Patent Application
20240392538
The present application claims priority to German Patent Application No. 10 2023 113 243.1 filed on May 22, 2023. The entire contents of the above-listed application are hereby incorporated by reference for all purposes.
The present disclosure relates to a method for determining or adapting a characteristic curve of a hydraulic component or mobile working machine.
Electrohydraulics are becoming increasingly important in the field of mobile working machines due to improved efficiency, automation of work processes, faster response times, load-independence and fine controllability of movements as well as configurable operator support. Electrohydraulics offer advantages over conventional, purely hydraulic controls.
In order to achieve a certain system behavior, it is advantageous to know the properties of the (electro) hydraulic components used, such as valves, and to store these in the form of a characteristic curve of the component on the machine control unit.
This is particularly important when controlling individual movements. For example, the flowing volume flow is set as precisely as possible for the precise movement of a hydraulic cylinder. The basis for this is knowledge of the opening cross-section as a function of the position of the associated valve, which can be defined via a characteristic curve. The characteristic curves provided by the component manufacturers are generally not sufficient, as they do not cover all effects that may occur.
Among other things, design-related flow forces in the component, friction effects in pipes and the pump as well as contact resistances in connecting elements have a significant influence on the behavior of the component. It may also be necessary to adjust the characteristic curve due to wear and other time-dependent influences during operation of the working machine.
Against this background, the object of the present disclosure is to provide a method for determining or adapting a characteristic curve of a hydraulic component or mobile working machine.
This object is achieved by the method with the features of the independent claim 1. Advantageous further embodiments of the disclosure are the subject matter of the dependent claims.
Consequently, a method is provided according to the disclosure for determining or adapting a characteristic curve of a hydraulic component or mobile working machine having the following steps:
The term “determining” is to be understood broadly and includes, for example, the terms detecting, calculating and/or measuring. In an example, the determination is performed via instructions stored in memory in a control unit.
Optionally, an identification can also be understood as determining. Optionally, an adaptation can also be understood as determining. In particular, it is conceivable that the adaptation is an online adaptation.
Optionally, it is provided that the volume flow is determined by measuring the volume flow, in particular using a measuring turbine.
Optionally, it is provided that the volume flow is determined from a rotational speed and a displacement volume of a pump, in particular of a hydraulic pump.
Optionally, it is provided that the displacement volume is determined from the pivot angle of the pump and/or from an electric control of the pump, preferably using a pump model.
Optionally, it is provided that the volume flow is determined from a movement of a consumer, in particular a hydraulic cylinder or hydraulic motor, and/or from a volume change of the consumer.
Optionally, it is provided that the movement of the consumer comprises a speed and/or rotational speed and/or in that the volume change is determined from an area, cubature and/or the movement of the consumer.
Optionally, it is provided that the pressure drop is determined by one, two or more than two pressure sensors. In particular, a pressure sensor can be arranged in a pipe system upstream of the component and a pressure sensor can be arranged downstream of the component.
Optionally, it is provided that the characteristic curve is determined or adapted by a Gaussian adjustment calculation, in particular using the least squares method and/or a recursive least squares algorithm.
Optionally, the characteristic curve is determined or adapted by determining more than one replacement parameter, in particular for different positions of the component.
Optionally, it is provided that the replacement parameter is determined from a division of the volume flow by the product of a system parameter and the square root of the difference of a first pressure drop in a first position of the component and of a second pressure drop in a second position of the component. The valve is a continuous valve (proportional valve). As the method runs online over the entire life cycle of the working machine, the replacement parameter is adapted not just for two different positions, but for all possible positions.
Optionally, it is that the system parameter comprises an orifice coefficient and/or a density of a hydraulic fluid.
Optionally, it is provided that the characteristic curve is stored and/or adapted on a machine control unit, for example in non-transitory memory of the control unit.
Optionally, it is provided that the component is or comprises an, in particular electrohydraulic, valve and/or in that the replacement parameter is a replacement cross-section of the valve.
Optionally, it is provided that the characteristic curve is determined or adapted during operation of the working machine. The characteristic curve is therefore determined or adjusted online on the working machine.
The disclosure also relates to a mobile working machine, in particular a hydraulic excavator, which is designed and/or has means for carrying out a method according to the disclosure.
Optionally, the working machine is a construction machine and/or equipped with an electric pump controller.
In other words, it is possible to bundle system influences and take them into account via a theoretical replacement parameter, such as a valve replacement cross-section. Optionally, the method is adaptive, runs online on the machine control unit, reacts to changes and/or thus ensures a defined control behavior over the entire life cycle of the mobile working machine.
At this point it is pointed out that the terms “a” and “one” do not necessarily refer to exactly one of the elements, although this is a possible embodiment, but can also denote a plurality of the elements. Similarly, the use of the plural also includes the presence of the element in question in the singular and, conversely, the singular also includes several of the elements in question. Furthermore, all of the features of the disclosure described herein may be claimed in any combination or in isolation from each other.
Further advantages, features and effects of the present disclosure are shown in the following description of preferred exemplary embodiments with reference to the figures, in which the same or similar components are designated by the same reference numerals. In the figures:
In a first exemplary embodiment of the method according to the disclosure, the known relationship between volume flow Q, orifice coefficient αD, cross-sectional area A, density ρ and pressure drop Δp at an orifice of a valve is used, which can be represented by the following equation 1:
In a first approximation, the orifice coefficient αD can be assumed to be constant. The density of the hydraulic fluid ρ is a system parameter of the mobile working machine 8 and can be determined as a function of the operating conditions.
If we now summarize all the existing values in the system parameter CB and reshape the relationship, the area of the valve can be described according to the following equation 2:
In order to determine a replacement cross-section of the valve that takes the system parameters and environmental influences into account, the real volume flow Qreal and the real pressure drop Δp across the valve are determined online, i.e. during operation of the working machine.
In addition, it is possible to define how and at what frequency the replacement cross-section is determined and thus the characteristic curve is adjusted.
During operation of the working machine, a desired movement is commanded via the control transmitter 10, translated by the machine control unit (ECU) 30 and forwarded to the valve 20.
Over the course of the machine's entire life cycle, various positions s of the valve 20 are specified.
If the volume flow Qreal, the pressure p1_real and the pressure p2_real are detected for each position s, the respective replacement cross-section AErsatz can be determined using the following equation 3:
In conjunction with the respective position s and a suitable mathematical method that defines a rule for the frequency of determination or adaptation, the characteristic curve of the valve can be determined and/or adapted.
Depending on the performance of the machine control unit 30, various options are available. For example, the Gaussian process and the recursive least squares (RLS) algorithm should be mentioned here.
The cross-section A of the valve 20 is shown on the y-axis and the valve position (deflection) s is shown on the x-axis.
In addition to the valve characteristic curve according to the manufacturer's specification HK, the determined replacement cross-sections AErsatz and the real characteristic curve IK determined and/or adapted from this are shown by small crosses. The determined characteristic curve(s) can then be used to control system operation via the ECU as described herein.
It can be seen that the deviation between the two characteristic curves HK and IK is large, especially with large valve deflection s. In this area in particular, it is advantageous to make an adjustment using the replacement cross-section AErsatz.
The control transmitter 10 transmits control commands to the machine control unit 30. The input value of a brake pedal 11 for the rotating mechanism is also transmitted to the machine control unit 30.
A pump 12 is also controlled by the machine control unit 30. The pump has a pivot angle sensor 14, which can be used to measure the pivot angle of the pump 12.
The flow rate of the hydraulic fluid between the pump 14 and valve block 20 can be measured using the measuring turbine 15.
The pressure drop across the valve block 20 can be determined by the pressure sensors 16 and 17.
The valve block 20 can control a translatory actuator in the form of a hydraulic cylinder 18 and/or a rotary actuator in the form of a hydraulic motor 22.
The valve block has valve 20a for actuating the hydraulic cylinder 18 and valve 20b for actuating the hydraulic motor 22.
The movement and/or position of the hydraulic cylinder 18 can be determined using a displacement transducer 19.
The movement and/or position of the hydraulic motor 22 can be determined using a rotational speed sensor 21.
There are various options for sensing the volume flow Qreal. Depending on the peripherals installed, there is the option of direct or indirect detection of the volume flow Qreal.
Direct detection is understood to mean measurement of the volume flow by a measuring turbine 15. As a measuring turbine causes additional costs and a permanent pressure drop or energy loss, it is primarily suitable for test and trial purposes.
Indirect detection offers several options for determining Qreal. This means that the volume flow at the pump 12 can be used as an approximation for Qreal. This can be calculated from the rotational speed and the displacement of the pump 12. By detecting the motor speed of the pump 12 and knowing the constant transmission ratio of the pump transmission, the rotational speed of the pump 12 is known to the machine control unit 30.
The displacement of pivot pumps is variable and can be detected by a pivot angle sensor 14.
If an electrically controlled pump 12 is used, the pivot angle sensor 14 can be omitted. In this case, it is possible to model the pump behavior and derive the pivot angle and thus the displacement volume from the electrical control IX1 of the pump 12.
The relationship between displacement volume Vg and control IX1 can be seen in the model in
In the model, a pressure dynamic GHyd(s) is determined from a characteristic curve of a pilot valve VK, which serves as an input variable for the characteristic curve of a pump controller PK, from which a pump dynamic GMech(s) and the displacement volume Vg are determined. The pump controller PK then controls pump operation.
As a further variant for determining Qreal, the volume flow at a consumer can be used instead of the pump volume flow.
This can be done differently depending on the sensors installed and the type of consumer. In the case of translatory consumers, e.g. in the form of a hydraulic cylinder 18, the speed can be detected with a displacement transducer 19 and the volume flow can be calculated using the geometry or the piston area.
In comparison, in the case of rotary consumers, for example in the form of a hydraulic motor 22, the rotational speed is measured by means of a speed sensor 21 and calculated to the volume flow by means of the cubature.
Pressure sensors 16, 17 are provided to determine the pressure difference Δp.
As already explained, the replacement cross-section includes all parameters and environmental influences of the entire system. However, certain included effects do not occur twice in multi-section operation, such as parallel actuation of a hydraulic cylinder and a hydraulic motor (two section valves). Therefore, if a plurality of cross-sections is considered in parallel operation and used for further calculations, it is advisable to take the unwanted duplication into account. A suitable method for this is a comparative analysis. For this purpose, the determined individual section cross-sections of the valve can be added together and compared with a determined multi-section cross-section. This makes it possible to prevent unwanted, unreal duplication of effects.
The method actions described herein may be implemented as instructions stored in memory of the ECU 30, which ECU communicates via one or more signal lines as illustrated to one or more sensors, transmitters, and actuators as described herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2023 113 243.1 | May 2023 | DE | national |
