Light-assisted calibration method and system for robotic arm

Abstract

This invention proposes a light source-assisted robotic arm calibration method and system, which eliminates the need for a virtual tool center based on the feature points of a physical tool, effectively solving the difficulties and challenges of existing virtual tool center calibration technologies. Furthermore, compared to traditional point-bar assisted calibration methods, this invention utilizes a combination of high-energy concentrated light source assistance and a visual sensing module, making the entire calibration process faster, more stable, and more efficient. This innovative calibration method is not only suitable for existing production environments but also provides effective support for future applications with high precision requirements.

Description

Technical Field

[0001] A method and system for calibrating a robotic arm, particularly a method and system for calibrating the center point of a robotic arm tool using a light source. Prior Technology

[0002] The demands of high-precision applications have led to an increased need for robotic arm calibration, particularly for tool coordinate systems, including the accuracy of the tool center point (TCP) and tool-axis orientation (TAO). Traditional TCP calibration often relies on visual inspection by field engineers, controlling the robotic arm to move the TCP to the same position in space under different tool orientations. However, this method is time-consuming and susceptible to human error.

[0003] While many existing automatic calibration methods exist, most rely on physical feature identification of the TCP (Technical Point of Contact). However, for virtual TCPs (V-TCPs) where the TCP is not on the tool body, such as imaginary points on the tool axis in spraying and optical inspection applications, a pointed rod is required as an alternative fixture for calibration. This method is prone to the following problems:

[0004] Assembly errors introduced by disassembly and reassembly: After the calibration is completed using a pointed bar as a substitute fixture, the pointed bar must be removed and replaced with the tool required for the actual application. This process is prone to slight deformation due to differences in the screw tightening sequence and force, introducing assembly errors that affect the final calibration accuracy and make it impossible to guarantee the accuracy of the TCP position.

[0005] The design of a tip based on the tool's CAD model can introduce positional deviations: the design of a replacement tip typically relies on the tool's CAD model. However, slight differences may exist between the CAD model and the actual tool, causing the tip's geometry to not perfectly align with the control point (TCP). This deviation directly affects the calibration accuracy, causing TCP errors, and is further amplified, especially in applications requiring high precision.

[0006] Calibration accuracy is affected by the weight of the tip: When the V-TCP is far from the tool body, the weight of the tip fixture becomes another challenge. The tip fixture not only increases the total weight of the tool, but also intensifies the load on the robotic arm, causing deformation of the arm structure and gears, which in turn affects the calibration results; long-distance tip fixtures may even exceed the load limit of the arm, leading to instability in the calibration process, or even damage to the robotic arm, affecting the long-term stability of the system. Summary of the Invention

[0007] To address the shortcomings of existing robotic arms that use pointed rods as alternative fixtures for calibration, such as assembly errors, positional deviations, and the influence of the weight of the pointed rods on calibration accuracy, this invention provides an innovative light source-assisted robotic arm calibration method to improve or at least provide a beneficial alternative to solve the problems of the aforementioned technology.

[0008] The present invention discloses a light source-assisted robotic arm calibration method, the steps of which include: Step 1: An auxiliary calibration module consisting of a rotary table and a concentrated light source, along with a tool module, are mounted on a robotic arm. A vision sensing module is placed adjacent to the robotic arm. By rotating the concentrated light source to four different positions using the rotary table, the intersection point of a tool axis of the tool module and a sensing plane is determined. Then, by controlling the robotic arm accordingly, the conversion relationship between the coordinate system of the vision sensing module and a reference coordinate system of the robotic arm can be obtained. Step 2: Using the rotary table, rotate the concentrated light source around the tool axis, and analyze the intersection of the concentrated light source and the sensing plane. By controlling the robotic arm to make the projection trajectory of the concentrated light source around the rotary table a perfect circle, obtain the sixth axis coordinate system relationship between the tool axis and the robotic arm. Step 3: Control the robotic arm to move the tool module to the same position on the sensing plane in at least one of the aforementioned postures, obtain the coordinates of the virtual tool center relative to the sixth axis coordinate system, and complete the correction of the virtual tool center and the tool axis.

[0009] Before calibrating the virtual tool center and the tool axis, the accurate relative relationship between the concentrated light source and the virtual tool center is obtained before the calibration process is executed.

[0010] During installation, the rotary table must be aligned with the tool axis, and the concentrated light source must intersect the tool axis at a single point.

[0011] Preferably, after fixing the relative position of the rotary table and the tool module, the distance from the rotation center point of the concentrated light source to the tool axis and the distance from the rotation center point of the light source to the virtual tool center along the tool axis are then corrected.

[0012] In this process, the rotation arm of the concentrated light source is adjusted to zero by setting the angle between the concentrated light source and the tool axis, and the vision sensing module is mounted at a position perpendicular to the tool axis as the sensing plane. Then, the rotary table is controlled to rotate, and the change in the position of the intersection point of the concentrated light source and the sensing plane is recorded during the rotation process. The data set of the coordinate system of the vision sensor of the vision sensing module is then used to obtain the equation of the circle and the radius of the circle using the minimum error method.

[0013] The correction system for the distance from the rotation center point of the concentrated light source to the virtual tool center along the tool axis is calculated by obtaining the distance from the rotation center point of the light source to the reference plane along the tool axis, and then adding the translation amount.

[0014] The virtual tool center and tool axis correction method first requires obtaining the coordinate transformation relationship between the visual sensor coordinate system and the robotic arm reference coordinate system, and converting motion control commands into vectors relative to the robotic arm reference coordinate system for motion control. The correction system for the transformation relationship between the visual sensor coordinate system and the robotic arm reference coordinate system will control the robotic arm to move along the direction of the robotic arm reference coordinate system, and use the visual sensor to observe the change in the position of the intersection point of the tool axis and the sensing plane to obtain the movement vector of the tool module relative to the visual sensor coordinate system when it moves along the direction of the robotic arm reference coordinate system. Finally, the transformation matrix between the visual sensor coordinate system and the robotic arm reference coordinate system will be obtained by using the condition that the robotic arm reference coordinate systems are perpendicular to each other in space.

[0015] Preferably, the correction of the conversion relationship between the visual sensor coordinate system and the robotic arm reference coordinate system is performed by identifying the intersection point of the tool axis and the sensing plane through the visual sensor, and by controlling the concentrated light source to rotate around the tool axis through the rotary table so that the concentrated light source forms a conical surface; the intersection point of the tool axis and the sensing plane is calculated by controlling the rotary table to rotate to four different angles and recording the intersection point of the concentrated light source and the sensing plane at each angle.

[0016] The robot arm is controlled to move the tool module in at least one posture to bring the virtual tool center to the same position in space. The combination of the angles of each axis of the robot arm is recorded and the coordinates of the virtual tool center are obtained through kinematic equations.

[0017] Furthermore, the present invention also provides a system used in the aforementioned light source-assisted robotic arm correction method, comprising: A robotic arm with a tool module mounted on it; An auxiliary calibration module includes: a rotary table, a concentrated light source, and a visual sensing module; A rotary table is provided between the tool module and the robotic arm, and a concentrated light source platform extends outward from it. A concentrated light source is mounted on the rotary table. The relative positions of the rotary table, the concentrated light source, the tool module, and the robotic arm are fixed, and one of the rotation axes of the rotary table coincides with one of the tool axes of the tool module, allowing the concentrated light source to rotate around the tool axis and project its light onto a sensing plane; and The vision sensing module is located on the opposite side of the robotic arm relative to the sensing plane. One optical axis of the vision sensor is perpendicular to the sensing plane to identify the intersection of the concentrated light source and the sensing plane, and to control the robotic arm to produce corresponding actions and perform the aforementioned light source-assisted robotic arm correction method.

[0018] Preferably, the concentrated light source used in this invention includes, but is not limited to, laser light; and the visual sensing module includes at least an optical filter and a visual sensor.

[0019] As can be seen from the above description, the present invention has the following beneficial effects and advantages:

[0020] 1. The present invention integrates a rotary table, a concentrated light source module, and a vision sensor to establish an auxiliary calibration system for calibrating the virtual tool center. Through the image projection of the concentrated light source onto the sensing plane, the vision sensor can identify image features on the other side of the sensing plane and control the robotic arm to accurately calibrate the virtual tool center and the tool axis. The present invention not only solves the assembly error problem during disassembly and assembly of existing calibration methods using pointed rods, but also significantly reduces calibration time and compensates for the problem of projection light source deformation.

[0021] 2. The calibration method of the present invention has high efficiency and high precision. When the absolute positioning accuracy of the robotic arm is good, the tool axis and the center of the virtual tool can be moved to a specified position directly by analytical equations. The entire calibration process takes a very short time, far less than the time required by manual calibration methods. Manual methods require skilled operators to complete, and inexperienced operators often cannot achieve accurate calibration results. The method provided by the present invention can completely avoid the accuracy problems caused by human intervention.

[0022] 3. The calibration method of the present invention is not only applicable to short-distance tools, but also effectively avoids the error problems caused by replacing the jig with a pointed rod, further improving calibration accuracy and adaptability, and can provide efficient, stable and highly adaptable solutions for different application scenarios. Simple Explanation of the Diagram

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are merely some examples or embodiments of the present invention and are not intended to absolutely limit the technical scope of the present invention. Unless obvious from the context or otherwise stated, the same reference numerals in the drawings represent the same structures or operations. Wherein: Figure 1 is a schematic diagram of a preferred embodiment of the present invention. Figure 2 is a top view schematic diagram of a preferred embodiment of the present invention. Figure 3 is a flowchart of the correction method according to a preferred embodiment of the present invention. Figure 4 is a schematic diagram of the rotary table assembly fixture according to a preferred embodiment of the present invention. Figure 5 is a schematic diagram of the tool module dimensions according to a preferred embodiment of the present invention. Figure 6A is a schematic diagram showing the relative relationship between the visual sensor and the tool module of the present invention. Figure 6B is a schematic diagram of the trajectory of the concentrated light source of the present invention. Figure 7 shows the correction of the present invention. A schematic diagram. Figure 8A is a 2D view of the concentrated light source being rotated around the tool axis by the rotary table of the present invention, so that the concentrated light source forms a conical surface. Figure 8B is a view of the present invention where the rotary table controls the concentrated light source to rotate around the tool axis, so that the concentrated light source forms a conical surface. Figures 9A-9D show the rotary table of the present invention. System diagram. Figures 10A-10D show the rotating platform of the present invention. Projection position Schematic diagram. Figure 11 shows the present invention. A schematic diagram of the intersection point between the tool axis and the sensing plane is obtained. Figure 12 is a schematic diagram of the intersection curve points of the conical surface of the concentrated light source and the sensing plane of the present invention. Figures 13A and 13B are the intersection point data sets of this invention. Fitting results. Figure 14 is a schematic diagram of the vector loop of the present invention. Figures 15A and 15B illustrate the present invention. A schematic diagram showing the relationship between the cone and the concentrated light source. Figures 16A and 16B are schematic diagrams showing the virtual tool of the present invention located at the center of the sensing plane. Figures 17A, 17B, and 17C illustrate the control method of this invention. and Schematic diagram of overlap. Implementation

[0024] The present invention will be described in detail below with reference to several preferred embodiments. The accompanying drawings are merely some exemplary representations or embodiments of the present invention. For those skilled in the art, the present invention can be applied to other similar situations based on these drawings without any further effort.

[0025] The terms “system,” “apparatus,” “unit,” and / or “module” used in this invention are to distinguish different components, elements, parts, sections, or assemblies at different levels. However, if other terms can achieve the same purpose, they may be replaced by other expressions. As illustrated in this invention, unless the context clearly indicates otherwise, words such as “a,” “an,” “an,” and / or “the” do not specifically refer to the singular and may also include the plural. Generally, the terms “comprising” and “including” only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list; the method or apparatus may also include other steps or elements.

[0026] This invention uses flowcharts to illustrate the operations performed by the system according to embodiments of the invention. It should be understood that the preceding or following operations are not necessarily performed precisely in sequence. Instead, the steps can be processed in reverse order or simultaneously. Furthermore, other operations can be added to these processes, or one or more steps can be removed from them.

[0027] For ease of reading and understanding, Table 1 below lists the definitions of relevant symbols used in the following text: symbol Unit (if any) definition - Reference coordinate system of robotic arm - Sixth axis coordinate system of robotic arm - Tool module coordinate system - Visual sensing module coordinate system - Elliptical coordinate system Degree Rotation angle of the rotary table Degree Angle between the concentrated light source and the tool axis Degree The angle between the concentrated light source and the reference point Degree Angle of intersection between the concentrated light source and V-TCP mm Distance from the center of rotation of the concentrated light source to the tool axis mm Distance along the tool axis from the center of rotation of the concentrated light source to the center point of the virtual tool mm Distance from the virtual tool center point along the tool axis to the reference plane - The center of rotation of a concentrated light source - The intersection of the tool axis and the sensing plane is at coordinates in - Coordinates of the intersection of the concentrated light source and the sensing plane - Data set of changes in the position of the point where the concentrated light source intersects the sensing plane - virtual tool center point relative to Design value -- virtual tool center point relative to Design value - The virtual tool center point relative to different calibration postures spatial location mm Length of the major axis of the ellipse mm Length of the minor axis of the ellipse Degree The major axis of the ellipse relative to tilt angle Degree Angle between the tool axis and the sensing plane

[0028] < [Light Source Assisted Robotic Arm Correction System]

[0029] Please refer to Figures 1 and 2, which are schematic diagrams of a preferred embodiment of the light source-assisted robotic arm correction system of the present invention. A tool module 10 is installed on a robotic arm 20 for correction. In this preferred embodiment, the tool module 10 is a spray gun.

[0030] A rotating platform 30 is provided between the tool module 10 and the robotic arm 20, and a concentrated light source platform 31 extends outward. A concentrated light source 32 is provided on the rotating platform 30, and one of the rotating platform rotation axes 30A of the rotating platform 30 coincides with one of the tool axes 10A of the tool module 10, so that the concentrated light source 32 can rotate around the tool axis 10A and project its light source onto a sensing plane P.

[0031] The present invention comprises an auxiliary calibration module consisting of a rotary table 30 and a concentrated light source 32, which is assembled with a tool module 10 to the robotic arm 20. The relative positions of the rotary table 30, the concentrated light source 32, the tool module 10, and the robotic arm 20 are fixed. The accurate relative relationship between the concentrated light source 32 and the tool module 10 in actual application is detected, including the distance from the rotation center point of the concentrated light source 32 to the tool axis 10A, and the distance from the rotation center point of the concentrated light source 32 to a virtual tool center point (V-TCP) along the tool axis 10A.

[0032] A vision sensing module 40 is disposed in front of the robotic arm 20. Preferably, the vision sensing module 40 is disposed on the opposite side of the robotic arm 20 relative to the sensing plane P, and an optical axis Zy of the vision sensing module 40 is perpendicular to the sensing plane P. This is used to identify the intersection of the concentrated light source 32 and the sensing plane P, and to control the robotic arm 20 to generate corresponding actions and execute the correction program of the present invention.

[0033] In this invention, the concentrated light source L used in the system is preferably laser light, and the visual sensing module 20 includes at least an optical filter and a visual sensor (not shown). Preferably, the optical filter serves as the sensing plane P in the calibration method of this invention.

[0034] < [Light Source-Assisted Robotic Arm Calibration Method]

[0035] Please refer to Figure 3. The correction method described in this invention includes the following steps:

[0036] Step 1: Install the auxiliary calibration module consisting of the rotary table 30 and the concentrated light source 32, along with the tool module 10, onto the robotic arm 20. The concentrated light source 32 is rotated to four different positions via the rotary table 30, with the corresponding angles of the rotary table 30 being... ,in, It can be at any angle, but is better. The intersection point of the tool axis 10A and the sensing plane P is determined, and then corresponding control is performed to obtain the coordinate system of the vision sensing module 20. A reference coordinate system with the robotic arm 20 The transformation relationship;

[0037] Step 2: Using the rotary table 30, rotate the concentrated light source 32 around the tool axis, and analyze the intersection point of the concentrated light source 32 and the sensing plane P. By controlling the robotic arm 20 to make the projection trajectory of the concentrated light source 32 around the rotary table 30 a perfect circle (representing that the tool axis is perpendicular to the sensing plane), the sixth axis coordinate system of the tool axis 10A (or TAO) relative to the robotic arm 20 can be obtained. The relationship between them;

[0038] Step 3: Control the robotic arm 20 to move the tool module 10 to the same position on the sensing plane P in four different postures, thereby obtaining the V-TCP relative to the sensor plane P. The coordinates of.

[0039] Step 4: The first step in the calibration process of this invention is to analyze the positional change of the concentrated light source 32 projected onto the sensing plane P through the vision sensing module 40 to determine the relative relationship between the vision sensing module 40 and the robotic arm 20. After completion, the robotic arm 20 is controlled according to the projection state of the concentrated light source 32, and finally the calibration of V-TCP and the tool axis 10A (TAO) is completed.

[0040] < [Preprocessing for Light Source-Assisted Robotic Arm Calibration Methods]

[0041] In some preferred embodiments of the present invention, before the aforementioned calibration of V-TCP and the tool axis 10A (TAO), the accurate relative relationship between the concentrated light source 32 and V-TCP must be obtained before the calibration process is performed. When installing the rotary table 30, the rotary table rotation axis 30A of the rotary table 30 must coincide with the tool axis 10A, and the concentrated light source 32 must intersect the tool axis 10A at a single point. The means by which the preceding processing steps are completed are not limited in the present invention; for example, they can be achieved through a fixture. In a preferred embodiment, the installation of the rotary table 30 can be achieved by first assembling the bushing-shaped fixture with the cylindrical reference surface of the tool module 10, and then adjusting the position of the rotary table 30 so that the rotary table 30 is coaxial with the tool axis 10A of the tool module 10, and the beam of the concentrated light source 32 intersects the tool axis 10A (TAO) at a single point, as shown in Figure 4.

[0042] After fixing the relative positions of the rotary table 30 and the tool module 10, the rotation center point of the concentrated light source 32 can then be corrected. Distance to tool axis 10A and the center point of rotation of the light source Distance to V-TCP along the tool axis 10A As shown in Figure 5. The length of a rotating arm of the concentrated light source 32 is adjusted. In this regard, the angle between the concentrated light source 32 and the tool axis 10A can be used to... Adjusted to The optical filter in the vision sensing module 20 is positioned perpendicular to the tool axis 10A as the sensing plane P. The rotary table 30 is then rotated, and the change in the position of the intersection point between the concentrated light source 32 and the sensing plane P is recorded during the rotation process, relative to the vision sensing module 20. Coordinate system dataset and the dataset The equation of the circle is obtained by using the minimum error squaring method. The radius of this circle is the distance from the rotation center of the concentrated light source 32 to the tool axis 10A. .

[0043] The rotation center point of the concentrated light source 32 Distance to V-TCP along the tool axis 10A In terms of calibration, since the V-TCP position does not have physical features, but rather extends relative to a certain reference point of the tool module 10, the calibration is performed by applying a distance from the reference point. The location, therefore, can be obtained through... Distance to the reference plane along the tool axis 10A Add the translation amount to calculate In this embodiment, the tool module 10 represents the distance of the spray gun's V-TCP relative to the spray gun's exit tip, and therefore can be adjusted... The angle at which the concentrated light source 32 intersects the reference point (the tip of the spray gun exit) is... , can be obtained Distance to the reference plane along TAO and the angle at which the concentrated light source 32 intersects with the V-TCP at a single point. As shown in Equations (1) and (2) below, and Figures 6A, 6B and 7. After obtaining the relative relationships of each component of the tool module 10, it can be installed on the robotic arm 20, and the TAO and V-TCP calibration process can be executed.

[0044] …Formula (1);

[0045] …Formula (2);

[0046] < [Virtual Center Calibration Method for Visual Sensors and Robotic Arms]

[0047] In detail, the V-TCP and TAO correction method proposed above in this invention mainly performs motion control to execute correction based on the information sensed by the vision sensing module 40. The preferred method includes first obtaining... and Only by understanding the coordinate transformation relationship can motion control commands be converted into coordinates relative to the target coordinate system. Motion control is performed using vectors; and Regarding the correction of the conversion relationship, the robotic arm 20 will be controlled to move along the respective directions. and The tool module 10 moves in a certain direction and observes the change in the position of the intersection point between TAO and the sensing plane P using the visual sensing module 40, thereby obtaining the position of the tool module 10 along the direction. and When moving in a direction relative to The movement vector is then used. and It can be obtained by considering the condition that they are perpendicular to each other in space. and The transformation matrix.

[0048] and The correction method for the conversion relationship requires the visual sensing module 40 to identify the intersection point of the tool axis 10A and the sensing plane P before the correction process can be executed. In a preferred embodiment of the present invention, the rotary table 30 controls the concentrated light source 32 to rotate around the tool axis 10A, so that the concentrated light source 32 forms a conical surface, as shown in Figures 8A and 8B. Therefore, the intersection point of the tool axis 10A and the sensing plane P can be calculated by controlling the rotary table 30 to rotate to four points and recording the intersection point of the concentrated light source 32 and the sensing plane P at each angle. A preferred embodiment is shown in Figure 11, and its detailed process is as follows:

[0049] Step 1: Adjust the angle between the concentrated light source 32 and the tool axis 10A to be between The rotating stage 30 is then adjusted to any angle so that the concentrated light source 32 faces the sensing plane P and intersects with it, and then the rotating stage 30 is adjusted to the first arbitrary angle. And record the intersection point of the concentrated light source 32 and the sensing plane P relative to... The coordinates are As shown in Figures 9A and 10A.

[0050] Step 2: Rotate the rotary table 30 to the second arbitrary angle. And record the intersection point of the concentrated light source 32 and the sensing plane P relative to... The coordinates are As shown in Figures 9B and 10B.

[0051] Step 3: Rotate the rotary table 30 to the third angle. And record the intersection point of the concentrated light source 32 and the sensing plane P relative to... The coordinates are ,make , The straight line formed Through the tool axis, as shown in Figures 9C and 10C.

[0052] Step 4: Rotate the rotary table 30 to the third angle. And record the intersection point of the concentrated light source 32 and the sensing plane P relative to... The coordinates are ,make , The straight line formed Through the tool axis, as shown in Figures 9D and 10D.

[0053] Step 5: Calculate the line and The intersection point is the point where the tool axis 10A intersects with the sensing plane P relative to... coordinates .

[0054] Finally, the result can be obtained through the above process. Then, the robotic arm 20 can be controlled to make the tool module 10 move along the three axes of the robotic arm 20. and Move and observe The changes, in order to obtain and The relationship and its process are as follows:

[0055] Step 1: The controller moves the robotic arm 20 to move the tool module 10 to obtain... The coordinates of.

[0056] Step 2: Control the robotic arm 20 to make the tool module 10 move along the robotic arm 20 Translate arbitrarily by direction and identify Changes in position, recorded relative to The position change vector of the sensing plane P is At the same time, this vector is relative to The space vector is That is, the x, y, z components of the movement vector.

[0057] Step 3: Control the robotic arm 20 to make the tool module 10 move along the robotic arm 20 Translate arbitrarily by direction and identify Changes in position, recorded relative to The position change vector of the sensing plane P is At the same time, this vector is relative to The space vector is .

[0058] Step 4: Control the robotic arm 20 to make the tool module 10 move along the robotic arm 20 Translate arbitrarily by direction and identify Changes in position, recorded relative to The position change vector of the sensing plane P is At the same time, this vector is relative to The space vector is .

[0059] Step 5: Utilize and At The conditions for mutual perpendicularity yield the following equations (3), (4), and (5).

[0060] …Formula (3);

[0061] …Equation (4);

[0062] …Formula (5).

[0063] Solving equations (3), (4), and (5) yields equations (6), (7), and (8):

[0064] …Equation (6);

[0065] …Equation (7);

[0066] …Equation (8);

[0067] From equations (6), (7), and (8), it can be seen that the two sets of solutions differ by a negative sign. Therefore, the visual sensor 40 can be used to determine the direction of the solution. and When moving, and Its length change and Based on this relationship, it can be determined whether the tool module 10 is moving toward or away from the vision sensor 40, in order to select the correct solution (such as...). When, as shown in Figure 8A, then A shorter length indicates that the tool module 10 is farther away from the sensing plane P; conversely, if... At that time, The increased length indicates that the tool module 10 is further away from the sensing plane P.

[0068] Seeking and The transformation relationship is as follows (9):

[0069] …Formula (9);

[0070] in, For relative to The movement vector, For relative to The movement vector, To transform the vector by Convert to The transformation matrix is ​​represented by equation (9). The motion control direction identified by the visual sensing module 40 can be converted into the transformation matrix using equation (9). The direction of the direction is used to make the robotic arm 20 move in the specified direction to achieve visual servo control.

[0071] < [Tool Shaft Calibration Process]

[0072] Next, in the calibration process of the tool shaft 10A, the preferred embodiment of the present invention obtains... and After the conversion relationship is completed, TAO correction can be performed. Regarding TAO correction, the method provided by this invention mainly involves controlling the robotic arm 20 to make the intersection of the conical surface formed by the concentrated light source 32 and the sensing plane P form a perfect circle, meaning the tool axis 10A is perpendicular to the sensing plane P. This allows the TAO to be calculated relative to the sensing plane P. The direction. A preferred embodiment of its process is as follows:

[0073] First, Adjust to any angle and control the robotic arm 20 so that the intersection curve of the conical surface of the concentrated light source 32 and the sensing plane P is within the field of view of the visual sensing module 40.

[0074] Next, control the rotary table 30 to make Rotate from 0° to 360° and identify the position change curve of the concentrated light source 32 projected onto the sensing plane P, and obtain the intersection point data set. As shown in Figure 12.

[0075] Then, the dataset of the position changes of the points where the concentrated light source 32 intersects with the sensing plane P. The ellipse equation is obtained by fitting the minimum error data, as shown in Figures 13A and 13B and Equation 10.

[0076] …Equation (10); where, These are the coefficients of the equation for an ellipse.

[0077] Next, the length of the major axis of the ellipse is obtained by using the coefficients of the ellipse equation. Length of the minor axis of the ellipse The major axis of the ellipse is relative to Inclination angle As shown in equations (11) to (13):

[0078] Length of the major axis of the ellipse …Formula (11);

[0079] Length of the minor axis of the ellipse …Equation (12);

[0080] The major axis of the ellipse relative to Inclination angle …Equation (13);

[0081] If the coefficients of the elliptic equation are... and , then represents the tilt angle. .

[0082] Next, obtain the tilt angle. Then, the robotic arm 20 can be controlled to rotate the tool module 10 until the tool axis 10A (TAO) is perpendicular to the sensing plane P.

[0083] Step 1: Establish an elliptical coordinate system With the major axis of the ellipse as The direction perpendicular to the sensing plane is The origin is taken as the center of the ellipse. The angle between the tool axis 10A and the sensing plane P is obtained using the vector loop equation. As shown in Figure 14 and equations (14) and (15):

[0084] …Equation (14);

[0085] …Equation (15);

[0086] By rewriting equations (14) and (15) as scalar equations and solving them, we can obtain the answer. , , and , as shown in equations (16) to (19). …Equation (16); …Equation (17); …Equation (18);

[0087] …Equation (19);

[0088] The angle between the tool axis 10A and the sensing plane P As in equation (20), where and the angle between the tool axis 10A and the sensing plane P There are two sets of branch solutions, which can be obtained from... and The correct solution for determining the length is as follows: At that time, This indicates that the tool axis 10A points to the upper left.

[0089] …Equation (20);

[0090] Relative to the minor axis of the ellipse direction Using equation (9), we can convert the minor axis of the ellipse relative to... direction And control the robotic arm 20 so that the center point of the virtual tool is relative to... Design value The position is fixed, and the position is relative to the minor axis of the ellipse. direction Rotate the angle between the tool axis 10A and the sensing plane P. The center point of the virtual tool is relative to Design value , and The V-TCP position design values ​​are respectively relative to and coordinates, It can be obtained through CAD models. To change the coordinates from Switch to The transformation matrix can be obtained through the DH parameters and the DH transformation matrix of the robotic arm 20:

[0091] 1. If the intersection line after rotation is an ellipse, and the length of the major axis of the ellipse is greater than the length before rotation, then control the robotic arm 20 to return to the state before rotation, and rotate it around the minor axis of the ellipse relative to... The opposite direction Rotate the angle between the tool axis 10A and the sensing plane P. And then determine the type of intersection line again.

[0092] 2. If the intersection line after rotation is an ellipse, and the length of the major axis of the ellipse is less than the length before rotation, the robot arm 20 may not be able to perform the action accurately due to poor absolute accuracy: recalculate the ellipse information using equations (10) to (13) and (16) to (20), and control the robot arm 20 to revolve around the center point of the virtual tool relative to the center point of the virtual tool. Design value Rotate and repeat this process until the intersection line approaches a perfect circle, which means that the tool axis 10A is perpendicular to the sensing plane P.

[0093] 3. Calculate the tool shaft 10A relative to... The direction is as shown in the following formulas (21) and (22):

[0094] …Equation (21); …Equation (22);

[0095] Since the tool axis 10A is perpendicular to the sensing plane P, the Z-axis direction of the tool axis 10A... The Z-axis direction of the visual sensing module 40 Parallel and opposite, therefore Change to The direction indicated is ,in and They are respectively and Compared to The direction, for Compared to The direction, To change the direction Switch to Matrix To change the direction Switch to The matrix.

[0096] Obtain and Compared to direction Further definition is needed. and Compared to direction and and Compared to direction Only then can the 10-coordinate system of this tool module be fully defined. Compared to The location. For tools of the V-TCP type in this virtual tool center, since the point of action is located outside the tool module 10 itself, it is usually only necessary to make... , and They need to be perpendicular to each other; when the tool axis 10A is perpendicular to the sensing plane P, it can be directly used. Compared to direction and Compared to The opposite direction Define the coordinate system of the tool module 10. , Direction, as shown in equations (23) and (24): …Equation (23); …Equation (24);

[0097] The TAO correction can be completed by using equation (25), which can be used to correct any relative to the TAO. The coordinates were changed to express:

[0098] …Formula (25).

[0099] < [Virtual Tool Center Correction]>

[0100] In the calibration of the Virtual Tool Center (V-TCP) of this invention, a preferred embodiment uses information from the vision sensing module 40 to control the movement of the robotic arm 20, positioning the tool module 10 in at least one posture (e.g., four different postures in this embodiment) to bring the V-TCP to the same position in space. The combination of angles along each axis of the robotic arm 20 is recorded, and the coordinates of the V-TCP can be obtained using kinematic equations. A preferred embodiment of the detailed calibration process includes the following steps:

[0101] First, adjust the angle between the concentrated light source 32 and the tool axis 10A to... And keep the tool axis 10A perpendicular to the sensing plane P, then analyze the intersection position. Location.

[0102] Step 1: As shown in Figure 15, The conical light source 32 may be located on the same side or opposite side of the tool module 10. To determine... In relation to the conical relationship of the concentrated light source 32, the tool module 10 can be moved along the direction of the robotic arm 20 by controlling the robotic arm 20. Directional movement: If the tool module 10 moves along... When moving, and The distance decreases as the movement progresses, which means The 32-cone light source is located on the same side; conversely, if it is on the opposite side, then... The conical light source 32, located on the opposite side, allows the tool module 10 to be moved along the robotic arm 20 by means of the control. Move in direction until The concentrator 32, located on the same side, is used for the following step 2.

[0103] Step 2: Use the aforementioned equation (17) to calculate the distance between V-TCP and the sensing plane P. And control the robotic arm 20 to make the tool module 10 move along move The distance is such that the intersection point of the concentrated light source 32 and the sensing plane P can be determined. and "Overlap" means that V-TCP overlaps with the sensing plane P.

[0104] Step 3: Record the overlap point relative to coordinates By measuring the angles of each axis of the robotic arm, the perpendicularity of the tool axis 10A to the sensing plane P (the first set of attitude angles) can be obtained, and V-TCP can be made to reach... The information, its first set of attitude angles Roll-Pitch-Yaw is The robotic arm has 20 axes with angles of [missing information]. ,in When the first set of postures is reached, V-TCP arrives. The 20th robotic arm Axis angle, let .

[0105] Step 4: Generate the orientation of the tool module 10 during three additional sets of calibrations; the orientation of the tool module 10 during these four sets of calibrations can be arbitrarily defined by the user, but the defined orientation of the tool module 10 should cover the complete orientation workspace of the tool module 10 as much as possible. A preferred embodiment of the present invention is illustrated below:

[0106] A. The steps for generating the second set of attitude angles include:

[0107] i. Position the tool module 10 at the first set of attitude angles. As the starting point, and by controlling the robotic arm 20 to make the virtual tool center point V-TCP relative to... Design value Fixed position, around Direction Rotation Angle To provide a larger angle variation, among which The angle should be increased as much as possible without exceeding the range of motion of the 20 axes of the robotic arm.

[0108] ii. Record the orientation of the tool module 10 relative to... Roll-Pitch-Yaw is the second set of postures. ,in , , .

[0109] B. Next, the third set of attitude angles is generated, including the following steps:

[0110] i. Using the first posture as the starting point, control the robotic arm 20 to... Fixed position and around Direction rotation ,in The angle should be increased as much as possible without exceeding the range of motion of the 20 axes of the robotic arm.

[0111] ii. Record the orientation of the tool module 10 relative to... Roll-Pitch-Yaw is the third set of poses. ,in , , .

[0112] C. Generate the fourth set of attitude angles, the steps of which include:

[0113] i. Generate azimuth increments using a random number generator. And control the robotic arm 20 to make After the position is fixed, the attitude of the tool module 10 is changed to... .

[0114] ii. Record the orientation of the tool module 10 relative to... Roll-Pitch-Yaw is the fourth pose. .

[0115] Step 5: Control the movement of the robotic arm 20, and position the tool module 10 in different postures so that the V-TCP reaches the same position in space. And record the current angles of each axis of the robotic arm 20. .

[0116] A. Control the robotic arm 20 to... The position is fixed and the attitude of the tool module 10 is changed to an attitude angle. The intersection point of the tool axis 10A and the sensing plane P is obtained at... coordinates in Location.

[0117] B. Confirmation The relationship with the 32-cone concentrated light source, if If located on the opposite side of the cone, then control the robotic arm 20 to... The 32-cone light source is located on the same side.

[0118] C. Obtaining relative to Vector and through the aforementioned formula (9) Convert to relative Vector To control the robotic arm 20 so that the tool axis 10A passes through .

[0119] D. Calculate the moving length using equation (17), and control the robotic arm 20 to make the tool module 10 move along... directional movement length , enabling V-TCP and coincide.

[0120] E. Control the rotary platform to rotate the laser light source around the tool axis 10A, and obtain the concentrated light source 32. The data set of intersection points of the sensing plane P :

[0121] i. If the intersection data set All points approach This means that V-TCP and If they overlap, the angle information of each of the 20 axes of the robotic arm will be recorded. ,in For the tool module 10, the first Group gestures enable V-TCP to arrive The 20th robotic arm Axis angle.

[0122] ii. Conversely, if the absolute precision of the robotic arm 20 is poor, it may be unable to accurately move the V-TCP to the designated position. In this case, return to step 5B and gradually correct the V-TCP to approach the correct position. .

[0123] F. If a movement error occurs during any step of this process (such as exceeding the movement range limit of the robotic arm 20), return to step 4 to readjust the movement. Group attitude angles.

[0124] Step 6: Next, if , then let Then return to step 5 above to obtain the next set of tool module 10 attitudes, so that V-TCP and Combination of overlapping joint angles; if Once the data collection of the angles of each axis of the 4 sets of the tool modules at the same position in space is completed, TCP calculation can begin.

[0125] Once four or more different combinations of the tool module 10's postures at the same position in space are obtained, the V-TCP relative to the mechanical arm 20 can be calculated using kinematic equations. The coordinates. According to the kinematic equations of the robotic arm 20, the V-TCP can be relative to... The coordinates are represented by the following formula (26):

[0126] …Equation (26);

[0127] in For DH (Denavit–Hartenberg) matrix, For the 20th time this robotic arm The tool module 10 enables V-TCP to... The overlapping number DH parameters of the axis, V-TCP relative to The x, y, and z coordinates are respectively , For the coincidence point relative to The coordinates of.

[0128] The angle information of each axis of the tool module 10 in each posture can be used to obtain three linear equations through equation (26). Therefore, 12 equations can be obtained using the angle information of each axis of the four tool modules 10 in each posture, and the coordinates of TCP can be obtained: Substitute the combination of the angles of each axis of the robotic arm 20 in the four tool modules 10 in each posture into equation (26), and after simplification, equations (27) and (28) can be obtained:

[0129] …Equation (27);

[0130] …Equation (28);

[0131] in , for The pseudo-inverse matrix. Following this process, V-TCP can be obtained relative to... The coordinates are used to complete the V-TCP correction.

[0132] During the calibration process, in the preferred embodiment described above, the tool module generates 12 equations through 4 sets of 10 postures to solve for 6 variables. However, in other possible embodiments, the number of equations increases with the number of points, which helps to distribute the error more evenly, thereby obtaining a more accurate calibration result of the present invention.

[0133] This invention uses flowcharts to illustrate the operations performed by the system according to embodiments of the invention. It should be understood that the preceding or following operations are not necessarily performed precisely in sequence. Instead, the steps can be processed in reverse order or simultaneously. Furthermore, other operations can be added to these processes, or one or more steps can be removed from them.

[0134] In some embodiments, numbers describing the quantity of components and attributes are used. It should be understood that such numbers used in the description of embodiments are modified in some examples with the terms "approximately," "approximately," or "generally." Unless otherwise stated, "approximately," "approximately," or "generally" indicates that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may be changed depending on the characteristics required by individual embodiments. In some embodiments, numerical parameters should take into account specified significant digits and employ a general method of digit reservation. Although the numerical ranges and parameters used to confirm their breadth of range in some embodiments of the invention are approximate values, in specific embodiments, such values ​​are set as precisely as feasible.

[0135] Finally, it should be understood that the embodiments described in this invention are merely illustrative of the principles of the invention. Other modifications may also fall within the scope of this invention. Therefore, alternative configurations of the embodiments of this invention are considered as examples and not limitations, and are regarded as consistent with the teachings of this invention. Accordingly, the embodiments of this invention are not limited to those explicitly described and illustrated herein.

[0136] 10: Tool Module V-TCP: The Central Point of Virtual Tools 10A: (TAO) Tool Shaft 20: Robotic Arm 30: Rotary table 31: Concentrated Light Source Stage 32: Concentrated light source 30A: Rotary table rotation shaft 40: Vision Sensor The distance from the rotation center of the concentrated light source to the tool axis. The distance along the tool axis from the center of rotation of the concentrated light source to the center point of the virtual tool. The distance from the virtual tool's center point along the tool axis to the reference plane. : Distance extended relative to a certain reference point of the tool module : Vector from the intersection of the tool axis and the plane to the lower side of the cone : Vector from the intersection of the tool axis and the plane to the upper side of the cone Vector from the intersection of the tool axis and the plane to the center point of the virtual tool Vector from the intersection of the upper side of the cone and the plane to the center point of the virtual tool Vector from the intersection of the lower side of the cone and the plane to the center point of the virtual tool P: Sensing plane The center of rotation of a concentrated light source Intersection of sensing planes Coordinates of the intersection point of the concentrated light source and the sensing plane When the rotary table is adjusted to the first arbitrary angle, the intersection of the concentrated light source and the sensing plane is relative to... coordinates When the rotary table is adjusted to the second arbitrary angle, the intersection of the concentrated light source and the sensing plane is relative to... coordinates When the rotary table is adjusted to the third arbitrary angle, the intersection of the concentrated light source and the sensing plane is relative to... coordinates When the rotary table is adjusted to the fourth arbitrary angle, the intersection of the concentrated light source and the sensing plane is relative to... coordinates : Coordinates of the intersection point of the tool axis and the sensing plane The intersection of the tool axis and the sensing plane is at coordinates in The virtual tool's center point coincides with the sensing plane's point relative to... coordinates Compared to movement vector Tool axis X-axis direction : Perpendicular to the sensing plane direction :X-axis direction of visual sensing module : Major axis direction of the ellipse : Y-axis direction of visual sensing module Tool axis Z-axis direction :Z-axis direction of visual sensing module Zy: Optical axis Angle between the concentrated light source and the tool axis The angle between the upper side of the cone and the normal vector of the plane. Angle between the tool axis and the sensing plane

Claims

1. A method for calibrating a light source-assisted robotic arm, comprising the following steps: Step 1: Installing an auxiliary calibration module and a tool module, consisting of a rotary table and a concentrated light source, onto a robotic arm, and placing a vision sensing module adjacent to the robotic arm; rotating the concentrated light source to four different positions using the rotary table to obtain the intersection point of a tool axis of the tool module and a sensing plane, and then controlling the robotic arm accordingly to obtain the transformation relationship between the coordinate system of the vision sensing module and a reference coordinate system of the robotic arm; Step 2: Using the rotary table to rotate the concentrated light source around the tool axis, and analyzing the intersection point of the concentrated light source and the sensing plane, and by controlling the robotic arm to make the projection trajectory of the concentrated light source around the rotary table a perfect circle, obtaining the sixth axis coordinate system relationship of the tool axis relative to the robotic arm; Step 3: Control the robotic arm to move a virtual tool center of the tool module to the same position on the sensing plane in at least one corresponding posture, obtain the coordinates of the virtual tool center relative to the sixth axis coordinate system, and complete the correction of the virtual tool center and the tool axis.

2. The light source-assisted robotic arm calibration method as described in claim 1, wherein: before calibrating the virtual tool center and the tool axis, the accurate relative relationship between the concentrated light source and the virtual tool center is obtained before executing the calibration process.

3. The light source-assisted robotic arm calibration method as described in claim 1 or 2, wherein: when the rotary table is installed, one of the rotary table's rotation axes must coincide with the tool axis, and the concentrated light source must intersect the tool axis at a single point.

4. The light source-assisted robotic arm calibration method as described in claim 1 or 2, wherein: after fixing the relative position of the rotary table and the tool module, the distance from the rotation center point of the concentrated light source to the tool axis, and the distance from the rotation center point of the light source to the virtual tool center along the tool axis are then calibrated.

5. The light source-assisted robotic arm correction method as described in claim 1 or 2, wherein: in correcting the length of a rotating arm system for the concentrated light source, the angle between the concentrated light source and the tool axis is adjusted to 0, and the vision sensing module is mounted at a position perpendicular to the tool axis as the sensing plane. Then, the rotating table is controlled to rotate, and the change in the position of the intersection point of the concentrated light source and the sensing plane during the rotation process is recorded. The data set relative to the coordinate system of the vision sensing module is recorded, and the equation of the circle and the radius of the circle are obtained from the data set using the minimum error method.

6. The light source-assisted robotic arm correction method as described in claim 5, wherein: the correction system for the distance from the rotation center point of the concentrated light source to the center of the virtual tool along the tool axis is calculated by obtaining the distance from the rotation center point of the light source to the reference surface along the tool axis, and adding the translation amount.

7. The light source-assisted robotic arm correction method as described in claim 1 or 2, wherein: the virtual tool center and the tool axis correction method first requires obtaining the coordinate transformation relationship between the visual sensing module coordinate system and the robotic arm reference coordinate system, and converting motion control commands into vectors relative to the robotic arm reference coordinate system for motion control; the correction system for the transformation relationship between the visual sensing module coordinate system and the robotic arm reference coordinate system will obtain the movement vector of the tool module relative to the visual sensing module coordinate system when it moves along the direction of the robotic arm reference coordinate system by controlling the robotic arm to move along the direction of the robotic arm reference coordinate system, and using the visual sensing module to observe the change in the position of the intersection point of the tool axis and the sensing plane, and finally using the condition that the robotic arm reference coordinate systems are mutually perpendicular in space to obtain the transformation matrix between the visual sensing module coordinate system and the robotic arm reference coordinate system.

8. The light source-assisted robotic arm correction method as described in claim 1 or 2, wherein: the correction of the conversion relationship between the coordinate system of the vision sensing module and the reference coordinate system of the robotic arm is performed by identifying the intersection point of the tool axis and the sensing plane through the vision sensing module, and the concentrated light source is controlled to rotate around the tool axis through the rotary table so that the concentrated light source forms a conical surface; the intersection point of the tool axis and the sensing plane is calculated by controlling the rotary table to rotate to four different angles and recording the intersection point of the concentrated light source and the sensing plane at each angle.

9. The light source-assisted robotic arm correction method as described in claim 1 or 2, wherein: through information from the visual sensing module, the movement of the robotic arm is controlled to position the tool module in at least one posture so that the virtual tool center reaches the same position in space, and the combination of the angles of each axis of the robotic arm is recorded and the coordinates of the virtual tool center are obtained through kinematic equations.

10. A light source-assisted robotic arm correction system, comprising: a robotic arm with a tool module mounted thereon; an auxiliary correction module comprising: a rotary table, a concentrated light source, and a vision sensing module; the rotary table is disposed between the tool module and the robotic arm, and a concentrated light source platform extends outward therefrom, the concentrated light source is disposed on the rotary table, the rotary table, the concentrated light source, the tool module, and the robotic arm are fixed in relative positions, and one of the rotary table's rotation axes coincides with one of the tool axes of the tool module, so that the concentrated light source can rotate around the tool axis and project its light source onto a sensing plane; and the vision sensing module is disposed on the opposite side of the robotic arm relative to the sensing plane, one optical axis of the vision sensing module is perpendicular to the sensing plane, for identifying the intersection position of the concentrated light source and the sensing plane, and controlling the robotic arm to generate corresponding actions and execute the light source-assisted robotic arm correction method as described in any one of claims 1 to 10.

11. The light source-assisted robotic arm correction system as claimed in claim 10, wherein: the concentrated light source comprises laser light; and the vision sensing module comprises at least an optical filter and a vision sensor.

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