Robot system

Abstract

To provide a robot system having two arms and capable of stably picking a workpiece at high speed even if the total weight and the size are small.SOLUTION: The robot system 1 includes a first robot 3 and a second robot 4, a main body 2 on which the first robot 3 and the second robot 4 are installed, and a control device 5 that controls operations of the first robot 3 and the second robot 4. The control device 5 calculates a first angular moment TF1 acting on the overturning fulcrum P of the main body 2 by the operation of the first arm 32 related to the first robot 3, a second angular moment TF2 acting on the overturning fulcrum P of the main body 2 by the operation of the second arm 42 related to the second robot 4, and a third angular moment TG acting on the overturning fulcrum P of the main body 2 by gravity. Then, the control device 5 performs control to prevent the main body 2 from falling down based on the values of the first angular moment TF1, the second angular moment TF2, and the third angular moment TG.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a robot system having two arms. [Background technology]

[0002] Conventionally, there has been known a robot system equipped with two arms for the purpose of automating operations such as serving food and loading. For example, Patent Document 1 discloses an automated guided vehicle equipped with a dual-arm robot. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-090749 Summary of the Invention [Problem to be solved by the invention]

[0004] For an automated guided vehicle, it is desirable to have as small a total weight and size as possible, provided that the performance is the same. However, an automated guided vehicle with a small total weight and size will have reduced stability. In particular, when picking distant or heavy workpieces, there is a risk of the vehicle tipping over if it is operated at high speed.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and its purpose is to provide a robot system that has two arms and can pick up workpieces quickly and stably, even though the total weight and size are small. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the present invention provides a robot system comprising a first robot and a second robot, a main body on which the first robot and the second robot are mounted, and a control device that controls the operation of the first robot and the second robot, wherein the control device calculates a first rotational moment that acts on the tipping fulcrum of the main body due to the operation of a first arm associated with the first robot, a second rotational moment that acts on the tipping fulcrum of the main body due to the operation of a second arm associated with the second robot, and a third rotational moment that acts on the tipping fulcrum of the main body due to gravity, and performs control to prevent the main body from tipping based on the values ​​of the first rotational moment, the second rotational moment, and the third rotational moment.

[0007] When the first robot extends the first arm outside the main body and performs an operation of pulling the first arm toward the main body while grasping a workpiece with a first hand associated with the first robot, the control device may control the first arm to be pulled toward the main body and the second arm to be accelerated in a direction symmetrical to the direction in which the first arm is pulled.

[0008] Furthermore, when the first robot extends the first arm away from the main body and performs an action of pulling the first arm toward the main body while holding a workpiece with the first hand of the first robot, the control device may control the second arm to extend away from the main body before starting the action of pulling the first arm toward the main body, and may control the second arm to decelerate the action of extending away from the main body after starting the action of pulling the first arm toward the main body. [Effects of the Invention]

[0009] The present invention provides a robot system that has two arms and is capable of picking up workpieces quickly and stably, even though the total weight and size are small. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a plan view showing the overall configuration of a robot system according to a first embodiment of the present invention; [Figure 2] Block diagram showing the hardware configuration of the robot system in Figure 1 [Figure 3] FIG. 3 is a diagram of the robot system seen from the direction III in FIG. 1 to explain the moment (torque) acting on the main body of FIG. 1. [Figure 4] 1 is a flowchart showing an example of a process flow realized by the control device of FIG. [Figure 5] FIG. 10 is a plan view illustrating the operation of the robot system according to the second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of the present invention will be described in detail below with reference to the drawings. The embodiment of the present invention relates to a robot system equipped with two arms. In the following, an automated guided vehicle (AGV) equipped with two arms will be used as an example. However, the present invention can also be applied to a robot system that does not move.

[0012] First Embodiment Fig. 1 is a plan view showing the overall configuration of a robot system according to a first embodiment of the present invention. As shown in Fig. 1, the robot system 1 includes a first robot 3 and a second robot 4, a main body 2 on which the first robot 3 and the second robot 4 are installed, and a control device 5 that controls the operations of the first robot 3 and the second robot 4. The first robot 3 and the second robot 4 may be a single dual-arm robot or a combination of two single-arm robots.

[0013] The main body 2 has a roughly rectangular parallelepiped shape with a front-to-rear direction, a left-to-right direction perpendicular to the front-to-rear direction, and a top-to-bottom direction perpendicular to the front-to-rear and left-to-right directions. The top surface 21 of the main body 2 has a roughly rectangular planar shape, forming a platform on which workpieces can be loaded, with a left front corner 22a, a right front corner 22b, a left rear corner 22c, and a right rear corner 22d. The main body 2 has a left front wheel 23a, a right front wheel 23b, a left rear wheel 23c, and a right rear wheel 23d at each of its four ends, respectively, and is an autonomously traveling automated guided vehicle. The drive system for autonomous traveling is not limited. The wheels may be omniwheels or crawlers, as long as they have a contact point with the floor surface. The number of wheels is not limited to four, but may be three, five, or more.

[0014] The first robot 3 includes a first base 31 installed in the left front corner 22a, a first arm 32 connected to the first base 31, and a first hand 33 attached to the first arm 32. The second robot 4 includes a second base 41 installed in the right front corner 22b, a second arm 42 connected to the second base 41, and a second hand 43 attached to the second arm 42. By installing the first robot 3 and the second robot 4 in the corners of the main body 2, the reach lengths of the first arm 32 and the second arm 42 can be effectively utilized. However, the installation locations of the first robot 3 and the second robot 4 are not limited.

[0015] The first arm 32 and the second arm 42 are configured with a link mechanism having multiple links, and have joints that connect the links. Each joint is provided with a drive motor (not shown). An example of the first robot 3 and the second robot 4 is a vertical multi-joint robot with six joints. However, the present invention is also applicable to robots with five or fewer or seven or more joints, horizontal multi-joint robots, etc. The first hand 33 and the second hand 43 have gripping units that grip a workpiece, such as a transported object.

[0016] The control device 5 is mounted inside the main body 2. There may be one or more control devices 5. In the case of more than one control device, the control devices 5 are connected to each other so that they can communicate with each other. In the following description, it is assumed that there is one control device 5, and that one control device 5 controls the operations of the main body 2, the first robot 3, and the second robot 4 as an automated guided vehicle.

[0017] 2 is a block diagram showing the hardware configuration of the robot system of FIG. 1. The main body 2 has an input / output interface 25, a sensor 26, and an actuator 27. The input / output interface 25 inputs signals from the control device 5 and outputs signals to the control device 5. The sensor 26 is, for example, a magnetic sensor or an optical sensor, and detects guide wires (not shown) formed on the floor surface, and outputs sensor data to the control device 5. The actuator 27 is, for example, a drive motor, and drives the wheels of the main body 2 in accordance with command signals from the control device 5. The sensor 26 and the actuator 27 are not limited to these examples.

[0018] The first robot 3 and the second robot 4 each have an input / output interface 34, 44, a sensor 35, 45, and an actuator 36, 46. The input / output interfaces 34, 44 input signals from the control device 5 and output signals to the control device 5. The sensors 35, 45 are, for example, encoders that detect the rotation speed and rotation angle of the drive motor of each rotation axis and output sensor data to the control device 5. The actuators 36, 46 are, for example, drive motors for the joints of the first arm 32 and the second arm 42 and the gripping parts of the first hand 33 and the second hand 43, and drive the joints and gripping parts in accordance with command signals from the control device 5. The sensors 35, 45 and the actuators 36, 46 are not limited to these examples.

[0019] The CPU (Central Processing Unit) 51, memory 52, auxiliary storage device 53, and input / output interface 54 of the control device 5 are connected via a bus 55. The CPU 51 reads a control program stored in advance in the auxiliary storage device 53 or the like into the memory 52 and sequentially executes a plurality of instructions. The auxiliary storage device 53 is a hard disk drive, a solid state drive, or the like, and stores data used in the processing described below. The input / output interface 54 inputs signals from the main body 2, the first robot 3, the second robot 4, and other devices, and outputs signals to them. Note that all or part of the functions of the control device 5 may be configured using logic circuits or analog circuits, and the processing of various programs may be configured using electronic circuits such as an FPGA (Field Programmable Gate Array).

[0020] Fig. 3 is a diagram of the robot system as seen from direction III in Fig. 1 to explain the moment (torque) acting on the main body of Fig. 1. In the example shown in Fig. 3, a workpiece 7 is placed on a table 6 on the left side of the robot system 1. Then, the first robot 3 extends the first arm 32 to the table 6 on the side away from the main body 2, and performs an operation to pull the workpiece 7 toward the main body 2 (hereinafter referred to as "pulling operation B") while grasping the workpiece 7 with the first hand 33 (hereinafter referred to as "grasping state A").

[0021] In the grasping state A, the center of gravity of the entire robot system 1 shifts to the left side of the main body 2, reducing the stability of the main body 2. Furthermore, when a pulling motion B is performed in the grasping state A and a force F1 is applied in the direction of the main body 2, the reaction force F1 further reduces the stability of the main body 2, increasing the possibility that the main body 2 will tilt to the left and tip over.

[0022] In the example shown in FIG. 3, the tipping fulcrum P of the main body 2 to the left is the contact point between the left front wheel 23a and the left rear wheel 23c and the floor. The rotational moment acting on the tipping fulcrum P due to the force F1 associated with the operation of the first robot 3 is defined as TF1. The rotational moment acting on the tipping fulcrum P due to gravity is defined as TG. The weight of the workpiece 7 and first hand 33 is defined as M1. The weight of the second hand 43 is defined as M2. The total weight of the main body 2, first base 31, first arm 32, second base 41, second arm 42, and control device 5 is defined as M3. The left-right distance from the tipping fulcrum P to the center of gravity of the workpiece 7 and first hand 33 is defined as L1. The left-right distance from the tipping fulcrum P to the center of gravity of the second hand 43 is defined as L2. The horizontal distance from the tipping fulcrum P to the center of gravity of the main body 2, first base 31, first arm 32, second base 41, second arm 42, and control device 5 is defined as L3. The vertical distance from the tipping fulcrum P to the center of gravity of the workpiece 7 and first hand 33 is defined as H1. The acceleration due to gravity is defined as g. Note that the weight and center of gravity may be divided into more specific parts.

[0023] If the acceleration of the workpiece 7 and the first hand 33 is α (where the direction of acceleration is positive toward the main body 2), then F1 = M1 × α, and the value of TF1 can be calculated using equation (1): TF1 = F1 × H1. The value of TG can be calculated using equation (2): TG = M2 × g × L2 + M3 × g × L3 - M1 × g × L1. TF1 acts in a direction that causes the main body 2 to tip to the left (= counterclockwise in Figure 3). The transportable weight of the workpiece 7 and the weight of each part of the robot system 1 are designed so that the value of TG is always positive, so TG acts in a direction that resists the main body 2 tipping to the left (= clockwise in Figure 3).

[0024] When the second robot 4 is stopped, in order for the first arm 32 to stably execute the pulling operation B, it is necessary to satisfy the following equation: TF1 + safety constant S≦TG··· equation (3) (where S>0). The safety constant S is a buffer amount for designing on the safe side. Note that equation (3) may be modified as follows: TF × safety factor K≦TG (where K>1). The same can be said for the following equations that include the safety constant S.

[0025] One possible way to satisfy equation (3) is to design the vehicle so that TG is increased. For example, an increase in the weight of the main body 2 can be used to increase TG. Another possible design is to increase the size of the main body 2 in a plan view from above in the vertical direction, thereby increasing the distance from the wheels to the center of gravity of the main body 2. However, these designs can cause problems, such as increased power consumption and floor wear due to the increased weight of the main body 2, and an increase in the required aisle width and a decrease in effective floor area due to the increased size of the main body 2.

[0026] Another possible means for satisfying equation (3) is to reduce TF1 by controlling the acceleration of the first arm 32 at a distance. However, this type of control causes problems such as a decrease in the operating speed of the first robot 3, and therefore a decrease in the availability of the first robot 3.

[0027] Therefore, in the first embodiment, the control device 5 controls the operation of the second robot 4 that is not performing work to generate a rotational moment that cancels out TF1. In Fig. 3, the rotational moment acting on the tipping fulcrum P due to the force F2 related to the operation of the second robot 4 is denoted as TF2. The vertical distance from the tipping fulcrum P to the center of gravity of the second hand 43 is denoted as H2.

[0028] If the acceleration of the second hand 43 is β (where the direction of acceleration is positive toward the main body 2), then F2 = M2 × β, and the value of TF2 can be calculated using TF2 = F2 × H2... Equation (4). Taking into account the force F2 of the operation of the second robot 4, in order for the first arm 32 to stably execute the pulling operation B, it is sufficient to satisfy TF1 + safety constant S ≦ TG + TF2... Equation (5). TF2 acts in a direction that resists the main body 2 from tipping over to the left (= clockwise direction in Figure 3).

[0029] Since the movement time is inversely proportional to the speed, in order to shorten the movement time and improve the operating rate, it is desirable to impart a large acceleration to the first arm 32 at the earliest possible stage. Therefore, it is desirable for the control device 5 to control the operation of the first robot 3 so as to make the initial acceleration α0 at which the first arm 32 starts the pulling operation B in the grasping state A as large as possible within a range that satisfies formula (5).

[0030] Fig. 4 is a flowchart showing an example of the flow of processing realized by the control device of Fig. 1. When there is a possibility of tipping over due to the main action alone, the robot system 1 prevents tipping over by performing an auxiliary action. In the processing shown in Fig. 4, the main action is the first robot 3 performing the aforementioned pulling action B in the aforementioned grasping state A. The auxiliary action is the action of the second robot 4 that is not performing work in the main action.

[0031] 4, the control device 5 calculates a rotational moment TF1 acting on the tipping fulcrum P of the main body 2 due to a pre-planned main operation of the first arm 32 of the first robot 3, and a rotational moment TG acting on the tipping fulcrum P of the main body 2 due to gravity (step S1). At each teaching point, the control device 5 calculates TF1 according to the above-mentioned formula (1) and calculates TG according to the above-mentioned formula (2) using teaching data, design data, etc. stored in the memory 52 or the auxiliary storage device 53.

[0032] The teaching data includes the three-dimensional coordinates, speed, and acceleration of each teaching point, the weight of the workpiece 7, etc. The design data includes the weight, dimensions, and link parameters of each part of the first robot 3 and the second robot 4. Link parameters that use the Denavit-Hartenberg notation (DH method) are known and are also called DH parameters. The link parameters that are stored in advance as design data include the distance between links, the link torsion angle, and the link length.

[0033] The control device 5 executes forward kinematic calculations using the link parameter values ​​to analytically calculate the positions of each part (each joint, the first hand 33, the second hand 43, etc.) of the first robot 3 and the second robot 4. Then, the control device 5 calculates the center of gravity position of each part, etc., and calculates TF1 and TG.

[0034] Next, the control device 5 checks whether there is a possibility of tipping over due to the main action alone (step S2). Specifically, the control device 5 checks whether the values ​​of TF1 and TG calculated in step S1 satisfy the above-mentioned formula (3). If there is no possibility of tipping over (No in step S2), the control device 5 executes control of the main action (step S3) and ends the processing. If there is a possibility of tipping over (Yes in step S2), the control device 5 executes a plan for control of the auxiliary action (step S4). The auxiliary action is an action in which the second robot 4 generates a rotational moment TF2 that cancels out TF1.

[0035] If the initial acceleration α0 at which the first arm 32 starts the pulling operation B in the gripping state A is increased to improve the availability, it is considered that the start of the pulling operation B will be the most likely to cause tipping. Therefore, the control device 5 plans control of the assist operation so that the second arm 42 extends in a direction symmetrical to the extension direction of the first arm 32 before the first arm 32 starts the operation to pull the workpiece 7. The direction symmetrical to the extension direction of the first arm 32 is a direction that is point-symmetrical to the extension direction of the first arm 32 with the tipping fulcrum P as the center. The control device 5 then plans control of the assist operation so that the second arm 42 accelerates in a direction symmetrical to the pulling direction of the first arm 32, in accordance with the timing at which the first arm 32 starts the operation to pull the workpiece 7. The direction symmetrical to the pulling direction of the first arm 32 is a direction that is point-symmetrical to the pulling direction of the first arm 32 with the tipping fulcrum P as the center.

[0036] The control device 5 takes into account both the control of the main operation and the auxiliary operation, and calculates, in addition to TF1 and TG, the rotational moment TF2 acting on the tipping fulcrum P of the main body 2 due to the auxiliary operation of the second arm 42 associated with the second robot 4. As in step S1, the control device 5 calculates TF2 at each teaching point according to the aforementioned equation (4) using the teaching data, design data, etc. stored in the memory 52 or the auxiliary storage device 53. The acceleration β of the second arm 42 associated with TF2 is calculated using the upper limit value within the allowable range. The control device 5 then checks whether the values ​​of TF1, TF2, and TG satisfy the aforementioned equation (5). If the value of β does not satisfy equation (5) even when it is the upper limit value within the allowable range, the control device 5 may modify the initial acceleration α0 of the first arm 32 associated with TF1 so that equation (5) is satisfied.

[0037] Returning to the explanation of Figure 4, the control device 5 controls the first hand 33 to grip the workpiece 7 and also controls the second arm 42 to extend in a direction symmetrical to the extension direction of the first arm 32 (step S5). However, the control device 5 does not need to control the extension of the second arm 42 simultaneously with the control of the first hand 33 to grip the workpiece 7, and may control the extension of the second arm 42 first.

[0038] Next, the control device 5 checks whether the operation of step S5 is completed (step S6). If the operation of step S5 is not completed (No in step S6), the control device 5 continues to control the operation of step S5. If the operation of step S5 is completed (Yes in step S6), the control device 5 proceeds to step S7.

[0039] Next, the control device 5 controls the first arm 32 to be pulled toward the main body 2, and accelerates the second arm 42 in a direction symmetrical to the pulling direction of the first arm 32 (step S7). Then, the control device 5 checks whether the operation of step S7 is completed (step S8). If the operation of step S7 is not completed (No in step S8), the control device 5 continues to control the operation of step S7. If the operation of step S7 is completed (Yes in step S8), the control device 5 ends the processing.

[0040] As described above, when the first robot 3 performs the pulling operation B in the gripping state A, the control device 5 controls the first hand 33 to grip the workpiece 7 and to extend the second arm 42 in a direction symmetrical to the extension direction of the first arm 32. The control device 5 also controls the first arm 32 to be pulled toward the main body 2 and to accelerate the second arm 42 in a direction symmetrical to the pulling direction of the first arm 32.

[0041] The control device 5 may execute the processes of steps S1, S2, and S4 at a timing separate from other processes, for example, when teaching of the main movement is completed.

[0042] Although the above explanation has been given using a fall to the left as an example, the present invention can be applied to falls to the right, forward, and backward in the same manner. The control device 5 identifies the tipping fulcrum P related to the fall direction to be monitored, and as described above, calculates the distance between the tipping fulcrum P and the center of gravity of each part, and then calculates the values ​​of TF1, TF2, and TG.

[0043] Furthermore, in the above explanation, the pulling operation B performed by the first arm 32 in the grasping state A has been given as an example, but the present invention can be similarly applied to other operations of the first arm 32. The control device 5 simply calculates the values ​​of TF1 and TG according to the operation of the first arm 32 and determines whether or not formula (3) is satisfied. Furthermore, if formula (3) is not satisfied, the control device 5 simply calculates the values ​​of TF1, TF2, and TG and plans appropriate control of the assisting operation by the second arm 42 so as to satisfy formula (5).

[0044] <Modification> As another means for canceling out TF1 in steps S5 and S7, the control device 5 may utilize a rotational moment TF2 caused by deceleration when the second arm 42 is extended away from the main body 2. The direction of deceleration when the second arm 42 is extended away from the main body 2 is symmetrical to the direction in which the first arm 32 is pulled, and is the same direction as β in Figure 3. Therefore, the rotational moment TF2 in this case acts in a direction (= clockwise direction in Figure 3) that resists tipping of the main body 2 to the left at the tipping fulcrum P.

[0045] In a modified example, the control device 5 controls the second arm 42 to extend away from the main body 2 before starting the operation of pulling the first arm 32 toward the main body 2. Then, the control device 5 controls the second arm 42 to decelerate the operation of extending the second arm 42 away from the main body 2 after starting the operation of pulling the first arm 32 toward the main body 2. Thereafter, if the second arm 42 extends to the maximum reach length before the main operation of the first arm 32 is completed, the control device 5 may control the second arm 42 to be pulled toward the main body 2, as in step S7.

[0046] Second Embodiment FIG. 5 is a plan view illustrating the operation of a robot system according to a second embodiment of the present invention. When the first robot 3 and the second robot 4 simultaneously perform different operations, if forces are generated in the same direction, the main body 2 is likely to become unstable. For example, as shown in FIG. 5, the first robot 3 grasps a workpiece 7a with the first hand 33 from the platform 6a on the left side of the main body 2 and places it on the platform on the top surface 21 of the main body 2. The second robot 4 grasps a workpiece 7b with the second hand 43 from the platform on the top surface 21 of the main body 2 and places it on the platform 6b on the right side of the main body 2. When these operations are performed simultaneously, forces are generated in the same direction, causing the main body 2 to become unstable.

[0047] Therefore, in the second embodiment, the control device 5 adjusts the timing of the operations of the first robot 3 and the second robot 4 so that forces are not generated in the same direction. For example, the control device 5 changes the operation plan so that the first arm 32 is pulled toward the main body 2 and the second arm 42 is pulled toward the main body 2. Furthermore, for example, the control device 5 changes the operation plan so that the first arm 32 is extended away from the main body 2 and the second arm 42 is extended away from the main body 2.

[0048] In the second embodiment, both the case where the main body 2 tilts to the left and tips over, and the case where the main body 2 tilts to the right and tips over, are considered. The tipping fulcrum P for the main body 2 to the left is the same as in FIG. 3, so the condition for not tipping over to the left is the same as in equation (5). The tipping fulcrum P for the main body 2 to the right is the contact point (not shown) between the right front wheel 23b and the right rear wheel 23d and the floor. If L1 to L3 in FIG. 3 are the distances from the tipping fulcrum P for the main body 2 to the right, the condition for not tipping over to the right can be derived in the same way as in equation (5). Then, as in the first embodiment, the control device 5 calculates the values ​​of TF1, TF2, and TG, and plans to control the movements of the first robot 3 and the second robot 4 so as to satisfy both the condition for not tipping over to the left and the condition for not tipping over to the right.

[0049] As described above, the control device 5 calculates the first rotational moment TF1 acting on the tipping fulcrum P of the main body 2 due to the operation of the first arm 32 associated with the first robot 3, the second rotational moment TF2 acting on the tipping fulcrum P of the main body 2 due to the operation of the second arm 42 associated with the second robot 4, and the third rotational moment TG acting on the tipping fulcrum P of the main body 2 due to gravity. The control device 5 then performs control to prevent the main body 2 from tipping based on the values ​​of the first rotational moment TF1, the second rotational moment TF2, and the third rotational moment TG. This allows the robot system 1 to pick the workpiece 7 quickly and stably, even if the total weight and size are small. Furthermore, the robot system 1 in the first and second embodiments can improve the operating rate while ensuring a wide working area without excessively increasing the total weight.

[0050] While the preferred embodiments of the robot system and the like according to the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that those skilled in the art can conceive of various modifications and alterations within the scope of the technical ideas disclosed herein, and it is understood that these modifications and alterations also fall within the technical scope of the present invention. [Explanation of symbols]

[0051] 1. Robot system 2...Main unit 3...First robot 4...Second robot 5...Control device 31. First Base 32 First arm 33. First Hand 41...Second base 42 Second arm 43. Second Hand TF1: Rotational moment acting on the tipping fulcrum P of the main body 2 due to the operation of the first arm 32 (=first rotational moment) TF2: rotational moment acting on the tipping fulcrum P of the main body 2 due to the operation of the second arm 42 (=second rotational moment) TG: The rotational moment acting on the tipping fulcrum P of the body 2 due to gravity (third rotational moment)

Claims

1. a first robot and a second robot; a main body on which the first robot and the second robot are installed; a control device that controls operations of the first robot and the second robot; Equipped with The control device calculates a first rotation moment acting on the tipping fulcrum of the main body due to the operation of a first arm associated with the first robot, a second rotation moment acting on the tipping fulcrum of the main body due to the operation of a second arm associated with the second robot, and a third rotation moment acting on the tipping fulcrum of the main body due to gravity, and performs control to prevent the main body from tipping over based on the values ​​of the first rotation moment, the second rotation moment, and the third rotation moment. A robot system characterized by:

2. When the first robot extends the first arm outside the main body and performs an operation of pulling the first arm toward the main body while holding a workpiece with a first hand of the first robot, the control device controls the first arm to be pulled toward the main body and accelerates the second arm in a direction symmetrical to the pulling direction of the first arm.

2. The robot system according to claim 1.

3. When the first robot extends the first arm away from the main body and performs an operation of pulling the first arm toward the main body while holding a workpiece with the first hand of the first robot, the control device controls the second arm to extend toward the side away from the main body before starting the operation of pulling the first arm toward the main body, and controls the second arm to decelerate the operation of extending the second arm toward the side away from the main body after starting the operation of pulling the first arm toward the main body.

2. The robot system according to claim 1.

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