Variable pump return stroke error open loop compensation method and device based on hysteresis model

Abstract

The application discloses a variable pump return stroke error open-loop compensation method and device based on a hysteresis model, which first acquires the relationship between the output flow of the variable pump and the input current of the variable pump control valve, obtains a control current-output flow curve, and fits a linear segment curve by using a linear regression method; then, a play operator is improved so as to simulate the dead zone and saturation phenomenon in the plunger pump flow curve, and a hysteresis positive model is constructed according to the regression equation of the linear segment curve; finally, a slope is designed in the improved play operator to simulate the instantaneous up and down jump, the inverse effect is realized, a compensation inverse model is designed according to the hysteresis positive model, and the compensation inverse model is placed into a controller to perform compensation. The application completes the compensation of the hysteresis and the dead zone phenomenon, improves the linearity of the variable pump flow control and the stability of the variable pump flow output by adding no other devices and modifying only the control program and adding the inverse model before inputting for compensation.

Description

Technical Field

[0001] This invention relates to the field of engineering machinery, and in particular to a method and apparatus for open-loop compensation of return error of variable pumps based on a hysteresis model. Background Technology

[0002] Axial variable displacement piston pumps are a crucial component of power supply systems, and the stability of their flow control plays a vital role in ensuring a high-quality power supply. Hysteresis phenomena, such as electromagnet hysteresis and return error of the variable displacement mechanism, significantly impact the linearity of flow control. Currently, compensation for hysteresis in axial variable displacement piston pumps typically involves installing flow sensors to achieve a closed-loop flow control, but this leads to increased equipment costs and insufficient installation space. There is a need to investigate a flow control method that compensates for the return error of axial variable displacement piston pump flow control without adding additional hardware, thereby improving the linearity of the variable displacement pump flow control. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing technologies by proposing an open-loop compensation method and device for the return error of a variable pump based on a hysteresis model.

[0004] The objective of this invention is achieved through the following technical solution: an open-loop compensation method for return error of a variable pump based on a hysteresis model, the method comprising the following steps:

[0005] (1) Acquire flow curve: Obtain the relationship between the output flow of the variable pump and the input current of the variable pump control valve to obtain the control current-output flow curve;

[0006] (2) Fitting the flow rate curve: The linear segment curve is fitted using the linear regression method;

[0007] (3) Establish a hysteresis positive model: Improve the play operator so that it can simulate the dead zone and saturation phenomenon in the flow curve of the plunger pump, and construct a hysteresis positive model based on the regression equation of the linear segment curve.

[0008] (4) Design the compensation inverse model: Design the slope in the improved play operator to simulate the instantaneous up and down jump, realize the inverse effect of the improved play operator, and design the compensation inverse model based on the hysteresis positive model;

[0009] (5) The compensation inverse model is put into the controller for compensation.

[0010] Furthermore, the variable pump was operated under standard conditions, and the control current was increased from 0 to the maximum and then decreased from the maximum to 0. At the same time, the control current and output flow were recorded to obtain the control current-output flow hysteresis curve on one side. The electromagnet flow hysteresis curve on the other side was measured in the same way.

[0011] Furthermore, the fitted linear segment curve is divided using the second derivative method, the specific process of which is as follows:

[0012] (2.1) Based on the monotonic nature of the control input, the time-flow rate curve is divided into an ascending segment and a descending segment;

[0013] (2.2) Plot the control quantity-flow rate curves for the rising and falling segments respectively, and resample the input quantities at equal intervals;

[0014] (2.3) Find the maximum and minimum points of the second derivative of the control quantity-flow curve for the rising and falling segments of the resampled data respectively, and obtain the two inflection points of the flow curve. Divide the curve into dead zone, rising and falling linear segments and saturation segment.

[0015] (2.4) The linear segments are truncated and fitted to obtain the linear fitting equations for the rising and falling segments.

[0016] Furthermore, the improved play operator adds bias parameters, slope parameters, upper and lower output limits, enabling it to simulate dead zones and saturation phenomena in the flow curve of a plunger pump.

[0017] Furthermore, by placing the compensation inverse model before the variable pump input within the controller, the dead zone and hysteresis of the variable pump flow control are eliminated, thereby compensating for the variable pump hysteresis error.

[0018] Secondly, the present invention also provides a variable pump return error open-loop compensation device based on a hysteresis model, comprising a memory and one or more processors, wherein the memory stores executable code, and when the processor executes the executable code, it implements the variable pump return error open-loop compensation method based on a hysteresis model.

[0019] Thirdly, the present invention also provides a computer-readable storage medium having a program stored thereon, which, when executed by a processor, implements the aforementioned open-loop compensation method for variable pump return error based on a hysteresis model.

[0020] Fourthly, the present invention also provides a computer program product, including a computer program, which, when executed by a processor, implements the aforementioned open-loop compensation method for variable pump return error based on a hysteresis model.

[0021] The beneficial effects of this invention are as follows: The open-loop compensation method for variable pump hysteresis error based on a hysteresis model proposed in this invention is based on the play operator in electromagnet hysteresis research. This operator has irreversible characteristics and is often only used for modeling hysteresis phenomena rather than compensation. The improved play operator proposed in this invention can simulate and compensate for the dead zone of variable control while modeling hysteresis phenomena. Simultaneously, an inverse method for the improved play operator is proposed, solving the problem of the play operator's irreversibility. The method of this invention uses experimental measurement and flow curve fitting, and uses the improved play operator to establish a fitting positive model and a compensation inverse model. Without adding other components, only the control program is modified to add the inverse model before the input for compensation, completing the compensation for hysteresis and dead zone phenomena, improving the linearity of variable pump flow control, and improving the stability of variable pump flow output. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 The flowchart of an open-loop compensation method for return error of a variable pump based on a hysteresis model is provided by the present invention.

[0024] Figure 2 This is a schematic diagram of the control current and flow rate curves collected.

[0025] Figure 3 This is a schematic diagram illustrating the division of the rising and falling segments in the process of fitting the flow rate curve.

[0026] Figure 4 This is a schematic diagram of resampling during the process of fitting the flow rate curve.

[0027] Figure 5 A schematic diagram of second derivative analysis and inflection point division for fitting the flow rate curve.

[0028] Figure 6 This is a schematic diagram of the linear fitting segment during the process of fitting the flow rate curve.

[0029] Figure 7 This is a schematic diagram of the improved play operator.

[0030] Figure 8 This is a schematic diagram of fitting a hysteresis positive model.

[0031] Figure 9 A schematic diagram for improving the inversion of the play operator.

[0032] Figure 10 A schematic diagram for inverting the hysteresis positive model.

[0033] Figure 11 This is a schematic diagram illustrating the relationship between each operator and the model.

[0034] Figure 12 This is a schematic diagram of the inverse model with compensation.

[0035] Figure 13 This is a diagram illustrating the compensation effect.

[0036] Figure 14 This is a structural diagram of a variable pump return error open-loop compensation device based on a hysteresis model provided by the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below with reference to the accompanying drawings and examples. It should be understood that the specific examples described herein are merely illustrative and not intended to limit the invention.

[0038] like Figure 1 As shown, this invention provides an open-loop compensation method for the return error of a variable pump based on a hysteresis model. This method consists of five steps: acquiring flow curves, fitting flow curves, establishing a hysteresis positive model, designing a compensation inverse model, and placing it into the controller for compensation. First, the relationship between the output flow of the variable pump and the input current of the variable pump control valve is recorded using a test bench, resulting in a control current-output flow curve. Then, a linear segment of the curve is extracted and fitted using linear regression. Next, a hysteresis positive model is built based on the regression equation of the linear segment curve. Then, a compensation inverse model is designed based on the positive model, and finally, the inverse model is placed before the variable pump input in the controller to compensate for the return error of the variable pump.

[0039] (1) Acquiring flow rate curves: The variable pump was operated under standard conditions. The control valve current was increased from 0 to maximum and then decreased back to 0. Simultaneously, the control current and output flow rate were recorded to obtain the control current-output flow rate hysteresis curve on one side. The flow rate hysteresis curve on the other side was measured using the same method. Finally, the flow rate hysteresis curve for the entire control range was obtained. The measured flow rate curve on one side was obtained as follows: Figure 2 As shown.

[0040] (2) Fitting the flow rate curve: This invention uses the second derivative segmentation method, as follows:

[0041] Rising and falling segment division: such as Figure 3 As shown, based on the monotonic nature of the control input, the time-flow rate curve is divided into an ascending segment and a descending segment.

[0042] Resampling: such as Figure 4 As shown, the control quantity-flow rate curves for the rising and falling segments are plotted respectively, and the input quantities are resampled at equal intervals.

[0043] Second derivative analysis and inflection point division: such as Figure 5 As shown, the second derivative of the resampled data is calculated. Smoothing filtering is required before each derivative calculation to reduce the impact of noise. The maximum and minimum points of the second derivative of the control quantity-flow rate curve are calculated for the rising and falling segments, respectively, resulting in two inflection points of the flow rate curve. The curve is divided into three segments: dead zone, rising / falling linear segment, and saturation segment.

[0044] Linear fitting segment truncation: such as Figure 6 As shown, by extracting 60% of the middle portion of the two linear segments mentioned above, we obtain the linear fitting segment of the rising / falling segment.

[0045] Linear analysis: Perform linear analysis on the linearly fitted segment to obtain the linear fitting equation for the rising / falling segment. Specifically:

[0046] The fitting equation for the rising segment is:

[0047] Descent segment fitting equation:

[0048] (3) Establish a hysteresis positive model:

[0049] (3.1) Improvement of the play operator

[0050] The original play operator is:

[0051]

[0052] The improved play operator of this invention is:

[0053]

[0054] The improved calculation method for each parameter in the play operator is as follows:

[0055]

[0056]

[0057]

[0058]

[0059]

[0060] in, Indicates the operator output, This represents the output of the operator at the previous time step. Indicates the control input quantity. Indicates the dead zone point of the descent segment. Indicates the dead zone point of the rising segment. Indicates operator parameters, Represents the slope parameter. Indicates the slope of the descending segment. Indicates the slope of the rising segment. Indicates the bias parameter. This indicates the upper limit of the operator's output. This indicates the lower bound of the operator output. This represents the saturation flow rate. Compared to the regular play operator, the improved play operator adds a bias parameter. Slope parameters Output limit Output lower limit .like Figure 7 As shown, the improved operator can effectively simulate the dead zone and saturation phenomenon in the flow curve of a plunger pump.

[0061] (3.2) As Figure 8 As shown, a hysteresis positive model is established using the regression equation and the improved play operator:

[0062]

[0063] in, This indicates the output flow rate.

[0064] (4) Design the compensation inverse model:

[0065] (4.1) Inverting the improved play operator: Neither the play operator nor the improved play operator itself can be inverted, requiring special methods to solve, such as... Figure 9 As shown, this invention employs a very large slope. Simulating instantaneous up-and-down jumps to achieve the effect of inverse calculation, the slope... The value should be much larger than the slope parameter φ, typically 100 times the value of φ. The resulting inverse improved play operator is as follows:

[0066]

[0067] (4.2) Compensation inverse model calculation: such as Figure 10 As shown, based on the above inverse formula and the hysteresis positive model, the compensation inverse model is obtained as follows:

[0068]

[0069] in, This represents the command flow rate, and 𝑘 is the slope parameter.

[0070] In steps (3) and (4), the relationships between each operator and the model are summarized as follows: Figure 11 As shown, the process of fitting the compensation inverse model using the inverse improvement operator is achieved by inverting the fitted hysteresis positive model.

[0071] (5) Implement compensation using the controller: such as Figure 12 As shown, by inserting the designed compensation inverse model before the input stage, the open-loop compensation effect is achieved, as follows: Figure 13 As shown, the present invention eliminates the dead zone and hysteresis of variable pump flow control, improves control linearity, and ensures the stability of flow control.

[0072] Corresponding to the aforementioned embodiment of the variable pump return error open-loop compensation method based on a hysteresis model, the present invention also provides an embodiment of a variable pump return error open-loop compensation device based on a hysteresis model.

[0073] See Figure 14 The present invention provides a variable pump return error open-loop compensation device based on a hysteresis model, comprising a memory and one or more processors. The memory stores executable code, and when the processor executes the executable code, it is used to implement a variable pump return error open-loop compensation method based on a hysteresis model in the above embodiment.

[0074] The embodiment of the variable pump return error open-loop compensation device based on a hysteresis model provided by this invention can be applied to any device with data processing capabilities, such as a computer. The device embodiment can be implemented in software, hardware, or a combination of both. Taking software implementation as an example, as a logical device, it is formed by the processor of any data processing device loading the corresponding computer program instructions from non-volatile memory into memory for execution. From a hardware perspective, such as... Figure 14 The diagram shown is a hardware structure diagram of any data processing-capable device, including a variable pump return error open-loop compensation device based on a hysteresis model provided by the present invention. (Except for...) Figure 14 In addition to the processor, memory, network interface, and non-volatile memory shown, any data processing device in the embodiment may also include other hardware depending on the actual function of the data processing device, which will not be described in detail here.

[0075] The specific implementation process of the functions and roles of each unit in the above device can be found in the implementation process of the corresponding steps in the above method, and will not be repeated here.

[0076] For the device embodiments, since they basically correspond to the method embodiments, the relevant parts can be referred to in the description of the method embodiments. The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of the present invention according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0077] This invention also provides a computer-readable storage medium storing a program thereon, which, when executed by a processor, implements an open-loop compensation method for variable pump return error based on a hysteresis model as described in the above embodiments.

[0078] The computer-readable storage medium can be an internal storage unit of any data processing device described in any of the foregoing embodiments, such as a hard disk or memory. The computer-readable storage medium can also be an external storage device of any data processing device, such as a plug-in hard disk, smart media card (SMC), SD card, flash card, etc., equipped on the device. Furthermore, the computer-readable storage medium can include both internal storage units and external storage devices of any data processing device. The computer-readable storage medium is used to store the computer program and other programs and data required by the data processing device, and can also be used to temporarily store data that has been output or will be output.

[0079] The present invention also provides a computer program product, including a computer program, which, when executed by a processor, implements the aforementioned open-loop compensation method for variable pump return error based on a hysteresis model.

[0080] The above embodiments are used to explain and illustrate the present invention, but not to limit the present invention. Any modifications and changes made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A method for open-loop compensation of return error of a variable pump based on a hysteresis model, characterized in that, The method includes the following steps: (1) Acquire flow curve: Obtain the relationship between the output flow of the variable pump and the input current of the variable pump control valve to obtain the control current-output flow curve; (2) Fitting the flow rate curve: The linear segment curve is fitted using the linear regression method; (3) Establish a hysteresis positive model: Improve the play operator so that it can simulate the dead zone and saturation phenomenon in the flow curve of the plunger pump, and construct a hysteresis positive model based on the regression equation of the linear segment curve; (4) Design the compensation inverse model: Design the slope in the improved play operator to simulate the instantaneous up and down jump, realize the inverse effect of the improved play operator, and design the compensation inverse model based on the hysteresis positive model; (5) The compensation inverse model is placed into the controller for compensation.

2. The open-loop compensation method for return error of a variable pump based on a hysteresis model according to claim 1, characterized in that, The variable pump was operated under standard conditions. The control current was increased from 0 to the maximum and then decreased from the maximum to 0. The control current and output flow were recorded at the same time to obtain the control current-output flow hysteresis curve on one side. The flow hysteresis curve of the electromagnet on the other side was measured in the same way.

3. The open-loop compensation method for return error of a variable pump based on a hysteresis model according to claim 1, characterized in that, The second-order derivative segmentation method is used to fit the linear segment curve. The specific process is as follows: (2.1) Based on the monotonic nature of the control input, the time-flow rate curve is divided into an ascending segment and a descending segment; (2.2) Plot the control quantity-flow rate curves for the rising and falling segments respectively, and resample the input quantities at equal intervals; (2.3) Find the maximum and minimum points of the second derivative of the control quantity-flow curve for the rising and falling segments of the resampled data respectively, and obtain the two inflection points of the flow curve. Divide the curve into dead zone, rising and falling linear segments and saturation segment. (2.4) The linear segments are truncated and fitted to obtain the linear fitting equations for the rising and falling segments.

4. The open-loop compensation method for return error of a variable pump based on a hysteresis model according to claim 1, characterized in that, The improved play operator adds bias parameters, slope parameters, upper and lower output limits to enable it to simulate dead zones and saturation phenomena in the flow curve of a plunger pump.

5. The open-loop compensation method for return error of a variable pump based on a hysteresis model according to claim 1, characterized in that, By placing the compensation inverse model before the variable pump input within the controller, the dead zone and hysteresis of the variable pump flow control are eliminated, thereby compensating for the variable pump hysteresis error.

6. A variable pump return error open-loop compensation device based on a hysteresis model, comprising a memory and one or more processors, wherein the memory stores executable code, characterized in that, When the processor executes the executable code, it implements a variable pump return error open-loop compensation method based on a hysteresis model as described in any one of claims 1-5.

7. A computer-readable storage medium having a program stored thereon, characterized in that, When the program is executed by the processor, it implements the open-loop compensation method for variable pump return error based on the hysteresis model as described in any one of claims 1-5.

8. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the open-loop compensation method for variable pump return error based on a hysteresis model as described in any one of claims 1-5.

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