A double-acting curved surface part normal vector tracking presser foot device and detection method

Abstract

The present invention discloses a double-acting curved surface part normal vector tracking pressing foot device and a detection method, which include a curved surface normal automatic detection unit, a multi-degree-of-freedom support reset unit, a force sensing detection unit, a chip suction and discharge unit, and an intelligent displacement detection unit; this device has a normal vector tracking detection function and a pressure detection function, and can ensure the accuracy of the processed hole positions of large thin-walled parts of aviation curved surfaces, improving the machining stability and the degree of automation of the machining process. The advantages of the present invention are as follows: it has multiple functions such as normal vector detection, force and displacement sensing monitoring, and chip suction and discharge at the same time, with a high degree of integration; the normal vector detection device has a double-acting function and is applicable to tracking different machining stages. The present invention has a high degree of integration and diverse functions, and can meet the accuracy requirements for hole-making normal vector detection, as well as the requirements for machining stability and intelligence.

Description

Technical Field

[0001] The present invention relates to the field of end effector surface machining, and particularly relates to a dual-acting surface part normal vector tracking pressing foot device and a detection method. Background Art

[0002] During the process of machining holes on the end effector of a robot for large curved thin-walled parts represented by large aircraft skins, problems such as stress concentration and increased coaxiality deviation often occur due to the non-coincidence of the hole-making direction and the surface normal of the curved surface. At the same time, when machining composite material curved surfaces, delamination and increased burrs on the inner wall of the fixed hole connection will occur, seriously affecting the assembly accuracy of aircraft assembly.

[0003] The existing methods for detecting the normal vector of the end effector are summarized as follows: Laser displacement sensor devices are symmetrically and obliquely arranged along the tool axis, the laser beam is emitted to the workpiece surface, and the normal vector is calculated by algorithm fitting; Laser displacement sensor devices are evenly arranged along the axis, and the laser beam is parallel to the axis. The laser beam is emitted to a circular baffle, and plane fitting is performed through the deflection of the baffle, and the normal vector is detected indirectly.

[0004] However, the dimensions of aerospace thin-walled parts are large and uneven deformation is likely to occur during machining. Using the method of directly measuring the surface normal vector of the curved surface part will be blocked by the pressing device and it is difficult to effectively monitor and feedback the normal vector of the deformed hole position. At the same time, due to the relatively scattered structural arrangement positions of the current actuator to realize the functions of each part, when facing large curved thin-walled parts with a small curvature, due to the influence of size and the assembly accuracy between components, the transmission error is too large and the accuracy of normal vector detection is not high. The present invention adopts the arrangement method that sensors are evenly distributed around the deflection center and the laser beams intersect radially at the deflection center. At the same time, the sensors can realize the position conversion between workstations through a flipping structure; with the adjustment of the deflection angle, the measurement method of the normal vector also realizes the conversion between indirect measurement and direct measurement, and the structures related to normal vector detection in the present invention adopt an integrated design. The advantages of this are:

[0005] 1. The normal vector detection function of this device is applicable to different machining stages: Before machining, the laser emitter is flipped to workstation 1, and the normal vector is solved by laser point plane fitting and compared with the normal vector of the digital model machining area to determine the machining area; During machining, the laser emitter is flipped to workstation 2 for normal vector detection and monitoring during machining deformation.

[0006] 2. When machining, the laser emitter is located at workstation 2, and the indirect detection of the normal vector is realized through the algorithm of fitting the deflection curve of the pressing foot, effectively avoiding the problem of difficult normal vector detection of the curved surface part during machining caused by uneven deformation and mechanism occlusion problems.

[0007] 3. The component structure involving normal vector detection adopts an integrated design method. Moreover, this device simultaneously has functions such as normal vector detection, machining axial force detection, chip suction and discharge, displacement detection, and monitoring, effectively improving the overall integration of the presser foot device and reducing the unnecessary increase in normal vector measurement errors caused by the dispersion of the functional structures of each part, the over-large overall size, and the error transmission between components. Summary of the Invention

[0008] The purpose of the present invention is to provide a double-acting curved surface part normal vector tracking presser foot device and detection method to solve the problems mentioned in the above background technology, such as the low integration of the curved surface normal vector detection presser foot device, the difficulty in normal vector feedback of machining deformation, and the large measurement errors caused by the low degree of part integration and the relatively large overall size.

[0009] To achieve the above purpose, the technical solution of the present invention includes a curved surface normal automatic detection unit, a multi-degree-of-freedom support and reset unit, a force sensing detection unit, a chip suction and discharge unit, and an intelligent displacement detection unit. The curved surface normal automatic detection unit includes a press nose rotating table, a laser emitter 1, an annular base, a laser emitter 2, a press nose, a laser emitter 3, a deflection support base, a station conversion device, an angle adjustment and locking device, and a rotating fixing plate. The press nose rotating table includes a hinge seat mounting hole, a laser receiving cylindrical surface, a deflection ball pair, a transition stepped surface, and a hinge seat mounting boss. The annular base includes a stiffness-enhancing through hole, a base fixing through hole, a laser emitter mounting hole, a ball pair mounting boss, an external thread joint ball pair mounting hole, and a laser emitter mounting rib plate. The multi-degree-of-freedom support and reset unit includes a double-earring type hinge seat, a short hinge pin, a shaft end fixing component, a hinge connecting rod, a flexible adjustment compression component, a deflection connecting rod, a lock washer connecting component, a lock washer fixing component, an external thread joint ball pair, a long hinge pin, a flexible system mounting seat, a lock washer cover, and a movable ball pair. The force sensing detection unit includes a ball pair mounting surface, an axial force transmission surface, a pressure detection device, a sensing pressure plate, a detection device mounting groove, and a positioning pin shaft. The chip suction and discharge unit includes a chip suction protective cover, a chip suction cavity, a positioning chip suction pipe, a chip suction pipe locking mechanism, a telescopic chip suction pipe, a chip suction pipe fixing component, and a chip suction cavity mounting component. The chip suction cavity includes a chip suction groove, a hollow cavity, a chip breaking flow channel, and a chip suction cavity mounting hole. The displacement measurement unit includes a base, a cylinder feedback baffle, a laser displacement emitter, and a mounting rib plate.

[0010] Preferably, the automatic surface normal detection unit is characterized in that: the annular base is located at the bottom of the automatic surface normal detection unit, with a circular ring shape and extending 3 mounting rib plates. The annular base plays a role in support and installation. The laser emitter is installed on the rib plate of the annular base through the laser emitter mounting hole. The nose pressing rotary table is an integral stepped rotary body, and the stepped shaft diameter gradually increases from bottom to top and finally extends 3 hinge seat mounting bosses. A pair of hinge seat mounting holes are opened in the center of the mounting boss for the installation of the double-earring type hinge seat. The laser receiving cylindrical surface plays a role in receiving the laser and causing changes in the laser beam displacement parameters during deflection. The transition stepped surface plays a role in size transition and reducing the length of the overhanging end. The deflection ball pair is installed in the nose pressing rotary table by interference fit, and the axial pressure is transmitted through the contact between the bottom of its inner ring and the axial force transmission surface. The laser emitters 1, 2, and 3 are vertically distributed in a circumferential array at intervals of 120° around the center of the circle, and the laser beams point radially towards the tool axis. The laser beams are emitted onto the laser receiving cylindrical surface. The laser emitter is installed on the deflection support base through the rotary fixing plate, and the flipping of the laser emitter is realized through the rotating pair. When the laser emitter is in the working position 1 state, the flipping angle is 0°, and the three laser beams are emitted towards the workpiece along the tool axis direction. When the laser emitter is in the working position 2 state, the flipping angle is 90°, and the laser beam is emitted radially towards the laser receiving cylindrical surface, and its laser extension line converges at the center of the deflection ball pair. The angle adjustment locking device realizes the positioning and locking of the flipping angle of the laser emitter through the cooperation and friction of the surface micro-convex cylinder. When the nose pressing deflects, the normal vector direction and deflection angle of the curved surface part are calculated through a normal vector detection method. The nose pressing is a rotary body, with a U-shaped groove opened around the top for chip discharge, and a countersunk threaded hole opened at the bottom of the groove for connection with the nose pressing rotary table. The top end of the nose pressing converges inward to form an arc surface to adapt to the shape of the workpiece curved surface.

[0011] Preferably, the annular base is characterized in that: the number of laser emitter mounting ribs is 3, which are circumferentially arrayed around the center of the circle at intervals of 120° from each other for mounting and fixing the laser emitter. The ribs are arranged parallel to the radial direction, and the distance from the radial direction is the eccentricity e, which enables the laser beam of the laser emitter to be directly aimed at the center of the cross-section. The number of stiffness-enhancing through-holes is 3 pairs, 6 in total, which are evenly distributed in a circular shape in the center of the 3 ribs for enhancing the mounting stiffness of the ribs. The number of laser emitter mounting holes is 3 pairs, 6 in total, which are evenly distributed in a circular shape on the 3 ribs for mounting three laser emitters. The number of spherical pair mounting bosses is 3, which are rectangular-shaped protrusions and are circumferentially arrayed around the center of the circle at intervals of 120° between the 3 laser emitter mounting ribs. The number of external-threaded spherical pair mounting holes is 3, which are evenly distributed in the center of the spherical pair mounting bosses for mounting the external-threaded spherical pair. The number of base fixing through-holes is 3, which are circumferentially arrayed around the center of the circle at intervals of 120° from each other for fixing the annular base.

[0012] Preferably, the multi-degree-of-freedom support and reset unit is characterized in that: the hinge link has a Z-shaped outer shape, with an inward depression at the upper end. The hinge holes at the bottom and top are perpendicular to each other and are respectively along the length and width directions of the hinge link, and are connected to the double-earring type hinge seat through a short hinge pin. The flexible system mounting seat is connected to the hinge link through a long hinge pin. The movable spherical pair is installed in the center of the flexible system mounting seat by interference fit. The anti-loosening cover plate is fixed on the flexible system mounting seat through the anti-loosening piece connecting component to prevent the outer ring of the movable spherical pair from loosening. The inner ring of the movable spherical pair has a clearance fit with the deflection connecting rod and can move up and down a certain distance along the deflection connecting rod under the support of the flexible adjustment and compression component. The flexible adjustment and compression component has a certain pre-tightening force to prevent the deviation of the pressure foot in the initial state. The deflection connecting rod is connected to the external-threaded spherical pair by interference fit. The flexible system mounting seat can freely swing at a certain angle around the center of the movable spherical pair in the indicated direction under the action of the movable spherical pair, long hinge pin, and hinge link.

[0013] Preferably, the force sensing unit is characterized in that: the spherical pair mounting surface has a cylindrical outer shape and is in interference fit with the inner ring of the spherical plain bearing, serving as the mounting surface of the inner ring of the spherical plain bearing. The bottom of the inner ring is in contact with the axial force transmission surface. When the pressure foot presses the workpiece, the axial pressure is transmitted through the axial force contact surface, causing the pressure detection device to work. The positioning pin plays a positioning role to ensure the coaxiality of the installation of the front and rear parts.

[0014] Preferably, the chip suction and discharge unit is characterized in that: the chip suction protective cover is in the shape of a semi-circular arc connection with different diameters, hollow at the bottom, and the thickness of the surrounding cover wall is smoothly transitioned from thick to thin by a fillet. A circular through-hole is opened in the center of the top to place the pressure nose. A concentric hollow boss is provided on one side of the small arc, and a groove is provided on one side. The telescopic chip suction pipe is installed on the boss through the chip suction pipe fixing component. The two ends of the positioning chip suction pipe are circular arc positioning surfaces, and the middle is connected by a hollow rectangular pipe. There are double-ear mounting holes on both sides of the bottom, and the positioning chip suction pipe is installed on the chip suction protective cover through the chip suction pipe locking mechanism. The outer contour of the chip suction cavity is a stepped rotating body, which is divided into an inner ring and an outer ring through a hollow cavity. The inner ring is provided with 4 U-shaped grooves, evenly distributed around the center of the circle. The outer ring is provided with 1 chip suction groove, directly opposite to the U-shaped groove of the inner ring, and is fixedly connected to the chip suction protective cover through the chip suction cavity mounting hole. The number of the chip suction cavity mounting holes is 3, evenly distributed around the center of the circle.

[0015] Preferably, the intelligent displacement detection unit is characterized in that: an installation rib plate is installed on one side of the front end of the bottom of the base. The laser displacement transmitter is fixedly connected to the lower side of the installation rib plate through a thread. The laser beam is along the axis direction of the main shaft and close to one side of the main shaft. The laser displacement transmitter judges the distance between the pressure foot device and the workpiece when feeding by emitting a laser beam to the workpiece, and then controls the feeding speed of the pressure foot device, reducing the impact when the pressure foot device contacts the workpiece and the impact deformation of the curved surface part. A cylinder stroke feedback baffle is installed on the other side of the bottom of the base, and a length meter is installed on the side of the actuator behind it. When the pressure foot device moves under the push of the cylinder, the movement displacement is detected through the expansion and contraction of the spring as a feedback signal to form a closed-loop control with the movement of the cylinder.

[0016] Preferably, a method for detecting the normal vector of the machining area of the end effector for curved surface hole making before machining is characterized in that when in station 1, it includes the following steps:

[0017] Step 1: Keep the laser beam emitting towards the workpiece side;

[0018] Step 2: The robotic arm drives the pressure foot device to move to the set machining position according to the pre-set offline program;

[0019] Step 3: Set three laser points as C1, C2, and C3 respectively, and set the lengths of the three laser beams at this time as ε0, ε1, and ε2. Calculate the spatial positions of the three laser points relative to the robot reference coordinate system according to the change of the readings of the laser transmitter;

[0020] Step 4: Set the plane determined by the three laser points as ε: λ1X + λ2Y + λ3Z = D. Fit the plane equation using the spatial position coordinates of points C1, C2, and C3 and calculate its normal vector ε0;

[0021] Step 5: Compare the calculated normal vector with the normal vector of the machining area digital model. When the included angle between the two is within the threshold allowed by the hole-making accuracy, determine the hole-making machining range; otherwise, adjust the pose of the pressure foot device and recalculate.

[0022] Preferably, in the method for detecting the normal vector of the end effector surface hole-making during machining, when in station 2, it includes the following steps:

[0023] Step 1: Keep the laser beam emitting towards the laser receiving cylindrical surface.

[0024] Step 2: The extension lines of the three laser beams intersect at point O1, and the section determined by the three laser beams is M. Taking point O1 as the origin and the opposite direction of the laser beam emitting direction of the laser emitter 3 as the positive direction of the y1 axis, establish a Cartesian space rectangular coordinate system x1O1y1. The three laser beams are in the same section Inside, the intercepted curve of the laser receiving cylindrical surface in section M is a circle at this time, with a radius of l, and the perpendicular distance from this section to the center O of the spherical pair is H.

[0025] Step 3: Let the intersection points of the laser beam and the cylindrical surface be E, F, and G respectively. Calculate the coordinate positions of points E, F, and G in the coordinate system x1O1y1 at this time as:

[0026]

[0027] Step 4: The pressure foot device feeds, the pressure nose contacts and presses the curved surface part, and the laser receiving cylindrical surface deflects. The axis direction of the deflected laser receiving cylindrical surface is the normal vector direction of the machining hole position of the curved surface part. Let the deflection angle be |Δ| ≤ 5°.

[0028] Step 5: Let the lengths of the laser beams of laser emitters 1, 2, and 3 be d1, d2, and d3 respectively. The intersection points of the deflected laser beam and the cylindrical surface are E1, F1, and G1 respectively, and the distance between the laser beam and point O1 is m. Then the coordinate positions of the deflected E1, F1, and G1 in the coordinate system x1O1y1 are:

[0029]

[0030] Step 6: The intercepted curve of the deflected laser receiving cylindrical surface in section M is an elliptical curve. Let the major axis be a and the minor axis be l. Taking its ellipse center O2 as the coordinate origin, the direction of the major axis of the ellipse and away from point O1 as the positive direction of the x2 axis, and the main axis feed direction as the plane normal, establish a Cartesian plane rectangular coordinate system x2O2y2.

[0031] Step 7: Let the length of the line segment O1O2 be The deflection angle of the x2 axis relative to the x1 axis is θ. Let the coordinate position of point O2 in the coordinate system x1O1y1 be (A, B). Then, tanθ = B / A. According to coordinate transformation, the coordinate transformation relationship between the coordinate systems x1O1y1 and x2O2y2 is According to the principle of coordinate system transformation, the coordinate positions of the intersection points E1, F1, and G1 of the deflected laser beams in the coordinate system x2O2y2 can be calculated;

[0032] Step 8: Establish a system of equations using the coordinate positions of E1, F1, and G1 in the coordinate system x2O2y2 and the relationships between the parameters. Substitute the coordinate positions of E1, F1, and G1 in the coordinate system x2O2y2 into the system of equations to solve for the normal vector direction of the curved surface part and the deflection angle Δ.

[0033]

[0034] Step 9: Use the pressure detection device and the curved surface normal vector automatic detection unit to achieve joint detection of machining deformation. When the machining axial force is too large and the normal vector changes exceed a certain range due to excessive machining deformation, adjust the pressure of the pressure foot and the cutting process parameters and perform normal vector correction;

[0035] Compared with the existing technology, the gain effect of the present invention is: the double-action normal vector detection end effector pressure foot device and detection method for curved surface hole making:

[0036] (1) Integrate functions such as curved surface normal vector detection, chip suction, displacement detection, and axial pressure measurement into the end effector pressure foot device, improving the integration degree of the pressure foot device.

[0037] (2) Optimize the problem of difficult monitoring and feedback of normal vector changes during machining caused by the easy deformation of aerospace curved surface thin-walled parts under the pressure of the pressure foot through indirect measurement;

[0038] (3) The curved surface normal vector automatic detection unit realizes double-action tracking detection of normal vector measurement at two workstations through the work position conversion device;

[0039] (4) The main components of the curved surface normal vector automatic detection unit, such as the annular base and the pressure nose rotating table, are all manufactured integrally, effectively reducing the problem of measurement accuracy decline caused by error transmission between components;

[0040] (5) Multiple ball pairs and rotating pairs are used in the multi-degree-of-freedom support and reset unit, enabling the unit to have deflection degrees of freedom along the radial horizontal, vertical, and axial directions. The flexible adjustment compression component can support and reset the pressure nose when it deflects in any direction;

[0041] (6) The smaller size of the nose press can better fit the surface of the curved part, reducing errors. Moreover, a U-shaped chip evacuation groove is opened around the nose press, which plays an auxiliary role in chip evacuation during processing. Description of the Drawings

[0042] Figure 1 is the overall state schematic diagram of Station 1 of the present invention;

[0043] Figure 2 is the overall state schematic diagram of Station 2 of the present invention;

[0044] Figure 3 is the structural schematic diagram of the automatic curved surface normal detection unit of the present invention;

[0045] Figure 4 is the structural schematic diagram of the nose press turntable of the present invention;

[0046] Figure 5 is the structural schematic diagram of the annular base of the present invention;

[0047] Figure 6 is the structural schematic diagram of the multi-degree-of-freedom support and reset unit of the present invention;

[0048] Figure 7 is the front right axonometric view of the force sensing unit of the present invention;

[0049] Figure 8 is the rear left axonometric view of the force sensing unit of the present invention;

[0050] Figure 9 is the structural schematic diagram of the chip suction and evacuation unit of the present invention;

[0051] Figure 10 is the structural schematic diagram of the chip suction protective cover of the present invention;

[0052] Figure 11 is the structural schematic diagram of the displacement measurement unit of the present invention;

[0053] Figure 12 is the schematic diagram of the normal vector detection principle of Station 1 of the present invention;

[0054] Figure 13 is the schematic diagram of the normal vector detection algorithm principle of Station 2 of the present invention.

[0055] In the figure: 1. Automatic surface normal detection unit; 2. Multi-degree-of-freedom support and reset unit; 3. Force sensing detection unit; 4. Chip suction and discharge unit; 5. Intelligent displacement detection unit; 1-1. Nasal pressing rotary table; 1-2. Laser emitter 1; 1-3. Ring base; 1-4. Laser emitter 2; 1-5. Nasal press; 1-6. Laser emitter 3; 1-7. Deflection support base; 1-8. Station conversion device; 1-9. Angle adjustment and locking device; 1-10. Rotating fixing plate; 1-1-1. Hinge seat mounting hole; 1-1-2. Laser receiving cylindrical surface; 1-1-3. Deflection ball pair; 1-1-4. Transition stepped surface; 1-1-5. Hinge seat mounting boss; 1-3-1. Stiffness enhancement through hole; 1-3-2. Base fixing through hole; 1-3-3. Laser emitter mounting hole; 1-3-4. Ball pair mounting boss; 1-3-5. External thread joint ball pair mounting hole; 1-3-6. Laser emitter mounting rib; 2-1. Double-earring type hinge seat; 2-2. Short hinge pin; 2-3. Shaft end fixing component; 2-4. Hinge connecting rod; 2-5. Flexible adjustment compression component; 2-6. Deflection connecting rod; 2-7. Locking piece connecting component; 2-8. Locking piece fixing component; 2-9. External thread joint ball pair; 2-10. Long hinge pin; 2-11. Flexible system mounting seat; 2-12. Locking cover piece; 2-13. Movable ball pair; 3-1. Ball pair mounting surface; 3-2. Axial force transmission surface; 3-3. Pressure detection device; 3-4. Sensing pressure plate; 3-5. Detection device mounting groove; 3-6. Positioning pin shaft; 4-1. Chip suction protection cover; 4-2. Chip suction cavity; 4-2-1. Chip suction groove; 4-2-2. Hollow cavity; 4-2-3. Chip breaking flow channel; 4-2-4. Chip suction cavity mounting hole; 4-3. Positioning chip suction pipe; 4-4. Chip suction pipe locking mechanism; 4-5. Telescopic chip suction pipe; 4-6. Chip suction pipe fixing component; 4-7. Chip suction cavity mounting component; 5-1. Base; 5-2. Cylinder stroke feedback baffle; 5-3. Laser displacement emitter; 5-4. Mounting rib. Detailed implementation manners

[0056] The object of the present invention is to provide a double-acting surface part normal vector tracking pressing foot device and detection method, so as to solve the problems existing in the above-mentioned prior art and improve the integration degree of the pressing foot device and the accuracy of normal vector detection.

[0057] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the drawings and specific implementation manners.

[0058] As Figure 1-2 shown, the pressing foot device for surface normal detection in this embodiment includes an automatic surface normal detection unit 1, a multi-degree-of-freedom support and reset unit 2, a force sensing detection unit 3, a chip suction and discharge unit 4, and an intelligent displacement detection unit 5. Among them Figure 1Indicates the state of the sensor arrangement at station 1, Figure 2 Indicates the state of the sensor arrangement at station 2.

[0059] Such as Figures 3-5 The surface normal automatic detection unit 1 shown, characterized in that: the annular base 1-3 is located at the bottom of the surface normal automatic detection unit 1, playing the role of supporting and installing the laser emitter and its flipping device, the laser emitter is installed on the laser emitter mounting rib 1-3-6 through the laser emitter mounting hole 1-3-3, three hinge seat mounting bosses 1-1-5 extend from the upper end of the nose pressing turntable 1-1, and a pair of hinge seat mounting holes 1-1-1 are opened in the center for the installation of the double-earring type hinge seat 2-1. The laser receiving cylindrical surface 1-1-2 plays the role of receiving the laser and causing changes in the laser beam displacement parameters during deflection. The transition stepped surface 1-1-4 plays the role of dimension transition and reducing the length of the overhanging end. The inner bottom of the deflection ball pair 1-1-3 transmits the axial pressure through contact with the axial force transmission surface 3-2. The laser emitter is installed on the deflection support base 1-7 through the rotation fixing plate 1-10, and the flipping of the laser emitter is realized through the station conversion device 1-8; the angle adjustment locking device 1-9 realizes the positioning and locking of the laser emitter through surface micro-convex cylinder cooperation and friction. The laser beam points radially to the tool axis, and the laser beam is emitted to the laser receiving cylindrical surface 1-1-2. When the nose pressing piece 1-5 deflects, a method for detecting the normal vector is used to calculate the normal vector direction and deflection angle of the curved surface part. The top of the nose pressing piece 1-5 is provided with a U-shaped groove around it for chip discharge, and converges inward into an arc surface to adapt to the shape of the workpiece curved surface. The bottom of the groove is connected to the nose pressing turntable 1-1.

[0060] Such as Figure 6The multi-degree-of-freedom support and reset unit 2 shown is characterized in that: the hinge link 2-4 is connected to the double-earring hinge seat 2-1 through a short hinge pin 2-2 to form a revolute pair 1, the flexible system mounting seat 2-11 is connected to the hinge link 2-4 through a long hinge pin 2-10 to form a revolute pair 2, the movable spherical pair 2-13 is installed in the center of the flexible system mounting seat 2-11 to form a spherical pair 1 for the adjustment of degrees of freedom, the anti-loosening cover plate 2-12 is fixed on the flexible system mounting seat through an anti-loosening piece connecting component to prevent the outer ring of the movable spherical pair from loosening, the movable spherical pair 2-13 and the deflection connecting rod 2-6 are in clearance fit and can move up and down a certain distance along the deflection connecting rod 2-6 under the support of the flexible adjustment compression component 2-5. The flexible adjustment compression component 2-5 has a certain pre-tightening force to prevent the presser foot from skewing in the initial state and realizes the reset function when the presser foot deflects through tension. The deflection connecting rod 2-6 is connected to the external thread spherical joint pair 2-10 through interference fit to form a spherical pair 2. Finally, under the action of multiple revolute pairs, spherical pairs and the flexible adjustment compression component 2-5, the multi-degree-of-freedom support and reset unit 2 realizes multi-degree-of-freedom deflection and presser foot return reset in space.

[0061] As Figures 7-8 The force sensing unit 3 shown is characterized in that: the force sensing unit 3 is located at the bottom of the curved surface normal automatic detection unit 1, avoiding the problem of inaccurate axial force measurement of the pressure detection device caused by the deflection adjustment of the presser foot and the possible contact of the curved surface. The spherical pair mounting surface 3-1 is in interference fit with the inner ring of the movable spherical pair 2-13, and the bottom of the inner ring is in contact with the axial force transmission surface 3-2. When the presser foot presses the workpiece, the axial pressure is transmitted through the axial force transmission surface 3-2, enabling the pressure detection device 3-3 to work. The positioning pin shaft 3-6 plays a positioning role to ensure the coaxiality of the installation of the front and rear parts.

[0062] As Figures 9-10 The chip suction and discharge unit 4 shown is characterized in that: for the chip suction protective cover 4-1, a circular through-hole is opened in the center of the top to place the pressure nose, a concentric hollow boss is provided on one side of the small arc, and one side is grooved. The telescopic chip suction pipe 4-5 is installed on the boss through the chip suction pipe fixing component 4-7. The two ends of the positioning chip suction pipe 4-3 are circular arc positioning surfaces, and the middle is connected by the hollow positioning chip suction pipe 4-3. There are double-ear mounting holes on both sides of the bottom, and the positioning chip suction pipe 4-3 is installed on the chip suction protective cover 4-1 through the chip suction pipe locking mechanism 4-4. The chip suction cavity 4-2 is divided into an inner ring and an outer ring by the hollow cavity 4-2-3. The inner ring is provided with 4 U-shaped grooves, which are evenly distributed around the center of the circle. The outer ring is provided with 1 chip suction groove, which is directly opposite to the U-shaped groove of the inner ring for the circulation of chips.

[0063] As Figure 11The intelligent displacement detection unit 5 shown is characterized in that: on one side of the front end of the bottom of the base 5-1, there is an installation rib plate 5-4, and the laser displacement transmitter 5-3 is fixed under the installation rib plate. The laser beam is along the main axis direction and close to one side of the main axis. The laser displacement transmitter judges the distance between the presser foot device and the workpiece when feeding by emitting a laser beam onto the workpiece, and then controls the feeding speed of the presser foot device to reduce the impact when the presser foot device contacts the workpiece and the impact deformation of the curved surface part. On the other side of the bottom of the base, there is a cylinder stroke feedback baffle, and a length meter is installed on the side of the actuator behind it. When the presser foot device moves under the push of the cylinder, the movement displacement is detected by the expansion and contraction of the spring as a feedback signal to form a closed-loop control with the movement of the cylinder.

[0064] As Figure 12 shown in the schematic diagram of the normal vector detection at station 1, which specifically includes the following steps:

[0065] Step 1: Keep the laser beam emitting towards the workpiece side;

[0066] Step 2: The robotic arm drives the presser foot device to move to the set machining position according to the pre-set offline program;

[0067] Step 3: Set three laser points as C1, C2, and C3 respectively, and set the lengths of the three laser beams at this time as ε0, ε1, and ε2. Calculate the spatial positions of the three laser points relative to the robot reference coordinate system according to the change in the readings of the laser emitter;

[0068] Step 4: Set the plane determined by the three laser points as ε: λ1X + λ2Y + λ3Z = D. Use the spatial position coordinates of points C1, C2, and C3 to fit the plane equation and calculate its normal vector ε0;

[0069] Step 5: Compare the calculated normal vector with the normal vector of the machining area digital model. When the included angle between the two is within the threshold allowed by the hole-making accuracy, determine the hole-making processing range; otherwise, adjust the pose of the presser foot device and recalculate;

[0070] As Figure 12 shown in the schematic diagram of the normal vector detection at station 2, which specifically includes the following steps:

[0071] Step 1: Keep the laser beam emitting towards the laser receiving cylindrical surface;

[0072] Step 2: The extension lines of the three laser beams intersect at point O1, and the cross-section determined by the three laser beams is M. Taking point O1 as the origin and the opposite direction of the laser beam emission direction of laser emitter 3 as the positive direction of the y1 axis, establish a Cartesian space rectangular coordinate system x1O1y1. The three laser beams are in the same cross-section inside, and the intercepted curve of the laser receiving cylindrical surface in cross-section M at this time is a circle with a radius of l, and the perpendicular distance from this cross-section to the center of the spherical pair O is H;

[0073] Step 3: Let the intersection points of the laser beam and the cylindrical surface be E, F, and G respectively, and calculate the coordinate positions of points E, F, and G in the coordinate system x1O1y1 at this time as follows:

[0074]

[0075] Step 4: The pressing foot device feeds, the pressing nose contacts and presses the curved surface part, and the laser receiving cylindrical surface deflects. The axis direction of the deflected laser receiving cylindrical surface is the normal vector direction of the machining hole position of the curved surface part, and let its deflection angle be |Δ| ≤ 5°;

[0076] Step 5: Let the laser beam lengths of laser emitters 1, 2, and 3 be d1, d2, and d3 respectively. The intersection points of the deflected laser beam and the cylindrical surface are E1, F1, and G1 respectively, and the distance between the laser beam and point O1 is m. Then the coordinate positions of the deflected E1, F1, and G1 in the coordinate system x1O1y1 are:

[0077]

[0078] Step 6: The intercepted curve of the deflected laser receiving cylindrical surface in the section M is an elliptical curve. Let the major axis be a and the minor axis be l. Take its ellipse center O2 as the coordinate origin, the direction of the major axis of the ellipse and away from point O1 as the positive direction of the x2 axis, and the main axis feed direction as the plane normal to establish the Cartesian plane rectangular coordinate system x2O2y2;

[0079] Step 7: Let the length of the line segment O1O2 be The deflection angle of the x2 axis relative to the x1 axis is θ. Let the coordinate position of point O2 in the coordinate system x1O1y1 be (A, B). Then tanθ = B / A. According to the coordinate transformation, the coordinate transformation relationship between the coordinate systems x1O1y1 and x2O2y2 is According to the coordinate system transformation principle, the coordinate positions of the deflected laser beam intersection points E1, F1, and G1 in the coordinate system x2O2y2 can be calculated;

[0080] Step 8: Use the coordinate positions of E1, F1, and G1 in the coordinate system x2O2y2 and the relationships between the parameters to establish a system of equations, and substitute the coordinate positions of E1, F1, and G1 in the coordinate system x2O2y2 into the system of equations to solve the normal vector direction and the deflection angle Δ.

[0081]

[0082] Step 9: Use the pressure detection device and the curved surface normal vector automatic detection unit to jointly detect the machining deformation. When the machining axial force is too large and the normal vector changes exceed a certain range due to excessive machining deformation, adjust the pressure of the pressure foot and the cutting process parameters and perform normal vector correction;

[0083] The working process of this example for the normal vector tracking detection of curved surface hole making is as follows:

[0084] 1. The industrial robot drives the end effector to move close to the curved surface part. The pressure foot device is in the state of station 1. Use the laser emitter to solve the plane normal vector and compare it with the normal vector of the digital model machining area to determine the approximate range of the machining area;

[0085] 2. Assume that the extension lines of the laser beams of laser emitters 1, 2, and 3 intersect at point O1. Take point O1 as the origin and establish a Cartesian space rectangular coordinate system O1-x1y1z1. Assume that the laser emission point of the laser displacement emitter is the origin S. Take the positive directions of the coordinate axes of coordinate system O1 as the coordinate positive directions and establish coordinate system S-rpg. Calculate the coordinate transformation matrix between the two and perform real-time conversion of the axial distance coordinates;

[0086] 3. After determining the machining area, the pushing cylinder of the pressure foot device fast-forwards, pushing the pressure foot device to feed along. However, there will be a certain error in the movement controlled by the cylinder. At this time, the cylinder stroke feedback baffle 5-2 works, detects the displacement of the pressure foot device advancing, and feeds the measured value back to the cylinder through the upper computer, forming a closed-loop control of the pressure foot movement with the cylinder;

[0087] 4. The sensor rotates 90°. The pressure foot device is in the state of station 2. The laser displacement emitter 5-3 detects the distance from the pressure foot device to the workpiece surface and converts it into the distance between the tool tip and the curved surface part along the tool axis through coordinate transformation. When it is detected that the distance between the tool and the workpiece is reduced to 20 mm, the displacement signal is fed back to the cylinder through the upper computer, and the cylinder feeds at a slow speed, and the moving speed of the pressure foot device decreases. The pressure foot feeds slowly, contacts and presses the workpiece tightly. The pressure nose rotating table 1-1 deflects, the length of the laser beam changes, and then the deflection angle and the curved surface normal vector direction are calculated through the above normal vector detection method and fed back to the robot through the upper computer, and the robot adjusts the pose of the end effector to make the tool axis face the hole making normal vector direction;

[0088] 5. The chip suction and discharge unit 4 is started, the electric spindle is started, and the end effector starts hole making machining. The axial force transmission surface 3-2 is pressed tightly, and the pressure detection device 3-3 works to measure the axial pressure of hole making. Part of the debris is discharged through the U-shaped groove of the pressure nose, and most of the debris is sucked into the hollow cavity 4-2-2 through the chip breaking flow channel 4-2-3, and then enters the positioning chip suction pipeline 4-3 through the chip suction groove 4-2-1, and then is sucked out through the telescopic chip suction pipe 4-5;

[0089] 6. The curved surface part is deformed under the action of the nose pressure and the machining reaction force. The deformation is predicted by the real-time feedback of the axial force data of the force sensor, and the real-time analysis of the hole position normal is carried out by the curved surface normal automatic detection unit. When the comprehensive influence value of the two exceeds a certain range, the pressure of the pressure foot and the cutting process parameters are adjusted and re-aligned;

[0090] The content not described in detail in this specification belongs to the prior art well known to those skilled in the art.

[0091] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A double-acting curved surface part normal vector tracking presser foot device, characterized in that, It includes a curved surface normal automatic detection unit (1), a multi-degree-of-freedom support and reset unit (2), a force sensing detection unit (3), a chip suction and discharge unit (4), and an intelligent displacement detection unit (5); The curved surface normal automatic detection unit (1) is installed above the intelligent displacement detection unit (5), and includes a nose pressing rotary table (1-1), a station conversion device (1-8), an annular base (1-3), a laser emitter 1 (1-2), a laser emitter 2 (1-4), and a laser emitter 3 (1-6); the laser emitters (1-2), (1-4), (1-6) are evenly distributed around the central axis of the annular base (1-3); when the laser emitter is in the station 1 state, the station conversion device (1-8) is in the initial state, and the three laser beams are emitted toward the curved surface part; when the laser emitter is in the station 2 state, the flipping angle of the station conversion device (1-8) is 90°, and the three laser beams are emitted along the normal direction of the laser receiving cylindrical surface (1-1-2); The nose pressing rotary table (1-1) is connected to the annular base (1-3) through 3 multi-degree-of-freedom support and reset units (2), and is used to press the curved surface part and make it deflect with the curvature of the curved surface part, and serve as the laser beam receiving and measuring reference for station 2; the laser emitter 1 (1-2), the laser emitter 2 (1-4), and the laser emitter 3 (1-6) are installed on the annular base (1-3) through the station conversion device (1-8); the station conversion device (1-8) is used to drive the laser emitter to flip, so as to realize the dual functions of normal vector tracking detection in station 1 and station 2; The multi-degree-of-freedom support and reset unit (2) includes a deflection connecting rod (2-6), an external thread spherical joint pair (2-9), a flexible adjustment compression component (2-5), a flexible system mounting seat (2-11), a hinge connecting rod (2-4), a double-earring type hinge seat (2-1), a movable spherical joint (2-13), and a shaft end fixing component (2-3); the external thread spherical joint pair (2-9) and the movable spherical joint (2-13) are installed on the deflection connecting rod (2-6) to realize the multi-degree-of-freedom movement of the pressing foot device; the flexible system mounting seat (2-11) is connected to the double-earring type hinge seat (2-1) through the hinge connecting rod (2-4); the deflection connecting rod (2-6) is connected to the flexible system mounting seat (2-11) through the movable spherical joint (2-13); the flexible adjustment compression component (2-5) is installed between the shaft end fixing component (2-3) and the movable spherical joint (2-13) for the support and deflection reset of the pressing foot device; The force sensing detection unit (3) is located between the nose pressing rotary table (1-1) and the annular base (1-3), and includes four pressure detection devices (3-3) and a sensing pressure plate (3-4); the four pressure detection devices (3-3) are installed in the grooves below the sensing pressure plate (3-4) for the detection of the machining axial force; The chip suction and discharge unit (4) is installed above the normal automatic detection unit (1), and includes a positioning chip suction pipeline (4-3) and a chip suction cavity (4-2) installed below the chip suction protective cover (4-1); The intelligent displacement detection unit (5) includes a base (5-1), a laser displacement transmitter (5-3), and a cylinder stroke feedback baffle (5-2); the laser displacement transmitter (5-3) is installed on the right side of the base (5-1) for measuring the distance to the curved surface part; the cylinder stroke feedback baffle (5-2) is installed on the left side of the base (5-1) for cylinder stroke feedback.

2. The double-acting curved surface part normal vector tracking presser foot device according to claim 1, characterized in that The annular base (1-3) includes a laser emitter mounting rib plate (1-3-6) and a ball pair mounting boss (1-3-4): the number of the laser emitter mounting rib plates (1-3-6) is 3, which are evenly distributed around the axis of the inner hole of the annular base (1-3), and the perpendicular distance between the laser emitter mounting rib plate (1-3-6) and the axis of the inner hole of the annular base (1-3) is e.

3. The double-acting curved surface part normal vector tracking presser foot device according to claim 1, characterized in that, The multi-degree-of-freedom support and reset unit (2) has a quantity of 3: the movable ball pair (2-13) can slide up and down along the axis on the deflection connecting rod (2-6).

4. The double-acting curved surface part normal vector tracking presser foot device according to claim 1, characterized in that, The chip suction and discharge unit (4) has a through hole in the chip suction protective cover (4-1) connected to the pressure nose (1-5); the chip suction cavity (4-2) is divided into an inner part and an outer part by a hollow cavity (4-2-2), with four U-shaped grooves (4-2-3) provided inside and a chip suction groove (4-2-1) provided outside; the chip suction groove (4-2-1) coincides with one of the inner U-shaped grooves (4-2-3).

5. A detection method for the double-acting curved surface part normal vector tracking presser foot device according to claim 1, characterized in that, When the pressure foot device is in working position 1, the following steps are included: Step 1: Keep the laser beam of the laser emitter emitting towards the curved surface part side. Step 2: The robotic arm drives the pressure foot device to move to the set machining position according to the pre-set offline program. Step 3: Read the spatial position coordinates of three laser points on the curved surface part. Step 4: Use the spatial position coordinates of the three laser points to fit a plane equation and calculate its normal vector. Step 5: Compare the calculated normal vector with the normal vector of the machining area digital model. When the included angle between the two is within the threshold allowed by the hole-making accuracy, determine the hole-making machining range; otherwise, adjust the pose of the pressure foot device and recalculate.

6. The detection method according to claim 5, wherein When the pressure foot device is in working position 2, the following steps are included: Step 1: Keep the laser beam of the laser emitter emitting towards the laser receiving cylindrical surface (1-1-2) side. Step 2: The extension lines of the three laser beams intersect at point O1, and the cross-section determined by the three laser beams is M. Taking point O1 as the origin, establish a Cartesian plane coordinate system x1O1y1. Step 3: Assume that the intersection points of the laser beams and the laser receiving cylindrical surface (1-1-2) are E, F, and G respectively, and calculate the initial coordinate positions of points E, F, and G in x1O1y1. Step 4: The pressure foot device feeds, and the laser receiving cylindrical surface (1-1-2) deflects. The axis direction of the deflected laser receiving cylindrical surface (1-1-2) is the normal vector direction of the machining hole position of the curved surface part. Step 5: Obtain the coordinate positions of the deflected laser beam intersection points E1, F1, and G1 in x1O1y1. Step 6: The contour shape of the deflected laser receiving cylindrical surface (1-1-2) in the laser beam cross-section M is an elliptical curve. Taking its ellipse center O2 as the coordinate origin, establish a Cartesian plane rectangular coordinate system x2O2y2. Step 7: Calculate the coordinate positions of the intersection points E1, F1, and G1 of the deflected laser beam in x2O2y2 through the coordinate transformation matrix of the coordinate systems x1O1y1 and x2O2y2; Step 8: Establish a system of equations using the coordinate positions of E1, F1, and G1 in x2O2y2 and the geometric position relationships between the parameters, and then the normal vector direction of the curved surface part and the deflection angle Δ can be solved; Step 9: Use multi-sensor fusion to achieve the joint detection of machining deformation, and perform normal vector correction when the machining deformation exceeds a certain range.

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