A collaborative pick-and-place planning method for dual SCARA robots

Abstract

This invention discloses a collaborative grasping and placing planning method for dual SCARA robots. The method involves first using a visual system to determine the center point position vector, posture angle, and object length of the object being grasped and placed at its starting point; then generating path points for the grasping and placing trajectory based on the target endpoint; and finally generating grasping point position vectors for the master and slave robots. These grasping point position vectors are then adjusted based on the two-dimensional force sensing information at the end of the slave robot. This invention utilizes two SCARA robots on a production line to collaboratively grasp and place higher-quality materials that exceed the load capacity of a single robot. This method eliminates the need to modify existing production lines or upgrade robot models, resulting in lower equipment costs.

Description

Technical Field

[0001] The present invention relates to the field of robotics and automation, and in particular to a collaborative grasping and placing planning method for dual SCARA robots. Background Art

[0002] SCARA stands for Selective Compliance Assembly Robot Arm, meaning a robotic arm used for assembly operations. It has three rotary joints, making it ideal for planar positioning. High-speed SCARA robots are a type of high-speed, high-precision planar articulated robot, capable of four degrees of freedom (DOF) in three directions (X, Y, and Z) and rotation about the Z axis. These robots meet the needs of specialized environments where space is limited and light, small, and bulky materials need to be handled. They help production lines achieve high-speed, precise, and continuous handling and sorting operations, making them particularly suitable for applications in industries such as lithium batteries, photovoltaics, and pharmaceuticals.

[0003] High-speed SCARA robots are primarily used for the rapid handling of lightweight materials. However, when the materials being handled are heavy, existing SCARA robots may not be able to meet the load requirements. A common solution is to replace the robot with one with a higher load capacity, but this involves purchasing a new SCARA robot and modifying the production line, which undoubtedly increases production and operating costs. Summary of the Invention

[0004] The problem to be solved by the present invention is to provide a collaborative grasping and placing planning method for dual SCARA robots.

[0005] To solve the above problems, the present invention provides a dual SCARA robot collaborative grasping and placing planning method. To achieve the above objectives, the technical solution adopted by the present invention to solve the technical problems is:

[0006] A dual-SCARA robot collaborative grasping and placing planning method comprises: step S1: determining, by a visual system, that an object to be grasped and placed is at a starting point; step S2: determining, according to task requirements, that the object to be grasped and placed is at an end point; step S3: planning a gate-shaped grasping and placing trajectory using position vectors obtained in steps S2 and S3 and attitude transformation angles in a fixed coordinate system and a relative system; step S4: defining two robots as an active robot and a passive robot, respectively, and defining grasping points of the active robot and the passive robot on the object to be grasped and placed; and step S5: using a two-dimensional force sensor installed at the end of the passive robot to detect in real time the force exerted on the passive robot when it moves to step S4.

[0007] As a further improvement of the present invention, step S1 includes: determining by the visual system that when the object to be grasped and placed is at the starting point, the position vector of the center point P0 of the object to be grasped and placed at the starting point in the robot reference coordinate system O-xyz is rP0 =(x0 y0 z0) T , the fixed coordinate system P0-x of the captured object P0 y P0 z P0 The attitude transformation angle of the relative system O-xyz (rotation angle around the z axis) is θ0, and the object to be grasped and released is at x P0 with y P0 The lengths in the directions are L x With L y .

[0008] As a further improvement of the present invention, step S2 includes: determining the center point P of the object to be caught at the end point according to the task requirements. n The position vector in the robot reference coordinate system O-xyz is r Pn =(x n y n z n ) T , the fixed coordinate system Pn-x of the captured object P ny P nz P The attitude transformation angle of the relative system O-xyz (rotation angle around the z axis) is θ n .

[0009] As a further improvement of the present invention, step S3 includes: using the r obtained in step S1 and step S2 P0 With r Pn , and θ0 and θ n , the trajectory planning method is used to obtain the path point position vector r on the door-shaped pick-up and release trajectory Pi and θ i (i=1,2,…,n-1).

[0010] As a further improvement of the present invention, the gate-shaped catch-and-release trajectory includes a vertical upward motion line, a horizontal motion line, and a vertical downward motion line, and both ends of the horizontal motion line are vertically connected to the vertical upward motion line and the vertical downward motion line respectively.

[0011] As a further improvement of the present invention, step S4 includes: defining the grasping points of the active robot and the slave robot on the grasped object to be P and P respectively. i a With P i p , then point P i a With P i p The position vector in the robot reference coordinate system O-xyz is calculated by the following formula;

[0012] When Ly ≥L x hour,

[0013]

[0014] When L y <L x hour,

[0015]

[0016] Where:

[0017]

[0018] As a further improvement of the present invention, step S5 includes: using a two-dimensional force sensor installed at the end of the slave robot to detect in real time the movement of the robot to the i-th grasping point P obtained in step S4 i p The force along x Pi with y Pi The force f in the direction i px With f i py .

[0019] As a further improvement of the present invention, the step S6 is included; Step S6: according to the air pressure P of the suction cup of the dual robot end effector air , the suction cup area S and the maximum friction factor μ between the suction cup and the grasped object, the maximum static friction is calculated as:

[0020] [f]=μP air S

[0021] If f i px <[f] and f i py <[f], the master and slave robots will grasp firmly and no adjustment is required;

[0022] If f i px ≥[f] or f i py ≥[f], then the grasping position of the slave robot needs to be adjusted by the following formula;

[0023] When L y ≥L x hour,

[0024]

[0025] When L y <L x hour,

[0026]

[0027] Where:

[0028]

[0029] Among them, K represents the elastic adjustment coefficient, which is debugged according to actual operating conditions.

[0030] As a further improvement of the present invention, the following steps are included: step S7; using the θ obtained in step S3 i , obtained in step S4 Step S6 obtained Construct n+1 grasping trajectory points of the active robot and the slave robot respectively, and then realize the cooperative motion control of the two robots with the help of position inverse solution.

[0031] The beneficial effect of the dual SCARA robot collaborative grasping and placing planning method of the present application is that: through collaborative planning, two SCARA robots on an existing production line can be used to jointly grasp and place a material, so that a SCARA robot with a relatively small load capacity can be used to grasp and place relatively large-mass materials, and the gravity of the material is shared by the two SCARA robots. The mass of the material can exceed the load capacity of a single SCARA robot, so there is no need to modify the existing production line or upgrade the SCARA robot model. Using two high-speed SCARA robots to collaboratively carry higher-quality materials is a cost-effective and intelligent solution. By refining the dual-machine collaborative grasping and placing planning method, the load capacity and flexibility of the grasping and placing operation can also be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0033] Figure 1 Schematic diagram of dual SCARA robots collaborative pick-and-place according to one embodiment of the present invention;

[0034] Figure 2 It is a schematic diagram of the grabbing points and coordinate system on the grab and release material according to one embodiment of the present invention.

[0035] 1-Object to be grasped and released; 2-Active robot; 3-Slave robot. DETAILED DESCRIPTION

[0036] The present invention will be described in further detail below with reference to specific embodiments:

[0037] A collaborative pick-and-place planning method for dual SCARA robots of the present invention comprises the following steps:

[0038] Step S1: The visual system determines that when the object 1 is at the starting point, the position vector of its center point P0 in the robot reference coordinate system O-xyz is r P0 =(x0 y0 z0) T , the fixed coordinate system P0-x of the object 1 P0 y P0 z P0 The attitude transformation angle (rotation angle around the z axis) of the relative system O-xyz is θ0, and the object 1 is at x P0 with y P0 The lengths in the directions are L x With L y ,like Figure 2 shown.

[0039] A fixed coordinate system, also known as a fixed coordinate system or a fixed coordinate system, is a coordinate system that rotates with a central celestial body (such as the Earth or the Moon). The origin of this coordinate system is usually located at the center of mass of the central celestial body, and the coordinate axes are defined based on the characteristics and requirements of the specific celestial body. A relative coordinate system, also known as a non-inertial coordinate system or a moving coordinate system, is a coordinate system that is in motion relative to an inertial coordinate system (i.e., a coordinate system that does not rotate or translate with any object). In a relative coordinate system, the motion of an object (including position, velocity, and acceleration) is affected by inertial forces.

[0040] Step S2: Determine the center point P of the object to be grasped when it is at the end point according to the task requirements. n The position vector in the robot reference coordinate system O-xyz is r Pn =(x n y n z n ) T , the fixed coordinate system P of the object 1 n -x Pn y Pn z Pn The attitude transformation angle (rotation angle around the z axis) of the relative system O-xyz is θ n .

[0041] Step S3: Using the r obtained in step S1 and step S2 P0 With r Pn , and θ0 and θ n , the trajectory planning method can be used to obtain the path point position vector r on the door-shaped pick-up and release trajectory Pi and θ i (i=1,2,…,n-1).

[0042] The gate-shaped catch-and-release trajectory is composed of a vertical upward motion line, a horizontal motion line, and a vertical downward motion line. The two ends of the horizontal motion line are respectively vertically connected to the vertical upward motion line and the vertical downward motion line.

[0043] Step S4: define the two SCARA robots as the active robot 2 and the slave robot 3, respectively, and define the grasping points of the active robot 2 and the slave robot 3 on the grasped object 1 as P and P respectively. i a With P i p , then point P i a With P i p The position vector in the robot reference coordinate system O-xyz can be calculated by the following formula.

[0044] P i a With P i p The midpoint of the line can be exactly P i In the gate-shaped pick-and-place trajectory, the one with a relatively long distance can correspond to the active robot 2.

[0045] When L y ≥L x hour,

[0046]

[0047] When L y <L x hour,

[0048]

[0049] Where:

[0050]

[0051] Step S5: The two-dimensional force sensor installed at the end of the slave robot 3 can be used to detect in real time the movement of the robot to the i-th grasping point P obtained in step S4. i p The force along x Pi with y Pi The force f in the direction i px With f i py .

[0052] Step S6: According to the double robot end effector suction cup air pressure P air, the suction cup area S and the maximum friction factor μ between the suction cup and the grasped object, the maximum static friction is calculated as:

[0053] [f]=μP air S

[0054] If f i px <[f] and f i py <[f], the active robot 2 and the driven robot 3 grasp firmly and no adjustment is required;

[0055] If f i px ≥[f] or f i py ≥[f], the grasping position of the slave robot 3 needs to be adjusted using the following formula.

[0056] When L y ≥L x hour,

[0057]

[0058] When L y <L x hour,

[0059]

[0060] Where:

[0061]

[0062] Among them, K represents the elastic adjustment coefficient, which is debugged according to actual operating conditions.

[0063] Step S7: Using the θ obtained in step S3 i , obtained in step S4 Step S6 obtained n+1 grasping trajectory points of the active robot 2 and the slave robot 3 can be constructed respectively, and then the coordinated motion control of the two robots can be realized with the help of position inverse solution.

[0064] Inverse kinematics is a concept in robotic kinematics. It refers to the process of determining the kinematic variables of each robot joint, given the position and posture of the robot's end effector (such as a manipulator) in a reference coordinate system. This process is the opposite of forward kinematics, which calculates the position and posture of the end effector based on the kinematic parameters and angles of each robot joint.

[0065] When the total lengths of the gate-shaped grasping and releasing trajectories of the active robot 2 and the driven robot 3 are equal, and the grasped and released object 1 is rotated 90°, there exists a spatial plumb plane so that the two gate-shaped grasping and releasing trajectories are mirror-symmetrical to each other, and the spatial intersection of the two trajectories is located on this spatial plumb plane.

[0066] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A dual SCARA robot collaborative pick-and-place planning method, characterized in that: include: Step S1: The visual system determines that the object to be grasped and released is at the starting point; Step S2: Determine the end point of the grasped object according to the task requirements; Step S3: planning a gate-shaped pick-and-release trajectory; Step S4: defining the two robots as an active robot and a slave robot respectively, and defining the grasping points of the active robot and the slave robot on the grasped and placed objects; Step S5: Using a two-dimensional force sensor installed at the end of the slave robot, the force applied to the slave robot when the slave robot moves to the grasping point position in step S4 is detected in real time; The step S4 comprises: The grasping points of the active robot and the slave robot on the grasped object are defined as and , then point and In the robot reference coordinate system O-xyz The position vector under is calculated by the following formula; when hour, ， ， ； when hour, ， ， ； Where: ， ， ； Define the fixed coordinate system of the object being grasped and released at the starting point , For the captured object The length in the direction, For the captured object The length in the direction, The fixed coordinate system of the object being grasped and released at the starting point Relative system O-xyz Around The attitude change angle of the axis rotation; The step S5 comprises: The two-dimensional force sensor installed at the end of the slave robot is used to detect the robot's movement to the first position obtained in step S4 in real time. Grab points The edge and Force in the direction and ; Step S6: According to the air pressure of the suction cup of the dual robot end effector , Suction cup area and the maximum friction factor between the suction cup and the object being grasped , calculate the maximum static friction force as: ； like and , then the master and slave robots can grasp firmly and no adjustment is required; like or , then the grasping position of the slave robot needs to be adjusted by the following formula; when hour, ， ； when hour, ， ； Where: ， ； in, Indicates the elastic adjustment coefficient, which is obtained by debugging according to actual operating conditions; Step S7: Utilize , obtained in step S4 , obtained in step S6 Construct the active robot and the passive robot respectively. The collaborative motion control of the two robots is achieved by using the position inverse solution.

2. The dual SCARA robot collaborative pick-and-place planning method according to claim 1, characterized in that: The step S1 comprises: When the visual system determines that the object is at the starting point, the center point of the object at the starting point is In the robot reference coordinate system O-xyz The position vector under , the fixed coordinate system of the captured object Relative system O-xyz Around The attitude transformation angle of the axis rotation is , the captured object is placed in and The lengths in the directions are and .

3. The dual SCARA robot collaborative pick-and-place planning method according to claim 2, characterized in that: The step S2 comprises: Determine the center point of the captured object at the end point according to the task requirements In the robot reference coordinate system O-xyz The position vector under , the fixed coordinate system of the captured object Relative system O-xyz Around The attitude transformation angle of the axis rotation is .

4. The dual SCARA robot collaborative pick-and-place planning method according to claim 3, characterized in that: The step S3 comprises: The data obtained by step S1 and step S2 and ,as well as and , using the trajectory planning method to obtain the path point position vector on the door-shaped pick-up and release trajectory and .

5. The dual SCARA robot collaborative pick-and-place planning method according to claim 4, characterized in that: The gate-shaped catch-and-release track includes a vertical upward motion line, a horizontal motion line, and a vertical downward motion line. Two ends of the horizontal motion line are respectively vertically connected to the vertical upward motion line and the vertical downward motion line.

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