CN117842713A - Control method of collaborative robot in palletizing process - Google Patents

Abstract

The invention provides a control method for a cooperative robot in a stacking process, wherein the cooperative robot comprises a mechanical arm and a lifting column, and the method comprises the following steps: determining the safety range of the mechanical arm, wherein the safety range refers to the movement range 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 and the stack type pallet at the left side and the right side of the mechanical arm; when stacking of the last material of the stack is completed, the mechanical arm is controlled to move, meanwhile, whether the control of the lifting column is started or not is judged based on the safety range, and if so, the lifting column is controlled to descend to a zero position while the mechanical arm is controlled to keep moving. Therefore, when the last material of the stacking is completed, the lifting column is controlled to descend based on the safety range of the mechanical arm, the cooperative movement between the mechanical arm and the lifting column can be optimized while the safety is ensured, the action continuity is improved, and the overall stacking efficiency can be improved.

Description

Control method of collaborative robot in palletizing process

Technical Field

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 technique

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.

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

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 stacking efficiency, the present invention proposes the following technical solution.

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 the method comprises the following steps: determining a safety range of the robotic arm, wherein the safety range refers to the range of movement 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.

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.

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.

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.

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.

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.

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.

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.

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.

According to one embodiment of the present invention, 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.

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

Among them, x _min represents the minimum horizontal coordinate, y _min represents the minimum vertical coordinate, and x _max represents the maximum horizontal coordinate.

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.

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:

Δx＝x _min

Δy＝ _ymin

Among them, α _left represents the angle between the first straight line and the second straight line, x _min represents the minimum horizontal coordinate, y _min represents the minimum vertical coordinate, 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.

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.

According to one embodiment of the present invention, when the stack is located on the left side of the robotic arm, the safety angle range of the first joint is [α _base , α _base +α _left ], wherein α _base is a reference angle, α _left is an angle between the first straight line and the second straight line when the stack is located on the left side of the robotic arm, and α _base and α _left are both greater than 0 degrees; when the stack is located on the right side of the robotic arm, the safety angle range of the first joint is [-α _right +α _base , α _base ], wherein α _base is a reference angle, α _right is an angle between the first straight line and the second straight line when the stack is located on the right side of the robotic arm, and α _right is greater than 0 degrees.

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.

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.

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

FIG. 1 is a flow chart of a method for controlling a collaborative robot in a palletizing process according to an embodiment of the present invention.

FIG. 2 is a schematic structural diagram of a collaborative robot arm according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of a safe angle range of a first joint according to an embodiment of the present invention.

FIG. 4 is a schematic diagram of calculating a minimum enclosing rectangle according to an example of the present invention.

FIG5 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.

FIG. 6 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.

FIG. 7 is a schematic diagram of a safe angle range of using a first joint according to an embodiment of the present invention.

Detailed ways

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.

FIG. 1 is a flow chart of a method for controlling a collaborative robot in a palletizing process according to an embodiment of the present invention.

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.

As shown in FIG. 1 , the control method for the collaborative robot in the palletizing process includes the following steps S1 and S2.

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.

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

S1, determine the safety range of the robot arm, wherein 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.

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

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

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.

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.

The 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 the zero position.

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 is descending. 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.

In actual applications, when 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 in 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.

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.

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.

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.

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.

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.

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).

As shown in Figure 3, assuming that the right and left sides of the collaborative robot have the same type of stack (stacks are stacked on a pallet), when the angle of the first joint of the robot body is between the two rays shown in Figure 3, it can be ensured that when the lifting column moves downward, the robot body and the stacks of materials on the left and right sides and the pallet 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 stacks of materials on the left and right sides and the pallet, and the inferior arc angle α_def between the two rays is the safe angle range of the first joint.

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 position of the robot arm.

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.

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 after stopping. 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.

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 motion parameters.

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.

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.

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

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.

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.

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 under the initial posture.

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.

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.

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

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.

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

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.

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.

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.

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.

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.

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.

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 _base (for example, 90.19 degrees) of the first joint in this position is determined.

Next, the representation of the minimum enclosing rectangle corresponding to the stack in the base coordinate system XOY plane is calculated. As shown in Figure 4, based on 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 in 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 select the minimum and maximum horizontal and vertical coordinates: x _min , x _max , y _min and y _max , where the x and y values are combined in pairs to obtain the coordinate representation 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 ), and point D is (x _min , y _max ).

Then, it is necessary to combine the structural parameters of the robot arm to determine that when the robot arm is in the base posture, that is, when the first joint angle is α _base , the first straight line L _link2 formed by the projection of the outermost edge of the second link (large arm tube) on the XOY plane of the base coordinate system, and at the same time, there is a third straight line L _joint1Center passing through the center point of the first joint that fits the Y axis of the base coordinate system, that is, the distance between the third straight line L _joint1Center and the Y axis is X _joint1Center = 0. As shown in Figure 5, L _link2 is parallel to L _joint1Center . For the robot arm, the distance between the two is constant. For example, the mathematical expression of L _link2 can be calculated as X _link2 = 334 (the distance of L _link2 from the Y axis). Then no matter how the robot arm rotates, the value of the distance between the two straight lines is always 334 under different postures.

After calculating the above parameters, the robot arm is controlled to rotate in the reference posture, 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. 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.

It should be noted that in order to ensure that when the second straight line is tangent to the tangent corner point, the second straight line and the minimum enclosing rectangle do not interfere with each other, the coordinates of the tangent corner point in the XOY plane of the base coordinate system are:

Among them, x _min represents the minimum horizontal coordinate, y _min represents the minimum vertical coordinate, and x _max represents the maximum horizontal coordinate. That is, when y _min ≤ 0, the tangent point is point A (x _min , y _min ), and when y _min > 0, the tangent point is point B (x _max , y _min ).

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:

After calculating the distance distance between the third straight line L _joint1Center and the first straight line L _link2 and the coordinates of the tangent corner point, the angle α _left between the first straight line L _link2 and the second straight line L _link2 is calculated according to the distance distance and the coordinates.

As shown in FIG6 , in the X and Y directions of the base coordinate system, the first black dotted line from left to right in FIG6 is the projection representation of the outermost edge of the second link (big arm tube) in the tangent posture 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′ _joint1Center passing through the center point of the first joint and parallel to the second straight line at this time, the first black solid line is the projection representation when the first joint angle is α _base , that is, the first straight line L _link2 , and the second black solid line is the third straight line L _joint1Center . When the second straight line L′ _link2 is tangent to the corner point A of the minimum enclosing rectangle, the property of the two straight lines being parallel can be used to obtain that the angle between L′ _link and L _link2 is equal to the angle between L′ _joint1Center and L _joint1Center , both of which are α _left . The specific value of α _left can be obtained by inverse tangent calculation. Taking L′ _link2 and L′ _link2 as an example, it can be seen from Figure 6 that the expression of the tangent corner point A in the XOY plane of the base coordinate system is known to be (x _min ,y _min ), then the angle between L′ _link2 and L _link2 is calculated by the following formula (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):

Δx＝x _min

Δy＝ _ymin

Wherein, α _left represents 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, x _min represents the minimum horizontal coordinate, y _min represents the minimum vertical coordinate, 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.

Therefore, if you want the lifting column to move during left-side palletizing without interference between the robot arm and the pallet shape, then the safe angle range of the corresponding first joint when the robot arm moves from the left side to the initial position is [α _base ,α _base +α _left ], where generally speaking, α _base +α _left is 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.

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.

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

That is to say, the range of the minor arc angle α_def between the two rays in FIG. 3 finally obtained by calculation is [-α _right +α _base , α _base +α _left ], and α _base , α _left and α _right are all greater than 0 degree.

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.

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.

As shown in FIG7 , 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, and is ready to return from the discharge point W (above the stack) to the material collection point U above the conveyor belt to perform a new round of stacking operations on the right. In this path, according to the above-mentioned 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 ), it will be located at point W1, which is exactly 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 zero. For the robot arm, the robot arm moves continuously from point W to point U.

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

To summarize, the embodiments of the present invention address the difficulties associated with the palletizing process of the collaborative robot and propose a universal and highly feasible solution, which optimizes the coordinated movement of the robot arm and the lifting column, maximizes the use of and gives full play to the improvement in the overall performance of the collaborative robot after the installation of the lifting column, increases the continuity of movement, and greatly improves the overall palletizing efficiency.

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.

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, without contradiction.

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.

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.

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.

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 (14)

1. The control method for the cooperative robot in the stacking process is characterized in that the cooperative robot comprises a mechanical arm and a lifting column, wherein the lifting column is arranged on the lower surface of a mechanical arm base, and the method comprises the following steps:

determining a safety range of the mechanical arm, wherein the safety range refers to a movement range of the mechanical arm when the lifting column descends to drive the mechanical arm to move and the mechanical arm, the pallet pallets on the left side and the right side of the mechanical arm and the stacking type of the mechanical arm do not collide;

when stacking of the last material of the stack type is completed, controlling the mechanical arm to move, judging whether to start controlling the lifting column based on the safety range, and if so, controlling the mechanical arm to keep moving and simultaneously starting controlling the lifting column to descend to a zero position.

2. A method of controlling a co-robot in a palletising process according to claim 1, wherein the safety range of the robotic arm comprises the safety angular range of the first joint of the robotic arm.

3. A method of controlling a co-robot in a palletising process according to claim 2, wherein determining the safety range of the robotic arm comprises:

determining an initial pose of the mechanical arm, wherein the center of a flange of the mechanical arm is positioned right in front of the mechanical arm under the initial pose;

and controlling the mechanical arm to move on the basis of the initial pose and determining the safety angle range of the first joint of the mechanical arm based on the movement state.

4. A method of controlling a co-robot in a palletising process according to claim 3, wherein controlling the movement of the robotic arm and determining the safe angular range of the first joint of the robotic arm based on the initial pose comprises:

determining the maximum projection between the vertical projection of the pallet on the base coordinate system XOY plane and the vertical projection of the stack on the pallet on the base coordinate system XOY plane;

determining an initial angle of a first joint of the mechanical arm in the initial pose;

controlling the first joint of the mechanical arm to rotate from the initial angle until the perpendicular projection of the mechanical arm on the basis coordinate system XOY plane is tangent to the maximum projection, and recording the rotation angle of the first joint;

And obtaining the safety angle range of the first joint of the mechanical arm according to the initial angle and the rotation angle.

5. A method of controlling a co-robot in a palletizing process according to claim 4, wherein controlling the rotation of the first joint of the mechanical arm from the initial angle until the perpendicular projection of the mechanical arm on the base coordinate system XOY plane is tangential to the maximum projection, recording the rotation angle of the first joint comprises:

controlling the first joint of the mechanical arm to rotate anticlockwise from the initial angle until the perpendicular projection of the mechanical arm on the basis coordinate system XOY plane is tangent to the maximum projection, and recording the anticlockwise rotation angle of the first joint;

and controlling the first joint of the mechanical arm to rotate clockwise from the initial angle until the perpendicular projection of the mechanical arm on the basis coordinate system XOY plane is tangent to the maximum projection, and recording the clockwise rotation angle of the first joint.

6. A method of controlling a co-robot in a palletizing process as claimed in claim 5, wherein,

when the pallet and the stack are positioned on the left side of the mechanical arm, the safety angle range of the first joint is [ alpha_init, alpha_init+beta_left ], wherein alpha_init is an initial angle, and beta_left is a counterclockwise rotation angle;

When the pallet and the stack are positioned on the right side of the mechanical arm, the safety angle range of the first joint is [ alpha_init-beta_right, alpha_init ], wherein beta_right is a clockwise rotation angle, and alpha_init, beta_left and beta_right are all larger than 0 degree.

7. A method of controlling a co-robot in a palletising process according to claim 3, wherein controlling the movement of the robotic arm and determining the safe angular range of the first joint of the robotic arm based on the initial pose comprises:

controlling the mechanical arm to rotate to a reference pose under the initial pose, wherein a first connecting rod of the mechanical arm under the reference pose is vertical to a Y axis of a base coordinate system, and determining a reference angle of the first joint under the reference pose and a first straight line formed by projection of the outermost edge of a preset connecting rod on an XOY plane of the base coordinate system, wherein the preset connecting rod is a second connecting rod or a third connecting rod;

determining a minimum bounding rectangle corresponding to the stack type on a base coordinate system XOY plane;

controlling the mechanical arm to rotate to a tangent pose under the reference pose, wherein a second straight line formed by projection of the outermost edge of the preset connecting rod on a base coordinate system XOY plane under the tangent pose is tangent to one corner point of the minimum bounding rectangle, and determining the coordinate of the tangent corner point on the base coordinate system XOY plane under the tangent pose;

Calculating an included angle between the first straight line and the second straight line based on the coordinates of the tangent angular point on a basic coordinate system XOY plane;

and calculating according to the reference angle and the included angle between the first straight line and the second straight line to obtain the safety angle range of the first joint of the mechanical arm.

8. The method for controlling a cooperative robot in a palletizing process according to claim 7, wherein determining a minimum bounding rectangle corresponding to the palletizing in a base coordinate system XOY plane comprises:

determining the coordinates of each corner point of any layer of boxes of the stack under the projection of a base coordinate system XOY plane;

traversing and sorting coordinates of all the angular points, and screening out a minimum abscissa, a maximum abscissa, a minimum ordinate and a maximum ordinate;

and obtaining a minimum bounding rectangle corresponding to the stack in the base coordinate system XOY plane according to the minimum abscissa, the maximum abscissa, the minimum ordinate and the maximum ordinate.

9. The method for controlling a cooperative robot in a palletizing process according to claim 8, wherein the base coordinate system uses the center of the manipulator base as an origin, the positive X-axis direction of the base coordinate system is directed to the right left side of the manipulator, the positive Y-axis direction of the base coordinate system is directed to the right rear side of the manipulator,

The coordinates of the tangential corner points on the base coordinate system XOY plane are as follows:

wherein x is _min Representing the minimum abscissa, y _min Representing the minimum ordinate, x _max Representing the maximum abscissa.

10. The method for controlling a cooperative robot in a palletizing process according to claim 9, wherein calculating an included angle between the first straight line and the second straight line based on coordinates of the tangent corner point in a base coordinate system XOY plane includes:

determining a third straight line which passes through the center point of the first joint and is attached to the Y axis of the base coordinate system under the reference pose;

determining a distance between the third line and the first line in the reference pose;

and calculating an included 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 angular point on the base coordinate system XOY plane.

11. The method of claim 10, wherein the angle between the first line and the second line is calculated by the following formula:

Δx＝x _min

Δy＝y _min

wherein alpha is _left Represents the included angle between the first straight line and the second straight line, x _min Representing the minimum abscissa, y _min And the distance represents the distance between the third straight line and the first straight line, and Deltax and Deltay represent the distances between the tangent corner point and the Y axis and the X axis of the base coordinate system respectively.

12. A method of controlling a co-operative robot in a palletising process according to any one of claims 7 to 11, wherein the predetermined link is a second link when the stack is located to the left of the robotic arm; when the stack type is positioned on the right side of the mechanical arm, the preset connecting rod is a third connecting rod.

13. Method for controlling a co-operating robot in a palletising process according to any of the claims 7-11, characterized in that,

when the stack is positioned on the left side of the mechanical arm, the safety angle range of the first joint is [ alpha ] _base ，α _base +α _left ]Wherein alpha is _base As a reference angle alpha _left For the included angle between the first straight line and the second straight line when the stack is positioned at the left side of the mechanical arm, alpha _base 、α _left All greater than 0 degrees;

when the stack is positioned on the right side of the mechanical arm, the safety angle range of the first joint is [ -alpha [ _right +α _base ，α _base ]Wherein alpha is _base As a reference angle alpha _right For the included angle between the first straight line and the second straight line when the stack is positioned on the right side of the mechanical arm, alpha _right Greater than 0 degrees.

14. The method for controlling a cooperative robot in a palletizing process according to claim 2, wherein determining whether to start the control of the lifting column based on the safety range comprises:

acquiring an angle of a first joint of the mechanical arm;

if the angle of the first joint of the mechanical arm is within the safe angle range, determining to start control of the lifting column;

and if the angle of the first joint of the mechanical arm is not in the safe angle range, determining that the control of the lifting column is not started.