Mobile robot system

Abstract

To provide a mobile robot system capable of improving an operation rate while securing a wide working area without excessively increasing total weight.SOLUTION: A mobile robot system 1a comprises: a self-sustainingly travelable carriage 2; and a robot 3 installed on the carriage 2, and having a robot arm 32. The mobile robot system 1a further comprises: a torque generation device 4 that is mounted on the carriage 2 and generates torque; and a control device 5 that controls operations of the robot 3 and the torque generation device 4. The control device 5 calculates a rotational moment caused by gravity acting on a toppling fulcrum of the carriage 2 and determines magnitude of the torque to be generated by the torque generation device 4 on the basis of the rotational moment caused by gravity.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a mobile robot system in which a robot is mounted on a cart. [Background technology]

[0002] At production sites, etc., AGVs (Automatic Guided Vehicles) equipped with robots are used. In AGVs, the robot arm may not reach the target workpiece, and insufficient reach of the robot arm becomes an issue. Patent Document 1 discloses a mobile robot equipped with a displacement mechanism that displaces a stage to which the base end of the robot arm is connected. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-094934 Summary of the Invention [Problem to be solved by the invention]

[0004] The technology disclosed in Patent Document 1 overcomes the problem of insufficient reach of the robot arm and ensures a wide working area. However, this creates a new problem: a decrease in the robot's operating rate. This is because, when the robot arm is extended to its maximum reach, the stability of the mobile robot decreases, and the robot arm must be moved slowly. Furthermore, the displacement mechanism disclosed in Patent Document 1 must support the entire robot arm from its base end to its tip end, and must also move the entire robot arm. This results in a larger displacement mechanism disclosed in Patent Document 1 and a larger required driving force. This inevitably increases the weight of the displacement mechanism and the driving source for operating the displacement mechanism, resulting in a problem of excessive overall weight of the mobile robot.

[0005] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a mobile robot system that can improve the operating rate while ensuring a wide working area without excessively increasing the total weight. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the present invention provides a mobile robot system comprising a cart capable of autonomous travel and a robot mounted on the cart, further comprising a torque generating device mounted on the cart to generate torque, and a control device to control the operation of the robot and the torque generating device, wherein the control device determines the magnitude of torque to be generated by the torque generating device based on the rotational moment due to the operation of the robot acting on the tipping fulcrum of the cart and the rotational moment due to gravity acting on the tipping fulcrum of the cart.

[0007] The robot may have a robot arm, and the control device may be configured to suppress the force of the robot arm when generating a maximum output torque in the torque generating device is insufficient to prevent the cart from tipping over.

[0008] Furthermore, the top surface of the cart may be a substantially rectangular shape having four corners, the robot may be installed at one of the four corners of the cart, and the torque generating device may be a reaction wheel mounted at a corner diagonally opposite the corner at which the robot is installed. [Effects of the Invention]

[0009] The present invention provides a mobile robot system that can improve the availability rate while ensuring a wide working area without excessively increasing the total weight. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a plan view showing the overall configuration of a mobile robot system according to a first embodiment of the present invention; [Figure 2]FIG. 2 is a side view showing the overall configuration of the mobile robot system of FIG. 1. [Figure 3] Block diagram showing the hardware configuration of the mobile robot system in Figure 1. [Figure 4] FIG. 2 is a diagram illustrating a first example of a moment (torque) acting on the carriage of FIG. 1; [Figure 5] FIG. 2 is a diagram illustrating a second example of a moment (torque) acting on the carriage of FIG. 1. [Figure 6] 1 is a flowchart showing an example of a process flow realized by the control device of FIG. [Figure 7] FIG. 10 is a plan view showing the overall configuration of a mobile robot system according to a second embodiment of the present invention. [Figure 8] FIG. 10 is a plan view showing the overall configuration of a mobile robot system according to a third embodiment of the present invention. [Figure 9] 10 is a flowchart showing an example of a flow of processing realized by a control device according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. The mobile robot system in the present invention may be an AGV (Automatic Guided Vehicle) or an AMR (Autonomous A mobile robot (autonomous transport robot) may also be used, and any mobile body equipped with a robot will do.

[0012] First Embodiment Fig. 1 is a plan view showing the overall configuration of a mobile robot system according to a first embodiment of the present invention. Fig. 2 is a side view showing the overall configuration of the mobile robot system of Fig. 1. As shown in Figs. 1 and 2, the mobile robot system 1a includes a carriage 2 and a robot 3 installed on the carriage 2. Furthermore, the mobile robot system 1a includes a torque generating device 4 mounted on the carriage 2 and generating torque, and a control device 5 that controls the operations of the carriage 2, the robot 3, and the torque generating device 4.

[0013] The carriage 2 has a front-rear direction X, a left-right direction Y perpendicular to the front-rear direction X, and a vertical direction Z perpendicular to the front-rear direction X and the left-right direction Y, and is formed as a substantially rectangular parallelepiped. The upper surface 21 of the carriage 2, when viewed from above in the vertical direction Z, is substantially rectangular with four corners 22. The four corners 22 are a right front corner 22a, a left front corner 22b, a right rear corner 22c, and a left rear corner 22d. The carriage 2 is provided with four wheels 23 at the front and rear of both sides in the left-right direction Y, and is capable of independent travel. The four wheels 23 are a right front wheel 23a, a left front wheel 23b, a right rear wheel 23c, and a left rear wheel 23d. The carriage 2 may be formed with a loading platform (not shown) on which workpieces such as transported objects are loaded. The drive system of the carriage 2 is not particularly limited. The wheels 23 may be omni-wheels or crawlers, as long as they have a contact point with the floor. The number of wheels 23 is not limited to four, but may be three, five or more.

[0014] The robot 3 includes a base 31, a robot arm 32 connected to the base 31, and a robot hand 33 attached to the robot arm 32. The base 31 of the robot 3 is installed at one of the four corners 22 of the carriage 2. In the example shown in FIGS. 1 and 2, the base 31 of the robot 3 is installed at the right front corner 22a. The robot arm 32 is configured with a link mechanism having multiple links and has joints connecting the links. Each joint is provided with a drive motor (not shown). An example of the robot 3 is a vertical articulated robot with six joints. However, the present invention is also applicable to robots with five or fewer or seven or more joints, horizontal articulated robots, etc. The robot hand 33 has a gripper for gripping a workpiece, such as a transported object.

[0015] The torque generator 4 is mounted on a corner 22 diagonally opposite the corner 22 where the robot 3 is installed. This allows the mobile robot system 1a to make maximum use of the reach of the robot arm 32 and ensure a wide working area. In the example shown in FIGS. 1 and 2, the torque generator 4 is mounted on the left rear corner 22d diagonally opposite the right front corner 22a where the robot 3 is installed. In the first embodiment, the torque generator 4 is two reaction wheels 4a, 4b.

[0016] The reaction wheels 4a and 4b each include a flywheel, which is a rotating body, and a motor (neither of which is shown), and generate a desired amount of torque by accelerating or decelerating the flywheel with the motor. The reaction wheel 4a is fixed so that the rotation axis of the flywheel extends in the left-right direction Y, and the reaction wheel 4b is fixed so that the rotation axis of the flywheel extends in the front-back direction X. Examples of reaction wheels 4a and 4b include, but are not limited to, those described in JP 2017-017807 A.

[0017] The control device 5 is mounted inside the carriage 2. The number of control devices 5 may be one or more. In the case of more than one, the control devices 5 are connected to each other so that they can communicate with each other. In the following, the number of control devices 5 is one, and the description will be given assuming that one control device 5 controls the operations of the carriage 2, the robot 3, and the torque generating device 4.

[0018] 3 is a block diagram showing the hardware configuration of the mobile robot system of FIG. 1. The dolly 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 23 of the dolly in accordance with command signals from the control device 5. The sensors 26 and actuators 27 provided on the dolly 2 are not limited to these examples.

[0019] The robot arm 32 and the robot hand 33 (robot 3) have an input / output interface 34, a sensor 35, and an actuator 36. The input / output interface 34 inputs signals from the control device 5 and outputs signals to the control device 5. The sensor 35 is, for example, an encoder, which detects the rotation speed and rotation angle of the drive motor of each rotation axis and outputs sensor data to the control device 5. The actuator 36 is, for example, a drive motor for the joint of the robot arm 32 or the gripping part of the robot hand 33, and drives the joint or gripping part in accordance with a command signal from the control device 5. The sensors 35 and actuators 36 included in the robot arm 32 and the robot hand 33 (robot 3) are not limited to these examples.

[0020] The reaction wheels 4a, 4b (torque generating device 4) have an input / output interface 41, a sensor 42, and an actuator 43. The input / output interface 41 inputs signals from the control device 5 and outputs signals to the control device 5. The sensor 42 is, for example, an inertial sensor combining a gyro sensor, an accelerometer, etc., and detects three-dimensional inertial motion (translational motion and rotational motion) and outputs sensor data to the control device 5. The actuator 43 is, for example, a drive motor, and drives the flywheel in accordance with a command signal from the control device 5. The sensor 42 and the actuator 43 included in the reaction wheels 4a, 4b (torque generating device 4) are not limited to these examples.

[0021] 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 commands. The auxiliary storage device 53 is a hard disk drive, a solid state drive, or the like, and stores data used in processing described below. The input / output interface 54 inputs signals from the cart 2, the robot 3, the torque generator 4, and other devices, and outputs signals to them.

[0022] Fig. 4 is a diagram illustrating a first example of the moment (torque) acting on the carriage of Fig. 1. In Fig. 4, the left rear wheel 23d is omitted to make the reaction wheel 4a easier to see. In the first example, the robot 3 performs an action (hereinafter referred to as "action B") of pulling the workpiece W backward in the X direction, with the robot arm 32 extending forward in the X direction and the robot hand 33 gripping the workpiece W (hereinafter referred to as "state A").

[0023] In state A, the center of gravity of the entire mobile robot system 1a shifts to the front of the cart 2, reducing the stability of the cart 2. Furthermore, when action B is performed in state A, that is, when force F is applied backward in the X direction, the reaction force F further reduces the stability of the cart 2, increasing the possibility that the cart 2 will tilt forward in the X direction and tip over.

[0024] In the example shown in FIG. 4, the tipping fulcrum P forward in the X direction is the contact point between the right front wheel 23a and the left front wheel 23b and the floor. TF denotes the rotational moment acting on the tipping fulcrum P due to the force F of the robot 3's movement, and TG denotes the rotational moment due to gravity acting on the tipping fulcrum P. M1 denotes the weight of the workpiece W, and M2 denotes the total weight of the cart 2, base 31, robot arm 32, robot hand 33, torque generator 4, and control device 5. L1 denotes the distance in the Z direction from the tipping fulcrum P to the center of gravity of the workpiece W. L2 denotes the distance in the X direction from the tipping fulcrum P to the center of gravity of the cart 2, base 31, robot arm 32, robot hand 33, torque generator 4, and control device 5. L3 denotes the distance in the X direction from the tipping fulcrum P to the center of gravity of the workpiece W. G denotes the gravitational acceleration. Note that weight and center of gravity may be considered in terms of more detailed components.

[0025] In this case, the values ​​of TF and TG can be calculated using equation (1): TF = F × L1···, and equation (2): TG = M2 × g × L2 - M1 × g × L3···. TF acts in a direction that attempts to tip the cart 2 (counterclockwise in the drawing). The payload capacity of the workpiece W and the weight of each part of the mobile robot system 1 are designed so that the value of TG is always positive, so TG acts in a direction that resists tipping of the cart 2 (clockwise in the drawing).

[0026] When the torque generating device 4 does not operate, in order for the robot arm 32 to stably execute operation B, it is necessary to satisfy TF + safety constant S≦TG···Equation (3) (where S>0). The safety constant S is a buffer amount for designing on the safe side. Equation (3) may be modified as follows: TF × safety coefficient K≦TG···Equation (3)′ (where K>1). The same applies to equations (4) to (10) below.

[0027] One possible way to satisfy equation (3) is to design the cart 2 so that it has a larger TG. Examples of ways to increase TG include increasing the weight of the cart 2, concentrating the weight on the side opposite the robot 3 (the rear side in the X direction in the drawing) to create an off-center center of gravity, or installing a counterweight on the side opposite the robot 3. Another possible way to satisfy equation (3) is to increase the size of the cart 2 in a plan view from above in the vertical direction Z, thereby increasing the distance from the wheels 23 to the center of gravity of the cart 2. However, these designs can cause problems, such as increased power consumption and floor wear due to the increased weight of the cart 2, and an increased required aisle width and reduced effective floor area due to the increased size of the cart 2.

[0028] Another possible means for satisfying equation (3) is to reduce TF by controlling the acceleration of the robot arm 32 at a distance. However, this type of control causes problems such as a decrease in the operating speed of the robot 3, and therefore a decrease in the availability of the robot 3.

[0029] Therefore, in this embodiment, the reaction wheel 4a (torque generator 4) generates torque in a direction (= opposite direction to TF) that resists tipping of the cart 2. If the torque generated by the reaction wheel 4a and acting on the tipping fulcrum P is TRa, the magnitude of TRa depends only on the radius, mass, and angular acceleration of the reaction wheel 4a. In other words, the magnitude of TRa does not depend on the distance in the front-rear direction X between the reaction wheel 4a and the tipping fulcrum P. However, in order to increase TG by the weight of the reaction wheel 4a, it is desirable to mount the reaction wheel 4a on the left rear corner 22d diagonally opposite the right front corner 22a where the robot 3 is installed, as shown in FIG. 1. Then, the control device 5 controls the operation of the reaction wheel 4a so as to satisfy the equation (4): TF + safety constant S ≦ TG + TRa.

[0030] 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 high acceleration to the robot arm 32 at the earliest possible stage. Therefore, the control device 5 may control the operations of the robot 3 and the reaction wheel 4a so as to increase the initial acceleration at which the robot arm 32 starts operation B in state A as much as possible within a range that satisfies formula (4).

[0031] Fig. 5 is a diagram illustrating a second example of the moment (torque) acting on the cart in Fig. 1. In the second example shown in Fig. 5, the robot 3 performs an action (hereinafter "action D") to pull the workpiece W toward the cart 2 in a state where the robot arm 32 extends in any direction on the XY plane and the robot hand 33 grasps the workpiece W (hereinafter "state C"). In the second example, there is a possibility that the robot will tilt forward in the X direction and tip over, or tilt to the right in the Y direction and tip over.

[0032] 5, the tipping fulcrum Px forward in the X direction is the contact point between the right front wheel 23a and the left front wheel 23b and the floor. The tipping fulcrum Py to the right in the Y direction is the contact point between the right front wheel 23a and the right rear wheel 23c and the floor. Here, the reaction F caused by the action D is considered by decomposing it into an X component Fx and a Y component Fy.

[0033] The rotational moment due to robot operation acting on tipping fulcrum Px by component force Fx is defined as TFx, the rotational moment due to gravity acting on tipping fulcrum Px is defined as TGx, and the torque generated by reaction wheel 4a acting on tipping fulcrum Px is defined as TRa. Note that the direction of TRa is the direction that resists tipping of cart 2 (= the opposite direction to TFx). TFx can be calculated in the same way as equation (1), and TGx can be calculated in the same way as equation (2). Then, control device 5 controls the operation of reaction wheel 4a so as to satisfy TFx + safety constant Sx ≦ TGx + TRa... equation (5).

[0034] Similarly, the rotational moment due to robot movement acting on tipping fulcrum Py by component force Fy is defined as TFy, the rotational moment due to gravity acting on tipping fulcrum Py is defined as TGy, and the torque generated by reaction wheel 4b acting on tipping fulcrum Py is defined as TRb. However, the direction of TRb is set to a direction that resists tipping of cart 2 (= opposite direction to TFy). TFy can be calculated in the same way as equation (1), and TGy can be calculated in the same way as equation (2). Then, control device 5 controls the operation of reaction wheel 4b so as to satisfy TFy + safety constant Sy ≦ TGy + TRb... equation (6).

[0035] In addition, the control device 5 may control the operation of the robot 3 and the reaction wheels 4a, 4b so as to maximize the initial acceleration at which the robot arm 32 starts operation D from state C, within the range that satisfies equations (5) and (6).

[0036] Although two examples have been described to facilitate understanding, the state A and operation B in the first example are merely special cases in which only the forward / backward direction X is considered in the state C and operation D in the second example. In the following, it is assumed that the control device 5 controls the operations of the reaction wheels 4a and 4b so as to satisfy the formulas (5) and (6).

[0037] FIG. 6 is a flowchart showing an example of the flow of processing realized by the control device of FIG. 1. In the processing shown in FIG. 6, if equations (5) and (6) are satisfied within the range of the maximum output torque of the reaction wheels 4a and 4b, the control device 5 causes the reaction wheels 4a and 4b to generate the required amount of torque. On the other hand, if equations (5) and (6) are not satisfied within the range of the maximum output torque of the reaction wheels 4a and 4b, the control device 5 causes the reaction wheels 4a and 4b to generate the maximum output torque and decelerates the movement of the robot arm 32 to a degree that can be suppressed by the reaction wheels 4a and 4b. Hereinafter, the maximum output torques of the reaction wheels 4a and 4b are referred to as TRmax and TRbmax, respectively. These are upper limits determined by the performance of the motors and become 0 when saturated.

[0038] 6, the control device 5 checks whether TFx+Sx≦TGx is satisfied (step S1). If this inequality is satisfied (Yes in step S1), the control device 5 proceeds to step S6, and if not (No in step S1), the control device 5 proceeds to step S2.

[0039] In step S2, the control device 5 checks whether TRamax≧TFx+Sx−TGx is satisfied. If this inequality is satisfied (Yes in step S2), the torque of the reaction wheel 4a is sufficient, so the control device 5 determines the value of TRa using the formula TRa=TFx+Sx−TGx (step S3). If this inequality is not satisfied (No in step S2), the torque of the reaction wheel 4a is insufficient, so the control device 5 needs to reduce the acceleration of the robot arm 32 and suppress the force. Specifically, the control device 5 determines the value of TRa to be TRamax, and determines the value of TFx using the formula TFx=TGx+TRa−Sx (step S4).

[0040] Then, the control device 5 transmits a control command to prevent the robot 3 from falling over to the robot 3 and the torque generating device 4 (reaction wheel 4a) (step S5). The content of the control command is a value (= the magnitude of the torque to be generated in the reaction wheel 4a, the acceleration of the robot arm 32) determined based on step S3 or S4. The control command to prevent the robot 3 from falling over becomes an interrupt control to the conventional operation control of the robot 3.

[0041] In step S6, the control device 5 checks whether TFy+Sy≦TGy is satisfied. If this inequality is satisfied (Yes in step S6), the control device 5 repeats the process from step S1, and if it is not satisfied (No in step S6), the control device 5 proceeds to step S7.

[0042] In step S7, the control device 5 checks whether TRbmax≧TFy+Sy−TGy is satisfied. If this inequality is satisfied (Yes in step S7), the torque of the reaction wheel 4b is sufficient, so the control device 5 determines the value of TRb using the formula TRb=TFy+Sy−TGy (step S8). If this inequality is not satisfied (No in step S7), the torque of the reaction wheel 4b is insufficient, so the control device 5 needs to reduce the acceleration of the robot arm 32 and suppress the force. Specifically, the control device 5 determines the value of TRb to be TRbmax, and determines the value of TFy using the formula TFy=TGy+TRb−Sy (step S9).

[0043] Then, the control device 5 transmits a control command to prevent the robot 3 and the torque generating device 4 (reaction wheel 4B) from tipping over (step S10), and repeats the process from step S1. The content of the control command is a value (= the magnitude of the torque to be generated in the reaction wheel 4b, the acceleration of the robot arm 32) determined based on step S8 or S9. The control command to prevent the robot 3 from tipping over is an interrupt control to the conventional operation control of the robot 3.

[0044] 6, the control device 5 acquires the current acceleration of the robot arm 32 and calculates the values ​​of TFx and TFy. The control device 5 also calculates the rotational moments TGx and TGy due to gravity acting on the tipping fulcrums Px and Py based on the design data and sensor data. The control device 5 stores in advance in the memory 52 or the auxiliary storage device 53 the design data of the mobile robot system 1a required for calculating the rotational moments due to gravity.

[0045] The design data of the mobile robot system 1a that is stored in advance includes, for example, the weight and dimensions of each part, and the link parameters of the robot arm 32. The weight of the workpiece W is the maximum carry weight if there are individual differences. 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. The sensor data is, for example, the rotation angle of the drive motor of the robot arm 32. The rotation angle of the drive motor is the link angle, which is one of the link parameters.

[0046] The control device 5 executes forward kinematics calculations using the values ​​of the link parameters to analytically calculate the position of each part (each joint, robot hand 33, etc.) of the robot 3. Then, the control device 5 calculates the positions of the centers of gravity of the robot arm 32 and the cart 2, and calculates the rotational moments TGx and TGy due to gravity acting on the tipping fulcrums Px and Py.

[0047] In steps S3 and S8 of FIG. 6, the control device 5 causes the reaction wheels 4a and 4b to generate the minimum values ​​of TRa and TRb that satisfy equations (5) and (6), thereby maximizing the operating rate of the robot 3 while minimizing the power consumption caused by driving the torque generating device 4.

[0048] Furthermore, if the torque of the reaction wheel 4b is insufficient to prevent the robot 3 from tipping over, in steps S4 and S9 of FIG. 6, the control device 5 generates the maximum output torque on the reaction wheels 4a and 4b and determines the force of the robot arm 32 to be the maximum value that satisfies equations (5) and (6). This allows the operating rate of the robot 3 to be maximized while preventing the robot 3 from tipping over.

[0049] As described above, the mobile robot system 1a includes the cart 2 and the robot 3 mounted on the cart 2 and having the robot arm 32. The mobile robot system 1a also includes reaction wheels 4a, 4b (torque generator 4) mounted on the cart 2 and generating torque, and a control device 5 that controls the operation of the robot 3 and the reaction wheels 4a, 4b. The control device 5 determines the magnitude of the torque to be generated by the reaction wheels 4a, 4b based on the rotational moment acting on the tipping fulcrum of the cart 2 due to the operation of the robot 3 and the rotational moment acting on the tipping fulcrum of the cart 2 due to gravity. This allows the mobile robot system 1a according to the first embodiment to secure a wide working area and improve the operating rate without excessively increasing the total weight.

[0050] Furthermore, if the maximum output torque generated by the reaction wheels 4a, 4b (torque generating device 4) is insufficient to prevent the cart 2 from tipping over, the control device may be configured to suppress the force of the robot arm 32. This makes it possible to reliably prevent the cart 2 from tipping over.

[0051] Furthermore, the control device 5 may determine the magnitude of the torque to be generated by the torque generating device 4 even at a timing other than the start of the robot arm 32's operation to pull the workpiece W. For example, the control device 5 may execute the process shown in Fig. 6 immediately before the robot hand 33 grasps the workpiece W. This improves the stability of the cart 2 and prevents it from tipping over, even when, for example, the robot hand 33 attempts to grasp a heavy workpiece W on an uneven floor with the reach of the robot arm 32 fully extended.

[0052] Second Embodiment 7 is a plan view showing the overall configuration of a mobile robot system according to a second embodiment of the present invention. Elements similar to those in the first embodiment are given the same reference numerals, and redundant explanations will be omitted.

[0053] As shown in Fig. 7, the mobile robot system 1b includes a cart 2 and a robot 3 installed on the cart 2. The mobile robot system 1b further includes a torque generator 4 that is installed on the cart 2 and generates torque, and a control device 5 that controls the operation of the robot 3 and the torque generator 4. The torque generator 4 is installed in a corner 22 diagonally opposite the corner 22 on which the robot 3 is installed.

[0054] 7, the torque generator 4 is a single reaction wheel 4c, which is mounted on the left rear corner 22d diagonally opposite the right front corner 22a where the robot 3 is installed. The reaction wheel 4c is fixed so that the rotation axis of the flywheel is oblique (i.e., neither perpendicular nor parallel) to both the front-rear direction X and the left-right direction Y.

[0055] In the second embodiment, as in the first embodiment, the robot 3 performs an operation (operation D) of pulling the workpiece W toward the carriage 2 with the robot arm 32 extending in any direction on the XY plane and the robot hand 33 gripping the workpiece W (state C). The tipping fulcrum Px forward in the X direction is the contact point between the right front wheel 23a and the left front wheel 23b and the floor, and the tipping fulcrum Py to the right in the Y direction is the contact point between the right front wheel 23a and the right rear wheel 23c and the floor. The control device 5 also executes processing according to the flowchart shown in FIG.

[0056] Here, the reaction force F caused by the action D is generated as Fx and Fy by the reaction wheel 4c, and the torque TRc acting on the tipping fulcrums Px and Py is decomposed into TRcx and TRcy. However, the direction of TRc is set to the direction that resists the tipping of the cart 2 (= the opposite direction to TF).

[0057] Let TFx be the rotational moment due to robot movement acting on tipping fulcrum Px by component force Fx, and TGx be the rotational moment due to gravity acting on tipping fulcrum Px. TFx can be calculated using equation (1), and TGx can be calculated using equation (2). Similarly, let TFy be the rotational moment due to robot movement acting on tipping fulcrum Py by component force Fy, and TGy be the rotational moment due to gravity acting on tipping fulcrum Py. TFy can be calculated using equation (1), and TGy can be calculated using equation (2).

[0058] Then, the control device 5 controls the operation of the reaction wheel 4c so as to satisfy the following expressions: TFx+safety constant Sx≦TGx+TRcx (7) and TFy+safety constant Sy≦TGy+TRcy (8). The control device 5 executes the process according to the flowchart shown in FIG. 6, similarly to the first embodiment.

[0059] As described above, the mobile robot system 1b includes the cart 2 and the robot 3 mounted on the cart 2 and having the robot arm 32. The mobile robot system 1b also includes a reaction wheel 4c (torque generator 4) mounted on the cart 2 and generating torque, and a control device 5 that controls the operation of the robot 3 and the reaction wheel 4c. The control device 5 determines the magnitude of the torque to be generated by the reaction wheel 4c based on the rotation moment caused by the operation of the robot 3 acting on the tipping fulcrum of the cart 2 and the rotation moment caused by gravity acting on the tipping fulcrum of the cart 2. As a result, the mobile robot system 1b according to the second embodiment can improve the operating rate while ensuring a wide working area without excessively increasing the total weight.

[0060] As in the first embodiment, when the maximum output torque generated by the reaction wheel 4c (torque generating device 4) is insufficient to prevent the cart 2 from tipping over, the control device 5 may suppress the force of the robot arm 32. This can reliably prevent the cart 2 from tipping over.

[0061] The magnitudes of the X-component TFx and Y-component TFy of the rotational moment TF due to the robot arm 32 change depending on the direction in which the robot arm 32 extends. To simultaneously satisfy equations (7) and (8), it is desirable that the direction of the torque TRc due to the reaction wheel 4c be exactly opposite to the direction of the rotational moment TF due to the robot's movement, i.e., 180 degrees opposite. Therefore, the mobile robot system 1b may be provided with a rotation mechanism (not shown) that can change the angle between the rotation axis of the flywheel of the reaction wheel 4c and the X-axis and Y-axis. In this case, before executing step S3 shown in FIG. 6, the control device 5 controls the operation of the rotation mechanism so that the direction of the torque TRc due to the reaction wheel 4c is exactly opposite to the direction of the rotational moment TF due to the robot's movement.

[0062] Third Embodiment 8 is a plan view showing the overall configuration of a mobile robot system according to a third embodiment of the present invention. Note that the same elements as those in the first embodiment are given the same reference numerals, and redundant explanations will be omitted.

[0063] As shown in Fig. 8, the mobile robot system 1c includes a cart 2 and a robot 3 installed on the cart 2. The mobile robot system 1c further includes a torque generator 4 that is mounted on the cart 2 and generates torque, and a control device 5 that controls the operation of the robot 3 and the torque generator 4. The torque generator 4 is mounted on a corner 22 diagonally opposite the corner 22 on which the robot 3 is installed.

[0064] In the third embodiment, the torque generator 4 is a single linear motion mechanism 4d, and in the example shown in Fig. 8, it is mounted in the left rear corner 22d, which is diagonally opposite the right front corner 22a where the robot 3 is installed. In the case of the linear motion mechanism 4d, the further away from the tipping fulcrums Px and Py the mechanism 4d is mounted, the greater the torque it generates with the same force. Therefore, mounting the linear motion mechanism 4d in the position shown in Fig. 8 is advantageous for preventing tipping, not only because it increases the TG due to the weight of the linear motion mechanism 4d, but also because it increases the torque it generates.

[0065] The linear motion mechanism 4d includes a weight, a support part that supports the weight so that it can be accelerated or decelerated in the vertical direction Z, and a motor that accelerates or decelerates the weight in the vertical direction Z (all of which are not shown). The control device 5 transmits commands indicating the number of rotations and the direction of rotation of the motor to the linear motion mechanism 4d, and controls the operation of the linear motion mechanism 4d.

[0066] When the weight accelerates from bottom to top, a torque is generated directly below the weight. The direction of the torque generated at this time is the same as the rotational moment due to gravity (vertical downward). The torque generated by the linear motion mechanism 4d can be decomposed into an X-direction component and a Y-direction component, just like the rotational moment due to gravity. Therefore, no matter in which direction the robot arm 32 is extended, an effective torque that resists the cart 2 from tipping over can be generated.

[0067] In the third embodiment, as in the first embodiment, the robot 3 performs an action (action D) to pull the workpiece W toward the carriage 2 in a state where the robot arm 32 extends in any direction on the XY plane and the robot hand 33 grasps the workpiece W (state C). The tipping fulcrum Px forward in the X direction is the contact point between the right front wheel 23a and the left front wheel 23b and the floor, and the tipping fulcrum Py to the right in the Y direction is the contact point between the right front wheel 23a and the right rear wheel 23c and the floor.

[0068] Here, we consider the reaction force F caused by action D as Fx and Fy, and the torque TRd generated by the linear motion mechanism 4d and acting on the tipping fulcrum as TRdx and TRdy. The magnitude of TRdx is proportional to the distance in the front-to-back direction X between the linear motion mechanism 4d and the tipping fulcrum Px. The magnitude of TRdy is proportional to the distance in the left-to-right direction Y between the linear motion mechanism 4d and the tipping fulcrum Py.

[0069] Let TFx be the rotational moment due to robot movement acting on tipping fulcrum Px by component force Fx, and TGx be the rotational moment due to gravity acting on tipping fulcrum Px. TFx can be calculated using equation (1), and TGx can be calculated using equation (2). Similarly, let TFy be the rotational moment due to robot movement acting on tipping fulcrum Py by component force Fy, and TGy be the rotational moment due to gravity acting on tipping fulcrum Py. TFy can be calculated using equation (1), and TGy can be calculated using equation (2).

[0070] The control device 5 controls the operation of the linear motion mechanism 4d so as to satisfy TFx+safety constant Sx≦TGx+TRdx·equation (9) and TFy+safety constant Sy≦TGy+TRdy·equation (10).

[0071] FIG. 9 is a flowchart showing an example of the flow of processing implemented by a control device according to a third embodiment of the present invention. In the case of the linear motion mechanism 4d, since the movement range of the weight is limited, "unloading" is required to decelerate the weight during the anti-overturn control. The flowchart in FIG. 9 shows the flow of processing taking this unloading into consideration. Hereinafter, the torque generated in the linear motion mechanism 4d during unloading is referred to as TRunload.

[0072] As shown in Fig. 9, the control device 5 checks whether unloading is necessary (step S11). For example, when the weight reaches a predetermined height, the control device 5 determines that unloading is necessary. If unloading is not necessary (No in step S11), the control device 5 executes the process shown in Fig. 6 (step S12) and repeats from step S11. If unloading is necessary (Yes in step S11), the control device 5 proceeds to step S13.

[0073] The control device 5 determines the value of TRd as TRunload (step S13) and checks whether TF+S≦TG−TRd is satisfied (step S14). If this inequality is satisfied (Yes in step S14), the control device 5 determines that the torque generated by the linear motion mechanism 4d during unloading is sufficient, and proceeds to step S16. If this inequality is not satisfied (No in step S14), the torque generated by the linear motion mechanism 4d during unloading is insufficient, and the control device 5 must reduce the acceleration of the robot arm 32 to suppress the force. Specifically, the control device 5 determines the value of TF using the formula TF=TG+TRd−S (step S15).

[0074] Then, the control device 5 transmits an unloading control command to the robot 3 and the torque generating device 4 (reaction wheel 4B) (step S16), and repeats the process from step S11. The content of the control command is a value (= the magnitude of the torque to be generated in the linear motion mechanism 4d, the acceleration of the robot arm 32) determined based on steps S13 and S15. The unloading control command to the robot 3 is an interrupt control to the conventional operation control of the robot 3.

[0075] As described above, the mobile robot system 1c includes the cart 2 and the robot 3 mounted on the cart 2 and having the robot arm 32. The mobile robot system 1c also includes a linear motion mechanism 4d (torque generator 4) mounted on the cart 2 and generating torque, and a control device 5 that controls the operation of the robot 3 and the linear motion mechanism 4d. The control device 5 determines the magnitude of the torque to be generated by the linear motion mechanism 4d based on the rotational moment acting on the tipping fulcrum of the cart 2 due to the movement of the robot 3 and the rotational moment acting on the tipping fulcrum of the cart 2 due to gravity. This allows the mobile robot system 1c according to the third embodiment to secure a wide working area and improve the operating rate without excessively increasing the total weight.

[0076] As in the first embodiment, when the maximum output torque generated by the linear motion mechanism 4d (torque generating device 4) is insufficient to prevent the cart 2 from tipping over, the control device 5 may suppress the force of the robot arm 32. This can reliably prevent the cart 2 from tipping over.

[0077] While the preferred embodiments of the mobile 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]

[0078] 1. Mobile robot system 2...Cart 3. Robot 4 Torque generating device 4a, 4b, 4c...Reaction wheels 4d……Linear motion mechanism 5...Control device 21...Top of the cart 22 Corner of the trolley 23... Cart wheel 32. Robot arm TF: Rotational moment due to robot movement TG: rotational moment due to gravity TR: Torque generated by a torque generator

Claims

1. A mobile robot system comprising: a cart capable of autonomous travel; and a robot installed on the cart, a torque generating device mounted on the carriage and configured to generate torque; a control device for controlling the operation of the robot and the torque generating device; Further provided with The control device determines the magnitude of the torque to be generated by the torque generating device based on a rotational moment due to the movement of the robot acting on the tipping fulcrum of the cart and a rotational moment due to gravity acting on the tipping fulcrum of the cart.

2. the robot has a robot arm; 2. The mobile robot system according to claim 1, wherein the control device reduces the force of the robot arm when the torque generating device generates a maximum output torque that is insufficient to prevent the carriage from tipping over.

3. the upper surface of the carriage has a substantially rectangular shape having four corners when viewed from above in a plan view, The robot is installed at one of four corners of the carriage, The torque generating device is a reaction wheel, and is mounted on a corner diagonally opposite to the corner where the robot is installed.

3. The mobile robot system according to claim 1 or 2.

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