Automatic skin placing method

Abstract

The invention relates to an automatic skin placing method, belongs to the technical field of automatic skin assembly, and solves the technical problem of low skin placing precision in the prior art. The method comprises the following steps: teaching a manipulator to execute a task of assembling a skin on a skeleton; a framework is arranged at a target position, a to-be-assembled skin is adsorbed through the tail end of a mechanical arm, and the mechanical arm is made to move the skin to the preset position along the teaching path according to the teaching transformation; respectively photographing and identifying the skin and the skeleton through a visual identification device; performing visual matching calculation to obtain actual transformation of the tail end of the manipulator; and the tail end of the manipulator adjusts the pose of the skin according to the actual transformation, and then the skin is positioned and placed on the framework from the preset position. According to the invention, the actual poses of the skin and the skeleton are respectively identified to adjust the teaching path, so that the adsorption error is offset, and the placement precision of the skin is improved.

Description

Technical Field

[0001] The invention relates to the technical field of automatic skin assembly, and in particular to an automatic skin placement method. Background Art

[0002] In the welding unit of complex components, the skin is a special type of wing component, which poses a great challenge to the automated welding process. The manufacturing process of the skin includes bending and sheet metal, which leads to poor consistency between the skins and is difficult to grasp using traditional manipulators. At present, the main method of sucking the skin is a suction cup, but the suction cup is a soft connection, and its repetitive accuracy of sucking the skin is about 0.5mm, resulting in the existing skin placement method being unable to meet the high-precision requirements of the welding process, especially when the assembly gap needs to be controlled within 0.01mm. Summary of the invention

[0003] In view of the above analysis, an embodiment of the present invention aims to provide a method for automatic placement of skins, so as to solve the technical problem of low precision of skin placement in the prior art.

[0004] In one aspect, an embodiment of the present invention provides a method for automatic skinning placement, the method comprising:

[0005] Teaching the manipulator to perform the task of assembling the skin onto the skeleton, thereby obtaining the skeleton teaching posture, the manipulator teaching path, the skin teaching posture of each path point on the teaching path, and the teaching transformation of the end of the manipulator;

[0006] The skeleton is set at the target position, the skin to be assembled is adsorbed by the end of the manipulator, and the end of the manipulator moves the skin to the preset position along the teaching path according to the teaching transformation;

[0007] The skin and the skeleton are photographed and identified respectively by a visual recognition device, so as to obtain the actual posture of the skin and the actual posture of the skeleton at a preset position;

[0008] Performing visual matching calculation according to the skeleton teaching posture, the skeleton actual posture, the skin teaching posture at the preset position, the skin actual posture and the teaching transformation of the manipulator end to obtain the actual transformation of the manipulator end;

[0009] The end of the manipulator adjusts the posture of the skin according to the actual transformation, and then positions the skin from the preset position to the skeleton.

[0010] Based on the further improvement of the above method, the visual matching calculation is performed according to the following formula to obtain the actual transformation of the end of the manipulator:

[0011]

[0012] Where, T 实际 is the actual transformation of the manipulator end, T 示教 is the teaching transformation of the manipulator at the preset position, T2 is the relative transformation of the skeleton’s posture, and P 2实际 is the actual pose of the skeleton, P 2示教 is the skeleton teaching pose, T1 is the relative transformation of the skin pose, P 1实际 is the actual pose of the skin at the preset position, P 1示教 Teach a pose for the skin at a preset position.

[0013] Based on a further improvement of the above method, the preset position is located directly above the target position, and the distance between the preset position and the target position is 20 mm to 50 mm.

[0014] Based on the further improvement of the above method, the manipulator end adjusts the posture of the skin according to the actual transformation, and then positions the skin from the preset position to the skeleton, including:

[0015] Disposing a plurality of guide devices along the edge of the skeleton at the target position;

[0016] After the end of the manipulator adjusts the posture of the skin according to the actual transformation, the skin is positioned and placed on the skeleton from the preset position under the limitation of the guiding device.

[0017] Based on the further improvement of the above method, the guide device includes: a base and a guide column, wherein the guide column is elastically connected to the base, and the outer wall of the guide column is used to contact the skin.

[0018] Based on the further improvement of the above method, the manipulator end adjusts the posture of the skin according to the actual transformation, and then positions the skin from the preset position to the skeleton, and further includes:

[0019] When the manipulator moves the skin to the preset position, the force condition at the end of the manipulator begins to be detected;

[0020] The manipulator is flexibly controlled according to the force conditions until the manipulator positions the skin on the skeleton.

[0021] Based on the further improvement of the above method, the manipulator is flexibly controlled according to the force condition, including:

[0022] Converting the external force on the end of the manipulator into a speed adjustment amount and / or a position adjustment amount;

[0023] The speed of the end of the manipulator is adjusted according to the speed adjustment amount, and / or the moving distance of the end of the manipulator is adjusted according to the position adjustment amount.

[0024] Based on the further improvement of the above method, the force condition of the manipulator is detected by a force control sensor, and the force control sensor is arranged on the manipulator.

[0025] Based on the further improvement of the above method, the skin to be assembled is adsorbed by the end of the manipulator, including the following steps:

[0026] Get the coordinates of the grab points of the skin to be assembled;

[0027] The end of the manipulator absorbs the skin to be assembled according to the coordinates of the grasping point and moves the skin to the preset position.

[0028] Based on the further improvement of the above method, the step of obtaining the coordinates of the grabbing points of the skin to be assembled includes:

[0029] Assemble the skin template to the skeleton template;

[0030] Identifying the coordinates of the fitting points between the skin template and the skeleton template by a visual recognition device;

[0031] The coordinates of at least three of the fitting points are selected as the grabbing point coordinates.

[0032] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0033] 1. In the present invention, after the end of the manipulator absorbs the skin to be assembled and moves it to a preset position, the actual postures of the skin and the skeleton are respectively identified by a visual recognition device for visual matching, so as to adjust the teaching transformation of the end of the manipulator, thereby realizing the correction of the skin posture, which can offset the adsorption error caused by soft connections such as adsorption connections, obtain accurate placement posture, and improve the accuracy of skin placement.

[0034] 2. In the present invention, by setting a guide device at the target position, the manipulator can be assisted to accurately place the skin on the frame, thereby reducing the positioning deviation caused by the suction error of the suction cup.

[0035] 3. In the present invention, while the guide device is guiding, the manipulator is flexibly controlled according to the force conditions at the end thereof, ensuring that the robot can operate with appropriate force and speed, avoiding damage to the skin, and enabling the manipulator to achieve efficient, safe and precise operation.

[0036] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0038] Figure 1 This is a flow chart of the automatic skin placement method according to an embodiment of the present invention.

[0039] Figure 2 A schematic diagram of an automated skin placement process according to an embodiment of the present invention;

[0040] Figure 3 Schematic diagram of the structure of the guide device according to an embodiment of the present invention.

[0041] Reference numerals:

[0042] 1. Manipulator; 2. Guide device; 3. Skin; 4. Skeleton;

[0043] 21 - base; 22 - guide column; 221 - straight section; 222 - inclined section. DETAILED DESCRIPTION

[0044] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0045] A specific embodiment of the present invention discloses a method for automatic placement of skins, such as Figure 1 and Figure 2 The method comprises:

[0046] Step 00, teaching the manipulator 1 to perform the task of assembling the skin 3 onto the skeleton 4, thereby obtaining the skeleton teaching posture, the manipulator 1 teaching path, the skin teaching posture of each path point on the teaching path, and the teaching transformation of the end of the manipulator 1;

[0047] Step 10, setting the skeleton 4 at the target position, adsorbing the skin 3 to be assembled by the end of the manipulator 1, and moving the skin 3 to the preset position along the taught path according to the taught transformation by the end of the manipulator 1;

[0048] Step 20, photographing and identifying the skin 3 and the skeleton 4 respectively by a visual recognition device, so as to obtain the actual posture of the skin and the actual posture of the skeleton at the preset position;

[0049] Step 30, performing visual matching calculation according to the skeleton teaching posture, the skeleton actual posture, the skin teaching posture at the preset position, the skin actual posture and the teaching transformation of the end of the manipulator 1 to obtain the actual transformation of the end of the manipulator 1;

[0050] In step 40 , the end of the manipulator 1 adjusts the posture of the skin 3 according to the actual transformation, and then positions the skin 3 from the preset position onto the skeleton 4 .

[0051] During implementation, a suction device, such as a plurality of suction cups, is provided at the end of the manipulator 1 for sucking the skin 3 .

[0052] Compared with the prior art, in the embodiment of the present invention, considering that the adsorption connection is a soft connection, an adsorption error will occur after the end of the manipulator 1 adsorbs the skin 3, which will cause the posture of the skin 3 to deviate, and this deviation cannot be accurately estimated. Therefore, after the end of the manipulator 1 absorbs the skin 3 to be assembled, the actual postures of the skin 3 and the skeleton 4 are respectively identified by a visual recognition device for visual matching, so as to adjust the teaching transformation of the end of the manipulator 1, thereby realizing the correction of the posture of the skin 3, which can offset the adsorption error caused by soft connections such as the adsorption connection, obtain accurate placement posture, and improve the accuracy of the placement of the skin 3.

[0053] Step 00, teaching the manipulator 1 to perform the task of assembling the skin 3 onto the skeleton 4, thereby obtaining the skeleton teaching posture, the manipulator 1 teaching path, the skin teaching posture of each path point on the teaching path, and the teaching transformation of the end of the manipulator 1.

[0054] Before the actual assembly task is performed, the process of assembling the skin 3 to the skeleton 4 can be simulated by teaching, so as to ensure that the manipulator 1 accurately learns and replicates the assembly action. The teaching path of the manipulator 1, the teaching posture of the skin at each path point on the teaching path, the teaching transformation of the end of the manipulator 1, and the teaching posture of the skeleton can be obtained through teaching.

[0055] The skin teaching posture and the skeleton teaching posture refer to the positions and directions of the skin 3 and the skeleton 4 in the robot coordinates determined by the teaching method. Specifically, during teaching, the operator sets the skin teaching posture and the skeleton teaching posture respectively according to the assembly environment and task requirements of the skin 3.

[0056] The teaching path refers to the moving trajectory of the robot 1 when performing an assembly task, and the teaching transformation refers to the specific position and direction of the end of the robot 1 on the moving trajectory.

[0057] It should be noted that the front and back sides of the skeleton 4 are respectively installed with a front skin and a back skin. That is, the skin 3 includes two types of skins, namely, the front skin and the back skin. The two different types of skins 3 need to be taught by robots separately.

[0058] Step 10, setting the skeleton 4 at the target position, adsorbing the skin 3 to be assembled by the end of the manipulator 1, and making the manipulator 1 move the skin 3 to the preset position along the taught path according to the taught transformation.

[0059] During implementation, the manipulator 1 first moves to a preset initial position, and then moves from the initial position to the storage position of the skin 3, so that its end adsorbs a skin 3 to be assembled. After adsorbing the skin 3, the manipulator 1 moves to the preset position according to the taught path, and then after visual matching and assembling the skin 3 to the skeleton 4, the manipulator 1 returns to the initial position to prepare to execute the assembly task of the next skin 3.

[0060] Specifically, the preset position is located directly above the target position, and the distance between the preset position and the target position is 20 mm to 50 mm.

[0061] In the embodiment of the present invention, the preset position is a position close to the skeleton 4. In other words, in the embodiment of the present invention, the manipulator 1 first moves the skin 3 to a position close to the skeleton 4 to adjust the posture of the skin 3, which can not only eliminate the adsorption error, but also reduce the cumulative error generated during the movement process, thereby more accurately controlling the positioning and installation of the skin 3. Specifically, the skin 3 to be assembled is adsorbed by the end of the manipulator 1, including the following steps:

[0062] Obtaining the coordinates of the grabbing point of the skin 3 to be assembled;

[0063] The end of the manipulator 1 absorbs the skin 3 to be assembled according to the coordinates of the grasping point, and moves the skin 3 to the preset position.

[0064] During implementation, the suction cup at the end of the manipulator 1 is adsorbed on the grasping point on the skin 3 to control the posture of the skin 3 .

[0065] Specifically, the step of obtaining the coordinates of the grabbing points of the skin 3 to be assembled includes:

[0066] Assemble the skin template to the skeleton template;

[0067] Identifying the coordinates of the fitting points between the skin template and the skeleton template by a visual recognition device;

[0068] The coordinates of at least three of the fitting points are selected as the grabbing point coordinates.

[0069] In this embodiment, the fitting point between the skin 3 and the skeleton 4 is selected as the grasping point, which is conducive to the manipulator 1 to accurately place the skin 3 on the skeleton 4 so that the two fit together.

[0070] It should be noted that, similarly, the skin template includes a front skin template and a reverse skin template, so the above method needs to be used to obtain the grab point coordinates of the front skin 3 and the grab point coordinates of the reverse skin 3. During implementation, the corresponding grab point coordinates are called according to the type of the skin 3 to be assembled.

[0071] Step 20, photographing and identifying the skin 3 and the skeleton 4 respectively by a visual recognition device, so as to obtain the actual posture of the skin and the actual posture of the skeleton at the preset position.

[0072] Specifically, the visual recognition device is a camera, which is used to capture images and perform analysis.

[0073] The visual recognition device determines the actual posture of the skin 3, that is, the position and direction of the skin 3 in space, by analyzing the image of the skin 3. Similarly, the visual recognition device determines the actual posture of the skeleton 4, that is, the position and direction of the skeleton 4 in space, by analyzing the image of the skeleton 4.

[0074] The posture of a workpiece refers to the three-dimensional spatial state of the workpiece in the robot coordinate system, including the position and orientation of the workpiece, where the position is the coordinate of the center point of the workpiece or a preselected reference point in space, and the orientation is the rotation state of the workpiece relative to the robot coordinate system, which can be described by Euler angles (pitch angle, yaw angle, roll angle).

[0075] Step 30 , performing visual matching calculation according to the actual posture of the skin, the actual posture of the skeleton and the teaching transformation of the end of the manipulator 1 at the preset position to obtain the actual transformation of the skin 3 assembly.

[0076] Specifically, the visual matching calculation is performed according to the following formula to obtain the actual transformation of the end of the manipulator 1:

[0077]

[0078]

[0079] Where, T 实际 is the actual transformation of the end of robot 1, T 示教 is the teaching transformation of the end of the manipulator 1 at the preset position, T2 is the relative transformation of the posture of the skeleton 4, and P 2实际 is the actual pose of the skeleton, P 2示教 is the skeleton teaching pose, T1 is the relative transformation of skin 3 pose, P 1实际 is the actual pose of the skin at the preset position, P 1示教Teach a pose for the skin at a preset position.

[0080] It should be noted that, in the assembly task, what is concerned is how to align a specific connection point of a component with the corresponding connection point of another component. Therefore, in the embodiment of the present invention, the posture of the skin 3 refers to the position and direction of the fitting point on the skin 3 and the skeleton 4, and the posture of the skeleton 4 refers to the position and direction of the fitting point on the skeleton 4 and the skin 3.

[0081] Before the robot teaching, the teaching posture of the skin 3 and the teaching posture of the skeleton 4 are set respectively according to the assembly environment of the skin 3 and the task requirements.

[0082] Step 40, the end of the manipulator 1 adjusts the posture of the skin 3 according to the actual transformation, and then positions the skin 3 on the skeleton 4, including:

[0083] A plurality of guide devices 2 are arranged along the edge of the skeleton 4 at the target position; after the end of the manipulator 1 adjusts the posture of the skin 3 according to the actual transformation, the skin 3 is positioned and placed on the skeleton 4 from the preset position under the limitation of the guide device 2.

[0084] In the embodiment of the present invention, Figure 2 As shown in , by setting the guide device 2 at the target position, the manipulator 1 can be assisted to accurately place the skin 3 on the skeleton 4, reducing the positioning deviation caused by the suction cup adsorption error.

[0085] like Figure 3 As shown in , the guide device 2 includes: a base 21 and a guide column 22 , wherein the guide column 22 is elastically connected to the base 21 , and the outer wall of the guide column 22 is used to contact the skin 3 .

[0086] Among them, the outer wall of the guide column 22 is an arc surface, which can ensure that the guide column 22 and the skin 3 are in line contact rather than surface contact. At the same time, the guide column 22 is elastically connected to the base 21, which can balance the external force acting on the skin 3, thereby avoiding damage to the skin 3.

[0087] The guide column 22 includes a connected straight section 221 and an inclined section 222, wherein the inclined section 222 is located above the guide column 22. The upper inclined section 222 facilitates the manipulator 1 to place the skin 3 on the frame 4, and the lower straight section 221 can limit the skin 3.

[0088] Step 40, the end of the manipulator 1 adjusts the posture of the skin 3 according to the actual transformation, and then positions the skin 3 from the preset position to the skeleton 4, and also includes:

[0089] When the manipulator 1 moves the skin 3 to the preset position, the force condition at the end of the manipulator 1 begins to be detected;

[0090] The manipulator 1 is flexibly controlled according to the force conditions until the manipulator 1 positions the skin 3 on the skeleton 4 .

[0091] In the embodiment of the present invention, while the guide device 2 is guiding, the manipulator 1 is flexibly controlled according to the force conditions at the end thereof, ensuring that the robot can operate with appropriate force and speed, avoiding damage to the skin 3, and enabling the manipulator 1 to achieve efficient, safe and precise operation.

[0092] Specifically, when the manipulator 1 approaches the target position, the guide device 2 contacts the skin 3, which applies external force to the skin 3 and transmits it to the manipulator 1. Therefore, by detecting the force condition at the end of the manipulator 1 and flexibly controlling the manipulator 1 according to the force condition, it can be ensured that when the skin 3 contacts the guide device 2 with a certain depth, the skin 3 can be assembled smoothly and accurately even under assembly conditions with a small tolerance.

[0093] Specifically, the force condition of the manipulator 1 is detected by a force control sensor, and the force control sensor is arranged on the manipulator 1. Furthermore, the force control sensor is a six-dimensional force control sensor.

[0094] Specifically, the flexibly controlling the manipulator 1 according to the force condition includes:

[0095] Converting the external force on the end of the manipulator 1 into a speed adjustment amount and / or a position adjustment amount;

[0096] The speed of the end of the manipulator 1 is adjusted according to the speed adjustment amount, and / or the moving distance of the end of the manipulator 1 is adjusted according to the position adjustment amount.

[0097] Among them, the compliance control includes stiffness control, damping control and impedance control. Converting the feedback force signal into a position adjustment is stiffness control; converting the feedback force signal into a speed adjustment is damping control; converting the feedback force signal into both a speed adjustment and a position adjustment is impedance control. In the embodiment of the present invention, any compliance control can be selected according to actual needs.

[0098] Exemplarily, the formula for converting the external force on the end of the manipulator 1 into the speed adjustment amount and / or the position adjustment amount is as follows:

[0099] Δv=k d ·F;

[0100] Δx=k p ·F;

[0101] Where Δv is the speed adjustment, F is the external force at the end of the manipulator 1; k d is the damping coefficient, which is used to determine the intensity of speed adjustment; Δx is the position adjustment amount, k p is the proportional stiffness coefficient, which is used to determine the strength of position adjustment.

[0102] Those skilled in the art will appreciate that all or part of the processes of the above-mentioned embodiments can be implemented by instructing related hardware through a computer program, and the program can be stored in a computer-readable storage medium, wherein the computer-readable storage medium is a disk, an optical disk, a read-only storage memory, or a random access memory, etc.

[0103] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for automatic skin placement, characterized in that: The method comprises: Teaching the manipulator to perform the task of assembling the skin onto the skeleton, thereby obtaining the skeleton teaching posture, the manipulator teaching path, the skin teaching posture of each path point on the teaching path, and the teaching transformation of the end of the manipulator; The skeleton is set at the target position, the skin to be assembled is adsorbed by the end of the manipulator, and the end of the manipulator moves the skin to the preset position along the teaching path according to the teaching transformation; The skin and the skeleton are photographed and identified respectively by a visual recognition device, so as to obtain the actual posture of the skin and the actual posture of the skeleton at a preset position; Performing visual matching calculation according to the skeleton teaching posture, the skeleton actual posture, the skin teaching posture at the preset position, the skin actual posture and the teaching transformation of the manipulator end to obtain the actual transformation of the manipulator end; The end of the manipulator adjusts the posture of the skin according to the actual transformation, and then positions the skin from the preset position to the skeleton.

2. The method according to claim 1, characterized in that Perform visual matching calculation according to the following formula to obtain the actual transformation of the end of the robot: Where, T 实际 is the actual transformation of the manipulator end, T 示教 is the teaching transformation of the end of the manipulator at the preset position, T2 is the relative transformation of the skeleton’s posture, and P 2实际 is the actual pose of the skeleton, P 2示教 is the skeleton teaching pose, T1 is the relative transformation of the skin pose, P 1实际 is the actual pose of the skin at the preset position, P 1示教 Teach a pose for the skin at a preset position.

3. The method according to claim 1 or 2, characterized in that: The preset position is located directly above the target position, and the distance between the preset position and the target position is 20 mm to 50 mm.

4. The method according to claim 1 or 2, characterized in that: The manipulator end adjusts the posture of the skin according to the actual transformation, and then positions the skin from the preset position to the skeleton, including: Disposing a plurality of guide devices along the edge of the skeleton at the target position; After the end of the manipulator adjusts the posture of the skin according to the actual transformation, the skin is positioned and placed on the skeleton from the preset position under the limitation of the guiding device.

5. The method according to claim 4, characterized in that The guide device comprises: a base and a guide column, wherein the guide column is elastically connected to the base, and the outer wall of the guide column is used to contact the skin.

6. The method according to claim 4, characterized in that The manipulator end adjusts the posture of the skin according to the actual transformation, and then positions the skin from the preset position to the skeleton, and further includes: When the manipulator moves the skin to the preset position, the force condition at the end of the manipulator begins to be detected; The manipulator is flexibly controlled according to the force conditions until the manipulator positions the skin on the skeleton.

7. The method according to claim 6, characterized in that The manipulator is flexibly controlled according to the force condition, including: Converting the external force on the end of the manipulator into a speed adjustment amount and / or a position adjustment amount; The speed of the end of the manipulator is adjusted according to the speed adjustment amount, and / or the moving distance of the end of the manipulator is adjusted according to the position adjustment amount.

8. The method according to claim 6, characterized in that The force condition of the manipulator is detected by a force control sensor, and the force control sensor is arranged on the manipulator.

9. The method according to claim 1 or 2, characterized in that: The skin to be assembled is adsorbed by the end of the manipulator, including the following steps: Get the coordinates of the grab points of the skin to be assembled; The end of the manipulator absorbs the skin to be assembled according to the coordinates of the grasping point and moves the skin to the preset position.

10. The method according to claim 9, characterized in that The step of obtaining the coordinates of the grabbing points of the skin to be assembled includes: Assemble the skin template to the skeleton template; Identify the coordinates of the fitting points between the skin template and the skeleton template by a visual recognition device; The coordinates of at least three of the fitting points are selected as the grabbing point coordinates.

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