CN107462881A - A kind of laser range sensor scaling method - Google Patents

Abstract

The invention discloses a laser ranging sensor calibration method, which belongs to the field of robot calibration. The device used in this method includes a laser tracker, an industrial mechanical arm, a flange, a hole-making end effector, a calibration rod, a plane calibration plate and a mounting frame, wherein the hole-making end effector mainly includes a feed module, an electric spindle, an electric Spindle mounting seat, large target ball seat, small target ball seat, pressing head and four laser distance measuring sensors, etc. In this method, the angle between the laser beam and the feed direction of the electric spindle is firstly calibrated; then the tool coordinate system and the workpiece coordinate system are established with the help of the laser tracker, and the hole-making end effector is moved to the front of the plane calibration plate and rotated several times, according to The geometric relationship calculates the coordinates of each laser point in different state coordinate systems, and then transforms the coordinates of all points into the same coordinate system to fit the spatial equation of the laser beam. The invention can calibrate the emitting point position and the laser beam sagittal direction of the laser ranging sensor, and can make the normal line detection result more accurate.

Description

A Calibration Method for Laser Distance Measuring Sensor

technical field

The invention relates to the field of robot calibration, in particular to a calibration method for a laser range-finding sensor, which can calibrate the positions of emission points and the sagittal directions of laser beams of four installed laser range-finding sensors.

Background technique

With the continuous improvement of people's material and cultural living standards, the way of travel is gradually changing, and more and more people choose to travel by air, so the demand for aircraft is increasing day by day. Automatic hole making is the most critical link in the manufacture and assembly of large aircraft, and occupies a very important position in aircraft manufacturing. The main connection method used in aircraft structures is mechanical connection. The most common connection method is riveting. The first step in riveting is drilling. The size of the hole and the quality of the hole wall seriously affect the strength of the riveting seam. Studies have shown that when the bolt is inclined more than 2° along the direction of the external load, the fatigue life is reduced by about 47%; when the inclination is greater than 5°, the fatigue life is reduced by about 95%. Therefore, an urgent problem to be solved in automatic hole making is how to ensure the verticality of the holes.

To ensure the verticality of the hole, the normal line of the surface of the workpiece must be detected first, and then the attitude adjustment is performed. For the normal line detection method, at present, the sensor is installed on the hole making end effector for real-time detection, and the most widely used sensor is the laser ranging sensor. However, due to processing and installation errors, it is necessary to calibrate the installation position of the sensor to ensure the accuracy of the normal measurement of the sensor. Based on the processed hole-making end effector, the present invention proposes a laser distance measuring sensor calibration method, which can calibrate the emitting point positions and laser beam sagittal directions of four installed laser distance measuring sensors.

Contents of the invention

The present invention proposes a calibration method for laser ranging sensors, the purpose of which is to calibrate the emission point positions and laser beam sagittal directions of the four laser ranging sensors, and then more accurately determine the Find the normal vector of the hole-making point on the surface of the workpiece.

The present invention is realized through the following technical solutions.

The device used in the method of the present invention includes a laser tracker, an industrial mechanical arm, a flange, a hole-making end effector, a calibration rod, a plane calibration plate and a mounting frame, wherein the hole-making end effector mainly includes a feed module, an electric spindle , Electric spindle mounting seat, large target ball seat, small target ball seat, compression head and four laser distance measuring sensors, etc. The flange is used to connect the industrial robot arm and the hole making end effector. The calibration rod adopts the stepped shaft method, one end can be connected to the electric spindle, and the other end can be vertically connected to the plane calibration plate. There is a hole in the center of the plane calibration plate for installing the calibration rod, and the four corners respectively have a target ball seat hole for placing the target ball of the laser tracker and installation and fixing holes for fixing it on the mounting bracket. The electric spindle mounting seat connects the feed module and the electric spindle, the feed module can drive the electric spindle to move in a straight line, and there is a fixed large target ball seat on the electric spindle mounting seat. The four laser distance measuring sensors are installed obliquely on the pressing head. The moving industrial mechanical arm moves the hole-making end effector to the front of the plane calibration plate. The four laser beams shoot at the plane calibration plate at a certain angle. The laser points Marked on the surface of the flat calibration plate, the four laser distance measuring sensors each have a distance return value. Since the laser ranging sensor needs to receive the returned laser beam information through laser ranging, the surface of the plane calibration plate must have strong reflection ability and cannot be black material, so the material of the plane calibration plate is aluminum alloy. The coordinate system inside the laser tracker is the world coordinate system.

Through the above connections, a hardware platform for laser ranging sensor calibration is formed.

The method for laser ranging sensor calibration includes the following sequential steps:

Step 1: Install one end of the calibration rod on the electric spindle, install the flat calibration plate on the extension end of the calibration rod, install the small target ball seat on the end face of the extension end, and place the target ball connected to the laser tracker fixed on the target tee;

Step 2: The feed module drives the motorized spindle to move to a suitable position, uses the laser tracker to measure the coordinates of the target ball in the world coordinate system, rotates the plane calibration board several times, and records four different angles of the plane calibration board. The reading of the laser ranging sensor, move the electric spindle several times, and repeat this step;

Step 3: According to the position coordinates of the target ball obtained in step 2 and the readings of the laser ranging sensor, calculate the angle between the sagittal direction of each laser beam and the moving direction of the electric spindle;

Step 4: Remove the plane calibration plate, move the position of the electric spindle, and install a large target ball seat on the extended end of the calibration rod to ensure that the bottom surface of the target ball seat is closely attached to the pressing plane of the compression head;

Step 5: Carry out TCP calibration with the help of laser tracker, establish the tool coordinate system, and then remove the calibration rod, target ball and target ball seat installed on the electric spindle;

Step 6: Fix the plane calibration plate on the mounting frame, measure the coordinates of the four target ball seat mounting holes on the plane calibration plate with the help of the laser tracker, and fit the workpiece plane;

Step 7: Move the hole-making end effector to a certain distance in front of the plane calibration plate through the industrial robot arm, place the large target ball on the large target ball seat fixed on the electric spindle mounting seat, move the electric spindle several times, and place it in the world coordinates The coordinates of the target ball at each position are measured under the system, and a straight line is fitted according to the coordinates of the measured points, which is the feed direction of the electric spindle, and the angle between the feed direction of the electric spindle and the workpiece plane is calculated, and the industrial mechanical arm drives The hole-making end effector rotates around the X-axis and Y-axis of the tool coordinate system by corresponding angles around the TCP point as the center, and repeats this step until the feeding direction of the electric spindle is perpendicular to the workpiece plane;

Step 8: Establish a workpiece coordinate system parallel to the tool coordinate system;

Step 9: Record the current position as state 1, use the laser tracker to measure the coordinates of the target ball in the world coordinate system when the electric spindle feed is 0, and record the data of the four laser ranging sensors;

Step 10: The industrial mechanical arm drives the hole-making end effector to rotate a certain angle around the X-axis of the tool coordinate system with the TCP point as the center, record the data of four laser ranging sensors, and move the electric spindle multiple times. According to the method in step 7, Fit the feed direction of the electric spindle, and then calculate the angle between the feed direction of the electric spindle and the Z axis of the workpiece coordinate system;

Step 11: According to step 10, adjust the rotation angle of the hole-making end effector around the X-axis of the tool coordinate system several times, record the data of four laser ranging sensors, and calculate the feed direction of the electric spindle and the Z-axis of the workpiece coordinate system the included angle;

Step 12: The industrial mechanical arm drives the hole-making end effector to return to state 1, and then drives it to rotate a certain angle around the Y-axis of the tool coordinate system with the TCP point as the center, records the data of the four laser ranging sensors, and follows step 10 Calculate the angle between the feed direction of the electric spindle and the Z axis of the workpiece coordinate system by using the method;

Step 13: According to step 12, adjust the rotation angle of the hole-making end effector around the Y-axis of the tool coordinate system several times, record the data of four laser ranging sensors, and calculate the feed direction of the electric spindle and the Z-axis of the workpiece coordinate system the included angle;

Step 14: Calculate the relative positional relationship between the four laser points in state 1 based on the data obtained in steps 9-13 and the geometric relationship, and establish a state parallel to the tool coordinate system with the laser point of one of the laser ranging sensors as the origin Coordinate system 1, to obtain the coordinates of each laser point;

Step 15: Adjust the distance between the hole-making end effector and the plane calibration plate several times, according to step 9, record it as state j (j=2,3,4,...,q), repeat steps 9-14, Obtain the coordinates of each laser point under the coordinate system j;

Step 16: According to the relative position relationship between each state, calculate the conversion relationship between each coordinate system in each state, convert the coordinates of all points to the same coordinate system, and obtain q according to each laser ranging sensor Each laser point can fit a ray, that is, the emission point position and the laser beam sagittal direction of the four laser ranging sensors are calibrated.

The present invention has following technical effect:

1) The present invention can accurately measure the position of each point by means of the laser tracker, accurately obtain the tool coordinate system and the workpiece coordinate system, and obtain the angle between the line and the surface conveniently and accurately;

2) The calibration process of the present invention adopts the method of multiple measurements to make the calibration results more accurate;

3) The emission point position and the laser beam sagittal direction of the laser ranging sensor calibrated by the present invention are applied to the normal line detection of the hole making process, and the normal vector of the hole making point on the workpiece surface can be accurately found;

The calibration method proposed by the present invention is not limited to the detection of the normal direction of the hole, and can be applied to other situations where the position and sagittal direction of the beam emission point need to be calibrated, and the number of beams is 2 or more.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings that need to be used in the specific implementation or description of the prior art. Obviously, the accompanying drawings in the following description These are some implementations of the present invention. For those skilled in the art, other drawings can also be obtained according to these drawings without creative work.

Fig. 1 shows a schematic diagram of the included angle between the sagittal direction of the calibration laser beam and the moving direction of the main shaft in an embodiment of the present invention;

Fig. 2 shows the schematic diagram of calibration laser beam emitting point position and sagittal installation in the embodiment of the present invention;

Fig. 3 shows the schematic diagram of laser beam emission in the calibration process in the embodiment of the present invention;

Fig. 4 shows the schematic diagram of the projection of the laser beam to the tool coordinate system X _T O _T Z _T plane in the calibration process in the embodiment of the present invention;

Fig. 5 is a schematic diagram showing the geometric relationship of the laser beam projection in the calibration process in the embodiment of the present invention.

In the figure, 1 is the industrial mechanical arm, 2 is the flange, 3 is the feed module, 4 is the electric spindle, 5 is the electric spindle mounting seat, 6 is the large target ball seat, 7a~d are A~D laser distance measuring Sensor, 8 is the pressing head, 9 is the plane calibration plate, 9a is the installation hole of the calibration plate, 9b~e are the ball seat holes of A~D targets, 9f~i are the fixing holes for installation, 10 is the mounting frame, 11 is the calibration rod , 12 is the small target ball seat; {W} is the world coordinate system, {T} is the tool coordinate system, {B} is the workpiece coordinate system, and {S ₁ } is the state coordinate system 1.

detailed description

The technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Apparently, the described embodiments are part of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts fall within the protection scope of the present invention.

Referring to Fig. 1 and shown in Fig. 2, the device used in the method of the present invention comprises a laser tracker, an industrial mechanical arm 1, a flange 2, a hole making end effector, a calibration rod 11, a plane calibration plate 9 and a mounting frame 10, The hole-making end effector mainly includes the feed module 3, the electric spindle 4, the electric spindle mounting seat 5, the large target ball seat 6, the small target ball seat 12, the pressing head 8 and four laser distance measuring sensors 7a-d, etc. . The flange 2 is used to connect the industrial mechanical arm 1 and the hole making end effector. The calibration rod 11 is in the form of a stepped shaft, one end can be connected to the electric spindle 4 , and the other end can be vertically connected to the plane calibration plate 9 . There is a hole 9a for installing the calibration rod 11 in the center of the plane calibration plate 9, and a target ball seat hole 9b-e for placing the target ball of the laser tracker in the four corners and a mounting bracket for fixing on the mounting frame. Holes 9f-i. The electric spindle mounting seat 5 is connected to the feed module 3 and the electric spindle 4 , the feed module 3 can drive the electric spindle 4 to move linearly, and there is a fixed large target ball seat 6 on the electric spindle mounting seat 5 . Four laser distance measuring sensors 7a~d are evenly distributed and obliquely installed on the pressing head 8, and the moving industrial robot arm 1 moves the hole-making end effector to the front of the plane calibration plate 9, and the four laser beams are directed at a certain angle. On the plane calibration board 9, the laser points are placed on the surface of the plane calibration board 9, and the four laser ranging sensors 7a-d all have a distance return value. Since the laser ranging sensors 7a-d need to receive the returned laser beam information through laser ranging, the surface of the plane calibration plate 9 needs to have strong reflection ability and cannot be made of black material, so the material of the plane calibration plate 9 is aluminum alloy.

Referring to Figure 2, {W} is the coordinate system of the laser tracker during the measurement process, which is set as the world coordinate system. After the target ball is placed on the target ball seat, the measuring point of the laser tracker is the center of the target ball. {T} is the tool coordinate system, in which, the Z _T axis is the feed direction of the electric spindle 4; the O _T point is located at the position 25mm from the front end of the compression plane of the compression head 8 along the Z _T axis direction, and the target ball seat is installed on the calibration rod 11 When the bottom surface of the target ball seat and the pressing plane of the compression head 8 are tightly fitted, the center of the target ball placed on the target ball seat is exactly the TCP point, that is, the O _T point; the X _T axis is perpendicular to the feed module 3 The direction of the motion plane; the Y _T axis is perpendicular to the X _T axis and the Z _T axis. {B} is the workpiece coordinate system, wherein, the O _B point is the measurement point of the D target ball seat hole 9e; the Z _B axis is perpendicular to the direction of the surface of the plane calibration plate 9; when the Z _T axis of the tool coordinate system {T} is perpendicular to When the surface of the plane calibration plate 9 is used, the X _B axis is parallel to the intersection line between the surface of the plane calibration plate 9 and the X _T O _T Z _T plane in the tool coordinate system {T}, and points to the measurement point of the C target ball seat hole 9d; Y _B axis perpendicular to the X _B axis and the Z _B axis.

The specific implementation steps of the laser ranging sensors 7a-d calibration method are as follows:

Step 1: Referring to Figure 1, install one end of the calibration rod 11 on the electric spindle 4, install the plane calibration plate 9 on the protruding end of the calibration rod 11, install the small target ball seat 12 on the end surface of the protruding end, and place the The target ball that is connected with the laser tracker is fixed on the small target ball seat 12.

Step 2: The feed module 3 drives the motorized spindle 4 to move to a suitable position, and uses a laser tracker to measure the coordinates of the target ball in the world coordinate system {W}. This point is marked as P ₁ , and the plane calibration plate 9 is rotated several times. , respectively record the readings of the four laser ranging sensors 7a-d at different angles on the plane calibration plate 9, and obtain a set of data:

Wherein, d ₁ , d ₂ , d ₃ , and d ₄ are 1*n matrices (n is the number of rotations), corresponding to the degrees of the four laser ranging sensors 7a-d.

Move the electric spindle 4 multiple times and repeat this step to obtain multiple target ball points P ₂ , P ₃ . . . P _m , and multiple sets of data D ₂ , _{D 3} .

Step 3: According to the position coordinates of the target ball obtained in step 2 and the readings of the laser ranging sensors 7a-d, calculate the angle between the sagittal direction of each laser beam and the moving direction of the main shaft, and the calculation steps are as follows:

1) Take the average of each row of data from D ₁ to D _m to get

2) Fit a straight line to points P ₁ , P ₂ , P ₃ ... P _m in the software that comes with the laser tracker, and take point P ₁ as the zero point, and measure the distance between points P ₁ ~ P _m and point P ₁ respectively. The distance between z ₁ ～z _m ;

3) Take the distance value z ₁ ~ z _m as the abscissa, and the corresponding data of each laser ranging sensor 7a ~ d as the ordinate, draw a scatter diagram, and add four trend lines, according to the slope k _i of the trend line can be Calculate the angle α _i (i=1,2,3,4) between the sagittal direction of each laser beam and the moving direction of the main axis, and the relationship is as follows:

Step 4: Remove the plane calibration plate 9, move the position of the electric spindle 4, and install a large target ball seat on the protruding end of the calibration rod 11 to ensure that the bottom surface of the target ball seat is closely attached to the pressing plane of the compression head 8.

Step 5: Carry out TCP calibration with the help of the laser tracker, and establish the tool coordinate system {T}, where the Z _T axis is the feed direction of the electric spindle 4; the O _T point is located at the front end of the compression plane of the compression head 8 along the Z _T axis direction 25mm The position is exactly the measuring point of the installed target ball; the X _T axis is perpendicular to the movement plane direction of the feed module 3; the Y _T axis is perpendicular to the X _T axis and the Z _T axis. After the coordinate system is established, the calibration rod 11, the target ball and the target ball seat installed on the electric spindle 4 are removed.

Step 6: Referring to Figure 2, fix the plane calibration plate 9 on the mounting frame 10, place the target ball seats on the target ball seat holes 9b-e of A, B, C, and D respectively, and measure the four points with a laser tracker. The position of the point is fitted to the workpiece plane.

Step 7: Move the hole-making end effector to a certain distance in front of the plane calibration plate 9 through the industrial mechanical arm 1, place the large target ball on the large target ball seat 6 fixed on the electric spindle mounting seat 5, and move the electric spindle several times 4. Measure the coordinates of the target ball at each position in the world coordinate system {W}, and fit a straight line according to the coordinates of the measured points, which is the feed direction of the electric spindle 4, and calculate the feed direction of the electric spindle 4 and The included angle of the workpiece plane, the industrial mechanical arm 1 drives the hole-making end effector to rotate the corresponding angle around the X _T axis and Y _T axis of the tool coordinate system {T} around the TCP point as the center, repeat this step until the electric spindle 4 enters The direction is perpendicular to the workpiece plane.

Step 8: Establish a workpiece coordinate system {B} parallel to the tool coordinate system {T}: O _B point is the measurement point of D target ball seat hole 9e; Z _B axis, X _B axis, Y _B axis are respectively connected to the tool coordinate system The Z _T axis, X _T axis, and Y _T axis of {T} are consistent.

Step 9: Record the current position as state 1, measure the coordinate S ₁ of the target ball in the world coordinate system {W} when the feed of the electric spindle 4 is 0 with the help of the laser tracker, and record the data of the four laser distance measuring sensors 7a~d d ₁₀ , d ₂₀ , d ₃₀ , d ₄₀ .

Step 10: The industrial mechanical arm 1 drives the hole-making end effector to rotate a certain angle around the X _T axis of the tool coordinate system {T} around the TCP point, and record the data d _X11 and d _X21 of the four laser ranging sensors 7a~d , d _X31 , d _X41 , move the electric spindle 4 multiple times, and fit the feed direction of the electric spindle 4 according to the method in step 7, and then calculate the feed direction of the electric spindle 4 and the Z _B axis of the workpiece coordinate system {B} The included angle θ _X1 .

Step 11: According to Step 10, adjust the rotation angle of the hole-making end effector around the X _T axis of the tool coordinate system {T} several times, and record the data d _X1i , d _X2i , d _X3i , d _X4i (i=2, 3, 4...), and calculate the angle θ _Xi between the feed direction of the electric spindle 4 and the Z _B axis of the workpiece coordinate system {B}.

Step 12: The industrial mechanical arm 1 drives the hole-making end effector to return to state 1, and then drives it to rotate a certain angle around the Y _T axis of the tool coordinate system {T} with the TCP point as the center, and records the four laser ranging sensors 7a ～d data d _Y11 , d _Y21 , d _Y31 , d _Y41 , and calculate the angle θ _Y1 between the feed direction of the electric spindle 4 and the Z _B axis of the workpiece coordinate system {B} according to the method in step 10.

Step 13: According to Step 12, adjust the rotation angle of the hole-making end effector around the Y _T axis of the tool coordinate system {T} several times, and record the data d _Y1i , d _Y2i , d _Y3i , d _Y4i (i=2, 3, 4...), and calculate the angle θ _Yi between the feed direction of the electric spindle 4 and the Z _B axis of the workpiece coordinate system {B}.

Step 14: According to the data obtained in steps 9-13 and the geometric relationship, calculate the relative positional relationship between the four laser points in state 1, and establish a coordinate system parallel to the workpiece {B with the laser point of the A laser distance measuring sensor 7a as the origin }’s state coordinate system 1{S ₁ }, get the coordinates of each laser point:

Refer to Figure 3 and Figure 4, taking the rotation around the Y _T axis of the tool coordinate system {T} as an example. O _r is the theoretical center point, on the straight line swept by the tool tip when the electric spindle 4 is fed. r ₀ is the distance from point O _r to point A. Points A, B, C, and D are the emission points of the laser beam. If there is no installation error, the four points should be on a circle centered on point O _r and radius r ₀ , and the plane where the circle is located is parallel to the tool coordinates It is the X _T O _T Y _T plane of {T}. α ₁ , α ₂ , α ₃ , and α ₄ are the included angles between the corresponding laser beam and the Z _T axis of the tool coordinate system {T}. Points A', B', C', D' are the laser points corresponding to the laser beam hitting the unrotated workpiece plane, points A", B", C", D" are the corresponding laser beam hitting the workpiece plane after rotation laser dot on the The workpiece plane does not move, and the hole-making end effector rotates θ _Y1 around the Y _T axis, which is equivalent to the hole making end effector not moving, and the workpiece plane rotates θ _Y1 around the Y _T axis. Project all the laser beams in Figure 3 to the X _T O _T Z _T plane of the tool coordinate system {T} to obtain the geometric relationship in Figure 4. Among them, the actual distance AA'=d ₁₀ , BB'=d ₂₀ , CC'=d ₃₀ , DD'=d ₄₀ , AA"=d _Y11 , BB"=d _Y21 , CC"=d _Y31 , DD"=d _Y41 . Note: The actual distance between point A and point A' is represented by AA', and the projected distance in the plane is represented by , and the rest are similar.

Suppose the space equation of the straight line where the laser beams of the laser ranging sensors 7a-d of A-D are:

Then the vectors corresponding to the four straight lines are:

Referring to Figure 5, taking the geometric relationship between A laser beam and B laser beam as an example, solve length. Among them, the origin O ₁ of the state coordinate system 1 {S ₁ } coincides with the point A', and the X ₁ axis, Y ₁ axis, and Z ₁ axis are parallel to the X _T axis, Y _T axis, Z _T axis of the tool coordinate system {T} axis. Angles β ₁ and β ₂ are projections _The angle with the X1 axis. The following geometric relationship exists,

A'A"=AA'-AA"=d ₁₀ -d _Y11

B'B"=BB'-BB"=d ₂₀ -d _Y21

is the projection of the laser beam directions A'A", B'B" in the direction of the Z _T axis, so,

Let the included angles between A'A", B'B" and the X _T O _T Z _T plane of the tool coordinate system {T} be It can be obtained according to the vector of the straight line in space:

The solution process of angle β ₁ and β ₂ is as follows:

then the projection distance The solution process is as follows:

Move B"B"' parallel to A"B" ₁ , in the formed ΔA"'B"'B" ₁ ,

distance That is, in state 1, laser beams A and B hit the plane perpendicular to the main axis, and the positional relationship of the laser point on the X ₁ axis under the state coordinate system 1{S ₁ }. In order to eliminate the influence of other factors and obtain position information more accurately, the method of taking the average of multiple measurements is adopted. According to the different angle values θ _Yi of the hole-making end effector rotating around the Y _T axis of the tool coordinate system {T}, and the obtained return values of the laser ranging sensors 7a-d, multiple value, and finally take the average value as the positional relationship of the laser spot on the X1 axis of the _A and B laser beams on the plane.

Similarly, the positional relationship of the laser point on the Y ₁ axis under the state coordinate system 1{S ₁ } can be calculated, and then the coordinates of each laser point under the state coordinate system 1{S ₁ } can be calculated:

Because the positions of all laser points are in the X ₁ O ₁ Y ₁ plane under the state coordinate system 1{S ₁ }, the Z ₁ coordinate value of all points is 0. All the variables of a and b are functions of the vector parameters of the space line equation.

Step 15: Adjust the distance between the hole-making end effector and the plane calibration plate 9 several times, according to step 9, record it as state j (j=2,3,4,...,q), repeat steps 9-14 , record the coordinates S _j of the target ball in the world coordinate system {W} when the feed of the electric spindle 4 is 0, and calculate the coordinates of each laser point in the state coordinate system j{S _j } according to the method in step 14:

Step 16: Calculate the conversion relationship between the state coordinate systems according to the relative positional relationship between the states, and convert the coordinates of all points to the state coordinate system 1 {S ₁ }, according to each laser ranging sensor 7a The q laser points obtained from ~d can fit a ray, that is, the positions of the emission points and the sagittal directions of the laser beams of the four laser ranging sensors 7a~d are calibrated:

Since all state coordinate systems are parallel to the tool coordinate system {T}, there is a translation relationship between each state coordinate system, and there is no angular transformation relationship. Let the translation transformation matrix of the state coordinate system j{S _j } relative to the state coordinate system 1{S ₁ } be p _j , namely

p _j ＝(x _j ,y _j ,z _j )

Among them, z _j is the distance between point S _j in the world coordinate system {W} and point S ₁ in the direction of Z and _B axes of the workpiece coordinate system {B} measured by the laser tracker.

Transform the points in each state coordinate system to the state coordinate system 1{S ₁ } to obtain the following q sets of coordinates:

Bring the coordinates of all points into the corresponding straight line equation, add the corresponding angle constraints, and then apply the least square method to obtain the space equation of the straight line where the laser beams of the four laser ranging sensors 7a-d are located. Finally, the position of the laser emitting point is calculated according to the return values of the laser ranging sensors 7a-d when the feeding direction of the electric spindle 4 is perpendicular to the workpiece plane under different states.

The present invention has following technical effect:

1) The present invention can accurately measure the position of each point by means of a laser tracker, accurately obtain the tool coordinate system {T} and the workpiece coordinate system {B}, and obtain the angle between the line and the surface conveniently and accurately;

2) The calibration process of the present invention adopts the method of multiple measurements to make the calibration results more accurate;

3) The emission point position and laser beam sagittal direction of the laser ranging sensors 7a-d calibrated by the present invention are applied to the normal line detection of the drilling process, and the normal vector of the drilling point on the surface of the workpiece can be accurately found;

The calibration method proposed by the present invention is not limited to the detection of the normal direction of the hole, and can be applied to other situations where the position and sagittal direction of the beam emission point need to be calibrated, and the number of beams is 2 or more.

Claims (1)

1. A kind of 1. laser range sensor scaling method, it is characterised in that：

   Device used in the inventive method includes laser tracker, industrial machinery arm, ring flange, drilling end effector, mark Fixed pole, plane reference plate and mounting bracket, wherein drilling end effector mainly include feeding module, electro spindle, electro spindle installation Seat, big target ball seat, small target ball seat, hold-down head and four laser range sensors etc..Ring flange be used for connect industrial machinery arm and Drilling end effector.Demarcate bar uses multi-diameter shaft mode, and one end may be coupled on electro spindle, and the other end can be with vertical connection Plane reference plate.Plane reference plate center has one to be used to installing the hole of demarcate bar, four angles have respectively one be used to placing it is sharp The target ball bore of optical tracker system target ball and the installation fixing hole for being fixed on mounting bracket.Electro spindle mounting seat connection feeding mould Block and electro spindle, feeding module can drive electro spindle to be moved along a straight line, and have a fixed big target in electro spindle mounting seat Ball seat.Four laser range sensors it is uniform it is tilting be arranged on hold-down head, mobile industrial mechanical arm is by drilling end effector It is moved in front of plane reference plate, four laser beams at an angle beat in plane reference by directive plane reference plate, laser spots Plate surface, four laser range sensors have one apart from return value.Because laser range sensor is by laser ranging, need The laser beam information of return is received, so plane reference plate surface need to possess stronger albedo, it is impossible to it is black material, Therefore plane reference plate material selects aluminium alloy.Coordinate system inside laser tracker is world coordinate system.

   By above-mentioned connection, the hardware platform that laser range sensor is demarcated is constituted.

   The method of laser range sensor demarcation includes order below step：

   Step 1：One end of demarcate bar is arranged on electro spindle, plane reference plate is arranged on to the external part of demarcate bar, will be small Target ball seat is arranged on the endface position of external part, will be fixed on the target ball that laser tracker connects on target ball seat；

   Step 2：Feeding module drives electro spindle to be moved to a suitable position, and measure target ball with laser tracker sits in the world Coordinate under mark system, multiple rotational plane scaling board, records four laser rangings under different angle of plane reference plate respectively The reading of sensor, electro spindle is repeatedly moved, repeat the step；

   Step 3：The target ball position coordinates and the reading of laser range sensor obtained according to step 2, calculates each laser beam The angle angle of arrowhead and electro spindle moving direction；

   Step 4：Plane reference plate is removed, mobile electro spindle position, one big target ball seat is installed in demarcate bar external part, ensured Target ball seat bottom surface is brought into close contact with hold-down head clamping plane；

   Step 5：TCP demarcation is carried out by laser tracker, tool coordinates system is established, then removes the mark on electro spindle Fixed pole and target ball, target ball seat；

   Step 6：Plane reference plate is fixed on mounting bracket, four target ball seats on plane reference plate are measured by laser tracker The coordinate of mounting hole, fits workpiece planarization；

   Step 7：At a certain distance from drilling end effector is moved in front of plane reference plate by industrial machinery arm, by big target ball The big target ball seat for being fixed on electro spindle mounting seat is positioned over, electro spindle is repeatedly moved, each position is measured under world coordinate system The coordinate of target ball, straight line, as electro spindle direction of feed are gone out according to the coordinate fitting of the point measured, electro spindle is calculated and enters To direction and the angle of workpiece planarization, industrial machinery arm drives drilling end effector to be sat successively around instrument centered on TCP points X-axis, the corresponding angle of Y-axis rotation of system are marked, repeats the step until electro spindle direction of feed is vertical with workpiece planarization；

   Step 8：Establish the workpiece coordinate system parallel with tool coordinates system；

   Step 9：Current location is designated as state 1, by laser tracker measure electro spindle feeding be 0 when target ball in world coordinate system Under coordinate, record four laser range sensor data；

   Step 10：It is certain that industrial machinery arm drives drilling end effector to be rotated centered on TCP points around the X-axis of tool coordinates system Angle, record four laser range sensor data, repeatedly move electro spindle, according to the method for step 7, fit electro spindle Direction of feed, then calculate the angle of the Z axis of electro spindle direction of feed and workpiece coordinate system；

   Step 11：According to step 10, the angle that drilling end effector rotates around the X-axis of tool coordinates system, record are repeatedly adjusted Four laser range sensor data, and calculate the angle of the Z axis of electro spindle direction of feed and workpiece coordinate system；

   Step 12：Industrial machinery arm drive drilling end effector return to state 1, then drive its centered on TCP points around The Y-axis of tool coordinates system rotates certain angle, records four laser range sensor data, and according to the method for step 10 Calculate the angle of the Z axis of electro spindle direction of feed and workpiece coordinate system；

   Step 13：According to step 12, the angle that drilling end effector rotates around the Y-axis of tool coordinates system, record are repeatedly adjusted Four laser range sensor data, and calculate the angle of the Z axis of electro spindle direction of feed and workpiece coordinate system；

   Step 14：The data and geometrical relationship obtained according to step 9~13 calculate the phase between 1 lower four laser spots that do well To position relationship, the state seat parallel to tool coordinates system is established using the laser spots of one of laser range sensor as origin Mark system 1, obtain the coordinate of each laser spots；

   Step 15：Repeatedly adjustment the distance between drilling end effector and plane reference plate, according to step 9, is designated as shape respectively State j (j=2,3,4 ... ..., q), repeat step 9~14, obtains the coordinate of each laser spots under coordinate system j；

   Step 16：According to the relative position relation between each state, the transformational relation between each coordinate system under each state is calculated, By coordinate a little be transformed under the same coordinate system, the q laser spots obtained according to each laser range sensor To fit a ray, that is, the launch point position and laser beam arrowhead of four laser range sensors are calibrated.

   The laser range sensor scaling method has the following technical effect that：

   1) present invention can accurately measure the position of each point by means of laser tracker, obtain exactly tool coordinates system and Workpiece coordinate system, easily and accurately obtain the angle between line and face；

   2) calibration process of the present invention makes calibration result more accurate using the method repeatedly measured；

   3) launch point position for the laser range sensor that the present invention calibrates and laser beam arrowhead are applied to drilling process normal Detection, the normal vector of workpiece surface drilling point can be correctly found；

   Scaling method proposed by the present invention is not limited to the detection of drilling normal direction, and can be applied to other needs to demarcate light beam launch point position Put the situation with arrowhead, light beam number be 2 and more than.