteratively repeating the process of increasing the pump control signal by one calibration step point until the flow pressure is within the defined range of the recorded flow pressure at the full pump command. [10] The computer-readable medium of any of claims 6 to 8, wherein the program instructions for calibrating the second pump threshold in the pump flow curve comprise: Setting the valve control signal to a restriction setting, the restriction setting indicating restricted fluid flow to the tank, Setting the pump control signal to full pump command, Recording the flow pressure at the full pump command, Adjusting the pump control signal towards the minimum pump control signal, Increasing the pump control signal by one calibration step point, checking whether the flow pressure is within a defined range of the recorded flow pressure at the full pump command, and iteratively repeating the increase of the pump control signal by one calibration step point until the flow pressure is within the defined range of the recorded flow pressure. [11] A method for calibrating an electro-hydraulically controlled pump on a work machine having an open-center hydraulic system for actuating an attachment coupled to the work machine, the open-center hydraulic system comprising an attachment control valve configured to control a flow ratio of a fluid through a hydraulic circuit between a tank and an attachment actuator in response to a valve control signal, the pump for controlling an outlet flow of the fluid through the hydraulic circuit in response to a pump control signal, a pressure transducer arranged to measure a flow pressure in the hydraulic circuit between the pump and the attachment control valve, the method comprising: Calibrating a first pump threshold in a pump flow curve for the pump, wherein a minimum pump control signal for actuating the pump is extrapolated from the first pump threshold, Calibrating a second pump threshold in the pump flow curve for the pump, wherein a maximum pump control signal for operating the pump below a relief setpoint is extrapolated from the second pump threshold, and Controlling an operation of the attachment actuator by transmitting the calibrated pump control signals to the electro-hydraulically controlled pump. [12] The method of claim 11, wherein calibrating the first pump threshold in the pump flow curve comprises: Setting the pump control signal to a low flow rate, Recording the flow pressure, Increasing the valve control signal by one pump calibration step point until the flow pressure changes by a defined value, wherein the defined flow pressure change value indicates a restricted fluid flow to the tank, Maintaining the valve control signal during restriction setting, Neutralizing the pump control signal, Increase the pump control signal by one pump calibration step point, Correlating a flow pressure change with the change in the pump control signal to identify a point on the pump flow curve, and iteratively repeating the increase of the pump control signal until the flow pressure increases by a target value. [13] The method of claim 12, further comprising determining a hysteresis band in the pump flow curve, wherein determining a hysteresis band comprises: Setting the valve control signal to the restriction setting from calibrating the first pump threshold, Setting the pump control signal to full pump command, Recording the flow pressure, Reducing the valve control signal until the flow pressure drops by a defined value, Neutralize the full pump command, Reducing the pump control signal by one calibration step point, Correlating the flow pressure change with the pump control signal to identify a point on the pump flow curve, and iteratively repeating the reduction of the pump control signal and correlating the flow pressure with the pump control signal until the pressure drops by a second target value. [14] A method according to any one of claims 11 to 13, further comprising: Verify that a fluid temperature is within an operating temperature range before calibration. [15] The method of any one of claims 11 to 14, wherein calibrating the second pump threshold in the pump flow comprises: Setting the valve control signal to a restriction setting, the restriction setting indicating restricted fluid flow to the tank, Setting the pump control signal to full pump command, Recording the flow pressure at the full pump command, Adjusting the pump control signal towards the minimum pump control signal, Increasing the pump control signal by one calibration step point, checking whether the flow pressure is within a defined range of the recorded flow pressure at the full pump command, and iteratively repeating the increment of the pump control signal by one calibration step point until the flow pressure is within the defined range of the recorded flow pressure.

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