CN117901047A

CN117901047A - Flexible rail hole making system end effector and hole making method

Info

Publication number: CN117901047A
Application number: CN202410247377.0A
Authority: CN
Inventors: 许斌; 周新房; 刘建桥; 张晋; 石文雄
Original assignee: AVIC Xian Aircraft Industry Group Co Ltd
Current assignee: AVIC Xian Aircraft Industry Group Co Ltd
Priority date: 2024-03-05
Filing date: 2024-03-05
Publication date: 2024-04-19

Abstract

The invention discloses an end effector of a flexible rail hole making system and a hole making method, wherein the end effector comprises an X-direction elastic guide rail adsorbed on the surface of a skin, a Y-direction guide rail crossing the X-direction elastic guide rail, a driving mechanism, a box body clamped between the Y-direction guide rails, an electric spindle adjusting device, a floating pressure head, a pressure head adjusting device, a control system, a laser range finder, an industrial camera and a force sensor, wherein the electric spindle adjusting device and the pressure head adjusting device are arranged in an opening of the box body, the electric spindle is arranged in the center of the electric spindle adjusting device, the floating pressure head is arranged at the bottom of the pressure head adjusting device, the laser range finder, the industrial camera and the force sensor are arranged on the floating pressure head, the industrial camera photographs and calculates the position of a reference hole on a product, the laser range finder measures and calculates the normal direction of the hole to be made, and the control system controls each mechanism to drive the electric spindle to move to the hole making position for hole making after the floating pressure head moves to the hole making position of the product.

Description

Flexible rail hole making system end effector and hole making method

Technical Field

The invention relates to the technical field of aviation manufacturing and assembly, in particular to an end effector of a flexible rail hole making system and a hole making method.

Background

When the surface of the large aircraft skin is perforated, the current trend is to adopt a track type perforation system, namely, a track of perforation equipment is paved on the surface of the aircraft skin, so that the perforation system is adsorbed on the surface of the aircraft skin, and actions such as reference hole identification, positioning, perforation, quality inspection and the like are completed. This requires that the system be lightweight and compact for ease of handling, as the end effector also carries visual, force and other precision sensors, and also requires strength and rigidity. In aircraft assembly, flexible rail hole making systems are becoming increasingly popular. The flexible rail hole making system can press the curved surface of a product by using the presser foot, and the curved surface space is converted into a plane space by using a mechanical structure, so that the control system can conveniently position the curved surface. Compared with the traditional robot hole making, the size and the weight of the robot hole making machine are greatly reduced, and the robot hole making machine has certain portability, so that more operations can be carried out on a single station. In the current flexible rail hole making, the adopted end effector is in a 4-axis or 5-axis structure form in a machine tool, the end effector has large volume and weight, the hole cannot be made on a wing thin-wall structure with a small area, and the station replacement is very difficult, so that a small-sized light-weight flexible rail hole making system is needed.

Disclosure of Invention

In order to solve the problems, the invention designs the parallel type hole making system aiming at the light weight and heavy load requirements of the flexible rail hole making end effector, and greatly reduces the weight of the hole making end on the premise of realizing the same function.

An end effector of a flexible rail hole making system comprises a group of parallel X-direction elastic guide rails, X-direction driving mechanisms, a group of parallel Y-direction guide rails, Y-direction driving mechanisms, a box body, an electric spindle adjusting device, a floating pressure head, a pressure head adjusting device, a control system, a laser range finder, an industrial camera and a force sensor, wherein a plurality of suckers are fixed below the X-direction elastic guide rails, the suckers are adsorbed on the surface of a skin of a hole to be made, the group of parallel Y-direction guide rails stretch over the X-direction elastic guide rails, each Y-direction guide rail is provided with one Y-direction driving mechanism, the box body is of a hexagonal structure, each surface is provided with an opening, handles on two sides of the box body are clamped between the Y-direction guide rails and connected with sliding blocks on the guide rails, the electric spindle adjusting device and the pressure head adjusting device are arranged in the opening of the box body, the electric spindle is arranged at the center of the electric spindle adjusting device, the floating pressure head is arranged at the bottom of the pressure head adjusting device, the laser range finder, the industrial camera and the force sensor are arranged on the floating pressure head, the industrial camera calculates the position of a reference hole on a product to be made by photographing, the laser range finder calculates the position of the hole to be made, the product by the linear distance, the laser range finder moves along the three-direction control systems, and the control systems drive the three electric spindle adjusting devices to move along the three directions along the Y-direction adjusting devices and the Y-direction, and the Y-direction adjusting device and the swing angle adjusting device, and the swing angle are arranged along the three directions and the Y-direction adjusting mechanism, and the Y-direction adjusting device moves along the direction and the Y-direction adjusting mechanism and the control direction. The floating pressure head presses the product after moving to the product hole making position, the pressing force is fed back through a pressure sensor on the floating pressure head and is regulated through a pressure head regulating device, and the electric spindle regulating device drives the electric spindle to move to the same position and direction as the floating pressure head for hole making.

The motorized spindle adjusting device comprises three support arm moving mechanisms and a spindle sleeve, wherein the three support arm moving mechanisms are parallel to the motorized spindle and are respectively fixed in openings of a box body at intervals, the spindle sleeve is arranged at the bottom of the three support arm moving mechanisms, the motorized spindle is arranged in the spindle sleeve, and the three support arm moving mechanisms can respectively move along the Z direction to drive the spindle sleeve to move along the hole making direction and the A, B swing angle direction.

The support arm movement mechanism comprises a support arm base, a support arm guide rail, a support arm screw rod, a support arm motor, a support arm sliding block and a ball head supporting rod, wherein the support arm base is fixed in an opening of the box body, the support arm guide rail, the support arm screw rod and the support arm motor are arranged on the support arm base, the support arm sliding block is fixed on the support arm guide rail, the support arm motor drives the support arm screw rod and drives the support arm sliding block to move, one end of the ball head supporting rod is connected with the support arm sliding block in a hinged mode, and the other end of the ball head supporting rod is connected with the main shaft sleeve through a ball hinge.

The pressure head adjusting device consists of three pressure head moving mechanisms, wherein the three pressure head moving mechanisms are parallel to the electric spindle and are respectively fixed in the openings of the box body at intervals, the bottom of the pressure head moving mechanisms is connected with a floating pressure head, and the three pressure head moving mechanisms can respectively move along the Z direction to drive the floating pressure head to move along the hole making direction and the A, B swing angle direction.

The pressure head motion mechanism comprises a pressure head base, a pressure head guide rail, a pressure head screw rod, a pressure head motor, a pressure head sliding block and a pressure head supporting rod, wherein the pressure head base is fixed in an opening of the box body, the pressure head guide rail, the pressure head screw rod and the pressure head motor are arranged on the pressure head base, the pressure head sliding block is fixed on the pressure head guide rail, the pressure head motor drives the pressure head screw rod and drives the pressure head sliding block to move, one end of the pressure head supporting rod is connected with the pressure head sliding block in a hinged mode, and the other end of the pressure head supporting rod is connected with the floating pressure head through a spherical hinge.

The floating pressure head comprises a nose and a bottom plate, the bottom plate is of a circular flat plate structure, a force sensor is arranged at the center of the bottom surface under the bottom plate, the nose is arranged on the force sensor, three laser rangefinders surround the nose and are uniformly distributed, the position relation between the three laser rangefinders and the nose is calibrated and recorded, an industrial camera is arranged between the two laser rangefinders, the upper part of the bottom plate is connected with three pressure head motion mechanisms through a spherical hinge structure, translation and rotation motion are realized under the driving of the three pressure head motion mechanisms, the nose is driven to a hole making position and is pressed on the surface of a product during hole making, the force sensor is used for measuring the pressing force and feeding back to a control system, the laser rangefinder is used for measuring the distance from the measuring head to the surface of the product and converting the distance between the nose and the surface of the product, the industrial camera is used for identifying and drilling a reference hole on the product, and a cutter on an electric spindle extends out through the center of the nose to finish hole making on the product.

The X-direction driving mechanism comprises a gear, a guide rail motor, a guide rail connecting plate, a slide block frame and rollers, wherein the gear is meshed with racks on an X-direction elastic guide rail, the guide rail motor is arranged on the guide rail connecting plate, the guide rail connecting plate connects the two slide block frames, the slide block frame is connected with a Y-direction guide rail, the two X-direction guide rails and the two Y-direction guide rails form a 'back' stable structure, the slide block frame is of a 'C' -shaped structure, four rollers with axes fixed and free to rotate are fixed inside the slide block frame, the rollers are cylindrical, the middle of the slide block frame is concave in a trapezoid cross section, a circular dovetail groove is formed, the X-direction elastic guide rail passes through the dovetail groove, the guide rail motor drives the gear and the racks to move during movement, the slide block frame moves along the X-direction elastic guide rail, the slide block frame and the rollers play a role of slide block, the slide block frame contacts with the rollers through a jogged groove contact surface and rolls in a rolling mode, the dovetail groove of the rollers rotates around the axes of the slide block frame and rolls along the sides of the elastic guide rail, and all structures on the upper part of the slide block move along the X-direction elastic guide rail.

The Y-direction driving mechanism consists of a transverse motor, a coupler, a supporting plate, a transverse screw rod, a sliding block nut and a transverse base, wherein the Y-direction driving mechanism is integrally fixed on a sliding block frame of the X-direction driving mechanism to form a layered tower structure, two moving shafts move independently of each other, the sliding block frame carries the supporting plate, the screw rod is fixed on the supporting plate through a bearing, the transverse motor is positioned on the motor base at the end of a guide rail, the coupler is driven by the motor during movement, the sliding block nut is driven by the coupler to move through the screw rod, and a box body is fixed on the sliding block to drive all structures on the box body to move along the Y direction.

The hole making method by using the end effector of the hole making system comprises the following steps:

firstly, before a flexible rail system is used for making holes, an X elastic guide rail is placed on a curved surface of a product in a lifting or manual carrying mode, and then is fixed in a pneumatic adsorption mode;

2, the part above the X elastic guide rail in the end effector of the hole making system is arranged on the X elastic guide rail, the end effector is operated by the control system to guide the floating pressure head to the position of the first reference hole of the product, the industrial camera is started to take a picture and record the coordinate O ₁ of the hole in the equipment coordinate system, the hole is taken as the origin of the product coordinate system, the end effector is driven to move, the floating pressure head is guided to the position of the second reference hole of the product, and the industrial camera is started to take a picture and record the coordinate O _N of the hole in the equipment coordinate system;

3, projecting all hole making points in the product digital model to a projection plane, wherein the projection plane is selected as a tangent plane of a central point of a hole making region, so as to obtain plane theoretical coordinates O ₁、O₂、…、O_N of all the hole making points under a product coordinate system;

4, calculating the coordinates of O ₂、O₃…、O_N-1 in the equipment coordinate system according to the position conversion relation between the coordinate calculation equipment of O ₁ and O _N in the equipment coordinate system and the product, and compiling an equipment control program;

Starting hole making according to a program, operating an end effector by a control system to move above each position to be hole-made, starting a laser range finder on a floating pressure head, measuring the distance between a measuring head and the surface of a product, feeding back to the control system, fitting a tangential plane of a point to be hole-made by the control system, calculating the normal direction of the point to be hole-made, adjusting the nose feeding direction to be consistent with the normal direction through a pressure head adjusting device, driving a floating pressure head to press on the surface of the product along the normal direction, starting a pressure sensor to adjust pressure, driving an electric spindle by the control system to perform hole making through the electric spindle adjusting device after the pressure adjustment is completed, sequentially retracting the electric spindle and the floating pressure head device along an original path, continuously making holes by the end effector along the directions of an X-direction elastic guide rail and a Y-direction guide rail, and sequentially and circularly completing hole making;

and 6, after the hole making is completed, the hole making system moves again along the hole making path, and the quality detection is carried out by taking pictures at each hole position by using a camera, and the diameter of a circle formed by each hole is calculated in a circle fitting mode, so that whether the hole diameter is qualified is calculated.

Advantageous effects

The invention realizes a parallel end effector for a flexible rail hole making system. The main movement direction is realized by the X-direction elastic guide rail and the X-direction driving mechanism, and the device can adapt to products with different curved surfaces. The hole making system can move along the X-direction elastic guide rail and can move between the X-direction elastic guide rails. By arranging two sets of parallel mechanisms in the main frame of the pore-forming system, the pose adjustment of the floating pressure head and the electric spindle is realized. By arranging components such as a laser range finder, an industrial camera and the like on the floating pressure head component, normal measurement and reference hole positioning are realized. The hole making system realizes parallel five-degree-of-freedom motion in a compact space, and has strong rigidity and stable structure.

Unlike conventional hole making structure, the hole making system has the advantages that in the hole making process, the floating pressure head and the electric spindle are driven separately, the required force and moment are reduced, and the requirements on the power and the structural strength of the motor are lowered. In the motion process of the electric spindle and the floating pressure head, three groups of mechanisms are driven by three groups of motors, and the parallel type motion mode further lightens the requirements on the power and the structural strength of the motors. Due to the two reasons, compared with a traditional hole making mechanism, the motor power and structural strength parameters are reduced to one sixth of the original parameters, so that the bearing structure size and the motor size are greatly reduced, the structure appearance is smaller and more compact, and the operation on the product which cannot bear heavy load, such as an aircraft skin, is facilitated.

In the aspect of gesture control, a parallel type moving pair-rotating pair-spherical hinge mode is adopted, so that the gesture and position adjustment is realized in a narrow space. Each component is tightly attached to the hexagonal main frame, and the installation position is in an open space, so that the installation and the overhaul are convenient. Two types of strut assemblies are employed, most of which are used interchangeably. In terms of structural stress, a cantilever mechanism or a turnover mechanism which is widely used by a traditional hole making system is not adopted, so that the possibility of 'low head' deformation of the system is prevented. The main direction of the stress of the system is the gravity direction, and the gravity direction is directly born by the support arm sliding block and the pressure head sliding block, so that the main direction of the stress of the system is the optimal stress direction of the component. Various sensors are arranged on the outer end face of the floating pressure head, the positions of the sensors can be directly finely adjusted during sensor calibration, the performance requirements on the measuring distance of the sensors are reduced, and the sensors are conveniently calibrated.

The hole making part adopts a special parallel kinematic pair form and an optimized space structure, so that a flexible rail hole making system with light weight, compact structure and powerful function is formed, and the hole making system can meet the hole making of curved surface products with large curvature change and high precision requirements.

Drawings

FIG. 1 is a block diagram of the end effector of the flexible rail system

Fig. 2 is a block diagram of an electric spindle adjusting device

FIG. 3 is a block diagram of a motion mechanism for a support arm

FIG. 4 is a block diagram of a ram adjustment assembly

FIG. 5 floating ram and sensor block diagram

FIG. 6 is a block diagram of a X-direction drive mechanism

FIG. 7 is a block diagram of a Y-direction drive mechanism

Figure 8 box structure diagram

FIG. 9 is a schematic diagram of coordinate transformation

FIG. 10 is a schematic diagram of camera calibration

Fig. 11 laser range finder calibration schematic diagram

FIG. 12 is a schematic diagram of force sensor calibration

FIG. 13 is a schematic view of point projection

The numbers in the figures illustrate 1: x-direction elastic guide rail, 2: x-direction driving mechanism, 3: y-direction guide rail, 4: y is to actuating mechanism, 5: box, 6: motorized spindle, 7: motorized spindle adjusting device, 8: floating ram, 9: pressure head adjusting device, 10: laser rangefinder, 11: industrial camera, 12: force sensor, 2.1: gear, 2.2: guide rail motor, 2.3: guide rail link plate, 2.4: slider frame, 2.5: roller, 4.1: transverse motor, 4.2: coupling, 4.3: support plate, 4.4: transverse screw, 4.5: slider nut, 4.6: transverse base, 7.1: arm motion mechanism, 7.2: spindle sleeve, 7.3: support arm base, 7.4: arm guide rail, 7.5: support arm lead screw, 7.6: arm motor, 7.7: arm slider, 7.8: ball head strut, 8.1: nose, 8.2: bottom plate, 9.1: ram motion mechanism, 9.2: pressure head base, 9.3: ram guide rail, 9.4: pressure head lead screw, 9.5: ram motor, 9.6: ram slide, 9.7: pressure head strut

Detailed Description

As shown in fig. 1-13, an end effector of a flexible rail hole making system

Fig. 1), comprising a group of parallel X-direction elastic guide rails 1, an X-direction driving mechanism 2, a group of parallel Y-direction guide rails 3, a Y-direction driving mechanism 4, a box body 5, an electric spindle 6, an electric spindle adjusting device 7, a floating pressure head 8, a pressure head adjusting device 9, a control system, a laser range finder 10, an industrial camera 11, a force sensor 12, a plurality of suckers fixed under the X-direction elastic guide rails 1, the suckers are adsorbed on the surface of a skin of a hole to be made, a group of parallel Y-direction guide rails 3 span the X-direction elastic guide rails 1, each Y-direction guide rail 3 is provided with a Y-direction driving mechanism 4, the box body 5 is of a hexagonal structure, each surface is provided with an opening, handles on two sides of the box body are clamped between the Y-direction guide rails 3 and are connected with slide block nuts 4.5 on the guide rails, the electric spindle adjusting device 7 and the pressure head adjusting device 9 are arranged in the opening of the box body 5, the electric spindle 6 is arranged at the center of the electric spindle adjusting device 7, the floating pressure head 8 is arranged at the bottom of the pressure head adjusting device 9, the floating pressure head 8 is provided with a laser distance meter 10, an industrial camera 11 and a force sensor 12, the industrial camera 11 calculates the position of a reference hole on a product to be drilled through photographing, the laser distance meter 10 calculates the normal direction of the hole to be drilled through a linear distance and feeds back to a control system, the control system controls the electric spindle adjusting device 7, the electric spindle 6 is driven to move along the Z direction and the two swing angle directions through three support arm moving mechanisms 7.1 on the control system, the pressure head adjusting device 9 is controlled to drive the floating pressure head 8 to move along the product normal direction and the two swing angle directions through three pressure head moving mechanisms 9.1 on the control pressure head adjusting device 9, the Y-direction driving mechanism 4 is controlled to drive the box 5 and the electric spindle 6, the electric spindle adjusting device 7, the floating pressure head 8 and the pressure head adjusting device 9 on the box body to move along the Y direction, the X-direction driving mechanism 2 is controlled to drive the Y-direction guide rail 3 and all parts on the Y-direction guide rail to move along the X-direction, the floating pressure head 8 moves to a product hole making position and then presses products, a pressing force is fed back through a force sensor 12 on the floating pressure head 8 and is regulated through a pressure head regulating device 9, and the electric spindle regulating device 7 drives the electric spindle 6 to move to the same position and direction as the floating pressure head 8 to make holes.

The end effector of the flexible rail hole making system is movable hole making equipment, is placed on a curved surface of a product in a lifting or manual carrying mode, and is fixed in a pneumatic adsorption mode. Due to the design of the flexible guide rail, the flexible guide rail can be suitable for skin systems of parts such as airplane wings, airplane fuselages and the like with common curvatures at present. For some high curvature products, the degree of flexure of the flexible rail can be increased by reducing the size of the pneumatic suction cup. In order to resist the influence of gravity, the optimal hole making direction is vertical downward, the system is lighter in weight and stable in adsorption mode, and the whole system can be horizontally placed, namely, the hole making direction is horizontal.

As shown in fig. 2, the motorized spindle adjusting device 7 includes three arm moving mechanisms 7.1 and a spindle sleeve 7.2, the three arm moving mechanisms 7.1 are parallel to the motorized spindle 6 and are respectively fixed in spaced openings of the box 5 (fig. 8), the spindle sleeve 7.2 is mounted at the bottom of the three arm moving mechanisms 7.1, the motorized spindle 6 is mounted in the spindle sleeve 7.2, and the three arm moving mechanisms 7.1 can respectively move along the Z direction to drive the spindle sleeve 7.2 to move along the hole making direction and the A, B swing angle direction.

As shown in fig. 3, the arm movement mechanism 7.1 includes an arm base 7.3, an arm guide rail 7.4, an arm screw rod 7.5, an arm motor 7.6, an arm slide block 7.7 and a ball head support rod 7.8, wherein the arm base 7.3 is fixed in an opening of the box body, the arm guide rail 7.4, the arm screw rod 7.5 and the arm motor 7.6 are installed on the arm base 7.3, the arm slide block 7.7 is fixed on the arm guide rail 7.8, the arm motor 7.6 drives an arm wire 7.5 rod and drives the arm slide block 7.7 to move, one end of the ball head support rod 7.8 is connected with the arm slide block 7.7 in a hinged mode, and the other end is connected with the main shaft sleeve 7.2 through a ball hinge.

The three support arm movement mechanisms 7.1 are distributed and fixed on the outer side of the box body 5, and the function of the three support arm movement mechanisms is to feed and adjust the posture of the motorized spindle 6. In the moving process, the ball head supporting rod 7.8 translates along the moving direction of the support arm screw rod 7.5 and rotates around the ball hinge on the support arm sliding block 7.7. The spindle sleeve 7.2 is connected with three ball head struts 7.8 through three spherical hinges, and on one hand, the spindle sleeve translates, so that on the other hand, rotation in two directions is performed due to different displacement sizes of the support arm sliding blocks 7.7. The hinge structure and the ball hinge structure release over-constraint in the movement process and ensure that the spindle sleeve 7.2 has no unrestricted degree of freedom. The motorized spindle 6 is sleeved in the spindle sleeve 7.2 in a rigid connection mode, and feeding and posture adjustment are realized along with the movement of the support arm sliding block 7.7. During the movement, the motorized spindle adjustment device 7 forms a single kinematic mechanism, the degrees of freedom of which can be calculated using the grubler formula, namely:

Wherein:

m represents the number of degrees of freedom, m=3 for a planar mechanism; for a spatial mechanism m=6,

N represents the number of components (including the machine base),

J represents the number of the joints of the patient,

C _i denotes the degree of freedom of the i-th joint,

Corresponding to the motorized spindle adjusting device 7, m=6 since it is a spatial mechanism. In calculating the number of components, the three arm bases 7.4 can be considered as fixed parts, the remaining components being: the three support arm slide blocks 7.7 and the ball head support rods 7.8 are respectively arranged, one main shaft sleeve 7.2 is arranged, and the other fixing part is arranged, namely 8 components are arranged. The joints of the three-set support arm movement mechanism 7.1 comprise: the support arm lead screw 7.5 and the support arm slider 7.7 form a moving pair, the support arm slider 7.7 and the ball head support rod 7.8 form a revolute pair and the ball head support rod 7.8 and the main shaft sleeve 7.2 form a spherical hinge, namely each support arm has 3 joints, wherein the freedom degree of the moving pair is 1, the freedom degree of the revolute pair is 1, and the freedom degree of the spherical hinge is 3. So there are:

dof＝6*((3*2+1+1)-1-(3*3))-3*(1+1+3)＝3

Namely, the degrees of freedom of the motorized spindle adjusting device 7 are 3, and the 3 degrees of freedom are controlled by the moving pairs driven by the 3 support arm motors 7.6, so that the position and the gesture of the spindle sleeve 7.2 connected with the support arm moving mechanism 7.1 are controlled.

As shown in fig. 4, the ram adjusting device 9 is composed of three ram moving mechanisms 9.1, wherein the three ram moving mechanisms are parallel to the motorized spindle 6 and are respectively fixed in the spaced openings of the box body 5, the bottom of each ram moving mechanism is connected with a floating ram 8, and the three ram moving mechanisms 9.1 can respectively move along the Z direction to drive the floating ram to move along the hole making direction and the A, B swing angle direction.

The pressure head moving mechanism 9.1 comprises a pressure head base 9.2, a pressure head guide rail 9.3, a pressure head lead screw 9.4, a pressure head motor 9.5, a pressure head sliding block 9.6 and a pressure head supporting rod 9.7, wherein the pressure head base 9.2 is fixed in an opening of the box body 5, the pressure head guide rail 9.3, the pressure head lead screw 9.4 and the pressure head motor 9.5 are arranged on the pressure head base 9.2, the pressure head sliding block 9.6 is fixed on the pressure head guide rail 9.3, the pressure head motor 9.5 drives the pressure head lead screw 9.4 and drives the pressure head sliding block 9.6 to move, one end of the pressure head supporting rod 9.7 is connected with the pressure head sliding block 9.6 in a hinged mode, and the other end of the pressure head supporting rod 9.7 is connected with the floating pressure head 8 through a spherical hinge.

The pressure head adjusting device 9 drives the rotary hinges and the spherical hinges at the two ends of the pressure head supporting rod 9.7 to realize conversion from three displacement amounts to one translation and two rotation angles, namely, the floating pressure head 8 is adjusted to a proper position and angle. In the process of adjusting the floating pressure head 8, the pressure head adjusting device 9 firstly adjusts the direction of the floating pressure head 8 to enable the direction to coincide with the normal direction of a product, and then enables the floating pressure head 8 to integrally feed forward to enable the nose 8.1 to press on the surface of the product.

As shown in fig. 5, the floating pressure head 8 comprises a nose 8.1 and a bottom plate 8.2, the bottom plate 8.2 is of a circular flat plate structure, a force sensor is arranged in the center of the lower bottom surface of the bottom plate 8.2, the nose 8.1 is arranged on a force sensor 12, three laser distance meters 10 are uniformly distributed around the nose 8.1 and are calibrated and recorded in the position relation with the nose 8.1, an industrial camera 11 is arranged between the two laser distance meters 10, the upper part of the bottom plate 8.2 is connected with three pressure head movement mechanisms 9.1 through a spherical hinge structure and is driven by the three pressure head movement mechanisms to realize translational and rotational movement, so that the nose 8.1 is driven to a hole making position and is pressed on the surface of a product during hole making, the force sensor 12 measures the pressing force and feeds back to a control system, the laser distance from the measuring head to the surface of the product, the nose 8.1 is converted into the distance from the surface of the product, the industrial camera 11 recognizes a reference hole drilled on the product, a cutter on the electric spindle 6 stretches out through the center of the nose 8.1, and the hole making is completed on the product.

The floating pressure head 8 is integrated with a plurality of sensors, and has a plurality of functions in the positioning process, firstly, the position of a reference hole is calculated by using an industrial camera 11, a local coordinate system of a product is established, and the position calibration between the product and equipment is realized; secondly, detecting the normal direction, sampling the distances between a plurality of points on the surface of the product and the hole making equipment through the laser range finder 10, fitting the surface of the product, and calculating the normal position of the product; thirdly, the product is pressed, the nose 8.1 is pressed on the surface of the product, the product and the hole making equipment are prevented from mutual displacement when holes are made, and the pressing force is measured through the force sensor 12. The premise of realizing the three functions is to calibrate various measuring devices.

As shown in fig. 10, when the industrial camera 11 is calibrated, that is, the inner parameter matrix and the outer parameter matrix of the camera need to be determined, this may be achieved by "hand-eye calibration" of the industrial camera 11, but the process is complicated, and the calibration of the camera may be achieved by a simplified method. Firstly, a standard state is defined, namely, the electric spindle adjusting device 7 and the pressure head adjusting device 9 are in initial states, the electric spindle 6 and the floating pressure head 8 do not rotate relative to the feeding direction of the electric spindle 6, the outer plane of the nose 8.1 is perpendicular to the feeding direction of the electric spindle 6, the electric spindle adjusting device 7 extends to the position with the most proper focal length when the industrial camera 11 shoots, and the extending amount of the electric spindle 6 is positioned at the position suitable for hole making. The motorized spindle 6 is then made to make a hole in a flat test piece, the industrial camera 11 is started to take a picture, and the offset is recorded in the image coordinate system. The deviation of the hole coordinates from the reference in the image captured by the post-industrial camera 11 is the deviation of the actual position of the hole, with the offset as the reference.

As shown in fig. 11, when calibrating the laser rangefinder 10, it is necessary to calculate its installation angle and position, for a total of three unknowns, which can be measured using a calibration plane. Firstly, a reference plane and a reference coordinate system are required to be determined, a calibration plane is arranged on the outer plane of the nose 8.1 of the floating pressure 8, the plane is taken as the reference plane, the center of the nose 8.1 is taken as the reference origin, the X-axis direction and the Y-axis direction can be determined according to the directions of the X-direction elastic guide rail 1 and the Y-direction guide rail 3, and the Z-axis direction is determined according to the right-hand rule. Firstly, the displacement of three laser rangefinders 10 is recorded in a reference coordinate system, then the calibration plane is moved outwards for a certain distance and rotated for a certain angle, the values of the sensors are recorded again, and the corresponding relation between the normal direction of the calibration plane and the sensor values can be obtained by repeating the above processes. The value of the origin of the laser rangefinder 10 in the reference coordinate system can be obtained using the above system of equations. The adoption of the above direction requires recording of multiple sets of values and accurate measurement of the normal to the calibration plane by external measurement equipment. In practice, the laser rangefinder 10 may be mechanically mounted with its measurement direction coincident with the nose axis, with its mounting locations being 120 ° evenly distributed on the mounting plane and one of them being located in the X-axis direction of the reference plane. Thus, only the distance between the laser distance meter 10 and the reference plane needs to be determined during calibration. When the calibration plane is moved, the calibration plane is only required to be ensured to be parallel to the reference calibration plane, and the angle rotation is not required, so that the calibration method of the laser range finder 10 is greatly simplified.

As shown in fig. 12, calibration of the force sensor 12 may be accomplished by a standard force sensor (e.g., an electronic scale). After the force sensor 12 is mounted on the device, it itself has a certain internal stress, and its indication cannot reflect the actual force of the nose 8.1 against the product due to the influence of factors such as zero drift of the electrical system. When the calibration is carried out, the nose 8.1 is only required to be pressed on the electronic scale, the electronic scale is fed forwards for a certain distance, the electronic scale indication and the pressure sensor indication are observed in the feeding process, and the difference value of the electronic scale indication and the pressure sensor indication is the reference force value of the force sensor 12. The reference force value subtracted from the reading of force sensor 12 at the time of hole making is the actual force value applied to the product.

After the floating pressure head 8 is pressed onto the product during the hole making, the force sensor 12 needs to determine the pressing force, the force value must be within a reasonable range, and if the force is excessive, the product may be damaged; if the force is too small, the product can vibrate along the normal direction during hole making, and the deviation of the aperture or the pit depth is caused. The force value is regulated by three pressure head movement mechanisms 9.1, which can be realized by a PID control method, and can also be directly calculated by the displacement value of the laser range finder 10. In either way, it is necessary to ensure that the linear assembly stops feeding after the force value is greater than a certain safety threshold. After normal adjustment, the feed amounts of the three ram motion mechanisms 9.1 may be inconsistent, so that the feed is performed by interpolation after inverse solution to ensure the positional constraint relationship between them. After the floating ram 8 has been pressed against the product, the axis of the nose 8.1 is aligned with the normal direction of the product, as is the normal direction of the motorized spindle 6. The motorized spindle adjusting device 7 adopts a structure similar to the pressure head adjusting device 9, and realizes the translation of one degree of freedom and the rotation of two degrees of freedom by adjusting the support arm moving mechanism 7.1, thereby realizing the translation and the angle adjustment of the motorized spindle 6. In the posture adjustment process, firstly, posture adjustment is carried out, so that the axial direction of the electric spindle 6 is the same as the axial direction of the nose 8.1, and then the electric spindle 6 is fed forwards, so that hole making on the surface of a product is realized. During the feeding process, the control of the pit depth is controlled by the feeding difference value of the motorized spindle adjusting device 7 and the pressure head adjusting device 9. When the floating ram 8 is pressed against the product, the feed is determined and the hole making system has obtained positional information of the product, i.e. the position of the outer plane of the nose 8.1. When the motorized spindle adjusting device 7 is used for feeding, the reference is used for the reference, and the hole making depth of the cutter on a product is the displacement of the support arm moving mechanism 7.1 on the basis, so that the pit depth can be controlled.

As a structural diagram

As shown in fig. 6, the X-direction driving mechanism 2 includes a gear 2.1, a rail motor 2.2, a rail connecting plate 2.3, a slider frame 2.4, and a roller 2.5, the gear 2.1 is meshed with the rack of the X-direction elastic rail 1, the rail motor 2.2 is mounted on the rail connecting plate 2.3, the rail connecting plate 2.3 connects the two slider frames 2.4, the slider frame 2.4 is connected with the Y-direction rail 3, the two X-direction elastic rails 1 and the two Y-direction rails 3 form a "back" shape stable structure, the slider frame is a "C" structure, four rollers 2.5 with axes fixed and freely rotating are fixed inside, the rollers 2.5 are cylindrical, the middle is concave with a trapezoid cross section to form a circular dovetail groove, the X-direction elastic rail 1 passes through the dovetail groove, the slider frame 2.2 moves along the X-direction elastic rail 1, the slider frame 2.4 and the roller 2.5 plays a rolling role, the side edge of the X-direction elastic rail 1 plays a guiding role, the slider frame 2.4 contacts the roller 2.5 along the axial direction of the dovetail groove along the X-direction elastic rail 1, and moves along the axial direction of the rolling direction along the axial direction of the roller 1.

As shown in fig. 7, the Y-direction driving mechanism 4 is composed of a transverse motor 4.1, a coupler 4.2, a supporting plate 4.3, a transverse screw rod 4.4, a sliding block nut 4.5 and a transverse base 4.6, the Y-direction driving mechanism 4 is integrally fixed on the sliding block frame 2.4 of the X-direction driving mechanism 2 to form a layered tower structure, two moving shafts move independently of each other, the sliding block frame 2.4 carries the supporting plate 4.3, the transverse screw rod 4.4 is fixed on the supporting plate 4.3 through a bearing, the transverse motor 4.1 is fixed on the end of the transverse base 4.6, the coupler 4.2 is driven by the transverse motor 4.1 during movement, the sliding block nut 4.5 is driven by the coupler 4.2 to move through the transverse screw rod 4.4, and the box body 5 is fixed on the sliding block nut 4.5 to drive all structures on the box body 5 to move along the Y direction.

The flexible rail hole making system adopts a double-rail mode, is adsorbed on the surface of a product, adopts a semi-enclosed embedded roller 2.5 and gear 2.1 driving mode to integrate an X-direction driving mechanism 2 on a guide rail, and erects a Y-direction driving mechanism 4 between the X-direction driving mechanisms 2, and realizes Y-direction movement of the hole making system by utilizing a ball screw driving sliding block mode. The X-and Y-direction movements achieve positioning of the hole making system on the surface of the product, the travel of which also determines the size of the hole making area. Except for the movable assembly, the core part of the hole making system adopts a hexagonal box body 5 as a main stress structure. The motorized spindle 6 and the floating pressure head 8 are controlled by adopting parallel structures. The motorized spindle adjusting device 7 and the pressure head adjusting device 9 are uniformly distributed on six surfaces of the hexagon to form a central symmetrical structure. The adjusting device comprises a moving pair, a rotating pair and a spherical hinge, so that three-degree-of-freedom motion is realized, and the five-degree-of-freedom motion of the whole hole making system is realized by combining the X-direction moving assembly and the Y-direction moving assembly.

Before the flexible rail system is used for hole making, the X elastic guide rail 1 is firstly placed on a curved surface of a product in a lifting or manual carrying mode, and then is fixed in a pneumatic adsorption mode.

2 The upper part of the X elastic guide rail 1 in the end effector of the hole making system is arranged on the X elastic guide rail 1, the end effector is operated by the control system to guide the floating pressure head to the position of the first reference hole of the product, the industrial camera 11 is started to take a picture and record the coordinate O ₁ of the hole under the equipment coordinate system, the end effector is driven to move again to guide the floating pressure head to the position of the second reference hole of the product, the industrial camera 11 is started to take a picture and record the coordinate O _N of the hole under the equipment coordinate system, the coordinates of the two points under the equipment coordinate system are obtained by the vision system, the theoretical coordinates of the two points are known, thus a plane coordinate system can be established through the two points, and the X axis direction isThe Y-axis direction is perpendicular to the X-axis, and the X-axis refers to the X-direction elastic guide rail 1, which is a curve axis, and the Y-axis direction, namely the Y-direction guide rail 3 direction is perpendicular to the X-axis, which is ensured by a mechanical structure.

3 After the plane coordinate system is established, the curved surface of the product is paved to obtain the plane coordinates (figure 9) of each point, and the plane coordinates of each hole can be used for positioning. And (3) projecting all the hole making points in the product digital model to a projection plane (figure 13), wherein the projection plane is selected as a tangential plane of the central point of the hole making region, and the plane theoretical coordinate O ₁、O₂、…、O_N of all the hole making points under the product coordinate system is obtained. The end effector of the hole making system is five-axis equipment, the X-direction elastic guide rail 1 and the Y-direction guide rail 3 of the end effector realize the movement on the plane, the Z-direction movement is used for feeding the hole making and moving the cutter on the electric spindle 6 out of the plane to prevent the cutter from rubbing with the plane of a product, and the normal direction of the product needs to be reestablished through the laser range finder 10 when the end effector moves to a specific hole site. In the hole making idle process, the electric spindle 6 and the floating pressure head 8 are required to be lifted upwards to the highest distance, so that collision with products during movement of hole making equipment is prevented. After the end effector of the flexible rail hole making system moves to a designated hole site according to plane coordinates, the nose 8.1 of the floating pressure head 8 is at a certain distance from the surface of the product, and the three laser range finders 10 are started and detect the laser beam displacement from the surface of the product. Since the mounting positions of the three laser rangefinders 10 are known, the direction of the laser light they project is also known, and the coordinates of three points on the surface of the product can be obtained from the displacement of the three laser beams. The local plane of the product surface can be fitted according to the coordinates of the three points, and the normal of the plane is obtained. The displacement and attitude angle of the floating ram 8 can be calculated according to the displacement of the laser beam and the normal value of the plane.

4 Calculating the coordinates of O ₂、O₃…、O_N-1 under the equipment coordinate system according to the position conversion relation between the coordinate calculation equipment and the product under the equipment coordinate system and the product coordinate system of O ₁ and O _N, programming the equipment control program, calculating the hole site coordinates, and calculating T= [ O ₁ O_N][Q₁ Q_N]⁺ ] assuming that the pose matrix of the equipment coordinate system of the hole making system under the product coordinate system is T, wherein "+" represents the generalized inverse of the matrix, and the coordinates of the rest holes to be made under the equipment can be calculated through O _i＝T·Q_i (i=2..N-1).

5, Starting hole making according to a program, operating an end effector to move above each position to be hole made by the control system, starting a laser range finder 10 on a floating pressure head 8, measuring the distance between a measuring head and the surface of a product, feeding back to the control system, fitting a tangential plane of a point to be hole made by the control system, calculating the normal direction of the point to be hole made, regulating the feeding direction of a nose 8.1 to be consistent with the normal direction through a pressure head regulating device 9, driving the floating pressure head 8 to press on the surface of the product along the normal direction, starting a pressure sensor 9 to regulate pressure, after pressure regulation is completed, driving an electric spindle 6 to make holes along the normal direction of the product by the control system through an electric spindle regulating device 7, after hole making is completed, sequentially retracting the electric spindle 6 and the floating pressure head 8 along an original path, continuously making holes by the end effector along the directions of an X-direction elastic guide rail 1 and a Y-direction guide rail 3, and sequentially and circularly completing hole making;

6, after the hole is formed, the hole forming system moves again along the hole forming path, and the quality detection is carried out by photographing through an industrial camera 11 at each hole position, and the diameter of a circle formed by each hole is calculated in a circle fitting mode, so that whether the hole diameter is qualified is calculated.

Claims

1. An end effector of a flexible rail hole making system is characterized by comprising a group of parallel X-direction elastic guide rails, X-direction driving mechanisms, a group of parallel Y-direction guide rails, Y-direction driving mechanisms, a box body, an electric spindle adjusting device, a floating pressure head, a pressure head adjusting device, a control system, a laser range finder, an industrial camera and a force sensor, wherein a plurality of suckers are fixed below the X-direction elastic guide rails, the suckers are adsorbed on the surface of a skin of a hole to be made, the group of parallel Y-direction guide rails stretch over the X-direction elastic guide rails, each Y-direction guide rail is provided with a Y-direction driving mechanism, the box body is of a hexagonal structure, each surface is provided with an opening, handles on two sides of the box body are clamped between the Y-direction guide rails and are connected with sliding blocks on the guide rails, the electric spindle adjusting device and the pressure head adjusting device are arranged in the opening of the box body, the electric spindle is arranged at the center of the electric spindle adjusting device, the floating pressure head is arranged at the bottom of the pressure head adjusting device, the floating pressure head is provided with the laser range finder, the industrial camera and the force sensor, the industrial camera calculates the position of a reference hole on a product to be made through calculation, the range finder is arranged on the product, the laser range finder is arranged on the floating pressure head, the product to be made to move along the direction of the Y-direction by the linear range finder, the control system and the two control heads and the two control devices move along the direction of the Y-direction guide mechanisms along the Y-direction guide shafts, the Y-direction guide mechanism and the Y-direction guide mechanism, and the Y-direction swing angle adjusting device move along the direction, and the Y-direction control mechanism and the Y-direction swing angle adjusting mechanism moves along the direction. The floating pressure head presses the product after moving to the product hole making position, the pressing force is fed back through a pressure sensor on the floating pressure head and is regulated through a pressure head regulating device, and the electric spindle regulating device drives the electric spindle to move to the same position and direction as the floating pressure head for hole making.

2. The end effector of a flexible rail hole forming system according to claim 1, wherein the motorized spindle adjusting device comprises three arm moving mechanisms and a spindle sleeve, the three arm moving mechanisms are parallel to the motorized spindle and are respectively fixed in the spaced openings of the box body, the spindle sleeve is arranged at the bottoms of the three arm moving mechanisms, the motorized spindle is arranged in the spindle sleeve, and the three arm moving mechanisms can respectively move along the Z direction to drive the spindle sleeve to move along the hole forming direction and the A, B swing angle direction.

3. The end effector of a flexible rail hole forming system according to claim 2, wherein the arm moving mechanism comprises an arm base, an arm guide rail, an arm screw rod, an arm motor, an arm slider and a ball head strut, the arm base is fixed in the opening of the box body, the arm guide rail, the arm screw rod and the arm motor are mounted on the arm base, the arm slider is fixed on the arm guide rail, the arm motor drives the arm screw rod and drives the arm slider to move, one end of the ball head strut is connected with the arm slider in a hinged manner, and the other end is connected with the spindle sleeve through a ball hinge.

4. The end effector of a flexible rail hole forming system according to claim 1, wherein the pressure head adjusting device comprises three pressure head moving mechanisms, the three pressure head moving mechanisms are parallel to the electric main shaft and are respectively fixed in the openings of the box body at intervals, the bottom of the three pressure head moving mechanisms are connected with a floating pressure head, and the three pressure head moving mechanisms can respectively move along the Z direction to drive the floating pressure head to move along the hole forming direction and the A, B swing angle direction.

5. The flexible rail hole making system end effector as claimed in claim 4, wherein the ram motion mechanism comprises a ram base, a ram guide rail, a ram screw rod, a ram motor, a ram slider and a ram support rod, the ram base is fixed in the opening of the box body, the ram guide rail, the ram screw rod and the ram motor are mounted on the ram base, the ram slider is fixed on the ram guide rail, the ram motor drives the ram screw rod and drives the ram slider to move, one end of the ram support rod is connected with the ram slider in a hinged manner, and the other end is connected with the floating ram through a spherical hinge.

6. The end effector of a flexible rail hole making system according to claim 1, wherein the floating pressure head comprises a nose and a bottom plate, the bottom plate is of a circular flat plate structure, a force sensor is arranged at the center of the lower bottom surface of the bottom plate, the nose is arranged on the force sensor, three laser rangefinders are uniformly distributed around the nose and mark and record the position relation between the three laser rangefinders and the nose, an industrial camera is arranged between the two laser rangefinders, the upper part of the bottom plate is connected with three pressure head movement mechanisms through a spherical hinge structure, translation and rotation movement are realized under the driving of the bottom plate, the nose is driven to the hole making position and is pressed on the surface of a product during hole making, the force sensor measures the pressing force and feeds back to a control system, the laser rangefinder measures the distance between the pressure head and the surface of the product and feeds back to the control system after converting the distance between the nose and the surface of the product, the industrial camera recognizes a reference hole drilled on the product, and a cutter on an electric spindle stretches out through the center of the nose to finish hole making on the product.

7. The end effector of a flexible rail hole forming system according to claim 1, wherein the X-direction driving mechanism comprises a gear, a rail motor, a rail connecting plate, a slider frame and a roller, the gear is meshed with a rack on the X-direction flexible rail, the rail motor is mounted on the rail connecting plate, the rail connecting plate connects two slider frames, the slider frame is connected with a Y-direction rail, the two X-direction and the two Y-direction rails form a 'back' stable structure, the slider frame is a 'C' -shaped structure, four rollers with fixed axes and free rotation are fixed inside, the rollers are cylindrical, the middle is concave with a trapezoid cross section to form a circular dovetail groove, the X-direction flexible rail passes through the dovetail groove, the rail motor drives the gear rack to move during movement, the slider frame moves along the X-direction flexible rail, the slider frame and the rollers play a role of sliding, the side edges of the flexible rail play a role of guiding, the slider frame contacts with the rollers through a contact surface of the embedded groove and moves in a rolling manner, the dovetail groove of the rollers rotates around the axes of the flexible rail, and rolls along the side edges of the flexible rail, and all structures on the upper part of the flexible rail move along the X-direction flexible rail direction.

8. The end effector of a flexible rail hole forming system according to claim 1, wherein the Y-direction driving mechanism is composed of a transverse motor, a coupler, a supporting plate, a transverse screw rod, a slide nut and a transverse base, the Y-direction driving mechanism is integrally fixed on a slide frame of the X-direction driving mechanism to form a layered tower structure, two moving shafts move independently of each other, the slide frame carries the supporting plate, the screw rod is fixed on the supporting plate through a bearing, the transverse motor is positioned on the motor base at the end of the guide rail, the coupler is driven by the motor during movement, the slide nut is driven by the screw rod to move, and the box body is fixed on the slide block to drive all structures on the box body to move along the Y direction.

9. A method of making a hole using a flexible rail hole making system end effector as defined in any one of claims 1-8, comprising the steps of:

9-1, before the flexible rail system is used for hole making, firstly placing the X elastic guide rail on a curved surface of a product in a lifting or manual carrying mode, and then fixing the X elastic guide rail in a pneumatic adsorption mode;

9-2, the part above the X-direction elastic guide rail in the end effector of the hole making system is arranged on the X-direction elastic guide rail, the end effector is operated by the control system to guide the floating pressure head to the position of a first reference hole of a product, an industrial camera is started to take a picture and record the coordinate O ₁ of the hole in a device coordinate system, the hole is taken as the origin of the product coordinate system, the end effector is driven to move, the floating pressure head is guided to the position of a second reference hole of the product, and the industrial camera is started to take a picture and record the coordinate O _N of the hole in the device coordinate system;

9-3, projecting all hole making points in the product digital model to a projection plane, wherein the projection plane is selected as a tangential plane of a central point of a hole making region, and a plane theoretical coordinate O ₁、O₂、…、O_N of all the hole making points under a product coordinate system is obtained;

9-4, calculating the coordinates of O ₂、O₃…、O_N-1 in the equipment coordinate system according to the position conversion relation between the coordinate calculation equipment of O ₁ and O _N in the equipment coordinate system and the product, and programming the equipment control program;

9-5, starting hole making according to a program, operating an end effector to move above each position of a hole to be made by a control system, starting a laser range finder on a floating pressure head, measuring the distance between a measuring head and the surface of a product, feeding back to the control system, fitting a tangential plane of the point to be made by the control system, calculating the normal direction of the point to be made, adjusting the nose feeding direction to be consistent with the normal direction through a pressure head adjusting device, driving the floating pressure head to press on the surface of the product along the normal direction, starting a pressure sensor to adjust pressure, driving an electric spindle to make holes along the normal direction of the product by the control system through an electric spindle adjusting device after pressure adjustment is completed, sequentially retracting the electric spindle and the floating pressure head device along an original path after hole making is completed, continuously making holes by the end effector along the directions of an X-direction elastic guide rail and a Y-direction to the next hole site, and sequentially and circularly completing hole making;

9-6, after hole making is completed, the hole making system moves again along the hole making path, and the quality detection is carried out by taking pictures at each hole position through a camera, and the diameter of a circle formed by each hole is calculated in a circle fitting mode, so that whether the hole diameter is qualified is calculated.