Constant force floating control fan blade surface polishing device and method thereof

Abstract

The present application relates to the field of mechanical processing and automation equipment, in particular to a constant force floating control fan blade surface polishing equipment and method thereof; it contains base, low friction air cylinder, cross communication hydraulic capsule group, main shaft function part containing magnetic rheological elastomer shear pad and controller; the equipment adopts series connection structure of air cylinder and shear pad, and carries out joint control in combination with motor current high frequency spectrum characteristics and back pressure cavity micro pressure pulse derivative; its core is to abandon the external force sensor which is easy to be disturbed, accurately evaluates the contact resistance and tangential disturbance through feature extraction, so as to dynamically adjust the macroscopic thrust of air cylinder and the stiffness of shear pad; the present application effectively resolves the physical contradiction of low frequency normal compliance and high frequency tangential vibration suppression, and avoids the main shaft vibration phenomenon.

Description

Technical Field

[0001] This invention relates to the field of machining and automation equipment, specifically to a constant force floating control wind turbine blade surface grinding device and method. Background Technology

[0002] In the grinding process of wind turbine blades, large blades have the characteristics of free-form surfaces with variable cross-sections. During the grinding process, the grinding equipment is usually subjected to the coupling effect of contact resistance changes caused by abrupt changes in normal curvature and tangential friction vibration caused by surface hard points. To perform constant force grinding on these complex curved surfaces, existing solutions generally adopt traditional simple cylinder or robot active motion control architecture, that is, directly measuring the three-dimensional contact force through end-effector multi-dimensional force sensors and then feeding it back to the servo actuator for thrust and attitude adjustment. Although this solution has a certain processing capability under the condition of smooth curved surfaces, it relies on external force sensors that are susceptible to vibration interference, and traditional sealed cylinders have static friction interference effects, resulting in high system response delay and large fluctuations in normal contact force. At the same time, a single rigid or flexible mechanical structure is difficult to decouple the contradictory requirements of low-frequency normal compliance and high-frequency tangential vibration suppression. When encountering tangential impact, it is easy to cause spindle chatter, making it difficult to support the smooth processing of complex curved surfaces that meet the preset fit threshold.

[0003] Therefore, how to improve the timeliness and adaptability of normal compliance and tangential vibration suppression of grinding equipment when facing multidimensional disturbances without relying on direct interface mechanical measurements has become an urgent technical problem to be solved. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides a constant force floating control wind turbine blade surface grinding device and method. Specifically, the technical solution of the present invention is as follows:

[0005] A constant-force floating control wind turbine blade surface grinding device, comprising:

[0006] Base;

[0007] A low-friction cylinder is located at the center of the base, and has a back pressure chamber inside. The end of its piston rod is connected to a ball joint support.

[0008] The hydraulic bladder group surrounds the periphery of the ball joint support body. The first hydraulic bladder and the opposite third hydraulic bladder, the second hydraulic bladder and the opposite fourth hydraulic bladder are arranged in a cross shape and are connected through the first cross flow channel and the second cross flow channel in the ball joint support body, respectively.

[0009] The grinding spindle functional unit is supported by the top of the hydraulic bladder group. The bottom center of the spindle flange is movably connected to the upper spherical surface of the ball joint support through a ball joint pair. The magnetorheological elastomer shear pad is connected to the top surface of the spindle flange. The bottom flange of the spindle motor housing is connected to the top surface of the magnetorheological elastomer shear pad. The output shaft of the spindle motor is vertically connected to the grinding disc.

[0010] The excitation coil is fixedly wrapped around the outer periphery of the magnetorheological elastomer shear pad;

[0011] A pressure sensor is installed on the back pressure chamber of the low-friction cylinder;

[0012] A current sensor is mounted on the spindle motor and connected in series in the stator power supply circuit of the spindle motor;

[0013] The controller connects to and controls the low-friction cylinder, the spindle motor, and the excitation coil; both the pressure sensor and the current sensor are connected to the controller.

[0014] In one embodiment, the low-friction cylinder is fixedly connected to the base by bolts, and the piston rod end of the low-friction cylinder is threadedly connected to the lower end of the ball joint support.

[0015] In one embodiment, the first hydraulic bladder, the third hydraulic bladder, and the first intersecting flow channel are filled with hydraulic oil, and the second hydraulic bladder, the fourth hydraulic bladder, and the second intersecting flow channel are filled with hydraulic oil.

[0016] In one embodiment, the magnetorheological elastomer shear pad has a circular structure, and the bottom flange of the main spindle motor housing is fixedly connected to the top surface of the magnetorheological elastomer shear pad by bolts.

[0017] In one embodiment, the grinding device further includes an electro-proportional valve disposed in the low-friction cylinder, the electro-proportional valve being connected to the controller.

[0018] In one embodiment, the controller is pre-set with a variable stiffness compensation model, which is configured to receive the high-frequency spectrum characteristics of the stator current of the spindle motor, the effective value of the fundamental wave of the stator current, and the micro-pressure pulse derivative of the back pressure chamber of the low-friction cylinder, extracted from the signals of the current sensor and the pressure sensor.

[0019] The variable stiffness compensation model is configured to generate a high damping demand signal based on the high frequency spectrum characteristics of the stator current and output it to the excitation coil, and to generate a low frequency thrust deviation signal based on the micro-pressure pulse derivative and the effective value of the fundamental wave of the stator current of the spindle motor and output it to the low friction cylinder.

[0020] In one embodiment, the free yaw angle of the spindle flange relative to the ball joint support is ±2° to ±12°.

[0021] A control method for a constant force floating control wind turbine blade surface grinding device includes:

[0022] S1. Control the low-friction cylinder to output macroscopic thrust, and push the ball joint support and the main shaft flange close to the surface of the fan blades;

[0023] S2. Control the spindle motor to drive the grinding disc to rotate and cut;

[0024] S3. Extract in real time the high-frequency spectrum characteristics of the stator current of the main spindle motor, the effective value of the fundamental wave of the stator current, and the micro-pressure pulse derivative of the back pressure chamber of the low-friction cylinder.

[0025] S4. Adjust the excitation coil current and the macroscopic thrust of the low-friction cylinder according to the high-frequency spectrum characteristics of the stator current, the fundamental effective value of the stator current, and the micro-pressure pulse derivative; wherein, when a high-frequency harmonic peak with an amplitude greater than a first preset threshold appears in the high-frequency spectrum characteristics of the stator current and the micro-pressure pulse derivative is within a preset zero-value neighborhood, control the excitation coil current to increase; when the fundamental effective value of the stator current increases monotonically within multiple consecutive preset time windows and the micro-pressure pulse derivative is greater than a second preset threshold, control the low-friction cylinder to reduce the macroscopic thrust and control the excitation coil current to decrease; in other cases, when the high-frequency spectrum characteristics of the stator current do not show a high-frequency harmonic peak exceeding the first preset threshold and the micro-pressure pulse derivative is less than a third preset threshold, control the low-friction cylinder to restore to the basic thrust and maintain the existing excitation level; otherwise, maintain the current thrust and excitation coil current output by the low-friction cylinder.

[0026] S5. Repeat steps S1 to S4 above.

[0027] In one embodiment, the constant force floating control wind turbine blade surface polishing equipment further includes an electro-proportional valve connected to the controller;

[0028] The step of controlling the low-friction cylinder to reduce the macroscopic thrust in S4 includes: generating a low-frequency thrust deviation signal based on the micro-pressure pulse derivative and the effective value of the stator current fundamental wave, and sending the low-frequency thrust deviation signal to the electro-proportional valve to reduce the macroscopic thrust of the low-friction cylinder.

[0029] In one embodiment, the controller is pre-configured with a variable stiffness compensation model;

[0030] The step of controlling the increase of the excitation coil current in S4 includes: controlling the variable stiffness compensation model to generate a high damping demand signal based on the high frequency spectrum characteristics of the stator current, and converting the high damping demand signal into a pulse width modulation signal and sending it to the excitation coil.

[0031] The step of controlling the reduction of the excitation coil current in S4 includes: the controller sending a pulse width modulation signal to reduce the excitation coil current.

[0032] The present invention has the following beneficial effects:

[0033] 1. This invention utilizes a series structure of a low-friction cylinder and a magnetorheological elastomer shear pad, combined with the high-frequency spectrum characteristics of the spindle motor stator current extracted by a variable stiffness compensation model and the derivative of the micro-pressure pulse in the back pressure cavity for joint control. This design can accurately assess contact resistance and tangential disturbance without relying on easily interfered external force sensors, thereby dynamically adjusting the macroscopic thrust of the cylinder and the stiffness of the shear pad, effectively resolving the contradiction between low-frequency normal compliance and high-frequency tangential vibration suppression, and avoiding spindle chatter.

[0034] 2. This invention utilizes a group of hydraulic bladders and cross-flow channels arranged in a cross shape around the ball joint support, in conjunction with the ball joint pair at the bottom of the main shaft flange, to construct a purely fluid-driven attitude correction mechanism. When the equipment is affected by the curved surface and sways, squeezing one side of the hydraulic bladder, the incompressible hydraulic oil inside is automatically pressed into the opposite side hydraulic bladder, causing it to expand and generate a reverse counteracting torque to passively straighten the main shaft axis. This structure does not require additional attitude servo components, ensuring smooth processing of free-form surfaces that meet the preset fit threshold. Attached Figure Description

[0035] The following drawings, illustrating embodiments of this application, are incorporated herein by reference and are used to understand this application. The drawings illustrate embodiments of this application and their descriptions, serving to explain the principles of this application. In the drawings,

[0036] Figure 1 This is a schematic diagram of the overall external structure of the device;

[0037] Figure 2 This is a schematic diagram of the hydraulic bladder group and its connection structure;

[0038] Figure 3 This is a flowchart of the method of the present invention.

[0039] In the diagram: 1. Base; 200. Low-friction cylinder; 210. Piston rod; 300. Ball joint support; 310. First crossflow channel; 320. Second crossflow channel; 400. Hydraulic bladder group; 410. First hydraulic bladder; 420. Second hydraulic bladder; 430. Third hydraulic bladder; 440. Fourth hydraulic bladder; 500. Grinding spindle functional unit; 510. Spindle flange; 520. Ball joint pair; 530. Magnetorheological elastomer shear pad; 540. Spindle motor; 541. Bottom flange of the housing; 542. Output shaft; 550. Grinding disc; 600. Excitation coil; 700. Electro-proportional valve. Detailed Implementation

[0040] In the following description, numerous specific details are set forth to provide a more thorough understanding of this application. However, it will be apparent to those skilled in the art that embodiments of this application may be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described to avoid confusion with embodiments of this application.

[0041] Example 1:

[0042] A constant-force floating control wind turbine blade surface grinding device, such as... Figure 1 As shown, it includes:

[0043] Base 1;

[0044] The low-friction cylinder 200 is located at the center of the base 1. It has a back pressure chamber inside, and the end of its piston rod 210 is connected to the ball joint support 300.

[0045] like Figure 2 As shown, the hydraulic bladder group 400 surrounds the ball joint support 300. The first hydraulic bladder 410 and the opposite third hydraulic bladder 430, the second hydraulic bladder 420 and the opposite fourth hydraulic bladder 440 are arranged in a cross shape and are connected through the first cross flow channel 310 and the second cross flow channel 320 in the ball joint support 300, respectively.

[0046] The grinding spindle functional unit 500 is supported at the top by the hydraulic bladder group 400. The center bottom surface of its spindle flange 510 is movably connected to the upper spherical surface of the ball joint support 300 through the ball joint pair 520. The magnetorheological elastomer shear pad 530 is connected to the top surface of the spindle flange 510. The bottom flange 541 of the housing of the spindle motor 540 is connected to the top surface of the magnetorheological elastomer shear pad 530. The output shaft 542 of the spindle motor 540 is vertically connected to the grinding disc 550.

[0047] The excitation coil 600 is fixedly wrapped around the outer periphery of the magnetorheological elastomer shear pad 530;

[0048] A pressure sensor is installed on the back pressure chamber of the low-friction cylinder 200;

[0049] A current sensor is mounted on the spindle motor 540 and connected in series in the stator power supply circuit of the spindle motor 540.

[0050] The controller connects to and controls the low-friction cylinder 200, the spindle motor 540, and the excitation coil 600; both the pressure sensor and the current sensor are connected to the controller.

[0051] The constant force floating control wind turbine blade surface grinding equipment in this embodiment is used for surface finishing of large wind turbine blades with variable cross-section free-form surfaces. The base 1 adopts a steel or aluminum alloy frame structure, with a length that can be set to 500mm to 1200mm and a width that can be set to 300mm to 800mm. It is used to support the low friction cylinder 200, the ball joint support 300, and the grinding spindle functional part 500. The low friction cylinder 200 is used to provide normal foundation thrust. Its cylinder diameter can be set to 40mm to 100mm, and its rated working pressure can be set to 0.4MPa to 0.8MPa. The piston rod 210 axis is basically coaxial with the rotation axis of the grinding disc 550 to reduce additional off-center load.

[0052] The low-friction cylinder 200 is divided into a rodless chamber and a rod chamber by a piston. The rodless chamber serves as the main intake chamber and is connected to the external air supply circuit to provide normal basic thrust. The rod chamber serves as the back pressure chamber, where the gas inside is forced to compress to generate back pressure to characterize the change in normal contact resistance. A pressure sensor for sampling back pressure data is installed on the back pressure chamber.

[0053] The ball joint support 300 is positioned above the end of the piston rod 210, serving both as an attitude support for the main shaft flange 510 and as a load-bearing component for the first cross flow channel 310 and the second cross flow channel 320. The hydraulic bladder group 400 is evenly distributed around the ball joint support 300, with the four hydraulic bladders arranged in a cross shape on the plane projection, so that any tilt in any direction can be decomposed into volume transfer between corresponding diagonal hydraulic bladders. The main shaft flange 510 is supported by the top of the hydraulic bladder group 400, and the ball joint pair 520 between the main shaft flange 510 and the ball joint support 300 allows the main shaft flange 510 to deflect at a small angle relative to the base 1 to accommodate changes in the normal vector of the blade surface.

[0054] A magnetorheological elastomer shear pad 530 is located between the spindle flange 510 and the spindle motor 540. Its material consists of a rubber matrix and magnetic sensitive particles. When the external excitation coil 600 is energized, it changes the apparent shear modulus and damping coefficient of the shear pad. The spindle motor 540 can be a variable frequency motor with a rated power of 1.5kW to 5.5kW. The output shaft 542 is connected downward to the grinding disc 550. The diameter of the grinding disc 550 can be set to 100mm to 300mm, and the speed can be set to 1000r / min to 6000r / min.

[0055] The excitation coil 600 has a thermistor mounted on its surface that is electrically connected to the controller. The controller integrates a drive power supply voltage detection circuit. The controller can be an industrial controller, a programmable logic controller, or an embedded control unit. It is electrically connected to the low-friction cylinder 200, the spindle motor 540, and the excitation coil 600, respectively, to perform thrust adjustment, speed control, and excitation adjustment.

[0056] In this structure, the low-friction cylinder 200 is responsible for macroscopic normal following, the magnetorheological elastomer shear pad 530 is responsible for stiffness and damping adjustment under tangential disturbance, and the hydraulic bladder group 400 is responsible for attitude self-soothing caused by normal deflection of the contact surface. Therefore, the same device has three capabilities: normal compliance, tangential vibration suppression and axis alignment.

[0057] The low-friction cylinder 200 is fixedly connected to the base 1 by bolts, and the end of the piston rod 210 of the low-friction cylinder 200 is connected to the lower end of the ball joint support 300 by thread.

[0058] In this embodiment, the low-friction cylinder 200 is fixed to the central mounting plate of the base 1 by four high-strength bolts. The bolt specifications can be M8 to M16, and the flatness of the mounting plate is controlled within 0.05mm per 100mm to ensure the consistency between the cylinder axis and the center line of the whole machine. The reason for using bolt fixing is that the cylinder will be subjected to periodic normal loads and high-frequency vibrations within a preset amplitude range during the grinding process. Bolt connection facilitates disassembly and maintenance, and facilitates the correction of installation accuracy by shims or adjusting blocks.

[0059] The piston rod 210 has an external thread at its end, and the ball joint support 300 has a corresponding internal thread at its lower end. The two are connected by threads to form an interchangeable assembly relationship. The threads can be of specifications from M12×1.75 to M24×2.0, and thread locking agent or lock nut is provided to prevent loosening. The thread connection length can be set to 1.2 to 2 times the nominal diameter to ensure the strength of the force transmission section.

[0060] This connection method allows the axial thrust output by the low-friction cylinder 200 to be directly transmitted to the ball joint support 300, while retaining the convenience of disassembly and replacement. If the equipment stroke is adjusted or a ball joint support 300 with different stiffness is replaced according to the blade specifications, the threaded connection can reduce the amount of work required for the overall machine modification. The low-friction cylinder 200 adopts a low-friction sealing structure, and its static friction can be controlled to be below 3% of the rated thrust, so that the piston rod 210 can still respond to the undulation of the blade surface under small displacement, thereby meeting the basic requirements of constant force contact.

[0061] Specifically, the low-friction sealing structure includes a gap sealing ring disposed on the outer wall of the cylinder piston and an air bearing guide sleeve located at the cylinder end cover. By forming a micron-level air film support between the piston and the cylinder and between the piston rod 210 and the end cover, the static dry friction locking effect caused by traditional rubber seals is avoided.

[0062] The first hydraulic bladder 410, the third hydraulic bladder 430 and the first cross flow channel 310 are filled with hydraulic oil, and the second hydraulic bladder 420, the fourth hydraulic bladder 440 and the second cross flow channel 320 are filled with hydraulic oil.

[0063] In this embodiment, the first hydraulic bladder 410, the third hydraulic bladder 430, and the first cross-flow channel 310 constitute a set of diagonally coupled hydraulic support units, and the second hydraulic bladder 420, the fourth hydraulic bladder 440, and the second cross-flow channel 320 constitute another set of diagonally coupled hydraulic support units. The hydraulic bladders can be made of oil-resistant rubber or polyurethane elastic materials, and the effective volume of a single hydraulic bladder can be set to 5 mL to 50 mL, and the wall thickness can be set to 1 mm to 5 mm. The first cross-flow channel 310 and the second cross-flow channel 320 are both opened inside the ball joint support 300, and the channel diameter can be set to 1 mm to 6 mm, and the channel length is determined according to the shape of the ball joint support 300.

[0064] Each hydraulic bladder and corresponding flow channel is filled with incompressible hydraulic oil. The hydraulic oil can be mineral oil or synthetic ester hydraulic medium with a kinematic viscosity of 15 mm² / s to 68 mm² / s. During assembly, venting is performed to ensure that the residual bubble volume fraction in the system is less than 2% to reduce compression hysteresis. To avoid the failure of attitude correction logic caused by oil mixing in the cross circuit, the first cross flow channel 310 and the second cross flow channel 320 are at different horizontal heights inside the ball joint support 300. They are spatially intersecting in a non-planar manner and are not connected to each other to ensure that the two sets of diagonally coupled hydraulic support units operate completely independently in terms of hydrodynamics.

[0065] The purpose of using incompressible hydraulic oil is to convert the local compression displacement caused by the tilt of the main spindle flange 510 into the synchronous volume expansion of the diagonal hydraulic bladder, thereby forming a predictable reverse support torque. When the main spindle flange 510 is biased towards the first hydraulic bladder 410, the first hydraulic bladder 410 is compressed, and the hydraulic oil is transferred to the third hydraulic bladder 430 through the first cross flow channel 310. The volume of the third hydraulic bladder 430 increases and lifts the area on the opposite side of the main spindle flange 510, thereby reducing the spindle tilt angle.

[0066] The second hydraulic bladder 420 and the fourth hydraulic bladder 440 perform the same mechanism in another orthogonal direction, so the device has passive attitude correction capability in two mutually perpendicular directions; this embodiment does not require additional angle sensors and attitude servo actuators, and torque compensation corresponding to the deflection direction can be obtained by means of liquid volume transfer alone.

[0067] The magnetorheological elastomer shear pad 530 has a ring-shaped structure, and the bottom flange 541 of the housing of the main spindle motor 540 is fixedly connected to the top surface of the magnetorheological elastomer shear pad 530 by bolts.

[0068] In this embodiment, the magnetorheological elastomer shear pad 530 adopts a ring-shaped structure, with an outer diameter that can be set to 120mm to 260mm, an inner diameter that can be set to 40mm to 120mm, and a thickness that can be set to 5mm to 20mm. The ring-shaped structure is used to bypass the output shaft 542 channel of the main spindle motor 540 and to form a uniformly distributed shear force area in the circumference. The magnetorheological elastomer shear pad 530 is composed of a rubber matrix and soft magnetic particles with a mass fraction of 30% to 75%. The matrix can be silicone rubber, natural rubber, or nitrile rubber, and the soft magnetic particles can be carbonyl iron powder or iron-nickel alloy powder. The average particle size can be set to 1μm to 100μm.

[0069] The bottom flange 541 of the main spindle motor 540 housing is fixed to the top surface of the magnetorheological elastomer shear pad 530 by six or eight bolts, with the bolts distributed circumferentially to ensure uniform clamping. The bottom surface of the magnetorheological elastomer shear pad 530 and the top surface of the main spindle flange 510 can be fixed by adhesive bonding, mechanical pressing, or a combination of both. The so-called series structure of pneumatic power transmission and magnetorheological intervention means that the normal thrust output by the low-friction cylinder 200 must pass through the magnetorheological elastomer shear pad 530 after passing through the ball joint support 300 and the main spindle flange 510 before being transmitted to the main spindle motor 540 and the grinding disc 550. Therefore, the change in shear pad stiffness caused by the excitation coil 600 will directly affect the transmission mode of the thrust.

[0070] When the excitation coil 600 is supplied with a current greater than the preset current threshold, the apparent shear modulus of the magnetorheological elastomer shear pad 530 increases, the micro-displacement of the spindle motor 540 relative to the spindle flange 510 decreases, and the equipment exhibits a preset high level of tangential stiffness. When the current in the excitation coil 600 decreases, the damping energy dissipation effect of the magnetorheological elastomer shear pad 530 is enhanced, which can absorb high-frequency impacts at the contact interface. The key to this structure is that the stiffness adjustment does not depend on additional mechanical clutches or independent servo axes, but is directly applied to the force transmission path through the controlled material layer.

[0071] The grinding equipment also includes an electro-proportional valve 700 disposed in the low-friction cylinder 200, and the electro-proportional valve 700 is connected to the controller;

[0072] In this embodiment, the grinding equipment is equipped with an electro-proportional valve 700 at the air inlet and / or exhaust end of the low-friction cylinder 200. The electro-proportional valve 700 is electrically connected to the controller and is used to adjust the cylinder chamber pressure according to the control signal, thereby adjusting the output thrust of the piston rod 210. The electro-proportional valve 700 can be a flow-type proportional valve or a pressure-type proportional valve, and the control input can be a 0V to 10V analog voltage signal, a 4mA to 20mA current signal, or a pulse width modulation signal.

[0073] To adapt to continuous load changes during the grinding process, the rated flow rate of the proportional valve can be set from 100L / min to 1000L / min, and the control response time can be set from 10ms to 100ms. The controller outputs a low-frequency thrust deviation signal to the electro-proportional valve 700 based on the current characteristics of the spindle motor 540 and changes in back pressure. The proportional valve then adjusts the working pressure of the low-friction cylinder 200 accordingly. For example, when a reduction in macroscopic thrust is required, the controller lowers the output pressure setpoint of the proportional valve, and the cylinder thrust is adjusted accordingly. The relationship declined, among which, For cylinder thrust, For cylinder pressure, The effective pressure-bearing area;

[0074] When the basic thrust needs to be restored, the controller adjusts the proportional valve control value back to the predetermined value. The purpose of using the electric proportional valve 700 is to make the thrust of the low-friction cylinder 200 continuously adjustable, rather than just switching between on and off states. This can be combined with the rapid stiffness change of the magnetorheological elastomer shear pad 530 to respectively undertake the correction of normal force at the low-frequency scale and the vibration suppression at the high-frequency scale.

[0075] The controller has a pre-set variable stiffness compensation model, which is configured to receive the high-frequency spectrum characteristics of the stator current of the spindle motor 540, the effective value of the fundamental stator current, and the micro-pressure pulse derivative of the back pressure chamber of the low-friction cylinder 200, which are extracted based on the signals from the current sensor and the pressure sensor.

[0076] The variable stiffness compensation model is configured to generate a high damping demand signal based on the high frequency spectrum characteristics of the stator current and output it to the excitation coil 600, and generate a low frequency thrust deviation signal based on the micro-pressure pulse derivative and the effective value of the fundamental wave of the stator current of the spindle motor 540 and output it to the low friction cylinder 200.

[0077] In this embodiment, the controller has a pre-set variable stiffness compensation model, which is a set of calculation rules used to convert easily measurable electrical signals and fluid pressure signals into control quantities. The high-frequency spectrum characteristics of the stator current refer to the parameters such as high-frequency harmonic amplitude, energy ratio, bandwidth, and frequency position obtained by sampling, filtering, and spectrum analysis of the original waveform of the stator current of the spindle motor 540. The micro-pressure pulse derivative of the back pressure chamber refers to the first derivative of the pressure change of the back pressure chamber of the low-friction cylinder 200 with time, and the unit can be expressed as kilopascals per millisecond.

[0078] In practice, the 540-phase current of the spindle motor is acquired through a Hall current sensor or a shunt, and the sampling frequency can be set to 5kHz to 50kHz. After bandpass filtering, the peak value of the spectrum within the preset frequency band is extracted. The back pressure chamber of the low-friction cylinder 200 is sampled through a pressure sensor, and the sampling frequency can be set to 1kHz to 10kHz. The derivative of the micro-pressure pulse is obtained through numerical difference calculation. The variable stiffness compensation model can adopt a threshold judgment model, a lookup table model, or an analytical model containing empirical coefficients.

[0079] The purpose of the variable stiffness compensation model is to estimate and separate the change in normal contact resistance and tangential friction disturbance in real time when the grinding disc 550 is in contact with the variable cross section free surface of the blade, in the case that it is not possible to directly install force sensors to accurately measure the real three-dimensional cutting force at the contact interface, by using easily measurable motor current and cylinder back pressure signals, thereby dynamically providing the required normal compliance and tangential stiffness adjustment amount.

[0080] In terms of logical structure and data flow, the model contains two parallel sub-modules: the tangential disturbance evaluation sub-module receives the high-frequency spectrum characteristics of the stator current as input, and is used to calculate and output the high-damping demand signal; the normal load tracking sub-module receives the micro-pressure pulse derivative and the effective value of the fundamental wave of the stator current as input, and is used to calculate and output the low-frequency thrust deviation signal.

[0081] The final controller converts the outputs of these two modules into control commands for the excitation coil 600 and the electro-proportional valve 700, respectively. The model as a whole represents the dynamic physical coupling relationship in which tangential frictional vibration is directly reflected in the high-frequency torque and current fluctuations of the drive motor during the grinding and cutting process, while the change in normal contact force is transmitted through the mechanical structure and squeezes the gas in the back pressure chamber of the low-friction cylinder 200, causing back pressure micro-pulse fluctuations.

[0082] Taking the threshold determination model as an example, when the amplitude of the high-frequency harmonic exceeds the pre-calibrated threshold Ih and the derivative of the micro-pressure pulse is close to zero, the model determines that the tangential disturbance is dominant and outputs a command to increase the excitation current; when the effective value of the fundamental wave of the stator current continues to increase within the predetermined time window, and the derivative of the micro-pressure pulse is positive and exceeds the threshold Dp, the model determines that the normal contact resistance is increasing and outputs a joint command to reduce the cylinder thrust and reduce the excitation current.

[0083] If an analytical model containing empirical coefficients is adopted, its calculation rules can be structurally decomposed as follows: divide the collected high-frequency harmonic peak amplitude by the reference amplitude to obtain the dimensionless vibration intensity coefficient; divide the micro-pressure pulse derivative by the reference derivative value to obtain the dimensionless normal resistance variation coefficient; where the reference amplitude is the stator current high-frequency harmonic peak amplitude when the equipment is running under no-load at rated speed.

[0084] The reference derivative value is the average value of the back pressure pulse derivative when the equipment is extended normally under no-load under rated working pressure; by weighted summation, the vibration intensity coefficient is multiplied by the first empirical weight, and the normal resistance change coefficient is multiplied by the second empirical weight to obtain the comprehensive compensation index; according to the numerical range of the comprehensive compensation index, the corresponding high damping demand signal and low frequency thrust deviation signal are independently matched respectively.

[0085] For example, if the first empirical weight is set to 0.7 and the second empirical weight is set to 0.3, when the calculated comprehensive compensation index is greater than 1.5, the system determines that the current working condition is a high-risk tangential disturbance and directly outputs the highest level of high-damping demand signal. Through the above logic, the analytical model can quantify multi-dimensional features into a one-dimensional decision index without complex nonlinear formulas, which is convenient for controller programming.

[0086] The model does not directly measure the actual stress at the contact interface, but rather reconstructs the required normal compliance and tangential stiffness adjustment under grinding conditions by utilizing the correspondence between changes in spindle load and cylinder back pressure. The input, processing sequence, and output relationship of the variable stiffness compensation model can be implemented according to the following logic:

[0087] Step 1: Acquire the raw current signal of at least one phase of the spindle motor 540, and simultaneously acquire the raw pressure signal of the back pressure chamber of the low friction cylinder 200.

[0088] Step 2: The original current signal is subjected to DC component removal and bandpass filtering to obtain the high-frequency current component used to characterize the contact disturbance. At the same time, the original pressure signal is subjected to low-pass filtering and the difference between adjacent sampling points is calculated to obtain the derivative of the micro-pressure pulse in the back pressure cavity.

[0089] Step 3: Perform spectrum analysis on the high-frequency current component within the sliding time window, and extract the peak amplitude, peak frequency, and total energy percentage of the preset frequency band. The preset frequency band is preferably a frequency band that is more than 3 times higher than the fundamental frequency of the motor to avoid misjudging normal torque fluctuations as tangential impacts.

[0090] Step 4: The controller reads the trend of the fundamental effective value of the stator current and the sign and amplitude of the derivative of the micro-voltage pulse within the same time window; wherein, the time length of the sliding time window is set to cover the duration of at least 5 control cycles in order to filter out transient fluctuations caused by single high-frequency noise;

[0091] Step 5: Based on the preset criteria, output the high damping demand signal and the low frequency thrust deviation signal, and send them to the excitation coil 600 control module and the cylinder thrust adjustment module, respectively.

[0092] The specific high-frequency harmonic peak extraction operation is as follows: perform a fast Fourier transform on the high-frequency current component after bandpass filtering, calculate the amplitude of each frequency point in the preset frequency band, extract the maximum amplitude point as the high-frequency harmonic peak in the current sliding time window, and compare it with the pre-calibrated threshold Ih to trigger subsequent adjustment decisions; the pre-calibrated threshold Ih is the aforementioned first preset threshold, and the threshold Ih represents the discrimination boundary of the significance of tangential disturbance, and its physical meaning is the minimum identifiable amplitude of high-frequency contact impact in the stator current spectrum;

[0093] Ih is not set arbitrarily, but can be obtained by pre-sampling under three working conditions: no-load rotation, light-load grinding, and stable normal grinding. First, record the statistical upper limit of the high-frequency peak under normal stable working conditions, and then add 10% to 30% safety margin as Ih on the basis of the statistical upper limit to avoid mistaking the inherent harmonics of the motor or the sensor noise as tangential abnormal disturbance.

[0094] The threshold Dp is the aforementioned second preset threshold. Threshold Dp represents the discrimination boundary of the upward trend of normal contact load. Its physical meaning is that the rate of change of back pressure chamber pressure reaches the minimum level that requires intervention. Dp can be obtained by conducting a stepped contact test under a known thrust setting. That is, the range of change of micro-pressure pulse derivative during the process of the grinding disc 550 from light contact to pressing is recorded, and the boundary value between the average value of the stable contact rising segment and the upper limit of noise fluctuation is selected as Dp. The so-called micro-pressure pulse derivative is close to zero means that the derivative falls within the preset zero value neighborhood interval. The tolerance band can be set to ±0.5kPa / ms to ±5kPa / ms, which is used to characterize the normal contact state as basically stable.

[0095] The model does not directly output a single conclusion, but makes decisions layer by layer according to the state discrimination logic: when the high frequency peak value is greater than Ih and the micro-pressure pulse derivative is within the preset zero value neighborhood, it first determines that the normal load has not changed significantly, and then determines that the main disturbance comes from tangential friction and local jump, so it outputs an instruction to increase the excitation current; when the fundamental effective value increases monotonically in multiple consecutive time windows and the micro-pressure pulse derivative is greater than Dp, it first determines that the overall contact resistance is rising, and then determines that the normal pressing trend is strengthening, so it outputs a joint instruction to reduce the cylinder thrust and reduce the excitation current at the same time.

[0096] The third preset threshold is determined by recording the range of change in the micro-pressure pulse derivative during the process of the grinding equipment moving from a compressed state to a stable release and disengagement. The average value of the micro-pressure pulse derivative during the stable release phase is selected as the third preset threshold, and this value is usually less than zero. When the high-frequency peak value does not exceed Ih and the micro-pressure pulse derivative is less than the third preset threshold, it is determined that the current contact has a release trend rather than impact accumulation. When it is confirmed that the system is not within the preset anti-vibration dead zone delay after the cylinder thrust is actively reduced, the basic thrust and the existing excitation level are maintained or slowly restored. The preset anti-vibration dead zone delay time is set to 2 to 5 control cycles to prevent secondary misjudgments caused by transient mechanical rebound after a sudden change in thrust. The final output of the process includes two types of results:

[0097] One type is the high-damping demand signal sent to the excitation coil 600 drive circuit, and the other type is the low-frequency thrust deviation signal sent to the electric proportional valve 700 or the cylinder control circuit, so that the model has a clear data source, calculation steps and control flow in the control system.

[0098] The free swing angle of the main spindle flange 510 relative to the ball joint support 300 is ±2° to ±12°;

[0099] In this embodiment, a ball joint is provided at the center of the lower surface of the main shaft flange 510, and a spherical head that mates with the ball joint is provided at the upper end of the ball joint support 300, forming a ball joint pair 520. The radius of the spherical head can be set from 15mm to 60mm. The material of the ball joint pair 520 can be tempered steel, hard chrome plated steel, or self-lubricating composite material to take into account both wear resistance and low friction requirements. The free swing angle of the main shaft flange 510 relative to the ball joint support 300 can be set from ±2° to ±12°, and the specific angle is selected according to the range of blade curvature variation and the size of the grinding disc 550.

[0100] The so-called preset angle range refers to the allowable wobble range determined by the geometric dimensions of the ball joint 520, the deformation of the hydraulic bladder group 400, and the clearance between the main spindle flange 510 and the surrounding structure. Within this range, the main spindle flange 510 can adjust its posture as the normal of the contact surface changes without mechanical interference. The ball joint 520 solves the posture adaptation problem when the axis of the low-friction cylinder 200 is not completely aligned with the normal of the local blades, allowing the main spindle flange 510 and the main spindle motor 540 above it to rotate around the center of the ball within a preset small angle range.

[0101] Since the hydraulic bladder group 400 is located below the outer periphery of the main spindle flange 510, the ball joint 520 provides rotational freedom, and the hydraulic bladder group 400 provides rotational damping and reverse support. When the two work together, the main spindle flange 510 can both swing to fit different curvature areas and will not produce unrestrained swaying under tangential friction disturbance. This swing structure can also reduce the bending moment level borne by the piston rod 210 and reduce the local wear of the seals and guides of the low-friction cylinder 200.

[0102] Example 2:

[0103] like Figure 3 As shown, a control method for a constant force floating control wind turbine blade surface grinding device includes:

[0104] S1. Control the low-friction cylinder 200 to output macroscopic thrust, and push the ball joint support 300 and the main shaft flange 510 close to the surface of the fan blades;

[0105] S2. Control the spindle motor 540 to drive the grinding disc 550 to perform rotary cutting;

[0106] S3. Real-time extraction of the high-frequency spectrum characteristics of the stator current of the spindle motor 540, the effective value of the fundamental wave of the stator current, and the micro-pressure pulse derivative of the back pressure chamber of the low-friction cylinder 200.

[0107] S4. Adjust the current of the excitation coil 600 and the macroscopic thrust of the low-friction cylinder 200 according to the high-frequency spectrum characteristics of the stator current, the fundamental effective value of the stator current, and the micro-pressure pulse derivative; wherein, when a high-frequency harmonic peak with an amplitude greater than the first preset threshold appears in the high-frequency spectrum characteristics of the stator current and the micro-pressure pulse derivative is within the preset zero value neighborhood, control the current of the excitation coil 600 to increase; when the fundamental effective value of the stator current increases monotonically within multiple consecutive preset time windows and the micro-pressure pulse derivative is greater than the second preset threshold, control the low-friction cylinder 200 to decrease the macroscopic thrust and control the current of the excitation coil 600 to decrease; in other cases, when the high-frequency spectrum characteristics of the stator current do not show a high-frequency harmonic peak exceeding the first preset threshold and the micro-pressure pulse derivative is less than the third preset threshold, control the low-friction cylinder 200 to restore to the basic thrust and maintain the existing excitation level, otherwise maintain the current thrust and excitation coil 600 current output by the low-friction cylinder 200;

[0108] S5. Repeat steps S1 to S4 above;

[0109] The control method in this embodiment is applied to the aforementioned grinding equipment; in S1, the controller gives a basic thrust command to the low-friction cylinder 200. The basic thrust is set according to the diameter of the grinding disc 550, the abrasive particle size and the material removal requirements, and can be set to 50N to 800N; the basic thrust makes the grinding disc 550 stably contact the blade surface, and at the same time provides a continuous normal load for subsequent attitude adaptation.

[0110] In S2, the controller drives the spindle motor 540 to work, and the spindle speed is set to 1000r / min to 6000r / min according to the process requirements. After the grinding disc 550 rotates, cutting contact is formed.

[0111] In S3, the current acquisition unit and the pressure acquisition unit continuously sample, and the controller extracts the high-frequency spectrum characteristics of the stator current and the derivative of the micro-pressure pulse of the back pressure cavity within a set time window.

[0112] The three control branches in S4 have clear decision-making roles: when the tangential friction disturbance is determined to be enhanced, the shear stiffness is increased to enhance the vibration damping capability; when the spindle load increases and is accompanied by an increased normal clamping trend, the grinding disc 550 produces a more compliant effect; when the contact load is in a released or stable falling state, the existing control value is maintained to avoid frequent adjustments.

[0113] In S5, the above steps are repeated according to the control cycle, which can be set from 1ms to 20ms.

[0114] This method integrates the load changes of the spindle motor 540, the back pressure changes of the cylinder, the stiffness changes of the magnetorheological material, and the attitude correction of the hydraulic bladder into the same control process, so that macroscopic thrust adjustment and microscopic damping adjustment can simultaneously serve the constant force grinding target. The judgment process in S3 and S4 can be refined in time sequence as follows: at the beginning of each control cycle, the stator current sampling value and the back pressure chamber pressure sampling value are read synchronously; the stator current data within the current sliding time window is subjected to spectrum analysis to determine whether there are high frequency peaks exceeding the preset criteria, and the difference between adjacent time moments is calculated for the pressure sampling value to obtain the micro-pressure pulse derivative.

[0115] The high-frequency peak value determination result, the fundamental effective value change trend, and the sign and amplitude of the micro-pressure pulse derivative are input into the control discrimination unit. The control discrimination unit generates the current adjustment command for the excitation coil 600 and the thrust adjustment command for the low-friction cylinder 200 respectively. Thus, S4 does not adjust based on the spectrum characteristics and derivative in a general way, but completes the control by synchronous sampling, spectrum extraction, trend judgment and branch output in sequence.

[0116] Among them, the specific high-frequency harmonic peak value is a criterion used to identify tangential impact and local flutter. Its physical meaning is that the peak amplitude or energy ratio in the preset high-frequency band exceeds the allowable upper limit of the normal grinding state. This criterion can be pre-calibrated during the equipment commissioning stage: record the spectrum distribution under three states: no-load rotation, normal grinding and artificially applied slight tangential disturbance, and select the peak threshold that can stably distinguish between normal grinding and abnormal tangential disturbance as the trigger boundary corresponding to the specific high-frequency harmonic peak value.

[0117] The so-called monotonically increasing fundamental effective value of stator current means that it shows a continuous upward trend in multiple consecutive control time windows, and the increase in magnitude exceeds the noise threshold each time, thereby avoiding the misjudgment of instantaneous fluctuations as a continuous increase in load.

[0118] Maintaining the base thrust and excitation coil current of 600 means maintaining the currently established base thrust setting and the excitation current level of the previous control cycle, and only limiting the holding when necessary, without introducing new thrust corrections or excitation corrections.

[0119] The three types of control branches in S4 have clear decision-making roles. In the first type of branch, when a high-frequency peak appears and the derivative of the micro-pressure pulse is within the preset zero value neighborhood, it indicates that the contact normal pressure is basically stable but the tangential friction disturbance is enhanced. At this time, the purpose of increasing the current of the excitation coil 600 is to improve the shear stiffness and vibration damping capability of the magnetorheological elastomer shear pad 530.

[0120] In the second type of branch, when the fundamental effective value continues to rise and the micro-pressure pulse derivative is positive and exceeds the preset threshold, it indicates that the spindle load increases and the normal clamping trend is strengthened. At this time, the purpose of reducing the macro thrust and reducing the current of the excitation coil 600 at the same time is to make the grinding disc 550 produce a more compliant effect along the normal direction.

[0121] In the third type of branch, when no specific high-frequency harmonic peak appears and the derivative of the micro-pressure pulse is less than zero, it indicates that the contact load is in a state of release or stable decline. At this time, maintaining the existing control quantity can avoid unnecessary frequent adjustments. Through the above step-by-step explanation, each judgment quantity in the control method has a clear physical meaning, source of acquisition, and logical relationship to trigger subsequent control actions.

[0122] To verify the effectiveness of the control method in this embodiment, a comparative experiment was conducted between the equipment using this control method and the traditional grinding equipment that only uses cylinder constant force control under the same large wind turbine blade variable cross-section free-form surface grinding conditions. The experimental data showed that when passing through the high curvature change area of ​​the blade, the normal contact force fluctuation range of the traditional equipment reached ±25% of the set thrust, while the normal contact force fluctuation range of this equipment was controlled within ±8% of the set thrust.

[0123] When encountering frictional disturbances caused by tangential hard points, the peak value of the high-frequency vibration acceleration of the spindle in traditional equipment reaches 4.5g, while the peak value of the high-frequency vibration acceleration of the spindle in this equipment is reduced to below 1.2g due to the rapid stiffening and vibration suppression effect of the magnetorheological elastomer shear pad 530. This comparative data fully demonstrates the significant technical effect of this control method in terms of normal compliance and tangential vibration suppression.

[0124] The constant force floating control wind turbine blade surface grinding equipment also includes an electro-proportional valve 700 connected to the controller; the step of controlling the low friction cylinder 200 to reduce the macroscopic thrust in S4 includes: generating a low-frequency thrust deviation signal based on the micro-pressure pulse derivative and the effective value of the stator current fundamental wave, and sending the low-frequency thrust deviation signal to the electro-proportional valve 700 to reduce the macroscopic thrust of the low friction cylinder 200;

[0125] In this embodiment, when the controller executes step S4, it outputs the low-frequency thrust deviation signal calculated by the variable stiffness compensation model to the electric proportional valve 700. The so-called low-frequency thrust deviation signal refers to the control quantity that reflects the macroscopic normal load correction requirement. Its update cycle is slower than the current adjustment cycle of the excitation coil 600. The update cycle can be set to 20ms to 500ms.

[0126] The controller calculates the thrust correction based on the trend of the fundamental effective value of the 540 stator current of the spindle motor, the derivative of the micro-pressure pulse in the back pressure chamber, and the current basic thrust value. And based on the effective pressure area Converted to pressure correction amount ,satisfy After receiving the corresponding electrical signal, the electric proportional valve 700 adjusts the intake pressure or exhaust throttling degree of the low-friction cylinder 200, so that the cylinder output thrust gradually decreases according to the set amplitude. For example, when the model determines that it has entered the high curvature climbing area, the controller can adjust the cylinder thrust from 300N to 220N within a time range of 100ms to 300ms, instead of dropping it to the target value instantaneously, so as to avoid the grinding disc 550 being deflected or unstable in contact due to sudden changes in thrust.

[0127] The reason for using long-cycle adjustment is that the low-friction cylinder 200 is responsible for building macroscopic normal thrust. The geometric change of the blade is a low-frequency change relative to the tangential vibration, so it is suitable to be smoothly corrected by the electric proportional valve 700. This can keep the cylinder thrust change and the material removal process continuous and reduce the additional load disturbance caused by rapid air pressure fluctuations.

[0128] The controller has a preset variable stiffness compensation model; the step of increasing the current of the excitation coil 600 in S4 includes: the variable stiffness compensation model generates a high damping demand signal based on the high frequency spectrum characteristics of the stator current, and converts the high damping demand signal into a pulse width modulation signal and sends it to the excitation coil 600; the step of decreasing the current of the excitation coil 600 in S4 includes: the controller sends a pulse width modulation signal to decrease the current of the excitation coil 600.

[0129] In this embodiment, the variable stiffness compensation model in the controller outputs not only the low-frequency thrust deviation signal, but also a high damping demand signal for controlling the excitation coil 600. When performing duty cycle conversion, the purpose of this model is to quantify the abstract damping demand into a specific electromagnetic control quantity, so as to achieve precise intervention on the apparent shear modulus of the magnetorheological elastic body. In terms of logic structure and data flow, this conversion process is completed by the signal mapping submodule. This submodule receives the high damping demand signal as input, combines it with the current temperature feedback of the excitation coil 600 and the power supply voltage fluctuation compensation coefficient, calculates a basic duty cycle, and outputs the final pulse width modulation signal after amplitude limiting and filtering.

[0130] Specifically, the calculation rules for this process are broken down into the following steps: First, the initial duty cycle is obtained by looking up a table based on the high damping demand signal; Second, the temperature value fed back by the thermistor installed on the surface of the excitation coil 600 is read. When the temperature exceeds the preset standard operating temperature, the temperature compensation gain is calculated by increasing by 0.5% for every 1°C increase, in order to offset the current attenuation caused by the increase in copper wire resistance.

[0131] The third step is to collect the drive power supply voltage in real time. When the voltage is lower than the rated value, the ratio of the rated voltage to the actual voltage is calculated as the voltage compensation coefficient. When the voltage is greater than or equal to the rated value, the voltage compensation coefficient is set to 1. The fourth step is to multiply the initial duty cycle, temperature compensation gain and voltage compensation coefficient to obtain the base duty cycle.

[0132] For example, if the preset standard operating temperature is 40°C, and the initial duty cycle is 50%, the current temperature of 50°C results in a temperature compensation gain of 1.05, and the actual voltage is 0.95 times the rated voltage, resulting in a voltage compensation coefficient of approximately 1.052. Then, the corrected base duty cycle is approximately 55.2%. This structured quantitative deduction logic clearly defines how temperature and voltage data flow and correct the final output, giving the underlying algorithm clear logical traceability and ensuring the accuracy of pulse width modulation signal adjustment.

[0133] This conversion model characterizes the electromagnetic induction law of the excitation coil 600 and the micro-rheological physical relationship between the magnetic sensitive particles in the magnetorheological elastomer forming a chain structure under different magnetic field strengths. That is, the duty cycle determines the average excitation current, the current determines the magnetic field strength, and determines the shear strength of the magnetic sensitive particle chain. The high damping demand signal can be expressed as a duty cycle target value of 0 to 100%, or as a target current value of 0A to 5A. The controller converts it into a pulse width modulation signal and sends it to the excitation coil 600 drive circuit.

[0134] The pulse width modulation carrier frequency can be set from 1kHz to 20kHz, and the duty cycle adjustment resolution can be set from 8 bits to 16 bits. The excitation coil 600 consists of a magnetic core and windings, and the number of winding turns can be set from 200 to 1500 turns. After being energized, it establishes a magnetic field around the magnetorheological elastomer shear pad 530. When the current of the excitation coil 600 is increased, the magnetic sensitive particles in the magnetorheological elastomer form a stronger interaction structure under the action of the magnetic field, the apparent shear modulus of the material increases, and the micro-displacement of the spindle motor 540 relative to the spindle flange 510 decreases, which is suitable for suppressing tangential high-frequency disturbances.

[0135] When the current of the excitation coil 600 is reduced, the shear stiffness of the material decreases, the damping energy dissipation characteristics become more prominent, and the grinding disc 550 is more likely to make slight yielding along the normal direction, which is suitable for reducing contact overload in areas with abrupt changes in high curvature. In this embodiment, the update cycle of the pulse width modulation signal can be set to 0.5ms to 10ms, which is faster than the thrust adjustment cycle of the electric proportional valve 700, so it can undertake the task of rapid adjustment at the microscale.

[0136] The variable stiffness compensation model uses the high-frequency current spectrum characteristics, fundamental wave effective value change and back pressure pulse derivative together to calculate the duty cycle, so that the control quantity of excitation coil 600 keeps the corresponding relationship with the spindle load state, thereby enabling the magnetorheological elastomer shear pad 530 to provide different shear constraints and damping levels under different grinding conditions.

[0137] The high damping demand signal is an intermediate decision quantity in the control logic. It is used to quantify the magnetic field strength level that the excitation coil 600 needs to provide under the current operating conditions. Its physical meaning is not simply the size of the material damping, but rather a comprehensive reflection of the excitation target after the tangential disturbance rejection requirement and the normal compliance requirement.

[0138] Specifically, when the controller determines that tangential impact is dominant, the high-damping demand signal increases; when the controller determines that normal clamping is too strong and contact needs to be released, the high-damping demand signal decreases. This signal does not originate from a single sensing quantity, but is obtained by fusing three types of information—high-frequency current spectrum characteristics, fundamental effective value variation trend, and back pressure pulse derivative—through a variable stiffness compensation model. Therefore, its role in the system is as a direct input criterion for the excitation coil 600 control link. The process of converting the high-damping demand signal generated based on the stator current high-frequency spectrum characteristics into a pulse-width modulated signal can be implemented as follows:

[0139] Step 1: The controller reads the high damping demand signal within the current control cycle and converts it into a target current value or a target duty cycle value.

[0140] Step 2: Limit the target value with upper and lower limits and change slope to avoid coil overcurrent, overheating or jumps exceeding the preset change rate threshold in adjacent cycles;

[0141] Step 3: Based on the excitation coil 600 drive power supply voltage, coil resistance, and driver rated capability, map the target value to the pulse width modulation duty cycle;

[0142] Step 4: Send the duty cycle to the drive circuit and reread the actual current feedback or estimate the current value in the next control cycle as a basis for subsequent corrections.

[0143] In this way, a clear data flow path is formed between model output, duty cycle generation and drive execution; the control actions of increasing and decreasing the current of the excitation coil 600 also have clear criterion boundaries; for the case of increasing the current, it is preferable to execute when the high frequency spectrum peak is detected to exceed the pre-calibrated threshold in one or more consecutive control cycles, and the derivative of the back pressure pulse is within the preset zero value neighborhood, so as to prevent malfunctions triggered by a single noise pulse.

[0144] For reducing current, it is preferable to execute when the fundamental effective value continues to rise and the back pressure pulse derivative is greater than the positive threshold, so as to ensure that the reduction of excitation is to release excessive normal contact, rather than erroneously softening the system when tangential vibration is severe; the so-called emission of pulse width modulation signal to reduce the current of excitation coil by 600 includes any of the following implementation methods: reducing the duty cycle, reducing the target current value, or entering a lower excitation level.

[0145] To improve the sufficiency of disclosure, the duty cycle calculation in this embodiment can be implemented by a hierarchical mapping method without relying on complex formulas; for example, the high-damping demand signal can be divided into a first level, a second level, a third level, and a fourth level, which correspond to the first preset duty cycle, the second preset duty cycle, the third preset duty cycle, and the maximum duty cycle within the upper limit protection, respectively; the controller directly outputs the corresponding duty cycle according to the current level, and allows for smooth transitions between adjacent levels;

[0146] The final output of the process is a pulse width modulation signal sent to the excitation coil 600 drive circuit. This signal directly determines the magnetic field level of the magnetorheological elastomer shear pad 530 and further acts on the stiffening or softening control step in S4. Through the above step-by-step processing, the control of the excitation coil 600 no longer stops at the abstract expression of direct control after model output, but has an executable input source, processing steps, criterion function and output destination.

[0147] This application has been described through the above embodiments; however, it should be understood that the above embodiments are for illustrative purposes only and are not intended to limit this application to the described embodiments. Those skilled in the art will understand that many more variations and modifications can be made based on the teachings of this application, and all such variations and modifications fall within the scope of protection claimed in this application.

Claims

1. A constant force floating control wind turbine blade surface grinding device, characterized in that, include: Base (1); A low-friction cylinder (200) is located at the center of the base (1), and has a back pressure chamber inside. The end of its piston rod (210) is connected to a ball joint support (300). A group of hydraulic bladders (400) surrounds the periphery of the ball joint support (300). The first hydraulic bladder (410) and the opposite third hydraulic bladder (430), the second hydraulic bladder (420) and the opposite fourth hydraulic bladder (440) are arranged in a cross shape and are connected through the first cross flow channel (310) and the second cross flow channel (320) in the ball joint support (300), respectively. The grinding spindle functional unit (500) is supported on top by a hydraulic bladder group (400). The bottom center of its spindle flange (510) is movably connected to the upper spherical surface of the ball joint support (300) through a ball joint pair (520). The magnetorheological elastomer shear pad (530) is connected to the top surface of the spindle flange (510). The bottom flange (541) of the spindle motor (540) is connected to the top surface of the magnetorheological elastomer shear pad (530). The output shaft (542) of the spindle motor (540) is vertically connected to the grinding disc (550). An excitation coil (600) is fixedly wrapped around the outer periphery of a magnetorheological elastomer shear pad (530); A pressure sensor is disposed on the back pressure chamber of the low-friction cylinder (200); A current sensor is mounted on the spindle motor (540) and connected in series in the stator power supply circuit of the spindle motor (540); The controller connects to and controls the low-friction cylinder (200), the spindle motor (540), and the excitation coil (600); the pressure sensor and the current sensor are both connected to the controller.

2. The constant force floating control wind turbine blade surface grinding equipment according to claim 1, characterized in that, The low-friction cylinder (200) is fixedly connected to the base (1) by bolts, and the end of the piston rod (210) of the low-friction cylinder (200) is threadedly connected to the lower end of the ball joint support (300).

3. The constant force floating control wind turbine blade surface grinding equipment according to claim 1, characterized in that, The first hydraulic bladder (410), the third hydraulic bladder (430) and the first cross flow channel (310) are filled with hydraulic oil, and the second hydraulic bladder (420), the fourth hydraulic bladder (440) and the second cross flow channel (320) are filled with hydraulic oil.

4. The constant force floating control wind turbine blade surface grinding equipment according to claim 1, characterized in that, The magnetorheological elastomer shear pad (530) has a circular structure, and the bottom flange (541) of the housing of the main shaft motor (540) is fixedly connected to the top surface of the magnetorheological elastomer shear pad (530) by bolts.

5. The constant force floating control wind turbine blade surface grinding equipment according to claim 1, characterized in that, The grinding equipment also includes an electro-proportional valve (700) disposed in the low-friction cylinder (200), the electro-proportional valve (700) being connected to the controller.

6. The constant force floating control wind turbine blade surface grinding equipment according to claim 1, characterized in that, The controller is pre-set with a variable stiffness compensation model, which is configured to receive the high-frequency spectrum characteristics of the stator current of the spindle motor (540), the effective value of the fundamental wave of the stator current, and the micro-pressure pulse derivative of the back pressure chamber of the low-friction cylinder (200) based on the signals extracted from the current sensor and the pressure sensor. The variable stiffness compensation model is configured to generate a high damping demand signal based on the high frequency spectrum characteristics of the stator current and output it to the excitation coil (600), and generate a low frequency thrust deviation signal based on the micro-pressure pulse derivative and the effective value of the fundamental wave of the stator current of the main spindle motor (540) and output it to the low friction cylinder (200).

7. The constant force floating control wind turbine blade surface grinding equipment according to claim 1, characterized in that, The free swing angle of the main shaft flange (510) relative to the ball joint support (300) is ±2° to ±12°.

8. A control method for a constant force floating control wind turbine blade surface grinding device, applied to the constant force floating control wind turbine blade surface grinding device according to any one of claims 1 to 7, characterized in that, include: S1. Control the low-friction cylinder (200) to output macroscopic thrust, and push the ball joint support (300) and the main shaft flange (510) close to the surface of the fan blade; S2. Control the spindle motor (540) to drive the grinding disc (550) to perform rotary cutting; S3. Real-time extraction of the high-frequency spectrum characteristics of the stator current of the main spindle motor (540), the effective value of the fundamental wave of the stator current, and the micro-pressure pulse derivative of the back pressure chamber of the low-friction cylinder (200); S4. Adjust the current of the excitation coil (600) and the macroscopic thrust of the low-friction cylinder (200) according to the high-frequency spectrum characteristics of the stator current, the fundamental effective value of the stator current, and the micro-pressure pulse derivative; wherein, when a high-frequency harmonic peak with an amplitude greater than a first preset threshold appears in the high-frequency spectrum characteristics of the stator current and the micro-pressure pulse derivative is within a preset zero-value neighborhood, control the current of the excitation coil (600) to increase; when the fundamental effective value of the stator current increases monotonically within multiple consecutive preset time windows and the micro-pressure pulse derivative is greater than a second preset threshold, control the low-friction cylinder (200) to decrease the macroscopic thrust and control the current of the excitation coil (600) to decrease; In other cases, when the high frequency spectrum characteristics of the stator current do not show a high frequency harmonic peak exceeding the first preset threshold, and the micro-pressure pulse derivative is less than the third preset threshold, the low friction cylinder (200) is controlled to return to the basic thrust and maintain the existing excitation level; otherwise, the low friction cylinder (200) is kept to output the current thrust and the current of the excitation coil (600). S5. Repeat steps S1 to S4 above.

9. The control method according to claim 8, characterized in that, The constant force floating control wind turbine blade surface grinding equipment also includes an electro-proportional valve (700) connected to the controller; the step of controlling the low friction cylinder (200) to reduce the macroscopic thrust in S4 includes: generating a low-frequency thrust deviation signal based on the micro-pressure pulse derivative and the effective value of the stator current fundamental wave, and sending the low-frequency thrust deviation signal to the electro-proportional valve (700) to reduce the macroscopic thrust of the low friction cylinder (200).

10. The control method according to claim 8, characterized in that, The controller is preset with a variable stiffness compensation model; the step of controlling the increase of the current of the excitation coil (600) in S4 includes: controlling the variable stiffness compensation model to generate a high damping demand signal according to the high frequency spectrum characteristics of the stator current, and converting the high damping demand signal into a pulse width modulation signal and sending it to the excitation coil (600); the step of controlling the decrease of the current of the excitation coil (600) in S4 includes: the controller sending a pulse width modulation signal to decrease the current of the excitation coil (600).

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