Control method of collaborative robot in palletizing process

Abstract

The present invention provides a control method for a collaborative robot in a palletizing process, wherein the collaborative robot includes a mechanical arm and a lifting column, and the method includes: determining a safety range of the mechanical arm, wherein the safety range refers to the range of motion of the mechanical arm when the lifting column descends to drive the mechanical arm to move, and the mechanical arm does not collide with the pallet plates and the stacking type on its left and right sides; when the palletizing of the last material in the stacking type is completed, the mechanical arm is controlled to move and at the same time, it is determined based on the safety range whether to turn on the control of the lifting column, and if so, the lifting column is controlled to descend to zero position while the mechanical arm is controlled to keep moving. Thus, when the last material in the stacking type is completed, the lifting column is controlled to descend based on the safety range of the mechanical arm, which can optimize the coordinated motion between the mechanical arm and the lifting column while ensuring safety, improve the continuity of the action, and thus improve the overall palletizing efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of palletizing, and in particular to a method for controlling a collaborative robot in a palletizing process. Background Art

[0002] When performing palletizing tasks, current collaborative robots cannot reach the required height by their own functions without the help of external mechanisms. Therefore, in this case, it is usually necessary to add a lifting column to the Z-axis of the collaborative robot arm so that the arm can move in the vertical direction to meet the requirements for the height of the stacked objects in actual production.

[0003] In the related art, the coordinated movement of the lifting column and the robotic arm is stiff and has poor continuity, which affects the palletizing efficiency. Summary of the invention

[0004] In order to solve the problem in the related art that the coordinated movement of the lifting column and the mechanical arm is stiff and has poor continuity, which affects the palletizing efficiency, the present invention proposes the following technical solution.

[0005] The first aspect of the present invention provides a method for controlling a collaborative robot in a palletizing process, wherein the collaborative robot comprises a robotic arm and a lifting column, wherein the lifting column is mounted on the lower surface of a base of the robotic arm, and wherein the method comprises the following steps: determining a safety range of the robotic arm, wherein the safety range refers to the range of motion of the robotic arm when the lifting column descends to drive the robotic arm to move without colliding with pallet stacks and stacks on its left and right sides; when completing the palletizing of the last material in the stack, controlling the movement of the robotic arm and determining whether to turn on the control of the lifting column based on the safety range, and if so, starting to control the lifting column to descend to zero position while controlling the robotic arm to keep moving.

[0006] In addition, the control method of the collaborative robot in the palletizing process according to the above embodiment of the present invention may also have the following additional technical features.

[0007] According to one embodiment of the present invention, the safety range of the robotic arm includes a safety angle range of the first joint of the robotic arm.

[0008] According to one embodiment of the present invention, determining the safety range of the robotic arm includes: determining an initial position of the robotic arm, wherein the center of the robotic arm flange is located directly in front of the robotic arm in the initial position; based on the initial position, controlling the movement of the robotic arm and determining the safety angle range of the first joint of the robotic arm based on the movement state.

[0009] According to one embodiment of the present invention, on the basis of the initial posture, the movement of the robot arm is controlled and the safe angle range of the first joint of the robot arm is determined based on the movement state, including: determining the maximum projection between the vertical projection of the pallet stack on the XOY plane of the base coordinate system and the vertical projection of the stack type on the pallet stack on the XOY plane of the base coordinate system; determining the initial angle of the first joint of the robot arm in the initial posture; controlling the first joint of the robot arm to rotate from the initial angle until the vertical projection of the robot arm on the XOY plane of the base coordinate system is tangent to the maximum projection, and recording the rotation angle of the first joint; obtaining the safe angle range of the first joint of the robot arm according to the initial angle and the rotation angle.

[0010] According to one embodiment of the present invention, the first joint of the robotic arm is controlled to rotate from the initial angle until the vertical projection of the robotic arm in the XOY plane of the base coordinate system is tangent to the maximum projection, and the rotation angle of the first joint is recorded, including: controlling the first joint of the robotic arm to rotate counterclockwise from the initial angle until the vertical projection of the robotic arm in the XOY plane of the base coordinate system is tangent to the maximum projection, and recording the counterclockwise rotation angle of the first joint; controlling the first joint of the robotic arm to rotate clockwise from the initial angle until the vertical projection of the robotic arm in the XOY plane of the base coordinate system is tangent to the maximum projection, and recording the clockwise rotation angle of the first joint.

[0011] According to one embodiment of the present invention, when the pallet stack and the stack are located on the left side of the robotic arm, the safety angle range of the first joint is [α_init, α_init+β_left], wherein α_init is the initial angle and β_left is the counterclockwise rotation angle; when the pallet stack and the stack are located on the right side of the robotic arm, the safety angle range of the first joint is [α_init-β_right, α_init], wherein β_right is the clockwise rotation angle, and α_init, β_left and β_right are all greater than 0 degrees.

[0012] According to one embodiment of the present invention, based on the initial posture, the movement of the robot arm is controlled and the safe angle range of the first joint of the robot arm is determined based on the motion state, including: controlling the robot arm to rotate to a reference posture in the initial posture, wherein the first link of the robot arm is perpendicular to the Y axis of the base coordinate system in the reference posture, and determining a reference angle of the first joint in the reference posture, a first straight line formed by the projection of the outermost edge of the preset link on the XOY plane of the base coordinate system, wherein the preset link is the second link or the third link; determining the outermost straight line corresponding to the stack type in the XOY plane of the base coordinate system small enclosing rectangle; control the robot arm to rotate to a tangent posture under the reference posture, wherein a second straight line formed by the projection of the outermost edge of the preset connecting rod on the XOY plane of the base coordinate system under the tangent posture is tangent to a corner point of the minimum enclosing rectangle, and determine the coordinates of the tangent corner point in the XOY plane of the base coordinate system under the tangent posture; calculate the angle between the first straight line and the second straight line based on the coordinates of the tangent corner point in the XOY plane of the base coordinate system; calculate the safe angle range of the first joint of the robot arm according to the reference angle and the angle between the first straight line and the second straight line.

[0013] According to one embodiment of the present invention, determining the minimum enclosing rectangle corresponding to the stack in the XOY plane of the base coordinate system includes: determining the coordinates of each corner point of any layer of boxes of the stack under the projection of the XOY plane of the base coordinate system; traversing and sorting the coordinates of all corner points, and screening out the minimum horizontal coordinate, the maximum horizontal coordinate, the minimum vertical coordinate and the maximum vertical coordinate; and obtaining the minimum enclosing rectangle corresponding to the stack in the XOY plane of the base coordinate system according to the minimum horizontal coordinate, the maximum horizontal coordinate, the minimum vertical coordinate and the maximum vertical coordinate.

[0014] According to one embodiment of the present invention, the base coordinate system takes the center of the robot arm base as its origin, the positive direction of the X-axis of the base coordinate system is toward the left side of the robot arm, and the positive direction of the Y-axis of the base coordinate system is toward the rear of the robot arm.

[0015] The coordinates of the tangent corner point in the XOY plane of the base coordinate system are:

[0016]

[0017] Among them, x min Indicates the minimum horizontal coordinate, y min represents the minimum ordinate, x max represents the maximum abscissa.

[0018] According to one embodiment of the present invention, the angle between the first straight line and the second straight line is calculated based on the coordinates of the tangent corner point in the XOY plane of the base coordinate system, including: determining a third straight line passing through the center point of the first joint and conforming to the Y axis of the base coordinate system in the reference posture; determining the distance between the third straight line and the first straight line in the reference posture; and calculating the angle between the first straight line and the second straight line according to the distance between the third straight line and the first straight line and the coordinates of the tangent corner point in the XOY plane of the base coordinate system.

[0019] According to one embodiment of the present invention, the angle between the first straight line and the second straight line is calculated by the following formula:

[0020]

[0021] Δx=x min

[0022] Δy=y min

[0023] Among them, α left represents the angle between the first straight line and the second straight line, x min Indicates the minimum horizontal coordinate, y min represents the minimum ordinate, distance represents the distance between the third straight line and the first straight line, Δx and Δy represent the distances between the tangent corner point and the Y axis and X axis of the base coordinate system respectively.

[0024] According to one embodiment of the present invention, when the stack type is located on the left side of the robotic arm, the preset connecting rod is the second connecting rod; when the stack type is located on the right side of the robotic arm, the preset connecting rod is the third connecting rod.

[0025] According to one embodiment of the present invention, when the stack is located on the left side of the robot arm, the safety angle range of the first joint is [α base , α base +α left ], where α base is the reference angle, α left is the angle between the first straight line and the second straight line when the stack is located on the left side of the robot arm, α base , α left are greater than 0 degrees; when the stack is located on the right side of the robot arm, the safety angle range of the first joint is [-α right +α base , α base ], where α base is the reference angle, α rightis the angle between the first straight line and the second straight line when the stack is located on the right side of the robot arm, α right Greater than 0 degrees.

[0026] According to one embodiment of the present invention, judging whether to start controlling the lifting column based on the safety range includes: acquiring the angle of the first joint of the mechanical arm; if the angle of the first joint of the mechanical arm is within the safety angle range, determining to start controlling the lifting column; if the angle of the first joint of the mechanical arm is not within the safety angle range, determining not to start controlling the lifting column.

[0027] The technical solution of the embodiment of the present invention first determines the safety range of the robot arm, wherein the safety range refers to the movement range of the robot arm when the lifting column descends to drive the robot arm to move without colliding with the pallet stacks and stacks on its left and right sides; then, when the palletizing of the last material in the stack is completed, the movement of the robot arm is controlled and at the same time, based on the safety range, it is determined whether to turn on the control of the lifting column; if so, the lifting column is controlled to descend to the zero position while the robot arm is controlled to keep moving.

[0028] Therefore, when the last material is palletized, the lifting column is controlled to descend based on the safety range of the robot arm, which can optimize the coordinated movement between the robot arm and the lifting column while ensuring safety, improve the continuity of movement, and thus improve the overall palletizing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The figure is a flow chart of a method for controlling a collaborative robot in a palletizing process according to an embodiment of the present invention.

[0030] Figure 2 This is a schematic structural diagram of a collaborative robot arm according to an embodiment of the present invention.

[0031] Figure 3 This is a schematic diagram of the safe angle range of the first joint according to an embodiment of the present invention.

[0032] Figure 4 The figure is a schematic diagram of calculating the minimum enclosing rectangle of an example of the present invention.

[0033] Figure 5 It is a schematic diagram of a first straight line formed by the projection of the outermost edge of the second connecting rod on the XOY plane in a reference posture of an example of the present invention.

[0034] Figure 6 This is a schematic diagram of calculating the angle between the second straight line and the first straight line according to an example of the present invention.

[0035] Figure 7A schematic diagram of a safe angle range of a first joint according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] Figure 1 The figure is a flow chart of a method for controlling a collaborative robot in a palletizing process according to an embodiment of the present invention.

[0038] It should be noted that the current movements of collaborative robots are divided into blocking movements and non-blocking movements. Blocking movements mean that the entire program cannot do anything else before reaching a specified point. Non-blocking movements mean that some other logical processing and communication control can be performed before reaching a specified point. The embodiment of the present invention controls the addition of non-blocking movements, and controls the lifting column during the movement of the collaborative robot's mechanical arm, so as to control the lifting column and the mechanical arm to move simultaneously under certain conditions, thereby realizing the coordinated work of the mechanical arm and the lifting column.

[0039] like Figure 1 As shown, the control method for the collaborative robot in the palletizing process includes the following steps S1 and S2.

[0040] Palletizing refers to stacking material boxes layer by layer on the pallet stacks on the left and right sides of the robot arm, where each layer includes at least one material box, and the sizes of the boxes can be the same or different.

[0041] The collaborative robot includes a robotic arm and a lifting column, which is installed on the lower surface of the robotic arm base along the Z-axis direction (vertical direction) of the robotic arm. Figure 2 As shown, it includes a first joint 1 (close to the base), a second joint 2, a first connecting rod (not shown in the figure) between the first joint 1 and the second joint 2, a second connecting rod 3 (big arm tube) and a third connecting rod 4 (small arm tube). The second connecting rod 3 refers to a connecting rod connecting the second joint 2 and the third joint, and the third connecting rod 4 refers to a connecting rod connecting the third joint and the fourth joint.

[0042] S1, determine the safety range of the robot arm, where the safety range refers to the range of movement of the robot arm when the lifting column descends to drive the robot arm to move without colliding with the pallet stacks and stacking types on its left and right sides.

[0043] Among them, the stack type refers to the material stack with the highest material layer already stacked.

[0044] Among them, the safety range of the robotic arm may be the safety angle range of its joints.

[0045] Specifically, before implementing the palletizing process, the movement of the robotic arm can be controlled in advance in the robot base coordinate system, and various parameters of the robotic arm can be obtained during the movement. The safety range of the robotic arm can be estimated or calculated based on various parameters, historical experience and the safety requirements of the palletizing process.

[0046] S2, when the palletizing of the last material in the pallet is completed, the robot arm is controlled to move and at the same time, it is determined whether to start the control of the lifting column based on the safety range. If so, the lifting column is controlled to descend to the zero position while the robot arm is controlled to keep moving.

[0047] Zero position refers to the position of the lifting column in its initial state without any lifting action, that is, the rising height is zero when the lifting column is in zero position.

[0048] Specifically, when the lifting column needs to be lowered, such as when the last material of the last layer of materials on the pallet (left or right side) is completed (at this time, the flange of the robot arm is located above the pallet), the robot arm's initial posture is used as the target to control the movement of the robot arm, and at the same time, based on the safety range, it is determined in real time whether to start (immediately) controlling the lifting column to descend, that is, it is necessary to determine the time point when the lifting column starts to descend, which can be achieved by determining whether the robot arm has reached its safety range. When the robot arm reaches its safety range, the lifting column is controlled to descend until it reaches zero position, while the robot arm is kept moving to ensure that the lifting column moves while the lifting column is descending, and the robot arm always collides and interferes with the pallet when the lifting column descends. Finally, the robot arm returns to its initial posture, and the lifting column returns to zero position. After descending to zero position, the palletizing process on the other side can be started. Increase the continuity of the action while ensuring safety.

[0049] In actual applications, after the last material is coded, the lifting column is not immediately controlled to descend. Instead, the robot arm is controlled to move (with the initial posture as the target). At the same time, the robot arm posture is monitored in real time to determine whether it is within a safe range. The safety range may not be met within a certain period of time, so the lifting column is not controlled during this period of time. After this period of time, when the robot arm meets the safety range, the lifting column is controlled to descend while keeping the robot arm moving.

[0050] It should be noted that no matter it is the palletizing process or the depalletizing process, there are situations where the lifting column needs to be lowered (the lifting column of the depalletizing process descends more frequently). Collision and interference should be prevented during the descent. Therefore, each time the lifting column needs to descend, it is necessary to determine whether the robotic arm is in a safe range. If so, it starts to control the descent of the lifting column while keeping the robotic arm moving to increase the continuity of the action.

[0051] In general, the embodiments of the present invention determine the safety range of the robotic arm in advance, and realize the coordinated work of the robotic arm and the lifting column on this basis: first, palletizing is realized by the robotic arm and the lifting column, and when the palletizing of the last layer is completed, the movement of the robotic arm is controlled until the robotic arm reaches the safety range, and then the lifting column is controlled to descend to the zero position, and the robotic arm keeps moving at the same time to ensure that the lifting column safely descends to the zero position without collision or interference.

[0052] In the related technology, a blocking motion strategy is adopted, and the lifting column and the robotic arm move independently without coordinated action, lacking overall coordinated continuity, affecting the overall rhythm of the production line, increasing time costs, and thus affecting the overall palletizing efficiency.

[0053] Compared with the related art, the embodiment of the present invention analyzes the palletizing process flow and determines a safety range. When the lifting column needs to move, a judgment on the safety range of the robot arm is added. The waypoint movement of the robot arm uses a non-blocking asynchronous method. When the robot arm is within the safety range, the lifting column is allowed to start moving (mainly descending action), which increases the continuity of the action, optimizes the coordinated movement between the robot arm and the lifting column, and improves the overall palletizing efficiency.

[0054] Therefore, the control method of the collaborative robot in the palletizing process of the embodiment of the present invention, when the last material of the palletizing type is completed, controls the descent of the lifting column based on the safety range of the robot arm, thereby optimizing the coordinated movement between the robot arm and the lifting column while ensuring safety, improving the continuity of movement, and thus improving the overall palletizing efficiency.

[0055] In one embodiment of the present invention, the safety range of the robot arm may be a safety angle range of the first joint (a joint connected to the base).

[0056] like Figure 3 As shown in the figure, assuming that the right and left sides of the collaborative robot have the same type of stack (stacked on the pallet), when the angle of the first joint of the robot body is Figure 3 When the two rays are between the two rays shown, it can be ensured that when the lifting column moves downward, the robot body and the stacking type and pallet of the materials on the left and right sides will never collide or interfere. Among them, the two rays are the rays formed by the angle of the first joint when the robot body does not collide or interfere with the stacking type and pallet of the materials on the left and right sides, and the inferior arc angle α_def between the two rays is the safe angle range of the first joint.

[0057] The embodiment of the present invention proposes two methods for obtaining the safe angle range, both of which are performed on the basis of the initial posture of the robot arm.

[0058] That is, in one embodiment of the present invention, determining the safety range of the robotic arm in step S1 may include: determining the initial position of the robotic arm, wherein the center of the robotic arm flange is located directly in front of the robotic arm in the initial position; based on the initial position, controlling the movement of the robotic arm and determining the safety angle range of the first joint of the robotic arm based on the motion state.

[0059] It should be noted that when the robot arm performs the palletizing process, there is an initial posture, which is used to maintain a safe state before each start or stop. Generally, this posture needs to ensure that the flange center or the tool connected at the end is facing the direction of the material coming from the conveyor belt of the assembly line, and the center of the robot arm flange is located directly in front of the robot arm to facilitate quick response and startup.

[0060] Specifically, the initial position and posture of the robot arm are first determined, the movement of the robot arm is controlled under the initial position and the motion state is determined in real time, the motion parameters are collected, and the safe angle range of the first joint is determined in combination with the motion state and the motion parameters.

[0061] Generally, the positive directions of each axis of the base coordinate system of the robot arm are determined by the actual installation method of the robot arm at the final site. In order to facilitate the subsequent description of the embodiments of the present invention, the direction of the base coordinate system (with the center of the base as the origin), that is, the positive direction X+ of the X-axis (towards the left side of the robot arm), the positive direction Y+ of the Y-axis (towards the back of the robot arm) and the positive direction Z+ of the Z-axis (towards the top of the robot arm) are the same as the world coordinate system. The plane where the robot base is located is parallel to the ground, that is, the XOY plane of the base coordinate system is parallel to the ground. Therefore, for the first joint of the robot arm, the rotation around the positive direction of the Z axis of the base coordinate system conforms to the provisions of the right-hand screw rule, that is, counterclockwise rotation, the value of the first joint angle increases, and clockwise rotation, The value of the first joint angle decreases.

[0062] Because the ultimate goal is to ensure that the vertical projection of the robot arm to the ground does not interfere with the vertical projection of the pallet and the stack to the ground, this engineering problem model can be placed on a two-dimensional plane of a base coordinate system XOY for processing. There are two ways to determine the safe angle range of the first joint. The first is to conduct an on-site assessment and roughly confirm a range. The second is to calculate it based on the mechanical appearance parameters of the robot.

[0063] A first method of determining the safe angle range of the first joint based on on-site evaluation is described below.

[0064] In an example of the present invention, based on the initial posture, controlling the movement of the robot arm and determining the safe angle range of the first joint of the robot arm based on the motion state may include: determining the maximum projection between the vertical projection of the pallet stack on the XOY plane of the base coordinate system and the vertical projection of the stack type on the pallet stack on the XOY plane of the base coordinate system; determining the initial angle of the first joint of the robot arm in the initial posture; controlling the first joint of the robot arm to rotate from the initial angle until the vertical projection of the robot arm on the XOY plane of the base coordinate system is tangent to the maximum projection, and recording the rotation angle of the first joint; and obtaining the safe angle range of the first joint of the robot arm based on the initial angle and the rotation angle.

[0065] Further, controlling the first joint of the robotic arm to rotate from an initial angle until the vertical projection of the robotic arm in the XOY plane of the base coordinate system is tangent to the maximum projection, and recording the rotation angle of the first joint may include: controlling the first joint of the robotic arm to rotate counterclockwise from the initial angle until the vertical projection of the robotic arm in the XOY plane of the base coordinate system is tangent to the maximum projection, and recording the counterclockwise rotation angle of the first joint; controlling the first joint of the robotic arm to rotate clockwise from the initial angle until the vertical projection of the robotic arm in the XOY plane of the base coordinate system is tangent to the maximum projection, and recording the clockwise rotation angle of the first joint.

[0066] Specifically, first, for the left-side stacking type or the right-side stacking type, determine the vertical projection of the pallet pallet on the XOY plane of the base coordinate system, the vertical projection of the pallet pallet on the XOY plane of the base coordinate system, and determine the maximum projection between the two projections, and determine the initial angle α_init of the first joint of the robot arm at the initial posture.

[0067] Then, for the left side stack, control the first joint to rotate counterclockwise from the initial angle, and monitor the vertical projection of the robot arm in the base coordinate system XOY plane in real time during the rotation process until the vertical projection is tangent to the maximum projection, and record the counterclockwise rotation angle β_left of the first joint at this time. Finally, according to the initial angle α_init of the first joint and the counterclockwise rotation angle β_left, the corresponding angle safety range of the first joint when the robot arm moves from the left side to the initial posture is obtained, that is, when the pallet and the stack are located on the left side of the robot arm, the safety angle range of the first joint is [α_init, α_init+β_left], where α_init is the initial angle and β_left is the counterclockwise rotation angle.

[0068] Then, for the right side stack, control the first joint to rotate clockwise from the initial angle, monitor the vertical projection of the robot arm in the base coordinate system XOY plane in real time during the rotation process, until the vertical projection is tangent to the maximum projection, and record the clockwise rotation angle β_right of the first joint at this time. Finally, according to the initial angle α_init of the first joint and the clockwise rotation angle β_right, the corresponding angle safety range of the first joint when the robot arm moves from the right side to the initial posture is obtained, that is, when the pallet and the stack are located on the right side of the robot arm, the safety angle range of the first joint is [α_init-β_right, α_init], where α_init is the initial angle and β_right is the clockwise rotation angle.

[0069] That is, the final calculation by evaluation Figure 3 The range of the minor arc angle α_def between the two rays in is [α_init-β_right, α_init+β_left], and α_init, β_left and β_right are all greater than 0 degrees.

[0070] In general, there is an initial posture, and the first joint angle of the robot arm when it rotates to this posture is α_init. After on-site observation, when the first joint starts to rotate clockwise by β_left and counterclockwise by β_right from this angle, the vertical projection of the robot arm on the XOY plane of the base coordinate system is not included in the vertical projection of the space occupied by any stack type and pallet stack to be used on the XOY plane of the base coordinate system. Therefore, the range of values ​​of the safety angle is obtained [α_init-β_right, α_init+β_left]. This interval is the safety angle range of the first joint.

[0071] Another method of calculating the safe angle range of the first joint based on the mechanical parameters is described below.

[0072] In another example of the present invention, based on the initial posture, controlling the movement of the robotic arm and determining the safe angle range of the first joint of the robotic arm based on the movement state may include: controlling the robotic arm to rotate to a reference posture in the initial posture, wherein the first link of the robotic arm is perpendicular to the Y axis of the base coordinate system in the reference posture, and determining the reference angle of the first joint in the reference posture, and the first straight line formed by the projection of the outermost edge of the preset link on the XOY plane of the base coordinate system, the preset link is the second link or the third link; determining the minimum enclosing rectangle corresponding to the stack type in the XOY plane of the base coordinate system; controlling the robotic arm to rotate to a tangent posture in the reference posture, wherein the second straight line formed by the projection of the outermost edge of the preset link on the XOY plane of the base coordinate system in the tangent posture is tangent to a corner point of the minimum enclosing rectangle, and determining the coordinates of the tangent corner point in the XOY plane of the base coordinate system in the tangent posture; calculating the angle between the first straight line and the second straight line based on the coordinates of the tangent corner point in the XOY plane of the base coordinate system; and calculating the safe angle range of the first joint of the robotic arm according to the reference angle and the angle between the first straight line and the second straight line.

[0073] Among them, the base coordinate system takes the center of the robot arm base as the origin, the positive direction of the X axis of the base coordinate system is toward the left side of the robot arm, the positive direction of the Y axis of the base coordinate system is toward the back of the robot arm, and the positive direction of the Z axis of the base coordinate system is toward the top of the robot arm.

[0074] Furthermore, determining the minimum enclosing rectangle corresponding to the stack in the XOY plane of the base coordinate system may include: determining the coordinates of each corner point of any layer of boxes in the stack under the projection of the XOY plane of the base coordinate system; traversing and sorting the coordinates of all corner points, and screening out the minimum horizontal coordinate, maximum horizontal coordinate, minimum vertical coordinate and maximum vertical coordinate; and obtaining the minimum enclosing rectangle corresponding to the stack in the XOY plane of the base coordinate system based on the minimum horizontal coordinate, maximum horizontal coordinate, minimum vertical coordinate and maximum vertical coordinate.

[0075] Furthermore, calculating the angle between the first straight line and the second straight line based on the coordinates of the tangent corner point in the XOY plane of the base coordinate system may include: determining a third straight line passing through the center point of the first joint and conforming to the Y axis of the base coordinate system in a reference posture; determining the distance between the third straight line and the first straight line in the reference posture; and calculating the angle between the first straight line and the second straight line based on the distance between the third straight line and the first straight line and the coordinates of the tangent corner point in the XOY plane of the base coordinate system.

[0076] Among them, when the stack type is located on the left side of the robot arm, that is, when calculating the angle safety range of the first joint corresponding to the movement of the robot arm from the left side to the initial posture, the preset connecting rod is the second connecting rod (big arm tube); when the stack type is located on the right side of the robot arm, that is, when calculating the angle safety range of the first joint corresponding to the movement of the robot arm from the right side to the initial posture, the preset connecting rod is the third connecting rod (small arm tube). The following is an example of the second connecting rod.

[0077] The first connecting rod refers to the line connecting the center point of the first joint and the center point of the second joint of the robotic arm.

[0078] Specifically, first, the robot arm is controlled to rotate in the initial position until the first link is perpendicular to the Y axis of the base coordinate system and stops. At this time, the robot arm is in the reference position, and the reference angle α of the first joint in this position is determined. base (For example 90.19 degrees).

[0079] Next, calculate the representation of the minimum enclosing rectangle corresponding to the stack type in the XOY plane of the base coordinate system. Figure 4 As shown in the figure, according to the center point of each material box in a certain layer of the stack, as well as the length and width of the material box, the coordinates of the four corner points of each box under the projection of the base coordinate system XOY plane can be calculated, and then the collection of all corner point coordinates is traversed and sorted to filter out the minimum and maximum horizontal and vertical coordinates: min 、x max ,y min and max , where the x and y values ​​are combined in pairs to get the coordinates of each corner point of the minimum enclosing rectangle. For example, point A is (x min ,y min ), point B is (x max ,y min ), point C is (x max ,y max ), point D is (x min ,y max ).

[0080] Then, we need to combine the structural parameters of the robot arm to determine when the robot arm is in the reference position, that is, the first joint angle is α base At this moment, the first straight line L formed by the projection of the outermost edge of the second connecting rod (big arm tube) on the XOY plane of the base coordinate system link2 , and there is a third straight line L passing through the center point of the first joint joint1Center Fit with the Y axis of the base coordinate system, that is, the third straight line L joint1Center The distance from the Y axis is X joint1Center =0, such as Figure 5 As shown, L link2 With L joint1Center Parallel, for the robot arm, the distance between the two is constant, for example, L can be calculated link2 The mathematical representation of X link2 =334(L link2 The distance from the Y axis). Then no matter how the robot arm rotates, the value of the distance between the two lines is always 334 in different postures.

[0081] After calculating the above parameters, the robot arm is controlled to rotate in the reference position, and the straight line formed by the projection of the outermost edge of the second link on the XOY plane is monitored in real time until the straight line is tangent to a corner point of the minimum enclosing rectangle, and the straight line is called the second straight line L′ link2 The tangent angle is called the tangent corner point, and the coordinates of the tangent corner point in the XOY plane of the base coordinate system are determined.

[0082] It should be noted that in order to ensure that the second straight line does not interfere with the minimum enclosing rectangle when it is tangent to the tangent corner point, the coordinates of the tangent corner point in the XOY plane of the base coordinate system are:

[0083]

[0084] Among them, x min Indicates the minimum horizontal coordinate, y min Indicates the minimum ordinate, x max Indicates the maximum horizontal coordinate. That is, when y min ≤0, the tangent point is point A (x min ,y min ), when y min >0, select the tangent point as point B (x max ,y min ).

[0085] It should be noted that the coordinates of the above tangent corner points are based on the X and Y directions of the base coordinate system (the base coordinate system takes the center of the robot base as the origin, the positive direction of the X axis of the base coordinate system is toward the left side of the robot, and the positive direction of the Y axis of the base coordinate system is toward the rear of the robot). In the embodiment of the present invention, the base coordinate direction can also be other directions. The calculation method of the coordinates of the tangent corner points in different base coordinate systems is the same, but the final expression method may change adaptively. For example, when the base coordinate system takes the center of the robot base as the origin, the positive direction of the X axis of the base coordinate system is toward the front of the robot, and the positive direction of the Y axis of the base coordinate system is toward the left side of the robot, the coordinates of the tangent corner point in the base coordinate system are:

[0086]

[0087] After calculating the third straight line L joint1Center With the first straight line L link2 After calculating the distance between the two and the coordinates of the tangent corner point, calculate the first straight line L based on the distance and coordinates. link2 With the second straight line L link2 The angle α between left .

[0088] like Figure 6 As shown, in the X and Y directions of the base coordinate system, Figure 6The first black dotted line from left to right is the projection of the outermost edge of the second connecting rod (big arm tube) in the tangent position in the XOY plane of the base coordinate system, that is, the second straight line L′ link2 , the second black dotted line represents the straight line L′ passing through the center point of the first joint and parallel to the second straight line joint1Center , the first black solid line is the first joint angle α base The projection representation of the first straight line L link2 , the second black solid line is the third straight line L joint1Center When the second straight line L′ link2 When it is tangent to the corner point A of the minimum enclosing rectangle, we can obtain L′ by the property that the two lines are parallel. link With L link2 The angle value and L′ joint1Center With L joint1Center The angle values ​​are equal, both are α left , α left The specific value of can be obtained by inverse tangent calculation, L′ link2 and L′ link2 For example, from Figure 6 It can be seen that the known tangent angle point A is expressed in the base coordinate system XOY plane as (x min ,y min ), then L′ is calculated by the following formula link2 With L link2 The angle between them (the base coordinate system takes the center of the robot base as its origin, the positive direction of the X axis of the base coordinate system is toward the left side of the robot, and the positive direction of the Y axis of the base coordinate system is toward the rear of the robot):

[0089]

[0090] Δx=x min

[0091] Δy=y min

[0092] Among them, α left It represents the angle between the first straight line and the second straight line when the stack is on the left side of the robot arm, x min Indicates the minimum horizontal coordinate, y min represents the minimum ordinate, distance represents the distance between the third straight line and the first straight line, Δx and Δy represent the distance between the tangent corner point and the Y axis and X axis of the base coordinate system respectively.

[0093] Therefore, if you want the lifting column to move during the left-side palletizing operation without interference between the robot arm and the pallet shape, then the safety angle range of the first joint when the robot arm moves from the left side to the initial position is [α base ,α base +α left], where α is generally base +α left Greater than or equal to α_init+β_left, that is, the safe angle range obtained by calculation is greater than the safe angle range obtained by estimation.

[0094] For the calculation of the safe angle range of the corresponding first joint when the robot arm moves from the right side to the initial position, you only need to pay attention to changing the outer edge of the above-mentioned large arm tube to the outer edge of the small arm tube. The other calculation derivation steps are the same and will not be described again.

[0095] Finally, it is calculated that when the stack is located on the left side of the robot arm, that is, when the robot arm moves from the left side to the initial position, the safe angle range of the first joint is [α base , α base +α left ], where α base is the reference angle, α left is the angle between the first straight line and the second straight line when the stack is on the left side of the robot; when the stack is on the right side of the robot, that is, when the robot moves from the right side to the initial position, the safety angle range of the first joint is [-α right +α base , α base ], where α base is the reference angle, α right It is the angle between the first straight line and the second straight line when the stack is located on the right side of the robot arm.

[0096] That is to say, the final result obtained by calculation is Figure 3 The range of the minor arc angle α_def between the two rays in is [-α right +α base , α base +α left ], α base , α left and α right Both are greater than 0 degrees.

[0097] In summary, obtaining the safe angle range of the first joint angle by estimation has the advantages of being simple and efficient, and can adapt to the general situation where the stack type does not exceed the pallet pallet. However, if the filling utilization rate of the pallet pallet is low, the estimated safe angle range limit of the first joint will appear to be a waste of performance; if the pallet type exceeds the edge of the pallet pallet, the estimated safe angle range of the first joint may still have the risk of collision. In order to avoid it, the safe angle range of the first joint can only be restricted more tightly, and the problem of performance waste is more obvious. By comparison, the calculation method to obtain the safe angle range of the first joint angle is automatically calculated according to the box size and the stack type, and dynamically transformed. On the premise of ensuring no collision, it obtains more movement time, improves rhythm and flexibility, and is more superior.

[0098] In one embodiment of the present invention, judging whether to start the control of the lifting column based on the safety range in step S2 may include: obtaining the angle of the first joint of the robot arm; if the angle of the first joint of the robot arm is within the safety angle range, determining to start the control of the lifting column; if the angle of the first joint of the robot arm is not within the safety angle range, determining not to start the control of the lifting column. Specifically, when the stacking of the last material of the stack type on either side of the robot is completed, the robot arm is controlled to move, and the first joint angle is monitored in real time. When the angle reaches the safety angle range, the lifting column is controlled to descend, while the robot arm is kept moving until the lifting column descends to zero position and the robot arm moves to the initial position. When the angle does not reach the safety angle range, only the robot arm is controlled to move, and the lifting column is not controlled to move. The lifting column is controlled to descend only when the angle reaches the safety angle range.

[0099] like Figure 7 As shown, it is assumed that the robot arm has finished stacking the last material of the stack on the left, and its end is located at the discharge point W. It is ready to return from the discharge point W (above the stack) to the material collection point U above the conveyor belt to start a new round of palletizing operations on the right. In this path, according to the above strategy of the embodiment of the present invention, non-blocking axial motion will be used to move from point W to point U. During this period, the angle of the first joint of the robot arm can be obtained in real time to determine whether the value of the first joint angle is within the safe angle range. For the first joint, when the first joint rotates clockwise by an angle of β (less than or equal to α_init+β_left, equal to α base +α left ), will be located at point W1, just within the safe angle range or at the extreme point of the safe angle range, at this time, the condition that the value of the first joint angle is within the safe angle range is met. For the lifting column, when the end of the robot arm moves from point W1 to point U, it can start to descend to the zero position. For the robot arm, the robot arm continues to move from point W to point U.

[0100] Therefore, within the first joint angle range that ensures safety, the robot arm can perform safe non-blocking movement and achieve smooth and continuous movement with the lifting column, which not only ensures safe coordinated movement but also improves the overall rhythm of the production line.

[0101] In summary, the embodiments of the present invention propose a universal and highly feasible solution to the difficulties related to the palletizing process of the collaborative robot, optimize the coordinated movement of the robot arm and the lifting column, maximize the use of and give full play to the improvement of the overall performance of the collaborative robot after the installation of the lifting column, increase the continuity of movement, and greatly improve the overall palletizing efficiency.

[0102] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0103] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0104] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention belong.

[0105] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0106] A person of ordinary skill in the art can understand that all or part of the steps carried by the method of the above-mentioned embodiment can be completed by instructing the relevant hardware through a program, and the program can be stored in a computer-readable storage medium, and the program, when executed, includes one or a combination of the steps of the method embodiment. In addition, each functional unit in each embodiment of the present invention can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into one module. The above-mentioned integrated module can be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0107] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for controlling a collaborative robot in a palletizing process, characterized in that: The collaborative robot comprises a mechanical arm and a lifting column, wherein the lifting column is mounted on the lower surface of a mechanical arm base, and the method comprises the following steps: Determine the safety range of the robotic arm, wherein the safety range refers to the range of motion of the robotic arm when the lifting column descends to drive the robotic arm to move without the robotic arm colliding with the pallet plates and the stacking type on its left and right sides; When the palletizing of the last material of the pallet is completed, the robot arm is controlled to move and at the same time, it is determined whether to start the control of the lifting column based on the safety range. If yes, the lifting column is controlled to descend to the zero position while the robot arm is controlled to keep moving. The safety range of the robotic arm includes the safety angle range of the first joint of the robotic arm. Determining the safety range of the robotic arm includes: Determining an initial position of the robotic arm, wherein the center of the robotic arm flange is located directly in front of the robotic arm in the initial position; Based on the initial posture, the robot arm is controlled to move and a safe angle range of the first joint of the robot arm is determined based on the motion state. include: Determine the maximum projection between the vertical projection of the pallet plate on the XOY plane of the base coordinate system and the vertical projection of the stack type on the pallet plate on the XOY plane of the base coordinate system; Determining an initial angle of the first joint of the robotic arm in the initial position; Controlling the first joint of the robotic arm to rotate from the initial angle until the vertical projection of the robotic arm on the XOY plane of the base coordinate system is tangent to the maximum projection, and recording the rotation angle of the first joint; A safe angle range of the first joint of the robotic arm is obtained according to the initial angle and the rotation angle.

2. The control method for a collaborative robot in a palletizing process according to claim 1, characterized in that: Controlling the first joint of the robotic arm to rotate from the initial angle until the vertical projection of the robotic arm on the XOY plane of the base coordinate system is tangent to the maximum projection, and recording the rotation angle of the first joint, including: Control the first joint of the robotic arm to rotate counterclockwise from the initial angle until the vertical projection of the robotic arm on the XOY plane of the base coordinate system is tangent to the maximum projection, and record the counterclockwise rotation angle of the first joint; The first joint of the robotic arm is controlled to rotate clockwise from the initial angle until the vertical projection of the robotic arm on the XOY plane of the base coordinate system is tangent to the maximum projection, and the clockwise rotation angle of the first joint is recorded.

3. The control method for a collaborative robot in a palletizing process according to claim 2, characterized in that: When the pallet and the stack are located on the left side of the robot arm, the safety angle range of the first joint is ,in, is the initial angle, is the counterclockwise rotation angle; When the pallet and the stack are located on the right side of the robot arm, the safety angle range of the first joint is ,in, is the clockwise rotation angle, , and Both are greater than 0 degrees.

4. The control method for a collaborative robot in a palletizing process according to claim 1, characterized in that: Based on the initial posture, controlling the movement of the robotic arm and determining a safe angle range of the first joint of the robotic arm based on the movement state includes: Control the robot arm to rotate to a reference posture in the initial posture, wherein the first link of the robot arm is perpendicular to the Y axis of the base coordinate system in the reference posture, and determine a reference angle of the first joint in the reference posture and a first straight line formed by the projection of the outermost edge of the preset link on the XOY plane of the base coordinate system, wherein the preset link is the second link or the third link; Determine the minimum enclosing rectangle corresponding to the stack type in the XOY plane of the base coordinate system; Controlling the robot arm to rotate to a tangent posture in the reference posture, wherein a second straight line formed by the projection of the outermost edge of the preset connecting rod on the XOY plane of the base coordinate system in the tangent posture is tangent to a corner point of the minimum enclosing rectangle, and determining the coordinates of the tangent corner point in the XOY plane of the base coordinate system in the tangent posture; Calculating the angle between the first straight line and the second straight line based on the coordinates of the tangent corner point in the XOY plane of the base coordinate system; The safe angle range of the first joint of the robotic arm is calculated according to the reference angle and the angle between the first straight line and the second straight line.

5. The control method for a collaborative robot in a palletizing process according to claim 4, characterized in that: Determining the minimum enclosing rectangle corresponding to the stack type in the XOY plane of the base coordinate system includes: Determine the coordinates of each corner point of any layer of boxes in the stack under the projection of the base coordinate system XOY plane; Traverse and sort the coordinates of all corner points, and filter out the minimum horizontal coordinate, maximum horizontal coordinate, minimum vertical coordinate, and maximum vertical coordinate; According to the minimum horizontal coordinate, the maximum horizontal coordinate, the minimum vertical coordinate and the maximum vertical coordinate, the minimum enclosing rectangle corresponding to the stack type in the XOY plane of the base coordinate system is obtained.

6. The control method for a collaborative robot in a palletizing process according to claim 5, characterized in that: The base coordinate system takes the center of the robot base as its origin, the positive direction of the X axis of the base coordinate system faces the left side of the robot, and the positive direction of the Y axis of the base coordinate system faces the rear side of the robot. The coordinates of the tangent corner point in the XOY plane of the base coordinate system are: ， in, represents the minimum horizontal coordinate, represents the minimum ordinate, represents the maximum abscissa.

7. The control method for a collaborative robot in a palletizing process according to claim 6, characterized in that: Calculating the angle between the first straight line and the second straight line based on the coordinates of the tangent corner point in the XOY plane of the base coordinate system includes: Determine a third straight line passing through the center point of the first joint and fitting with the Y axis of the base coordinate system under the reference posture; determining a distance between the third straight line and the first straight line in the reference posture; The angle between the first straight line and the second straight line is calculated according to the distance between the third straight line and the first straight line and the coordinates of the tangent angle point in the XOY plane of the base coordinate system.

8. The method for controlling a collaborative robot in a palletizing process according to claim 7, characterized in that: The angle between the first straight line and the second straight line is calculated by the following formula: , in, represents the angle between the first straight line and the second straight line, Indicates the minimum horizontal coordinate, represents the minimum ordinate, represents the distance between the third straight line and the first straight line, , Respectively represent the distance between the tangent corner point and the Y-axis and X-axis of the base coordinate system.

9. The method for controlling a collaborative robot in a palletizing process according to any one of claims 4 to 8, characterized in that: When the stack type is located on the left side of the robotic arm, the preset connecting rod is the second connecting rod; when the stack type is located on the right side of the robotic arm, the preset connecting rod is the third connecting rod.

10. The control method for a collaborative robot in a palletizing process according to any one of claims 4 to 8, characterized in that: When the stack is located on the left side of the robot arm, the safety angle range of the first joint is ,in, is the base angle, is the angle between the first straight line and the second straight line when the stack is located on the left side of the robot arm, , All are greater than 0 degrees; When the stack is located on the right side of the robot arm, the safety angle range of the first joint is ,in, is the base angle, is the angle between the first straight line and the second straight line when the stack is located on the right side of the robot arm, Greater than 0 degrees.

11. The control method for a collaborative robot in a palletizing process according to claim 1, characterized in that: Determining whether to start controlling the lifting column based on the safety range includes: Obtaining the angle of the first joint of the robotic arm; If the angle of the first joint of the mechanical arm is within the safety angle range, determining to start the control of the lifting column; If the angle of the first joint of the robot arm is not within the safety angle range, it is determined not to start the control of the lifting column.

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