Contact type positioning method for tail end of mechanical arm

Abstract

The invention discloses a mechanical arm tail end contact type positioning method, and belongs to the technical field of mechanical arm positioning recognition. The method comprises the following steps: dividing a target sampling area, controlling a mechanical arm to autonomously move to poll a target sampling point, approaching a to-be-operated object, and judging whether the mechanical arm is in contact with the to-be-operated object through a tail end force sensor so as to mark the position and depth information of the to-be-operated object in the target area; and after polling is completed, a position area range of the to-be-operated object can be formed, so that positioning of the to-be-operated object is completed. According to the method, the contour and depth information of the to-be-operated object can be accurately obtained under multiple working conditions that the area information of the to-be-operated object is difficult to obtain in a complex environment, no visual implementation condition exists and less information of the to-be-operated object is known.

Description

Technical Field

[0001] The invention relates to a contact positioning method for a mechanical arm end, belonging to the technical field of mechanical arm positioning and identification. Background Art

[0002] Robotic arms are widely used in industrial production and special operations. They are usually used to perform flexible posture control through their multi-degree-of-freedom characteristics to complete a series of fine assembly operations. In this process, the robot needs to locate and identify the object being operated before further operations. Common robot positioning and identification technologies include: (1) obtaining the target position by fixed measurement or dragging teaching. This process requires human participation and requires the working area to be simple and friendly. Each time a component is moved or replaced, it needs to be re-measured, which makes the process more complicated. (2) Through vision, it is necessary to install a camera and use a computer for image processing. While increasing costs, the image recognition and coordinate conversion algorithms are also more complex, and the shape information or feature identification of the target object needs to be known for visual training and recognition. In some work scenarios where the environment is complex and vision is difficult to work, such as underwater, mine tunnels, underground, etc., when it is necessary to locate, identify and operate the controlled object, it is necessary to invent a robot positioning technology that is more autonomous and does not rely on vision and direct operator participation.

[0003] Chinese patent CN112248860A discloses a method that uses an ultrasonic transmitting probe on the vehicle side and an ultrasonic receiving probe on the charging robot arm side. After the robot arm moves to the working area, the kinematic parameters of the robot arm are calculated according to the time when the ultrasonic probe receives the detection signal, and the robot arm is controlled to move to the positioning area, thereby ensuring the docking of the automatic charging robot arm with the vehicle-mounted connector. This method uses ultrasonic positioning to locate the object to be operated, but requires that the object to be operated is equipped with an ultrasonic transmitting probe and its state is known. It is difficult to implement in complex environments where the information of the object to be operated is unclear.

[0004] Chinese patent CN118078220A discloses a human spine positioning method based on robot arm force perception, which uses a depth camera to perform three-dimensional reconstruction and segmentation of the human back (the object to be operated), and then uses a 3D key point detection network to roughly locate the point cloud model, thereby planning the initial motion trajectory, controlling the robot arm movement to collect force sensor information, and thus obtaining the accurate spinal position. This method is applied to medical detection scenarios to simulate human hand palpation, but its prerequisite is still the visual recognition and modeling method based on the depth camera, which is difficult to use in scenarios that are not suitable for visual implementation. Summary of the invention

[0005] The technical problem solved by the present invention is: to overcome the deficiencies of the prior art and propose a contact positioning method for the end of a robot arm to solve the problem of autonomous positioning of the end of a robot arm in the absence of vision, direct participation of personnel and less information about the object to be operated.

[0006] The technical solution of the present invention is:

[0007] A contact positioning method for the end of a robotic arm, comprising:

[0008] The base of the robot is taken as the origin, the reachable working space of the robot in space is taken as the working boundary, the direction in which the robot approaches the object to be operated is taken as the normal, and the plane perpendicular to the normal is taken as the plane where the object to be operated is located;

[0009] The target sampling area for the end movement of the robot arm is divided from the plane direction dimension where the object to be operated is located, combined with the working boundary of the robot arm; the target sampling area is divided into several blocks in the form of a grid network and numbered as target sampling points, and the sampling points are assigned values ​​in turn, and the values ​​are used to indicate whether the object to be operated is touched;

[0010] The robot arm autonomously polls each sampling point in the order of sampling points, and records whether the end of the robot arm touches the target when it is at each sampling point and the stroke of the robot arm along the normal direction when it touches the target;

[0011] According to the information of all the recorded sampling points, the position information of the object to be operated is obtained.

[0012] Furthermore, the robot arm autonomously polls each sampling point in the order of sampling points, and the specific method is as follows:

[0013] Move the robot arm to the location of the first sampling point and perform contact sampling operation: feed the robot arm toward the object to be operated in the normal direction; during the movement, determine whether the end is in contact with the object to be operated based on the contact force collected by the robot arm; if it is judged to be in contact, the current sampling point is assigned a value of 1, and the stroke of the current robot arm in the normal direction is recorded, and the robot arm returns; if it is still judged to be not in contact until the end movement stroke exceeds the maximum movement depth of the robot arm, the current sampling point is assigned a value of 0, and the robot arm returns;

[0014] After the robot arm returns to the starting position, it moves to the location of the next sampling point and performs the contact sampling operation again; this polling is repeated until the contact sampling operation is completed for all sampling points.

[0015] Furthermore, during the movement, the contact force collected by the robot arm is used to determine whether the end is in contact with the object to be operated, specifically:

[0016] The force sensor module inside the robotic arm monitors the force information collected by the force sensor at the end of the robotic arm in real time, and filters and compensates the collected force information;

[0017] The central controller in the robotic arm makes a judgment based on the filtered and compensated force information: if the force information is greater than the set contact force threshold, it is determined that the end of the robotic arm is in contact with the object to be operated at the current sampling point and at the current moment; otherwise, it is determined that the end of the robotic arm is not in contact with the object to be operated at the current sampling point and at the current moment.

[0018] Furthermore, according to the information of all the sampling points obtained, the position information of the object to be operated is obtained, and the specific method is as follows:

[0019] All sampling point information obtained, including the location information of the sampling point, the state value of whether it is in contact, and the movement distance of the robot arm in the normal direction;

[0020] Only the sampling point information corresponding to the contact state value of 1 is retained; the contour information and depth information of the object to be operated are obtained by integrating the movement stroke of the robot arm in the normal direction corresponding to each sampling point, and the position area range of the object to be operated is formed.

[0021] Furthermore, within the boundary of the target area, the plane target area is divided into several areas in the form of a grid network and labeled. The labeling method adopts the matrix numbering form, which is denoted by x ij , which represents the area located in the i-th horizontal direction and the j-th vertical direction in the divided plane target area.

[0022] Furthermore, within the boundary of the target area, the plane target area is divided into several areas in the form of a grid network, each area is α×α in size, where α satisfies:

[0023] ε robot ≤α≤ε goal

[0024] In the formula, ε robot Represents the positioning accuracy of the robot arm, ε goal Represents the expected positioning accuracy of the object to be operated.

[0025] Furthermore, the robotic arm system includes a central controller, a robotic arm controller, a force sensor acquisition module, and a force signal processing module;

[0026] The central controller sends motion instructions to the robot arm controller;

[0027] The robot controller converts the motion instructions into the robot joint space and controls the robot to achieve motion;

[0028] The force sensor acquisition module is located at the end of the robotic arm and monitors the force information collected by the force sensor at the end of the robotic arm in real time;

[0029] The force signal processing module filters and compensates the collected force information and sends the processed information to the central controller.

[0030] The advantages of the present invention compared with the prior art are:

[0031] (1) The target sampling area division method of the present invention is based on the robot arm workspace, and the reachable area of ​​the robot arm itself is used as the working boundary, so that information acquisition is easier and more accurate, and the problem of being unable to determine the working area due to difficulty in obtaining information about the area where the object to be operated is located when working in a complex environment is avoided;

[0032] (2) The present invention divides the target sampling area in the form of a grid network as the target sampling point. The grid size is selected according to the positioning accuracy of the robot arm and the desired accuracy of the object to be operated. This division method can reduce data processing time and improve measurement efficiency while ensuring the accuracy of the measurement results.

[0033] (3) The present invention controls the robot arm to move and poll the target sampling points in a grid form, and can traverse the target area in the most efficient and standardized manner to obtain the sampling results of each sampling point.

[0034] (4) The present invention uses the end torque sensor provided on the robot arm itself as the acquisition and measurement device, avoiding the use of sensing and measurement devices such as cameras and lasers that have high requirements on the environment or require operations on the object to be operated, and is easy to implement.

[0035] (5) The present invention uses 0 or 1 to mark the state of whether the end of the robot arm is in contact with the object to be operated, and records the movement depth when in contact. This recording method is simple to describe the sampling state of the target sampling point and can express the orientation information of the target sampling point.

[0036] (6) The present invention filters and compensates the collected force information through the force sensor module. The force sensor has large instantaneous numerical disturbance and may have temperature drift. After filtering and compensation, smoother and more realistic force collection information is obtained;

[0037] (7) Based on the sample values ​​of all the recorded sample points and the motion stroke information when contact occurs, the present invention can establish the position area range of the object to be operated from the two dimensions of plane direction and normal direction, and can obtain the contour and depth information of the object to be operated, which can more accurately describe the shape contour and position of the object to be operated, and is also conducive to the realization of subsequent operation tasks. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0039] Figure 1 This is a flow chart of the contact positioning method of the end of a robot arm according to an embodiment of the present invention;

[0040] Figure 2 This is a schematic diagram of the composition of the contact positioning module at the end of the robot arm according to an embodiment of the present invention;

[0041] Figure 3 Schematic diagram of a contact positioning method for a robot end of an embodiment of the present invention;

[0042] Figure 4 A schematic diagram of the normal direction and the plane direction of an embodiment of the present invention;

[0043] Figure 5 This is a schematic diagram of a target area plane division method according to an embodiment of the present invention;

[0044] Figure 6 Schematic diagram of force contact positioning marking of a target area according to an embodiment of the present invention. DETAILED DESCRIPTION

[0045] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0046] The present invention proposes a contact positioning method for the end of a manipulator. By dividing the target area, the manipulator is controlled to autonomously move and poll the target sampling point, approach the object to be operated, and determine whether it is in contact with the target through the end force sensor, thereby marking the target position and depth information in the target area. When the polling is completed, the position area range of the object to be operated can be formed, thereby completing the positioning of the object to be operated. The relationship between the various operation modules involved in the method is as follows: Figure 2As shown. The central controller sends motion instructions to the robot controller, which contains functional modules such as robot motion planning, interpolator, and kinematics. It is responsible for converting the motion instructions issued by the central controller to the robot joint space and controlling the robot to achieve movement. A force sensor acquisition module is provided at the end of the robot to monitor the force information collected by the force sensor at the end of the robot in real time. The force signal processing module is responsible for filtering and compensating the collected force information and sending the processed smoother and more realistic information to the central controller.

[0047] This method is Figure 1 As shown, specifically including:

[0048] Step 1: Determine the target area and direction

[0049] When there is little information about the area where the object to be operated is located, it is difficult to directly determine the target area from the range where the object to be operated is located. The base of the robot is taken as the origin, and the reachable working space of the robot in space is taken as the target area. The direction of the target area is also specified, with the direction of the robot approaching the target as the normal, and the plane perpendicular to the normal as the plane direction where the object to be operated is located, such as Figure 3 shown.

[0050] Step 2: Target area division

[0051] According to the target area and direction determined in step 1, the plane direction dimension of the object to be operated is divided as the target area for the end movement of the robot. Within the boundary of the target area, the plane target area is divided into several small areas in the form of a grid network, and the size of each grid is α×α (unit: mm), where the value of α is selected by the designer according to the positioning accuracy level of the robot and the expected target positioning accuracy.

[0052] ε robot ≤α≤ε goal

[0053] In the formula, ε robot Represents the positioning accuracy of the robot arm (unit: mm), ε goal Represents the expected positioning accuracy of the object to be operated (unit: mm).

[0054] Number each area as the target sampling point in the form of matrix numbering, denoted by x 11 、x 12 ,……,x mn (m and n represent the maximum number of regions divided horizontally and vertically in the plane, respectively), such as Figure 5 shown.

[0055] x 11 、x 12 , …, xmn ∈C plane

[0056] In the formula, C plane The extent of the plane direction representing the robot's workspace.

[0057] Each grid target sampling point contains a value to indicate whether there is subsequent contact, where 0 represents no contact and 1 represents contact. The values ​​of the target sampling points in the grid area are initialized to 0.

[0058] like Figure 4 shown.

[0059]

[0060] The division and values ​​of the target area and sampling points are stored in the central controller.

[0061] Step 3: The robot moves to the starting position of the sampling point.

[0062] From the sampling point x 11 At the beginning, the central controller sends a translation motion command to the robot controller. The robot controller contains functional modules such as robot motion planning, interpolator, and kinematics. It is responsible for converting the motion command sent by the central controller to the robot joint space and controlling the robot to achieve motion. The end of the robot moves in the plane direction to the sampling point x 11 Location, such as Figure 3 shown.

[0063] Step 4: The end of the robot arm feeds to perform contact sampling.

[0064] After the end of the robot arm moves to the sampling point in the previous step, the central controller sends a feed motion instruction to the robot arm controller, and the controller controls the robot arm to move toward the target along the normal direction of the target area, such as Figure 4 As shown, during this process, the force sensor acquisition module monitors the force information collected by the force sensor at the end of the robotic arm in real time. The force sensor module is responsible for filtering and compensating the collected force information, and sending the processed smoother and more real information to the central controller.

[0065] The central controller judges based on the contact force information collected by the force sensor at the end of the robot arm: (1) When the force information collected by the force sensor is greater than the set contact force threshold F th When the end is judged to be in contact with the target object, the target sampling point is marked as in contact, and the value of the corresponding grid area is marked as 1. Figure 6 As shown, the distance of the robot arm moving along the normal direction is recorded, which is d ij, control the robot to return; when the end motion exceeds the maximum motion depth of the robot and the contact force information is still not collected, the target sampling point is marked as no contact, the value of the corresponding grid area is marked as 0, and the robot is controlled to return. The maximum motion depth of the robot is d max It is selected by the designer based on the reachable working space of the robot arm.

[0066] F ij ≥F th When x ij =1,d ij =d mov

[0067] F ij <F th And d mov >d max When x ij =0,d ij =0

[0068] In the formula, F ij represents the contact force collected at the sampling point (i, j), F th Represents the set contact force threshold, x ij Represents the numerical state of whether the sampling point (i, j) touches the object to be operated, d mov Represents the stroke of the robot arm along the normal motion, d ij Represents the depth of contact with the object to be operated, d max Represents the maximum depth of the robot arm movement. 0 <i<m,0<j<n。

[0069] Step 5: Complete the target sampling point polling.

[0070] When the robot arm detects the last sampling point and returns to the starting position, the central controller sends a translation motion command to control the robot arm to move to the next target sampling point, repeats steps 3 and 4, starts the detection of the next sampling target point, and stores the collected results in the central controller. The sampling process ends when the polling detection of all target sampling points is completed.

[0071] Step 6: Count the sampling results and generate target location information.

[0072] After sampling, the central controller collects data from all sampling points. Each sampling point contains three pieces of information: (1) First, the sampling point number i, j represents the position of the sampling point in the plane direction of the workspace, which can be represented in the form of coordinates. (2) Whether the sampling point is in contact with the object to be operated ij is 0 or 1, (3) the distance d of the robot arm in the normal direction ij , when the contact state is 1, dij The value of is not 0.

[0073] After the sampling is completed, the position information of the object to be operated can be expressed according to the information of all the sampling points obtained, among which only the sampling point contact state is retained as 1, that is, the sampling point (i, j) with contact is the valid sampling point, and the motion stroke d at the comprehensive valid sampling point is ij , the contour information and depth information of the object to be operated can be obtained, and then the position area range of the object to be operated can be established, so as to realize the positioning of the robot arm on the object to be operated.

[0074] After the above 6 steps, the end contact positioning method described in the present invention can be completed. Without the use of visual participation and direct participation of personnel, the robot arm's own workspace is divided into regions, and the end force sensor is used to perform contact polling detection on the target in the divided grid target area, thereby realizing the problem of autonomous positioning of the robot arm in the space of the object to be operated. The positioning result obtained contains the contour and depth information of the object to be operated, which helps the robot arm to further operate it.

[0075] The present invention proposes a contact positioning method for the end of a robotic arm. This method has no visual implementation conditions and has little knowledge of the target information. It does not require other operations on the target and human participation. By using the end force sensing module provided by the robotic arm itself and the grid-shaped target area divided by the robotic arm's own working space, the robotic arm movement is controlled to perform polling contact measurement on the target sampling points, thereby obtaining a series of contact information and depth information of the object to be operated, thereby describing the shape contour and position of the object to be operated, and solving the problem of obtaining the target position without vision and direct human participation.

[0076] The above-described embodiments are only preferred specific implementations of the present invention. Common changes and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A contact positioning method for the end of a robot arm, characterized in that: include: The base of the robot is taken as the origin, the reachable working space of the robot in space is taken as the working boundary, the direction in which the robot approaches the object to be operated is taken as the normal, and the plane perpendicular to the normal is taken as the plane where the object to be operated is located; The target sampling area for the end movement of the robot arm is divided from the plane direction dimension where the object to be operated is located, combined with the working boundary of the robot arm; the target sampling area is divided into several blocks in the form of a grid network and numbered as target sampling points, and the sampling points are assigned values ​​in turn, and the values ​​are used to indicate whether the object to be operated is touched; The robot arm autonomously polls each sampling point in the order of sampling points, and records whether the end of the robot arm touches the target when it is at each sampling point and the stroke of the robot arm along the normal direction when it touches the target; According to the information of all the recorded sampling points, the position information of the object to be operated is obtained.

2. The end-of-arm contact positioning method according to claim 1, characterized in that: The robot arm autonomously polls each sampling point in the order of sampling points. The specific method is as follows: Move the robot arm to the location of the first sampling point and perform contact sampling operation: feed the robot arm toward the object to be operated along the normal direction; During the movement, the contact force collected by the robot arm is used to determine whether the end is in contact with the object to be operated. If it is judged to be in contact, the current sampling point is assigned a value of 1, and the stroke of the current robot arm along the normal direction is recorded, and the robot arm returns. If it is still judged to be not in contact until the end movement stroke exceeds the maximum movement depth of the robot arm, the current sampling point is assigned a value of 0, and the robot arm returns. After the robot arm returns to the starting position, it moves to the location of the next sampling point and performs the contact sampling operation again; this polling is repeated until the contact sampling operation is completed for all sampling points.

3. The end-of-arm contact positioning method according to claim 2, characterized in that: During the movement, the contact force collected by the robot arm is used to determine whether the end is in contact with the object to be operated. Specifically: The force sensor module inside the robotic arm monitors the force information collected by the force sensor at the end of the robotic arm in real time, and filters and compensates the collected force information; The central controller in the robotic arm makes a judgment based on the filtered and compensated force information: if the force information is greater than the set contact force threshold, it is determined that the end of the robotic arm is in contact with the object to be operated at the current sampling point and at the current moment; otherwise, it is determined that the end of the robotic arm is not in contact with the object to be operated at the current sampling point and at the current moment.

4. The contact positioning method of the end of the robot arm according to claim 1, characterized in that: According to the information of all sampling points obtained, the position information of the object to be operated is obtained. The specific method is: All sampling point information obtained, including the location information of the sampling point, the state value of whether it is in contact, and the movement distance of the robot arm in the normal direction; Only the sampling point information corresponding to the contact state value of 1 is retained; The contour information and depth information of the object to be operated are obtained by integrating the movement stroke of the robot arm in the normal direction corresponding to each sampling point, and the position area range of the object to be operated is formed.

5. The end-of-arm contact positioning method according to claim 1, characterized in that: Within the boundary of the target area, the plane target area is divided into several areas in the form of a grid network and labeled. The labeling method adopts the matrix numbering form, which is denoted by x ij , which represents the area located in the i-th horizontal direction and the j-th vertical direction in the divided plane target area.

6. The end-of-arm contact positioning method according to claim 1, characterized in that: Within the target area boundary, the plane target area is divided into several regions in the form of a grid network, each region is α×α, where α satisfies: e robot ≤α≤ε goal In the formula, ε robot Represents the positioning accuracy of the robot arm, ε goal Represents the expected positioning accuracy of the object to be operated.

7. The contact positioning method of the end of the robot arm according to claim 1, characterized in that: The robotic arm system includes a central controller, a robotic arm controller, a force sensor acquisition module, and a force signal processing module; The central controller sends motion instructions to the robot arm controller; The robot controller converts the motion instructions into the robot joint space and controls the robot to achieve motion; The force sensor acquisition module is located at the end of the robotic arm and monitors the force information collected by the force sensor at the end of the robotic arm in real time; The force signal processing module filters and compensates the collected force information and sends the processed information to the central controller.

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