Automatic hole-making end normal sensor calibration method

Abstract

The application provides an automatic hole-making end normal sensor calibration method and belongs to the field of aviation manufacturing engineering and airplane assembly technology. The application is based on large-scale high-precision measuring equipment such as a laser tracker, and the high-precision calibration of the relative position and angle of each optical normal sensor emission and the tool axis can be completed on the assembly site by means of a specially-made calibration target plate, the influence of the end effector part machining precision and assembly error is significantly reduced, and the hole-making quality and efficiency of the standard part are ensured.

Description

Technical Field

[0001] This invention belongs to the field of aerospace manufacturing engineering and aircraft assembly technology, and relates to a calibration method for an optical normal sensor of an end effector of an automatic hole-making equipment, used for measuring the normal of the surface to be processed during the automatic hole-making process in aircraft assembly. Background Technology

[0002] Developing advanced fighter jets to enhance national defense capabilities is an inevitable path for major powers, especially given the significant improvements in stealth and long service life, which places higher demands on the precision of standard component connections. Hole-making precision has the greatest impact on standard component connections. Automated hole-making / riveting equipment is widely used in aircraft assembly lines to reduce worker labor intensity and ensure the consistency and stability of hole-making quality. To meet the requirements of high stealth and long service life for aircraft, it is urgent to develop high-precision calibration methods for optical normal sensors suitable for automated hole-making, ensuring the perpendicularity of standard component connection holes and thus improving the quality of standard component connections.

[0003] Automated drilling / riveting equipment used in aircraft assembly is generally based on robots or five-axis machine tools. It integrates end effectors to complete tasks such as hole location determination, automatic method finding, hole drilling and countersinking, rivet feeding, and riveting. Aircraft manufacturing processes are complex, and the parts have intricate shapes and low rigidity. The deformation caused by the weight of the components during assembly is significant, and the cumulative effect of manufacturing errors further contributes to the problem. For surface-type parts such as skin panels, the aerodynamic shape deviates greatly from the theoretical shape, severely affecting the perpendicularity of automated drilling. To ensure the perpendicularity of the rivet hole axis to the curved skin surface, an optical normal measurement sensor is installed on the automated drilling equipment. A laser rangefinder measures the normal value at the drilling point, and a background program calculates the actual normal value at that point, guiding the robot or five-axis machine tool to adjust the normal and compensate for the normal deviation. Multiple optical normal sensors are installed on the end effector, arranged around the axis of the drilling tool. The position and angle of the light emitted by each optical normal sensor relative to the tool axis must be precisely calibrated. The mounting position of most optical normal sensors is guaranteed by machining accuracy. However, the end effector has a complex structure and the machining accuracy of its parts is difficult to guarantee. Coupled with assembly errors, there are problems such as large installation errors of optical normal sensors, which will inevitably affect the vertical accuracy of hole making. Summary of the Invention

[0004] To address the aforementioned issues, this invention proposes a calibration method for the optical normal sensors of the end effector in an aircraft automatic hole-making equipment. Based on large-scale, high-precision measuring equipment such as laser trackers, and with the aid of a specially designed calibration target plate, the relative position and angle of each optical normal sensor emission to the tool axis can be calibrated with high precision on the assembly site. This significantly reduces the impact of machining accuracy and assembly errors on the end effector parts, ensuring the quality and efficiency of hole-making for standard parts.

[0005] The technical solution of this invention is as follows:

[0006] A method for calibrating the end-effector normal sensor of an automatic drilling machine is disclosed. This method is based on an automatic drilling end-effector normal sensor calibration system for aircraft. The system includes an end effector 1 (automatic drilling equipment), an optical normal sensor 2, an auxiliary laser tracker ball mount 3, a sensor laser line 4, a calibration target plate 5, a laser tracker ball mount 6, and a light spot projection disk 7. The end effector 1 is fixedly mounted on a CNC machine such as a robot or a five-axis machine tool. Multiple optical normal sensors 2 are installed on the front conical section of the end effector 1, surrounding the brake tool spindle. The auxiliary laser tracker ball mounts 3 are distributed at easily measurable locations on the end effector 1 to quickly establish the end effector coordinate system during calibration. The sensor laser line 4 is the light emitted by the optical normal sensor 2, used to measure the distance between the optical normal sensor 2 and the aircraft skin surface. By combining data from multiple sets of optical normal sensors 2, the angle between the tool spindle of the end effector 1 and the aircraft skin can be calculated, thus providing closed-loop control data support for normal adjustment. The calibration target plate 5 is placed on the ground and its height and angle can be adjusted. A laser tracker ball mount 6 and a light spot projection disk 7 are arranged on it, with the light spot projection disk 7 located at the center of the calibration target plate 5. Figure 2 As shown. The specific calibration method is as follows:

[0007] 1) Calibration target plate fabrication

[0008] according to Figure 2 As shown, a calibration target plate 5 is fabricated, and the centers (OA, OB) of the two laser tracker ball mounts 6 are aligned with the center O1 (x) of the light spot projection disk 7. O1 ,y O1 ,z O1 They are collinear and satisfy the following equation:

[0009]

[0010] 2) Determine the coordinate system of the end effector 1 of the automatic hole-making equipment.

[0011] Before calibration, a coordinate system for the end effector 1 of the automatic hole-making equipment is established using digital measuring equipment such as a tracker. This primarily determines the positional relationship between the auxiliary laser tracker ball mount 3 and the tool spindle of the end effector 1. The tool spindle is selected as the Z-axis, while the X and Y axes are unrestricted. Finally, a value is assigned to the center of the auxiliary laser tracker ball mount 3 (target ball diameter 12.7mm) for subsequent calibration to quickly establish the coordinate system of the end effector 1.

[0012] 3) Calibrate the optical normal sensor 2

[0013] Adjust the position of the end effector 1 of the automatic hole-making equipment, select an optical normal sensor 2, and make the sensor laser line 4 emitted by it approximately parallel to the horizontal plane, so that the light spot of the sensor laser line 4 within a range of 10m can fall on the calibration target plate 5.

[0014] Place the laser tracker target ball on the ball seat 3 of the measuring auxiliary laser tracker, and use the laser tracker to measure the target ball on the ball seat 3 of the auxiliary laser tracker point by point, and record the coordinate values. Use the coordinate values ​​determined in step 2) as the target values ​​to establish the coordinate system of the end effector 1 of the automatic hole making equipment using the best fit.

[0015] Place the calibration target plate 5 near the end effector 1 of the automatic hole-making equipment, at a distance of about 5m. Adjust the calibration target plate 5 so that the spot of the sensor laser line 4 falls on the center of the spot projection disk 7. Place the laser tracker target ball inside the laser tracker ball base 6, use the laser tracker to measure the values ​​of two points, record the coordinate values, and calculate the center value of the spot of the sensor laser line 4 as P1(x,y,z) according to the equation in step 1). Similarly, along the direction of the sensor laser line 4, move the calibration target plate 5 about 5m further away to obtain the center value of the spot of the sensor laser line 4 as P2(x,y,z). Since there are measurement and spot position adjustment errors in the calibration process (the comprehensive error does not exceed 0.5mm), by increasing the calibration distance, the influence of the comprehensive error can be significantly reduced when calculating the straight angle. Based on the closest 5m, the error does not exceed atan(0.5 / 5000) = 0.006°.

[0016] 4) Optical normal sensor 2 angle calculation

[0017] According to the equation of the straight line Substitute the coordinates of points P1 and P2 into the linear equation, and calculate the spatial expression of sensor laser line 4 with point P2 as the initial point. Then calculate the positional relationship between sensor laser line 4 and the spindle of the tool of the end effector 1 of the automatic hole-making equipment, and complete the calibration calculation of optical normal sensor 2.

[0018] 5) Repeat steps 3) and 4) to complete the calibration and angle calculation of the remaining optical normal sensors 2, and achieve high-precision calibration of all optical normal sensors 2.

[0019] The beneficial effects of this invention are as follows: Based on large-scale, high-precision measuring equipment such as laser trackers, this invention uses a specially designed calibration target plate to effectively control the overall error influence within one-thousandth when calibrating straight angles by increasing the calibration distance. This significantly improves the calibration accuracy of the optical normal sensor, with the angle calibration deviation not exceeding 0.006°, reduces the processing accuracy requirements of the end effector, and ensures the perpendicularity of the hole made by the automatic hole-making equipment. Attached Figure Description

[0020] Figure 1This is a diagram illustrating the configuration of an automatic drilling end-normal sensor calibration system for aircraft.

[0021] Figure 2 This is a schematic diagram of the calibration target plate structure.

[0022] In the figure: 1. End effector of automatic hole making equipment; 2. Optical normal sensor; 3. Ball mount of auxiliary laser tracker; 4. Sensor laser line; 5. Calibration target plate; 6. Ball mount of laser tracker; 7. Spot projection disk. Detailed Implementation

[0023] The following description, in conjunction with the embodiments and accompanying drawings, further explains the specific implementation of the present invention, but is not intended to limit the present invention.

[0024] like Figure 1 As shown, the calibration method for the aircraft automatic hole-making end-normal sensor calibration system includes the following steps:

[0025] 1) Calibration target plate fabrication

[0026] according to Figure 2 As shown, a calibration target plate 5 is fabricated. The centers (OA, OB) of the two laser tracker ball mounts 6 are aligned with the center O1 of the light spot projection disk 7, with O1 located at the midpoint between OA and OB.

[0027] 2) Determine the coordinate system of the end effector 1 of the automatic hole-making equipment.

[0028] Using digital measuring equipment such as a tracker, a coordinate system for the end effector 1 of the automatic hole-making equipment is established, with the tool spindle selected as the Z-axis and the X and Y axes unrestricted. The center of the ball seat 3 of the auxiliary laser tracker is assigned a value for subsequent calibration to quickly establish the coordinate system of the end effector 1 of the automatic hole-making equipment.

[0029] 3) Calibrate the optical normal sensor 2

[0030] Adjust the position of the end effector 1 of the automatic hole-making equipment, select an optical normal sensor 2, and make the sensor laser line 4 emitted by it approximately parallel to the horizontal plane, so that the light spot of the sensor laser line 4 within a range of 10m can fall on the calibration target plate 5.

[0031] Place the laser tracker target ball on the ball seat 3 of the measuring auxiliary laser tracker, and use the laser tracker to measure the target ball on the ball seat 3 point by point, record the coordinate values, and use the best fit to quickly establish the coordinate system of the end effector 1 of the automatic hole making equipment.

[0032] Along the direction of the sensor laser line 4, the calibration target plate 5 is placed at two locations 5m and 10m away from the end effector 1 of the automatic hole-making equipment, respectively. The calibration target plate 5 is adjusted so that the light spot of the sensor laser line 4 falls on the center of the light spot projection disk 7. The values ​​of two points on the ball seat 6 of the laser tracker are measured using a laser tracker, and the center values ​​of the light spot of the sensor laser line 4, P1(x,y,z) and P2(x,y,z), are calculated.

[0033] 4) Optical normal sensor 2 angle calculation

[0034] Substitute the coordinates of points P1 and P2 into the linear equation, and calculate the spatial expression of sensor laser line 4 with point P2 as the initial point; then calculate the positional relationship between sensor laser line 4 and the spindle of the tool of the end effector 1 of the automatic hole-making equipment, and complete the calibration calculation of optical normal sensor 2.

[0035] 5) Repeat steps 3) and 4) to complete the calibration and angle calculation of the remaining optical normal sensors 2, and achieve high-precision calibration of all optical normal sensors 2.

Claims

1. A method for calibrating an automatic hole-making end normal sensor, characterized in that, This method is based on an automatic drilling end-effector calibration system, which includes an automatic drilling equipment end effector (1), an optical normal sensor (2), an auxiliary laser tracker ball mount (3), a calibration target plate (5), a laser tracker ball mount (6), and a spot projection disk (7). The automatic drilling equipment end effector (1) is fixedly mounted on a robot or a five-axis CNC machine tool. Multiple optical normal sensors (2) are installed on the front cone of the automatic drilling equipment end effector (1), surrounding the brake tool spindle. The auxiliary laser tracker ball mounts (3) are distributed on the automatic drilling equipment end effector (1) for easy measurement. The optical normal sensor (2) emits a laser line (4) to quickly establish the coordinate system of the end effector during the calibration process. The light emitted by the optical normal sensor (2) is the sensor laser line (4), which is used to measure the distance between the optical normal sensor (2) and the surface of the aircraft skin. By combining the data from multiple sets of optical normal sensors (2), the angle between the spindle of the tool of the end effector (1) of the automatic drilling equipment and the aircraft skin can be calculated, thereby providing closed-loop control data support for normal adjustment. The calibration target plate (5) is placed on the ground and can be adjusted in height and angle. A laser tracker ball seat (6) and a spot projection disk (7) are arranged on it, with the spot projection disk (7) located at the center of the calibration target plate (5). The specific calibration method is as follows: 1) Calibration target plate fabrication Make a calibration target plate (5), and adjust the centers OA and OB of the two laser tracker ball mounts (6) to be collinear with the center O1 of the light spot projection disk (7), with O1 located at the midpoint of OA and OB; 2) Determine the coordinate system of the end effector of the automatic hole-making equipment. Before calibration, the coordinate system of the end effector (1) of the automatic hole-making equipment is established by digital measurement equipment, the tool spindle is selected as the Z axis, and the X and Y axes are not limited; and the center of the ball seat (3) of the auxiliary laser tracker is assigned a value for subsequent calibration to quickly establish the coordinate system of the end effector (1) of the automatic hole-making equipment. 3) Calibrate the optical normal sensor The specific steps are as follows: Adjust the position of the end effector (1) of the automatic hole-making equipment, select an optical normal sensor (2) so that the sensor laser line (4) emitted by it is parallel to the horizontal plane, and ensure that the light spot of the sensor laser line (4) within a range of 10m can fall on the calibration target plate (5). Place the laser tracker target ball on the ball seat (3) of the measuring auxiliary laser tracker, and use the laser tracker to measure the target ball on the ball seat (3) of the auxiliary laser tracker point by point, record the coordinate values, and use the coordinate values ​​determined in step 2) as the target values ​​to establish the coordinate system of the end effector (1) of the automatic hole making equipment using the best fit; Along the direction of the sensor laser line (4), place the calibration target plate (5) at two locations 5m and 10m away from the end effector (1) of the automatic hole-making equipment, respectively. Adjust the calibration target plate (5) so that the light spot of the sensor laser line (4) falls on the center of the light spot projection disk (7). Place the laser tracker target ball in the laser tracker ball seat (6), use the laser tracker to measure the values ​​of the two points, record the coordinate values, and calculate the center value of the light spot of the sensor laser line (4) as P1(x, y, z) and P2(x, y, z). 4) Calculation of the angle of the optical normal sensor Substitute the coordinates of points P1 and P2 into the linear equation, and calculate the spatial expression of the sensor laser line (4) with point P2 as the initial point; then calculate the positional relationship between the sensor laser line (4) and the tool spindle of the end effector (1) of the automatic hole-making equipment, and complete the calibration calculation of the optical normal sensor (2); 5) Repeat steps 3) and 4) to complete the calibration and angle calculation of the remaining optical normal sensors (2) and achieve high-precision calibration of all optical normal sensors (2).

2. The method for calibrating an automatic hole-making end normal sensor according to claim 1, characterized in that, In step 3), the target ball has a diameter of 12.7 mm.

3. A method for calibrating an automatic hole-making end normal sensor according to any one of claims 1 or 2, characterized in that, In step 3), the error should not exceed 0.006° based on the nearest 5m.

Images