High-precision position control method for dual-variable hydraulic system based on energy efficiency decoupling

Abstract

The present invention discloses a high-precision position control method for a dual-variable hydraulic system based on energy efficiency decoupling, and the steps include: 1. Determine the initial parameters of the dual-variable hydraulic system operation through energy efficiency decoupling; 2. In the process of controlling the movement of the hydraulic cylinder, considering the different response speeds of the variable speed motor and the variable pump to the output flow, combine the external load pressure and displacement following error, set a fuzzy controller, and adjust the initial parameters according to the pre-set fuzzy control rules; 3. When the following error measured by the system is large, adjust the displacement of the variable pump; when the following error measured by the system is small, adjust the speed of the variable speed motor. The present invention can not only improve the position tracking accuracy and response speed of the dual-variable hydraulic system, but also reduce the energy consumption of the hydraulic system.

Description

Technical Field

[0001] The invention relates to the field of position tracking control of a dual variable hydraulic system, in particular to a high-precision position control method of a dual variable hydraulic system based on energy efficiency decoupling. Background Art

[0002] With the increasing popularity of energy-saving and environmental protection concepts and the continuous improvement of product precision requirements in downstream industries, precision forming hydraulic equipment is developing in the direction of high precision and low energy consumption. In recent years, as the manufacturing precision requirements of large equipment have become higher and higher, the demanders have higher and higher requirements on the load control characteristics of the control system, especially force control and position control.

[0003] The valve-controlled asymmetric cylinder electro-hydraulic system based on the throttling principle has the advantages of fast response speed, high control accuracy, and simple structure. It is widely used in high-precision positioning devices such as industrial robots, aviation flight control, and automated manufacturing equipment. However, the valve-controlled system has large throttling losses and overflow losses, low system efficiency, severe heat generation, and rapid component aging. When the actuator is loaded, the load power does not match the output power of the drive system, and the drive system has a large amount of energy loss, generally consuming more than 70% of the energy.

[0004] Compared with valve control system, pump control system has the advantages of high energy utilization, compact layout and significant energy saving effect. In today's increasingly tight energy situation, pump control system has a more advantageous application prospect. With the rapid development of variable speed motors and variable displacement pumps, the output power of the drive unit and the load power can be matched by adjusting the motor speed and pump displacement. The three common ways to achieve power matching by adjusting the operating parameters of the hydraulic system are: variable speed fixed displacement system, fixed speed variable displacement system and variable speed variable displacement system. Research in recent years has shown that the energy saving potential of variable speed variable displacement drive system is significantly better than the other two.

[0005] Compared with other hydraulic systems, the hydraulic system using variable speed and variable displacement drive system has higher energy efficiency, but the dynamic response under local working conditions is low. Therefore, how to balance the energy efficiency and dynamic characteristics of the dual variable hydraulic system is the focus and difficulty of the future development of the dual variable hydraulic system. Summary of the invention

[0006] In order to solve the problems in the background technology, the present invention provides a high-precision position control method for a dual-variable hydraulic system based on energy efficiency decoupling, in order to improve the position tracking accuracy and response speed of the dual-variable hydraulic system under different working conditions and reduce the energy consumption of the hydraulic system.

[0007] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is as follows:

[0008] The high-precision position control method of a dual-variable hydraulic system based on energy efficiency decoupling of the present invention is characterized in that it is carried out according to the following steps:

[0009] Step 1: After the dual variable hydraulic system is started, according to the actual working conditions of the system, the combination of the speed of the variable speed motor and the displacement of the variable pump that makes the hydraulic system most energy efficient is obtained through energy efficiency decoupling, and is used as the initial operating parameters of the dual variable hydraulic system, the initial operating parameters being the speed of the variable speed motor N0 and the displacement of the variable pump V0;

[0010] Step 2: Define variable k and initialize k=1;

[0011] Step 3: Use a pressure sensor to collect the load pressure signal of the k-th stage hydraulic cylinder in the dual variable hydraulic system, and use a displacement sensor to collect the displacement signal of the k-th stage hydraulic cylinder, so as to calculate the external load pressure P of the k-th stage hydraulic cylinder. L,k and displacement following error E k ;

[0012] Step 4: According to the external load pressure P L,k and displacement following error E k , get the speed adjustment parameter ΔN of the variable speed motor in the kth stage k Or the displacement adjustment parameter ΔV of the variable displacement pump k ;

[0013] Step 5: Adjust the speed of the variable speed motor according to the parameter ΔN k Or the displacement adjustment parameter ΔV of the variable displacement pump k , for the speed N of the variable speed motor in the k-1th stage k-1 Or the displacement V of the variable pump k-1 Adjust to get the speed N of the variable speed motor in the kth stage k Or the displacement V of the variable pump k , and used as the kth order operating parameter of the dual variable hydraulic system; where: N k =N k-1 +ΔN k , V k =V k-1 +ΔV k ;

[0014] Step 6: When the displacement follows the error E k Greater than the error distribution standard definition parameter E d When adjusting the displacement V of the variable pump k ; When the displacement follows the error E k Less than the error distribution standard definition parameter E d When adjusting the speed of the variable speed motor N k ;

[0015] Step 7: Assign k+1 to k and return to step 3 to execute sequentially until the displacement follows the error E k Control ends when it reaches zero or the dual variable hydraulic system runs to the specified position.

[0016] The high-precision position control method described in the present invention is also characterized in that the process of energy efficiency decoupling is: first, an energy efficiency database is established through experimental methods, and then during the operation of the dual-variable hydraulic system, according to the actual output pressure and output flow of the variable pump, the corresponding combination of the speed of the variable speed motor and the displacement of the variable pump is obtained by querying the energy efficiency database.

[0017] The process of establishing the energy efficiency database includes:

[0018] Step 3.1, according to the actual working requirements of the dual variable hydraulic system, use sensors to collect the output pressure and output flow information of the variable pump during the entire operation of the dual variable hydraulic system, and use the horizontal axis to represent the output pressure P of the variable pump and the vertical axis to represent the output flow Q of the variable pump, thereby establishing a plane coordinate system related to the output pressure P and the output flow Q;

[0019] Step 3.2: Divide the measured output pressure P into n ranges, denoted as P1, P2, …, P i ,…,P n ; The output flow Q is evenly divided into m ranges, denoted as Q1, Q2, …, Q j ,…,Q m , thus dividing the plane coordinate system into n×m cells of the same size, and the coordinates of any cell are marked as (i, j), where P i Indicates the i-th output pressure range, Q j represents the jth output flow range;

[0020] Step 3.3: Calculate the unit power ratio γ using formula (1):

[0021]

[0022] In formula (1): P c(i,j) is the system output power under the working condition represented by the cell with coordinates (i, j); P w It is the total power output of the system during a working cycle;

[0023] According to the size of γ, the degree of secondary division is divided into three levels:

[0024] When γ is less than γ1, the level of secondary division is level I, that is, the original cells are not divided;

[0025] When γ is greater than or equal to γ1 and less than γ2, the level of secondary division is level II, that is, the original cell is evenly divided into 4 parts;

[0026] When γ is greater than or equal to γ3, the level of secondary division is level III, that is, the original cell is evenly divided into 9 parts; among which, 0<γ1<γ2<γ3<1;

[0027] The cells of different sizes obtained after the secondary division are divided into three types, including: type I cells, type II cells and type III cells; the coordinates of type I cells in the coordinate system are (i, j), where i = 1, 2, ..., n; j = 1, 2, ..., m; the coordinates of type II cells in the coordinate system are (i Ⅱa ,j Ⅱb ), where a=1,2, b=1,2; the coordinates of the type III cell in the coordinate system are (i Ⅲx ,j Ⅲy ), where x = 1, 2, 3, y = 1, 2, 3;

[0028] Step 3.4: Through the experimental method, the coordinates (i, j), (i Ⅱa ,j Ⅱb ) and (i Ⅲx ,j Ⅲy ) represents the output flow and output pressure represented by the center point of the three types of cells, and is used as the optimal speed under the working conditions represented by the entire cell, and is denoted as N r (i,j),N r (i Ⅱa ,j Ⅱb ) and N r (i Ⅲx ,j Ⅲy );

[0029] Step 3.5, according to the coordinates (i, j), (i Ⅱa ,j Ⅱb ) and (i Ⅲx ,j Ⅲy ) The actual output pressure P of any coordinate point (α, β) in the three types of units R (α) and the actual output flow Q R (β), calculate the displacement V of any coordinate point (α, β) according to formula (2) r (P R (α),Q R (β)):

[0030]

[0031] In formula (2): N rThe optimal speed of the three types of cells is uniformly represented; then the displacement corresponding to any coordinate point in the three types of cells is:

[0032] Type I cells:

[0033] Type II cells:

[0034] Class III cells:

[0035] Step 3.6: According to step 3.4 and step 3.5, the optimal speed and displacement of all types of cells in the plane coordinate system are obtained, thereby establishing an energy efficiency database.

[0036] The error allocation criterion defines the parameter E d It is calculated according to formula (6):

[0037]

[0038] In formula (3), A is the effective area of ​​the hydraulic cylinder, V min is the minimum adjustment amount of the variable pump displacement, N RE is the actual speed of the variable speed motor, and T0 is the standard evaluation parameter of the response time.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] 1. The present invention adopts a strategy of time-sharing control based on error distribution according to the different response speeds of the variable speed motor and the variable pump to the output flow in actual work. When the displacement following error is large, the displacement of the variable pump is adjusted. When the displacement following error is small, the speed of the variable speed motor is adjusted, thereby improving the response speed and position tracking accuracy of the system.

[0041] 2. The present invention determines the combination of the speed of the variable speed motor and the displacement of the variable pump with the highest energy efficiency by means of energy efficiency decoupling, and uses it as the initial operating parameters of the hydraulic drive system, so that the load power and the output power of the drive system are matched as much as possible, thereby reducing the energy consumption of the hydraulic system.

[0042] 3. The present invention focuses on analyzing working conditions with higher energy consumption based on the different energy consumption under different working conditions during the operation of the hydraulic system, thereby minimizing the number of experiments required to establish an energy efficiency database and ensuring the accuracy of energy efficiency decoupling. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a control flow chart of the system of the present invention;

[0044] Figure 2 It is a schematic diagram of the structure of the dual variable hydraulic system of the present invention;

[0045] Figure 3 It is a schematic diagram of the principle of establishing the energy efficiency decoupling database of the present invention.

[0046] Numbers in the figure: 1 variable speed motor, 2 variable pump, 3 overflow valve, 4 throttle valve, 5 three-position four-way solenoid valve, 6 hydraulic cylinder, 7 data acquisition card, 8 industrial computer, 9 data output card, 10 speed sensor, 11 flow sensor, 12 oil inlet pressure sensor, 13 oil return pressure sensor, 14 displacement sensor. DETAILED DESCRIPTION

[0047] The present invention is further described in detail with reference to the accompanying drawings and specific implementation processes.

[0048] like Figure 2 As shown, the dual variable hydraulic system of the present invention is mainly composed of a variable speed motor 1, a variable pump 2, a relief valve 3, a throttle valve 4, a three-position four-way solenoid valve 5, a hydraulic cylinder 6, a data acquisition card 7, an industrial computer 8, a data output card 9, a speed sensor 10, a flow sensor 11, an oil inlet pressure sensor 12, an oil return pressure sensor 13, and a displacement sensor 14. The data acquisition card 7 collects the detection signals of each sensor, the industrial computer 8 performs signal processing on the collected signals, and outputs control signals to the data output card 9 to control the speed of the variable speed motor 1, the displacement of the variable pump 2, and the three-position four-way solenoid valve 5 respectively.

[0049] like Figure 1 As shown in FIG. 1 , a high-precision position control method for a dual-variable hydraulic system based on energy efficiency decoupling, taking a fuzzy controller as an example, is performed in the following steps:

[0050] Step 1: After the dual variable hydraulic system is started, according to the actual working conditions of the system, the combination of the speed of the variable speed motor and the displacement of the variable pump that makes the hydraulic system most energy efficient is obtained through energy efficiency decoupling, and is used as the initial operating parameters of the dual variable hydraulic system. The initial operating parameters are the speed of the variable speed motor N0 and the displacement of the variable pump V0;

[0051] Among them, Figure 3 As shown in the figure, the specific process of energy efficiency decoupling is: first, an energy efficiency database is pre-established through experimental methods, and then during the operation of the hydraulic system, according to the actual output pressure and output flow of the variable pump, the corresponding combination of the speed of the variable speed motor and the displacement of the variable pump is obtained by querying the energy efficiency database.

[0052] In specific implementation, the process of establishing the energy efficiency database is as follows:

[0053] 1) According to the actual needs of the hydraulic system, the output pressure and output flow information of the variable pump of the dual variable hydraulic system during the entire operation process are collected by using sensors, and the output pressure P of the variable pump is represented by the horizontal axis, and the output flow Q of the variable pump is represented by the vertical axis, so as to establish a plane coordinate system related to the output pressure P and the output flow Q;

[0054] 2) The measured output pressure P is evenly divided into n ranges, which are recorded as P1, P2, ..., P i ,…,P n ; The output flow Q is evenly divided into m ranges, denoted as Q1, Q2, …, Q j ,…,Q m , thus dividing the coordinate system into n×m cells of equal size, where P i Indicates the i-th output pressure range, Q j represents the jth output flow range;

[0055] 3) Calculate the unit power ratio γ using formula (1):

[0056]

[0057] In formula (1): P c(i,j) is the system output power under the working condition represented by the cell with coordinates (i, j); P w It is the total power output of the system during a working cycle;

[0058] The larger the unit power ratio coefficient γ is, the greater the energy consumption of the working condition represented by the cell during the entire working cycle of the system, and the greater the impact on the energy efficiency of the system. Therefore, a more refined secondary division of the cell is required to ensure the accuracy of energy efficiency decoupling.

[0059] In this embodiment, according to the size of γ, the degree of secondary division is divided into three levels: when γ is less than γ1, the level of secondary division is level I, that is, the original cell is not divided; when γ is greater than or equal to γ1 and less than γ2, the level of secondary division is level II, that is, the original cell is evenly divided into 4 parts; when γ is greater than or equal to γ3, the level of secondary division is level III, that is, the original cell is evenly divided into 9 parts. Among them, 0<γ1<γ2<γ3<1, γ1, γ2 and γ3 are set according to the actual situation of the system.

[0060] After the secondary division, the cells of different sizes can be divided into three types: type I cells, type II cells and type III cells. The coordinates of type I cells in the coordinate system are (i, j), where i = 1, 2, ..., n; j = 1, 2, ..., m; the coordinates of type II cells in the coordinate system are (i Ⅱa ,j Ⅱb), where a=1,2, b=1,2; the coordinates of the type III cell in the coordinate system are (i Ⅲx ,j Ⅲy ), where x=1,2,3,y=1,2,3.

[0061] 4) The coordinates (i, j) and (i Ⅱa ,j Ⅱb ) and (i Ⅲx ,j Ⅲy The variable speed motor speed with the highest energy efficiency under the output flow and output pressure represented by the center point of the cell of ) is used as the optimal speed under the working condition represented by the entire cell, and is denoted as N r (i,j),N r (i Ⅱa ,j Ⅱb ) and N r (i Ⅲx ,j Ⅲy );

[0062] 5) According to the coordinates (i,j), (i Ⅱa ,j Ⅱb ) and (i Ⅲx ,j Ⅲy ) The actual output pressure P of any coordinate point (α, β) in the three types of units R (α) and the actual output flow Q R (β), and thus the displacement V of any coordinate point (α, β) is calculated according to formula (2): r (P R (α),Q R (β)):

[0063]

[0064] In formula (2): N r The optimal rotation speeds of the three types of cells are uniformly represented;

[0065] Then the displacement corresponding to any coordinate point in the three types of cells is:

[0066] Type I cells:

[0067] Type II cells:

[0068] Class III cells:

[0069] 6) According to step 4) and step 5), the optimal speed and displacement of all types of cells in the plane coordinate system are obtained, thereby establishing an energy efficiency database.

[0070] Step 2: Define variable k and initialize k=1;

[0071] Step 3: Use the pressure sensor to collect the load pressure signal of the hydraulic cylinder in the dual-variable hydraulic system, use the displacement sensor to collect the displacement signal of the hydraulic cylinder, and calculate the external load pressure P of the hydraulic cylinder in the kth stage. L,k and displacement following error E k ;

[0072] Step 4: According to the external load pressure P L,k and displacement following error E k After being processed by the fuzzy controller, the speed adjustment parameter ΔN of the variable speed motor in the kth stage is obtained. k Or the displacement adjustment parameter ΔV of the variable displacement pump k ;

[0073] The fuzzy controller controls the variable speed pump or the variable speed motor separately at different stages of displacement following error change according to the different response speeds of the variable speed motor and the variable speed pump to the output flow of the motor pump.

[0074] The adjustment parameter refers to the amount by which the speed of the variable speed motor or the displacement of the variable pump needs to be changed in order to eliminate the displacement following error;

[0075] The speed adjustment parameter and displacement adjustment parameter are obtained by the following control method:

[0076] S1. The displacement sensor measures the actual displacement of the piston rod of the hydraulic cylinder. The controller takes the difference between the required displacement and the actual displacement measured by the sensor as the displacement following error. The pressure measured by the oil inlet pressure sensor and the pressure measured by the oil return pressure sensor are taken as the external load pressure.

[0077] S2, fuzzy processing of external load pressure and displacement tracking error;

[0078] S3. Then, according to the predetermined fuzzy control processing rules, the fuzzy external load pressure and displacement following error are fuzzily adjusted dynamically to obtain the speed adjustment fuzzy control signal of the variable speed motor or the displacement adjustment fuzzy control signal of the variable pump.

[0079] The following is an example of the specific process of S3:

[0080] The external load pressure P L The value range is divided into seven range levels from P1 to P7, and the value of load pressure gradually increases from P1 to P7;

[0081] The displacement tracking error E is divided into seven ranges from E1 to E7. The displacement tracking error increases gradually from E1 to E7. d Set to E3;

[0082] The value range of the speed adjustment amount of the variable speed motor is divided into seven range levels of ΔN1-ΔN7, and the value range of the speed adjustment amount gradually increases from ΔN1 to ΔN7;

[0083] The displacement adjustment value range of the variable displacement pump is divided into seven range levels of ΔV1-ΔV7, and the displacement adjustment value range gradually increases from ΔV1 to ΔV7;

[0084] Then make the following judgment:

[0085] 1) If the external load pressure P currently measured in real time is L In the first pressure range class P1:

[0086] If the displacement following error E obtained by the current real-time measurement is within the range of the first error range level E1 to the third error range level E3, the speed adjustment parameter of the variable speed motor is set to the seventh speed adjustment level ΔN7;

[0087] If the displacement following error E is within the range of the fourth error range level E4 to the seventh error range level E7, the displacement adjustment parameter of the variable displacement pump is set to the seventh displacement adjustment level ΔV7;

[0088] 2) If the external load pressure P currently measured in real time is L In the second pressure range class P2:

[0089] If the displacement following error E obtained by the current real-time measurement is within the first error range level E1, the speed adjustment parameter of the variable speed motor is set to the sixth speed adjustment level ΔN6; if it is within the range from the second error range level E2 to the third error range level E3, the speed adjustment parameter of the variable speed motor is set to the seventh speed adjustment level ΔN7;

[0090] If the displacement following error E is within the range of the fourth error range level E4, the displacement adjustment parameter of the variable pump is set to the sixth displacement adjustment level ΔV6; if it is within the range of the fourth error range level E4 to the seventh error range level E7, the displacement adjustment parameter of the variable pump is set to the seventh displacement adjustment level ΔV7;

[0091] 3) If the external load pressure P currently measured in real time is L In the third pressure range class P3:

[0092] If the displacement following error E obtained by the current real-time measurement is within the range of the first error range level E1, the speed adjustment parameter of the variable speed motor is set to the fifth speed adjustment level ΔN5; if it is within the range of the second error range level E2, the speed adjustment parameter of the variable speed motor is set to the sixth speed adjustment level ΔN6; if it is within the range of the third error range level E3, the speed adjustment parameter of the variable speed motor is set to the seventh speed adjustment level ΔN7;

[0093] If the displacement following error E is within the range of the fourth error range level E4, the displacement adjustment parameter of the variable pump is set to the fifth displacement adjustment level ΔV5; if it is within the range of the fifth error range level E5, the displacement adjustment parameter of the variable pump is set to the sixth displacement adjustment level ΔV6; if it is within the range of the sixth error range level E6 to the seventh error range level E7, the displacement adjustment parameter of the variable pump is set to the seventh displacement adjustment level ΔV7;

[0094] 4) If the external load pressure P currently measured in real time is L In the fourth pressure range level P4:

[0095] If the displacement following error E currently measured in real time is within the range of the first error range level E1, the speed adjustment parameter of the variable speed motor is set to the fourth speed adjustment level ΔN4; if it is within the range of the second error range level E2, the speed adjustment parameter of the variable speed motor is set to the fifth speed adjustment level ΔN5; if it is within the range of the third error range level E3, the speed adjustment parameter of the variable speed motor is set to the sixth speed adjustment level ΔN6;

[0096] If the displacement following error E is within the range of the fourth error range level E4, the displacement adjustment setting parameter of the variable pump is set to the fourth displacement adjustment level ΔV4; if it is within the range of the fifth error range level E5, the displacement adjustment parameter of the variable pump is set to the fifth displacement adjustment level ΔV5; if it is within the range of the sixth error range level E6, the displacement adjustment parameter of the variable pump is set to the sixth displacement adjustment level ΔV6; if it is within the range of the seventh error range level E7, the displacement adjustment parameter of the variable pump is set to the seventh displacement adjustment level ΔV7;

[0097] 5) If the external load pressure P currently measured in real time is L In the fifth pressure range level P5:

[0098] If the displacement following error E obtained by the current real-time measurement is within the first error range level E1, the speed adjustment parameter of the variable speed motor is set to the third speed adjustment level ΔN3; if it is within the second error range level E2, the speed adjustment parameter of the variable speed motor is set to the fourth speed adjustment level ΔV4; if it is within the third error range level E3, the speed adjustment parameter of the variable speed motor is set to the fifth speed adjustment level ΔN5;

[0099] If the displacement following error E is within the range of the fourth error range level E4, the displacement adjustment parameter of the variable pump is set to the third displacement adjustment level ΔV3; if it is within the range of the fifth error range level E5, the displacement adjustment parameter of the variable pump is set to the fourth displacement adjustment level ΔV4; if it is within the range of the sixth error range level E6, the displacement adjustment parameter of the variable pump is set to the fifth displacement adjustment level ΔV5; if it is within the range of the seventh error range level E7, the displacement adjustment parameter of the variable pump is set to the sixth displacement adjustment level ΔV6;

[0100] 6) If the external load pressure P currently measured in real time is L In the sixth pressure range level P6:

[0101] If the displacement following error E currently measured in real time is within the range of the first error range level E1, the speed adjustment parameter of the variable speed motor is set to the second speed adjustment level ΔN2; if it is within the range of the second error range level E2, the speed adjustment parameter of the variable speed motor is set to the third speed adjustment level ΔN3; if it is within the range of the third error range level E3, the speed adjustment parameter of the variable speed motor is set to the fourth speed adjustment level ΔN4;

[0102] If the displacement following error E is within the range of the fourth error range level E4, the displacement adjustment parameter of the variable pump is set to the second displacement adjustment level ΔV2; if it is within the range of the fifth error range level E5, the displacement adjustment parameter of the variable pump is set to the third displacement adjustment level ΔV3; if it is within the range of the sixth error range level E6, the displacement adjustment parameter of the variable pump is set to the fourth displacement adjustment level ΔV4; if it is within the range of the seventh error range level E7, the displacement adjustment parameter of the variable pump is set to the fifth displacement adjustment level ΔV5;

[0103] 7) If the external load pressure P currently measured in real time is L In the seventh pressure range level P7:

[0104] If the displacement following error E currently measured in real time is within the range of the first error range level E1, the speed adjustment parameter of the variable speed motor is set to the first speed adjustment level ΔN1; if it is within the range of the second error range level E2, the speed adjustment parameter of the variable speed motor is set to the second speed adjustment level ΔN2; if it is within the range of the third error range level E3, the speed adjustment parameter of the variable speed motor is set to the third speed adjustment level ΔN3;

[0105] If the displacement following error E is within the range of the fourth error range level E4, the displacement adjustment parameter of the variable pump is set to the first displacement adjustment level ΔV1; if it is within the range of the fifth error range level E5, the displacement adjustment parameter of the variable pump is set to the second displacement adjustment level ΔV2; if it is within the range of the sixth error range level E6, the displacement adjustment parameter of the variable pump is set to the third displacement adjustment level ΔV3; if it is within the range of the seventh error range level E7, the displacement adjustment parameter of the variable pump is set to the fourth displacement adjustment level ΔV4;

[0106] The membership functions of the input variables and output variables of the fuzzy control are Gaussian distribution functions, and other calculations of the fuzzy control are calculated according to the conventional algorithms of the fuzzy control. The control rules of the fuzzy controller are shown in Table 1.

[0107] Table 1 Fuzzy control rules table

[0108]

[0109] Step 5: Adjust the parameter ΔN according to the speed of the variable speed motor k Or the displacement adjustment parameter ΔV of the variable displacement pump k , for the speed N of the variable speed motor in the k-1th stage k-1 Or the displacement V of the variable pump k-1 Adjust to get the speed N of the variable speed motor in the kth stage k Or the displacement V of the variable pump k , and used as the operating parameters of the k-th stage dual variable hydraulic system; where; N k =N k-1 +ΔN k , V k =V k-1 +ΔV k ;

[0110] Step 6: Calculate the error allocation standard definition parameter E using equation (3) d :

[0111]

[0112] In formula (3), A is the effective area of ​​the hydraulic cylinder, Vmin is the minimum adjustment amount of the variable pump displacement, N RE is the actual speed of the variable speed motor, T0 is the standard evaluation parameter of the response time, which can be obtained by experimental methods;

[0113] The response time standard evaluation parameter T0 is related to the response speed of the variable pump and the variable speed motor to the output flow of the motor pump. In order to measure the response speed of the variable pump and the variable speed motor to the output flow of the motor pump, the response time evaluation parameter T0 of the variable pump is proposed. v and the response time evaluation parameter T of the variable speed motor n , using equations (4) and (5) to calculate the response time evaluation parameter T of the variable pump v and the response time evaluation parameter T of the variable speed motor n :

[0114]

[0115]

[0116] In formula (4) and formula (5): V min is the minimum adjustment amount of the variable pump displacement, N min V is the minimum adjustment amount of the variable speed motor speed. RE is the actual displacement of the variable pump;

[0117] The present invention adopts T v As an evaluation parameter, when T v When T is greater than T0, the fuzzy controller adjusts the displacement of the variable pump; when T v When it is less than T0, the fuzzy controller adjusts the speed of the variable speed motor;

[0118] Due to T v It cannot be directly obtained through measurement, and the output flow error ΔQ of the motor pump is proportional to the displacement following error E, that is, ΔQ = A × E. Therefore, the mathematical relationship between the displacement following error E and the response time standard evaluation parameter T0 can be established, and the error distribution standard definition parameter E can be calculated. d , thereby controlling the variable speed motor or variable pump according to the change of displacement following error.

[0119] The experimental method to obtain T0 is as follows: first, combining the actual working speed of the hydraulic system, the minimum adjustment amount of the variable pump displacement and other factors, calculate T0 according to formula (2): v The value range of is denoted as [T va ,T vb ], then [T va ,T vb] is divided into r parts, and r-1 equal points are taken as T0 for experiment. The response speed and position tracking accuracy of the dual variable hydraulic system are used as evaluation criteria to determine the best value range [T vc ,T vd ]; Finally, in [T vc ,T vd ] The binary selection method is used to conduct experiments multiple times until the best point is found as T0.

[0120] Step 7: When the measured displacement following error E k Greater than E d When the displacement following error E is measured, adjust the displacement of the variable pump; k Less than E d When adjusting the speed of the variable speed motor;

[0121] Step 8: After assigning k+1 to k, return to step 3 and execute sequentially until the detected displacement following error is zero or the dual variable hydraulic system runs to the specified position, and the control ends.

Claims

1. A high-precision position control method for a dual-variable hydraulic system based on energy efficiency decoupling, characterized in that: The steps are as follows: Step 1: After the dual variable hydraulic system is started, according to the actual working conditions of the system, the combination of the speed of the variable speed motor and the displacement of the variable pump that makes the hydraulic system most energy efficient is obtained through energy efficiency decoupling, and is used as the initial operating parameters of the dual variable hydraulic system, the initial operating parameters being the speed of the variable speed motor N0 and the displacement of the variable pump V0; Step 2: Define variable k and initialize k=1; Step 3: Use a pressure sensor to collect the load pressure signal of the k-th stage hydraulic cylinder in the dual variable hydraulic system, and use a displacement sensor to collect the displacement signal of the k-th stage hydraulic cylinder, so as to calculate the external load pressure P of the k-th stage hydraulic cylinder. L,k and displacement following error E k ; Step 4: According to the external load pressure P L,k and displacement following error E k , get the speed adjustment parameter ΔN of the variable speed motor in the kth stage k Or the displacement adjustment parameter ΔV of the variable displacement pump k ; Step 5: Adjust the speed of the variable speed motor according to the parameter ΔN k Or the displacement adjustment parameter ΔV of the variable displacement pump k , for the speed N of the variable speed motor in the k-1th stage k-1 Or the displacement V of the variable pump k-1 Adjust to get the speed N of the variable speed motor in the kth stage k Or the displacement V of the variable pump k , and used as the kth order operating parameter of the dual variable hydraulic system; where: N k =N k-1 +ΔN k , V k =V k-1 +ΔV k ; Step 6: When the displacement follows the error E k Greater than the error distribution standard definition parameter E d When adjusting the displacement V of the variable pump k ; When the displacement follows the error E k Less than the error distribution standard definition parameter E d When adjusting the speed of the variable speed motor N k ; Step 7: Assign k+1 to k and return to step 3 to execute sequentially until the displacement follows the error E k Control ends when it reaches zero or the dual variable hydraulic system runs to the specified position.

2. The high-precision position control method according to claim 1, characterized in that: The process of energy efficiency decoupling is: first, an energy efficiency database is established through experimental methods, and then during the operation of the dual variable hydraulic system, according to the actual output pressure and output flow of the variable pump, the corresponding combination of the speed of the variable speed motor and the displacement of the variable pump is obtained by querying the energy efficiency database.

3. The high-precision position control method according to claim 2, characterized in that: The process of establishing the energy efficiency database includes: Step 3.1, according to the actual working requirements of the dual variable hydraulic system, use sensors to collect the output pressure and output flow information of the variable pump during the entire operation of the dual variable hydraulic system, and use the horizontal axis to represent the output pressure P of the variable pump and the vertical axis to represent the output flow Q of the variable pump, thereby establishing a plane coordinate system related to the output pressure P and the output flow Q; Step 3.2: Divide the measured output pressure P into n ranges, denoted as P1, P2, …, P i ,…,P n ; The output flow Q is evenly divided into m ranges, denoted as Q1, Q2, …, Q j ,…,Q m , thus dividing the plane coordinate system into n×m cells of the same size, and the coordinates of any cell are marked as (i, j), where P i Indicates the i-th output pressure range, Q j represents the jth output flow range; Step 3.3: Calculate the unit power ratio γ using formula (1): In formula (1): P c(i,j) is the system output power under the working condition represented by the cell with coordinates (i, j); P w It is the total power output of the system during a working cycle; According to the size of γ, the degree of secondary division is divided into three levels: When γ is less than γ1, the level of secondary division is level I, that is, the original cells are not divided; When γ is greater than or equal to γ1 and less than γ2, the level of secondary division is level II, that is, the original cell is evenly divided into 4 parts; When γ is greater than or equal to γ3, the level of secondary division is level III, that is, the original cell is evenly divided into 9 parts; among which, 0<γ1<γ2<γ3<1; The cells of different sizes obtained after the secondary division are divided into three types, including: type I cells, type II cells and type III cells; the coordinates of type I cells in the coordinate system are (i, j), where i = 1, 2, ..., n; j = 1, 2, ..., m; the coordinates of type II cells in the coordinate system are (i Ⅱa ,j Ⅱb ), where a=1,2, b=1,2; the coordinates of the type III cell in the coordinate system are (i Ⅲx ,j Ⅲy ), where x = 1, 2, 3, y = 1, 2, 3; Step 3.4: Through the experimental method, the coordinates (i, j), (i Ⅱa ,j Ⅱb ) and (i Ⅲx ,j Ⅲy ) represents the output flow and output pressure represented by the center point of the three types of cells, and is used as the optimal speed under the working conditions represented by the entire cell, and is denoted as N r (i,j),N r (i Ⅱa ,j Ⅱb ) and N r (i Ⅲx ,j Ⅲy ); Step 3.5, according to the coordinates (i, j), (i Ⅱa ,j Ⅱb ) and (i Ⅲx ,j Ⅲy ) The actual output pressure P of any coordinate point (α, β) in the three types of units R (α) and the actual output flow Q R (β), calculate the displacement V of any coordinate point (α, β) according to formula (2) r (P R (α),Q R (β)): In formula (2): N r The optimal speed of the three types of cells is uniformly represented; then the displacement corresponding to any coordinate point in the three types of cells is: Type I cells: Type II cells: Class III cells: Step 3.6: According to step 3.4 and step 3.5, the optimal speed and displacement of all types of cells in the plane coordinate system are obtained, thereby establishing an energy efficiency database.

4. The high-precision position control method according to claim 1, characterized in that: The error allocation criterion defines the parameter E d It is calculated according to formula (6): In formula (3), A is the effective area of ​​the hydraulic cylinder, V min is the minimum adjustment amount of the variable pump displacement, N RE is the actual speed of the variable speed motor, and T0 is the standard evaluation parameter of the response time.

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