Robot

Abstract

To provide a robot capable of performing different operational controls on a counterweight according to use purposes.SOLUTION: A robot 100 comprises: a lower arm 104 and an upper arm 106; J1, J2, and J3 axes, which are joints for rotating the respective arms; a connecting arm 110 that is connected to the lower arm and extends, based on the J2 axis, toward a side opposite to the lower arm; a counterweight W attached to the connecting arm; a weight rotation device 112 that is disposed on the connecting arm and rotates the counterweight by deforming the connecting arm; and a control device 114 that controls operation of the joints and the weight rotation device.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a robot having an arm with a counterweight attached thereto. [Background technology]

[0002] Industrial robots equipped with arms are used in production sites such as factories. Industrial robots have multiple arms connected at joints, and perform processing on workpieces by operating the arms.

[0003] For example, Patent Document 1 describes an industrial robot in which a counterbalance unit is provided at a joint of an arm that receives the action of gravity. This counterbalance unit positions the center of gravity of the arm near the joint by reciprocating a weight to move it closer to or away from the joint in response to changes in gravitational torque, thereby reducing the gravitational torque of the arm. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 162491 / 1983 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the industrial robot of Patent Document 1 simply automatically adjusts the counterbalance portion (counterweight) in response to changes in gravitational torque, and the counterweight is used only for so-called gravity compensation.

[0006] In view of the above problems, the present invention aims to provide a robot capable of controlling the movement of a counterweight in different ways depending on the application. [Means for solving the problem]

[0007] In order to solve the above problems, a typical configuration of a robot according to the present invention is characterized by comprising one or more arms, one or more joints for rotating the arms, a connecting arm connected to the arms and extending to the opposite side of the arms relative to the joints, a counterweight attached to the connecting arms, a weight rotating device disposed on the connecting arms and for deforming the connecting arms to rotate the counterweights, and a control device for controlling the operation of the joints and the weight rotating device.

[0008] When the arm is rotated, the control device preferably controls the weight rotating device to accelerate the counterweight in the same direction as the rotation direction of the arm, thereby decelerating the arm.

[0009] When the arm is rotated, the control device preferably controls the weight rotating device to accelerate the counterweight in a direction opposite to the direction of rotation of the arm, thereby accelerating the arm. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a robot that can perform different motion control of a counterweight depending on the application. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram schematically illustrating an overall configuration of a robot according to an embodiment of the present invention. [Figure 2] 2A to 2C are diagrams illustrating the control (operation) for adjusting the rotation torque of the robot in FIG. [Figure 3] 2A and 2B are diagrams illustrating control for decelerating the arm of the robot in FIG. 1. [Figure 4] FIG. 2 is a diagram illustrating control for accelerating the arm of the robot in FIG. [Figure 5] FIG. 10 is a diagram illustrating a robot of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0012] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Dimensions, materials, and other specific values ​​shown in the embodiments are merely examples for facilitating understanding of the invention and, unless otherwise specified, do not limit the present invention. In this specification and drawings, elements having substantially the same functions and configurations are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present invention are not shown.

[0013] 1 is a diagram schematically illustrating the overall configuration of a robot 100 according to an embodiment of the present invention. The robot 100 is an industrial robot used in production sites such as factories, and is shown here as a three-axis vertical articulated robot by way of example.

[0014] However, the present invention is not limited to this, and may be applied to a five-axis, six-axis, or other articulated robot. Specifically, by adding a J4 axis that twists and rotates the upper arm 106, a J5 axis that rotates the manipulator M vertically relative to an installation surface 108 (described later), and a J6 axis that twists and rotates the manipulator M to the robot 100, the present invention can be applied to a six-axis articulated robot.

[0015] 1(a), the robot 100 includes a rotating frame 102, a lower arm 104, an upper arm 106, J1-axis, J2-axis, and J3-axis joints, and a manipulator M. The manipulator M is, for example, a hand or gripper that grasps an object to be grasped, and is attached to the tip of the upper arm 106.

[0016] The J1 axis of the robot 100 is an axis that is approximately perpendicular to the installation surface 108. The swivel frame 102 rotates horizontally by the J1 axis in a plane that is approximately parallel to the installation surface 108. The J2 axis and the J3 axis are horizontal axes that are supported in a direction that is approximately parallel (horizontal) to the installation surface 108. The lower arm 104 is rotatably connected to the swivel frame 102 via the J2 axis, and rotates vertically with respect to the installation surface 108. The upper arm 106 is rotatably connected to the lower arm 104 via the J3 axis, and rotates vertically with respect to the installation surface 108.

[0017] The robot 100 further includes a connecting arm 110, a counterweight W, a weight rotating device 112, and a control device 114. The connecting arm 110 is connected to the lower arm 104 and extends on the opposite side of the lower arm 104 with respect to the J2 axis, which is a joint. The counterweight W is attached to the extending end of the connecting arm 110.

[0018] The weight rotating device 112 is a device disposed on the connecting arm 110, and is located between the J2 axis and the counterweight W. The weight rotating device 112 has a Ja axis that mainly operates the counterweight W, and a Jb axis that rotates in a twisting motion. The Ja axis changes the position of the counterweight W (the posture resulting from the rotation) and applies acceleration (the rotation motion itself) to the counterweight W.

[0019] The Jb axis twists and rotates to change the direction in which the Ja axis rotates the counterweight W. In FIG. 1(a), the Ja axis is in a position where it rotates vertically relative to the installation surface 108, but as the Jb axis twists and rotates as shown by the arrow in FIG. 1(b), it assumes a position where it rotates in a direction that includes a horizontal component.

[0020] This allows the weight rotating device 112 to rotate the counterweight W by the Ja axis and the Jb axis so as to deform, specifically, to bend, the connecting arm 110 (see FIG. 3). The control device 114 also controls the operation of the J1 axis, the J2 axis, the J3 axis and the weight rotating device 112.

[0021] 5 is a diagram illustrating a comparative example (conventional example) robot 100A. Robot 100A differs from robot 100 described above in that a weight rotating device 112 is not provided on connecting arm 110A.

[0022] The connecting arm 110A is connected to the lower arm 104 and extends on the opposite side of the lower arm 104 with the J2 axis, which is a joint, as the reference. A counterweight W is attached to the extending end of the connecting arm 110A. In other words, the counterweight W is disposed on the opposite side of the manipulator M with the J2 axis as the center.

[0023] In the robot 100A, the counterweight W is used to configure a so-called gravity compensation mechanism, which is a mechanism for mechanically canceling the weight of the lower arm 104 and the upper arm 106.

[0024] Therefore, in the robot 100A, by balancing the manipulator M side and the counterweight W side, the law of conservation of angular momentum shown in the following equation (1) holds true. P M ×r1=P W ×r2 …Formula (1)

[0025] In equation (1), P M is the momentum of manipulator M, r1 is the horizontal distance of manipulator M from the J1 axis, P W indicates the momentum of the counterweight W, and r2 indicates the horizontal distance of the counterweight W from the J1 axis.

[0026] The robot 100A uses a gravity compensation mechanism using a counterweight W to reduce the load on the installation surface 108 and the J2 axis when stopped or operating in the vertical direction (raising and lowering the arm) and horizontal direction (rotating the J1 axis). This makes it possible to reduce the difficulty of control and to increase safety by reducing motor output. However, the robot 100A of the comparative example uses the counterweight W only for gravity compensation.

[0027] In contrast to this, in the robot 100 of this embodiment, by arranging the weight rotating device 112 on the connecting arm 110, different motion control can be performed on the counterweight W depending on the application. This will be specifically described below.

[0028] Fig. 2 is a diagram illustrating the control (operation) for adjusting the rotation torque of the robot 100 in Fig. 1. In the robot 100, when it is desired to position the manipulator M attached to the tip of the upper arm 106, high precision is required in the operation of the lower arm 104 and the upper arm 106.

[0029] When such precision in the hand is required, the control device 114 controls the weight rotating device 112 to move the counterweight W away from the J1 axis.

[0030] Specifically, in the robot 100, when the control device 114 rotates the Ja axis to move the counterweight W away from the J1 axis (the horizontal distance D1 from the J1 axis) as shown in Figure 2(a), the torque for rotating the J1 axis increases, and the rotation speed slows down. Even if no balance is achieved, such as with gravity compensation, the effect of inertia can be reduced by slowing down the rotation speed, and the precision of the hand can be improved.

[0031] Furthermore, in the robot 100, by balancing the manipulator M side and the counterweight W side (gravity compensation), the torque in the direction of tilting the J1 axis is reduced, the load on the J1 axis is reduced, and deformation and vibration can be suppressed. As a result, the robot 100 can operate the manipulator M with high precision when precision in the hand is required.

[0032] Furthermore, for example, when simply changing the horizontal position of the upper arm 106 or returning it to its initial position, precision is not required in the operation of the lower arm 104 and the upper arm 106, and priority is given to the rotation speed. In such cases, the control device 114 controls the weight rotating device 112 to move the counterweight W closer to the J1 axis.

[0033] Specifically, in the robot 100, when the control device 114 rotates the Ja axis to bring the counterweight W closer to the J1 axis (the horizontal distance D2 from the J1 axis) as shown in Figure 2(b), the torque for rotating the J1 axis decreases (if the motor output is constant), and the rotation speed increases due to the law of conservation of angular momentum. Therefore, the robot 100 can operate the manipulator M at high speed when rotation speed is given priority.

[0034] In this way, according to the robot 100, by performing different motion control on the counterweight W depending on the application, it is possible to operate the manipulator M with high precision or at high speed.

[0035] Furthermore, in the robot 100, when rotation speed is a priority, the counterweight W is brought closer to the J1 axis with the connecting arm 110 folded upward as shown in Figure 2(b). This reduces the rotation radius of the entire robot 100, prevents the counterweight W from getting in the way, and improves safety.

[0036] FIG. 3 is a diagram illustrating control for decelerating the arm of the robot 100 in FIG. 1. FIG. 3(a) is a top view of the robot 100, showing a state in which the Jb axis has been rotated as shown in FIG. 1(b) and the orientation has been changed so that the Ja axis rotates with a horizontal component. Note that in FIG. 3(a), the J2 axis is omitted and the J3 axis is depicted small. FIG. 3(b) shows a further simplified version of the robot 100, omitting the Ja axis and Jb axis from FIG. 3(a).

[0037] In the robot 100, it is assumed that the control device 114 rotates the J1 axis as shown in Figure 3(a) to apply torque T1 to the manipulator M. At this time, if the Ja axis is rotated in the "same direction as the J1 axis" by applying torque to the counterweight W, a force in the folding direction (direction to fold the connecting arm 110) is applied to the parts of the connecting arm 110 in front of and behind the Ja axis. In other words, a reaction force is applied to the part of the connecting arm 110 between the Ja axis and the J1 axis.

[0038] In the robot 100, the position of the Ja axis is not fixed, but only the position of the J1 axis is fixed. Therefore, the portion of the connecting arm 110 between the Ja axis and the J1 axis rotates due to the circumferential component of the torque applied to the counterweight W, centered on the J1 axis. Even if the counterweight W accelerates due to the rotation of the Ja axis, the existence of the Ja axis as an axis can be ignored because it is not fixed (see FIG. 3(b)).

[0039] In other words, the counterweight W moves "approaching while rotating around the J1 axis," and if the acceleration torque of the circumferential component of the counterweight W at that time is T2, then the following equation (2) holds true. T2=J×α…Equation (2)

[0040] In equation (2), J is the moment of inertia of the counterweight W (kg m 2 ), and α is the angular acceleration (rad / s 2 ) The moment of inertia J is proportional to the weight of the counterweight W and the square of the distance r3 from the J1 axis.

[0041] As a result, a reaction force (counter torque T2r) acts on the lower arm 104 and upper arm 106 on the manipulator M side in a direction opposite to the rotation direction of the counterweight W, as shown in FIGS. 3(a) and 3(b).

[0042] Therefore, in the robot 100, when the control device 114 controls the weight rotating device 112 to rotate the counterweight W with torque T2 in the "same direction" as the rotation direction of the manipulator M and accelerate it, a counter torque T2r is generated due to inertia. Then, the torque T1 that rotates the manipulator M about the J1 axis is attenuated by the counter torque T2r. In other words, the counter torque T2 helps to decelerate the lower arm 104 and the upper arm 106.

[0043] As an example, the robot 100 may be provided with a stopper that restricts the rotation of the swivel frame 102. In such a case, the counterweight W is accelerated in the same direction as the rotation of the arm to decelerate the arm immediately before the swivel frame 102 collides with the stopper. This makes it possible to mitigate the impact when the swivel frame 102 collides with the stopper.

[0044] Figure 4 is a diagram illustrating control for accelerating the arm of the robot 100 in Figure 1. Figures 4(a) and 4(b) are top views of the robot 100, and correspond to Figures 3(a) and 3(b), respectively.

[0045] In the robot 100, suppose that the control device 114 rotates the J1 axis as shown in Figure 4(a) to apply torque T1 to the manipulator M. At this time, if the Ja axis is rotated in the "opposite direction to the J1 axis" by applying torque to the counterweight W, a force in the opposite direction to the direction bending the connecting arm 110 is applied to the parts of the connecting arm 110 before and after the Ja axis. In other words, a reaction force is applied to the part of the connecting arm 110 between the Ja axis and the J1 axis.

[0046] The portion of the connecting arm 110 between the Ja axis and the J1 axis rotates due to the circumferential component of the torque applied to the counterweight W, centered on the J1 axis. Note that the Ja axis is not fixed, so its existence as an axis can be ignored (see FIG. 4(b)).

[0047] Here, if the acceleration torque of the circumferential component of the counterweight W is T3, a reaction force (reaction torque T3r) acts on the lower arm 104 and upper arm 106 on the manipulator M side in the same direction as the rotation direction of the counterweight W, as shown in Figures 4(a) and 4(b).

[0048] That is, in the robot 100, when the control device 114 controls the weight rotating device 112 to rotate and accelerate the counterweight W in the "opposite direction" to the rotation direction of the manipulator M, a counter torque T3r is generated. This counter torque T3r assists (assists in acceleration) the torque T1 that rotates the manipulator M by the J1 axis.

[0049] As a result, in the robot 100, the torque for rotating the lower arm 104 and the upper arm 106 increases, allowing the lower arm 104 and the upper arm 106 to operate at high speed. If the arms were rotated at the same speed, it would be possible to reduce the power consumption and size of the motors in the joints.

[0050] In the robot 100, the configuration for rotating the counterweight W is not limited to the configuration of the weight rotating device 112 described above, and any appropriate configuration can be adopted as long as it is arranged on the connecting arm 110 and can rotate the counterweight W by deforming the connecting arm 110.

[0051] While the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such examples. It is clear that those skilled in the art can conceive of various modifications and alterations within the scope of the claims, and it is understood that such modifications and alterations also fall within the technical scope of the present invention. [Industrial Applicability]

[0052] The present invention is applicable to robots that include an arm with a counterweight attached. [Explanation of symbols]

[0053] 100, 100A...robot, 102...swivel frame, 104...lower arm, 106...upper arm, 108...mounting surface, 110, 110A...connecting arm, 112...weight rotation device, 114...control device, J1, J2, J3, Ja, Jb...each axis, J1, J2, J3...joint, M...manipulator, W...counterweight

Claims

1. one or more arms; one or more joints for rotating the arm; a connecting arm connected to the arm and extending to the opposite side of the arm with respect to the joint; a counterweight attached to the connecting arm; a weight rotating device disposed on the connecting arm and configured to deform the connecting arm to rotate the counterweight; a control device that controls the operation of the joint and the weight rotating device.

2. 2. The robot according to claim 1, wherein the control device controls the weight rotating device when rotating the arm to accelerate the counterweight in the same direction as the rotation direction of the arm and decelerate the arm.

3. 2. The robot according to claim 1, wherein the control device controls the weight rotating device when rotating the arm to accelerate the counterweight in a direction opposite to the direction of rotation of the arm, thereby accelerating the arm.

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