Posture self-adaptive constant force polishing device based on macro-micro cooperation and elastic compensation

Abstract

The application is a posture self-adaptive constant force polishing device based on macro-micro cooperation and elastic compensation, comprising: a base platform, a magnetic suspension micro-motion unit, an elastic compensation unit configured to provide elastic tension force pointing away from the workpiece direction, a six-dimensional force sensor, an intermediate floating platform located above the magnetic suspension micro-motion unit, a macro-motion posture adjusting mechanism for realizing axial large-stroke extension and deflection posture adjusting motion relative to the intermediate floating platform, and a working unit. The magnetic suspension micro-motion unit comprises a magnetic suspension stator fixed to the base platform, a magnetic suspension mover fixed to the intermediate floating platform, and an electromagnetic drive assembly. The electromagnetic attraction force between the stator and the mover is configured as an active control variable. The linear stiffness coefficient of the elastic compensation unit is configured to be greater than the absolute value of the displacement negative stiffness coefficient at the preset balance air gap of the electromagnetic drive assembly. The device can still generate stable feeding force relying on electromagnetic attraction force in inverted or lateral posture, and has high adaptability.

Description

Technical Field

[0001] This invention belongs to the field of precision machining equipment and intelligent control technology for robots. Specifically, it relates to a posture-adaptive robot constant force grinding device and control method that is applied to the machining of large and complex curved surfaces, actively outputs grinding pressure using electromagnetic attraction, and maintains a linear working range through macro-micro collaborative drive. Background Technology

[0002] With the development of industrial automation technology, when industrial robots grind and polish large composite material components such as wind turbine blades, aircraft skins, and yacht hulls, due to the large curvature variation and poor consistency of the workpiece surface, as well as the insufficient rigidity of the robot body, it is necessary to install a force-controlled end effector at the end of the robotic arm to compensate for trajectory errors and maintain a constant contact force.

[0003] Existing constant-force grinding devices suffer from the following limitations: First, while pure pneumatic devices offer a large stroke, their force control response bandwidth is low due to the compressibility of gas and cylinder friction, making it difficult to suppress high-frequency cutting vibrations. Second, magnetic levitation drive devices offer fast response speed, high bandwidth, and no friction interference, but existing magnetic levitation devices rely solely on magnetic force to balance gravity, resulting in limited effective load capacity. To reduce energy consumption and size, conventional magnetic levitation devices tend to employ electromagnetic attraction principles. However, electromagnetic attraction inherently possesses negative stiffness—the smaller the air gap, the greater the attraction—making it easy for the mover to detach from its equilibrium point and collide with the stator when disturbed, easily leading to "attraction instability." Furthermore, the force-current characteristics of electromagnetic attraction only exhibit good linearity within a very narrow air gap range; beyond this range, severe nonlinearity occurs, significantly increasing control difficulty and power consumption. Finally, traditional single-axis floating devices can only adjust the normal force and cannot sense or correct the angle between the grinding disc and the workpiece surface. When machining workpieces with large curvature, the inability to automatically correct normal alignment deviations can lead to unilateral grinding or surface defects such as "crescent-shaped" patterns. A single driving method cannot reconcile the contradiction between macroscopic attitude adjustment and microscopic high-frequency force control.

[0004] Therefore, there is an urgent need for a grinding device that can achieve wide-range attitude self-adaptation, use electromagnetic attraction as an active power source to output grinding force, and has an anti-instability mechanism to overcome the instability of electromagnetic attraction and maintain high-frequency, high-precision constant force output. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a posture adaptive constant force grinding device based on macro-micro coordination and elastic compensation, which addresses the problems of slow response speed of traditional grinding devices, narrow linear working range of electromagnetic suction grinding devices, and inability of traditional grinding devices to automatically correct normal contact deviation when facing workpieces with large curvature.

[0006] To solve the above technical problems, the following technical solutions can be used: In a first aspect, the present invention provides an attitude-adaptive constant-force grinding device based on macro-micro coordination and elastic compensation, the device comprising: The base platform is configured to be rigidly connected to the end flange of the industrial robot, serving as the mounting base for the device. The magnetic levitation micro-motion unit is connected between the base platform and the intermediate floating platform. It includes a magnetic levitation stator 3 fixed to the base platform, a magnetic levitation mover fixed to the intermediate floating platform, and an electromagnetic drive assembly. The electromagnetic attraction between the magnetic levitation stator and the magnetic levitation mover is configured as an active control variable to drive the intermediate floating platform to perform axial micro-motion and force output relative to the base platform. An elastic compensation unit is disposed between the base platform and the intermediate floating platform and is configured to provide an elastic tension pointing away from the workpiece; the direction of the elastic tension is opposite to the direction of the electromagnetic force; the linear stiffness coefficient of the elastic compensation unit is configured to be greater than the absolute value of the displacement negative stiffness coefficient at the preset balance air gap of the electromagnetic drive assembly; at the same time, by utilizing the combined effect of adjustable electromagnetic attraction and elastic force, the electromagnetic attraction is converted into an adjustable grinding clamping force; The intermediate floating platform is located above the magnetic levitation micro-motion unit and is suspended and supported by the magnetic levitation micro-motion unit and the elastic compensation unit. The macro-motion attitude adjustment mechanism is used to realize the axial large stroke extension and deflection attitude adjustment movement relative to the intermediate floating platform. It is installed below the intermediate floating platform and includes multiple pneumatic actuators evenly distributed in the circumferential direction, a connecting plate for connecting the upper end of all pneumatic actuators to the intermediate floating platform, and a transition plate for connecting the lower end of all pneumatic actuators to the six-dimensional force sensor. A six-dimensional force sensor is installed below the transition disk of the macro-motion attitude adjustment mechanism to detect the grinding contact normal force and tangential torque; The working unit, connected to the input end of the six-dimensional force sensor, includes a grinding head for the final grinding operation.

[0007] Furthermore, the lower ends of each pneumatic actuator are connected by flexible connectors and converge to the lower transition plate, forming a multi-degree-of-freedom parallel mechanism.

[0008] Furthermore, the base platform includes a top plate, a bottom plate, and multiple side plates connected to the top plate. The upper end of the top plate is rigidly connected to the end flange of the industrial robot by bolts. The bottom plate has a central through hole for the intermediate floating platform to float up and down, and multiple mounting slots for mounting the magnetic levitation stator are evenly distributed around the central through hole. Each side plate has a sliding groove for the intermediate floating platform to float up and down on the side facing the center.

[0009] Furthermore, the intermediate floating platform includes a floating mounting platform and a connecting shaft disposed at the center of the floating mounting platform. Sliding extensions matching the slide groove are evenly arranged around the floating mounting platform. The connecting shaft is fixed to the floating mounting platform in the middle by a bushing and a key. The connecting shaft moves synchronously with the floating mounting platform. An elastic compensation unit is sleeved between the upper part of the connecting shaft and the lower surface of the top plate of the base platform. The upper end of the elastic compensation unit is fixed to the top plate. The distance between the upper end of the connecting shaft and the top plate is not less than the set macroscopic movement distance. The lower end of the elastic compensation unit is fixed to the floating mounting platform. The lower end of the connecting shaft passes through the middle through hole of the bottom plate of the base platform and is connected to the macroscopic attitude adjustment mechanism. The elastic compensation unit includes at least one tension spring.

[0010] Furthermore, a baffle is provided at the lower end of the connecting shaft.

[0011] Furthermore, a stiffness adjustment mechanism connected to the elastic compensation unit is provided at the top plate of the base platform. The stiffness adjustment mechanism adopts a threaded lifting structure. By rotating the adjustment ring, the axial position of the upper hanging point of the elastic compensation unit is changed, thereby changing the initial elongation of the tension spring without changing the overall height of the device. When a heavier grinding head is replaced, the adjustment ring is rotated to increase the initial elongation of the tension spring, thereby increasing the upward pulling force generated. Thus, without changing the working air gap of the magnetic levitation, the balance equation of elastic force + new gravity = attraction force in the non-contact suspension state is re-established.

[0012] Furthermore, in the absence of electromagnetic force, the elastic compensation unit pulls the intermediate floating platform and the lower components toward the direction of the top plate of the base platform, causing the magnetic levitation mover and the magnetic levitation stator to move away from each other. When polishing is required, the controller applies an excitation current to the magnetically levitated stator, causing the magnetically levitated mover to generate a downward electromagnetic attraction. The force balance equation of the device is: ; in To provide the grinding force applied to the workpiece. The upward pulling force of the spring. For gravity; By adjusting the electromagnetic attraction force Actively adjust output force When grinding upside down (workpiece on top), gravity... Reverse, electromagnetic attraction The direction is upward; at this point, simply increase the electromagnetic attraction. It overcomes gravity and spring force, thus enabling the grinding head to be sucked upwards onto the workpiece surface for processing; When the macro-motion attitude adjustment mechanism makes large-scale attitude adjustments, the magnetic levitation micro-motion unit above can absorb and isolate high-frequency vibrations in real time, protecting the robot body while providing high-precision constant force floating.

[0013] Furthermore, the magnetically levitated mover and stator are composed of permanent magnets on one side and electromagnets on the other. The macro-motion attitude adjustment mechanism has three pneumatic actuators. The upper cylinder end of the pneumatic actuator is hinged to the connecting plate through a Hooke hinge to limit the rotation of the pneumatic actuator around its own axis and prevent air circuit entanglement. The lower end of the piston rod is connected to the transition plate downward through a ball hinge to drive the lower component to perform a wide range of axial extension and angular deflection.

[0014] Furthermore, three eddy current or Hall sensors are evenly distributed at the center or around the circumference of the magnetic levitation stator to calculate the displacement of the intermediate floating platform. The macro-motion attitude adjustment mechanism is connected in series with a precision electric proportional valve to control the air circuit; The electromagnetic attraction model F of the electromagnetic drive component approximately satisfies ,in is the magnetic constant. For air gap; the linear stiffness coefficient of the elastic compensation unit Satisfies the stability inequality: ,in The preset optimal linear balance air gap.

[0015] Secondly, the present invention provides an attitude-adaptive constant-force grinding control method based on macro-micro coordination and elastic compensation. The control method employs the aforementioned device and includes the following steps: S1 signal decoupling: Acquire the six-dimensional force sensor signal, extract the low-frequency contour force signal through the low-pass filter, extract the high-frequency force error signal through the high-pass filter, and directly read the torque around the X-axis and Y-axis output by the sensor as the contact torque signal. S2 Zero Torque Attitude Calculation: Based on the contact torque signal, the required tilt angle correction of the intermediate floating platform is calculated through the contact stiffness model and converted into asynchronous differential extension commands of each pneumatic actuator in the macro-motion attitude adjustment mechanism to drive the intermediate floating platform to deflect until the contact torque converges to the preset threshold range. S3 Linear Zone Maintenance Control: Based on the low-frequency contour force signal, control each pneumatic actuator in the macro-motion attitude adjustment mechanism to perform synchronous common mode expansion and contraction, and compensate for the macro-contour undulation of the workpiece surface in real time, so that the magnetic levitation mover of the magnetic levitation micro-motion unit is always maintained within the preset linear balance air gap range. S4 High-Frequency Constant Force Suppression and Active Output: Under the premise that the magnetic levitation micro-motion unit is maintained within the linear balance air gap range, the excitation current of the electromagnetic drive component is adjusted based on the high-frequency force error signal to suppress high-frequency cutting vibration. At the same time, the high-frequency constant force output is achieved by controlling the magnitude of the electromagnetic attraction force of the magnetic levitation stator on the magnetic levitation mover.

[0016] Furthermore, the cutoff frequency of the low-pass filter is set to 5-8Hz; the cutoff frequency of the high-pass filter is set to 10-12Hz. Using the point cloud data of the 3D model of the workpiece being ground, or by installing a line laser profilometer or structured light camera to generate point cloud data, the rate of change of the normal vector of the surface is obtained. Before the grinding head reaches the curvature change point, the host computer searches forward along the planned path in the model according to the current position coordinates of the grinding head and the feed speed vector, predicts the change of the normal vector and curvature of the workpiece surface at the next moment, calculates the tilt angle and displacement of the macro-motion attitude adjustment mechanism required to maintain normal alignment, and adds them to the control loop as feedforward quantities, sending commands to multiple pneumatic actuators in advance to start action.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) Active output of electromagnetic attraction and all-position machining: This invention changes the traditional approach of using magnetic levitation only for passive vibration isolation. During operation, the electromagnetic attraction is increased to overcome spring resistance and gravity, actively outputting grinding pressure. This mechanism allows the device to generate a stable feed force by relying on electromagnetic attraction even in inverted or lateral positions, making it highly adaptable and breaking through the limitations of traditional airbag-type grinding heads that rely on gravity assistance.

[0018] (2) Excellent vibration isolation characteristics: The “micro-top and macro-bottom” serial layout is adopted, with the middle floating platform as the suspension base. Through the redesign of the structure, the electromagnetic attraction force directly participates in the construction of the contact force, which can effectively isolate the high-frequency vibration during the grinding process from being transmitted to the robot body and protect the robot joints.

[0019] (3) Optimal linear region locking: This invention establishes a synergistic relationship between macro-motion and micro-motion. The macro-motion attitude adjustment mechanism is responsible for large-range contour tracking, always keeping the magnetic levitation micro-motion unit at the optimal linear operating point of the magnetic field characteristics, avoiding high energy consumption and control divergence in the nonlinear region, and significantly improving the system's energy efficiency ratio and force control accuracy.

[0020] (4) Intrinsic safety: By limiting the stiffness of the elastic compensation unit, the positive stiffness of the spring suppresses the negative stiffness of the electromagnetic attraction. Even if the control system fails completely or is powered off, the device can rely on the balance between the passive elastic compensation force and its own gravity and electromagnetic force to return the mover to a safe position, thus solving the potential collision risk caused by the attraction instability of the magnetic levitation at the physical level.

[0021] (5) Torque feedback attitude adaptation: The torque feedback of the six-dimensional force sensor is used to control the differential pneumatic actuator, which realizes blind bonding without the need for visual sensors. It can automatically eliminate the angle between the grinding disc and the workpiece, ensuring the consistency of processing quality and avoiding one-sided over-grinding. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the device provided in one embodiment of the present invention.

[0023] Figure 2 This is a schematic diagram of the base platform and magnetic levitation stator distribution according to an embodiment of the present invention.

[0024] Figure 3 This is a schematic diagram of the structure of an intermediate floating platform according to an embodiment of the present invention.

[0025] Figure 4 This is a schematic diagram of the magnetic levitation mover distribution according to an embodiment of the present invention.

[0026] Figure 5 This is a flowchart illustrating the control method according to an embodiment of the present invention.

[0027] Reference numerals: 1-Base platform; 2-Elastic compensation unit; 3-Magnetic levitation stator; 4-Magnetic levitation mover; 5-Intermediate floating platform; 6-Connecting plate; 7-Pneumatic actuator; 8-Six-dimensional force sensor; 9-Working unit; 10-Transition plate. Detailed Implementation

[0028] To make the description of the objectives, technical solutions and advantages of the present invention more complete, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0029] Example 1 This invention relates to an attitude-adaptive constant-force grinding device based on macro-micro coordination and elastic compensation, such as... Figure 1 As shown, its main structure consists of an upper micro-motion constant force stage and a lower macro-motion attitude adjustment stage connected in series. It includes a base platform 1, an elastic compensation unit 2 and a magnetic levitation micro-motion unit, an intermediate floating platform 5, a macro-motion attitude adjustment mechanism, a six-dimensional force sensor 8, and a working unit 9; the specific structure is as follows: The base platform is configured to be rigidly connected to the end flange of the industrial robot, serving as the mounting base for the device. The magnetic levitation micro-motion unit, connected between the base platform and the intermediate floating platform, includes a magnetic levitation stator 3 fixed to the base platform, a magnetic levitation mover 4 fixed to the intermediate floating platform, and an electromagnetic drive assembly; the electromagnetic attraction between the magnetic levitation stator and the magnetic levitation mover is configured as an active control variable to drive the intermediate floating platform to perform axial micro-motion and force output relative to the base platform; An elastic compensation unit is disposed between the base platform and the intermediate floating platform and is configured to provide an elastic pulling force pointing away from the workpiece; the direction of the elastic pulling force is opposite to the direction of the electromagnetic force; the linear stiffness coefficient of the elastic compensation unit is configured to be greater than the absolute value of the displacement negative stiffness coefficient at the preset balance air gap of the electromagnetic drive assembly, so as to avoid collision caused by attraction instability; at the same time, by utilizing the combined effect of adjustable electromagnetic attraction and elastic force, the electromagnetic attraction is converted into an adjustable grinding clamping force.

[0030] The intermediate floating platform, located above the magnetic levitation micro-motion unit, is suspended and supported by the magnetic levitation micro-motion unit and the elastic compensation unit, and together with the base platform, it forms the overall frame of the device. The macro-motion attitude adjustment mechanism is installed below the intermediate floating platform and includes at least three pneumatic actuators evenly distributed along the circumference, a connecting plate 6 for connecting the upper ends of all pneumatic actuators to the intermediate floating platform, and a transition plate for connecting the lower ends of all pneumatic actuators to the six-dimensional force sensor. The lower ends of each pneumatic actuator are connected by flexible connectors and converge to the lower transition plate to form a multi-degree-of-freedom parallel mechanism for realizing axial large-stroke extension and deflection attitude adjustment relative to the intermediate floating platform. A six-dimensional force sensor is installed below the transition plate of the macro-motion attitude adjustment mechanism to detect the grinding contact normal force and tangential torque; The working unit, connected to the input end of the six-dimensional force sensor, includes a grinding head for the final grinding operation.

[0031] The key feature of this "micro-on-top, macro-on-bottom" layout is that it utilizes a magnetically levitated mover with extremely fast response and an intermediate floating platform as a floating base to suspend the entire macro-motion adjustment mechanism and grinding head. When the macro-motion adjustment mechanism performs large-scale attitude adjustments, the magnetically levitated micro-motion unit above can absorb and isolate high-frequency vibrations in real time, protecting the robot body while providing high-precision constant force floating.

[0032] Example 2 In this embodiment, the base platform 1 includes a top plate, a bottom plate, and multiple side plates connected to the top plate. The upper end of the top plate is rigidly connected to the end flange of the industrial robot by bolts. The bottom plate has a central through hole for the intermediate floating platform 5 to float up and down, and multiple mounting slots for mounting the magnetic levitation stator are evenly distributed around the central through hole. Each side plate has a sliding groove on its center-facing side for the intermediate floating platform to float up and down (see...). Figure 3 A wiring hole is also provided around the outer ring of the central through hole.

[0033] The intermediate floating platform includes a floating mounting platform 501 and a connecting shaft 503 located at the center of the floating mounting platform 501. Sliding extensions 502, matching the sliding grooves, are evenly arranged around the floating mounting platform. The connecting shaft 503 is fixed to the floating mounting platform 501 via a bushing and a key. The connecting shaft moves synchronously with the floating mounting platform. An elastic compensation unit 2 is fitted between the upper part of the connecting shaft 503 and the lower surface of the top plate of the base platform 1. The upper end of the elastic compensation unit 2 is fixed to the top plate. The distance between the upper end of the connecting shaft and the top plate is not less than a set macroscopic movement distance. The lower end of the elastic compensation unit 2 is fixed to the floating mounting platform. The lower end of the connecting shaft 503 passes through a central through-hole in the bottom plate of the base platform and connects to the macroscopic adjustment mechanism. A baffle 504 is provided at the lower end of the connecting shaft 503 to prevent the lower end from passing through the bottom plate of the base platform.

[0034] The magnetic levitation stator 3 is fixed in the corresponding mounting slot on the bottom plate of the base platform 1; the magnetic levitation mover 4 is located above the magnetic levitation stator 3 and is fixedly connected to the intermediate floating platform 5. The magnetic levitation mover and the magnetic levitation stator are opposite poles facing each other, generating electromagnetic attraction. The elastic compensation unit 2 is coaxially installed with the connecting shaft of the intermediate floating platform. Its upper end is hung on the lower surface of the top plate of the base platform 1, and its lower end is fixed to the intermediate floating platform 5, providing tensile elasticity to counteract the electromagnetic attraction. In the absence of electromagnetic force, the elastic compensation unit 2 pulls the intermediate floating platform 5 and the components below it (the magnetic levitation mover 4, the macro-motion adjustment mechanism, and the components connected to the macro-motion adjustment mechanism) toward the top plate of the base platform 1, keeping the magnetic levitation mover and the magnetic levitation stator away from each other and avoiding collision.

[0035] Active power output principle: The magnetically levitated stator 3 is fixed to the upper surface of the base plate of the base platform 1, and the magnetically levitated mover 4 is fixed to the lower surface of the floating mounting platform of the intermediate floating stage 5. When grinding is required, the controller provides an excitation current to the magnetically levitated stator 3, causing the magnetically levitated mover to generate a downward electromagnetic attraction. The force balance equation of the device is: (Assuming forward polishing, the direction is defined as follows) Figure 1 (The middle downwards is positive). Among them... To provide the grinding force applied to the workpiece. The upward pulling force of the spring. It is gravity.

[0036] Therefore, it can be seen that by adjusting the electromagnetic attraction force It can actively adjust the output force. When grinding upside down (workpiece on top), gravity... Reverse, electromagnetic attraction The direction is upward; at this point, simply increase the electromagnetic attraction. By overcoming gravity and spring force, the grinding head can be suctioned upwards to the workpiece surface for processing. This realizes the function of using electromagnetic attraction as an active grinding force source.

[0037] Stiffness matching settings: Assume the reference constant force required by the actual grinding process is... The magnetic levitation rotor and stator are composed of permanent magnets on one side and electromagnets on the other. The total weight of the magnetic levitation rotor 4 and its lower components is... The preset optimal linear balance air gap is When the current is zero, finite element simulation shows that the electromagnetic attraction model approximately satisfies... ,in Let be the magnetic constant. Therefore, the displacement negative stiffness of the electromagnetic attraction at the equilibrium point is calculated as: To prevent engagement instability, the total linear stiffness coefficient of the elastic compensation unit 2 selected in this embodiment is... Configured to have a negative stiffness greater than the electromagnetic attraction force displacement. ,Right now The system's composite stiffness is positive. Therefore, the elastic compensation unit in the device provides a constant positive stiffness bias, which ensures that the system is self-stabilizing and can prevent the occurrence of engagement instability without the intervention of a controller.

[0038] Example 3 In this embodiment, the intermediate floating platform 5 serves as an intermediate connector, and its installation position in the height direction is controlled by the range of action of the magnetic levitation stator and magnetic levitation mover in the magnetic levitation micro-motion unit. A macro-motion attitude adjustment mechanism is installed below the intermediate floating platform 5. The macro-motion attitude adjustment mechanism includes pneumatic actuators 7, a connecting plate 6, and a transition plate 10. This mechanism has three pneumatic actuators 7, which are arranged in parallel, comprising three pneumatic actuators 7 evenly distributed along a 120° circumference. The upper cylinder end of the pneumatic actuator 7 is hinged to the connecting plate 6 via a Hooke hinge to limit the rotation of the pneumatic actuator around its own axis and prevent air entanglement; the lower end of the piston rod is connected downwards to the transition plate 10 via a ball joint. This connection method of upper Hooke hinge and lower ball joint forms a three-parallel motion mechanism, driving the lower components to perform a wide range of axial extension and angular deflection.

[0039] The pneumatic actuator is a low-friction cylinder, with its upper end mounted on the connecting plate 6 via a Hooke hinge and its lower end connected to the transition plate 10 via a ball hinge.

[0040] The six-dimensional force sensor 8 is installed at the end of the macro-motion attitude adjustment mechanism, and the working unit 9, including the grinding head, is installed below the six-dimensional force sensor 8.

[0041] The magnetic levitation stator 3 and magnetic levitation mover 4 use high-efficiency electromagnets, but in order to reduce energy consumption, one of them can be replaced with a high-magnetic permanent magnet.

[0042] In this embodiment, three sets of magnetically levitated stators 3 and magnetically levitated movers 4 are evenly distributed around the circumference to balance the forces and reduce the heat generated by a single combination.

[0043] Example 4 In this embodiment, three eddy current or Hall sensors are evenly distributed at the center or around the periphery of the magnetic levitation stator to calculate the displacement of the intermediate floating platform 5. The macro-motion attitude adjustment mechanism is connected in series with a precision electric proportional valve to control the air circuit; The top and bottom plates of the base platform adopt a hexagonal structure, which is formed by alternating short and long sides. The three long sides are of equal length and the three short sides are of equal length. Side plates are installed on the short sides.

[0044] Example 5: Implementation of Macro-Micro Cooperative Control Method like Figure 3 As shown, the control method in this embodiment includes the following logic: Assuming the robot is polishing a wind turbine blade, a constant target normal force is set. .

[0045] 1. Maintaining the linear operating region: Through pre-calibration, it was determined that under constant current conditions, the region in this embodiment where the rate of change of the slope of force with displacement is less than 30% is the "linear operating region," and the air gap range is set as follows: During the grinding process, if the workpiece surface gradually bulges, the grinding head and the intermediate floating platform will be displaced upwards by the reaction force. This will cause the magnetically levitated mover to move away from the magnetically levitated stator, resulting in air gap expansion and the normal force detected by the six-dimensional force sensor 6. As the low-frequency components increase, and the displacement sensor (such as a Hall sensor, not shown in the figure) detects the air gap expanding to... This exceeds the linear range. The controller calculates that the air gap and workpiece surface deviation total [value missing]. The three pneumatic actuators 7 of the macro-motion attitude adjustment mechanism are instructed to generate synchronous contraction displacement. , These represent the retraction displacements of the three pneumatic actuators. The retraction of the macro-motion adjustment mechanism reduces the clamping force of the grinding head on the workpiece, thereby reducing the upward reaction force on the intermediate floating platform. This causes the intermediate floating platform 5 and the magnetically levitated mover 4 to return to their downward position under electromagnetic attraction, pulling the air gap between the magnetically levitated stator 3 and the magnetically levitated mover 4 back to the linear operating region. At this point, the electromagnetic coil operates again in the region with the flattest characteristic, and only minor current adjustments are needed to eliminate the remaining high-frequency force error.

[0046] 2. Zero-torque attitude calculation: Assuming that the grinding disc is in contact on one side during the grinding process, the six-dimensional force sensor 8 detects the torque around the Y-axis. The controller uses a contact stiffness model to calculate the required rotation of the end of the transition disk around the Y-axis (the axial direction of the device). According to the inverse solution of the parallel mechanism, this rotation is achieved by the controller controlling three pneumatic actuators 7, specifically by extending any one pneumatic actuator while the other two retract. This continues until the normal to the grinding disc coincides with the normal to the workpiece surface. Converging to 0, blind bonding is achieved.

[0047] 3. High-Frequency Constant Force Suppression Active Output: With the macro-motion attitude adjustment mechanism maintaining the air gap and attitude, the high-frequency components (caused by cutting texture and machine tool vibration) in the force signal detected by the six-dimensional force sensor 8 are extracted. The controller adjusts the excitation current of the magnetic levitation stator 3 coil. Since the air gap is now locked in the optimal linear region, the relationship between current and force is approximately linear. The controller can precisely adjust the electromagnetic force with an extremely high response bandwidth. Utilizing the rapid response characteristics of electromagnetic attraction, it serves as an active force source to provide a reference clamping force, and simultaneously quickly suppresses high-frequency force fluctuations caused by cutting texture, eliminating high-frequency force errors and achieving high-quality constant force grinding.

[0048] Example 6: Modular variant with adjustable parameters To accommodate grinding tools of varying weights, such as replacing sandpaper discs with heavy-duty grinding wheels, this embodiment improves the elastic compensation unit. A stiffness adjustment mechanism (not shown) connected to the elastic compensation unit 2 is installed on the top plate of the base platform. This adjustment mechanism employs a threaded lifting structure. By rotating the adjusting ring, the axial position of the upper hanging point of the elastic compensation unit 2 is changed, thereby altering the initial elongation of the tension spring without changing the overall height of the device. When replacing with a heavier grinding head, rotating the adjusting ring increases the initial elongation of the tension spring, increasing its upward pulling force. This re-establishes the balance equation of elastic force + new gravity = attraction in the non-contact suspension state without changing the air gap of the magnetic levitation system. This gives the device wide load adaptability without requiring replacement of the spring hardware.

[0049] Example 7: Predictive Control with Model Feedforward This embodiment proposes a method to further improve performance. Using the point cloud data of the 3D model of the workpiece being ground, or point cloud data generated by a line laser profilometer or structured light camera, the rate of change of the surface normal vector is obtained. Before the grinding head reaches the curvature abrupt change point, the host computer, based on the current position coordinates of the grinding head and the feed velocity vector, searches forward along the planned path in the model to predict the change in the normal vector and curvature of the workpiece surface at the next moment. It calculates the tilt angle and displacement of the macro-motion attitude adjustment mechanism required to maintain normal alignment and adds them as feedforward quantities to the control loop, sending commands to the three pneumatic actuators in advance to initiate their operation. This dual control architecture of "model feedforward + torque feedback" can fundamentally eliminate the instantaneous force impact caused by the lag of the mechanical system, theoretically achieving a near-perfect constant force tracking effect.

[0050] Example 8 The macro-micro collaborative control method in this embodiment includes the following steps: S1 signal decoupling: Acquire six-dimensional force sensor signals (capable of simultaneously measuring three force components (Fx, Fy, Fz) and three torque components (Mx, My, Mz)), extract low-frequency profile force signals through a low-pass filter (cutoff frequency usually set to 5-8Hz), extract high-frequency force error signals through a high-pass filter (cutoff frequency set to 10~12Hz), and directly read the torques around the X and Y axes output by the sensor as contact torque signals; S2 Zero Torque Attitude Calculation: Based on the contact torque signal, the required tilt angle correction of the intermediate floating platform is calculated through the contact stiffness model and converted into asynchronous differential extension commands of each pneumatic actuator in the macro-motion attitude adjustment mechanism to drive the intermediate floating platform to deflect until the contact torque converges to the preset threshold range. S3 Linear Zone Maintenance Control: Based on the low-frequency contour force signal, control each pneumatic actuator in the macro-motion attitude adjustment mechanism to perform synchronous common mode expansion and contraction, and compensate for the macro-contour undulation of the workpiece surface in real time, so that the magnetic levitation mover of the magnetic levitation micro-motion unit is always maintained within the preset linear balance air gap range. S4 High-Frequency Constant Force Suppression and Active Output: Under the premise that the magnetic levitation micro-motion unit is maintained within the linear balance air gap range, the excitation current of the electromagnetic drive component is adjusted based on the high-frequency force error signal to suppress high-frequency cutting vibration. At the same time, the high-frequency constant force output is achieved by controlling the magnitude of the electromagnetic attraction force of the magnetic levitation stator on the magnetic levitation mover.

[0051] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that terms such as “comprising / including” or “having” specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0053] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0054] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. A posture-adaptive constant-force grinding device based on macro-micro coordination and elastic compensation, characterized in that, The device includes: The base platform is configured to be rigidly connected to the end flange of the industrial robot, serving as the mounting base for the device. The magnetic levitation micro-motion unit, connected between the base platform and the intermediate floating platform, includes a magnetic levitation stator fixed to the base platform, a magnetic levitation mover fixed to the intermediate floating platform, and an electromagnetic drive assembly; the electromagnetic attraction between the magnetic levitation stator and the magnetic levitation mover is configured as an active control variable to drive the intermediate floating platform to perform axial micro-motion and force output relative to the base platform; An elastic compensation unit is disposed between the base platform and the intermediate floating platform and is configured to provide an elastic pulling force pointing away from the workpiece; the direction of the elastic pulling force is opposite to the direction of the electromagnetic attraction force; the linear stiffness coefficient of the elastic compensation unit is configured to be greater than the absolute value of the displacement negative stiffness coefficient at the preset balance air gap of the electromagnetic drive assembly; at the same time, by utilizing the combined effect of the adjustable electromagnetic attraction force and the elastic force, the electromagnetic attraction force is converted into an adjustable grinding clamping force; The intermediate floating platform is located above the magnetic levitation micro-motion unit and is suspended and supported by the magnetic levitation micro-motion unit and the elastic compensation unit. The macro-motion attitude adjustment mechanism is used to realize the axial large stroke extension and deflection attitude adjustment movement relative to the intermediate floating platform. It is installed below the intermediate floating platform and includes multiple pneumatic actuators evenly distributed in the circumferential direction, a connecting plate for connecting the upper end of all pneumatic actuators to the intermediate floating platform, and a transition plate for connecting the lower end of all pneumatic actuators to the six-dimensional force sensor. A six-dimensional force sensor is installed below the transition plate of the macro-motion attitude adjustment mechanism to detect the grinding contact normal force and tangential torque; The working unit, connected to the input end of the six-dimensional force sensor, includes a grinding head for the final grinding operation.

2. The attitude-adaptive constant force grinding device based on macro-micro coordination and elastic compensation according to claim 1, characterized in that, The lower ends of each pneumatic actuator are connected by flexible connectors and converge to the lower transition plate, forming a multi-degree-of-freedom parallel mechanism.

3. The attitude-adaptive constant force grinding device based on macro-micro coordination and elastic compensation according to claim 1, characterized in that, The base platform includes a top plate, a bottom plate, and multiple side plates connected to the top plate. The upper end of the top plate is rigidly connected to the end flange of the industrial robot by bolts. The bottom plate has a central through hole for the intermediate floating platform to float up and down. Multiple mounting slots for installing magnetic levitation stators are evenly distributed around the central through hole. Each side plate has a sliding groove for the intermediate floating platform to float up and down on the side facing the center.

4. The attitude-adaptive constant force grinding device based on macro-micro coordination and elastic compensation according to claim 3, characterized in that, The intermediate floating platform includes a floating mounting platform and a connecting shaft located at the center of the floating mounting platform. Sliding extensions matching the slide grooves are evenly arranged around the floating mounting platform. The connecting shaft is fixed to the floating mounting platform in the middle by a bushing and a key. The connecting shaft moves synchronously with the floating mounting platform. An elastic compensation unit is sleeved between the upper part of the connecting shaft and the lower surface of the top plate of the base platform. The upper end of the elastic compensation unit is fixed to the top plate. The distance between the upper end of the connecting shaft and the top plate is not less than the set macroscopic movement distance. The lower end of the elastic compensation unit is fixed to the floating mounting platform. The lower end of the connecting shaft passes through the middle through hole of the bottom plate of the base platform and is connected to the macroscopic attitude adjustment mechanism. The elastic compensation unit includes at least one tension spring.

5. The attitude-adaptive constant force grinding device based on macro-micro coordination and elastic compensation according to claim 4, characterized in that, A baffle is provided at the lower end of the connecting shaft; At the top plate of the base platform, a stiffness adjustment mechanism connected to the elastic compensation unit is provided. The stiffness adjustment mechanism adopts a threaded lifting structure. By rotating the adjustment ring, the axial position of the upper hanging point of the elastic compensation unit is changed, thereby changing the initial elongation of the tension spring without changing the overall height of the device. When a heavier grinding head is replaced, rotating the adjustment ring increases the initial elongation of the tension spring, thereby increasing the upward pulling force it generates. Thus, without changing the working air gap of the magnetic levitation, the balance equation of elastic force + new gravity = attraction force in the non-contact suspension state is re-established.

6. The attitude-adaptive constant force grinding device based on macro-micro coordination and elastic compensation according to claim 4, characterized in that, In the absence of electromagnetic force, the elastic compensation unit pulls the intermediate floating platform and the lower components toward the top plate of the base platform, causing the magnetic levitation mover and magnetic levitation stator to move away from each other. When polishing is required, the controller applies an excitation current to the magnetically levitated stator, causing the magnetically levitated mover to generate a downward electromagnetic attraction. The force balance equation of the device is: ; in To provide the grinding force applied to the workpiece. The upward pulling force of the spring. For gravity; By adjusting the electromagnetic attraction force Actively adjust output force ; When grinding upside down (workpiece on top), gravity... Reverse, electromagnetic attraction The direction is upward; at this point, simply increase the electromagnetic attraction. It overcomes gravity and spring force, thus enabling the grinding head to be sucked upwards onto the workpiece surface for processing; When the macro-motion attitude adjustment mechanism performs a wide range of attitude adjustments, the magnetic levitation micro-motion unit above can absorb and isolate high-frequency vibrations in real time, protecting the robot body while providing high-precision constant force floating.

7. The attitude-adaptive constant force grinding device based on macro-micro coordination and elastic compensation according to claim 4, characterized in that, The magnetically levitated rotor and stator are composed of permanent magnets on one side and electromagnets on the other. The macro-motion attitude adjustment mechanism has three pneumatic actuators. The upper cylinder end of the pneumatic actuator is hinged to the connecting plate through a Hooke hinge to limit the rotation of the pneumatic actuator around its own axis and prevent air circuit entanglement. The lower end of the piston rod is connected to the transition plate downward through a ball hinge to drive the lower component to perform a wide range of axial extension and angular deflection.

8. The attitude-adaptive constant force grinding device based on macro-micro coordination and elastic compensation according to claim 4, characterized in that, Three eddy current or Hall sensors are evenly distributed at the center or around the circumference of the magnetic levitation stator to calculate the displacement of the intermediate floating platform. The macro-motion attitude adjustment mechanism is connected in series with a precision electric proportional valve to control the air circuit; The electromagnetic attraction model F of the electromagnetic drive component approximately satisfies ,in is the magnetic constant. For air gap; the linear stiffness coefficient of the elastic compensation unit Satisfies the stability inequality: ,in The preset optimal linear balance air gap.

9. A posture-adaptive constant force grinding control method based on macro-micro coordination and elastic compensation, characterized in that, The control method employs the apparatus described in any one of claims 1-8, and includes the following steps: S1 signal decoupling: Acquire the six-dimensional force sensor signal, extract the low-frequency contour force signal through the low-pass filter, extract the high-frequency force error signal through the high-pass filter, and directly read the torque around the X-axis and Y-axis output by the sensor as the contact torque signal. S2 Zero Torque Attitude Calculation: Based on the contact torque signal, the required tilt angle correction of the intermediate floating platform is calculated through the contact stiffness model and converted into asynchronous differential extension commands of each pneumatic actuator in the macro-motion attitude adjustment mechanism to drive the intermediate floating platform to deflect until the contact torque converges to the preset threshold range. S3 Linear Zone Maintenance Control: Based on the low-frequency contour force signal, control each pneumatic actuator in the macro-motion attitude adjustment mechanism to perform synchronous common mode expansion and contraction, and compensate for the macro-contour undulation of the workpiece surface in real time, so that the magnetic levitation mover of the magnetic levitation micro-motion unit is always maintained within the preset linear balance air gap range. S4 High-Frequency Constant Force Suppression and Active Output: Under the premise that the magnetic levitation micro-motion unit is maintained within the linear balance air gap range, the excitation current of the electromagnetic drive component is adjusted based on the high-frequency force error signal to suppress high-frequency cutting vibration. At the same time, the high-frequency constant force output is achieved by controlling the magnitude of the electromagnetic attraction force of the magnetic levitation stator on the magnetic levitation mover.

10. The control method according to claim 9, characterized in that, The cutoff frequency of the low-pass filter is set to 5-8Hz; the cutoff frequency of the high-pass filter is set to 10-12Hz. Using the point cloud data of the 3D model of the workpiece being ground, or by installing a line laser profilometer or structured light camera to generate point cloud data, the rate of change of the normal vector of the surface is obtained. Before the grinding head reaches the curvature change point, the host computer searches forward along the planned path in the model according to the current position coordinates of the grinding head and the feed speed vector, predicts the change of the normal vector and curvature of the workpiece surface at the next moment, calculates the tilt angle and displacement of the macro-motion attitude adjustment mechanism required to maintain normal alignment, and adds them to the control loop as feedforward quantities, sending commands to multiple pneumatic actuators in advance to start action.

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