A dual-piezoelectric ring self-sensing bend-driven two-stage slide valve electro-hydraulic servo valve

Abstract

A two-stage spool-type electro-hydraulic servo valve with dual piezoelectric rings and self-sensing bending drive is disclosed. The valve has a symmetrical structure, with the left and right control valve cores driven by bending motions of the left and right piezoelectric rings, respectively. Due to the piezoelectric effect, the piezoelectric rings generate voltage signals proportional to their bending deformation during operation. These signals are extracted by a self-sensing circuit and transmitted to the control circuit to form a self-sensing closed-loop control of the control valve core displacement. The movement of the control valve core within the control valve sleeve opens the control valve port, generating oil that drives the main valve core. This movement causes a feedback rod to rotate around the center of the Bourdon tube, causing the upper end of the feedback rod to move the control valve sleeve towards the direction of valve port closure. When the control valve port is fully closed, the main valve core stops moving, forming a mechanical closed-loop control of the main valve core position. This invention employs dual piezoelectric ring drive and dual closed-loop control without requiring sensors, offering advantages such as fast response, high accuracy, small size, and minimal temperature-dependent performance.

Description

Technical Field

[0001] This invention belongs to the field of electro-hydraulic servo control, specifically relating to a dual-piezoresistive self-sensing curved-drive two-stage slide valve electro-hydraulic servo valve. Background Technology

[0002] As a core component of high-end electro-hydraulic equipment, the frequency response, accuracy, and reliability of electro-hydraulic servo valves directly restrict the control accuracy and response speed of the entire high-end electro-hydraulic equipment servo system, and also directly affect the reliability and lifespan of the entire system. Therefore, high-speed, high-precision, and high-reliability electro-hydraulic servo valves have always been a major requirement for the country's high-end electro-hydraulic servo equipment.

[0003] The development history of electro-hydraulic servo valves shows that improving the frequency response and dynamic load-carrying capacity of the electro-mechanical converter used in servo valves is a prerequisite for improving the dynamic performance of electro-hydraulic servo valves. The emergence of high-precision, high-frequency-response, and high-reliability electro-mechanical converters, represented by piezoelectric actuators, has provided an opportunity for the development of high-speed precision electro-hydraulic servo valves. Piezoelectric actuators are characterized by low energy consumption, no heat generation, long service life, no electromagnetic interference, short response time, and great energy-saving potential; their application research in electro-hydraulic servo valves has always been a hot topic in the research of new electro-hydraulic servo valves. Currently, piezoelectric bicrystalline, piezoelectric stack, and enlarged piezoelectric actuators are widely used in electro-hydraulic servo valve research. Research on piezoelectric ring-bend actuators in electro-hydraulic servo valves is still in its early stages, but considering factors such as size, performance, and price, piezoelectric ring-bend actuators have greater advantages.

[0004] Like other piezoelectric actuators, piezoelectric ring bending-driven actuators exhibit good dynamic performance, but their output is also hysteretic and nonlinear, resulting in a relatively large size even with large displacement and output force. Therefore, while piezoelectric ring bending-driven electro-hydraulic servo valves offer good dynamic performance, their overall size is large and their output exhibits hysteresis and nonlinearity. To reduce size and nonlinearity while maintaining flow rate, current piezoelectric ring bending-driven electro-hydraulic servo valves typically employ a two-stage structure with two displacement sensors for closed-loop electrical feedback control of the valve cores in both stages. The first sensor provides closed-loop control of the position of the control-stage valve core, and the second sensor provides closed-loop control of the position of the power-stage main valve core. While adding two sensors improves performance, it increases the overall valve cost, size, and reduces reliability. Summary of the Invention

[0005] To overcome the above shortcomings, this invention provides a dual-piezoelectric ring self-sensing bend-drive type two-stage slide valve electro-hydraulic servo valve. This electro-hydraulic servo valve divides the control valve core into left and right parts, which are driven by two piezoelectric ring bend-drive type actuators respectively. The control stage adopts self-sensing closed-loop control, and the power stage adopts mechanical closed-loop control. Therefore, this electro-hydraulic servo valve has the advantages of fast response speed, high control accuracy, high reliability, and small size.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A dual-piezoelectric ring self-sensing bend-drive type two-stage slide valve electro-hydraulic servo valve includes a left piezoelectric ring, a right piezoelectric ring, a left output rod, a right output rod, a feedback rod, a left control valve core, a right control valve core, a control valve sleeve, and a control valve body. The left piezoelectric ring is disposed in the left end cavity of the control valve body, and its side is glued to the side wall of the control valve body cavity. The inner wall of the middle circular hole of the left piezoelectric ring is glued to the side of the left support seat. The left end of the left output rod is threaded to the left support seat and locked by a left zero-adjustment nut. The left control valve core is disposed in the control valve sleeve and is threaded to the right end of the left output rod. The right piezoelectric ring is disposed in the right end cavity of the valve body, and its side is glued to the side wall of the control valve body cavity. The inner wall of the middle circular hole of the right piezoelectric ring is glued to the side wall of the right support seat. The right end of the right output rod is threaded to the right support seat and locked by a right zero-adjustment nut. The right control valve core is disposed in the control valve sleeve and is threaded to the left end of the right output rod.

[0008] Further optimization involves the control valve being fitted inside the control valve body, with a clearance fit between the two.

[0009] Further optimization involves symmetrically distributing the left and right control valve cores on both sides of the control valve sleeve. The left end of the left control valve core has a threaded hole, and its right end has a blind hole serving as the oil return chamber. An annular groove is provided on its outer periphery, and an oil hole communicating with the oil return chamber is located within the annular groove. The outlet of the left control valve core's oil return chamber communicates with the control valve's oil return chamber. Similarly, the right end of the right control valve core has a threaded hole, and its left end serves as the right control valve core's oil return chamber. An annular groove is provided on its outer periphery, and an oil hole communicating with the right control valve core's oil return chamber is located within the annular groove. The outlet of the right control valve core's oil return chamber communicates with the control valve's oil return chamber. The control valve's oil return chamber communicates with the main valve's oil return chamber through the control valve's oil return channel. The main valve's oil return chamber communicates with the oil return port T.

[0010] Further optimization involves providing a left annular groove and a right annular groove in the inner hole of the control valve sleeve. The right end of the annular groove on the left control valve core and the left end of the left annular groove constitute the left control valve port, and the left end of the annular groove on the right control valve core and the right end of the right annular groove constitute the right control valve port.

[0011] In a further optimization, the left piezoelectric ring drives the left control valve core to move within the control valve sleeve, thereby changing the opening degree of the left control valve port, and the right piezoelectric ring drives the right control valve core to move within the control valve sleeve, thereby changing the opening degree of the right control valve port.

[0012] Further optimization involves the left and right piezoelectric rings generating voltage signals proportional to their bending deformation, which are then detected and processed by a self-sensing circuit and fed back to the controller to achieve self-sensing closed-loop control of the displacement of the left and right control valve cores.

[0013] Further optimization involves the oil from the left or right control valve port driving the main valve core to move, which in turn moves the lower end of the feedback rod, causing the feedback rod to rotate around the center of the spring tube. The upper end of the feedback rod pushes the control valve sleeve to move in the direction of closing the left and right control valve ports. When the left and right control valve ports are completely closed, the main valve core stops moving, forming a closed-loop control of the main valve core position, making the displacement of the main valve core proportional to the displacement generated by the left and right control valve cores.

[0014] Further optimization involves threading the left output rod to the left support seat and locking it with the left zero-adjustment nut, and threading the right output rod to the right support seat and locking it with the right zero-adjustment nut. All of the above connecting threads are fine-pitch. Loosening the left or right zero-adjustment nut allows the left and right output rods to be rotated, causing the left and right control valve cores to move and completing the zero-position adjustment of the control valve.

[0015] Further optimization involves the feedback rod having spherical ends. The upper end passes through the inner hole of the spring tube and forms a ball joint connection with the control valve sleeve. The spring tube is installed on the centerline of the control valve body. The lower end of the feedback rod forms a ball joint connection with the main valve core. The main valve core is located inside the main valve sleeve, and the two are clearance-fitted. The main valve sleeve is located inside the main valve body, and the two are interference-fitted.

[0016] Further optimization involves ensuring that the distance from the upper end of the feedback rod to its rotation center is greater than the distance from the lower end to the rotation center, so that the displacement of the main valve core is greater than the displacement of the left and right control valve cores.

[0017] The beneficial effects of this invention are as follows:

[0018] 1. The control valve core is divided into left and right parts, and the left and right control valve cores are driven by left and right piezoelectric rings respectively. Compared with a single piezoelectric ring driving the entire control valve core, the driving load of the piezoelectric ring is effectively reduced. Therefore, a smaller piezoelectric ring driver can be selected. In addition, the left and right symmetrical structure can eliminate thermal displacement caused by temperature changes and improve the accuracy of self-sensing control.

[0019] 2. The displacement of the control valve core is obtained through the self-sensing signal generated by the piezoelectric effect of the piezoelectric ring. This signal is extracted, processed, and fed back to the controller to form a self-sensing electrical feedback closed-loop control of the control valve core displacement. By adjusting the controller parameters, the motion accuracy and response speed of the control valve core can be improved. The displacement of the main valve core is fed back to the control valve sleeve through the feedback rod, causing the control valve port that drives the main valve core to close, forming a mechanical feedback closed-loop control of the main valve core displacement. The two-stage closed-loop feedback of the entire electro-hydraulic servo valve does not require additional sensors, which can effectively reduce costs, reduce size, and improve reliability.

[0020] In summary, the dual-piezoelectric ring self-sensing bending-drive two-stage spool electro-hydraulic servo valve designed in this invention divides the control stage valve core into two parts, which are driven by bending by the left and right piezoelectric rings respectively. The control stage adopts self-sensing closed-loop control, and the power stage forms mechanical closed-loop control through the feedback rod. No additional sensors are required. Therefore, the electro-hydraulic servo valve designed in this invention has significant advantages such as fast response speed, high control accuracy, small size, low cost, and high reliability. Attached Figure Description

[0021] Figure 1 This is a structural diagram of a dual-piezoresistive self-sensing, bend-driven, two-stage slide valve electro-hydraulic servo valve.

[0022] Figure 2 This is a diagram of the oil passage for a two-stage spool valve electro-hydraulic servo valve with dual piezoelectric rings and self-sensing bending drive.

[0023] Figure 3 This is a schematic diagram of a piezoelectric ring self-sensing drive circuit.

[0024] Figure 4 Diagram showing the bending deformation of the piezoelectric ring;

[0025] Markings in the diagram: 1. Left piezoelectric ring, 2. Right piezoelectric ring, 3. Left support base, 4. Right support base, 5. Left zero-adjusting nut, 6. Right zero-adjusting nut, 7. Left output rod, 8. Right output rod, 9. Main valve sleeve, 10. Main valve core, 11. Left fixed throttle orifice, 12. Right fixed throttle orifice, 13. Main valve body, 14. Feedback rod, 15. Bourdon tube, 16. Left control valve core, 17. Right control valve core, 18. Control valve sleeve, 19. Control... Valve body, 20. Left control chamber, 21. Right control chamber, 22. Left oil inlet passage, 23. Right oil inlet passage, 24. Left high-pressure oil chamber, 25. Right high-pressure oil chamber, 26. Main valve return oil chamber, 27. Left annular groove of control valve sleeve, 28. Right annular groove of control valve sleeve, 29. Left control valve core return oil chamber, 30. Right control valve core return oil chamber, 31. Left control valve port, 32. Right control valve port, 33. Control valve return oil chamber, 34. Control valve return oil passage. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will now be clearly and completely described with reference to the accompanying drawings.

[0027] A dual-piezoelectric ring self-sensing bend-drive type two-stage spool valve electro-hydraulic servo valve includes a left piezoelectric ring 1, a right piezoelectric ring 2, a left output rod 7, a right output rod 8, a feedback rod 14, a left control valve core 16, a right control valve core 17, a control valve sleeve 18, and a control valve body 19. The left piezoelectric ring 1 is disposed in the left end cavity of the control valve body 19, and its side is glued to the side wall of the cavity of the control valve body 19. The middle circular hole of the left piezoelectric ring 1 is glued to the left support seat 3. The left end of the left output rod 7 is threaded to the left support seat 3. The left control valve core 17 is locked in place by the left zero-adjustment nut 5 and is located inside the control valve sleeve 18. It is connected to the right end of the left output rod 7 by a thread. The right piezoelectric ring 2 is located in the right cavity of the control valve body 19. Its side is glued to the side wall of the cavity of the control valve body 19. The inner wall of the middle circular hole of the right piezoelectric ring 2 is glued to the side wall of the right support seat 4. The right end of the right output rod 8 is threaded to the right support seat 4 and locked in place by the right zero-adjustment nut 6. The right control valve core 17 is located inside the control valve sleeve 18 and is connected to the left end of the right output rod 8 by a thread. The control valve sleeve 18 is located inside the control valve body 19, and the two are fitted with a clearance fit.

[0028] The left control valve core 16 and the right control valve core 17 are symmetrically distributed on both sides of the control valve sleeve 18. The left end of the left control valve core 16 is a threaded hole, and its right end is the left control valve core return oil chamber 29, which has an annular groove on its outer periphery. The left control valve core 16 has a return oil hole that communicates with the left control valve core return oil chamber 29. The outlet of the left control valve core return oil chamber 29 communicates with the control valve return oil chamber 33. The right end of the right control valve core 17 is a threaded hole, and its left end is the right control valve core return oil chamber 30, which has an annular groove on its outer periphery. The right control valve core 17 has a return oil hole that communicates with the right control valve core return oil chamber 30. The outlet of the right control valve core return oil chamber 30 communicates with the control valve return oil chamber 33. The control valve return oil chamber 33 communicates with the main valve return oil chamber 26 through the control valve return oil channel 34. The main valve return oil chamber 26 communicates with the return oil port T.

[0029] The inner hole of the control valve sleeve 18 is provided with a left annular groove 27 and a right annular groove 28. The right end of the annular groove on the left control valve core 16 and the left end of the left annular groove 27 of the control valve sleeve form the left control valve port 31. The left end of the annular groove on the right control valve core 17 and the right end of the right annular groove 28 of the control valve sleeve form the right control valve port 32.

[0030] The left piezoelectric ring 1 drives the left control valve core 16 to move within the control valve sleeve 18, thereby changing the opening of the left control valve port 31. The right piezoelectric ring 2 drives the right control valve core 17 to move within the control valve sleeve 18, thereby changing the opening of the right control valve port 32. While the left and right piezoelectric rings 1 and 2 undergo bending deformation, they also generate voltage signals proportional to their deformation. These signals are detected and processed by a self-sensing circuit and fed back to the controller to achieve self-sensing closed-loop control of the displacement of the left and right control valve cores 16 and 17. The oil flow from the left and right control valve ports 31 and 32 drives the main valve core 10 to move, which in turn moves the lower end of the feedback rod 14. The feedback rod 14 rotates around the center of the spring tube 15. The feedback rod 14 must have high stiffness and cannot undergo bending deformation. The upper end of the feedback rod 14 pushes the control valve sleeve 18 to move in the direction of closing the left and right control valve ports. When the left and right control valve ports are completely closed, the main valve core 10 stops moving, forming a closed-loop control of the position of the main valve core 10, so that the displacement of the main valve core 10 is proportional to the displacement of the left and right control valve cores.

[0031] The left output rod 7 is threadedly connected to the left support seat 3 and locked by the left zero-adjustment nut 5. The right output rod 8 is threadedly connected to the right support seat 4 and locked by the right zero-adjustment nut 6. All the above connecting threads are fine threads. Loosening the left zero-adjustment nut 5 or the right zero-adjustment nut 6 allows the left and right output rods to be rotated, causing the left and right control valve cores to move and completing the zero-position adjustment of the control valve.

[0032] The feedback rod 14 has spherical ends. Its upper end passes through the inner hole of the spring tube 15 and connects to the control valve sleeve 18. The spring tube 15 is installed on the centerline of the control valve body 19. The lower end of the feedback rod 14 is connected to the main valve core 10, which is located inside the main valve sleeve 9 with a clearance fit. The main valve sleeve 9 is located inside the main valve body 13 with an interference fit. The distance from the upper end of the feedback rod 14 to its rotation center is greater than the distance from the lower end to the rotation center, so that the displacement of the main valve core 10 is greater than the displacement of the left and right control valve cores.

[0033] The piezoelectric ring bending actuator uses a three-wire bipolar drive. When the input voltage... u When the input voltage is 0, the piezoelectric ring does not bend or deform; when the input voltage is 0, the piezoelectric ring does not bend or deform. u When the voltage is in the range of -100V to 0V, the piezoelectric ring bends to the right; when the input voltage... u In the range of 0~100V, the piezoelectric ring bends to the left, and its deformed shape is as follows: Figure 4 As shown. Piezoelectric materials possess both driving and sensing functions; by measuring their self-induced voltage, piezoelectric ring bending actuators can sense their own deformation. Based on Figure 3 Construct a bridge circuit and select appropriate capacitors. C 3. This allows us to measure the voltage of the piezoelectric ring bending actuator, which is proportional to the displacement at both ends, during operation. uf .

[0034] The working principle of the dual-piezoresistive self-sensing curved-drive two-stage spool valve electro-hydraulic servo valve proposed in this invention is as follows: Figure 1 and Figure 2 As shown, after the system supplies oil, the high-pressure oil flows into the main valve body 8 through the inlet P and then splits into three paths along the oil passage. The middle path flows into the power main valve; the left path flows into the left control chamber 20 and the left annular groove 27 of the control valve sleeve through the left inlet passage 22 and the left fixed throttle orifice 11; and the right path flows into the right control chamber 21 and the right annular groove 28 of the control valve sleeve through the right inlet passage 23 and the right fixed throttle orifice 12. When the controller input command is zero, the input voltage of the left piezoelectric ring 1 and the right piezoelectric ring 2 is 0, and neither of the two piezoelectric rings bends or deforms. The left control valve port 31 and the right control valve port 32 are in the closed state. The oil pressure in the left control chamber 20 and the right control chamber 21 is equal, so the hydraulic pressure on the left and right ends of the main valve core 10 is equal. The main valve core 10 is in the zero position and does not move. There is no flow output from the control ports A and B.

[0035] When the controller input command is positive, the input voltage of left piezoelectric ring 1 is... u The value is negative, causing it to bend and deform to the left. This deformation, along with the left support 3 and left output rod 7, pushes the left control valve core 16 to the left, closing the left control valve port 31. The input voltage of the right piezoelectric ring 2... u When the value is positive, the valve bends and deforms to the left, pushing the right control valve core 17 to the left via the right support seat 4 and the right output rod 8, thus opening the right control valve port 32. The oil in the right annular groove 28 of the control valve sleeve flows back to the oil tank through the right control valve port 32, the right control valve core return oil chamber 30, the control valve return oil chamber 33, the control valve return oil channel 34, the main valve return oil chamber 26, and the return port T, making the right control chamber 21 connected to the oil tank. This causes a pressure drop in the right control chamber 21, resulting in a decrease in the hydraulic pressure exerted on the main valve core 10 to the left. Meanwhile, the oil pressure in the left control chamber 20 remains unchanged, and its hydraulic pressure exerted on the main valve core 10 to the right also remains unchanged. Therefore, the main valve core 10 experiences a resultant force to the right and moves to the right. This causes the lower end of the feedback rod 14 to move, and the feedback rod 14 rotates around the spring tube. Its upper end pushes the control valve sleeve 18 to the left, causing the right control valve port 32 to gradually close. During this process, the pressure in the right control chamber 21 gradually increases. When the right control valve port 32 is completely closed, the oil pressure in the right control chamber 21 is equal to the oil pressure in the left control chamber 20. The hydraulic pressure on both ends of the main valve core 10 is equal, and it stops moving. The magnitude of its displacement is proportional to the displacement of the control valve sleeve 18, which is equal to the leftward displacement of the right control valve core 17. When the load pressure difference is constant, the output of control port A is proportional to the displacement of the main valve core 10.

[0036] When the controller input command is negative, the input voltage of the right piezoelectric ring 2 is... uThe value is negative, causing it to bend and deform to the right. This deformation, along with the right support 4 and right output rod 8, pushes the right control valve core 17 to the right, closing the right control valve port 32. The left piezoelectric ring 1 input voltage... u When the value is positive, the valve bends and deforms to the right, pushing the left control valve core 16 to the right via the left support 3 and the left output rod 7, thus opening the left control valve port 31. The oil in the left annular groove 27 of the control valve sleeve flows back to the oil tank via the left control valve port 31, the left control valve core return oil chamber 29, the control valve return oil chamber 33, the control valve return oil channel 34, the main valve return oil chamber 26, and the return port T. This connects the left control chamber 20 to the oil tank, causing a decrease in pressure within it. Consequently, the hydraulic pressure acting on the main valve core 10 to the right decreases, while the pressure in the right control chamber 21 remains unchanged, and the hydraulic pressure acting on the main valve core 10 to the left remains unchanged. Therefore, the main valve core 10 experiences a net external force to the left, moving to the left and driving the lower end of the feedback rod 14. Moving to the left causes the feedback rod 14 to rotate clockwise around the center of the spring tube. Its upper end pushes the control valve sleeve 18 to the right, gradually closing the left control valve port 31. During this process, the pressure inside the left control chamber 20 gradually increases. When the left control valve port 31 is completely closed, the pressure inside the left control chamber 20 equals the pressure inside the right control chamber 21. The hydraulic pressure at both ends of the main valve core 10 is equal, and it stops moving. Its displacement is proportional to the displacement of the control valve sleeve 18, which is equal to the rightward displacement of the left control valve core 16. When the load pressure difference is constant, the output flow rate of control port B is proportional to the displacement of the main valve core 10.

[0037] In summary, when the load pressure difference is constant, the valve's output flow rate is proportional to the displacement of the main valve core 10, and the displacement of the main valve core 10 is proportional to the displacement of the control valve core. The ratio of this ratio is the distance from the lower end of the feedback rod 14 to the center of rotation to the distance from the upper end of the feedback rod 14 to the center of rotation. Under self-sensing closed-loop control, the displacement of the control valve core is approximately proportional to the input command. Therefore, the overall valve output flow rate is approximately proportional to the magnitude of the input command, and its direction is related to the polarity of the controller's input command.

[0038] The foregoing has shown and described the main features, usage methods, basic principles, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention based on actual circumstances without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A dual-piezoelectric ring self-sensing bend-driven two-stage slide valve electro-hydraulic servo valve, characterized in that, The system includes a left piezoelectric ring, a right piezoelectric ring, a left output rod, a right output rod, a feedback rod, a left control valve core, a right control valve core, a control valve sleeve, and a control valve body. The left piezoelectric ring is disposed in the left-end cavity of the control valve body, and its side is glued to the side wall of the left-end cavity of the control valve body. The inner wall of the middle circular hole of the left piezoelectric ring is glued to the side of the left support seat. The left end of the left output rod is threaded to the left support seat and locked by the left zero-adjustment nut. The left control valve core is disposed in the control valve sleeve and is threaded to the right end of the left output rod. The right piezoelectric ring is disposed in the right end cavity of the control valve body. Inside the cavity, its side is glued to the right end cavity sidewall of the control valve body, the inner wall of the middle circular hole of the right piezoelectric ring is glued to the sidewall of the right support seat, the right end of the right output rod is threaded to the right support seat and locked by the right zero-adjustment nut, the right control valve core is located inside the control valve sleeve and is threaded to the left end of the right output rod; the inner hole of the control valve sleeve is provided with a left annular groove and a right annular groove, the right end of the annular groove on the left control valve core and the left end of the left annular groove of the control valve sleeve form the left control valve port, and the left end of the annular groove on the right control valve core and the right end of the right annular groove of the control valve sleeve form the right control valve port; The left and right control valve cores are symmetrically distributed on both sides of the control valve sleeve. The left end of the left control valve core is a threaded hole, and its right end is a blind hole that serves as the oil return chamber for the left control valve core. An annular groove is provided on the outer periphery, and an oil hole communicating with the oil return chamber of the left control valve core is provided in the annular groove. The outlet of the oil return chamber of the left control valve core is connected to the oil return chamber of the control valve. The oil return chamber of the control valve is connected to the oil return chamber of the main valve through the oil return channel of the control valve. The oil return chamber of the main valve is connected to the oil return port T. The two ends of the feedback rod are spheres. The upper end passes through the inner hole of the spring tube and forms a ball joint connection with the control valve sleeve. The spring tube is installed on the centerline of the control valve body. The lower end of the feedback rod forms a ball joint connection with the main valve core. The main valve core is located inside the main valve sleeve, and the two are clearance-fitted. The main valve sleeve is located inside the main valve body, and the two are interference-fitted.

2. The dual-piezoelectric ring self-sensing bending-drive type two-stage slide valve electro-hydraulic servo valve as described in claim 1, characterized in that, The control valve is sleeved within the control valve body, and the two are fitted with a clearance.

3. The dual-piezoelectric ring self-sensing bending-drive type two-stage slide valve electro-hydraulic servo valve as described in claim 1, characterized in that, The right end of the right control valve core is provided with a threaded hole, and the left end is the oil return chamber of the right control valve core. An annular groove is provided on its outer periphery, and an oil hole communicating with the oil return chamber of the right control valve core is provided in the annular groove. The outlet of the oil return chamber of the right control valve core is connected to the oil return chamber of the control valve. The oil return chamber of the control valve is connected to the oil return chamber of the main valve through the oil return channel of the control valve.

4. The dual-piezoelectric ring self-sensing bending-drive type two-stage slide valve electro-hydraulic servo valve as described in claim 1, characterized in that, The left piezoelectric ring drives the left control valve core to move within the control valve sleeve, thereby changing the opening degree of the left control valve port. The right piezoelectric ring drives the right control valve core to move within the control valve sleeve, thereby changing the opening degree of the right control valve port.

5. The dual-piezoelectric ring self-sensing bending-drive type two-stage slide valve electro-hydraulic servo valve as described in claim 1, characterized in that, The left and right piezoelectric rings generate voltage signals proportional to their bending deformation, which are then detected and processed by the self-sensing circuit and fed back to the controller to achieve self-sensing closed-loop control of the movement displacement of the left and right control valve cores.

6. The dual-piezoelectric ring self-sensing bending-drive type two-stage slide valve electro-hydraulic servo valve as described in claim 1, characterized in that, The oil from the left or right control valve port drives the main valve core to move, which in turn moves the lower end of the feedback rod, causing the feedback rod to rotate around the center of the spring tube. The upper end of the feedback rod pushes the control valve sleeve to move in the direction of closing the left and right control valve ports. When the left and right control valve ports are completely closed, the main valve core stops moving, forming a closed-loop control of the main valve core position, so that the displacement of the main valve core is proportional to the displacement generated by the left and right control valve cores.

7. The dual-piezoelectric ring self-sensing bending-drive type two-stage slide valve electro-hydraulic servo valve as described in claim 1, characterized in that, The left output rod is threaded to the left support seat and locked by the left zero-adjustment nut, and the right output rod is threaded to the right support seat and locked by the right zero-adjustment nut. Both threads are fine-pitch. Loosening the left or right zero-adjustment nut allows the left and right output rods to be rotated, causing the left and right control valve cores to move and completing the zero-position adjustment of the control valve.

8. The dual-piezoelectric ring self-sensing bending-drive type two-stage slide valve electro-hydraulic servo valve as described in claim 1, characterized in that, The distance from the upper end of the feedback rod to its rotation center is greater than the distance from the lower end to the rotation center, so that the displacement of the main valve core is greater than the displacement of the left control valve core and the right control valve core.

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