Mechanical arm end contact positioning method

Abstract

The application discloses a mechanical arm end contact positioning method and belongs to the technical field of mechanical arm positioning and identification. The method divides a target sampling area, controls a mechanical arm to autonomously move and poll a target sampling point, approaches an object to be operated, and judges whether the object to be operated is contacted through an end force sensor, so that the position and depth information of the object to be operated are marked in the target area. When the polling is completed, the position area range of the object to be operated can be formed, and the positioning of the object to be operated is completed. The application can accurately obtain the contour and depth information of the object to be operated under the conditions that the environment is complex, the implementation condition is without vision, and the information of the object to be operated is less known.

Description

TECHNICAL FIELD

[0001] The application relates to a mechanical arm end contact positioning method and belongs to the technical field of mechanical arm positioning and identification. BACKGROUND

[0002] Mechanical arms are widely used in industrial production and special operation fields, and are generally characterized by multiple degrees of freedom to flexibly control poses and then complete a series of fine assembly operations. In the process, the mechanical arm needs to position and identify the operated object and then further operate. Common mechanical arm positioning and identification technologies are as follows: (1) fixed measurement or drag teaching is used to obtain a target position. This process needs personnel to participate, requires a simple and friendly working area environment, and needs to be re-measured after each movement or replacement of components, so the process is relatively complex; (2) a camera is installed and a computer is used for image processing in a visual manner. The image processing and coordinate conversion algorithm is more complex, and the shape information or feature identification of the target object needs to be known for visual training and identification. In some complex environments where vision cannot work, such as underwater, mine, underground and the like, when the operated object needs to be positioned and identified and operated, a mechanical arm positioning technology with stronger autonomy and without the need for direct participation of vision and operators needs to be invented.

[0003] Chinese patent CN112248860A discloses a method for positioning an operated object by using an ultrasonic wave emitting probe on a vehicle end and an ultrasonic wave receiving probe on a charging mechanical arm end. After the mechanical arm moves to a working area, the kinematic parameters of the mechanical arm are calculated according to the time when the ultrasonic wave probe receives a detection signal, the mechanical arm is controlled to move to a positioning area, and the automatic charging mechanical arm is connected with the vehicle end connector. This method uses an ultrasonic wave positioning method to position the operated object, but requires that the operated object is installed with an ultrasonic wave emitting probe and the state is known. For scenes in a complex environment where the information of the operated object is not clear, the method is difficult to implement.

[0004] Chinese patent CN118078220A discloses a human spine positioning method based on mechanical arm force perception. A depth camera is used to perform three-dimensional reconstruction and segmentation of the back of a human body (an operated object), a 3D key point detection network is used to perform rough positioning on a point cloud model, an initial motion trajectory is planned, a mechanical arm is controlled to move to collect force sensor information, and an accurate spine position is obtained. This method is applied to a medical detection scene to simulate hand palpation, but the precondition is still a visual recognition and modeling method based on a depth camera. In scenes where vision is not suitable for implementation, the method is difficult to use. SUMMARY

[0005] The technical problems solved by the present application are: overcoming the deficiencies of the prior art, providing a mechanical arm end contact positioning method, solving the problem of mechanical arm end autonomous positioning in the case of no vision, no direct participation of personnel and less information about the object to be operated.

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

[0007] A mechanical arm end contact positioning method, comprising:

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

[0009] The target sampling region for the movement of the mechanical arm end is obtained by dividing the plane direction dimension in which the object to be operated is located and combining the working boundary of the mechanical arm; the target sampling region is divided into a plurality of blocks in the form of a grid network and labeled as target sampling points, and the sampling points are sequentially assigned values, with the values being used to represent whether the object to be operated is contacted;

[0010] The mechanical arm autonomously polls each sampling point in the order of the sampling points, and records whether the mechanical arm end contacts the target and the travel of the mechanical arm along the normal when the mechanical arm end contacts the target when the mechanical arm is at each sampling point;

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

[0012] Further, the mechanical arm autonomously polls each sampling point in the order of the sampling points, and the specific method is:

[0013] The mechanical arm is moved to the position of the first sampling point, and a contact sampling operation is performed: the mechanical arm is moved towards the object to be operated along the normal direction; during the movement, whether the mechanical arm end contacts the object to be operated is determined according to the contact force collected by the mechanical arm; if it is determined that the mechanical arm end contacts the object to be operated, the current sampling point is assigned a value of 1, and the travel of the mechanical arm along the normal is recorded, and the mechanical arm returns; if the travel of the mechanical arm end exceeds the maximum movement depth of the mechanical arm and it is still determined that the mechanical arm end does not contact the object to be operated, the current sampling point is assigned a value of 0, and the mechanical arm returns;

[0014] After the mechanical arm returns to the starting position, the mechanical arm is moved to the position of the next sampling point, and the contact sampling operation is performed again; the polling is repeated until the contact sampling operation is completed for all the sampling points.

[0015] Further, during the movement, whether the mechanical arm end contacts the object to be operated is determined according to the contact force collected by the mechanical arm, and the specific method is:

[0016] The inner force sensor module of the robot arm monitors force information collected by the robot arm end force sensor in real time, filters and compensates the collected force information.

[0017] The central controller in the robot arm judges based on the filtered and compensated force information: if the force information is greater than a set contact force threshold, it is determined that the robot arm end has contact with the object to be operated at the current sampling point and time, otherwise it is determined that the robot arm end has no contact with the object to be operated at the current sampling point and time.

[0018] Further, based on the obtained information of all sampling points, the position information of the object to be operated is obtained, and the specific method is:

[0019] All obtained sampling point information includes the position information of the sampling point, the state value of whether contact, and the travel in the normal direction of the robot arm;

[0020] Only the sampling point information corresponding to the contact state value of 1 is retained; the travel in the normal direction of the robot arm corresponding to each sampling point is integrated to obtain the contour information and depth information of the object to be operated, and the position range of the object to be operated is formed.

[0021] Further, within the target region boundary, the planar target region is divided into a plurality of regions in the form of a grid network and labeled, and the labeling method adopts a matrix numbering form, denoted as x ij , representing that the region is located in the i-th horizontal and j-th vertical of the divided planar target region.

[0022] Further, within the target region boundary, the planar target region is divided into a plurality of regions in the form of a grid network, and each region has a size of α×α, where α satisfies:

[0023] ε robot ≤α≤ε goal

[0024] In the formula, ε robot represents the positioning accuracy of the robot arm, and ε goal represents the desired positioning accuracy of the object to be operated.

[0025] Further, the robot arm system includes a central controller, a robot arm controller, a force sensor collection module, and a force signal processing module.

[0026] The central controller sends a motion instruction to the robot arm controller.

[0027] The robot arm controller converts the motion instruction to the joint space of the robot arm and controls the robot arm to realize the motion.

[0028] The force sensor collection module is located at the end of the robot arm and monitors force information collected by the robot arm end force sensor 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] Compared with the prior art, the present application has the following advantages:

[0031] (1) The present application divides the target sampling area based on the workspace of the mechanical arm, taking the reachable area of the mechanical arm itself as the working boundary, so that the information acquisition is easier and more accurate, and the problem of being unable to determine the working area due to the difficulty in obtaining the region information of the object to be operated in a complex environment is avoided.

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

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

[0034] (4) The present application uses the end torque sensor provided by the mechanical arm itself as the measurement device, avoiding the use of cameras, lasers and other sensing measurement devices that require high environmental requirements or need to operate the object to be operated, which is convenient to implement.

[0035] (5) The present application uses 0 and 1 to mark the state of whether the end of the mechanical arm contacts the object to be operated, and records the movement depth when contact occurs, which is a simple and accurate way to describe the sampling state of the target sampling point.

[0036] (6) The present application filters and compensates the collected force information through the force sensor module, which can obtain smoother and more real force collection information.

[0037] (7) According to the sampling values of all sampling points and the movement stroke information when contact occurs, the present application can establish the position area range of the object to be operated in two dimensions of the plane direction and the normal direction, and obtain the contour and depth information of the object to be operated, which is more accurate in describing the shape and position of the object to be operated, and is also beneficial to the subsequent operation task implementation. BRIEF DESCRIPTION OF DRAWINGS

[0038] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments with reference made to the accompanying drawings. The drawings are for purposes of illustration only and serve to build a better understanding of the invention. The same reference numerals used throughout describe the same components. In the drawings:

[0039] Figure 1 Flow chart of the embodiment of the end-of-arm contact positioning method of the present application;

[0040] Figure 2 Schematic diagram of the end-of-arm contact positioning module of the embodiment of the present application;

[0041] Figure 3 Schematic diagram of the end-of-arm contact positioning method of the embodiment of the present application;

[0042] Figure 4 Schematic diagram of the normal direction and the plane direction of the embodiment of the present application;

[0043] Figure 5 Schematic diagram of the target area plane division method of the embodiment of the present application;

[0044] Figure 6 Schematic diagram of the target area force contact positioning mark of the embodiment of the present application. DETAILED DESCRIPTION

[0045] Exemplary embodiments of the present disclosure will be described below in greater detail with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the drawings, it is understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be accurately conveyed to those skilled in the art.

[0046] The present application proposes an end-of-arm contact positioning method, which divides a target area, controls the end-of-arm to poll target sampling points autonomously, approaches an object to be operated, and judges whether it is in contact with the target through an end-of-arm force sensor to mark the target position and depth information in the target area, and when polling is completed, the position area range of the object to be operated is formed to complete the positioning of the object to be operated. The relationship between the operation modules involved in the method is as shown in the schematic diagram of the end-of-arm contact positioning method of the embodiment of the present application. Figure 2The central controller sends motion instructions to the robot arm controller, which includes motion planning, interpolator, kinematics and other functional modules of the robot arm, and is responsible for converting the motion instructions issued by the central controller into the joint space of the robot arm and controlling the robot arm to realize motion. A force sensor acquisition module is provided at the end of the robot arm to monitor the force information collected by the force sensor at the end of the robot arm in real time, and a force signal processing module is responsible for filtering and compensating the collected force information, and sending the processed more smooth and real information to the central controller.

[0047] The method is as shown in Figure 1 , and specifically includes:

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

[0049] When the area information of the object to be operated is less known, it is difficult to directly determine the target area from the range of the object to be operated. The reachable workspace of the robot arm in space is taken as the target area with the robot arm base as the origin. The direction of the target area is specified, and the direction of the robot arm approaching the target is the normal direction, and the plane perpendicular to the normal direction is the plane direction of the object to be operated, as shown in Figure 3 .

[0050] Step 2: Target area division

[0051] According to the target area and direction determined in step 1, the target area is divided from the plane direction dimension where the object to be operated is located, as the target area of the robot arm end motion. Within the boundary of the target area, the plane target area is divided into a plurality of small areas in the form of a grid network, and the size of each grid is α x α (unit: mm), wherein the value of α is selected by the designer according to the positioning accuracy level of the robot arm 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), and ε goal represents the expected positioning accuracy of the object to be operated (unit: mm).

[0054] Each area is numbered as a target sampling point, and the numbering method adopts a matrix numbering form, denoted as x 11 , x 12 , …, x mn (m, n represent the maximum number of regions divided in the horizontal and vertical directions of the plane, respectively), as shown in Figure 5 .

[0055] x 11 , x 12 , …, xmn ∈C plane

[0056] In the formula, C plane represents the range of the plane direction of the workspace of the robot arm.

[0057] Each grid target sampling point contains a numerical value representing the state of 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] As Figure 4 shown.

[0059]

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

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

[0062] Starting from the sampling point x 11 , the central controller issues a translation motion instruction to the robot arm controller, which includes motion planning, interpolator, kinematics, and other functional modules in the robot arm controller, responsible for converting the motion instruction issued by the central controller to the joint space of the robot arm and controlling the robot arm to realize motion. The end of the robot arm moves in the plane direction to the position of the sampling point x 11 , as Figure 3 shown.

[0063] Step 4: The robot arm end feeds motion for contact sampling.

[0064] After the robot arm end moves to the sampling point in the previous step, the central controller issues a feed motion instruction to the robot arm controller, which controls the robot arm to feed motion in the normal direction of the target area, as Figure 4 shown. During this process, the force sensor acquisition module monitors the force information collected by the force sensor at the end of the robot 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 according to 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 , it is judged that the end of the robot arm has contact with the target object at this time, and the target sampling point is marked as having contact, and the numerical value of the corresponding grid area is marked as 1, as Figure 6 shown, and records the stroke of the robot arm along the normal direction at this time, denoted as d ij, control the robot arm to return; when the stroke of the end motion exceeds the maximum motion depth of the robot arm and the contact force information is still not collected, mark the target sampling point as no contact, mark the value of the corresponding grid area as 0, control the robot arm to return, the maximum motion depth d of the robot arm max Selected by the designer according to the reachable workspace of the robot arm.

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

[0067] F ij < F th , and d mov > d max , 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) contacts the object to be operated, d mov represents the stroke of the robot arm along the normal direction, d ij represents the depth when contacting the object to be operated, d max represents the maximum depth of the robot arm motion. 0 < i < m, 0 < j < n.

[0069] Step 5: complete the polling of the target sampling points.

[0070] After the robot arm detects the previous sampling point and returns to the starting position, the central controller issues a motion translation motion instruction to control the robot arm to move to the next target sampling point, and repeats steps 3 and 4 to start the detection of the next sampling target point. The collected results are stored in the central controller. Until the polling detection of all target sampling points is completed, the sampling process is ended.

[0071] Step 6: count the sampling results and generate target position information.

[0072] After sampling, the central controller collects all the data of the sampling points. For each sampling point, it contains three information: (1) First, the serial number of the sampling point i, j represents the position of the sampling point in the workspace plane direction. This position can represent the position information of the sampling point in the form of coordinates. (2) The state of whether the sampling point contacts the object to be operated x ij is 0 or 1, (3) the stroke d ij of the robot arm motion in the normal direction, when the contact state is 1, dij The value of i is not 0.

[0073] When the sampling is finished, according to the information of all the sampling points obtained, the position information of the object to be operated can be represented, wherein only the sampling points with the contact state of 1 are effective sampling points, and the motion stroke d of the effective sampling points is integrated ij That is, the contour information and the depth information of the object to be operated can be obtained, and the position range of the object to be operated can be established, so that the positioning of the object to be operated by the robot arm is realized.

[0074] Through the above six steps, the end contact positioning method described in the application is completed. Without the participation of vision and personnel, the self workspace of the robot arm is divided into regions, the polling detection of the target by the end force sensor is performed on the divided grid target region, and the autonomous positioning of the robot arm in the space of the object to be operated is realized. The positioning result obtained contains the contour and depth information of the object to be operated, which is helpful for the further operation of the robot arm.

[0075] The end contact positioning method of the robot arm proposed in the application is implemented without vision and with less understanding of the target information, and does not require other operations on the target and personnel participation. Through the end force sensing module set by the robot arm itself, the grid target region divided by the self workspace of the robot arm is used to control the movement of the robot arm to poll and contact the sampling points of the target, a series of contact information and depth information of the object to be operated at the time of contact are obtained, and the shape contour and position of the object to be operated are described, so that the problem of obtaining the position of the target without vision and without direct participation of personnel is solved.

[0076] The above-described embodiments are only the preferred specific embodiments of the application, and the usual changes and replacements made by those skilled in the art within the scope of the technical solutions of the application should be included in the protection scope of the application.

Claims

1. A mechanical arm end contact positioning method characterized by, The application relates to a method for obtaining the position information of an object to be operated by a robot arm. The reachable working space of the robot arm in space is taken as the working boundary, and the direction in which the robot arm approaches the object to be operated is taken as the normal direction. The object to be operated is taken as the plane perpendicular to the normal direction. The object to be operated is divided into a plurality of block regions in the form of a grid network, and the block regions are taken as target sampling points. The robot arm is polled in the order of the target sampling points, and whether the end of the robot arm contacts the object to be operated and the stroke of the robot arm along the normal direction when the end of the robot arm contacts the object to be operated are recorded. The position information of the object to be operated is obtained according to the information of all the target sampling points. The robot arm is polled in the order of the target sampling points. The robot arm is moved to the position of the first target sampling point, and a contact sampling operation is performed. During the movement, whether the end of the robot arm contacts the object to be operated is judged according to the contact force collected by the robot arm.

2. The mechanical arm end contact positioning method according to claim 1, wherein, If the end of the robot arm contacts the object to be operated, the current target sampling point is assigned a value of 1, and the stroke of the robot arm along the normal direction is recorded. If the end of the robot arm does not contact the object to be operated, the current target sampling point is assigned a value of 0. The robot arm is returned to the starting position, and then is moved to the position of the next target sampling point.

3. The mechanical arm end contact positioning method of claim 1, wherein, The robot arm is polled in the order of the target sampling points until the contact sampling operation is completed for all the target sampling points. During the movement, whether the end of the robot arm contacts the object to be operated is judged according to the contact force collected by the robot arm. The force information collected by the force sensor at the end of the robot arm is monitored by the force sensor module in the robot arm. The force information is filtered and compensated.

4. The mechanical arm end contact positioning method of claim 1, wherein, In the target region boundary, the planar target region is divided into several regions in the form of grid network and labeled, the labeling method adopts matrix numbering form, denoted as x ij , representing the region is located in the horizontal i-th and vertical j-th of the divided planar target region.

5. The mechanical arm end-effort positioning method of claim 1, wherein, The central controller in the robot arm judges whether the force information is greater than the set contact force threshold value. e robot ≤ a < e goal In the formula, ε robot represents the positioning accuracy of the robot arm, ε goal represents the desired positioning accuracy of the object to be operated.

6. The mechanical arm end contact positioning method of claim 1, wherein, If the force information is greater than the set contact force threshold value, it is determined that the end of the robot arm contacts the object to be operated. If the force information is not greater than the set contact force threshold value, it is determined that the end of the robot arm does not contact the object to be operated. The position information of the object to be operated is obtained according to the information of all the target sampling points. The position information of the object to be operated is obtained according to the information of all the target sampling points. The position information of the object to be operated is obtained according to the information of all the target sampling points. The robot arm system comprises a central controller, a robot arm controller, a force sensor collection module and a force signal processing module. The central controller sends a movement instruction to the robot arm controller. The robot arm controller converts the movement instruction into the joint space of the robot arm and controls the robot arm to move. The robot arm system comprises a central controller, a robot arm controller, a force sensor collection module and a force signal processing module. The force sensor acquisition module is located at the end of the mechanical arm and monitors force information collected by the force sensor at the end of the mechanical 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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