Robot tail end hole making system and method based on contact type normal correction

Abstract

The invention provides a robot tail end hole making system and method based on contact type normal correction, and relates to the technical field of aeronautical manufacturing and airplane digital assembly. The system is connected with a tail end mechanical arm of the industrial robot through a detachable connecting interface and comprises a hole forming actuator and a control subsystem. The control subsystem is configured to control the hole forming actuator to move to the position, where holes are to be formed, on the wall plate. A hole forming actuator is controlled to make contact with the surface of the wall plate, and normal information of the to-be-formed hole position is detected through a sensor arranged on the hole forming actuator; according to the normal direction information, the adjusting posture of a drilling actuator is controlled, so that the axis of the cutter is consistent with the normal direction of the position to be drilled; by measuring the back-off amount of the wall plate, the hole forming actuator is controlled to compensate the TCP position of the cutter; and after the posture adjustment and the TCP displacement compensation are completed, a hole forming actuator is controlled to complete hole forming machining. According to the invention, the high-precision drilling requirement for aircraft assembly can be met, and support is provided for an aircraft digital assembly technology.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of aviation manufacturing and aircraft digital assembly, and particularly relates to a robot end-hole drilling system and method based on contact normal correction. BACKGROUND

[0002] In aviation manufacturing, aircraft assembly requires a large number of hole drilling operations. Traditional manual hole drilling has problems such as low efficiency and poor accuracy. With the development of automation technology, robot hole drilling systems have gradually been applied to the assembly of small and medium-sized parts, such as aircraft movable wings, due to their flexibility and cost advantage. However, in the existing automation technology, the non-contact normal correction technology based on the laser displacement sensor group currently in use has the following significant defects:

[0003] 1. Normal measurement is disconnected from the processing state: the local deformation of the weak rigid laminated thin wall under the action of one-way compression force changes the normal of the hole drilling area, making it difficult to ensure the hole perpendicularity based on the measurement before compression.

[0004] 2. Poor boundary adaptability: in the boundary hole area, the laser may not hit the wallboard, while in the dense hole area, the laser may enter the processed hole, thereby limiting the application range.

[0005] 3. Complex algorithm and insufficient accuracy: the existing plane fitting algorithm requires calibration of 21 parameters, which is computationally intensive and prone to misoperation; the four-point leveling algorithm relies on zero-point calibration values, and the error of the γ-angle solution increases with the increase of the normal deviation angle, and the wallboard deformation is not considered.

[0006] In summary, although contact normal correction technology has been applied abroad, such as the Boeing 777X tail assembly, this technology still has problems such as poor adaptability of the pressing foot structure and algorithm, insufficient hole position compensation, etc. In China, there is still a gap in the systematic study and engineering application of this technology, especially the lack of efficient and accurate normal correction schemes for weak rigid thin walls. There is an urgent need for a high-precision contact normal correction technology that can detect wallboard deformation in real time and dynamically compensate for hole position deviation. SUMMARY

[0007] To overcome the above-mentioned deficiencies of the prior art, the present application proposes a robot end-hole drilling system and method based on contact normal correction, which aims to solve the problems of disconnection between normal measurement and actual processing state, large hole position deviation, and low efficiency in the process of drilling holes in weak rigid thin walls, improve the hole drilling perpendicularity, hole position accuracy and processing efficiency, meet the high-precision hole drilling requirements in the field of aircraft assembly, and is particularly suitable for spot and hole drilling operations on parts such as aircraft movable wings.

[0008] In one aspect, the present application provides a robot end-hole drilling system based on contact normal correction, which is connected with the end mechanical arm of an industrial robot through a detachable connection interface. The system comprises a hole drilling executor and a control subsystem, wherein the hole drilling executor and the control subsystem are electrically connected.

[0009] The control subsystem is configured to control the hole drilling executor to move to a to-be-drilled position on a wallboard, control the hole drilling executor to contact the wallboard surface and detect the normal information of the to-be-drilled position through a sensor arranged on the hole drilling executor, control the adjustment posture of the hole drilling executor according to the normal information so that the tool axis is consistent with the normal of the to-be-drilled position, control the hole drilling executor to perform TCP position compensation by measuring the wallboard back-off amount, and control the hole drilling executor to complete hole drilling processing after the posture adjustment and TCP displacement compensation are completed.

[0010] Further, the hole drilling executor comprises a spindle module, a spindle feeding module, a cross laser normal searching module, a pressure foot module and a pressure normal searching module.

[0011] The spindle module is used to complete hole drilling processing by driving the tool to rotate.

[0012] The spindle feeding module is connected with the spindle module and is used to drive the spindle module to move along the tool axis, measure the actual feeding distance of the spindle module in real time, and then transmit the measured actual feeding distance to the control subsystem; at the same time, the real-time distance between the hole drilling executor and the to-be-drilled position is measured, and the measured real-time distance is transmitted to the control subsystem.

[0013] The cross laser normal searching module is used to measure the non-contact normal vector of the to-be-drilled position before the pressure foot module contacts the wallboard and transmit the measured non-contact normal vector to the control subsystem.

[0014] The pressure foot module is used to extend to fit the wallboard and be pressed tightly before hole drilling, measure the real-time pressing force in the pressing process and transmit the measured real-time pressing force to the control subsystem; wherein the pressing refers to that the pressing force applied by the pressure foot module to the wallboard reaches a preset value.

[0015] The pressure normal searching module is used to measure the contact normal vector of the to-be-drilled position after the pressure foot module is pressed tightly with the wallboard and transmit the measured contact normal vector to the control subsystem.

[0016] Further, the pressure foot module comprises a pneumatic mechanism, a spherical hinge structure and a pressure sensor, wherein the pneumatic mechanism is connected with the spherical hinge structure through a telescopic rod.

[0017] The pneumatic mechanism is used to drive the telescopic rod to move along the axis direction, thereby driving the spherical hinge structure to extend or retract along the axis direction of the telescopic rod.

[0018] The ball hinge structure is used to produce self-adaptive deflection according to the surface curvature of the wallboard to fit the wallboard during contact with the wallboard.

[0019] The pressure sensor is used to detect the pressing force applied by the pneumatic mechanism on the wallboard in real time and transmit to the control subsystem.

[0020] Further, the functions of the pressure seeking module are realized by a displacement measuring device and a normal vector measuring device; the displacement measuring device is a displacement sensor installed in the ball hinge structure, which is used to measure the axial displacement of the ball hinge structure after the pressure foot module is pressed against the wallboard and transmit to the control subsystem; the normal vector measuring device is a movable guide port with four grating ruler measuring modules built-in, which is used to measure the contact normal vector of the position to be drilled and transmit to the control subsystem; the grating ruler measuring modules are symmetrically distributed, and the movable guide port is an angle-changeable mechanism arranged at the front end of the hole drilling executor.

[0021] Further, the hole drilling executor further comprises:

[0022] A tool changing module is used to automatically change the tool installed on the electric spindle according to the actual hole drilling process requirements.

[0023] A binocular vision module is used to collect images of the position to be drilled and extract feature points, construct the actual coordinate system of the position to be drilled by fitting the feature points, and perform three-dimensional scanning on the position to be drilled and generate a digital point cloud model of the position to be drilled.

[0024] Further, the control subsystem is configured to perform:

[0025] A data acquisition function is used to obtain the actual feeding distance of the spindle module from the spindle feeding module, the real-time distance between the hole drilling executor and the position to be drilled, the non-contact normal vector of the position to be drilled from the cross laser seeking normal module, the real-time pressing force from the pressure foot module, and the contact normal vector of the position to be drilled from the pressure seeking normal module;

[0026] A pose correction function is used to generate distance control instructions and send to the spindle feeding module according to the real-time distance between the hole drilling executor and the position to be drilled, generate preliminary pose adjustment instructions and send to the controller in the industrial robot according to the non-contact normal vector of the position to be drilled, adjust the spatial pose of the hole drilling executor by controlling the movement of the end mechanical arm, and generate accurate pose adjustment instructions and send to the pressure foot module according to the contact normal vector of the position to be drilled when the axial displacement of the ball hinge structure is not zero.

[0027] The compression force adjusting function is used for comparing the preset compression force with the real-time compression force, calculating the difference between the preset compression force and the real-time compression force, generating a compression force control instruction according to the calculated difference, and sending the compression force control instruction to the pneumatic mechanism;

[0028] The TCP displacement compensation function is used for calculating a wallboard back-off amount according to the actual feeding distance of the spindle module, generating a tool position compensation instruction based on the wallboard back-off amount, and sending the tool position compensation instruction to the spindle module.

[0029] In another aspect, the application provides a robot end-hole drilling method based on contact normal correction, which is implemented by using the robot end-hole drilling system based on contact normal correction, and includes the following processes:

[0030] When the hole drilling executor moves above the position to be drilled, the hole drilling executor is subjected to positioning detection and preliminary normal detection, and the hole drilling executor is subjected to preliminary attitude adjustment according to the detection results;

[0031] Based on the current position of the hole drilling executor, the hole drilling executor is attached to and compressed against the position to be drilled, and the hole drilling executor is subjected to accurate attitude adjustment by using the contact normal correction technology;

[0032] In the process of attaching and compressing the hole drilling executor to the position to be drilled, the actual feeding distance of the spindle module in the hole drilling executor is measured, and the wallboard back-off amount is calculated ;

[0033] According to the wallboard back-off amount , a new TCP position is generated by using the TCP displacement compensation method, and the hole drilling executor completes the hole drilling processing according to the new TCP position.

[0034] Further, the method for detecting the positioning and the preliminary normal of the hole drilling executor is as follows:

[0035] The real-time distance between the hole drilling executor and the position to be drilled is obtained, and it is determined whether the real-time distance meets the preset distance requirement; if not, the position of the hole drilling executor is adjusted until it meets the requirement; if yes, the hole drilling executor is subjected to preliminary normal detection;

[0036] The non-contact normal vector of the position to be drilled is obtained, and a unit vector is obtained in a tool coordinate system TCS established in advance;

[0037] The included angle between the non-contact normal vector of the position to be drilled and the unit vector is calculated, and the included angle is taken as the deviation angle between the tool axis and the normal at the position to be drilled at the current time;

[0038] If the deviation angle exceeds the preset deviation angle threshold, the position of the hole making implement is adjusted according to the deviation angle, and the positioning detection and the preliminary normal detection of the hole making implement are performed again;

[0039] If the deviation angle exceeds the preset deviation angle threshold, the preliminary posture adjustment of the hole making implement is completed.

[0040] Further, the specific content of the accurate posture adjustment of the hole making implement by using the contact normal correction technology is as follows:

[0041] The axial displacement of the spherical hinge structure is acquired in real time, and when the axial displacement of the spherical hinge structure is not zero, the contact normal vector of the position to be drilled is acquired;

[0042] The included angle between the contact normal vector of the position to be drilled and the unit vector in the tool coordinate system TCS is calculated, and the included angle is taken as the spatial deviation angle between the tool axis and the normal at the position to be drilled at the current time;

[0043] According to the spatial deviation angle, the spatial posture of the hole making implement is adjusted, the contact normal vector of the adjusted position to be drilled is acquired, and the spatial deviation angle is recalculated until the spatial deviation angle is zero; at this time, it is considered that the tool axis at the current time is consistent with the normal direction at the position to be drilled.

[0044] Further, the wallboard back-off amount The method for generating a new TCP position by using the TCP displacement compensation method is as follows:

[0045] The method for generating a new TCP position by using the TCP displacement compensation method is as follows: The z-axis of the tool coordinate system TCS is defined as the reference direction of the translation compensation;

[0046] An original TCP position is acquired;

[0047] Based on the wallboard back-off amount

[0048] A homogeneous transformation matrix that translates in the reference direction of the translation compensation is constructed;

[0049] The original TCP position is translated by using the homogeneous transformation matrix to generate a new TCP position.

[0050] The beneficial effects produced by the above technical solutions are as follows:

[0051] ​1. High-precision normal detection: The system and method of the present application directly obtains normal information after the wallboard is compressed and deformed through contact measurement of the ball hinge structure, solving the problem of disconnection between measurement and processing state in non-contact technology. Through analysis of test data, the hole verticality deviation is reduced from to , with an improvement of 62.5%.

[0052] 2. Significant improvement in hole position accuracy: The system and method of the present application uses TCP displacement compensation technology to eliminate hole position deviation caused by wallboard rollback. Through analysis of test data, the hole position error is reduced from 0.15mm to 0.03mm, with an improvement of 80%, meeting the hole position accuracy requirements in aircraft assembly.

[0053] 3. Improved processing efficiency: Through analysis of test data, the system and method of the present application reduces the time spent on a single hole from 45s to 32s, with an efficiency improvement of 29%, effectively reducing processing time and meeting the needs of automated production lines.

[0054] 4. Stable and reliable structure: The system and method of the present application are based on ball hinge structure design criteria, ensuring stable contact of the pressure foot with the workpiece during compression and posture adjustment, and achieving automatic resetting of the ball hinge through a connecting spring, reducing mechanical adjustment time; and providing accurate data for normal correction and feed control through high-precision measurement of displacement sensors and grating rulers.

[0055] 5. Strong adaptability: The system and method of the present application are suitable for CFPR, Al, Ti and other weakly rigid laminated thin-walled materials, effectively solving the processing problem of boundary holes and dense hole areas, and expanding the application range of the robot hole making system.

[0056] In summary, the system and method of the present application effectively solve the key technical problems in weakly rigid thin-walled hole making through structural innovation and algorithm optimization, and have significant engineering application value and broad market prospects. BRIEF DESCRIPTION OF DRAWINGS

[0057] Figure 1 is a schematic diagram of a robot end-hole making system based on contact normal correction in the present embodiment;

[0058] Figure 2 is a structural schematic diagram of a robot end-hole making system based on contact normal correction in the present embodiment;

[0059] Figure 3 is a flowchart of a robot end-hole making method based on contact normal correction in the present embodiment;

[0060] Figure 4A flowchart for normal correction of the hole-making implement in the embodiment;

[0061] In the figure: a-process of positioning detection and preliminary normal detection; b-process of contact normal vector detection; c-process of contact normal vector detection; 1-main shaft feeding module; 2-pressure foot module; 3-tool changing module; 4-cross laser normal searching module; 5-binocular vision module; 6-pressure normal searching module. DETAILED DESCRIPTION

[0062] For the convenience of understanding the present application, the specific embodiments of the present application are described in further detail below in combination with the drawings and embodiments. The following embodiments are used to illustrate the present application but are not used to limit the scope of the present application. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0063] Embodiment 1

[0064] A robot end-hole-making system based on contact normal correction in the embodiment is connected with the end mechanical arm of an industrial robot through a detachable connection interface, as shown in Figure 1 and Figure 2 The system comprises a hole-making implement and a control subsystem, wherein the hole-making implement and the control subsystem are electrically connected.

[0065] The control subsystem is configured to control the hole-making implement to move to a to-be-hole-making position on a wallboard, control the hole-making implement to contact the surface of the wallboard and detect the normal information of the to-be-hole-making position through the sensor arranged on the hole-making implement, control the adjustment posture of the hole-making implement according to the normal information so that the tool axis is consistent with the normal of the to-be-hole-making position, control the hole-making implement to perform TCP position compensation by measuring the wallboard back-off amount, and control the hole-making implement to complete hole-making processing after the posture adjustment and TCP displacement compensation are completed.

[0066] The hole-making implement comprises a main shaft module, a main shaft feeding module 1, a cross laser normal searching module 4, a pressure foot module 2 and a pressure normal searching module 6.

[0067] The main shaft module is used to complete hole-making processing by driving the tool to rotate.

[0068] In the embodiment, an electric spindle for driving the tool to rotate is included in the main shaft module, and a drill and scribe integrated tool is installed on the electric spindle. During hole-making processing, different drill tools can be installed on the electric spindle to meet different drilling requirements.

[0069] The spindle feeding module 1 is connected with the spindle module, used for driving the spindle module to move along the tool axis, measuring the actual feeding distance of the spindle module in real time, and transmitting the measured actual feeding distance to the control subsystem; at the same time, measuring the real-time distance between the hole forming executor and the position to be drilled, and transmitting the measured real-time distance to the control subsystem.

[0070] In the embodiment, the spindle feeding module 1 is implemented by a spindle feeding mechanism for controlling the feeding movement of the electric spindle. The spindle feeding mechanism is the main mechanism for drilling and slotting, and is provided with a high-precision grating ruler to accurately measure the tool feeding amount. The spindle feeding mechanism specifically comprises a ram module, a supporting plate module, a feeding guide rail, a grating ruler measuring module, a screw pair transmission module and a laser ranging module. The supporting plate module is fixedly connected with the shell of the hole forming executor. The ram module is installed on the supporting plate module through the feeding guide rail, and the electric spindle is fixedly installed on the ram module. The screw pair transmission module is fixedly connected with the ram module, and drives the ram module to reciprocate along the feeding guide rail direction through a servo motor, thereby driving the electric spindle to move in feeding. The grating ruler measuring module is installed on the supporting plate module. The grating ruler measuring module comprises a grating ruler, a grating ruler reading head and a signal processing circuit. The grating ruler is installed on the feeding guide rail. The grating ruler reading head is installed on the ram module, used for reading the grating ruler and transmitting the read value to the signal processing circuit. The signal processing circuit is used for converting the received value into the feeding distance of the electric spindle and transmitting it to the control subsystem. The laser ranging module is installed at the front end of the ram module, used for measuring the distance between the hole forming executor and the position to be drilled on the wallboard before drilling, and transmitting the measured distance to the control subsystem.

[0071] It should be noted that during the hole drilling process, there are two sensors at both ends of the screw in the feeding direction, which can limit the movement range of the feeding movement, ensure that the electric spindle does not collide with the shell of the hole forming executor, and ensure the safety of the hole drilling process.

[0072] The cross laser seeking method module 4 is used for measuring the non-contact normal vector of the position to be drilled before the pressure foot module 2 contacts the wallboard and transmitting it to the control subsystem.

[0073] In the embodiment, the cross laser module 4 emits specific cross laser lines through a cross line laser. The cross laser lines provide accurate and uniform laser line segments, which can adapt to the skin colors of black, green, silver, etc. The cross laser module also includes an industrial camera and an image processing unit. The industrial camera is used to collect the cross laser line projection image projected on the wallboard and transmit it to the image processing unit. The image processing unit receives the cross laser line projection image collected by the industrial camera, calculates the projection point coordinates of the cross laser line based on the cross laser line projection image using a pre-set image processing algorithm, and then calculates the non-contact normal vector of the to-be-made hole position by fitting the projection point coordinates and transmits it to the control subsystem.

[0074] The laser axis of the cross laser line and the position equation of the hole making executor have been pre-calibrated and form a measurement normal function with the vision system.

[0075] The pressure foot module 2 is used to extend to fit the wallboard and press tightly before making holes, measure the real-time pressing force during the pressing process and transmit it to the control subsystem; wherein the pressing refers to the pressing force applied by the pressure foot module to the wallboard reaching a preset value.

[0076] In the embodiment, the preset value of the pressing force is 200N-400N, which is used to eliminate the product layer gap and reduce the hole burr.

[0077] The pressure foot module 2 includes a pneumatic mechanism, a ball hinge structure and a pressure sensor; wherein the pneumatic mechanism is connected with the ball hinge structure through a telescopic rod.

[0078] The pneumatic mechanism is used to drive the telescopic rod to move along the axis direction, and then drive the ball hinge structure to extend or retract along the axis direction of the telescopic rod.

[0079] In the embodiment, the pressure foot module applies pressure to the aircraft wallboard through the pneumatic mechanism, and the pressure can be adjusted through the pressure regulating valve in the pneumatic mechanism to complete the process of fitting, pressing and retracting the ball hinge structure with the wallboard.

[0080] The ball hinge structure is used to produce adaptive deflection according to the surface curvature of the wallboard during contact with the wallboard to fit the wallboard.

[0081] In the embodiment, the ball hinge structure comprises a nose, a ball hinge, a connecting spring and a dust cover. The nose is in the form of a boss with an inner diameter of 30 mm, which increases the contact area to prevent instability and reduces the normal detection principle error. The ball hinge is divided into a front half and a rear half. The front half is fixed to the nose and can rotate within ±5° around the center of the ball. The rear half is fixed to the shell of the hole making implement. The connecting spring is connected between the front half and the rear half of the ball hinge to keep it in tension and achieve automatic reset of the nose. In addition, a displacement sensor is installed between the front half and the rear half of the ball hinge to measure the displacement of the front half of the ball hinge in the direction of the shaft of the telescopic rod.

[0082] The contact area of the nose is larger than the minimum contact area of the workpiece after deformation, and the critical value of the minimum contact area is ; and the rotational stiffness of the ball hinge is not less than .

[0083] The pressure seeking method module 6 is used to measure the contact normal vector of the position to be drilled after the pressure foot module 2 is pressed against the wallboard and transmit it to the control subsystem.

[0084] The function of the pressure seeking method module 6 is realized by a displacement measuring device and a normal vector measuring device. The displacement measuring device is a displacement sensor installed in the ball hinge structure, which is used to measure the axial displacement of the ball hinge structure after the pressure foot module 2 is pressed against the wallboard and transmit it to the control subsystem. The normal vector measuring device is a movable guide port with four built-in grating ruler measuring modules, which is used to measure the contact normal vector of the position to be drilled and transmit it to the control subsystem. The grating ruler measuring modules are symmetrically distributed, and the movable guide port is a mechanism with changeable angle installed at the front end of the hole making implement.

[0085] In the embodiment, there is a movable guide port with changeable angle at the front end of the hole making implement. During drilling, the cutter protrudes from the movable guide port. Inside the movable guide port, there are four built-in grating ruler reading heads. When the movable guide port of the hole making implement contacts the surface of the wallboard, the movable guide port will fit the surface of the wallboard, and the grating ruler used in cooperation with the grating ruler reading head is connected with the movable guide port. Then, the normal angle of the surface of the wallboard is obtained through the reading change of the grating ruler, that is, based on the pre-calibrated system geometric parameters, the spatial deflection angle of the movable guide port is calculated as the contact normal vector of the position to be drilled according to the displacement signals read by the four grating ruler reading heads.

[0086] In the present embodiment, the pressure normal module is an important module for online measurement and processing of the late normal, which is applicable to normal fine tuning and compensation for slight normal changes caused by pressure. The function of the pressure normal module is realized by a displacement sensor installed between the front half and the rear half of the ball joint. The displacement sensor is used to measure the displacement of the front half of the ball joint in the direction of the telescopic rod axis, i.e. the axial displacement of the ball joint structure. When the front half of the ball joint is displaced in the direction of the telescopic rod axis, it is considered that the hole making implement still has a normal offset, so that normal correction is performed according to the contact normal vector of the position to be drilled. In addition, the pressure normal module uses a high-precision analog transmitter, combined with the mathematical algorithm of the plane equation, for programming adjustment.

[0087] The hole making implement further comprises:

[0088] The tool changing module 3 is used to automatically change the tool mounted on the electric spindle according to the actual hole making process requirements.

[0089] In the present embodiment, the tool changing module 3 provides a transverse translation function through a set of feed mechanisms to switch the equipment and tools in the machining axis position. When tool changing is required, the electric spindle is translated through the screw motion. Similarly, there are two sensors at both ends of the tool changing screw to ensure that the tool changing motion of the electric spindle does not exceed the stroke range.

[0090] The binocular vision module 5 is used to collect images of the position to be drilled and extract feature points, construct an actual coordinate system of the position to be drilled by fitting the feature points, and perform three-dimensional scanning on the position to be drilled to generate a digital point cloud model of the position to be drilled.

[0091] In the present embodiment, the binocular vision module 5 should have the function of fitting the coordinate system of a rigid structure with multiple points. The receiving wave band should be able to switch between a specific wave band and a natural light wave band. This system is conducive to learning and understanding how vision and the end and the robot work together. The binocular vision module should also have a 3D scanning function as an extension of vision. The 3D scanning function can scan the information of the panel and rib parts into the computer to form a 3D point cloud mode, thereby providing a data basis for analyzing the deformation and position compensation of the aircraft panel.

[0092] The control subsystem is configured to perform:

[0093] The data acquisition function is used to obtain the actual feed distance of the spindle module from the spindle feed module, the real-time distance between the hole making implement and the position to be drilled, the non-contact normal vector of the position to be drilled from the cross laser normal module, the real-time pressing force from the pressure foot module, and the axial displacement of the ball joint structure and the contact normal vector of the position to be drilled from the pressure normal module.

[0094] The posture correction function is used to generate distance control instructions according to the real-time distance between the hole-making implement and the position to be drilled and send the distance control instructions to the spindle feeding module; generate preliminary posture adjustment instructions according to the non-contact normal vector of the position to be drilled and send the preliminary posture adjustment instructions to the controller in the industrial robot to adjust the spatial posture of the hole-making implement by controlling the movement of the end mechanical arm; when the axial displacement of the spherical hinge structure is not zero, generate accurate posture adjustment instructions according to the contact normal vector of the position to be drilled and send the accurate posture adjustment instructions to the pressure foot module.

[0095] In the embodiment, whether the hole-making implement needs to continue to move is determined according to the real-time distance between the hole-making implement and the position to be drilled, distance control instructions are generated according to the determination result and sent to the spindle feeding module, and the process is repeated until the real-time distance between the hole-making implement and the position to be drilled meets the preset distance requirement. The preliminary posture adjustment instructions are generated by solving the deviation between the non-contact normal vector of the position to be drilled and the ideal normal vector and sent to the controller in the industrial robot, and the spatial posture of the hole-making implement is adjusted by controlling the movement of the end mechanical arm. When the axial displacement of the spherical hinge structure is not zero, the accurate posture adjustment instructions are generated by solving the deviation between the contact normal vector of the position to be drilled and the ideal normal vector and sent to the spherical hinge structure of the pressure foot module, the spatial posture of the hole-making implement is adjusted by rotating the rear half of the spherical hinge around the spherical center, and the tool axis is consistent with the normal of the position to be drilled. If the axial displacement of the spherical hinge structure is zero, it is considered that the hole-making implement does not have normal deviation.

[0096] The compression force adjustment function is used to compare the preset compression force with the real-time compression force, calculate the difference between the preset compression force and the real-time compression force, generate compression force control instructions according to the calculated difference, and send the compression force control instructions to the pneumatic mechanism.

[0097] In the embodiment, if the real-time compression force is less than the preset compression force, the generated compression force control instructions for continuing to apply pressure are generated and sent to the pneumatic mechanism; otherwise, the generated compression force control instructions for stopping applying pressure are generated and sent to the pneumatic mechanism; thereby realizing closed-loop control of the compression force.

[0098] The TCP displacement compensation function is used to calculate the wall panel back-off amount according to the actual feeding distance of the spindle module, generate tool position compensation instructions based on the wall panel back-off amount, and send the tool position compensation instructions to the spindle feeding module.

[0099] In the embodiment, the data acquisition function, the posture correction function, the pressing force adjustment function and the TCP displacement compensation function can be realized by a central controller integrating multiple function modules. The software system running on the central controller includes a software device model loading module, which can load data models of different robots and their end-hole-making actuators, and can adjust the posture of the data model according to the zero point of the robot. The software system has a workpiece model loading function, which can add different product models. The position of the model is a theoretical position, which can be reset by using a Jacobian matrix transformation. The deviation between the theoretical model and the actual model can be automatically corrected in combination with the end visual system. The point normal extraction function can import point data in a spreadsheet and extract normal data therefrom. The digital twin module collects motion data of the actual robot through a TCP / IP interface and synchronizes the motion of the robot model with the actual position. The software system has a visual acquisition function, which can fit the coordinate system of a rigid structure and correct the BASE value of the robot to adapt to subsequent production requirements. In addition, the software system also has the ability to work with laser structured light. The normal vector of the hole to be made is calculated in cooperation with the laser structured light.

[0100] In the embodiment, the tool coordinate origin is determined by manual operation before the hole-making actuator moves to the working position, and the industrial robot equipped with the hole-making actuator can automatically convert the tool coordinate origin to the mechanical arm flange coordinate origin; the workpiece coordinate system and the coordinate system of the tool changer are determined, and the industrial robot automatically calculates the positional relationship between the coordinate systems according to the workpiece coordinate system, the coordinate system of the tool changer and the preset robot body base coordinate, so as to determine the motion trajectory of the industrial robot and the action sequence of the industrial robot through programming.

[0101] When the mechanical arm drives the hole-making actuator to the working position, the hole-making actuator is attached to the wall surface where the hole to be made is located. When the pressure normal module detects that the readings of the four grating rulers change, the changed numerical relationship is converted into the normal of the surface where the hole to be made is located through a specific mathematical formula, and then fed back to the industrial robot. The industrial robot adjusts the pose of the hole-making actuator so that the spindle axis coincides with the normal, and then starts to make holes.

[0102] Embodiment 2

[0103] The robot end-hole-making method based on contact normal correction in the embodiment is implemented by using a robot end-hole-making system based on contact normal correction, as shown in Figure 3 The method includes the following processes:

[0104] When the hole-making actuator moves above the hole to be made, the hole-making actuator is positioned and detected and preliminarily detected, and the hole-making actuator is preliminarily adjusted in posture according to the detection results.

[0105] The method for positioning detection and preliminary normal detection of the hole making implement is:

[0106] The real-time distance between the hole making implement and the hole making position is obtained, and it is determined whether the real-time distance meets the preset distance requirement. If not, the position of the hole making implement is adjusted until it meets the requirement. If it meets the requirement, the hole making implement is subjected to preliminary normal detection.

[0107] The non-contact normal vector of the hole making position is obtained, and a unit vector in the tool coordinate system TCS is obtained.

[0108] The included angle between the non-contact normal vector of the hole making position and the unit vector is calculated, and the included angle is taken as the deviation angle between the tool axis and the normal at the hole making position at the current time.

[0109] If the deviation angle exceeds the preset deviation angle threshold, the position of the hole making implement is adjusted according to the deviation angle, and the hole making implement is subjected to positioning detection and preliminary normal detection again.

[0110] If the deviation angle exceeds the preset deviation angle threshold, the preliminary pose adjustment of the hole making implement is completed.

[0111] Based on the current position of the hole making implement, the hole making implement is attached to and pressed against the hole making position, and the hole making implement is subjected to accurate pose adjustment by using the contact normal correction technology.

[0112] In the embodiment, as shown in Figure 4 When the nose tip of the pressure foot module contacts the surface of the wallboard and reaches the preset pressing force, the nose tip and the front half part of the ball hinge structure connected thereto will produce self-adaptive deflection under the reaction force of the curved surface to completely attach to the curved surface. The deflection movement is detected in real time by a plurality of grating scales integrated in the ball hinge structure, and the contact normal vector of the hole making position is solved based on the pre-accurately calibrated ball hinge geometric model and combined with the geometric parameters of the ball hinge structure.

[0113] The specific content of the accurate pose adjustment of the hole making implement by using the contact normal correction technology is:

[0114] The axial displacement of the ball hinge structure is obtained in real time, and the contact normal vector of the hole making position is obtained when the axial displacement of the ball hinge structure is not zero.

[0115] The included angle between the contact normal vector of the hole making position and the unit vector in the tool coordinate system TCS is calculated, and the included angle is taken as the spatial deviation angle between the tool axis and the normal at the hole making position at the current time.

[0116] Based on the spatial deviation angle, the spatial attitude of the hole-making actuator is adjusted, the contact normal vector of the adjusted hole position is obtained, and the spatial deviation angle is recalculated until the spatial deviation angle is zero; at this time, it is assumed that the tool axis is consistent with the normal direction at the hole position.

[0117] During the process of fitting and clamping the hole-making actuator to the position of the hole to be made, the actual feed distance of the spindle module in the hole-making actuator is measured, and the wall plate retraction amount is calculated. .

[0118] In this embodiment, the wall panel retraction amount refers to the difference between the theoretical feed distance and the actual feed distance. Normally, the theoretical feed distance is set to 0 by default.

[0119] Based on the wall panel retraction amount A new TCP position is generated using the TCP position change compensation method, and the hole-making actuator completes the hole-making process according to the new TCP position.

[0120] The amount of wall panel retraction The method for generating a new TCP position using TCP position compensation is as follows:

[0121] The z-axis of the tool coordinate system TCS is defined as the reference direction for translation compensation.

[0122] Obtain the raw TCP location.

[0123] Based on panel retraction Construct a translation along the reference direction of the translation compensation. The homogeneous transformation matrix.

[0124] The original TCP position is translated using a homogeneous transformation matrix to generate a new TCP position.

[0125] In this embodiment, the original TCP position is translated along the z-axis of the TCS by the value of the wall panel retraction amount to obtain a new TCP position. This achieves dynamic translation of the TCP position along the z-axis, making the new TCP coincide with the deformed hole position and eliminating the influence of the wall panel retraction.

[0126] The homogeneous transformation matrix is ​​expressed as:

[0127]

[0128] in For the new TCP location; This is the original TCP location; This refers to the amount of wall panel retraction.

[0129] In this embodiment, the pressing force is monitored in real time during the hole making process, so that the fluctuation range of the real-time pressing force does not exceed ±5N, ensuring the stability of the interlamination gap, thereby ensuring the stable progress of the hole making process. The hole making executor executes the hole making and counterbore instructions according to the adjusted pose and new TCP position, retracts the presser foot after completing the machining, and enters the next hole machining process.

[0130] Embodiment 3

[0131] In this embodiment, a test platform for verifying the effectiveness of a robot end hole making system and method based on contact normal correction is built, which specifically includes:

[0132] In order to realize the hole making process on a certain type of aircraft movable wing surface CFRP / Al laminated wallboard with a thickness of 4mm-9mm, 2A12 aluminum alloy with a size of 340mm*115mm and a thickness of 2mm is selected as the test plate to carry out the test.

[0133] A KUKA KR420 R3330 robot is selected, and the robot end hole making system based on contact normal correction, a laser tracker with a precision of ±5μm, and a Hexagon three-coordinate measuring instrument are installed on the robot end mechanical arm. The robot end hole making system based on contact normal correction contains a self-made contact pressure foot module with a spherical hinge structure and a displacement sensor. Meanwhile, a drill and counterbore integrated tool with a model of FQ60500 CARBIDE TOOL is selected as the hole making tool, and the diameter is 4.91mm.

[0134] Firstly, the test plate is fixed on the product tooling, and the world coordinate system, the robot base coordinate system, the flange coordinate system, the tool coordinate system and the product coordinate system are established by using the laser tracker.

[0135] Secondly, five control instructions containing the information of the target point and pose to be drilled, normal detection, normal pose adjustment, hole making and counterbore, etc. are sequentially issued to the robot end hole making system based on contact normal correction.

[0136] Finally, all the control instructions are executed in sequence, and the specific process is divided into: positioning stage, pressing detection stage, dynamic compensation stage and machining stage. In the positioning stage, the pressure foot module moves above the position to be drilled, and is positioned by the cross laser seeking module; in the pressing detection stage, the pressure foot module is extended, so that the nose tip is attached to the workpiece surface, and the normal vector is detected by the displacement sensor; in the dynamic compensation stage, the pose of the hole making executor is adjusted to make the tool axis consistent with the normal, the wallboard retreat amount is measured and the TCP is translated to a new position; in the machining stage, the hole making and counterbore operations are executed, and the three-coordinate measuring instrument is used to measure the hole perpendicularity and hole position deviation, and the counterbore depth measuring instrument is used to detect the counterbore depth.

[0137] After the above control instruction is completed, the test is ended.

[0138] Then, a comparative test is conducted by using the existing non-contact hole forming method, and the test results of the robot end hole forming system and method based on the contact normal correction and the test results of the existing non-contact hole forming method are compared and analyzed, as shown in Table 1.

[0139] Table 1 Comparison table of test results

[0140] Indicator Non-contact Contact (application) Lifting range Perpendicularity deviation 0.8°-1.2° 0.3°-0.5° 62.5% Hole position error 0.15mm 0.03mm 80% Single-hole time-consuming 45s 32s 29%

[0141] The test results show that the robot end hole forming system and method based on the contact normal correction significantly improves the hole forming precision and efficiency, the perpendicularity qualified rate reaches 98%, and the hole position deviation is less than 0.03 mm, which meets the hole forming precision requirements in the field of aircraft assembly.

[0142] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope defined by the present application.

Claims

1. A robot end-effector hole-making system based on contact-type normal correction, wherein the robot end-effector hole-making system is connected to the end effector of an industrial robot via a detachable connection interface, characterized in that, The system includes: a hole-making actuator and a control subsystem; wherein the hole-making actuator and the control subsystem are electrically connected; The control subsystem is configured to: control the hole-making actuator to move to the position of the hole to be made on the wall plate; control the hole-making actuator to contact the surface of the wall plate and detect the normal information of the position of the hole to be made through a sensor installed on the hole-making actuator; control the hole-making actuator to adjust its posture according to the normal information so that the tool axis is consistent with the normal of the position of the hole to be made; control the hole-making actuator to perform TCP position compensation by measuring the wall plate retraction amount; and control the hole-making actuator to complete the hole-making process after completing the posture adjustment and TCP displacement compensation.

2. The robot end-effector hole-making system based on contact-type normal correction according to claim 1, characterized in that, The hole-making actuator includes: a spindle module, a spindle feed module, a cross laser homing module, a pressure foot module, and a pressure homing module; The spindle module is used to complete hole-making by driving the tool to rotate; The spindle feed module is connected to the spindle module and is used to drive the spindle module to feed along the tool axis. It also measures the actual feed distance of the spindle module in real time and transmits the measured actual feed distance to the control subsystem. At the same time, it measures the real-time distance between the hole-making actuator and the position of the hole to be made and transmits the measured real-time distance to the control subsystem. The cross laser homing module is used to measure the non-contact normal vector of the hole to be drilled position and transmit it to the control subsystem before the pressure foot module contacts the wall plate. The pressure foot module is used to extend before drilling to fit and press against the wall panel, measure the real-time pressing force during the pressing process and transmit it to the control subsystem; wherein the pressing refers to the pressing force applied by the pressure foot module to the wall panel reaching a preset value; The pressure-finding module is used to measure the contact normal vector of the hole to be drilled after the pressure foot module is pressed against the wall panel and transmit it to the control subsystem.

3. The robot end-effector hole-making system based on contact-type normal correction according to claim 2, characterized in that, The pressure foot module includes: a pneumatic mechanism, a ball joint structure, and a pressure sensor; wherein the pneumatic mechanism is connected to the ball joint structure via a telescopic rod. The pneumatic mechanism is used to drive the telescopic rod to move along the axial direction, thereby causing the ball joint structure to extend or retract along the axial direction of the telescopic rod. The ball joint structure is used to generate adaptive deflection according to the surface curvature of the wall panel during contact with the wall panel, so as to fit the wall panel. The pressure sensor is used to detect the clamping force applied to the wall panel by the pneumatic mechanism in real time and transmit it to the control subsystem.

4. The robot end-effector hole-making system based on contact-type normal correction according to claim 3, characterized in that, The function of the pressure-finding module is achieved through a displacement measuring device and a normal vector measuring device. The displacement measuring device is a displacement sensor installed in the ball joint structure, used to measure the axial displacement of the ball joint structure after the pressure foot module is pressed against the wall panel and transmit it to the control subsystem. The normal vector measuring device is a movable guide port with four built-in grating ruler measuring modules, used to measure the contact normal vector of the hole to be drilled and transmit it to the control subsystem. The grating ruler measuring modules are symmetrically distributed, and the movable guide port is a mechanism with an adjustable angle located at the front end of the hole-making actuator.

5. The robot end-effector hole-making system based on contact-type normal correction according to claim 4, characterized in that, The hole-making actuator also includes: The tool changing module is used to automatically change the tools mounted on the electric spindle according to the actual hole-making process requirements. The binocular vision module is used to acquire images of the location of the hole to be drilled and extract feature points. By fitting the feature points, the actual coordinate system of the location of the hole to be drilled is constructed. The location of the hole to be drilled is then scanned in three dimensions and a digital point cloud model of the location of the hole to be drilled is generated.

6. The robot end-effector hole-making system based on contact-type normal correction according to claim 4, characterized in that, The control subsystem is configured to execute: The data acquisition function is used to acquire the actual feed distance of the spindle module from the spindle feed module and the real-time distance between the hole-making actuator and the hole position, the non-contact normal vector of the hole position from the cross laser locator module, the real-time clamping force from the pressure foot module, and the contact normal vector of the hole position from the pressure locator module. The attitude correction function is used to generate a distance control command and send it to the spindle feed module based on the real-time distance between the hole-making actuator and the position of the hole to be made; to generate a preliminary attitude adjustment command based on the non-contact normal vector of the position of the hole to be made and send it to the controller in the industrial robot, thereby adjusting the spatial attitude of the hole-making actuator by controlling the movement of the end effector; when the axial displacement of the ball joint structure is not zero, a precise attitude adjustment command is generated based on the contact normal vector of the position of the hole to be made and sent to the pressure foot module. The clamping force adjustment function is used to compare the preset clamping force with the real-time clamping force, calculate the difference between the preset clamping force and the real-time clamping force, generate a clamping force control command based on the calculated difference, and send it to the pneumatic mechanism. The TCP displacement compensation function is used to calculate the wall plate retraction amount based on the actual feed distance of the spindle module, generate a tool position compensation command based on the wall plate retraction amount, and then send the tool position compensation command to the spindle module.

7. A robot end-effector hole-making method based on contact-type normal correction, implemented using the robot end-effector hole-making system based on contact-type normal correction as described in any one of claims 1-6, characterized in that, This method includes the following steps: When the hole-making actuator moves above the position of the hole to be made, the hole-making actuator is positioned and preliminarily normalized, and the hole-making actuator is preliminarily adjusted according to the detection results. Based on the current position of the hole-making actuator, the hole-making actuator is attached and pressed against the position of the hole to be made, and the contact normal correction technology is used to make precise attitude adjustment of the hole-making actuator; During the process of fitting and clamping the hole-making actuator to the position of the hole to be made, the actual feed distance of the spindle module in the hole-making actuator is measured, and the wall plate retraction amount is calculated. ; Based on the wall panel retraction amount A new TCP position is generated using the TCP position change compensation method, and the hole-making actuator completes the hole-making process according to the new TCP position.

8. The robot end-effector hole-making method based on contact-type normal correction according to claim 7, characterized in that, The method for positioning detection and preliminary normal detection of the drilling actuator is as follows: The real-time distance between the hole-making actuator and the position of the hole to be made is obtained, and it is determined whether the real-time distance meets the preset distance requirement. If it does not meet the requirement, the position of the hole-making actuator is adjusted until it does. If the conditions are met, a preliminary normal detection is performed on the hole-making actuator; Obtain the non-contact normal vector of the hole to be drilled, and obtain the unit vector in the pre-established tool coordinate system TCS; Calculate the angle between the non-contact normal vector at the location of the hole to be drilled and the unit vector, and use this angle as the deviation angle between the tool axis and the normal at the location of the hole to be drilled at the current moment; If the deviation angle exceeds the preset deviation angle threshold, the position of the hole-making actuator is adjusted according to the deviation angle, and the hole-making actuator is repositioned and preliminarily normalized. If the deviation angle exceeds the preset deviation angle threshold, the initial attitude adjustment of the hole-making actuator is completed.

9. The robot end-effector hole-making method based on contact-type normal correction according to claim 8, characterized in that, The specific details of using contact-type normal correction technology to precisely adjust the attitude of the drilling actuator are as follows: The axial displacement of the ball joint structure is acquired in real time. When the axial displacement of the ball joint structure is not zero, the contact normal vector of the hole to be drilled is acquired. Calculate the angle between the contact normal vector at the position of the hole to be drilled and the unit vector in the tool coordinate system TCS, and use this angle as the spatial deviation angle between the tool axis and the normal at the position of the hole to be drilled at the current moment; Based on the spatial deviation angle, the spatial attitude of the hole-making actuator is adjusted, the contact normal vector of the adjusted hole position is obtained, and the spatial deviation angle is recalculated until the spatial deviation angle is zero; at this time, it is assumed that the tool axis is consistent with the normal direction at the hole position.

10. The method for creating a hole at the end effector of a robot based on contact-type normal correction according to claim 9, characterized in that, The amount of wall panel retraction The method for generating a new TCP position using TCP position compensation is as follows: The amount of wall panel retraction The method for generating a new TCP position using TCP position compensation is as follows: The z-axis of the tool coordinate system TCS is defined as the reference direction for translation compensation; Obtain the raw TCP position; Based on panel retraction Construct a translation along the reference direction of the translation compensation. The homogeneous transformation matrix; The original TCP position is translated using a homogeneous transformation matrix to generate a new TCP position.

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