Double-oil-cylinder loading hydraulic control system and method based on proportional control

Abstract

The invention relates to a double-oil-cylinder loading hydraulic control system and method based on proportional control, the control system comprises a double-oil-cylinder loading structure and a hydraulic system for controlling double-oil-cylinder loading, and the double-oil-cylinder loading structure comprises two loading oil cylinders connected with a loading tool; a first force sensor and a second force sensor are arranged between piston rods of the two loading oil cylinders and the loading tool; the hydraulic system is a first hydraulic system and comprises a synchronous element, a three-position four-way electromagnetic reversing valve, a motor pump and an electric proportional overflow valve, or a first electric proportional pressure reducing valve and a second electric proportional pressure reducing valve are added on the basis to form a second hydraulic system. According to the control method, the control system is adopted, and the problems that under the equal loading force, the pressure of a single-oil-cylinder loading hydraulic system is large, the oil cylinder is large, and the requirement for hydraulic components is high are effectively solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydraulic control, and particularly relates to a hydraulic control system and method for double-cylinder loading based on proportional control. Background Art

[0002] Currently, the common hydraulic control technologies mainly include mechanical control, proportional control, and servo control. Among them, the mechanical control technology is the most widely used but has a low control accuracy. The servo control technology has a high control accuracy, but has high requirements for the precision of hydraulic components, high requirements for the cleanliness of hydraulic oil, and high costs, which severely limits the use of the servo control technology. Compared with these two hydraulic control technologies, the proportional control technology can just overcome the above disadvantages, so the proportional control technology is the most widely used in the control of hydraulic systems.

[0003] The cylinder loading method currently has the characteristic of high usage frequency in various test benches, such as the strength detection test of agricultural machinery parts, the structural mechanics test bench of parts, the strength detection test of wind power bearings, presses, etc. These test benches usually have the characteristic of high loading force, and their loading force is usually as high as hundreds of kN, thousands of kN, and some even as high as tens of thousands of kN. For such a large loading force, if a single cylinder is used to provide it, the cylinder has a large external dimension and the hydraulic system pressure is high, which will bring great difficulties to the selection of hydraulic system components and the manufacturing of the cylinder.

[0004] Therefore, in view of the problems existing in the existing single-cylinder loading, it is completely necessary to provide a hydraulic control system and method for double-cylinder loading based on proportional control. Summary of the Invention

[0005] The purpose of the present invention is to provide a hydraulic control system and method for double-cylinder loading based on proportional control, which solves the problems existing in the single-cylinder loading in the prior art and has the characteristics of high control accuracy and easy operation.

[0006] To achieve the above purpose, the first technical solution adopted by the present invention is: a hydraulic control system for double-cylinder loading based on proportional control, including a double-cylinder loading structure and a hydraulic system for controlling the double-cylinder loading. The double-cylinder loading structure includes two loading cylinders connected to a loading tooling. Force sensors, namely a first force sensor and a second force sensor, are arranged between the piston rods of the two loading cylinders and the loading tooling; The hydraulic system is the first hydraulic system, which includes a synchronization element, a three-position four-way electromagnetic directional control valve, a motor pump, and an electro-hydraulic proportional relief valve. The motor pump is connected to the P port on the three-position four-way electromagnetic directional control valve through an oil circuit. The inlet port of the electro-hydraulic proportional relief valve is connected to the P port of the three-position four-way electromagnetic directional control valve. The outlet port of the electro-hydraulic proportional relief valve is connected to the fuel tank. The A port on the three-position four-way electromagnetic directional control valve is connected to the inlet port of the synchronization element. The two outlet ports of the synchronization element are respectively connected to the rodless cavity oil ports of the two loading cylinders. The rodless cavity oil ports of the two loading cylinders are connected to the B port of the three-position four-way electromagnetic directional control valve. The T port of the three-position four-way electromagnetic directional control valve is connected to the fuel tank.

[0007] The second technical solution proposed by the present invention is: replacing the first hydraulic system with a second hydraulic system. The second hydraulic system includes a synchronization element, a three-position four-way electromagnetic directional control valve, a motor pump, an electro-hydraulic proportional relief valve, a first electro-hydraulic proportional reducing valve, and a second electro-hydraulic proportional reducing valve. The motor pump is connected to the P port on the three-position four-way electromagnetic directional control valve through an oil circuit. The inlet port of the electro-hydraulic proportional relief valve is connected to the P port of the three-position four-way electromagnetic directional control valve. The outlet port of the electro-hydraulic proportional relief valve is connected to the fuel tank. The A port on the three-position four-way electromagnetic directional control valve is connected to the inlet port of the synchronization element. The two outlet ports of the synchronization element are respectively connected to the rodless cavity oil ports of the two loading cylinders through the first electro-hydraulic proportional reducing valve and the second electro-hydraulic proportional reducing valve. The rodless cavity oil ports of the two loading cylinders are connected to the B port of the three-position four-way electromagnetic directional control valve. The T port of the three-position four-way electromagnetic directional control valve is connected to the fuel tank.

[0008] In the above two solutions, the loading tooling is a loading beam or a loading plate.

[0009] The third technical solution proposed by the present invention is: on the basis of the above two solutions, a displacement sensor is provided on each loading cylinder. The displacement sensor is fixed at the tail of the loading cylinder and is used to measure the real-time displacement of the piston rod of the loading cylinder.

[0010] Furthermore, the measuring component of the displacement sensor is installed inside the piston rod of the loading cylinder and moves synchronously with the piston rod.

[0011] The present invention also proposes a fourth technical solution, a proportional control-based dual-cylinder loading hydraulic control method. This method uses the dual-cylinder loading hydraulic control system described in the first technical solution and uses the measured value of the force sensor as the feedback signal of the dual-cylinder loading hydraulic control system. This method includes the following steps: (1) Determine the total loading force according to the test object of the dual-cylinder loading hydraulic control system. (2) Calculate the pressure P required for the first hydraulic system according to the total loading force and the diameter of the rodless cavity of the loading cylinder. (3) Automatically adjust the voltage of the proportional relief valve according to the calculated pressure P, and provide pressure for the loading cylinder through the first hydraulic system. (4) The three-position four-way electromagnetic directional valve in the first hydraulic system is energized to supply oil to the rodless cavity of the loading cylinder, thereby controlling the slow extension of the piston rod of the loading cylinder; (5) When the piston rod of the loading cylinder extends, it drives the loading tooling to move slowly until the loading tooling contacts the test object; (6) After the loading tooling contacts the test object, under the action relationship of action and reaction forces, the pressure of the first hydraulic system begins to increase, the piston rod continues to extend, and the system pressure continues to increase until it reaches the pressure set by the proportional relief valve; (7) The dual-cylinder loading hydraulic control system continuously calculates the sum of the measured values of the first force sensor and the second force sensor and compares it with the total loading force. If the sum of the measured values of the two force sensors is lower than the total loading force, the voltage of the proportional relief valve is continuously increased until the sum of the measured values of the two force sensors is equal to the total loading force; (8) After the loading force applied by the first hydraulic system reaches the requirement, the test starts, and the test time depends on the test object.

[0012] The present invention further proposes a fifth technical solution, a proportional control-based dual-cylinder loading hydraulic control method, which adopts the dual-cylinder loading hydraulic control system described in the second technical solution and uses the measured value of the force sensor as the feedback signal of the dual-cylinder loading hydraulic control system; the method includes the following steps: (1) Determine the total loading force according to the test object of the dual-cylinder loading hydraulic control system; (2) Calculate the pressure P required for the second hydraulic system according to the total loading force and the diameter of the rodless cavity of the loading cylinder; (3) Automatically adjust the voltage of the proportional relief valve according to the calculated pressure P, and provide pressure for the loading cylinder through the second hydraulic system; (4) The three-position four-way electromagnetic directional valve in the second hydraulic system is energized to supply oil to the rodless cavity of the loading cylinder, thereby controlling the slow extension of the piston rod of the loading cylinder; (5) When the piston rod of the loading cylinder extends, it drives the loading tooling to move slowly until the loading tooling contacts the test object; (6) After the loading tooling contacts the test object, under the action relationship of action and reaction forces, the pressure of the second hydraulic system begins to increase, the piston rod continues to extend, and the system pressure continues to increase until it reaches the pressure set by the proportional relief valve; (7) The double-cylinder loading hydraulic control system calculates the sum of the measured values of the first force sensor and the second force sensor in real time, and compares the difference between the measured values of the first force sensor and the second force sensor; if the deviation between the measured values of the first force sensor and the second force sensor is greater than the set value, the double-cylinder loading hydraulic control system adjusts the input voltages of the first electro-hydraulic proportional relief valve and the second electro-hydraulic proportional relief valve until the deviation between the measured values of the first force sensor and the second force sensor is less than the set value; meanwhile, the double-cylinder loading hydraulic control system compares the sum of the measured values of the first force sensor and the second force sensor with the total loading force. If the sum of the measured values of the two force sensors is lower than the total loading force, the voltage of the proportional overflow valve is continuously increased until the sum of the measured values of the two force sensors is equal to the total loading force. (8) After the loading force applied by the second hydraulic system reaches the requirement, the test starts, and the test time depends on the test object.

[0013] Further, the set value is 2%.

[0014] The present invention further proposes a sixth technical solution, a proportional control-based double-cylinder loading hydraulic control method, which uses the double-cylinder loading hydraulic control system described in the third technical solution and uses the measured value of the displacement sensor as the feedback signal of the double-cylinder loading hydraulic control system; the method includes the following steps: (1) Determine the total loading force according to the test object of the double-cylinder loading hydraulic control system. (2) Calculate the pressure P required for the hydraulic system according to the total loading force and the diameter of the rodless cavity of the loading cylinder. (3) Automatically adjust the voltage of the proportional overflow valve according to the calculated pressure P, and provide pressure for the loading cylinder through the hydraulic system. (4) The three-position four-way electromagnetic directional valve in the hydraulic system is energized to supply oil to the rodless cavity of the loading cylinder, thereby controlling the piston rod of the loading cylinder to extend intermittently, and the displacement of each extension is equal. (5) When the piston rod of the loading cylinder extends, it drives the loading tooling to move slowly until the loading tooling contacts the test object. (6) After the loading tooling contacts the test object, the double-cylinder loading hydraulic control system controls the loading cylinder to extend intermittently with the same displacement. Under the action relationship of action and reaction, the sum of the measured values of the first force sensor and the second force sensor gradually increases. (7) For the first hydraulic system, the double-cylinder loading hydraulic control system calculates the sum of the measured values of the first force sensor and the second force sensor in real time and compares it with the total loading force. If the sum of the measured values of the two force sensors is lower than the total loading force, the voltage of the proportional overflow valve is continuously increased, and the piston rod of the loading cylinder continues to extend intermittently until the sum of the measured values of the two force sensors is equal to the total loading force. For the second hydraulic system, the dual-cylinder loading hydraulic control system counts the sum of the measured values ​​of the first force sensor and the second force sensor in real time, and compares the difference between the measured values ​​of the first force sensor and the second force sensor; if the measured value deviation of the first force sensor and the second force sensor is greater than the set value, the dual-cylinder loading hydraulic control system adjusts the input voltage of the first electric proportional pressure reducing valve and the second electric proportional pressure reducing valve until the measured value deviation of the first force sensor and the second force sensor is less than the set value; at the same time, the dual-cylinder loading hydraulic control system compares the sum of the measured values ​​of the first force sensor and the second force sensor with the total loading force. If the sum of the measured values ​​of the two force sensors is lower than the total loading force, the voltage of the proportional relief valve continues to be increased, and the piston rod of the loading cylinder continues to extend intermittently until the sum of the measured values ​​of the two force sensors is equal to the total loading force; (8) After the loading force applied by the hydraulic system reaches the requirement, the test begins. The test time depends on the test object.

[0015] The beneficial effects of the present invention are as follows: the present invention effectively solves the difficult problems of high pressure, large cylinder and high requirements on hydraulic components in a single cylinder loading hydraulic system under equal loading force.

[0016] The hydraulic system and the control process in the dual-cylinder loading hydraulic control system provided by the present invention are simple, and the corresponding control method can ensure that the two loading cylinders maintain substantially equal loading forces, and the application value is high.

[0017] The present invention provides different control methods in a targeted manner according to the composition of the control system and the difference in feedback signals, so that the user can select a more appropriate test scheme according to the test object and test requirements, thereby effectively expanding the scope of application of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 This is a schematic diagram of the structure of double cylinder loading in Example 1 of the present invention; Figure 2 is a schematic diagram of the first hydraulic system in Embodiment 1 of the present invention; Figure 3 This is a hydraulic control flow chart based on the force sensor measurement value and the first hydraulic system in Embodiment 2 of the present invention; Figure 4 This is a hydraulic control flow chart based on the displacement sensor measurement value and the first hydraulic system in Embodiment 3 of the present invention; Figure 5 This is the schematic diagram of the second hydraulic system in Embodiment 4 of the present invention; Figure 6 This is the hydraulic control flowchart based on the measurement value of the force sensor and the second hydraulic system in Embodiment 5 of the present invention; Figure 7 This is the hydraulic control flowchart based on the measurement value of the displacement sensor and the second hydraulic system in Embodiment 6 of the present invention; Markings in the figure: 1. Displacement sensor, 2. Loading cylinder, 3. Transition plate, 4. First force sensor, 5. Hinge block, 6. Loading tooling, 7. Second force sensor, 8. Synchronous element, 9. Three-position four-way electromagnetic reversing valve, 10. Motor pump, 11. Electro-hydraulic proportional relief valve, 12. First electro-hydraulic proportional reducing valve, 13. Second electro-hydraulic proportional reducing valve. Detailed implementation manners

[0020] The present invention will be further described in detail below in conjunction with the drawings and embodiments, but it shall not be used as a basis for any limitation to the invention.

[0021] Embodiment 1 A double-cylinder loading hydraulic control system based on proportional control includes a double-cylinder loading structure and a first hydraulic system for controlling the double-cylinder loading.

[0022] As shown in Figure 1 , the double-cylinder loading structure includes two loading cylinders 2 for loading the loading tooling 6. The front end of the piston rod of the loading cylinder 2 is processed with an external thread for connecting the transition plate 3. A force sensor is installed on the side of the transition plate 3 facing the loading tooling 6, and the force sensor is connected to the loading tooling 6 through the hinge block 5. The force sensors on the two loading cylinders 2 are the first force sensor 4 and the second force sensor 7 respectively. The two loading cylinders 2 are connected to the first hydraulic system, and the first hydraulic system controls the actions of the two loading cylinders 2.

[0023] Among them, the loading tooling 6 can be a loading beam or a loading plate, and the specific shape can be determined according to the shape of the object to be loaded and the loading requirements.

[0024] The structure of the first hydraulic system is as shown in Figure 2 , and it includes a synchronous element 8, a three-position four-way electromagnetic reversing valve 9, a motor pump 10, and an electro-hydraulic proportional relief valve 11.

[0025] The motor pump 10 is connected to the P port on the three-position four-way solenoid directional control valve 9 through a one-way valve and a filter on the oil path. The inlet port of the electro-hydraulic proportional relief valve 11 is connected to the P port of the three-position four-way solenoid directional control valve 9. The outlet port of the electro-hydraulic proportional relief valve 11 is directly connected to the oil tank. The A port on the three-position four-way solenoid directional control valve 9 is connected to the inlet port of the synchronization element 8. The synchronization element 8 has two outlet ports, which are respectively directly connected to the rodless cavity oil ports of the two loading cylinders 2. The rodless cavity oil ports of the two loading cylinders 2 are connected to the B port of the three-position four-way solenoid directional control valve 9. The T port of the three-position four-way solenoid directional control valve 9 is connected to the oil tank.

[0026] The synchronization element 8 is a mechanical flow splitting structure. For example, a flow splitting valve is adopted, and the flow rate of the hydraulic oil in the two output circuits is adjusted through its own internal components to ensure that the flow rates of the two paths are the same, thereby ensuring the synchronous extension and retraction of the piston rods of the two loading cylinders 2.

[0027] Embodiment 2 A dual-cylinder loading hydraulic control method based on proportional control. This method adopts the dual-cylinder loading hydraulic control system described in Embodiment 1. The feedback signal of the control system is the measured value of the force sensor. The feedback signal is fed back to the electro-hydraulic proportional relief valve 11, and the electro-hydraulic proportional relief valve 11 automatically adjusts the input voltage value, and then adjusts the input pressure value of the rodless cavities of the two loading cylinders 2, thereby realizing the adjustment of the loading force. As Figure 3 shown, the method specifically includes the following steps: 1. Determine the total loading force according to the test object of the dual-cylinder loading hydraulic control system; 2. According to the determined total loading force F 总 and the diameter of the rodless cavity of the loading cylinder 2 D 1, calculate the required pressure P of the hydraulic system according to the following formula; ; 3. The hydraulic control system automatically adjusts the voltage of the proportional relief valve 11 according to the calculated pressure P. This voltage is 5% lower than the voltage corresponding to the calculated pressure P, so as to provide pressure for the loading cylinder 2 through the hydraulic system; 4. The three-position four-way solenoid directional control valve 9 in the hydraulic system is energized to supply oil to the rodless cavities of the loading cylinders 2, and then control the piston rods of the loading cylinders 2 to slowly extend; 5. When the piston rods of the loading cylinders 2 extend, drive the loading tooling 6 to move slowly until the loading tooling 6 contacts the test object; 6. After the loading tooling 6 contacts the test object, under the action of the action and reaction forces, the pressure of the hydraulic system starts to increase, the piston rod continues to extend, and the system pressure continues to increase until it reaches the pressure set by the proportional relief valve 11; 7. In the first hydraulic system, the control system continuously calculates the sum of the measured values of the first force sensor 4 and the second force sensor 7, and compares it with the total loading force F 总 for comparison. If the sum of the measured values of the two force sensors is lower than the total loading force F 总 , the voltage of the proportional overflow valve 11 is continuously increased until the sum of the measured values of the two force sensors is equal to the total loading force F 总 ; 8. After the loading force applied by the first hydraulic system reaches the requirement, the test begins. The test time depends on the test object.

[0028] Embodiment 3 As Figure 1 shown, on the basis of Embodiment 1, this embodiment sets a displacement sensor 1 on each loading cylinder 2. The displacement sensor 1 is fixed at the tail of the loading cylinder 2 and is used to measure the real-time displacement of the piston rod of the loading cylinder 2. Specifically, the measuring component of the displacement sensor 1 is installed inside the piston rod of the loading cylinder 2 and moves synchronously with the piston rod, so as to ensure the accuracy of displacement measurement. The remaining structural settings are the same as those in Embodiment 1.

[0029] In this embodiment, when loading and testing the test object, the measured value of the displacement sensor is used as the feedback signal of the control system. The feedback signal is fed back to the electro-hydraulic proportional overflow valve 11, and the electro-hydraulic proportional overflow valve 11 automatically adjusts the input voltage value, and then adjusts the input pressure value of the rodless chambers of the two loading cylinders 2, so as to realize the adjustment of the loading force. As Figure 4 shown, the method specifically includes the following steps: 1. Determine the total loading force according to the test object of the double-cylinder loading hydraulic control system; 2. According to the determined total loading force F 总 , the diameter D 1 of the rodless chamber of the loading cylinder 2, calculate the required pressure P of the hydraulic system according to the following formula; ; 3. The hydraulic control system automatically adjusts the voltage of the proportional overflow valve 11 according to the calculated pressure P. This voltage is 5% lower than the voltage corresponding to the calculated pressure P, so as to provide pressure for the loading cylinder 2 through the hydraulic system; 4. The three-position four-way electromagnetic directional valve 9 in the hydraulic system is energized to supply oil to the rodless chambers of the loading cylinders 2, and then control the piston rods of the loading cylinders 2 to extend intermittently, that is, the displacement of each extension of the loading cylinder is equal; 5. When the piston rod of the loading cylinder 2 extends, it drives the loading tooling 6 to move slowly until the loading tooling 6 contacts the test object; 6. After the loading tooling 6 contacts the test object, the control system controls the loading oil cylinder to extend intermittently with the same displacement. Under the action relationship of the action force and the reaction force, the sum of the measured values of the first force sensor 4 and the second force sensor 7 gradually increases; 7. In the first hydraulic system, the control system continuously statistics the sum of the measured values of the first force sensor 4 and the second force sensor 7, and compares it with the total loading force F 总 If the sum of the measured values of the two force sensors is lower than the total loading force F 总 , then continue to increase the voltage of the proportional overflow valve 11, and the piston rod of the loading oil cylinder continues to extend intermittently until the sum of the measured values of the two force sensors is equal to the total loading force F 总 ; 8. After the loading force applied by the first hydraulic system reaches the requirement, start the test, and the test time depends on the test object.

[0030] Example 4 The main difference between this example and Example 1 is the hydraulic system. The second hydraulic system adopted in this example adds two electro-hydraulic proportional pressure reducing valves compared with the first hydraulic system described above. Therefore, the composition of the second hydraulic system is as follows: As Figure 5 shown, the motor pump 10 is connected to the P port of the three-position four-way electromagnetic directional control valve 9 through a check valve and a filter on the oil path. The inlet port of the electro-hydraulic proportional overflow valve 11 is connected to the P port of the three-position four-way electromagnetic directional control valve 9. The outlet port of the electro-hydraulic proportional overflow valve 11 is directly connected to the fuel tank. The A port of the three-position four-way electromagnetic directional control valve 9 is connected to the inlet port of the synchronization element 8. The two outlet ports of the synchronization element 8 are respectively connected to the rodless cavity oil ports of the loading oil cylinder 2 through the first electro-hydraulic proportional pressure reducing valve 12 and the second electro-hydraulic proportional pressure reducing valve 13. The rod chamber oil port of the loading oil cylinder 2 is connected to the B port of the three-position four-way electromagnetic directional control valve 9.

[0031] In the first hydraulic system of Example 1, the loading forces of all the loading oil cylinders 2 are uniformly controlled by the electro-hydraulic proportional overflow valve 11, and the loading force of each loading oil cylinder 2 cannot be adjusted separately. In the second hydraulic system of this example, the loading force of the corresponding loading oil cylinder 2 can be adjusted separately through the electro-hydraulic proportional pressure reducing valve, and it can ensure that the deviation of the loading force output by each loading oil cylinder 2 is within 2% or other set values, which is specifically set according to the test requirements.

[0032] In the first hydraulic system of Example 1, the feedback signal of its control system is only fed back to the electro-hydraulic proportional overflow valve 11 in the hydraulic system. The electro-hydraulic proportional overflow valve 11 automatically adjusts the input voltage value, and then adjusts the input pressure value of the rodless cavities of the two loading oil cylinders 2, so as to achieve the adjustment of the loading force.

[0033] In the second hydraulic system of this embodiment, the feedback signal of its control system is first fed back to the electro-hydraulic proportional relief valve 11 in the hydraulic system. The electro-hydraulic proportional relief valve 11 automatically adjusts the input voltage value, and then adjusts the input pressure values of the rodless chambers of the two loading cylinders 2, so as to realize the adjustment of the loading force. When the deviation between the measured values of the first force sensor 4 and the second force sensor 7 is less than 2%, the input voltages of the first electro-hydraulic proportional reducing valve 12 and the second electro-hydraulic proportional reducing valve 13 do not need to be adjusted; when the deviation between the measured values of the first force sensor 4 and the second force sensor 7 is greater than 2%, in addition to adjusting the input voltage of the electro-hydraulic proportional relief valve 11, the control system also needs to adjust the input voltages of the first electro-hydraulic proportional reducing valve 12 and the second electro-hydraulic proportional reducing valve 13 until the deviation between the measured values of the first force sensor 4 and the second force sensor 7 is less than 2%. Among them, the "deviation between the measured values of the first force sensor 4 and the second force sensor 7" refers to the percentage of the absolute value of the difference between the measured values of the first force sensor 4 and the second force sensor 7 in the smaller measured value, which can be set according to the test requirements.

[0034] Therefore, compared with the first hydraulic system, the second hydraulic system can control the loading forces of the two loading cylinders respectively, ensure that the output forces of the two loading cylinders are consistent, and make the test piece more evenly stressed. When in use, the user can choose to use the first hydraulic system or the second hydraulic system according to the test object and test requirements, and the loading forces of the two loading cylinders can be basically equal. Only when the second hydraulic system is used, the control is more accurate.

[0035] In other embodiments of this embodiment, a displacement sensor 1 is provided on each loading cylinder 2. The displacement sensor 1 is fixed at the tail of the loading cylinder 2 and is used to measure the real-time displacement of the loading cylinder 2. Specifically, the measuring component of the displacement sensor 1 is installed in the piston rod of the loading cylinder 2 and moves synchronously with the piston rod, so as to ensure the accuracy of displacement measurement.

[0036] Embodiment 5 A dual-cylinder loading hydraulic control method based on proportional control. This method uses the dual-cylinder loading hydraulic control system described in Embodiment 4. The feedback signal of the control system is the measured value of the force sensor, and its control process is as Figure 6 shown.

[0037] Compared with the method described in Embodiment 2, the main difference lies in Step 7. In the second hydraulic system, the control system continuously calculates the sum of the measured values of the first force sensor 4 and the second force sensor 7, and simultaneously compares the deviation between the measured values of the first force sensor 4 and the second force sensor 7. If the deviation between the measured values of the first force sensor 4 and the second force sensor 7 is greater than 2%, the control system adjusts the input voltages of the first electro-hydraulic proportional relief valve 12 and the second electro-hydraulic proportional relief valve 13 until the deviation between the measured values of the first force sensor 4 and the second force sensor 7 is less than 2%. The control system simultaneously compares the sum of the measured values of the first force sensor 4 and the second force sensor 7 with the total loading force F 总 and if the sum of the measured values of the two force sensors is lower than the total loading force F 总 , the voltage of the proportional overflow valve 11 is continuously increased until the sum of the measured values of the two force sensors is equal to the total loading force F 总 . The remaining steps are the same as those described in Embodiment 2

[0038] Embodiment 6 A hydraulic control method for double-cylinder loading based on proportional control. This method uses the double-cylinder loading hydraulic control system described in Embodiment 4, and the feedback signal of the control system is the measured value of the displacement sensor. Its control process is as Figure 7 shown

[0039] Compared with the method described in Embodiment 3, the main difference lies in Step 7. In the second hydraulic system, the control system continuously calculates the sum of the first force sensor 4 and the second force sensor 7, and simultaneously compares the difference between the measured values of the displacement sensors at the tails of the two loading cylinders 2. If the deviation between the measured values of the displacement sensors at the tails of the two loading cylinders 2 is greater than 2%, the control system adjusts the input voltages of the first electro-hydraulic proportional relief valve 12 and the second electro-hydraulic proportional relief valve 13, thereby adjusting the extension lengths of the two loading cylinders until the deviation between the measured values of the displacement sensors at the tails of the two loading cylinders 2 is less than 2%. The control system simultaneously calculates the sum of the measured values of the first force sensor 4 and the second force sensor 7, and compares it with the total loading force F 总 and if the sum of the measured values of the two force sensors is lower than the total loading force F 总 , the voltage of the proportional overflow valve 11 is continuously increased, and the piston rods of the loading cylinders 2 continue to extend intermittently until the sum of the measured values of the two force sensors is equal to the total loading force F 总 . Among them, the "deviation of the measured value of the displacement sensor" refers to the percentage of the absolute value of the difference between the measured values of the two displacement sensors in the smaller measured value, which can be set according to the test requirements

[0040] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Those of ordinary skill in the art should understand that the specific implementation manners of the present invention can be modified or equivalently replaced by referring to the above embodiments. Any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention are within the scope of protection of the claims pending for approval.

Claims

1. A dual-cylinder loading hydraulic control system based on proportional control, comprising a dual-cylinder loading structure and a hydraulic system for controlling the dual-cylinder loading, characterized in that: The double-cylinder loading structure includes two loading cylinders connected to the loading tooling. Force sensors, namely a first force sensor and a second force sensor, are arranged between the piston rods of the two loading cylinders and the loading tooling. The hydraulic system is a first hydraulic system, which includes a synchronization element, a three-position four-way electromagnetic directional control valve, a motor pump, and an electro-hydraulic proportional overflow valve. The motor pump is connected to the P port on the three-position four-way electromagnetic directional control valve through an oil circuit. The inlet port of the electro-hydraulic proportional overflow valve is connected to the P port of the three-position four-way electromagnetic directional control valve. The outlet port of the electro-hydraulic proportional overflow valve is connected to the oil tank. The A port on the three-position four-way electromagnetic directional control valve is connected to the inlet port of the synchronization element. The two outlet ports of the synchronization element are respectively connected to the rodless cavity oil ports of the two loading cylinders. The rodless cavity oil ports of the two loading cylinders are connected to the B port of the three-position four-way electromagnetic directional control valve. The T port of the three-position four-way electromagnetic directional control valve is connected to the oil tank.

2. The hydraulic control system for dual-cylinder loading based on proportional control according to claim 1, wherein: The first hydraulic system is replaced by a second hydraulic system, which includes a synchronization element, a three-position four-way electromagnetic directional control valve, a motor pump, an electro-hydraulic proportional overflow valve, a first electro-hydraulic proportional pressure reducing valve, and a second electro-hydraulic proportional pressure reducing valve. The motor pump is connected to the P port on the three-position four-way electromagnetic directional control valve through an oil circuit. The inlet port of the electro-hydraulic proportional overflow valve is connected to the P port of the three-position four-way electromagnetic directional control valve. The outlet port of the electro-hydraulic proportional overflow valve is connected to the oil tank. The A port on the three-position four-way electromagnetic directional control valve is connected to the inlet port of the synchronization element. The two outlet ports of the synchronization element are respectively connected to the rodless cavity oil ports of the two loading cylinders through the first electro-hydraulic proportional pressure reducing valve and the second electro-hydraulic proportional pressure reducing valve. The rodless cavity oil ports of the two loading cylinders are connected to the B port of the three-position four-way electromagnetic directional control valve. The T port of the three-position four-way electromagnetic directional control valve is connected to the oil tank.

3. A hydraulic control system for double-cylinder loading based on proportional control according to claim 1 or 2, characterized in that: The loading tooling is a loading beam or a loading plate.

4. A proportional control-based dual-cylinder loading hydraulic control system according to claim 1 or 2, characterized in that: A displacement sensor is arranged on each loading cylinder. The displacement sensor is fixed at the tail of the loading cylinder and is used to measure the real-time displacement of the piston rod of the loading cylinder.

5. A dual-cylinder loading hydraulic control system based on proportional control according to claim 4, characterized in that: The measuring component of the displacement sensor is installed inside the piston rod of the loading cylinder and moves synchronously with the piston rod.

6. A hydraulic control method for dual-cylinder loading based on proportional control, characterized in that: This method adopts the double-cylinder loading hydraulic control system as described in Claim 1, and uses the measured value of the force sensor as the feedback signal of the double-cylinder loading hydraulic control system. The method includes the following steps: (1) Determine the total loading force according to the test object of the double-cylinder loading hydraulic control system. (2) Calculate the pressure P required for the first hydraulic system according to the total loading force and the diameter of the rodless cavity of the loading cylinder. (3) Automatically adjust the voltage of the proportional overflow valve according to the calculated pressure P, and provide pressure for the loading cylinder through the first hydraulic system. (4) The three-position four-way electromagnetic directional control valve in the first hydraulic system is energized to supply oil to the rodless cavity of the loading cylinder, thereby controlling the piston rod of the loading cylinder to slowly extend. (5) When the piston rod of the loading cylinder extends, it drives the loading tooling to move slowly until the loading tooling contacts the test object. (6) After the loading tooling contacts the test object, under the action relationship of action and reaction, the pressure of the first hydraulic system starts to increase, the piston rod continues to extend, and the system pressure continues to increase until it reaches the pressure set by the proportional overflow valve. (7) The dual-cylinder loading hydraulic control system real-time statistically sums the measured values of the first force sensor and the second force sensor, and compares it with the total loading force. If the sum of the measured values of the two force sensors is lower than the total loading force, the voltage of the proportional overflow valve is continuously increased until the sum of the measured values of the two force sensors is equal to the total loading force; (8) After the loading force applied by the first hydraulic system reaches the requirement, the test starts, and the test time depends on the test object.

7. A hydraulic control method for double-cylinder loading based on proportional control, characterized in that: This method uses the dual-cylinder loading hydraulic control system as described in claim 2, and uses the measured value of the force sensor as the feedback signal of the dual-cylinder loading hydraulic control system; this method includes the following steps: (1) Determine the total loading force according to the test object of the dual-cylinder loading hydraulic control system; (2) Calculate the pressure P required for the second hydraulic system according to the total loading force and the diameter of the rodless cavity of the loading cylinder; (3) Automatically adjust the voltage of the proportional overflow valve according to the calculated pressure P, and provide pressure for the loading cylinder through the second hydraulic system; (4) The three-position four-way electromagnetic directional valve in the second hydraulic system is energized to supply oil to the rodless cavity of the loading cylinder, thereby controlling the piston rod of the loading cylinder to slowly extend; (5) When the piston rod of the loading cylinder extends, it drives the loading tooling to move slowly until the loading tooling contacts the test object; (6) After the loading tooling contacts the test object, under the action relationship of the action force and the reaction force, the pressure of the second hydraulic system starts to increase, the piston rod continues to extend, and the system pressure continues to increase until it reaches the pressure set by the proportional overflow valve; (7) The dual-cylinder loading hydraulic control system real-time statistically sums the measured values of the first force sensor and the second force sensor, and compares the difference between the measured values of the first force sensor and the second force sensor; if the deviation between the measured values of the first force sensor and the second force sensor is greater than the set value, the dual-cylinder loading hydraulic control system adjusts the input voltages of the first electro-hydraulic proportional reducing valve and the second electro-hydraulic proportional reducing valve until the deviation between the measured values of the first force sensor and the second force sensor is less than the set value; at the same time, the dual-cylinder loading hydraulic control system compares the sum of the measured values of the first force sensor and the second force sensor with the total loading force. If the sum of the measured values of the two force sensors is lower than the total loading force, the voltage of the proportional overflow valve is continuously increased until the sum of the measured values of the two force sensors is equal to the total loading force; (8) After the loading force applied by the second hydraulic system reaches the requirement, the test starts, and the test time depends on the test object.

8. A hydraulic control method for dual-cylinder loading based on proportional control according to claim 7, characterized in that: The set value is 2%.

9. A hydraulic control method for dual-cylinder loading based on proportional control, characterized in that: This method uses the dual-cylinder loading hydraulic control system as described in claim 4, and uses the measured value of the displacement sensor as the feedback signal of the dual-cylinder loading hydraulic control system; this method includes the following steps: (1) Determine the total loading force according to the test object of the dual-cylinder loading hydraulic control system; (2) Calculate the pressure P required for the hydraulic system according to the total loading force and the diameter of the rodless cavity of the loading cylinder; (3) Automatically adjust the voltage of the proportional overflow valve according to the calculated pressure P, and provide pressure for the loading cylinder through the hydraulic system; (4) The three-position four-way electromagnetic directional valve in the hydraulic system is energized to supply oil to the rodless cavity of the loading cylinder, thereby controlling the intermittent extension of the piston rod of the loading cylinder, and the displacement of each extension is equal; (5) When the piston rod of the loading cylinder extends, it drives the loading tooling to move slowly until the loading tooling contacts the test object; (6) After the loading tooling contacts the test object, the dual-cylinder loading hydraulic control system controls the loading cylinder to extend intermittently by the same displacement. Under the action relationship of action and reaction forces, the sum of the measured values of the first force sensor and the second force sensor gradually increases; (7) For the first hydraulic system, the dual-cylinder loading hydraulic control system continuously calculates the sum of the measured values of the first force sensor and the second force sensor and compares it with the total loading force. If the sum of the measured values of the two force sensors is lower than the total loading force, the voltage of the proportional relief valve is continuously increased, and the piston rod of the loading cylinder continues to extend intermittently until the sum of the measured values of the two force sensors is equal to the total loading force; For the second hydraulic system, the dual-cylinder loading hydraulic control system continuously calculates the sum of the measured values of the first force sensor and the second force sensor and compares the difference between the measured values of the first force sensor and the second force sensor. If the deviation between the measured values of the first force sensor and the second force sensor is greater than the set value, the dual-cylinder loading hydraulic control system adjusts the input voltages of the first electro-hydraulic proportional reducing valve and the second electro-hydraulic proportional reducing valve until the deviation between the measured values of the first force sensor and the second force sensor is less than the set value. At the same time, the dual-cylinder loading hydraulic control system compares the sum of the measured values of the first force sensor and the second force sensor with the total loading force. If the sum of the measured values of the two force sensors is lower than the total loading force, the voltage of the proportional relief valve is continuously increased, and the piston rod of the loading cylinder continues to extend intermittently until the sum of the measured values of the two force sensors is equal to the total loading force; (8) After the loading force applied by the hydraulic system reaches the requirement, the test starts, and the test time depends on the test object.

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