Patent Application
20230265870
The present disclosure relates to a work machine and a method for calibrating an electrohydraulic pump in an open center hydraulic system.
In industrial or construction work machines, a system of hydraulic pumps, valves, and actuators are often used to produce motion for an implement. Various technologies exist to manage the control of these hydraulic devices. Systems can be developed that blend elements of each available technology. Some systems rely purely on hydromechanical means of controlling pumps, valves, and actuators (also commonly referred to as manual or pilot operated controls). Other systems, however, incorporate electronic devices for control (commonly known as electro-hydraulic controls). Electro-hydraulic devices can be utilized to control hydraulic pumps and valves. These devices can take on various design forms. One embodiment for an electro-hydraulic control device is the use of an electronic solenoid to induce electro-magnetic forces either directly or indirectly on a valve spool by subjecting the solenoid to a given electrical current. The actuation of the valve spool by the solenoid is used to induce a given hydraulic pressure, which may then be used to pilot a main stage valve spool or pump. This provides the ability to electronically control the flow or pressure in a hydraulic circuit, which is ideal for implementation in complex control systems that utilize microcontrollers. Depending on the application of electro-hydraulic devices in a given system, a method for calibrating components is often necessary to optimize system performance. A nominal input/output relationship for a device can be determined based on the component design. However, manufacturing tolerances may deviate the system from theoretical nominal performances from one component to the next. Calibration routines are often developed to account for such variances. Therein lies an opportunity to develop a calibration routine optimized to account for variances in pump performance in an open center hydraulic system.
This summary is provided to introduce a selection of concepts that are further described below in the detailed description and accompanying drawings. This summary is not intended to identify key or essential features of the appended claims, nor is it intended to be used as an aid in determining the scope of the appended claims.
The present disclosure relates to an apparatus with a calibration system, and method of calibrating the pump in an open center hydraulic system on a work machine. The work machine comprises an open center hydraulic system, and a calibration system. The open center hydraulic system controls actuation of the implement. The open center hydraulic system includes an implement control valve configured to control a flow of the fluid to and from an implement actuator in response to a first control signal. The hydraulic system also includes an electro-hydraulically controlled pump for controlling the outlet flow of the fluid through a hydraulic circuit in response to a second control signal. This hydraulic circuit is coupled to the implement actuator. A pressure transducer is positioned for measuring a pressure in the hydraulic circuit between the pump and the implement control valve. The calibration system calibrates the pump for controlling the flow of fluid through the open center hydraulic system. The calibration system includes a controller having a non-transitory computer readable medium with a program instruction to do the following steps. The program instruction includes calibrating a first threshold and second threshold for the pump in a pump-flow curve and determining a hysteresis band in the pump-flow curve. The first threshold includes a minimum current command to actuate the pump. The second threshold includes a maximum current command to actuate the pump below a relief setpoint.
Calibrating the first threshold for the pump in the pump-flow curve may comprise of setting the pump at a constant flowrate, identifying an implement control valve command for a restriction setting, recording the pump pressure, initializing a pump calibration step point, ramping the first control signal until the pressure changes to a predetermined value, correlating the pressure change to the change in the flow of fluid to the implement actuator to identify a given point on the pump-flow curve, outputting an adjustment signal for adjusting the first threshold, and iteratively repeating the outputting of the adjustment signal based on a repeated ramping of the first control signal until the adjustment signal falls within a predetermined range.
Calibrating the second threshold for the pump in the pump-flow curve may comprise of setting the pump at a constant flowrate, identifying an implement control valve command for a restriction setting, ramping the second control signal beyond a nominal full stroke actuation of the implement, recording the pump pressure, ramping the first control signal, outputting an adjustment signal for adjusting the second threshold, and iteratively repeating the outputting of the adjustment signal based on a repeated ramping of the second control signal until the adjustment signal falls within a predetermined range.
Determining the hysteresis band in the pump-flow curve may comprise of ramping the second control signal until the pressure drops, determining a pressure drop target by correlating the pressure to a change in the flow of fluid to the implement actuator, outputting an adjustment signal for adjusting the pressure drop target, and iteratively repeating the output of the adjustment signal based on a repeated ramping of the second control signal until the adjustment signal falls within a predetermined range.
Prior to the calibration, the fluid will be within an operating temperature range prior to proceeding with the calibrating process.
Prior to the calibration, the engine speed will be within an operating speed range prior to proceeding with the calibrating process.
Other features and aspects of the disclosure will become apparent by consideration of the following detailed description and accompanying drawings.
Before any 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 the arrangement of components set forth in the following description or illustrated in the following drawings. The disclosure is capable of supporting other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
As used herein, unless otherwise limited or modified, lists with elements that are separated by conjunctive terms (e.g., “and”) and that are also preceded by the phrase “one or more of” or “at least one of” indicate configurations or arrangements that potentially include individual elements 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” indicates 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).
As used herein, the term “controller” is a computing device including a processor and a memory. The “controller” may be a single device or alternatively multiple devices. The controller may further refer to any hardware, software, firmware, electronic control component, processing logic, processing device, individually or in any combination, including without limitation: application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality.
The term “processor” is described and shown as a single processor. However, two or more processors can 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. Generally, the processor can execute program instructions and can manipulate data to perform the operations of the controller, including operations using algorithms, methods, functions, processes, flows, and procedures as described in the present disclosure.
With references to
In the open center hydraulic valve 120, the center passage 155 is typically closed off at some rate as one of the work circuit passages 160 is opened up. The timing of this transition can vary from valve to valve, but typically the center passage 155 is not completely closed off until the work circuit passages 160 are at least partially opened. This ensures that there is always a path for flow, and the ratio of the orifices formed in the center passage 155 and the work circuit passage 160 dictate the flow split. There is, however, a point in the valve spool travel range wherein the center passage 155 starts to restrict (often substantially) before the work circuit passage 160 opens up. This “restriction setting” 307 can be used to create a known restrictive path for pump flow, which provides a method for calibrating the “minimum” calibration point 222a for the hydraulic pump 105. Pump calibration establishes an area opening downstream of the pump 105. If that area remains consistent for the duration of the calibration, a precise change in flow is identifiable as a function of a change in pressure.
Now referencing
The flow diagram for calibrating the “minimum current” command 222a to actuate the pump is shown in
Now turning to
Once the hysteresis band 212 is determined, a final calibration identifies the second threshold 210 (or true max flow for the pump).
One or more of the steps or operations in any of the methods, processes, or systems discussed herein may be omitted, repeated, or re-ordered and are within the scope of the present disclosure.
While the above describes example embodiments of the present disclosure, these descriptions should not be viewed in a restrictive or limiting sense. Rather, there are several variations and modifications which may be made without departing from the scope of the appended claims.
