CN116906394A - A dual piezoelectric ring self-sensing bend-driven two-stage slide valve electro-hydraulic servo valve - Google Patents

Abstract

A dual piezoelectric ring self-sensing bend-driven two-stage slide valve electro-hydraulic servo valve. The valve structure is symmetrical, and the left and right control valve cores are bent and driven by the left and right piezoelectric rings respectively. Due to the piezoelectric effect, the piezoelectric ring will generate a voltage signal proportional to the size of its bending deformation during driving. After being extracted through the self-sensing circuit, it is transmitted to the control circuit to form a self-sensing closed-loop control of the displacement of the valve core. The movement of the control valve core in the control valve sleeve causes the control valve port to open, producing oil that drives the movement of the main valve core. The movement of the main valve core will drive the feedback rod to rotate around the center of the spring tube, causing the upper end of the feedback rod to drive the control valve sleeve toward the control valve. Movement in the direction of mouth closing. When the control valve port is completely closed, the main valve core stops moving, forming a mechanical closed-loop control of the main valve core position. The invention adopts dual piezoelectric ring drive and dual closed-loop control but does not require sensors. It has the advantages of fast response, high precision, small size, and little influence on temperature by performance.

Description

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

Technical field

The invention belongs to the field of electro-hydraulic servo control, and specifically relates to a dual-piezoelectric ring self-sensing bend-driven two-stage slide valve electro-hydraulic servo valve.

Background technique

As the core basic component of high-end electro-hydraulic equipment, the electro-hydraulic servo valve's frequency response, accuracy and reliability 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 life of the entire system. , Therefore, high-speed, precision and high-reliability electro-hydraulic servo valves have always been a major demand for high-end electro-hydraulic servo equipment in the country.

It can be seen from the development history of electro-hydraulic servo valves that improving the frequency response and dynamic load capacity of the electro-mechanical converter used in the servo valve is the prerequisite for improving the dynamic performance of the electro-hydraulic servo valve. The emergence of high-precision, high-frequency response, and high-reliability electro-mechanical actuators represented by piezoelectric actuators provides opportunities for the development of high-speed precision electro-hydraulic servo valves. Piezoelectric actuators have low energy consumption, no heat, long service life, no electromagnetic interference, short response time, and large energy saving potential. Its application research in electro-hydraulic servo valves has always been a hot spot in the research of new electro-hydraulic servo valves. At present, there are many studies on the application of piezoelectric bimorph, piezoelectric stack, and amplified piezoelectric actuators in electro-hydraulic servo valves. The research on piezoelectric ring bending actuators in electro-hydraulic servo valves is in its infancy, but in terms of volume and performance, Comprehensive comparison with price and other aspects, the piezoelectric ring bending actuator has greater advantages.

Like other piezoelectric actuators, the piezoelectric ring bending actuator has better dynamic performance, but its output is also hysteretic and nonlinear. When the displacement and output force are large, its volume is still large. Therefore, although the piezoelectric ring bend-driven electro-hydraulic servo valve has good dynamic performance, the entire valve is large in size and the output will show hysteretic nonlinearity. In order to reduce the volume and nonlinearity while ensuring the flow rate, the current piezoelectric ring bend-driven electro-hydraulic servo valve usually adopts a two-stage structure and uses two displacement sensors to perform electrical feedback closed-loop control of the two-stage valve core. One sensor performs closed-loop control of the position of the control stage spool, and the second sensor performs closed-loop control of the position of the main spool of the power stage. Although adding two sensors can improve performance, it will increase the cost, increase the size and reduce the reliability of the entire valve.

Contents of the invention

In order to overcome the above shortcomings, the present invention provides a dual piezoelectric ring self-sensing bend-driven two-stage slide valve type electro-hydraulic servo valve. The electro-hydraulic servo valve divides the control valve core into left and right parts. Two piezoelectric ring bending actuators are driven separately. The control stage adopts self-sensing closed-loop control, and the power stage adopts mechanical closed-loop control. Therefore, the electro-hydraulic servo valve has fast response speed, high control accuracy, high reliability, small size, etc. advantage.

In order to achieve the above objects, the technical solutions adopted by the present invention are:

A dual piezoelectric ring self-sensing bend-driven two-stage slide valve electro-hydraulic servo valve, including 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, control valve sleeve, control valve body, the left piezoelectric ring is arranged in the left end cavity of the control valve body, its side is glued to the side wall of the control valve body cavity, and the middle of the left piezoelectric ring The inner wall of the round hole 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 set in the control valve sleeve and connected through threads. The right end of the left output rod; the right piezoelectric ring is arranged in the right end cavity of the valve body, and its side is glued to the side wall of the control valve body cavity, and the inner wall of the middle circular hole of the right piezoelectric ring is connected to the side wall of the right support seat Glue, 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 in the control valve sleeve and is threaded to the left end of the right output rod.

To further optimize, the control valve is sleeved in the control valve body, and the two have a clearance fit.

Further optimization, the left control valve core and the right control valve core 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 the blind hole at the right end is the oil return chamber of the left control valve core, and the outer circumference An annular groove is provided, and an oil hole connected to 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 right end of the right control valve core is provided with The left end of the threaded hole is the oil return chamber of the right control valve core. There is an annular groove on the outer periphery. There is an oil hole in the annular groove that communicates with the oil return chamber of the right control valve core. The outlet of the oil return chamber of the right control valve core is connected with the control valve. The oil return chamber of the control valve is connected to the main valve oil return chamber through the control valve oil return channel, and the main valve oil return chamber is connected to the oil return port T.

Further optimization, 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 constitute the left control valve port. The annular groove on the right control valve core is The left end and the right end of the right annular groove form the right control valve port.

Further optimization, the left piezoelectric ring drives the left control valve core to move in the control valve sleeve, thereby changing the left control valve opening, and the right piezoelectric ring drives the right control valve core to move in the control valve sleeve, thereby changing the right control valve opening. Valve opening.

Further optimization, when the left piezoelectric ring and the right piezoelectric ring produce bending deformation, they also generate voltage signals proportional to their deformation, which are fed back to the controller through self-sensing circuit detection and processing to realize control of the left control valve. Self-sensing closed-loop control of core and right control spool displacement.

Further optimization, the oil from the left control valve port or the right control valve port drives the main valve core to move, and drives the lower end of the feedback rod to move, causing the feedback rod to rotate around the center of the spring tube, and the upper end of the feedback rod pushes the control valve sleeve to the left The control valve port and the right control valve port move in the direction of closing. When the left control valve port and the right control valve port 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 and the left control valve The displacement produced by the spool is proportional to that of the right control spool.

Further optimization, the left output rod is threadedly connected to the left support base and locked by the left zero-adjustment nut, and the right output rod is threadedly connected with the right support base and locked by the right zero-adjustment nut. The above-mentioned connection threads are all fine-threaded and loose. Open the left zero-adjustment nut or the right zero-adjustment nut to rotate the left output rod and right output rod to move the left control valve core and the right control valve core to complete the zero position adjustment of the control valve.

Further optimization, 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 center line of the control valve body, and the lower end of the feedback rod forms a ball joint with the main valve core. connection, the main valve core is located in the main valve sleeve, and the two have a clearance fit, and the main valve sleeve is located in the main valve body, and the two have an interference fit.

To further optimize, 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.

The beneficial effects of the present invention are:

1. Divide the control valve core into left and right parts. The left and right control valve cores are driven by the left and right piezoelectric rings respectively. Compared with a single piezoelectric ring driving the entire control valve core, the pressure of the piezoelectric ring is effectively reduced. To drive the load, a smaller piezoelectric ring driver can be selected. In addition, the left-right symmetrical structure can eliminate thermally induced displacement caused by temperature changes and improve the accuracy of self-sensing control;

2. The displacement of the control valve core is obtained through the self-sensing signal generated by the piezoelectric effect of the piezoelectric ring. It is fed back to the controller through extraction and processing to form a self-sensing electrical feedback closed-loop control of the displacement of the control valve core. By adjusting the controller parameters, the Improve the movement accuracy and response speed of the control spool. The displacement of the main spool feeds back its displacement signal to the control valve sleeve through the feedback rod, causing the control valve port that drives the main spool to close, forming a closed loop of mechanical feedback to the displacement of the main spool. Control, the two-stage closed-loop feedback of the entire electro-hydraulic servo valve does not require additional sensors, which can effectively reduce costs, reduce volume, and improve reliability.

In summary, the dual piezoelectric ring self-sensing bend-driven two-stage slide valve electro-hydraulic servo valve designed by the present invention divides the control stage valve core into two parts, which are bent and driven by the left and right piezoelectric rings respectively. The stage adopts self-sensing closed-loop control, and the power stage forms a mechanical closed-loop control through a feedback rod without the need for additional sensors. Therefore, the electro-hydraulic servo valve designed in the present invention has fast response speed, high control accuracy, small size, low cost, and high reliability. Significant advantages.

Description of the drawings

Figure 1 is a structural diagram of a dual piezoelectric ring self-sensing bend-driven two-stage slide valve electro-hydraulic servo valve;

Figure 2 is the oil passage diagram of the double piezoelectric ring self-sensing bend-driven two-stage slide valve electro-hydraulic servo valve;

Figure 3 is a schematic diagram of the piezoelectric ring self-sensing drive circuit;

Figure 4 shows the bending deformation diagram of the piezoelectric ring;

Marked in the picture: 1. Left piezoelectric ring, 2. Right piezoelectric ring, 3. Left support base, 4. Right support base, 5. Left zero-adjustment nut, 6. Right zero-adjustment nut, 7. Left output rod, 8. Right output rod, 9. Main valve sleeve, 10. Main valve core, 11. Left fixed orifice, 12. Right fixed orifice, 13. Main valve body, 14. Feedback rod, 15. Spring 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 Channel, 24. Left high-pressure oil chamber, 25. Right high-pressure oil chamber, 26. Main valve oil return chamber, 27. Left annular groove of control valve sleeve, 28. Right annular groove of control valve sleeve, 29. Oil return of left control valve core Chamber, 30. Right control valve core oil return chamber, 31. Left control valve port, 32. Right control valve port, 33. Control valve oil return chamber, 34. Control valve oil return channel.

Detailed ways

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

A dual piezoelectric ring self-sensing bend-driven two-stage slide valve type electro-hydraulic servo valve, a dual piezoelectric ring self-sensing bend-driven two-stage slide valve type electro-hydraulic servo valve, including a left piezoelectric ring 1 , right piezoelectric ring 2, left output rod 7, right output rod 8, feedback rod 14, left control valve core 16, right control valve core 17, control valve sleeve 18, control valve body 19, the left piezoelectric ring 1 It is arranged 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 round hole of the left piezoelectric ring 1 is connected to the left support seat 3 through glue. The left output The left end of the rod 7 is threadedly connected to the left support seat 3 and locked by the left zero-adjustment nut 5. The left control valve core 17 is set in the control valve sleeve 18 and is threadedly connected to the right end of the left output rod 7; the right The piezoelectric ring 2 is arranged in the right 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 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 threadedly connected to the right support seat 4 and locked by the right zero adjustment nut 6. The right control valve core 17 is located in the control valve sleeve 18 and is threadedly connected to the left end of the right output rod 8 to control The valve sleeve 18 is located in the control valve body 19, and the two have a clearance fit.

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 oil return chamber 29, and there are There is an annular groove, and the left control valve core 16 is provided with an oil return hole that communicates with the left control valve core oil return chamber 29, and the outlet of the left control valve core oil return chamber 29 communicates with the control valve oil return chamber 33; the right control valve core The right end of the valve core 17 is provided with a threaded hole, the left end is the right control valve core oil return chamber 30, and an annular groove is provided on its outer periphery. The right control valve core 17 is provided with an oil return hole communicating with the right control valve core oil return chamber 30. , the outlet of the right control valve core oil return chamber 30 is connected with the control valve oil return chamber 33. The control valve oil return chamber 33 is connected with the main valve oil return chamber 26 through the control valve oil return channel 34. The main valve oil return chamber 26 is connected with the return oil return chamber 34. Oil port T is connected.

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 constitute the left control valve port 31. The left end of the annular groove on the control valve core 17 and the right end of the right annular groove 28 of the control valve sleeve form a right control valve port 32.

The left piezoelectric ring 1 drives the left control valve core 16 to move in the control valve sleeve 18, thereby changing the opening of the left control valve port 31, and the right piezoelectric ring 2 drives the right control valve core 17 to move in the control valve sleeve 18, Thereby changing the opening of the right control valve port 32. When the left piezoelectric ring 1 and the right piezoelectric ring 2 produce bending deformation, they also generate a voltage signal proportional to the deformation, which is fed back to the controller through self-sensing circuit detection and processing to achieve control of the left valve core. 16 and self-sensing closed-loop control of the displacement of the right control valve core 17. The oil in the left control valve port 31 and the right control valve port 32 drives the main valve core 10 to move, and drives the lower end of the feedback rod 14 to move. The feedback rod 14 will rotate around the center of the spring tube 15, and the stiffness of the feedback rod 14 must be It is large and cannot produce 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. The displacement of the main valve core 10 is proportional to the displacement of the left and right control valve cores.

The left output rod 7 is threadedly connected to the left support base 3 and locked by the left zero-adjustment nut 5. The right output rod 8 is threadedly connected with the right support base 4 and locked by the right zero-adjustment nut 6. The above connection threads are all thin. teeth, loosen the left zero-adjustment nut 5 or the right zero-adjustment nut 6, thereby rotating the left and right output rods to move the left and right control valve cores, completing the zero position adjustment of the control valve.

The two ends of the feedback rod 14 are spheres, and its upper end passes through the inner hole of the spring tube 15 and is connected to the control valve sleeve 18. The spring tube 15 is installed on the center line of the control valve body 19, and the lower end of the feedback rod 14 is connected to the main valve core 10. The main valve core 10 is located in the main valve sleeve 9, and the two have a clearance fit. The main valve sleeve 9 is located in the main valve body 13, and the two have 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 movement displacement of the left and right control valve cores.

The piezoelectric ring bending actuator adopts three-wire bipolar drive. When the input voltage u is 0, the piezoelectric ring does not bend and deform; when the input voltage u is in the range of -100V~0, the piezoelectric ring bends to the right; When the input voltage u is in the range of 0~100V, the piezoelectric ring bends to the left, and its shape after bending and deformation is shown in Figure 4. Piezoelectric materials have dual functions of driving and sensing. By measuring the self-induction voltage, the piezoelectric ring bending actuator has the ability to sense its own deformation. Based on Figure 3, a bridge circuit is built. By selecting the appropriate capacitor C ₃ , the voltage u _f proportional to the displacement at both ends when the piezoelectric ring bending drive actuator is working can be measured.

The working principle of the double piezoelectric ring self-sensing bend-driven two-stage slide valve electro-hydraulic servo valve proposed by the present invention is shown in Figures 1 and 2. After the system is supplied with oil, high-pressure oil flows into the oil inlet P. The main valve body 8 is divided into three paths along the rear 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 oil inlet passage 22 and the left fixed orifice 11, and the right path It flows into the right control chamber 21 and the right annular groove 28 of the control valve sleeve through the right oil inlet passage 23 and the right fixed orifice 12. When the input command of the controller is zero, and the input voltage of the left piezoelectric ring 1 and the right piezoelectric ring 2 is 0, the above two piezoelectric rings do not bend and deform, and the left control valve port 31 and the right control valve port 32 are in Disabled. The pressure generated by the oil 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 there is no flow output from the control oil ports A and B.

When the controller input command is positive, the input voltage u of the left piezoelectric ring 1 is negative and bends and deforms to the left. The left control valve core 16 is pushed to the left through the left support seat 3 and the left output rod 7, and the left control valve port 31 is off. The input voltage u of the right piezoelectric ring 2 is a positive value, and it bends and deforms to the left. The right control valve core 17 is pushed to the left through the right support seat 4 and the right output rod 8, and the right control valve port 32 is opened. The oil in the right annular groove 28 of the control valve sleeve passes through the right control valve port 32, the right control valve core oil return chamber 30, the control valve oil return chamber 33, the control valve oil return channel 34, the main valve oil return chamber 26, and the oil return port. T flows back to the oil tank, causing the right control chamber 21 to communicate with the oil tank, causing the pressure in the right control chamber 21 to drop. The oil in the chamber acts on the main valve core 10 and the hydraulic pressure to the left decreases, while the oil in the left control chamber 20 The hydraulic pressure remains unchanged, and the hydraulic force acting on the main valve core 10 to the right also remains unchanged. Therefore, the main valve core 10 is moved to the right by the resultant force, and drives 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 move 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 rises. When the right control valve port 32 is completely closed, the oil in the right control chamber 21 The hydraulic pressure 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 stops moving. Its displacement is proportional to the displacement of the control valve sleeve 18. The displacement of the control valve sleeve 18 is equal to the right control valve core. 17 Movement displacement to the left. When the load pressure difference is constant, control port A outputs a flow rate proportional to the displacement of the main valve core 10.

When the input command of the controller is negative, the input voltage u of the right piezoelectric ring 2 is negative and bends and deforms to the right. The right control valve core 17 is pushed to the right through the right support seat 4 and the right output rod 8, and the right control valve port is 32 is off. The input voltage u of the left piezoelectric ring 1 is positive, and it bends and deforms to the right. It pushes the left control valve core 16 to move to the right through the left support seat 3 and the left output rod 7, and the left control valve port 31 opens. The oil in the left annular groove 27 of the control valve sleeve passes through the left control valve port 31, the left control valve core oil return chamber 29, the control valve oil return chamber 33, the control valve oil return channel 34, the main valve oil return chamber 26, and the oil return port. T flows back to the oil tank, causing the left control chamber 20 to communicate with the oil tank. The pressure in the chamber decreases, and the hydraulic pressure acting on the main valve core 10 decreases, while the pressure in the right control chamber 21 remains unchanged, and its effect on the main valve core 10 The hydraulic pressure to the left on 10 remains unchanged, so the main valve core 10 is subject to the total external force to the left, moves to the left, and drives the lower end of the feedback rod 14 to move to the left, causing the feedback rod 14 to rotate clockwise around the center of the spring tube, and its upper end Push the control valve sleeve 18 to the right, causing the left control valve port 31 to gradually close. During this process, the pressure in the left control chamber 20 gradually rises. When the left control valve port 31 is completely closed, the pressure in the left control chamber 20 is equal to the right control valve port 31. The pressure in the cavity 21 and the hydraulic pressure on both ends of the main valve core 10 are equal and stop moving. Its displacement is proportional to the movement displacement of the control valve sleeve 18. The displacement of the control valve sleeve 18 is equal to the rightward movement displacement of the left control valve core 16. . When the load pressure difference is constant, control port B outputs a flow rate proportional to the displacement of the main valve core 10.

To sum up, when the load pressure difference is constant, the output flow of the valve 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 is the distance between the lower end of the feedback rod 14 and the center of rotation and the feedback The ratio of the distance from the upper end of rod 14 to the center of rotation. Under self-sensing closed-loop control, the control valve core displacement is approximately proportional to the input command, so the output flow of the entire valve is approximately proportional to the size of the input command, and the direction is related to the polarity of the controller input command.

The main features, usage methods, basic principles and advantages of the present invention have been shown and described above. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also be modified according to actual conditions. Various changes and modifications are possible, which fall within the scope of the claimed invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims (10)

1. The double-piezoelectric-ring self-sensing bend-driving two-stage slide valve type electrohydraulic servo valve is characterized by comprising 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), wherein the left piezoelectric ring (1) is arranged in a left end cavity of the control valve body (19), the side surface of the left piezoelectric ring is glued with the left end cavity side wall of the control valve body (19), the inner wall of a middle circular hole of the left piezoelectric ring (1) is glued with the side surface of a left supporting seat (3), the left end of the left output rod (7) is connected with the left supporting seat (3) in a threaded manner and locked through a left zero adjusting nut (5), and the left control valve core (16) is arranged in the control valve sleeve (18) and is connected with the right end of the left output rod (7) through threads; the right piezoelectric ring (2) is arranged in a right end cavity of the control valve body (19), the side surface of the right piezoelectric ring is glued with the side wall of the right end cavity of the control valve body (19), the inner wall of a middle circular hole of the right piezoelectric ring (2) is glued with the side wall of the right supporting seat (4), the right end of the right output rod (8) is connected with the right supporting seat (4) in a threaded manner and locked through the right zeroing nut (6), and the right control valve core (17) is arranged in the control valve sleeve (18) and is connected with the left end of the right output rod (8) in a threaded manner.

2. A two-stage spool valve type electrohydraulic servo valve with self sensing and bending driving dual piezoelectric rings as in claim 1, wherein said control valve sleeve (18) is disposed in a control valve body (19) and is in clearance fit with the two.

3. The dual-piezoelectric ring self-sensing bend-driving two-stage slide valve type electrohydraulic servo valve according to claim 1, characterized in that 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, the right end blind hole is a left control valve core oil return cavity (29), an annular groove is arranged at the periphery, an oil hole communicated with the left control valve core oil return cavity (29) is arranged in the annular groove, and the outlet of the left control valve core oil return cavity (29) is communicated with the control valve oil return cavity (33); the right end of the right control valve core (17) is provided with a threaded hole, the left end is a right control valve core oil return cavity (30), the outer periphery of the right control valve core oil return cavity is provided with an annular groove, an oil hole communicated with the right control valve core oil return cavity (30) is arranged in the annular groove, an outlet of the right control valve core oil return cavity (30) is communicated with a control valve oil return cavity (33), the control valve oil return cavity (33) is communicated with a main valve oil return cavity (26) through a control valve oil return channel (34), and the main valve oil return cavity (26) is communicated with an oil return port T.

4. The dual piezoelectric ring self-sensing bend-driven two-stage slide valve type electrohydraulic servo valve according to claim 2, characterized in that a left annular groove (27) and a right annular groove (28) are arranged in an inner hole of the control valve sleeve (18), a left control valve port (31) is formed by 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, and a right control valve port (32) is formed by 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.

5. A dual piezoelectric ring self-sensing bend-driven two-stage spool valve type electrohydraulic servo valve according to claim 1, characterized in that said left piezoelectric ring (1) drives the left control valve core (16) to move in the control valve sleeve (18) to change the opening of the left control valve port (31), and the right piezoelectric ring (2) drives the right control valve core (17) to move in the control valve sleeve (18) to change the opening of the right control valve port (32).

6. The dual-piezoelectric ring self-sensing bend-driving two-stage slide valve type electrohydraulic servo valve according to claim 1, characterized in that the left piezoelectric ring (1) and the right piezoelectric ring (2) generate bending deformation and generate voltage signals proportional to the deformation, and the voltage signals are fed back to a controller after being detected and processed by a self-sensing circuit so as to realize self-sensing closed-loop control of the motion displacement of a left control valve core (16) and a right control valve core (17).

7. A dual piezoelectric ring self-sensing bend-driven two-stage spool valve type electrohydraulic servo valve according to claim 1, characterized in that oil from left control valve port (31) or right control valve port (32) drives main spool (10) to move and drives the lower end of feedback rod (14) to move, so that feedback rod (14) rotates around the center of spring tube (15), the upper end of feedback rod (14) pushes control valve sleeve (18) to move towards the closing direction of left control valve port (31) and right control valve port (32), when left control valve port (31) and right control valve port (32) are completely closed, main spool (10) stops moving, forming closed loop control of the position of main spool (10), so that the displacement of main spool (10) is proportional to the displacement generated by left control spool (16) and right control spool (17).

8. The dual piezoelectric ring self-sensing bend-driving two-stage slide valve type electrohydraulic servo valve according to claim 1, characterized in that the left output rod (7) is in threaded connection with the left supporting seat (3) and locked by the left zeroing nut (5), the right output rod (8) is in threaded connection with the right supporting seat (4) and locked by the right zeroing nut (6), the connecting threads are fine teeth, the left zeroing nut (5) or the right zeroing nut (6) is loosened, and therefore the left output rod (7) and the right output rod (8) are rotated to enable the left control valve core (16) and the right control valve core (17) to move, and zero adjustment of the control valve is completed.

9. The dual-piezoelectric-ring self-sensing bend-driving two-stage slide valve type electrohydraulic servo valve according to claim 1, characterized in that two ends of the feedback rod (14) are spheres, the upper ends of the feedback rod penetrate through an inner hole of the spring tube (15) to form spherical hinge connection with the control valve sleeve (18), the spring tube (15) is arranged on a central line of the control valve body (19), the lower end of the feedback rod (14) is in spherical hinge connection with the main valve core (10), the main valve core (10) is arranged in the main valve sleeve (9), the main valve sleeve (9) is in clearance fit with the main valve body (13), and the main valve sleeve are in interference fit with each other.

10. A dual piezoelectric ring self-sensing bend-driven two-stage spool valve electro-hydraulic servo valve as claimed in claim 1, wherein the distance from the upper end of the feedback rod (14) to the rotation center thereof is greater than the distance from the lower end to the rotation center thereof, so that the displacement of the main spool (10) is greater than the displacement of the left control spool (16) and the right control spool (17).