Robot system

Abstract

A robot system (1) includes a robot (2) and a control device (3) for controlling the robot (2). The robot (2) includes a carriage (4) and a robot arm (5) mounted on the carriage (4). The robot arm (5) includes a sensor (12) for detecting a force or torque acting on one or more joints. The control device (3) controls at least one of the robot arm (5) and the carriage (4) based on the force or torque detected by the sensor (12) such that the torque acting on the carriage (4) does not exceed the tipping torque.

Description

Technical Field

[0001] The present disclosure relates to a robot system. Background Art

[0002] There is known a mobile platform type robot having a manipulator mounted on a carriage (for example, refer to Patent Document 1).

[0003] Patent Document 1 describes setting a target change amount of the ZMP based on the actual ZMP obtained from the behavior of the carriage-mounted robot and the ZMP critical value at which the standing state of the carriage-mounted robot is unstable.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2006-150567 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] In Patent Document 1, during the movement of the carriage, by adjusting the angle of the manipulator, it is ensured that the robot does not tip over due to the acceleration of the carriage. However, in the mobile platform type robot, at the movement destination of the carriage, the robot operates each time without using a fixing tool to fix the carriage to the ground. Therefore, there is a need for a robot system that can prevent tipping caused by the movement of the manipulator not only during the movement of the carriage but also in the state where the carriage stops at each operation site of the movement destination.

[0009] Solutions for Solving the Problems

[0010] One aspect of the present disclosure is a robot system including: a robot; and a control device for controlling the robot, the robot including a carriage and a manipulator mounted on the carriage, the manipulator including a sensor for detecting a force or torque acting on one or more joints, and the control device controlling at least one of the manipulator and the carriage based on the force or torque detected by the sensor so that the torque acting on the carriage does not exceed the tipping torque. Brief Description of the Drawings

[0011] Figure 1 FIG. is a perspective view showing a robot system according to an embodiment of the present disclosure.

[0012] Figure 2 To show Figure 1 of the robot system.

[0013] Figure 3 Top view of the mobile platform vehicle type robot included in the robot system shown in Figure 1 . Figure 1

[0014] Figure 4 To show Figure 1 A diagram showing an example of the relationship between the angle of the rotating body of the mobile platform vehicle type robot included in the robot system shown in Figure 1 and the tipping moment.

[0015] Figure 5 To illustrate Figure 3 Side view for explaining the moments acting on each part when the angle θ1 of the rotating body of the mobile platform vehicle type robot shown in Figure 3 is 0°.

[0016] Figure 6 To illustrate Figure 3 Front view for explaining the moments acting on each part when the angle θ1 of the rotating body of the mobile platform vehicle type robot shown in Figure 3 is 90°. Detailed implementation mode

[0017] Hereinafter, the robot system 1 according to an embodiment of the present disclosure will be described with reference to the accompanying drawings.

[0018] As shown in Figure 1 and Figure 2 , the robot system 1 according to the present embodiment includes a mobile platform vehicle type robot (robot) 2 and a control device 3 for controlling the mobile platform vehicle type robot 2. The control device 3 is built in the mobile platform vehicle type robot 2, for example.

[0019] The mobile platform vehicle type robot 2 includes a self-propelled or push-type trolley 4 capable of traveling on the road surface and a robot arm 5 mounted on the trolley 4.

[0020] The trolley 4 is, for example, a four-wheeled vehicle, on the upper surface of which the robot arm 5 is mounted, and includes a mounting table 6 for mounting workpieces and the like within the operating range of the robot arm 5. In the figure, the reference numeral 14 denotes the wheels of the trolley 4.

[0021] The robot arm 5 includes a base 7 and a rotating body 8. The base 7 is fixed to the upper surface of the trolley 4, and the rotating body 8 is supported so as to be rotatable about a vertical first axis J1 relative to the base 7. In addition, the robot arm 5 includes a first robot arm 9, a second robot arm 10, and a three-axis wrist unit 11. The first robot arm 9 is supported so as to be rotatable about a horizontal second axis J2 relative to the rotating body 8, the second robot arm 10 is supported so as to be rotatable about a third axis J3 parallel to the second axis J2 relative to the first robot arm 9, and the three-axis wrist unit 11 is mounted at the front end of the second robot arm 10. The form of the robot arm 5 is not limited to the vertical multi-joint type, and any form such as the horizontal multi-joint type or the linear motion type may be adopted. ​

[0022] As Figure 1 shown, a torque sensor (sensor) 12 is provided at a position of the first robotic arm 9 near the second axis J2. The torque sensor 12 is configured to detect the torque about the second axis J2. Further, the torque sensor 12 configured to detect the torque about the second axis J2 can also detect the torque itself applied by the robotic hand 5 to the carriage 4.

[0023] In addition, a hand 13 for gripping a workpiece (not shown) is mounted at the front end of the wrist unit 11.

[0024] The control device 3 includes a storage unit 16 and a control unit 17. The storage unit 16 stores programs and the like, and the control unit 17 controls the robotic hand 5 according to the programs stored in the storage unit 16. The storage unit 16 is constituted by a memory, and the control unit 17 is constituted by a processor and a memory.

[0025] In addition, the control device 3 receives the torque about the second axis J2 detected by the torque sensor 12, and controls the robotic hand 5 at each position of the robotic hand 5 that moves relative to the carriage 4 to a state where the detected torque does not exceed the tipping torque Ma.

[0026] The tipping torque Ma is the torque applied by the robotic hand 5 to the carriage 4, that is, the critical value at which the carriage 4 tips over. The tipping torque Ma is stored in advance in the storage unit 16 corresponding to the angle θ1 of the rotating body 8 relative to the base 7 about the first axis J1.

[0027] For example, as Figure 1 and Figure 3 shown, the carriage 4 is provided with four wheels 14. When the first axis J1 is disposed at the center of the left and right wheels 14 and is closer to the front wheel among the front and rear wheels 14, as Figure 4 shown, the tipping torque Ma changes corresponding to the angle θ1.

[0028] And, for example, as Figure 5 shown, in a state where the rotating body 8 of the robotic hand 5 is disposed at the origin position (θ1 = 0°) in front of the traveling direction of the carriage 4 with respect to the base 7, the condition for the static tipping of the carriage 4 is as shown in the following formula (1):

[0029] L1 × W1 < L2 × W2 (1)

[0030] Here, W1 is the weight of the carriage 4, L1 is the distance from the center of the front wheel of the carriage 4 to the center of gravity of the carriage 4, W2 is the weight of the robotic hand 5, the hand 13, and the workpiece, and L2 is the distance from the center of the front wheel of the carriage 4 to the center of gravity of the robotic hand 5, the hand 13, and the workpiece as a whole.

[0031] The masses W1, W2 and the distance L1 are known values.

[0032] Although the distance L2 is a value determined according to the posture of the robot hand 5, it can be calculated by the following formula (2) using the torque M about the first axis J1 detected by the torque sensor 12:

[0033] M = (L2 + L3) × W2 (2)

[0034] Here, L3 is the distance from the center of the front wheels of the carriage 4 to the first axis J1 and is a known value.

[0035] When formula (2) is used to transform formula (1), it is as shown in the following formulas (3) and (4):

[0036] L1 × W1 < (M / W2 - L3) × W2 (3)

[0037] M > L1 × W1 + L3 × W2 = Ma(θ1) (4)

[0038] Here, Ma(θ1) is the tipping moment that changes corresponding to the angle θ1.

[0039] That is, when the moment M on the left side of formula (4) exceeds the tipping moment Ma(θ1) on the right side, the carriage 4 will tip over.

[0040] The control device 3 calculates the difference between the moment M detected by the torque sensor 12 and the tipping moment Ma, that is, the differential moment, at each position of the robot hand 5.

[0041] Normally, it is designed such that as long as the weight of the gripped workpiece is below the rated weight, the tipping condition of formula (4) will not be satisfied, and the robot hand 5 can operate in the entire operating range without tipping over the carriage 4. However, there may be a situation where even if the operating range of the robot hand 5 is restricted, it is desired to increase the rated weight of the workpiece to be processed. In this case, it is necessary to consider the situation where the carriage 4 tips over.

[0042] The situation where the carriage 4 tips over is as follows:

[0043] First, for example, in a state where the hand 13 grips a heavy workpiece, if the first robot arm 9 and the second robot arm 10 extend forward in the traveling direction of the carriage 4, the tipping condition of formula (4) will be gradually approached, and at a certain point in time, the differential moment becomes zero and the carriage 4 tips over. To avoid tipping over in this case, before the tipping condition of formula (4) is satisfied, the control device 3 stops the operation of the robot hand 5.

[0044] Second, if the robot arm 5 moving in the direction close to the tipping condition of formula (4) is decelerated to stop, a reaction torque equal to the deceleration torque is added, causing the torque acting on the carriage 4 to increase sharply, and the tipping condition of formula (4) is satisfied.

[0045] To avoid tipping in this case, the control device 3 decelerates the operation of the robot arm 5 at each position during the operation of the robot arm 5 relative to the carriage 4 when the calculated differential torque reaches a predetermined value each time.

[0046] In the case where the robot arm 5 stops suddenly during operation, since the maximum deceleration torque is generated, preferably, the predetermined value is set to a value greater than the deceleration torque required for sudden stop.

[0047] The deceleration torque required for sudden stop varies depending on the operation speed of the robot arm 5, and thus is calculated based on the operation speed at each position.

[0048] When the robot arm 5 moves in the direction close to the tipping condition of formula (4), even if it is decelerated at a deceleration smaller than that during sudden stop, it will be closer to the tipping condition, but the deceleration torque required for sudden stop will decrease due to the speed reduction. Therefore, the robot arm 5 can be operated while maintaining the state where the tipping condition of formula (4) is not satisfied, and even if an emergency stop command is issued, the carriage 4 will not tip over.

[0049] Third, there may be a case where the tipping condition of formula (4) is satisfied due to the torque dynamically generated by the reaction force when any axis of the robot arm 5 is accelerated.

[0050] For example, at the position of Figure 5 , even when the tipping condition of formula (4) is not satisfied, when the first robotic arm 9 is accelerated counterclockwise about the second axis J2, a clockwise reaction torque is applied to the carriage 4. As a result, there may be a case where the tipping condition of formula (4) is satisfied and the carriage 4 tips over. In this case, the control device 3 limits the magnitude of the counterclockwise acceleration of the first robotic arm 9.

[0051] As described above, according to the robot system 1 of the present embodiment, the torque sensor 12 provided on the robot arm 5 detects the torque acting on the carriage 4, and the control device 3 controls the robot arm 5 in a state where the detected torque does not exceed the tipping torque Ma. Thus, there is an advantage that the robot arm 5 can be operated in a state where the carriage 4 does not tip over while the carriage 4 is stopped.

[0052] In addition, in the present embodiment, a case is illustrated where the movement locus of the robot hand 5 based on the movement instruction is not changed, and the movement speed or the acceleration / deceleration speed is adjusted to prevent the cart 4 from tipping over. Instead, the cart 4 can also be prevented from tipping over by changing the movement locus of the robot hand 5 based on the movement instruction.

[0053] For example, as described above, the tipping moment of the cart 4 changes correspondingly according to the angle θ1 of the rotating body 8 around the first axis J1. In Figure 4 this case, the tipping moment Ma is the smallest when the angle θ1 = 0°, and thus compared with the case where θ1 = 90° as shown in Figure 6 , the case where θ1 = 0° as shown in Figure 5 is more likely to tip over. Therefore, also at each position of the movement of the robot hand 5, when the moment detected by the torque sensor 12 approaches the tipping moment Ma of the angle θ1 at this time point, the rotating body 8 can be rotated to an angle θ1 where the tipping moment Ma becomes larger.

[0054] In addition, for example, when the cart 4 is self-propelled and the first robot arm 9 rotates clockwise in Figure 5 , if the first robot arm 9 is decelerated, the cart 4 will tip forward, then the control device 3 controls the cart 4 to accelerate in the forward direction. Thereby, the moment applied by the robot hand 5 to the cart 4 can be reduced, and the cart 4 can be prevented from tipping over.

[0055] Or, when the first robot arm 9 rotates clockwise in Figure 5 , if the first robot arm 9 is decelerated, the cart 4 will tip forward, then the second robot arm 10 is accelerated clockwise relative to the first robot arm 9 around the third axis J3.

[0056] In this case, the center-of-gravity position of the robot hand 5 can be made close to the second axis J2, thereby reducing the moment applied by the robot hand 5 to the cart 4, and a reaction torque generated by the acceleration of the second robot arm 10 is generated on the first robot arm 9, thereby reducing the moment.

[0057] When the rotating body 8 is rotated or the second robot arm 10 is rotated, since it is not the movement of the robot hand 5 based on the movement instruction, it is necessary to confirm that no interference occurs between the mobile platform type robot 2 and the peripheral equipment.

[0058] In addition, in the present embodiment, the torque sensor 12 for detecting the torque about the second axis J2 is provided between the first robotic arm 9. However, the torque sensor 12 may also be built into the rotating body 8 or the base 7, or provided between the carriage 4 and the base 7. Alternatively, a force sensor or a torque sensor, such as an acceleration sensor that detects the force or torque acting on at least one joint, may be used instead.

[0059] In addition, in the present embodiment, the case where the robot hand 5 is controlled in a state where the carriage 4 does not tip over when the robot hand 5 is operated while the carriage 4 is stopped has been described. Alternatively, it may be applied to the case where the robot hand 5 is operated while the carriage 4 is in motion. In this case, it is only necessary to consider adding the torque acting on the carriage 4 due to the acceleration and deceleration of the carriage 4.

[0060] Description of Reference Numerals

[0061] 1: Robot system

[0062] 2: Mobile platform type robot (robot)

[0063] 3: Control device

[0064] 4: Carriage

[0065] 5: Robot hand

[0066] 8: Rotating body

[0067] 9: First robotic arm

[0068] 10: Second robotic arm

[0069] 12: Torque sensor (sensor)

[0070] J1: First axis

[0071] J2: Second axis

[0072] J3: Third axis

[0073] Ma: Tipping moment

Claims

1. A robot system, characterized in that, Comprising: A robot; And A control device for controlling the robot, The robot includes a carriage and a manipulator mounted on the carriage, The manipulator includes sensors for detecting forces or torques acting on more than one joint, Based on the forces or torques detected by the sensors, the control device controls at least one of the manipulator and the carriage in a state where the torque acting on the carriage does not exceed the tipping torque. At each position during the movement of the manipulator relative to the carriage, a differential torque obtained by subtracting the torque acting on the carriage from the tipping torque is calculated, and the movement of the manipulator is decelerated at the time point when the differential torque becomes a predetermined value. The predetermined value is set to be larger than the deceleration torque required to urgently stop the manipulator at each position during the movement of the manipulator relative to the carriage.

2. The robot system according to claim 1, wherein: The sensor detects a torque about a horizontal second axis.

3. The robot system according to claim 2, wherein: The manipulator includes a first robotic arm that is driven to rotate relative to the carriage about the second axis, The sensor is disposed near the second axis.

4. A robot system, characterized in that, Comprising: A robot; And A control device for controlling the robot, The robot includes a carriage and a manipulator mounted on the carriage, The manipulator includes sensors for detecting forces or torques acting on more than one joint, Based on the forces or torques detected by the sensors, the control device controls at least one of the manipulator and the carriage in a state where the torque acting on the carriage does not exceed the tipping torque. The manipulator includes a first robotic arm that is driven to rotate relative to the carriage about a horizontal second axis, During the movement of the first robotic arm relative to the carriage at each position, the control device calculates a differential torque obtained by subtracting the torque acting on the carriage from the tipping torque, and causes the first robotic arm to move at an acceleration or deceleration smaller than the acceleration or deceleration corresponding to the differential torque.

5. The robot system according to claim 4, wherein: The manipulator includes a second robotic arm that is driven to rotate relative to the first robotic arm about a third axis parallel to the second axis, At the time point when the differential torque becomes a predetermined value, the control device moves the second robotic arm in a direction to reduce the torque detected by the sensor.

6. The robot system according to claim 4 or 5, wherein: The manipulator includes a rotating body that is driven to rotate relative to the carriage about a vertical first axis, The first robotic arm is driven to rotate relative to the rotating body about the second axis.

7. The robot system according to claim 6, wherein: At the time point when the differential torque becomes a predetermined value, the control device operates the rotating body in a direction in which the tipping torque is increased.

8. The robot system according to claim 6, wherein the sensor is a torque sensor that detects a torque about the first axis.

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