CN113932753A - Method for calibrating grinding profile of hub flange plate - Google Patents

Abstract

The invention discloses a contour calibration method for wheel hub flange grinding, comprising step 1, setting and fixing a workpiece of the wheel hub flange to be polished in a working state; step 2, setting a contact probe on a mechanical arm of an industrial robot, Put the contact probe of the robotic arm against the inner side wall of the hub flange; step 3, define the first contact position of the contact probe as p1, and then pass the contact probe on the inner side wall of the hub flange at 45° intervals Carry out a position calibration, and record the position coordinate information of the contact position; Step 4, calculate the coordinates of the center O ₀ of the hub flange to be polished through the position coordinate information of the contact position; Step 5, repeat steps 3 and 4, carry out multiple Calibration, eliminate errors and determine the center position of the hub flange to be polished, so as to calibrate the contour of the hub flange to be polished. The invention can realize the calibration of the coordinate system for the contour of the hub flange, simplify the calibration process, and improve the production efficiency.

Description

A Contour Calibration Method for Wheel Hub Flange Grinding

technical field

The invention relates to a contour calibration method for wheel hub flange grinding in the field of industrial robot grinding.

Background technique

With the popularity of industrial robots and the rise in labor costs, the application of industrial robots in the grinding industry is possible. Compared with traditional manual grinding, the robotic grinding method has the advantages of good workpiece surface consistency, high production efficiency and low cost. More importantly, this method avoids the damage to employees' physical and mental health caused by metal dust and physical exertion during the manual grinding process, and also reduces the probability of safety accidents that may occur in manual operations.

Robot grinding programming can be done in two ways: manual teaching and offline programming. When used for complex space curve and curved surface processing, the accuracy of point position and the quality of distance control under manual teaching method are poor, and the efficiency of point position teaching is low and the randomness is large, so the processing effect of this method is not ideal. . The offline programming method of the robot can automatically program without affecting the work of the robot. It has functions such as accessibility analysis, collision interference check, and beat calculation, and the program is safer and more reasonable. Major robot manufacturers have launched off-line programming software, such as FANUC's ROBOGUIDE system and ABB's RobotStudio system. For example, the patent "System Calibration Method for Offline Programming of Grinding Robots" (201810764773.5) provides a system calibration method for offline programming of grinding robots, but requires the acquisition of physical scanning point cloud models and importing them into professional software for processing and reconstruction. to get calibration data. This sorting process increases the process of 3D scanning, which increases the cost and reduces the overall efficiency.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the deficiencies of the prior art, to provide a contour calibration method for hub flange grinding, aiming at the contour characteristics of the hub flange, using off-line programming and simulation functions to automatically generate off-line programs, and solve the workpiece The actual installation deviation problem can meet the reuse requirements of the grinding program.

A technical solution for achieving the above-mentioned purpose is: a method for calibrating the profile of hub flange grinding, comprising the following steps:

Step 1, set and fix the workpiece of the hub flange to be polished in the working state;

Step 2, set a contact probe on the robotic arm of the industrial robot, and abut the contact probe of the robotic arm against the inner side wall of the hub flange;

Step 3: Define the first contact position of the contact probe as p1, and then perform position calibration on the inner side wall of the hub flange every 45° by the contact probe, and define the subsequent contact positions P2, P3, P4, P5, P6, P7, P8, respectively record the position coordinate information of the contact position;

Step 4, calculate the coordinates of the center O ₀ of the hub flange to be polished by the position coordinate information of the contact position;

Step 5: Repeat steps 3 and 4 to perform multiple calibrations to obtain the coordinates of the center of the _circle O ₁ , O ₂ , O ₃ . , and then determine the center position of the flange of the hub to be polished by calibrating the area where the data points are located, so as to calibrate the contour of the flange of the hub to be polished.

Further, in step 3, the position coordinates of the P1 are (x ₁ , y ₁ , z ₁ ), the position coordinates of the P2 are (x ₂ , y ₂ , z ₂ ), and the position coordinates of the P1 are (x ₃ , y ₃ , z ₃ ), and so on.

Further, the position of the circle center O ₀ is defined by (X, Y, Z, W, P, R), where X, Y, and Z are used to indicate the position of the circle center O ₀ in the base coordinates of the industrial robot; W, P , R are used to represent the attitude of the workpiece coordinate system, where the W value represents the rotation angle of the workpiece coordinate system around the base coordinate X axis, P represents the rotation angle of the workpiece coordinate system around the base coordinate Y axis, and the R value represents the workpiece coordinate system around the base coordinate. The rotation angle of the coordinate Z axis;

The coordinates of the center of the circle 0 ₀ are:

in,

A ₁ =y ₁ z ₂ -y ₁ z ₃ -z ₁ y ₂ +z ₁ y ₃ +y ₂ z ₃ -y ₃ z ₂

B ₁ = -x ₁ z ₂ +x ₁ z ₃ +z ₁ x ₂ -z ₁ x ₃ -x ₂ z ₃ +x ₃ z ₂

C ₁ =x ₁ y ₂ -x ₁ y ₃ -y ₁ x ₂ +y ₁ x ₃ +x ₂ y ₃ -x ₃ y ₂

D ₁ = -x ₁ y ₂ z ₃ +x ₁ y ₃ z ₂ +x ₂ y ₁ z ₃ -x ₃ y ₁ z ₂ -x ₂ y ₃ z ₁ +x ₃ y ₂ z ₁

A ₂ =2(x ₂ -x ₁ )

B ₂ =2(y ₂ -y ₁ )

C ₂ =2(z ₂ -z ₁ )

D ₂ =x ₁ ² +y ₁ ² +z ₁ ² -x ₂ ² -y ₂ ² -z ₂ ²

A ₃ =2(x ₃ -x ₁ )

B ₃ =2(y ₃ -y ₁ )

C ₃ =2(z ₃ -z ₁ )

D ₃ =x ₁ ² +y ₁ ² +z ₁ ² -x ₃ ² -y ₃ ² -z ₃ ²

The rotation angle is:

R=atan2(u _y ,y _x )

P=atan2(-u _z cosR,u _x )

W=atan2(v _z ,w _z )

in,

The invention provides a contour calibration method for wheel hub flange grinding, which can realize the coordinate system calibration of the wheel hub flange contour without going through the process of 3D scanning, expands the application of offline programming of the grinding robot, and makes complex trajectories possible. The programming efficiency of the robot has been significantly improved, and the reuse requirements of the grinding program are met, so that the grinding quality of the robot grinding is stable and the production efficiency is improved.

Description of drawings

Fig. 1 is a kind of wheel hub flange workpiece structure schematic diagram to be polished of the profile calibration method of wheel hub flange polishing of the present invention;

FIG. 2 is a schematic view of the plane structure of the hub flange to be polished in a contour calibration method for hub flange polishing according to the present invention.

Detailed ways

In order to better understand the technical solutions of the present invention, the following specific examples are described in detail:

Under the ROBOGUIDE environment, according to the contour characteristics of the hub flange, the invention uses offline programming and simulation functions to automatically generate an offline program, solves the problem of actual installation deviation of the workpiece, and meets the reuse requirements of grinding programs.

The grinding object in this embodiment is a spherical wheel hub, which is a key component of the wind power equipment. Due to its large size and weight, grinding and cleaning after casting are difficult and risky. At present, the grinding and cleaning method of the wheel hub is mainly carried out by manual hand-held tool or grinding wheel, which has low processing efficiency and large differences in manual operation. The height of the wind turbine hub is 3000mm and the mass is about 20t. Three fan blades are evenly distributed in the circumferential direction to connect to the flange, and the outer diameter of the disk is about 2300mm. Due to the occurrence of flash, burr, parting line, etc. in the casting process of the blank part, it is required to use the grinding process for the initial processing and cleaning of the line edge of the casting, such as the edge of the blade butting flange. By adopting the present invention, manual hammering and grinding wheel grinding can be replaced in an automated manner.

The grinding system consists of a robot, a quick-change interface at the end, a grinding head and a probe head, a workpiece rotating table, etc. Among them, the robot adopts FANUC's R-2000iC/210L. The robot has a maximum range of 3100mm and a repeatability of 0.05mm. It is widely used in grinding, welding, handling, deburring and other work scenarios. A quick-change joint is installed at the end of the robot, which can automatically replace the grinding head and the contact probe according to the process needs. The contact probe is used for the position calibration of the hub workpiece. The workpiece rotary table adopts the worm gear transmission form, which can realize the rotation positioning of the table surface and reliable self-locking during processing. In order to facilitate the transplantation and reuse of offline programs, the origin of the workpiece coordinate system is generally set at the center of the circle o, but because the flange is hollow and large in size, the o point cannot be positioned directly and accurately.

Please refer to Figure 1 and Figure 2, set the plane where the flange is located as plane I, the base coordinate system of the industrial robot is B, and the center point o is the origin of the coordinate system of workpiece 1 to be polished, so point o is on plane I, w is the third coordinate axis of the workpiece 1 coordinate system of the flange to be polished, and the other u and v coordinate axes can be arbitrarily defined. There is no need to set the contact probe positioning pin on the flange plate, because the position of the circle is theoretically located in the coordinates of the center point o and the unit normal vector w of the plane I, and has nothing to do with the u and v vectors.

Before reusing the offline programming program on the field robot, the workpiece position needs to be detected and calibrated due to the workpiece clamping error. A contour calibration method for wheel hub flange grinding of the present invention includes the following steps:

Step 1. Set and fix the workpiece of the hub flange to be polished in the working state.

In step 2, a contact probe is set on the mechanical arm of the industrial robot. In order to improve the detection accuracy, a contact probe with high precision and high hardness is used. Touch the contact probe of the robot arm against the inner side wall of the hub flange.

Step 3: Define the first contact position of the contact probe as p1, and then perform position calibration on the inner wall of the hub flange at intervals of 45° by the contact probe, and define the subsequent contact positions P2, P3, P4, P5, P6, P7, and P8 respectively record the position coordinate information of the contact position. In Figure 2, P1, P2, P3, P4, P5, P6, P7, and P8 are the calibration points of the probe sequence, and the point P1 is set on the u-axis of the coordinate system of the workpiece 1 of the flange to be polished. The position coordinates of P1 are (x ₁ , y ₁ , z ₁ ), the position coordinates of P2 are (x ₂ , y ₂ , z ₂ ), and the position coordinates of P1 are (x ₃ , y ₃ , z ₃ ), so that analogy.

Step 4: Calculate the coordinate O ₀ of the center of the flange of the hub to be polished by using the position coordinate information of the contact position. The workpiece coordinate system calibration of the FANUC robot is defined by 6 values, namely X, Y, Z, W, P, R. Among them, X, Y, and Z are used to represent the position of the origin in the base coordinate B of the robot; W, P, and R are used to represent the attitude of the workpiece coordinate system, where the value of W represents the rotation angle of the workpiece coordinate system around the X axis, and P It represents the rotation angle of the workpiece coordinate system around the Y axis, and the R value represents the rotation angle of the workpiece coordinate system around the Z axis.

The coordinates of the center of the circle 0 ₀ are:

in,

A ₁ =y ₁ z ₂ -y ₁ z ₃ -z ₁ y ₂ +z ₁ y ₃ +y ₂ z ₃ -y ₃ z ₂

B ₁ = -x ₁ z ₂ +x ₁ z ₃ +z ₁ x ₂ -z ₁ x ₃ -x ₂ z ₃ +x ₃ z ₂

C ₁ =x ₁ y ₂ -x ₁ y ₃ -y ₁ x ₂ +y ₁ x ₃ +x ₂ y ₃ -x ₃ y ₂

D ₁ = -x ₁ y ₂ z ₃ +x ₁ y ₃ z ₂ +x ₂ y ₁ z ₃ -x ₃ y ₁ z ₂ -x ₂ y ₃ z ₁ +x ₃ y ₂ z ₁

A ₂ =2(x ₂ -x ₁ )

B ₂ =2(y ₂ -y ₁ )

C ₂ =2(z ₂ -z ₁ )

D ₂ =x ₁ ² +y ₁ ² +z ₁ ² -x ₂ ² -y ₂ ² -z ₂ ²

A ₃ =2(x ₃ -x ₁ )

B ₃ =2(y ₃ -y ₁ )

C ₃ =2(z ₃ -z ₁ )

D ₃ =x ₁ ² +y ₁ ² +z ₁ ² -x ₃ ² -y ₃ ² -z ₃ ²

The rotation angle is:

R=atan2(u _y ,y _x )

P=atan2(-u _z cosR,u _x )

W=atan2(v _z ,w _z )

in,

To sum up, (X, Y, Z, W, P, R) are the direct input values when the user coordinate system is calibrated under these three points. Where (x ₀ , y ₀ , z ₀ ) is the origin of the workpiece coordinate system.

Step 5: Repeat steps 3 and 4 to perform multiple calibrations to avoid excessive human error during calibration operations. Obtain the circle center coordinates O ₁ , O ₂ , O ₃ ... On , if the distance between any two points _is greater than the set value, discard the set of calibration data points, and then determine the hub method to be polished according to the area where the calibration data points are located The center position of the flange, so as to demarcate the contour of the flange of the hub to be polished. The calibration algorithm can be implemented in the form of Karel language, embedded in the robot controller, and invoked in the form of program execution.

Embodiment 1: In ROBOGUIDE, the method is used to locate the outer edge area of the workpiece to be processed multiple times, and the workpiece coordinate system calibration algorithm is used to obtain the calibration input value. The target feature of the workpiece is automatically identified by the Closed Loop method in the CAD-TO-PATH function, the contour curve of the outer edge is extracted, and the offline grinding program of the flange surface edge is automatically generated.

In this offline automatic programming function, the origin of the user coordinate system is set at the center of the flange, the z-axis is perpendicular to the plane of the flange and points outward, the radius of the machining tool is set to 20mm, and the tool is deflected by 10° toward the center of the track. The programmed entry and exit points are set to P1, and the safety distance is set to 100mm. When the robot performs deburring operations, it first moves the tool to the safety point quickly, then moves to the entry point in a straight line, and then follows the The machining path point is ground and processed. After the machining of the path is completed, that is, after moving to the end point of the path, lift the tool in a straight line to a safe point.

Embodiment 2: When the workpiece has a certain offset, including the position and attitude, the workpiece coordinate system calibration algorithm is also used to obtain the calibration input value and update the same workpiece coordinate system. Run the program FPRG1 again to recalculate the trajectory path of the grinding head.

In the summary of the two examples, the position of the machining track on the edge of the hub flange is accurate, indicating that the above-mentioned user coordinate system calibration method is accurate; comparing Example 1 and Example 2, the tool attitude of the two is consistent with the machining track, indicating that the automatic The generated offline program can be reused in the field robot; therefore, the offline program automatically generated by ROBOGUIDE can be used for the machining operation of the wheel hub flange in the workshop without the need to pre-set precise positioning points on the workpiece, which is also suitable for machining. The division of process tasks provides the conditions.

Those of ordinary skill in the art should realize that the above embodiments are only used to illustrate the present invention, but not to limit the present invention. Changes and modifications will fall within the scope of the claims of the present invention.

Claims (3)

1. A method for calibrating grinding profile of a hub flange plate is characterized by comprising the following steps:

step 1, arranging and fixing a hub flange plate workpiece to be polished in a working state;

step 2, arranging a contact probe on a mechanical arm of the industrial robot, and enabling the contact probe of the mechanical arm to abut against the inner side wall of the hub flange plate;

step 3, defining a first contact position of the contact probe as P1, then carrying out position calibration once through the contact probe at an interval of 45 degrees on the inner side wall of the hub flange, respectively defining subsequent contact positions P2, P3, P4, P5, P6, P7 and P8, and respectively recording position coordinate information of the contact positions;

step 4, calculating the circle center O of the flange plate of the hub to be polished through the position coordinate information of the contact position₀Coordinates;

step 5, repeating the step 3 and the step 4, calibrating for multiple times, and obtaining a circle center coordinate O₁、O₂、O₃…O_nAnd if the distance between any two points is larger than a set value, abandoning the calibration data point set, and determining the circle center position of the to-be-polished hub flange plate according to the area range where the calibration data points are located, so as to calibrate the profile of the to-be-polished hub flange plate.

2. The method for calibrating the grinding profile of the hub flange plate according to claim 1, wherein in the step 3, the position coordinate of P1 is (x) in₁,y₁,z₁) The position coordinate of P2 is (x)₂，y₂，z₂) The position coordinate of P1 is (x)₃,y₃,z₃) And so on.

3. The method for calibrating the grinding profile of the hub flange plate according to claim 2, wherein the center of the circle is O₀Is defined by (X, Y, Z, W, P, R), wherein X, Y, Z is used to indicate the center O₀Position in a base coordinate of an industrial robot; w, P, R is used for representing the attitude of the workpiece coordinate system, wherein W represents the angle of rotation of the workpiece coordinate system about the X axis of the base coordinate system, P represents the angle of rotation of the workpiece coordinate system about the Y axis of the base coordinate system, and R represents the angle of rotation of the workpiece coordinate system about the Z axis of the base coordinate system;

circle center 0₀The coordinates of (a) are:

wherein,

A₁＝y₁z₂-y₁z₃-z₁y₂+z₁y₃+y₂z₃-y₃z₂

B₁＝-x₁z₂+x₁z₃+z₁x₂-z₁x₃-x₂z₃+x₃z₂

C₁＝x₁y₂-x₁y₃-y₁x₂+y₁x₃+x₂y₃-x₃y₂

D₁＝-x₁y₂z₃+x₁y₃z₂+x₂y₁z₃-x₃y₁z₂-x₂y₃z₁+x₃y₂z₁

A₂＝2(x₂-x₁)

B₂＝2(y₂-y₁)

C₂＝2(z₂-z₁)

D₂＝x₁ ²+y₁ ²+z₁ ²-x₂ ²-y₂ ²-z₂ ²

A₃＝2(x₃-x₁)

B₃＝2(y₃-y₁)

C₃＝2(z₃-z₁)

D₃＝x₁ ²+y₁ ²+z₁ ²-x₃ ²-y₃ ²-z₃ ²

the rotating angle is as follows:

R＝atan2(u_y,y_x)

P＝atan2(-u_zcosR,u_x)

W＝atan2(v_z,w_z)

wherein,

v＝w×u。

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