Optimization design method for measuring rod of multi-station mechanical arm calibration device

Abstract

The invention discloses a measuring rod optimization design method of a multi-station mechanical arm calibration device. The method comprises the following steps: (1) mounting a group of measuring rods with structural parameters at the tail end of a mechanical arm; (2) the 3D measuring device is placed at one station of the multi-station base, attitude angles of the measuring rods are evenly distributed in the measuring space of the 3D measuring device, the joint angle of the mechanical arm is solved, and then the joint angle of the mechanical arm is obtained through configuration screening; (3) placing the 3D measuring device on other stations of the multi-station base, and repeating the step (2) to obtain all pose joint angles; (4) selecting measured joint angles based on the observability indexes to obtain an observability index of an optimal measured joint angle combination, and recording the observability index as an optimal observability index; and (5) in the off-line simulation environment, the measuring rods with different structural parameters are sequentially installed at the tail end of the mechanical arm, the steps 2-4 are repeated, the optimal observation indexes corresponding to the different measuring rods are obtained, and the optimal structural parameters of the measuring rods are determined.

Description

Technical Field

[0001] The invention relates to the field of robots, and in particular to a method for optimizing the design of a measuring rod of a multi-station mechanical arm calibration device. Background Art

[0002] Taking a robot calibration device based on multi-station measurement with Chinese invention patent application number 202110278848.0 as an example, it includes a calibrated device, a calibration device, and a multi-station template. The multi-station template provides multiple calibration measurement positions for expanding the calibration measurement range of the calibration device for the calibrated device. The positional relationship between the calibrated device and the calibration device is: the calibrated device is connected to the robot arm and the calibration device is connected to the multi-station template, or the calibration device is connected to the robot arm and the calibrated device is connected to the multi-station. The calibration device of the present invention can calibrate the robot at any time on the industrial site. The operation is simple and convenient, and the calibration accuracy is higher. The multi-station template is used to realize the calibration device in the measurement of multiple stations, and a larger performance measurement range can be obtained. At the same time, the relative position between each station is a known information, which can be used for the robot kinematic parameters to improve the calibration accuracy.

[0003] However, when this method is used to calibrate the kinematic parameters of the robot arm, if the measuring rod is too short, the robot arm cannot move in a larger spatial range, affecting the measurement diversity and resulting in low calibration accuracy; if the measuring rod is too long, the robot arm is also easily "stretched", and the attitude angle adjustment range of the point movement may still be affected, and it will also cause the rigidity of the measuring rod to be low, which is not conducive to obtaining a higher actual measurement accuracy. Therefore, it is necessary to optimize the design of the most suitable measuring rod for different robot arms to maximize the calibration accuracy. Summary of the invention

[0004] The purpose of the present invention is to provide a method for optimizing the design of a measuring rod of a multi-station robot arm calibration device, so as to solve the existing technical defects and unattainable technical requirements.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for optimizing the design of a measuring rod of a multi-station robot arm calibration device comprises the following steps:

[0007] (1) In an offline simulation environment, a set of structural parameter measurement rods are installed at the end of the robot arm, and a multi-station base is set near the base of the robot arm;

[0008] (2) The 3D measuring device is placed at one of the stations of the multi-station base, the point constraint of the measuring ball center at the end of the measuring rod is maintained, the attitude angle of the measuring rod is evenly distributed in the measurement space of the 3D measuring device, the corresponding joint angle of the robot arm is solved based on the inverse kinematics of the robot arm, and then it is screened through configuration screening, and finally a large number of feasible and reasonable joint angles of the robot arm are obtained, and the configuration screening includes simulation collision detection;

[0009] (3) Place the 3D measurement device on other stations of the multi-station base and repeat step 2 to finally obtain all feasible and reasonable joint angles;

[0010] (4) Selecting the measured joint angles based on the observability index, selecting the optimal measured joint angle combination from all feasible and reasonable joint angles, and obtaining the observability index of the optimal measured joint angle combination, which is recorded as the optimal observability index;

[0011] (5) In an offline simulation environment, measuring rods with different structural parameters are installed at the end of the robot arm in turn, and steps 2-4 are repeated to obtain the optimal observability index corresponding to different measuring rods. The optimal structural parameters of the measuring rod are determined using the optimal observability index as the evaluation index.

[0012] Preferably, the main body of the measuring rod is a curved pipe with a bent section in the middle, one end of the measuring rod is connected to the flange connection seat at the end of the robot arm, and the other end of the measuring rod is connected to the measuring ball, the measuring rod includes a first pipe section and a second pipe section, and the lengths of the first pipe section and the second pipe section are L1 and L2 respectively, and the angle between the first pipe section and the second pipe section is γ;

[0013] The coordinates of the center of the measuring ball at the end of the measuring rod relative to the center of the flange mounting surface at the end of the robot arm are:

[0014]

[0015] Preferably, the angle between the first pipe section and the second pipe section is 90°≤γ<180°.

[0016] Preferably, in step 5, when determining the optimal structural parameters of the measuring rod with the optimal observability index as the evaluation index, for each set of structural parameters of the measuring rod, it is necessary to repeat the experiment multiple times, and each experiment requires changing the relative position between the multi-station base and the robotic arm, and then repeat steps 2-4 to generate multiple optimal observability indexes, and then select the highest value as the final evaluation index.

[0017] Preferably, the measurement space of the 3D measuring device refers to defining the intersection of the axes of three orthogonally placed displacement sensors as O1, taking point O1 or a point O2 near point O1 as the measuring point, and making three reference surfaces through the measuring point that are parallel to the measuring planes of the three displacement sensor probes. The three reference surfaces divide the spherical space with the measuring point as the center into eight equal parts, and taking one-eighth of the open area facing outwards of the three displacement sensors as the measurement space.

[0018] Preferably, the specific method of measuring the attitude angle of the spatially uniformly distributed measuring rod of the 3D measuring device is as follows: the coordinates on the spherical surface are defined by the longitude and latitude in geography according to a certain division value, and the direction of the line connecting the intersection of each longitude and latitude line and the center of the sphere is the z-axis direction of the measuring spherical coordinate system of the end of the robot arm in the measured posture, and the direction of the x-axis is obtained by rotating an initial x-axis around the z-axis by an angle γ, and the angle γ is obtained by rotating an initial x-axis around the z-axis by an angle γ from -180° to 180° with a division value d γ By traversing and determining the z-axis and the x-axis, the entire end measurement spherical coordinate system can be determined;

[0019] Alternatively, instead of using longitude and latitude to define the coordinate points on the sphere, the points can be evenly distributed on the sphere, and the direction of the line connecting the evenly distributed points and the center of the sphere is defined as the z-axis direction of the spherical coordinate system measured by the end of the manipulator. The direction of the x-axis is obtained by rotating an initial x-axis around the z-axis by an angle γ, which is divided into a scale value d from -180° to 180°. γ By traversing and determining the z-axis and the x-axis, the entire end measurement spherical coordinate system can be determined.

[0020] Preferably, the simulated collision detection is that if the robotic arm moves to a certain joint angle and will cause self-collision or collision with the outside world, the joint angle will be eliminated, and the collision detection in the simulation will be judged. The self-collision refers to the collision between the joint links of the robotic arm, and the collision with the outside world refers to the collision between the robotic arm and the ground, the multi-station base, and the 3D measuring device.

[0021] Preferably, the observable index can characterize the degree of pathological condition of the Jacobian matrix when the kinematic parameters are identified based on the optimization method, and is specifically one of OI1, OI2, OI3, OI4 and OI5:

[0022]

[0023] OI3=σ q (15-3)

[0024]

[0025] Among them, σ i (i=1,2,..,q,σ q≤...≤σ1)1 is the singular value of the Jacobian matrix J, q is the number of singular values, m is the number of data sets, and there are many ways to evaluate the observability index. The larger the OI value, the better the flexibility of the robot under this group of joint angles.

[0026] Preferably, the measurement of the joint angle is performed using a DETMAX algorithm, and the specific steps are as follows:

[0027] Randomly select m groups of data from all feasible and reasonable joint angle data, and calculate the observation index values ​​corresponding to these m groups of data;

[0028] In the remaining Traverse the group data to find a group of data, so that the observation index value corresponding to the (m+1) group of data after adding the group of data originally selected is the largest;

[0029] Traverse and select a group of data from the (m+1) groups of data so that the observed index value of the m groups of data after deleting the group of data is the largest;

[0030] This cycle is repeated continuously until the group of data deleted is exactly the group of data added, thereby obtaining the m groups of data with the largest observable index values ​​and realizing the selection of the optimal measurement joint angle combination.

[0031] Preferably, in step 5, when determining the optimal measuring rod structural parameters with the optimal observability index as the evaluation index, it is necessary to set multiple groups of alternative values ​​for the three structural parameters L1, L2 and γ respectively, and then arrange and combine the alternative values ​​of the three structural parameters to form multiple groups of structural parameters, and then repeat steps 2-4 for the measuring rod of each group of structural parameters multiple times to generate multiple optimal observability indexes, and then select the highest value from them as the optimal measuring rod structural parameter.

[0032] Preferably, in step 5, when determining the optimal measuring rod structural parameters using the optimal observability index as the evaluation index, the specific process is as follows:

[0033] a. Select a set of initial structural parameters L1, L2 and γ;

[0034] b. Optimize one of the structural parameters as the parameter to be optimized, keep the other structural parameters fixed as fixed parameters, search for a new value near the original value of the parameter to be optimized, and adjust the parameter to be optimized to the new value so that the optimal observability index of the group of structural parameters is maximized, thereby completing a parameter transformation;

[0035] c. Repeat step b with the other parameters as the parameters to be optimized, thus completing a round of parameter rotation;

[0036] d. Repeat steps bc continuously and perform multiple rounds of parameter rotation. When the optimal observability index no longer increases or the increase is less than the threshold, exit the loop and output the structural parameters L1, L2 and γ that obtain the largest optimal observability index during the rotation process as the optimal measuring rod structural parameters to complete the iterative optimization.

[0037] Compared with the prior art, the beneficial effect of the present invention is that by sequentially installing measuring rods with different parameters at the end of the mechanical arm and performing simulated collision detection on them, the optimal observability index is obtained, thereby determining the optimal structural parameters of the measuring rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a stereogram of the measuring rod;

[0039] Figure 2 It is a side cross-sectional view of the measuring rod;

[0040] Figure 3 This is a structural diagram of the 3D measuring device installed on the multi-station base;

[0041] Figure 4 The schematic diagram of the mechanism for installing the measuring rod on the robotic arm;

[0042] Figure 5 is the observation index value when the angle γ is 90°;

[0043] Figure 6 is the observation index value when the angle γ is 135°. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] like Figure 1 and Figure 2The main body of the measuring rod 13 is a curved pipe with a bending section in the middle, one end of the measuring rod 13 is connected to a flange connection seat 1304, and the flange connection seat 1304 is connected to the standard flange adapter at the end of the robotic arm 11, and the other end of the measuring rod 13 is connected to the measuring ball 12, the measuring rod 13 includes a first pipe section 1301 and a second pipe section 1302, a first threaded joint 1303 is provided at the rear end of the first pipe section 1301, and the first threaded joint 1303 is connected to the flange connection seat 1304 through threads, a second threaded joint 1307 is provided at the front end of the second pipe section 1302, and the second threaded joint 1307 is connected to the ball seat 1305 through threads, and the measuring ball 12 is arranged on the ball seat 1305, the lengths of the first pipe section 1301 and the second pipe section 1302 are L1 and L2 respectively, and the angle between the first pipe section 1301 and the second pipe section 1302 is γ.

[0046] The coordinates of the center of the measuring ball 12 at the end of the measuring rod 13 relative to the center of the flange mounting surface at the end of the mechanical arm 11 are:

[0047]

[0048] The included angle between the first pipe section and the second pipe section is 90°≤γ<180°.

[0049] like Figure 3 and Figure 4 The 3D measuring device 8 is installed on the multi-station base 2, and the mechanical arm 11 drives the measuring ball 12 on the measuring rod 13 to enter the measuring part of the 3D measuring device 8 for detection.

[0050] A method for optimizing the design of a measuring rod 13 of a multi-station robot arm calibration device comprises the following steps:

[0051] (1) In an offline simulation environment, a set of structural parameter measurement rods 13 are installed at the end of a robotic arm 11;

[0052] (2) The 3D measuring device 8 is placed at one of the stations of the multi-station base 2, and the point constraint of the center of the measuring ball 12 at the end of the measuring rod 13 is maintained. The posture angle of the measuring rod 13 is evenly distributed in the measurement space of the 3D measuring device 8, and the corresponding joint angle of the robot arm 11 is solved based on the inverse kinematics of the robot arm 11, and then it is screened through configuration screening, and finally a large number of feasible and reasonable joint angles of the robot arm 11 are obtained, and the configuration screening includes simulated collision detection;

[0053] (3) placing the 3D measuring device 8 on other stations of the multi-station base 2 and repeating step 2, and finally obtaining all feasible and reasonable posture joint angles;

[0054] (4) Selecting the measured joint angles based on the observability index, selecting the optimal measured joint angle combination from all feasible and reasonable joint angles, and obtaining the observability index of the optimal measured joint angle combination, which is recorded as the optimal observability index;

[0055] (5) In an offline simulation environment, measuring rods 13 with different structural parameters are installed at the end of the robot arm 11 in turn, and steps 2-4 are repeated to obtain the optimal observability index corresponding to different measuring rods 13, and the optimal structural parameters of the measuring rod 13 are determined using the optimal observability index as the evaluation index.

[0056] In step 5, when determining the optimal structural parameters of the measuring rod 13 using the optimal observability index as the evaluation index, for each set of structural parameters of the measuring rod 13, it is necessary to repeat the experiment multiple times, and each experiment requires changing the relative position between the multi-station base 2 and the robot arm 11, and then repeating steps 2-4 to generate multiple optimal observability indexes, and then selecting the highest value as the final evaluation index.

[0057] The measurement space of the 3D measuring device 8 refers to defining the intersection of the axes of three orthogonally placed displacement sensors as O1, taking point O1 or a point O2 near point O1 as the measuring point, and making three reference surfaces through the measuring point that are parallel to the measuring planes of the three displacement sensor probes. The three reference surfaces divide the spherical space with the measuring point as the center into eight equal parts, and taking the one-eighth open area facing outwards of the three displacement sensors as the measurement space.

[0058] The specific method of measuring the attitude angle of the spatially uniform measuring rod 13 of the 3D measuring device 8 is as follows: the coordinates on the spherical surface are defined by the longitude and latitude in geography according to a certain division value, and the direction of the line connecting the intersection of each longitude and latitude line and the center of the sphere is the z-axis direction of the coordinate system of the measuring sphere 12 at the end of the robot arm 11 in the measured posture, and the x-axis direction is obtained by rotating an initial x-axis around the z-axis by an angle γ, and the angle γ is divided into -180°~180° with a division value d γ By traversing, the coordinate system of the entire end measurement ball 12 can be determined by determining the z-axis and the x-axis;

[0059] Alternatively, instead of using longitude and latitude to define the coordinate points on the sphere, the points can be evenly distributed on the sphere, and the direction of the line connecting the evenly distributed points and the center of the sphere is defined as the z-axis direction of the coordinate system of the measuring sphere 12 at the end of the robot 11. The direction of the x-axis is obtained by rotating an initial x-axis around the z-axis by an angle γ, and the angle γ is divided into a scale value d from 180° to 180°. γ By traversing and determining the z-axis and the x-axis, the coordinate system of the entire end measurement ball 12 can be determined.

[0060] The simulated collision detection is that when the robot arm 11 moves to a certain joint angle, it will cause self-collision or collision with the outside world. In this case, the joint angle will be eliminated. Through the collision detection judgment in the simulation, the self-collision refers to the collision between the joint links of the robot arm 11, and the collision with the outside world refers to the collision between the robot arm 11 and the ground, the multi-station base 2, and the 3D measuring device 8.

[0061] The observability index can characterize the degree of pathological condition of the Jacobian matrix when the kinematic parameters are identified based on the optimization method, specifically one of OI1, OI2, OI3, OI4 and OI5:

[0062]

[0063] OI3=σ q (15-3)

[0064]

[0065] Among them, σ i (i=1,2,..,q,σ q ≤...≤σ1)1 is the singular value of the Jacobian matrix J, q is the number of singular values, m is the number of data sets, and there are multiple evaluation methods for the observability index. The larger the OI value, the better the flexibility of the robot arm 11 under this group of joint angles.

[0066] The measurement joint angle selection adopts the DETMAX algorithm, and the specific steps are as follows:

[0067] Randomly select m groups of data from all feasible and reasonable joint angle data, and calculate the observation index values ​​corresponding to these m groups of data;

[0068] In the remaining Traverse the group data to find a group of data, so that the observation index value corresponding to the (m+1) group of data after adding the group of data originally selected is the largest;

[0069] Traverse and select a group of data from the (m+1) groups of data so that the observed index value of the m groups of data after deleting the group of data is the largest;

[0070] This cycle is repeated continuously until the group of data deleted is exactly the group of data added, thereby obtaining the m groups of data with the largest observable index values ​​and realizing the selection of the optimal measurement joint angle combination.

[0071] In step 5, when determining the optimal structural parameters of the measuring rod 13 using the optimal observability index as the evaluation index, it is necessary to set multiple groups of alternative values ​​for the three structural parameters L1, L2 and γ respectively, and then arrange and combine the alternative values ​​of the three structural parameters to form multiple groups of structural parameters, and then repeat steps 2-4 for each group of structural parameters of the measuring rod 13 to generate multiple optimal observability indexes, and then select the highest value as the optimal structural parameter of the measuring rod 13.

[0072] Preferably, in step 5, when determining the optimal structural parameters of the measuring rod 13 using the optimal observability index as the evaluation index, the specific process is as follows:

[0073] a. Select a set of initial structural parameters L1, L2 and γ;

[0074] b. Optimize one of the structural parameters as the parameter to be optimized, keep the other structural parameters fixed as fixed parameters, search for a new value near the original value of the parameter to be optimized, and adjust the parameter to be optimized to the new value so that the optimal observability index of the group of structural parameters is maximized, thereby completing a parameter transformation;

[0075] c. Repeat step b with the other parameters as the parameters to be optimized, thus completing a round of parameter rotation;

[0076] d. Repeat steps bc continuously and perform multiple rounds of parameter rotation. When the optimal observability index no longer increases or the increase is less than the threshold, exit the loop and output the structural parameters L1, L2 and γ that obtain the largest optimal observability index during the rotation process as the optimal structural parameters of the measuring rod 13 to complete the iterative optimization.

[0077] In step 4, the measured joint angle is selected using the DETMAX algorithm, and the specific steps are as follows:

[0078] a. Randomly select m groups of data from all feasible and reasonable joint angle data, and calculate the observation index values ​​corresponding to these m groups of data;

[0079] b. In the remaining Traverse the group data to find a group of data, so that the observation index value corresponding to the (m+1) group of data after adding the group of data originally selected is the largest;

[0080] c. Traverse and select a group of data from the (m+1) group of data so that the observed index value of the m group of data after deleting the group of data is the largest;

[0081] d. Continue looping in this way until the group of data deleted is exactly the group of data added, thereby obtaining the m groups of data with the largest observable index value and realizing the selection of the optimal measurement joint angle combination.

[0082] Figure 5 Taking the Stäubli TX90 as the experimental object and limiting the angle γ between the first pipe section 1301 and the second pipe section 1302 to 90°, the experimental results, namely the observable index value OI1, are obtained by changing the combination of different L1 and L2.

[0083] Figure 6 Taking the Stäubli TX90 as the experimental object and limiting the angle γ between the first pipe section 1301 and the second pipe section 1302 to 135°, the experimental results obtained by changing the combination of different L1 and L2, namely the observation index value OI1.

[0084] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0085] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for optimizing the design of a measuring rod of a multi-station robot arm calibration device, characterized in that: The following steps are involved: (1) In an offline simulation environment, a set of structural parameter measurement rods are installed at the end of the robot arm, and a multi-station base is set near the base of the robot arm; (2) The 3D measuring device is placed at one of the stations of the multi-station base, the point constraint of the measuring ball center at the end of the measuring rod is maintained, the attitude angle of the measuring rod is evenly distributed in the measurement space of the 3D measuring device, the corresponding joint angle of the robot arm is solved based on the inverse kinematics of the robot arm, and then it is screened through configuration screening, and finally a large number of feasible and reasonable joint angles of the robot arm are obtained, and the configuration screening includes simulation collision detection; (3) Place the 3D measurement device on other stations of the multi-station base and repeat step 2 to finally obtain all feasible and reasonable joint angles; (4) Selecting the measured joint angles based on the observability index, selecting the optimal measured joint angle combination from all feasible and reasonable joint angles, and obtaining the observability index of the optimal measured joint angle combination, which is recorded as the optimal observability index; (5) In an offline simulation environment, measuring rods with different structural parameters are installed at the end of the robot arm in turn, and steps 2-4 are repeated to obtain the optimal observability index corresponding to different measuring rods. The optimal structural parameters of the measuring rod are determined using the optimal observability index as the evaluation index.

2. The measuring rod optimization design method of a multi-station robot arm calibration device according to claim 1 is characterized in that: The main body of the measuring rod is a curved pipe with a bent section in the middle, one end of the measuring rod is connected to the flange connection seat at the end of the mechanical arm, and the other end of the measuring rod is connected to the measuring ball, the measuring rod includes a first pipe section and a second pipe section, and the lengths of the first pipe section and the second pipe section are L1 and L2 respectively, and the angle between the first pipe section and the second pipe section is γ; The coordinates of the center of the measuring ball at the end of the measuring rod relative to the center of the flange mounting surface at the end of the robot arm are:

3. The measuring rod optimization design method of a multi-station robot arm calibration device according to claim 2 is characterized in that: The angle between the first pipe section and the second pipe section is 90°≤γ<180°.

4. The measuring rod optimization design method of a multi-station robot arm calibration device according to claim 1 is characterized in that: In step 5, when the optimal structural parameters of the measuring rod are determined using the optimal observability index as the evaluation index, for each set of structural parameters of the measuring rod, it is necessary to repeat the experiment multiple times. Each experiment requires changing the relative position between the multi-station base and the robotic arm, and then repeat steps 2-4 to generate multiple optimal observability indexes, and then select the highest value as the final evaluation index.

5. The method for optimizing the design of a measuring rod of a multi-station robot arm calibration device according to claim 1, characterized in that: The measurement space of the 3D measuring device refers to defining the intersection of the axes of three orthogonally placed displacement sensors as O1, taking point O1 or a point O2 near point O1 as the measuring point, and making three reference surfaces through the measuring point that are parallel to the measuring planes of the three displacement sensor probes. The three reference surfaces divide the spherical space with the measuring point as the center into eight equal parts, and taking one-eighth of the open area facing outwards of the three displacement sensors as the measurement space.

6. The method for optimizing the design of a measuring rod of a multi-station robot arm calibration device according to claim 1, characterized in that: The specific method of measuring the attitude angle of the spatially uniformly distributed measuring rod of the 3D measuring device is as follows: the coordinates on the spherical surface are defined by the longitude and latitude in geography according to a certain division value, and the direction of the line connecting the intersection of each longitude and latitude line and the center of the sphere is the z-axis direction of the measuring spherical coordinate system of the end of the robot arm in the measured posture, and the direction of the x-axis is obtained by rotating an initial x-axis around the z-axis by an angle γ, and the angle γ is divided into 180° to 180° with a division value d γ By traversing and determining the z-axis and the x-axis, the entire end measurement spherical coordinate system can be determined; Alternatively, instead of using longitude and latitude to define the coordinate points on the sphere, the points can be evenly distributed on the sphere, and the direction of the line connecting the evenly distributed points and the center of the sphere is defined as the z-axis direction of the spherical coordinate system measured by the end of the manipulator. The direction of the x-axis is obtained by rotating an initial x-axis around the z-axis by an angle γ, which is divided into a scale value d from -180° to 180°. γ By traversing and determining the z-axis and the x-axis, the entire end measurement spherical coordinate system can be determined.

7. The method for optimizing the design of a measuring rod of a multi-station robot arm calibration device according to claim 1, characterized in that: The simulation collision detection is that when the robot arm moves to a certain joint angle, it will cause self-collision or collision with the outside world. In this case, the joint angle will be eliminated. Through the collision detection judgment in the simulation, the self-collision refers to the collision between the joint links of the robot arm, and the collision with the outside world refers to the collision between the robot arm and the ground, the multi-station base, and the 3D measuring device.

8. The method for optimizing the design of a measuring rod of a multi-station robot arm calibration device according to claim 1, characterized in that: The observability index can characterize the degree of pathological condition of the Jacobian matrix when the kinematic parameters are identified based on the optimization method, specifically one of OI1, OI2, OI3, OI4 and OI5: Among them, σ i (i=1,2,...,q,σ q ≤...≤σ1)1 is the singular value of the Jacobian matrix J, q is the number of singular values, m is the number of data sets, and there are many ways to evaluate the observability index. The larger the OI value, the better the flexibility of the robot under this group of joint angles.

9. The method for optimizing the design of a measuring rod of a multi-station robot arm calibration device according to claim 2, characterized in that: In step 5, when determining the optimal measuring rod structural parameters with the optimal observability index as the evaluation index, it is necessary to set multiple groups of alternative values ​​for the three structural parameters L1, L2 and γ respectively, and then arrange and combine the alternative values ​​of the three structural parameters to form multiple groups of structural parameters, and then repeat steps 2-4 for the measuring rod of each group of structural parameters multiple times to generate multiple optimal observability indexes, and then select the highest value from them as the optimal measuring rod structural parameters.

10. The method for optimizing the design of a measuring rod of a multi-station robot arm calibration device according to claim 2, characterized in that: In step 5, when the optimal measuring rod structural parameters are determined using the optimal observability index as the evaluation index, the specific process is as follows: a. Select a set of initial structural parameters L1, L2 and γ; b. Optimize one of the structural parameters as the parameter to be optimized, keep the other structural parameters fixed as fixed parameters, search for a new value near the original value of the parameter to be optimized, and adjust the parameter to be optimized to the new value so that the optimal observability index of the group of structural parameters is maximized, thereby completing a parameter transformation; c. Repeat step b with the other parameters as the parameters to be optimized, thus completing a round of parameter rotation; d. Repeat steps bc continuously and perform multiple rounds of parameter rotation. When the optimal observability index no longer increases or the increase is less than the threshold, exit the loop and output the structural parameters L1, L2 and γ that obtain the largest optimal observability index during the rotation process as the optimal measuring rod structural parameters to complete the iterative optimization.

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