A hydraulic press four-corner leveling system based on independent load ports and its control method

Abstract

The present invention discloses a four-corner leveling system of a hydraulic press based on independent load ports and a control method thereof. The four-corner leveling system mainly includes: a leveling cylinder, a displacement sensor, a relief valve, a pressure sensor, a high-frequency proportional valve, a hydraulic source, an oil tank and a controller. The control method of the present invention first collects displacement signals and pressure signals during the leveling process through each displacement sensor and a pressure sensor; adjusts the target speed of the flow controller according to the difference between the actual displacement of each leveling cylinder and the target displacement, and then processes the difference between the actual speed of each leveling cylinder and the target speed through the flow controller to output the control value of the flow valve, and compares and adjusts it with the control value of the diagonal leveling cylinder, and finally returns the final adjustment value to each flow controller. The control method provided by the present invention can quickly and accurately adjust the actual displacement of each hydraulic cylinder to keep synchronization with the target position when bearing an eccentric load, maintain the stable operation of the system, improve the processing accuracy of the hydraulic press, and has strong engineering practicability.

Description

Technical Field

[0001] The invention relates to the design and control of a hydraulic system, in particular to a high-speed hydraulic four-corner leveling system based on independent load ports and a control method thereof. Background Art

[0002] Complex curved stamping parts are widely used in key fields such as aerospace, automobile and transportation. The strength and precision of stamping parts are affected by the service performance of hydraulic forming equipment. The efficient and stable operation of hydraulic forming equipment is related to the final quality and forming performance of the formed parts. However, when pressing large material parts such as automobiles and aircraft, the uneven force on the movable beam is caused by the eccentric load characteristics, resulting in the position shift of the movable beam of the press, which seriously restricts the quality of product forming and even causes irreversible damage to the mold.

[0003] Research has shown that hydraulic four-corner leveling technology can improve the performance and reliability of hydraulic presses. However, as the working surface of large hydraulic presses becomes larger, the working speed becomes higher, and the precision requirements become higher, higher requirements are placed on the hydraulic four-corner leveling system. Therefore, it is particularly important to study a hydraulic four-corner leveling system with stable and reliable performance and its control method. Summary of the invention

[0004] The purpose of the present invention is to provide a high-speed hydraulic press four-corner leveling system based on independent load ports and a control method thereof, which can improve the working stability and reliability of the hydraulic press.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A four-corner leveling system of a hydraulic press based on independent load ports comprises a first leveling cylinder, a second leveling cylinder, a third leveling cylinder and a fourth leveling cylinder, wherein the first leveling cylinder is connected to a first displacement sensor, the second leveling cylinder is connected to a second displacement sensor, the third leveling cylinder is connected to a third displacement sensor, the fourth leveling cylinder is connected to a fourth displacement sensor, the first leveling cylinder is connected to a first overflow valve and a second overflow valve, the second leveling cylinder is connected to a third overflow valve and a fourth overflow valve, the third leveling cylinder is connected to a fifth overflow valve and a sixth overflow valve, the fourth leveling cylinder is connected to a seventh overflow valve and an eighth overflow valve, the first leveling cylinder is also provided with a first pressure sensor and a second pressure sensor, the second leveling cylinder is connected to a third overflow valve and a fourth overflow valve, the third leveling cylinder is connected to a fifth overflow valve and a sixth overflow valve, the fourth leveling cylinder is connected to a seventh overflow valve and an eighth overflow valve, the first leveling cylinder is also provided with a first pressure sensor and a second pressure sensor, the second leveling cylinder is connected to a third overflow valve and a fourth overflow valve, the first ... The leveling cylinder is connected to the third pressure sensor and the fourth pressure sensor, the third leveling cylinder is connected to the fifth pressure sensor and the sixth pressure sensor, the fourth leveling cylinder is connected to the seventh pressure sensor and the eighth pressure sensor, the first leveling cylinder is connected to the first flow control high-frequency response proportional valve and the first pressure control high-frequency response proportional valve, the second leveling cylinder is connected to the second flow control high-frequency response proportional valve and the second pressure control high-frequency response proportional valve, the third leveling cylinder is connected to the third flow control high-frequency response proportional valve and the third pressure control high-frequency response proportional valve, the fourth leveling cylinder is connected to the fourth flow control high-frequency response proportional valve and the fourth pressure control high-frequency response proportional valve, and the system also includes a ninth pressure sensor, a ninth overflow valve, an oil tank, a hydraulic source and a controller.

[0007] The present invention also has the following features:

[0008] The first displacement sensor, the second displacement sensor, the third displacement sensor and the fourth displacement sensor are installed inside the first leveling cylinder, the second leveling cylinder, the third leveling cylinder and the fourth leveling cylinder respectively.

[0009] The first displacement sensor, the second displacement sensor, the third displacement sensor and the fourth displacement sensor are used to collect displacement signals of the first leveling cylinder, the second leveling cylinder, the third leveling cylinder and the fourth leveling cylinder respectively and send them to the controller in real time.

[0010] The oil inlet P of the first flow control high-frequency response proportional valve, the first pressure control high-frequency response proportional valve, the second flow control high-frequency response proportional valve, the second pressure control high-frequency response proportional valve, the third flow control high-frequency response proportional valve, the third pressure control high-frequency response proportional valve, the fourth flow control high-frequency response proportional valve, and the fourth pressure control high-frequency response proportional valve are connected to the hydraulic source, and the oil return port T is connected to the oil tank. The working oil ports A of the first flow control high-frequency response proportional valve, the second flow control high-frequency response proportional valve, the third flow control high-frequency response proportional valve, and the fourth flow control high-frequency response proportional valve are respectively connected to the rodless chambers of the first leveling cylinder, the second leveling cylinder, the third leveling cylinder, and the fourth leveling cylinder; the working oil ports A of the first pressure control high-frequency response proportional valve, the second pressure control high-frequency response proportional valve, the third pressure control high-frequency response proportional valve, and the fourth pressure control high-frequency response proportional valve are It is also connected to the rod chambers of the first leveling cylinder, the second leveling cylinder, the third leveling cylinder and the fourth leveling cylinder. The controller sends flow control signals to the first flow control high-frequency response proportional valve, the second flow control high-frequency response proportional valve, the third flow control high-frequency response proportional valve and the fourth flow control high-frequency response proportional valve in real time, and sends pressure control signals to the first pressure control high-frequency response proportional valve, the second pressure control high-frequency response proportional valve, the third pressure control high-frequency response proportional valve and the fourth pressure control high-frequency response proportional valve.

[0011] The first relief valve, the third relief valve, the fifth relief valve, the seventh relief valve and the eighth relief valve are installed in the oil circuit connecting the rod chamber of the first leveling cylinder, the second leveling cylinder, the third leveling cylinder and the fourth leveling cylinder and the first flow control high-frequency response proportional valve, the second flow control high-frequency response proportional valve, the third flow control high-frequency response proportional valve and the fourth flow control high-frequency response proportional valve;

[0012] The second overflow valve, the fourth overflow valve are connected, the sixth overflow valve and the eighth overflow valve are connected to the rodless chamber installed in the first leveling cylinder, the second leveling cylinder, the third leveling cylinder and the fourth leveling cylinder and the first flow control high-frequency response proportional valve, the second flow control high-frequency response proportional valve, the third flow control high-frequency response proportional valve, and the fourth flow control high-frequency response proportional valve are connected in the oil circuit.

[0013] The first pressure sensor, the third pressure sensor, the fifth pressure sensor and the seventh pressure sensor are installed in the oil circuit connecting the rod chamber of the first leveling cylinder, the second leveling cylinder, the third leveling cylinder and the fourth leveling cylinder and the working oil port A of the first flow control high-frequency response proportional valve, the second flow control high-frequency response proportional valve, the third flow control high-frequency response proportional valve and the fourth flow control high-frequency response proportional valve;

[0014] The rodless chambers of the first leveling cylinder, the second leveling cylinder, the third leveling cylinder and the fourth leveling cylinder are respectively connected to the working oil ports A of the first control pressure high-frequency response proportional valve, the second control pressure high-frequency response proportional valve, the third control pressure high-frequency response proportional valve and the fourth control pressure high-frequency response proportional valve; the hydraulic source is connected to the oil inlet P of the first control pressure high-frequency response proportional valve, the second control pressure high-frequency response proportional valve, the third control pressure high-frequency response proportional valve and the fourth control pressure high-frequency response proportional valve.

[0015] The first leveling cylinder, the second leveling cylinder, the third leveling cylinder and the fourth leveling cylinder are vertically placed at the four corners of the bottom beam under the hydraulic press in a clockwise direction.

[0016] A control method for a four-corner leveling system of a hydraulic press based on independent load ports.

[0017] Input the target displacement and target pressure into the flow controller and pressure controller of the first leveling cylinder, the second leveling cylinder, the third leveling cylinder and the fourth leveling cylinder respectively, so that the flow controller performs displacement control on the first leveling cylinder, the second leveling cylinder, the third leveling cylinder and the fourth leveling cylinder, and the pressure controller performs pressure control on the first leveling cylinder, the second leveling cylinder, the third leveling cylinder and the fourth leveling cylinder;

[0018] Feeding back the displacement values ​​and pressure values ​​of the first leveling cylinder, the second leveling cylinder, the third leveling cylinder and the fourth leveling cylinder in the leveling cycle to the flow controller and the pressure controller thereof;

[0019] The flow controller and the pressure controller output the flow control quantity and the pressure control quantity respectively, and feed back each control quantity to the cross controller of the diagonally arranged leveling cylinders, so that the control quantities of the two diagonally arranged leveling cylinders are equal, and finally enter the next leveling cycle.

[0020] Step 1: Divide the leveling process into n intervals, that is, t0~t n Divided into t0, t1, …, t j , t j+1 ,…,t n At n+1 moments, the displacement sensor collects the displacement signal x during the leveling process. i (i=1,2,3,4), the pressure sensor collects pressure signals p1, p ai (i=1, 2, 3, 4) and p bi (i=1, 2, 3, 4), the controller outputs a control signal u to the high-frequency response proportional valve 1i (i=1, 2, 3, 4) and u 2i (i=1, 2, 3, 4);

[0021] Step 2: During the leveling process, the displacement signal x collected by the displacement sensor i , the pressure signals p1 and p collected by the pressure sensorai (i=1, 2, 3, 4) and p bi (i=1, 2, 3, 4) are uploaded to the controller in real time, and the displacement signal x collected by the displacement sensor is i and the target displacement value x of the leveling cylinder ref The displacement difference Δx is obtained by subtracting i , the hydraulic cylinder rod chamber pressure signal p bi With the target pressure value p ref The pressure difference Δp is obtained by subtracting bi ;

[0022] Step 3: Substitute the absolute value of the displacement difference |Δx i |Difference δ from the allowable displacement of the system x For comparison, if the absolute value of the displacement difference |Δx i The absolute value of | is greater than the allowable displacement difference δ x , then go to step 4, otherwise go to step 5;

[0023] At the same time, the absolute value of the pressure difference |Δp bi |Difference from system allowable pressure δ p For comparison, if the absolute value of the pressure difference |Δp bi The absolute value of | is greater than the allowable pressure difference δ p , then go to step 4, otherwise go to step 5;

[0024] Step 4: If the displacement difference Δx i Greater than 0, indicating the actual position x of the leveling cylinder i Lagging behind the target position x ref , then the displacement difference Δx i Input to the position controller, the position controller converts the displacement difference Δx i Derivative to get the target speed difference The target speed difference The speed controller converts the target speed difference With the target speed value v ref Add together to increase the target speed to Then the target speed With actual speed (A ai is the rodless chamber area of ​​the hydraulic cylinder, K ai is the flow coefficient of the rodless chamber of the hydraulic cylinder, ρ is the density of the hydraulic oil, P r is the tank pressure) and subtract it to get the speed difference Δv i , and then the speed difference Δv i After being processed by the PID algorithm in the speed controller, the output value u of the flow control valve opening is 1i, and compare it with the adjustment value of the diagonal leveling cylinder of the leveling cylinder, average the absolute values ​​of the two values ​​and add their respective signs, and then return the average value to each controller; if the displacement difference Δx i Less than 0, indicating the actual position x of the leveling cylinder i Ahead of target position x ref , then the displacement difference Δx i Input to the position controller, the position controller converts the displacement difference Δx i Derivative to get the target speed difference The target speed difference The speed controller converts the target speed difference With the target speed value v ref Add together to reduce the target speed to Then the target speed With actual speed (A ai is the rodless chamber area of ​​the hydraulic cylinder, K ai is the flow coefficient of the rodless chamber of the hydraulic cylinder, ρ is the density of the hydraulic oil, P r is the tank pressure) and the speed difference Δv is obtained by subtracting i , and then the speed difference Δv i After being processed by the PID algorithm in the speed controller, the output value u of the flow control valve opening is 1i , and compare it with the adjustment value of the diagonal leveling cylinder of the leveling cylinder, average the absolute values ​​of the two values ​​and add their respective signs, and then return the average value to each controller;

[0025] At the same time, if the pressure difference Δp bi If it is greater than 0, it means that the actual pressure p of the low-pressure chamber of the leveling cylinder bi Less than the target pressure p ref , then the pressure difference Δp bi After being processed by the PID algorithm in the pressure controller, the output value of the valve opening of the pressure control valve is compared with the adjustment value of the diagonal cylinder of the leveling cylinder. The absolute values ​​of the two values ​​are averaged and their respective signs are added, and then the average value is returned to each controller; if the pressure difference Δp bi If it is less than 0, it means that the actual pressure p of the low-pressure chamber of the leveling cylinder bi Greater than the target pressure p ref , then the pressure difference Δp bi After being processed by the PID algorithm in the pressure controller, the output value of the valve opening size of the pressure control valve is compared with the added value of the diagonal cylinder of the leveling cylinder, and compared with the adjustment value of the diagonal leveling cylinder of the leveling cylinder. The absolute values ​​of the two values ​​are averaged and their respective signs are added, and then the average value is returned to each controller;

[0026] Step 5: Determine whether the time does not exceed the specified tn If the judgment is yes, then j+1 is made to enter the next leveling cycle and return to step 1. If the judgment is no, the leveling is ended.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: adjusting the control signal output of the flow controller of each leveling cylinder according to the difference between the actual displacement of each leveling cylinder and the target displacement, adjusting the control signal output of the pressure controller of each leveling cylinder according to the difference between the actual pressure of each leveling cylinder and the target pressure, and then comparing and adjusting the adjustment control signal with the adjustment control signal of the diagonal leveling cylinder, so as to more accurately and quickly control the actual displacement of each hydraulic cylinder to keep synchronization with the target position when bearing an eccentric load. The control method provided by the present invention can quickly and accurately maintain the horizontal accuracy of the slider, maintain the stable operation of the system, improve the processing accuracy of the hydraulic machine, and has strong engineering practicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is the principle diagram of the four-corner leveling hydraulic system of the present invention;

[0029] Figure 2 It is the distribution diagram of the leveling cylinder of the present invention;

[0030] Figure 3 is a diagonal cross control strategy diagram of the present invention;

[0031] Figure 4 It is a control flow chart of the present invention. DETAILED DESCRIPTION

[0032] Combination Figures 1 to 4 The four-corner leveling system of a high-speed hydraulic press based on independent load ports and its control method of the present invention are further described as follows:

[0033] A four-corner leveling system of a hydraulic press based on independent load ports includes a first leveling cylinder 100, a second leveling cylinder 200, a third leveling cylinder 300 and a fourth leveling cylinder 400, wherein the first leveling cylinder 100 is connected to a first displacement sensor 110, the second leveling cylinder 200 is connected to a second displacement sensor 210, the third leveling cylinder 300 is connected to a third displacement sensor 310, the fourth leveling cylinder 400 is connected to a fourth displacement sensor 410, and .... The first leveling cylinder 100 is connected to the first overflow valve 120 and the second overflow valve 130, the second leveling cylinder 200 is connected to the third overflow valve 220 and the fourth overflow valve 230, the third leveling cylinder 300 is connected to the fifth overflow valve 320 and the sixth overflow valve 330, the fourth leveling cylinder 400 is connected to the seventh overflow valve 420 and the eighth overflow valve 430, the first leveling cylinder 100 is also provided with a first pressure sensor 140 and a second pressure sensor 150, the second leveling cylinder 200 is connected to the third pressure sensor 240 and the fourth pressure sensor 250, the third leveling cylinder 300 is connected to the fifth pressure sensor 340 and the sixth pressure sensor 350, the fourth leveling cylinder 400 is connected to the seventh pressure sensor 140 and the eighth pressure sensor 150, The sensor 440 is connected to the eighth pressure sensor 450, the first leveling cylinder 100 is connected to the first flow control high-frequency response proportional valve 160 and the first pressure control high-frequency response proportional valve 170, the second leveling cylinder 200 is connected to the second flow control high-frequency response proportional valve 260 and the second pressure control high-frequency response proportional valve 270, the third leveling cylinder 300 is connected to the third flow control high-frequency response proportional valve 360 ​​and the third pressure control high-frequency response proportional valve 370, the fourth leveling cylinder 400 is connected to the fourth flow control high-frequency response proportional valve 460 and the fourth pressure control high-frequency response proportional valve 470, and the system also includes a ninth pressure sensor 510, a ninth overflow valve 520, an oil tank 530, a hydraulic source 540 and a controller 550.

[0034] The first displacement sensor 110 , the second displacement sensor 210 , the third displacement sensor 310 , and the fourth displacement sensor 410 are installed inside the first leveling cylinder 100 , the second leveling cylinder 200 , the third leveling cylinder 300 , and the fourth leveling cylinder 400 , respectively.

[0035] The first displacement sensor 110 , the second displacement sensor 210 , the third displacement sensor 310 and the fourth displacement sensor 410 are used to collect displacement signals of the first leveling cylinder 100 , the second leveling cylinder 200 , the third leveling cylinder 300 and the fourth leveling cylinder 400 respectively and send them to the controller 550 in real time.

[0036] The oil inlet P of the first flow control high-frequency response proportional valve 160 and the first pressure control high-frequency response proportional valve 170 are connected, the second flow control high-frequency response proportional valve 260, the second pressure control high-frequency response proportional valve 270, the third flow control high-frequency response proportional valve 360, the third pressure control high-frequency response proportional valve 370, the fourth flow control high-frequency response proportional valve 460 and the fourth pressure control high-frequency response proportional valve 470 are connected to the hydraulic source 540, and the oil return port T is connected to the oil tank 530. The working oil ports A of the first flow control high-frequency response proportional valve 160, the second flow control high-frequency response proportional valve 260, the third flow control high-frequency response proportional valve 360 ​​and the fourth flow control high-frequency response proportional valve 460 are respectively connected to the rodless chambers of the first leveling cylinder 100, the second leveling cylinder 200, the third leveling cylinder 300 and the fourth leveling cylinder 400;

[0037] The working oil ports A of the first pressure control high-frequency response proportional valve 170, the second pressure control high-frequency response proportional valve 270, the third pressure control high-frequency response proportional valve 370 and the fourth pressure control high-frequency response proportional valve 470 are also connected to the rod chambers of the first leveling cylinder 100, the second leveling cylinder 200, the third leveling cylinder 300 and the fourth leveling cylinder 400. The controller 550 sends flow control signals to the first flow control high-frequency response proportional valve 160, the second flow control high-frequency response proportional valve 260, the third flow control high-frequency response proportional valve 360 ​​and the fourth flow control high-frequency response proportional valve 460 in real time, and sends pressure control signals to the first pressure control high-frequency response proportional valve 170, the second pressure control high-frequency response proportional valve 270, the third pressure control high-frequency response proportional valve 370 and the fourth pressure control high-frequency response proportional valve 470.

[0038] The first relief valve 120, the third relief valve 220, the fifth relief valve 320, the seventh relief valve 420 and the eighth relief valve 430 are installed in the oil circuit connecting the rod chamber of the first leveling cylinder 100, the second leveling cylinder 200, the third leveling cylinder 300 and the fourth leveling cylinder 400 with the first flow control high-frequency response proportional valve 160, the second flow control high-frequency response proportional valve 260, the third flow control high-frequency response proportional valve 360 ​​and the fourth flow control high-frequency response proportional valve 460;

[0039] The second overflow valve 130 and the fourth overflow valve 230 are connected, the sixth overflow valve 330 and the eighth overflow valve 430 are connected to the rodless chamber installed in the first leveling cylinder 100, the second leveling cylinder 200, the third leveling cylinder 300 and the fourth leveling cylinder 400, and the first flow control high-frequency response proportional valve 160, the second flow control high-frequency response proportional valve 260, the third flow control high-frequency response proportional valve 360, and the fourth flow control high-frequency response proportional valve 460 are connected in the oil circuit.

[0040] The first pressure sensor 140, the third pressure sensor 240, the fifth pressure sensor 340 and the seventh pressure sensor 440 are installed in the oil circuit connecting the rod chamber of the first leveling cylinder 100, the second leveling cylinder 200, the third leveling cylinder 300 and the fourth leveling cylinder 400 and the working oil port A of the first flow control high-frequency response proportional valve 160, the second flow control high-frequency response proportional valve 260, the third flow control high-frequency response proportional valve 360 ​​and the fourth flow control high-frequency response proportional valve 460;

[0041] The rodless chambers of the first leveling cylinder 100, the second leveling cylinder 200, the third leveling cylinder 300 and the fourth leveling cylinder 400 are respectively connected to the working oil ports A of the first control pressure high-response proportional valve 170, the second control pressure high-response proportional valve 270, the third control pressure high-response proportional valve 370 and the fourth control pressure high-response proportional valve 470; the hydraulic source 540 is connected to the oil inlet P of the first control pressure high-response proportional valve 170, the second control pressure high-response proportional valve 270, the third control pressure high-response proportional valve 370 and the fourth control pressure high-response proportional valve 470.

[0042] The first leveling cylinder 100 , the second leveling cylinder 200 , the third leveling cylinder 300 and the fourth leveling cylinder 400 are vertically placed at the four corners of the bottom beam of the hydraulic press in a clockwise direction.

[0043] A control method for a four-corner leveling system of a hydraulic press based on independent load ports.

[0044] The target displacement and the target pressure are respectively input into the flow controller and the pressure controller of the first leveling cylinder 100, the second leveling cylinder 200, the third leveling cylinder 300 and the fourth leveling cylinder 400, so that the flow controller performs displacement control on the first leveling cylinder 100, the second leveling cylinder 200, the third leveling cylinder 300 and the fourth leveling cylinder 400, and the pressure controller performs pressure control on the first leveling cylinder 100, the second leveling cylinder 200, the third leveling cylinder 300 and the fourth leveling cylinder 400;

[0045] Feedback the displacement values ​​and pressure values ​​of the first leveling cylinder 100, the second leveling cylinder 200, the third leveling cylinder 300 and the fourth leveling cylinder 400 in the leveling cycle to their flow controllers and pressure controllers;

[0046] The flow controller and the pressure controller output the flow control quantity and the pressure control quantity respectively, and feed back each control quantity to the cross controller of the diagonally arranged leveling cylinders, so that the control quantities of the two diagonally arranged leveling cylinders are equal, and finally enter the next leveling cycle.

[0047] The control method flow of the hydraulic press four-corner leveling system based on independent load ports also includes the following steps:

[0048] Step 1: Divide the leveling process into n intervals, that is, t0~t n Divided into t0, t1, ..., t j , t j+1 , ..., t n At n+1 moments, the displacement sensor collects the displacement signal x during the leveling process. i (i=1,2,3,4), the pressure sensor collects pressure signals p1, p ai (i=1, 2, 3, 4) and p bi (i=1, 2, 3, 4), the controller outputs a control signal u to the high-frequency response proportional valve 1i (i=1, 2, 3, 4) and u 2i (i=1, 2, 3, 4);

[0049] Step 2: During the leveling process, the displacement signal x collected by the displacement sensor i , the pressure signals p1 and p collected by the pressure sensor ai (i=1, 2, 3, 4) and p bi (i=1, 2, 3, 4) are uploaded to the controller in real time, and the displacement signal x collected by the displacement sensor is i and the target displacement value x of the leveling cylinder ref The displacement difference Δx is obtained by subtracting i =x ref -x i , the hydraulic cylinder rod chamber pressure signal p bi With the target pressure value p ref The pressure difference Δp is obtained by subtracting bi =p ref -p bi ;

[0050] Step 3: Substitute the absolute value of the displacement difference |Δx i |Difference δ from the allowable displacement of the system x For comparison, if the absolute value of the displacement difference |Δx i The absolute value of | is greater than the allowable displacement difference δ x , then go to step 4, otherwise go to step 5;

[0051] At the same time, the absolute value of the pressure difference |Δp bi |Difference from system allowable pressure δ p For comparison, if the absolute value of the pressure difference |Δp bi The absolute value of | is greater than the allowable pressure difference δ p , then go to step 4, otherwise go to step 5;

[0052] Step 4: If the displacement difference Δx i Greater than 0, indicating the actual position x of the leveling cylinder iLagging behind the target position x ref , then the displacement difference Δx i Input to the position controller, the position controller converts the displacement difference Δx i Derivative to get the target speed difference The target speed difference The speed controller converts the target speed difference With the target speed value v ref Add together to increase the target speed to Then the target speed With actual speed (A ai is the rodless chamber area of ​​the hydraulic cylinder, K ai is the flow coefficient of the rodless chamber of the hydraulic cylinder, ρ is the density of the hydraulic oil, P r is the tank pressure) and the speed difference Δv is obtained by subtracting i , and then the speed difference Δv i After being processed by the PID algorithm in the speed controller, the output value u of the flow control valve opening is 1i , and compare it with the adjustment value of the diagonal leveling cylinder of the leveling cylinder, average the absolute values ​​of the two values ​​and add their respective signs, and then return the average value to each controller; if the displacement difference Δx i Less than 0, indicating the actual position x of the leveling cylinder i Ahead of target position x ref , then the displacement difference Δx i Input to the position controller, the position controller converts the displacement difference Δx i Derivative to get the target speed difference The target speed difference The speed controller converts the target speed difference With the target speed value v ref Add together to reduce the target speed to Then the target speed With actual speed (A ai is the rodless chamber area of ​​the hydraulic cylinder, K ai is the flow coefficient of the rodless chamber of the hydraulic cylinder, ρ is the density of the hydraulic oil, P r is the tank pressure) and the speed difference Δv is obtained by subtracting i , and then the speed difference Δv i After being processed by the PID algorithm in the speed controller, the output value u of the flow control valve opening is 1i , and compare it with the adjustment value of the diagonal leveling cylinder of the leveling cylinder, average the absolute values ​​of the two values ​​and add their respective signs, and then return the average value to each controller;

[0053] At the same time, if the pressure difference Δp biIf it is greater than 0, it means that the actual pressure p of the low-pressure chamber of the leveling cylinder bi Less than the target pressure p ref , then the pressure difference Δp bi After being processed by the PID algorithm in the pressure controller, the output value of the valve opening of the pressure control valve is compared with the adjustment value of the diagonal cylinder of the leveling cylinder. The absolute values ​​of the two values ​​are averaged and their respective signs are added, and then the average value is returned to each controller; if the pressure difference Δp bi If it is less than 0, it means that the actual pressure p of the low-pressure chamber of the leveling cylinder bi Greater than the target pressure p ref , then the pressure difference Δp bi After being processed by the PID algorithm in the pressure controller, the output value of the valve opening size of the pressure control valve is compared with the added value of the diagonal cylinder of the leveling cylinder, and compared with the adjustment value of the diagonal leveling cylinder of the leveling cylinder. The absolute values ​​of the two values ​​are averaged and their respective signs are added, and then the average value is returned to each controller;

[0054] Step 5: Determine whether the time does not exceed the specified t n If the judgment is yes, then j+1 is made to enter the next leveling cycle and return to step 1. If the judgment is no, the leveling is ended.

[0055] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0056] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A control method for a four-corner leveling system of a hydraulic press based on independent load ports, characterized in that: Inputting the target displacement and the target pressure into the flow controller and the pressure controller of the first leveling cylinder (100), the second leveling cylinder (200), the third leveling cylinder (300) and the fourth leveling cylinder (400) respectively, so that the flow controller performs displacement control on the first leveling cylinder (100), the second leveling cylinder (200), the third leveling cylinder (300) and the fourth leveling cylinder (400), and the pressure controller performs pressure control on the first leveling cylinder (100), the second leveling cylinder (200), the third leveling cylinder (300) and the fourth leveling cylinder (400); Feeding back the displacement values ​​and pressure values ​​of the first leveling cylinder (100), the second leveling cylinder (200), the third leveling cylinder (300) and the fourth leveling cylinder (400) within the leveling cycle to their flow controllers and pressure controllers; The flow controller and the pressure controller output the flow control amount and the pressure control amount respectively, and feed back the control amounts to the cross controllers of the diagonally arranged leveling cylinders, so that the control amounts of the two diagonally arranged leveling cylinders are equal, and finally enter the next leveling cycle; The control method of the hydraulic press four-corner leveling system based on independent load ports comprises the following steps: Step 1: Divide the leveling process into n interval, about to Divide into common n +1 moment, during the leveling process, the displacement sensor collects the displacement signal , the pressure sensor collects the pressure signal , and , the controller outputs a control signal to the high-frequency response proportional valve and ; Step 2: During the leveling process, the displacement signal collected by the displacement sensor , pressure signal collected by pressure sensor , and Upload the displacement signal collected by the displacement sensor to the controller in real time Target displacement value of leveling cylinder The displacement difference is obtained by subtracting , the hydraulic cylinder has a rod chamber pressure signal With target pressure value Make a difference to get the pressure difference ; Step 3: The absolute value of the displacement difference Difference from system allowable displacement For comparison, if the absolute value of the displacement difference The absolute value of the displacement difference is greater than the allowable displacement difference , then go to step 4, otherwise go to step 5; At the same time, the absolute value of the pressure difference Allowable pressure difference with the system For comparison, if the absolute value of the pressure difference The absolute value is greater than the allowable pressure difference , then go to step 4, otherwise go to step 5; Step 4: If the displacement difference Greater than 0, indicating the actual position of the leveling cylinder Lagging behind target position , then increase the opening of the flow control valve, the increase is ,in is the rodless chamber area of ​​the hydraulic cylinder, is the flow coefficient of the rodless chamber of the hydraulic cylinder, is the hydraulic oil density, and is compared with the reduced value of the diagonal leveling cylinder of the leveling cylinder, the absolute values ​​of the two values ​​are averaged, and then the average value is returned to each controller; if the displacement difference Less than 0, indicating the actual position of the leveling cylinder Ahead of target position , then reduce the flow control valve opening size, the reduction value is ,in is the rodless chamber area of ​​the hydraulic cylinder, is the flow coefficient of the rodless chamber of the hydraulic cylinder, is the density of the hydraulic oil, and is compared with the increase value of the diagonal leveling cylinder of the leveling cylinder, the absolute values ​​of the two values ​​are averaged, and then the average value is returned to each controller; At the same time, if the pressure difference Greater than 0, indicating the actual pressure of the low-pressure chamber of the leveling cylinder Less than target pressure , then increase the opening of the pressure control valve, and its value increases to , and compare it with the decrease value of the diagonal cylinder of the leveling cylinder, and compare it with the increase value of the diagonal leveling cylinder of the leveling cylinder, average the absolute values ​​of the two values, and then return the average value to each controller; if the pressure difference If it is less than 0, it means the actual pressure of the low-pressure chamber of the leveling cylinder Greater than target pressure , then reduce the flow control valve opening size, its value is reduced to , and compare it with the increase value of the diagonal cylinder of the leveling cylinder, and compare it with the increase value of the diagonal leveling cylinder of the leveling cylinder, average the absolute values ​​of the two values, and then return the average value to each controller; Step 5: Determine whether the time does not exceed the specified time If the judgment is yes, then j +1, enter the next leveling cycle and return to step 1. If the judgment is no, the leveling is ended.

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