A kind of hydraulic valve spool device of step motor drive with double encoder FOC

Abstract

This invention discloses a stepper motor-driven hydraulic valve spool device employing a dual-encoder FOC (Focus on the Engine) architecture, relating to the field of hydraulic valve spool drive control technology. The device includes a stepper motor, a gear reduction mechanism, a rack, a valve spool, a control circuit board, a drive module, and a first encoder and a second encoder respectively mounted on the motor rotor end and the reduction gear shaft end. The first encoder collects the position and speed information of the motor rotor, while the second encoder collects the rotation angle information of the reduction gear shaft to calculate the actual position of the valve spool. The control circuit board controls the stepper motor through the drive module and receives feedback signals from the dual encoders to achieve closed-loop control of the current loop, speed loop, and position loop. This invention, through the collaborative work of the dual encoders and the three-loop closed-loop control using FOC, effectively compensates for transmission errors, significantly improves valve spool positioning accuracy and control stability, and reduces energy consumption.

Description

Technical Field

[0001] This invention relates to the field of hydraulic valve spool drive control technology, and in particular to a stepper motor drive device for hydraulic valve spools using dual encoder FOC (field orientation control). Background Technology

[0002] Currently, the linear drive of valve cores is achieved by using stepper motors in conjunction with gear reduction mechanisms and rack and pinion transmission. Its basic structure includes a stepper motor, a gear reduction mechanism (motor gear, double gear), a rack, a valve core, and a drive controller. The working principle is as follows: the controller outputs a drive signal to control the stepper motor to rotate. The output shaft of the stepper motor drives the motor gear to rotate. The motor gear meshes with the large gear in the double gear to achieve speed reduction. The small gear in the double gear meshes with the rack, converting the rotational motion into linear motion. This, in turn, drives the rack to perform reciprocating linear motion through the ball joint connecting the valve core, thereby adjusting the valve core opening.

[0003] In existing technologies, stepper motor control methods are mainly divided into two types: one is open-loop control, which does not require feedback elements, has a simple structure and low cost, but has obvious defects. Stepper motors are prone to step loss and cannot sense load changes. When there is backlash, wear, or fluid resistance disturbance in the gear reduction mechanism, the actual position of the valve core will deviate significantly from the preset position of the controller, resulting in low positioning accuracy and failing to meet the requirements of high-precision control. The other type is encoder closed-loop control, but the encoder is only used for closed-loop control and cannot sense load changes. It is used to collect the position and speed information of the gears, but does not use FOC control for real-time current regulation, resulting in large torque ripple and low energy efficiency. Moreover, a single encoder cannot simultaneously take into account high-frequency current feedback and precise position compensation at the transmission end, resulting in insufficient control stability. Summary of the Invention

[0004] The purpose of this invention is to provide a stepper motor driven hydraulic valve core device using dual encoder FOC, so as to solve the technical problems of low positioning accuracy, inability to compensate for transmission error, poor control stability and low energy efficiency in the prior art.

[0005] To achieve the above objectives, the present invention provides a stepper motor driven hydraulic valve core device using dual encoder FOC, comprising a stepper motor and a reduction gear set in a housing, wherein a gear reduction mechanism, a rack guide rail and a rack are mounted on the reduction gear set, and the rack is connected to the valve core in the valve body; It also includes a control circuit board, a drive module, a first encoder, and a second encoder; a first encoder magnet and a second encoder magnet are respectively installed in the housing at positions corresponding to the first encoder and the second encoder. The first encoder is coaxially connected to the rotor of the stepper motor and is used to collect the position and speed information of the motor rotor; the second encoder is coaxially connected to the reduction gear shaft of the gear reduction mechanism and is used to collect the rotation angle information of the reduction gear shaft; the control circuit board is electrically connected to the first encoder, the second encoder, and the drive module, and the drive module is electrically connected to the stepper motor.

[0006] Preferably, guide grooves are provided on both sides of the rack, and guide pressure plates are correspondingly provided on the rack guide rail, with the guide pressure plates embedded in the guide grooves; one end of the rack is connected to the valve core through a ball joint handle, and a preload spring is provided on the ball joint handle through a retaining ring.

[0007] Preferably, the control circuit board uses a microcontroller with an integrated FOC control algorithm to receive feedback signals from the first encoder and the second encoder, output control commands to the drive module, realize the field orientation control of the stepper motor, and form a three-closed-loop control of current loop, speed loop and position loop.

[0008] Preferably, the first encoder is used to provide the control circuit board with position and speed feedback of the motor rotor to realize current closed-loop control and speed closed-loop control; the second encoder is used to provide the control circuit board with rotation angle feedback of the reduction gear shaft to calculate the actual position of the rack and the valve core to realize position closed-loop control.

[0009] Preferably, the drive module has a built-in protection circuit, which includes an overcurrent protection circuit, an overtemperature protection circuit, and a short-circuit protection circuit, used to automatically cut off the drive signal and send a fault signal to the control circuit board when the stepper motor malfunctions.

[0010] Preferably, the gear reduction mechanism includes a motor gear and a double gear. The motor gear is fixedly connected to the output shaft of the stepper motor. The large gear of the double gear meshes with the motor gear, and the small gear of the double gear meshes with the rack. The second encoder is fixedly installed at one end of the reduction gear shaft of the double gear.

[0011] Preferably, both the first encoder and the second encoder are absolute encoders. The first encoder is connected to the encoder interface of the control circuit board via a differential signal line, and the second encoder is connected to another encoder interface of the control circuit board via a differential signal line.

[0012] Preferably, it further includes a current acquisition unit, which is connected to the phase winding of the stepper motor and electrically connected to the ADC port of the control circuit board, for real-time acquisition of the phase current signal of the stepper motor and feedback to the control circuit board.

[0013] Preferably, the control circuit board is configured to automatically switch to single encoder control mode when either the first encoder or the second encoder fails, and continue to achieve closed-loop control using the normally functioning encoder.

[0014] Preferably, the meshing clearance between the motor gear and the large gear of the double gear is 0.01-0.03 mm, and the reduction gear shaft of the double gear is rotatably connected to the housing through a deep groove ball bearing.

[0015] Compared with the prior art, the present invention has the following advantages and technical effects: This invention provides a stepper motor-driven hydraulic valve core device employing a dual-encoder FOC (Focus on the Valve Core). By setting up a first encoder and a second encoder, the two encoders work collaboratively. The first encoder is responsible for high-frequency current feedback to ensure stable motor torque, while the second encoder directly collects motion information from the transmission links to achieve position closed-loop control. This effectively compensates for transmission errors such as gear backlash, wear, and rack meshing deviation, improving positioning accuracy from ±0.05mm in existing technologies to ±0.01mm. Through FOC three-loop control (current loop, speed loop, and position loop), precise decoupled control of the motor current is achieved, reducing torque pulsation. Combined with a preload spring, this mitigates transmission shock, resulting in smoother motor operation, reducing vibration amplitude by over 30% and noise by over 25%. The current closed-loop control dynamically adjusts the motor phase current according to the valve core load, avoiding maintaining high current under light load or stationary conditions, improving energy efficiency by over 20%. Simultaneously, the drive module incorporates a built-in protection circuit and dual-encoder redundancy switching function, greatly enhancing the system's reliability and safety. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention.

[0017] Figure 1 This is a schematic diagram of the overall structure of the device of the present invention.

[0018] Figure 2 This is a schematic diagram showing the connection details between the rack and valve core of the present invention.

[0019] Figure 3 This is a schematic diagram showing the details of the gear reduction and rack transmission of the present invention.

[0020] Figure 4This is a schematic diagram of the placement of the dual encoders in this invention.

[0021] In the diagram: 1. Housing; 2. Stepper motor; 3. Motor gear; 4. Reducer; 5. Rack and pinion guide; 6. First encoder; 7. First encoder magnet; 8. Second encoder; 9. Second encoder magnet; 10. Preload spring; 11. Double gear; 12. Rack; 13. Ball joint; 14. Valve core; 15. Valve body; 16. Control circuit board; 17. Snap ring; 18. Reducer gear shaft; 19. Motor gear shaft. Detailed Implementation

[0022] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other. The described embodiments are merely some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0023] like Figures 1 to 4 As shown, the present invention provides a stepper motor driven hydraulic valve core device using dual encoder FOC, including a stepper motor 2 and a reducer 4 disposed in a housing 1. The reducer 4 is equipped with a gear reduction mechanism, a rack guide rail 5 and a rack 12, and the rack 12 is connected to the valve core 14 in the valve body 15. It also includes a control circuit board 16, a drive module, a first encoder 6, and a second encoder 8; a first encoder magnet 7 and a second encoder magnet 9 are respectively installed in the housing 1 at the positions corresponding to the first encoder 6 and the second encoder 8. The first encoder 6 is coaxially connected to the rotor of the stepper motor 2 and is used to collect the position and speed information of the motor rotor; the second encoder 8 is coaxially connected to the reduction gear shaft 18 of the gear reduction mechanism and is used to collect the rotation angle information of the reduction gear shaft 18; the control circuit board 16 is electrically connected to the first encoder 6, the second encoder 8, and the drive module respectively, and the drive module is electrically connected to the stepper motor 2.

[0024] This invention enables dual encoders to work together, with the first encoder 6 responsible for current and speed feedback at the motor end and the second encoder 8 responsible for position feedback at the transmission end, thereby effectively compensating for transmission errors such as gear backlash, wear, and rack meshing deviation, and significantly improving the positioning accuracy and control stability of the valve core 14.

[0025] Further optimization of the design: guide grooves are provided on both sides of the rack 12, and guide pressure plates are correspondingly provided on the rack guide rail 5, with the guide pressure plates embedded in the guide grooves; one end of the rack 12 is connected to the valve core 14 through the ball head connector 13, and a preload spring 10 is provided on the ball head connector 13 through the retaining ring 17.

[0026] The above settings can prevent the rack 12 from shifting during movement, ensure the coaxiality of the valve core 14, and achieve eccentricity compensation through the ball joint 13. The preload spring 10 presses the ball head into the spherical groove of the rack 12, eliminating transmission gaps and further improving transmission accuracy and smoothness.

[0027] To further optimize the scheme, the control circuit board 16 adopts a microcontroller with integrated FOC control algorithm, which is used to receive feedback signals from the first encoder 6 and the second encoder 8, output control commands to the drive module, realize the field orientation control of the stepper motor 2, and form a three-closed-loop control of current loop, speed loop and position loop.

[0028] The above settings enable precise decoupling control of the stepper motor's current, reducing torque ripple and making the motor run more smoothly. At the same time, the three-loop control can adjust the control parameters in real time according to load changes, improving the system's dynamic response and anti-interference capabilities.

[0029] Further optimization of the scheme: the first encoder 6 is used to provide the position and speed feedback of the motor rotor to the control circuit board 16 to realize current closed-loop control and speed closed-loop control; the second encoder 8 is used to provide the rotation angle feedback of the reduction gear shaft 18 to the control circuit board 16 to calculate the actual position of the rack 12 and the valve core 14 to realize position closed-loop control.

[0030] The above settings can avoid the feedback delay and adjustment lag caused by a single encoder handling two tasks. The first encoder 6 focuses on the high-frequency feedback of the current loop to ensure stable motor torque output, while the second encoder 8 focuses on the real-time feedback of the position loop to compensate for transmission errors and ensure that the valve core 14 accurately reaches the target position.

[0031] The scheme is further optimized by incorporating a protection circuit in the drive module. This protection circuit includes an overcurrent protection circuit, an overtemperature protection circuit, and a short-circuit protection circuit. It is used to automatically cut off the drive signal and send a fault signal to the control circuit board 16 when the stepper motor 2 malfunctions.

[0032] The above settings can protect the stepper motor 2 and the controller from damage, while the control circuit board 16 can promptly detect fault conditions and take corresponding measures, thereby improving the safety and reliability of the entire device.

[0033] The scheme is further optimized. The gear reduction mechanism includes a motor gear 3 and a double gear 11. The motor gear 3 is fixedly connected to the output shaft of the stepper motor 2 through the motor gear shaft 19. The large gear of the double gear 11 meshes with the motor gear 3, and the small gear of the double gear 11 meshes with the rack 12. The second encoder 8 is fixedly installed at one end of the reduction gear shaft 18 of the double gear 11.

[0034] The above settings enable the stepper motor 2 to reduce speed and increase torque, while the second encoder 8 can directly acquire the rotation angle of the reduction gear shaft 18 and accurately calculate the actual positions of the rack 12 and valve core 14 based on the gear reduction ratio and the module of the rack 12, providing precise feedback for position closed-loop control.

[0035] In a further optimized scheme, both the first encoder 6 and the second encoder 8 are absolute encoders. The first encoder 6 is connected to the encoder interface of the control circuit board 16 via a differential signal line, and the second encoder 8 is connected to another encoder interface of the control circuit board 16 via a differential signal line.

[0036] The above settings allow the position information to be retained even after a power outage, eliminating the need to reset to zero every time power is restored. At the same time, the differential signal transmission method has strong anti-interference capabilities, ensuring the accuracy and stability of the feedback signal.

[0037] Further optimization of the scheme also includes a current acquisition unit, which is connected to the phase winding of the stepper motor 2 and electrically connected to the ADC port of the control circuit board 16, for real-time acquisition of the phase current signal of the stepper motor 2 and feedback to the control circuit board 16.

[0038] The above settings enable closed-loop current control, dynamically adjusting the phase current of the stepper motor 2 according to the load of the valve core 14, avoiding the motor from maintaining a high current under light load or stationary conditions, reducing power loss and improving energy efficiency.

[0039] The scheme is further optimized so that the control circuit board 16 is configured to automatically switch to single encoder control mode when either the first encoder 6 or the second encoder 8 fails, and continue to realize closed-loop control using the normally working encoder.

[0040] The above settings enable dual encoder redundancy backup. When one encoder fails, the device can still continue to work, avoiding system shutdown due to encoder failure and improving system reliability and fault tolerance.

[0041] Further optimization of the scheme: the meshing clearance between the motor gear 3 and the large gear of the double gear 11 is 0.01-0.03mm, and the reduction gear shaft 18 of the double gear 11 is rotatably connected to the housing 1 through a deep groove ball bearing.

[0042] The present invention can reduce backlash error and improve transmission accuracy through the above-mentioned settings. At the same time, the deep groove ball bearing reduces rotational friction, ensures smooth transmission, and extends the service life of the device.

[0043] The stepper motor driven hydraulic valve core device with dual encoder FOC provided by this invention has the following overall implementation process: First, start-up preparation is performed by connecting the device to an external power supply. The control circuit board 16, drive module, first encoder 6, and second encoder 8 are initialized. The second encoder 8 collects the rotation angle of the current reduction gear shaft 18, calculates the initial position of the valve core 14, and feeds back the initial position signal to the control circuit board 16. The control circuit board 16 records the initial position of the valve core 14, completing the initialization. Then, external control commands (such as the target position and movement speed of the valve core 14) are received. The control circuit board 16 calculates the required rotation angle, speed, and target current value of the stepper motor 2 based on the difference between the initial position and the target position of the valve core 14. Next, the FOC three-loop control and feedback regulation stage begins: In the current closed-loop control, the first encoder 6 collects the position and speed information of the stepper motor 2 rotor in real time and feeds it back to the control circuit board 16. The current acquisition unit collects the current signal of the two-phase winding of the stepper motor in real time and feeds it back to the control circuit board 16. The control circuit board 16 achieves precise decoupling control of the motor current through Park and Clark transformations to ensure stable motor torque output. In the speed closed-loop control, the control circuit board 16 compares the motor speed information fed back by the first encoder 6 with the target speed and adjusts the output current through the speed regulator to control the stepper motor. Stepper motor 2's rotational speed stabilizes at the target speed. In position closed-loop control, the second encoder 8 collects the rotation angle of the reduction gear shaft 18 in real time. Based on the gear reduction ratio and the module of rack 12, it calculates the actual positions of rack 12 and valve core 14 and feeds this information back to control circuit board 16. Control circuit board 16 compares the actual position of valve core 14 with the target position. If there is a deviation, it adjusts the control parameters of the speed loop and current loop to drive stepper motor 2 to rotate. This rotation drives double gear 11 through motor gear 3. The pinion of double gear 11 drives rack 12, and rack 12 pushes valve core 14 to move through ball joint 13 until valve core 14 reaches the target position. During operation, the protection circuit built into the drive module monitors the current and temperature of stepper motor 2 in real time. If an overcurrent, overtemperature, or short circuit fault occurs, the drive signal is immediately cut off and a fault signal is sent to control circuit board 16. If either the first encoder 6 or the second encoder 8 malfunctions, control circuit board 16 automatically switches to single encoder control mode and continues to achieve closed-loop control using the normally functioning encoder. When an external control command issues a stop signal, the control circuit board 16 controls the stepper motor 2 to decelerate and stop, and the second encoder 8 collects the final position of the valve core 14 and feeds it back to the control circuit board 16 to complete the stop process.

[0044] The present invention provides a stepper motor driven hydraulic valve core device employing dual encoder FOC. Firstly, through the collaborative operation of the two encoders, the first encoder 6 is responsible for current and speed closed-loop control, ensuring stable motor torque output. The second encoder 8 directly collects motion information from the transmission links to achieve position closed-loop control, effectively compensating for transmission errors such as gear backlash, wear, and rack meshing deviation. This solves the problem of accumulated deviation between the motor end position and the actual valve core position in existing technologies, improving positioning accuracy from ±0.05mm to ±0.01mm, meeting the requirements for high-precision valve core control. Secondly, the FOC control algorithm achieves precise decoupling control of the motor current through Park and Clark transformations, reducing torque pulsation. Combined with the preload spring 10, this alleviates transmission shock, making the stepper motor 2 run more smoothly and reducing vibration amplitude by 30%. The noise is reduced by more than 25%, preventing valve core 14 from jamming or vibrating, thus improving the system's operational stability. Furthermore, the current closed-loop control dynamically adjusts the motor phase current according to the valve core 14 load, preventing the stepper motor 2 from maintaining high current under light load or stationary conditions, reducing energy loss and improving energy efficiency by more than 20%. In addition, the drive module incorporates overcurrent, overtemperature, and short-circuit protection circuits, dual encoder redundancy switching, and an optimized mechanical structure, all contributing to the device's high reliability and long service life. Finally, the device's mechanical structure and control logic are simple, with all components being standardized parts, facilitating processing, assembly, and maintenance. The gear reduction ratio, rack 12 length, and stepper motor 2 parameters can be adjusted according to different valve core 14 specifications and stroke requirements, making it suitable for various fluid control equipment and hydraulic systems requiring high-precision valve core 14 drive.

[0045] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A stepper motor driven hydraulic valve core device employing dual encoder FOC, characterized in that, Includes a stepper motor (2) and a speed reducer (4) disposed in the housing (1). The speed reducer (4) is equipped with a gear reduction mechanism, a rack guide rail (5) and a rack (12). The rack (12) is connected to the valve core (14) in the valve body (15). It also includes a control circuit board (16), a drive module, a first encoder (6) and a second encoder (8); the housing (1) is equipped with a first encoder magnet (7) and a second encoder magnet (9) at positions corresponding to the first encoder (6) and the second encoder (8), respectively. The first encoder (6) is coaxially connected to the rotor of the stepper motor (2) and is used to collect the position and speed information of the motor rotor. The second encoder (8) is coaxially connected to the reduction gear shaft (18) of the gear reduction mechanism and is used to collect the rotation angle information of the reduction gear shaft (18). The control circuit board (16) is electrically connected to the first encoder (6), the second encoder (8) and the drive module, respectively. The drive module is electrically connected to the stepper motor (2).

2. The stepper motor driven hydraulic valve core device with dual encoder FOC as described in claim 1, characterized in that, The rack (12) has guide grooves on both sides, and a guide pressure plate is provided on the rack guide rail (5) accordingly. The guide pressure plate is embedded in the guide groove. One end of the rack (12) is connected to the valve core (14) through a ball head handle (13). A pre-tightening spring (10) is provided on the ball head handle (13) through a retaining ring (17).

3. The stepper motor driven hydraulic valve core device with dual encoder FOC as described in claim 1, characterized in that, The control circuit board (16) adopts a microcontroller with integrated FOC control algorithm, which is used to receive feedback signals from the first encoder (6) and the second encoder (8), output control commands to the drive module, realize the magnetic field orientation control of the stepper motor (2), and form a three-closed-loop control of current loop, speed loop and position loop.

4. The stepper motor driven hydraulic valve core device with dual encoder FOC as described in claim 3, characterized in that, The first encoder (6) is used to provide the position and speed feedback of the motor rotor to the control circuit board (16) to realize current closed-loop control and speed closed-loop control; the second encoder (8) is used to provide the rotation angle feedback of the reduction gear shaft (18) to the control circuit board (16) to calculate the actual position of the rack (12) and the valve core (14) to realize position closed-loop control.

5. The stepper motor driven hydraulic valve core device with dual encoder FOC as described in claim 1, characterized in that, The drive module has a built-in protection circuit, which includes an overcurrent protection circuit, an overtemperature protection circuit and a short circuit protection circuit. It is used to automatically cut off the drive signal and send a fault signal to the control circuit board (16) when the stepper motor (2) fails.

6. The stepper motor driven hydraulic valve core device with dual encoder FOC as described in claim 1, characterized in that, The gear reduction mechanism includes a motor gear (3) and a double gear (11). The motor gear (3) is fixedly connected to the output shaft of the stepper motor (2). The large gear of the double gear (11) meshes with the motor gear (3), and the small gear of the double gear (11) meshes with the rack (12). The second encoder (8) is fixedly installed at one end of the reduction gear shaft (18) of the double gear (11).

7. The stepper motor driven hydraulic valve core device with dual encoder FOC as described in claim 1, characterized in that, Both the first encoder (6) and the second encoder (8) are absolute encoders. The first encoder (6) is connected to the encoder interface of the control circuit board (16) via a differential signal line, and the second encoder (8) is connected to another encoder interface of the control circuit board (16) via a differential signal line.

8. The stepper motor driven hydraulic valve core device with dual encoder FOC as described in claim 1, characterized in that, It also includes a current acquisition unit, which is connected to the phase winding of the stepper motor (2) and electrically connected to the ADC port of the control circuit board (16) for real-time acquisition of the phase current signal of the stepper motor (2) and feedback to the control circuit board (16).

9. The stepper motor driven hydraulic valve core device with dual encoder FOC as described in claim 1, characterized in that, The control circuit board (16) is configured to automatically switch to single encoder control mode when either the first encoder (6) or the second encoder (8) fails, and continue to implement closed-loop control using the normally functioning encoder.

10. The stepper motor driven hydraulic valve core device with dual encoder FOC according to claim 6, characterized in that, The meshing clearance between the motor gear (3) and the large gear of the double gear (11) is 0.01-0.03 mm, and the reduction gear shaft (18) of the double gear (11) is rotatably connected to the housing (1) through a deep groove ball bearing.

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