A detection method and device for automatic angle finding of annular micro blind hole

Abstract

The present invention relates to the field of automatic measurement of the hole positions of industrial annular parts, and provides a convenient automatic circumferential hole finding and automatic hole center alignment detection method and device, which are used for the automated assembly of a certain large precision part in aerospace. During measurement, the annular part is first automatically aligned, and the XYZ axis of the four-coordinate truss robot is moved to align the rotation center of the measuring end with the center of the annular part. The sensor is then moved to the radial position of the hole position to be measured by the radial cylinder. The Z axis is slowly moved downward to the measuring plane. When the value of the optical fiber sensor is higher than the threshold value 1, the predetermined detection height is reached, and the movement of the Z axis is stopped. The rotating R axis drives the digital optical fiber sensor to rotate one circle. Through the change in the value of the optical fiber sensor, the circumferential scanning hole finding and hole center positioning of the small blind hole of the annular part are realized with the value below the threshold value 2 as the standard. The present invention adopts a non-contact measurement method to avoid scratches and bumps on precision parts to the greatest extent.

Description

Technical Field

[0001] The present invention relates to the field of automatic measurement of the hole positions of industrial annular parts, and specifically to a detection method and device for automatic angle orientation of annular micro-blind holes. The method and device are applicable to technologies such as automatic angle orientation and hole center positioning of annular micro-blind holes and through holes, and can be used for the automated assembly of large and medium-sized equipment. Background Art

[0002] The automated assembly of a large precision aerospace component requires multiple circumferential hole position identification and hole center positioning detection requirements, and high positioning and assembly accuracy are required. Assembly of through holes or shallow surfaces can be achieved manually, but blind hole detection of narrow ring deep bottom hole workpieces is a major difficulty in the assembly process. The assembly parts diagram is shown in the figure below. Figure 1-Figure 3 shown.

[0003] The current assembly method is manual assembly, which requires three skilled professional operators and takes 90 minutes. The specific process steps are described in Table 1:

[0004] Table 1 Manual assembly method for narrow ring deep bottom blind hole detection

[0005]

[0006] The difficulties of manual assembly are:

[0007] The assembly holes are located at the annular edge of the bottom of the workpiece, which limits the assembly freedom.

[0008] The hole is blind and cannot be passed through by the assembly parts for trial and verification;

[0009] High assembly accuracy requirements for holes and fittings. Summary of the Invention

[0010] To address the difficulties and shortcomings of manual assembly of precision-fitted parts, this invention provides a convenient, automated circumferential hole-finding and hole-center alignment detection method and device. Utilizing a four-axis truss robot and fiber optic sensors, this method achieves precise angular positioning and non-contact measurement, enabling accurate measurement and effective protection of hole positions in precision-fitted parts.

[0011] The technical solution adopted by the present invention to achieve the above-mentioned purpose is:

[0012] A detection device for automatic angle orientation of annular micro blind holes, comprising: a four-coordinate truss robot, an optical fiber sensor, a radial cylinder, and a PLC control system, wherein:

[0013] The radial cylinder is arranged on the end of the R-axis, one end is fixed at the center of the circle of the end of the R-axis, and the other end is provided with a fiber optic sensor. The plane where the radial cylinder is located is perpendicular to the Z-axis of the four-coordinate truss robot. The PLC control system is connected to the radial cylinder and the fiber optic sensor respectively.

[0014] The X, Y, and Z axes of the truss robot are all ball screw structures, and the R axis rotates around the center of the Z axis.

[0015] The PLC control system is also connected to the industrial computer and the display respectively.

[0016] A method for automatically finding the angle of an annular micro blind hole comprises the following steps:

[0017] 1) Place the assembly 1 on the operating table of the four-coordinate truss robot and use a level ruler to check that the positions of the assembly 1 and the operating table of the four-coordinate truss robot are both level;

[0018] 2) Detect the center coordinates of assembly 1 using visual inspection, calculate the offset between the center coordinates of the assembly 1 and the center coordinates of the R-axis end of the four-axis truss robot, and control the movement of the X-axis and Y-axis to align the center of assembly 1 and the center of the R-axis end on the same vertical line;

[0019] 3) Using a radial cylinder, move the fiber optic sensor to the radial position of the hole to be measured on assembly 1, so that the projection length of the line connecting the fiber optic sensor and the center of the circle at the end of the R axis on the plane where the hole to be measured is the length from the hole to the center of assembly 1, and control the Z axis to move to the predetermined measurement height;

[0020] 4) Rotate the R-axis to drive the optical fiber sensor to rotate one circle, record the starting time t1 and the ending time t2 when the value of the optical fiber sensor is lower than the threshold 2, and convert the angles using the values of the encoder on the R-axis corresponding to the times t1 and t2, respectively, to obtain the circumferential angles α1 and α2 on both sides of the hole to be measured, and then obtain the hole center angle α = (α1 + α2) / 2 of the hole to be measured, completing the angle direction finding.

[0021] After completing the angle finding, the four-axis truss robot returns to the initial position, replaces the assembly gripper, and picks up the assembly part 2 at a fixed angle according to the hole center angle α. After picking up, the truss robot is moved again to complete the automated assembly work.

[0022] The assembly part 1 is an annular workpiece.

[0023] In step 2), the initial position of the optical fiber sensor on the R axis deviates from the hole position to be measured on the assembly 1 by at least a set angle.

[0024] In step 3), when the value of the optical fiber sensor at the end of the R-axis of the four-coordinate truss robot is higher than the threshold value 1, the Z-axis reaches the predetermined measurement height. If the value of the optical fiber sensor is always lower than the threshold value 1, then check whether the optical fiber sensor is normal, whether the position of the assembly 1 is horizontal, and whether the position of the four-coordinate truss robot operating table is horizontal.

[0025] In step 4), if the value of the optical fiber sensor is still not lower than threshold 2 after the R axis rotates for more than one circle, check whether the radial position of the optical fiber sensor is consistent with the radial position of the hole to be measured and whether there is any foreign matter at the hole to be measured.

[0026] The present invention has the following beneficial effects and advantages:

[0027] 1. The present invention adopts a non-contact measurement method to avoid scratches and bumps on precision parts to the greatest extent.

[0028] 2. Angle measurement and assembly are implemented step by step to facilitate precise angle orientation and hole center positioning of tiny blind holes.

[0029] 3. The present invention utilizes a four-coordinate truss robot for automated measurement and assembly, saving labor and improving efficiency.

[0030] 4. This method can be used to detect and locate similar circumferential hole-finding requirements.

[0031] 5. Data is collected in real time, and through data analysis, a preliminary judgment can be made on the flatness of the workpiece to be tested. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of assembly part 1;

[0033] Figure 2 This is a schematic diagram of assembly part 2;

[0034] Figure 3 A schematic diagram of the assembly components;

[0035] Figure 4 Schematic diagram of a four-coordinate truss robot;

[0036] Figure 5 This is a schematic diagram of the principle of automatic angle direction finding;

[0037] Figure 6 These are the implementation steps of an example of the present invention;

[0038] Figure 7 This is the sensor value change diagram when the Z axis is moved to the detection plane;

[0039] Figure 8 This is a diagram of the sensor value changes during automatic angle finding. DETAILED DESCRIPTION

[0040] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0041] The system of the present invention includes the following components:

[0042] 1) Four-axis truss robot (XYZ axis is a ball screw structure, R axis can rotate around the center of Z axis)

[0043] 2) XYZ axis servo motor and absolute encoder

[0044] 3) R-axis servo motor, encoder and reducer

[0045] 4) Fiber optic sensors

[0046] 5) Radial cylinder

[0047] 6)PLC control system

[0048] 7) Industrial computers and displays

[0049] like Figure 4 As shown, the 4-axis truss robot utilizes servo motors and absolute encoders for the X, Y, and Z axes, while the rotary R-axis utilizes a servo motor, reducer, and absolute encoder. The motor, reducer, and encoder are integrated into the 4-axis truss robot itself, with the robot's operating console located beneath the truss. A fiber optic sensor and radial cylinder are integrated into the removable R-axis end cap. The R-axis end cap is also equipped with an internal pneumatically supported assembly gripper for assembly after angular orientation. The PLC control system, industrial computer, and monitor are located near the console.

[0050] Figure 5 This is a schematic diagram of the principle of automatic angle direction finding. The XY axis aligns the detection center O' with the center to be detected O, and then moves the radial cylinder, vertical axis Z axis, and rotation axis R axis respectively to achieve circumferential scanning and hole finding of the detection plane. The details are as follows:

[0051] like Figure 6 As shown, first, place the assembly 1 on the operating table of the four-coordinate robot and use a spirit level to check to ensure it is level. The detection of the workpiece center is achieved by visual inspection. By reading the workpiece center coordinate O position, the actual offset is calculated, and the XY axis is moved according to the offset so that the center of the R axis end is aligned with the center of the annular workpiece to achieve automatic centering. Check whether the angle position of the optical fiber sensor on the R axis is the angle of the blind hole. If the angle is close, rotate the R axis to deviate by at least a certain angle (for example, 30 degrees).

[0052] In the second step, the optical fiber sensor is moved to the radius position of the hole to be measured by the radial cylinder, and the Z axis is slowly moved downward to the measurement plane. When the optical fiber sensor value is higher than the threshold value 1, Figure 7 As shown, the predetermined detection height has been reached, at which point the Z-axis movement ceases. If the sensor reading remains below threshold 1 when moving to the measurement plane, check that the fiber optic sensor is functioning properly, the work surface is level, and assembly 1 is level. The fiber optic sensor displays distance information as a quantized value of light intensity, which can be used to detect the presence of targets within the measuring range and their approximate distance.

[0053] The third step is to rotate the R axis to drive the digital fiber optic sensor to rotate one circle. The sensor value changes in real time during the rotation process. When encountering a hole or blind hole below the measurement plane, the value will suddenly decrease, such as Figure 8 As shown. Detection is performed based on the value falling below threshold 2. Record the start and end times t1 and t2 of reaching threshold 2. Using the R-axis encoder values at t1 and t2, calculate the circumferential angles α1 and α2 on either side of the blind hole. Hole center angle α = (α1 + α2) / 2. If the value remains below threshold 2 after more than one rotation, check that the radial position of the fiber optic sensor is consistent with that of the assembly hole and that there are no foreign objects in the assembly hole.

[0054] The R-axis end rotates around the Z-axis, and a zero position is marked on the surface of the fixed position where the Z-axis and the R-axis end are connected. When the R-axis rotates, the circumferential angle is converted by the change of the R-axis absolute encoder. The circumferential angle range is 0 to 360 degrees.

[0055] When performing angle direction finding, the optical fiber sensor value will change significantly at the edge of the hole to be measured. The circumferential angles α1 and α2 of the hole to be measured are recorded when the optical fiber sensor enters and leaves the hole to be measured.

[0056] When the optical fiber sensor is directly above the center of the hole to be measured, it is recorded as the hole center angle.

[0057] In the fourth step, after successfully completing the angle finding, the truss robot returns to the zero point, replaces the assembly gripper, and picks up the assembly part 2 at a fixed angle according to the hole center angle α. After picking up, the truss robot is moved again to carry out subsequent automated assembly work.

Claims

1. A method for automatically finding the angle of an annular micro blind hole, characterized in that: The detection method is implemented by a detection device for automatic angle finding of annular micro blind holes, which includes: a four-coordinate truss robot, an optical fiber sensor, a radial cylinder, and a PLC control system, wherein: The radial cylinder is arranged on the end of the R-axis, with one end fixed to the center of the circle at the end of the R-axis and the other end provided with an optical fiber sensor. The plane where the radial cylinder is located is perpendicular to the Z-axis of the four-axis truss robot. The PLC control system is connected to the radial cylinder and the optical fiber sensor respectively. The detection method comprises the following steps: 1) Place the assembly 1 on the operating table of the four-axis truss robot and use a level ruler to check that the positions of the assembly 1 and the operating table of the four-axis truss robot are both level; 2) Use visual inspection to detect the center coordinates of assembly 1 and calculate the offset between them and the center coordinates of the R-axis end of the 4-axis truss robot. Control the movement of the X-axis and Y-axis to align the center of assembly 1 and the center of the R-axis end on the same vertical line. 3) Use the radial cylinder to move the fiber optic sensor to the radial position of the hole to be measured on assembly 1, so that the projection length of the line connecting the fiber optic sensor and the center of the circle at the end of the R axis on the plane where the hole to be measured is the length from the hole to the center of assembly 1. Control the Z axis to move to the predetermined measurement height; 4) Rotate the R axis to drive the fiber optic sensor to rotate one circle, record the starting time t1 and the ending time t2 when the value of the fiber optic sensor is lower than the threshold 2, and convert the angles using the values of the R axis encoder corresponding to the times t1 and t2, respectively, to obtain the circumferential angles α1 and α2 on both sides of the hole to be measured, and then obtain the hole center angle α = (α1 + α2) / 2 of the hole to be measured, completing the angle direction finding; In step 3), when the value of the optical fiber sensor at the end of the R axis of the four-axis truss robot is higher than the threshold value 1, the Z axis reaches the predetermined measurement height. If the value of the optical fiber sensor is still lower than the threshold value 1, the optical fiber sensor is checked to see if it is normal, the position of the assembly 1 is checked to see if it is level, and the position of the operating table of the four-axis truss robot is checked to see if it is level. In step 4), if the value of the optical fiber sensor is still not lower than threshold 2 after the R axis rotates for more than one circle, check whether the radial position of the optical fiber sensor is consistent with the radial position of the hole to be measured and whether there is any foreign matter at the hole to be measured.

2. The method for detecting an annular micro blind hole by automatic angle orientation according to claim 1, characterized in that: After completing the angle finding, the four-axis truss robot returns to the initial position, replaces the assembly gripper, and picks up the assembly part 2 at a fixed angle according to the hole center angle α. After picking up, the truss robot is moved again to complete the automated assembly work.

3. The method for detecting an annular micro blind hole by automatic angle orientation according to claim 1, characterized in that: The assembly part 1 is an annular workpiece.

4. The method for detecting an annular micro blind hole by automatic angle orientation according to claim 1, characterized in that: In step 2), the initial position of the optical fiber sensor on the R axis deviates from the hole position to be measured on the assembly 1 by at least a set angle.

5. The method for detecting an annular micro blind hole by automatic angle orientation according to claim 1, characterized in that: The PLC control system is also connected to the industrial computer and the display respectively.

Images