Robot system, state detection method, and detection device

Abstract

To provide a robot system, a state detection method, and a detection device capable of detecting a state with high accuracy and performing work with high accuracy.SOLUTION: A robot system includes: a robot which includes a base and a robot arm having an arm connected via a joint portion that includes a motor and a planetary gear speed reducer, and connected to the base; and a detection device which has an acquisition unit that acquires a current value caused by counter electromotive force generated in the motor, and a detection unit that detects a state of the robot on the basis of the current value acquired by the acquisition unit.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a robot system, a state detection method, and a detection device.

Background Art

[0002] There is known a robot having a robot arm including a plurality of arms and joint portions that rotatably connect adjacent arms, and driving the robot arm to a desired posture to perform work on a workpiece. The robot arm has a plurality of joint portions, and a joint mechanism is installed in each joint portion as a driving portion for rotationally driving the arm. The joint mechanism has a motor as a drive source and a speed reducer for reducing the rotational speed of the motor.

[0003] For example, in Patent Document 1, a harmonic drive type speed reducer is used as the speed reducer of the joint mechanism. Encoders are respectively installed on the input shaft and the output shaft of the harmonic drive type speed reducer, and the torque of the motor is estimated by calculating the torsional angle from the difference between the encoder values of each encoder, and the collision of the robot arm is detected.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, since the collision detection method described in Patent Document 1 utilizes the torsion of the speed reducer, the rigidity of the joint mechanism is lowered. Therefore, the robot arm is likely to vibrate. As a result, it becomes difficult for the robot arm to perform highly accurate operations.

Means for Solving the Problems

[0006] The robot system of the present invention has a base and an arm connected via a joint portion including a motor and a planetary gear type reducer, and includes a robot arm connected to the base. It includes a detection device having an acquisition unit that acquires a current value due to a back electromotive force generated by the motor, and a detection unit that detects the state of the robot based on the current value acquired by the acquisition unit.

[0007] The state detection method of the present invention is a state detection method for detecting the state of a robot having a base and an arm connected via a joint portion including a motor and a planetary gear type reducer, and including a robot arm connected to the base, a first step of acquiring a current value due to a back electromotive force generated by the motor, and a second step of detecting the state of the robot based on the current value acquired in the first step.

[0008] The detection device of the present invention is a detection device for detecting the state of a robot having a base and an arm connected via a joint portion including a motor and a planetary gear type reducer, and including a robot arm connected to the base, having an acquisition unit that acquires a current value due to a back electromotive force generated by the motor, and a detection unit that detects the state of the robot based on the current value acquired by the acquisition unit.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0010] Hereinafter, the robot system, state detection method, and detection device of the present invention will be described in detail based on the embodiments shown in the accompanying drawings.

[0011] <First Embodiment> FIG. 1 is a schematic configuration diagram of a robot system according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of a planetary gear type reducer provided in the robot shown in FIG. 1. FIG. 3 is a perspective view showing the internal structure of the planetary gear type reducer shown in FIG. 2. FIG. 4 is a block diagram of the robot system shown in FIG. 1. FIG. 5 is a diagram for explaining the rotational direction of the first arm provided in the robot shown in FIG. 1 and the direction in which force is applied, and is a view seen from directly above vertically. FIG. 6 is a flowchart for explaining an example of the state detection method of the present invention.

[0012] Note that the vertical direction in FIG. 1 coincides with the vertical direction, and the upper side in FIG. 1 is also referred to as "upper" and the lower side as "lower". For the robot arm 72, the first arm 73, and the second arm 74, the right side in FIG. 1 is referred to as the "base end portion" and the left side as the "tip end portion".

[0013] In addition, in this specification, the term "vertical" includes not only the case where it coincides with the vertical direction, but also the case where it is inclined slightly with respect to the vertical direction, for example, within ±10°. Further, in this specification, the term "parallel" includes not only the case where two objects coincide with each other in parallel, but also the case where they are inclined slightly from the parallel direction, for example, within ±10°.

[0014] The robot system 1 shown in FIG. 1 includes a robot 7 and a detection device 8 of the present invention that controls the driving of each part of the robot 7 and detects an abnormal state of the robot 7.

[0015] The robot 7 in the present embodiment is a scalar robot and is used, for example, in various operations such as holding, transporting, assembling, processing, painting, and inspecting workpieces such as electronic components (hereinafter these are collectively referred to as "operations"). However, the use and type of operations of the robot 7 are not particularly limited. Further, the robot 7 may be, for example, a 6-axis articulated robot, a dual-arm robot, etc. other than a scalar robot.

[0016] As shown in FIG. 1, the robot 7 includes a base 71 and a robot arm 72 rotatably connected to the base 71.

[0017] The base 71 is installed on the floor surface of a workroom in a factory or the like. The base 71 may be installed at a location other than the floor surface, for example, on a wall surface, ceiling, pedestal, moving table, etc.

[0018] The detection device 8 is installed inside the base 71. However, it is not limited to this configuration, and the detection device 8 may be installed at a location other than the base 71.

[0019] The robot arm 72 has a first arm 73 whose base end is connected to the base 71 and rotates around a first rotation axis J1 along the vertical direction with respect to the base 71, and a second arm 74 whose base end is connected to the tip of the first arm 73 and rotates around a second rotation axis J2 along the vertical direction with respect to the first arm 73.

[0020] A working head 75 is provided at the tip of the second arm 74. The working head 75 has a spline nut 751 and a ball screw nut 752 that are coaxially arranged at the tip of the second arm 74, and a spline shaft 753 that is inserted through the spline nut 751 and the ball screw nut 752. The spline shaft 753 is rotatable about a third rotation axis J3, which is its central axis and extends in the vertical direction, with respect to the second arm 74, and is movable up and down in the direction along the third rotation axis J3.

[0021] An end effector 76 is attached to the lower end of the spline shaft 753. The end effector 76 is detachable from the spline shaft 753, and an appropriate one suitable for the intended work is selected as appropriate. The end effector 76 may be, for example, a tool such as a grinding machine, a milling machine, a cutting machine, a spray gun, a laser light irradiator, a driver, or a wrench.

[0022] The first joint portion 2K rotatably connects the base 71 and the first arm 73, and has a motor unit 2 that rotates the first arm 73 about a first rotation axis J1 with respect to the base 71.

[0023] The second joint portion 3K rotatably connects the first arm 73 and the second arm 74, and has a motor unit 3 that rotates the second arm 74 about a second rotation axis J2 with respect to the first arm 73.

[0024] The third joint portion 4K connects the spline shaft 753 to be movable up and down along the third rotation axis J3 with respect to the second arm 74, and has a first drive mechanism 4 that rotates the ball screw nut 752 to move the spline shaft 753 up and down in the direction along the third rotation axis J3.

[0025] The fourth joint portion 5K rotatably connects the spline shaft 753 to be rotatable about the third rotation axis J3 with respect to the second arm 74, and has a second drive mechanism 5 that rotates the spline nut 751 to rotate the spline shaft 753 about the third rotation axis J3.

[0026] The motor unit 2 includes a motor 21 and a power transmission mechanism 22 that uses the motor 21 as a driving source. The motor 21 generates a driving force for rotating the first arm 73 with respect to the base 71.

[0027] The motor unit 3 includes a motor 31 and a power transmission mechanism 32 that uses the motor 31 as a driving source. The motor 31 generates a driving force for rotating the second arm 74 with respect to the first arm 73.

[0028] The first drive mechanism 4 includes a motor 41 and a power transmission mechanism 42 that uses the motor 41 as a driving source. The motor 41 generates a driving force for rotating the ball screw nut 752 to move the spline shaft 753 up and down in the direction along the third rotation axis J3.

[0029] The second drive mechanism 5 includes a motor 51 and a power transmission mechanism 52 that uses the motor 51 as a driving source. The motor 51 generates a driving force for rotating the spline nut 751 to rotate the spline shaft 753 around the third rotation axis J3.

[0030] The motors 21, 31, 41, and 51 are not particularly limited, and examples include servo motors such as AC servo motors and DC servo motors.

[0031] Although not shown in the drawings, the motors 21, 31, 41, and 51 include a stator, a rotor that rotates inside the stator, and a case that houses them. The stator is arranged along the inner circumference of the case and has a winding such as a three-phase winding, for example. The stator generates a magnetic field by energizing the winding, for example, by applying three-phase alternating current. In the motors 21, 31, 41, and 51, the energization pattern, energization timing, energization amount, etc. of each winding provided in the stator are controlled by the detection device 8. As a result, the motors 21, 31, 41, and 51 rotate at desired timings, rotation directions, and speeds, respectively.

[0032] The power transmission mechanism 22 has a first speed reducer 23. The power transmission mechanism 32 has a second speed reducer 33. The power transmission mechanism 42 has pulleys and belts (not shown). The power transmission mechanism 52 has pulleys and belts (not shown).

[0033] The first speed reducer 23 and the second speed reducer 33 are each a planetary gear type speed reducer. Since the first speed reducer 23 and the second speed reducer 33 have the same configuration except for different weights as will be described later, the first speed reducer 23 will be typically described below.

[0034] As shown in FIGS. 2 and 3, the first speed reducer 23 includes a frame 231, an internal gear 233, a sun gear 234, a plurality of, three planetary gears 235 in this embodiment, a carrier 236, an input shaft 237, and an output shaft 238. In FIG. 3, for easy viewing of the internal structure, the input shaft 237 and the output shaft 238 are shown thinner than actual. The first speed reducer 23 may have an elastic support member outside the internal gear 233. The elastic support member enables radial deformation of the internal gear 233 due to the action of stress and has a strength such that the phase does not shift with respect to the frame 231 in the circumferential direction.

[0035] As shown in FIG. 2, the frame 231 is a cylindrical casing and has a function of protecting each member inside it.

[0036] As shown in FIG. 3, the internal gear 233 has a ring shape or a cylindrical shape centered on the axis O1 and has internal teeth 233A on its inner peripheral portion. The internal teeth 233A mesh with the teeth 235A of each planetary gear 235.

[0037] The sun gear 234 has teeth 234A on its outer peripheral portion and is disposed inside the internal gear 233 and at a concentric position with the internal gear 233. The sun gear 234 is connected to the input shaft 237 and rotates around the axis O1. The input shaft 237 is connected to the rotation shaft of the motor 21 via, for example, a bearing (not shown). The motor 21 is fixed to the base 71 directly or indirectly (not shown).

[0038] The three planetary gears 235 are arranged at equal angular intervals on the outer peripheral side of the sun gear 234 and on the inner peripheral side of the internal gear 233. Each planetary gear 235 has teeth 235A on its outer peripheral portion, and the teeth 235A mesh with the teeth 234A of the sun gear 234 and the internal teeth 233A of the internal gear 233. The three planetary gears 235 are equal in diameter and the number of teeth 235A respectively.

[0039] As shown in FIGS. 2 and 3, the gear trains of the sun gear 234 and the three planetary gears 235 are provided in a row on the same plane, that is, on a predetermined cross section of the first speed reducer 23. Also, the types, forms, etc. of the internal gear 233, the sun gear 234, and the planetary gear 235 are not particularly limited, and in the illustrated configuration, they are spur gears respectively. However, in the present invention, the internal gear 233, the sun gear 234, and the planetary gear 235 are preferably involute gears respectively.

[0040] The carrier 236 rotatably supports the planetary gears 235 around the axis O2 which is the central axis of the planetary gears 235. In the illustrated configuration, the carrier 236 has a shape in which three rod-shaped members arranged at 120° intervals are connected at their ends on the axis O1 side, so-called star shape. However, it is not limited to this configuration, and the carrier 236 may be composed of, for example, a frame-shaped member or a disk-shaped member.

[0041] An output shaft 238 is connected to the central portion of the carrier 236. The output shaft 238 is fixed to the base end portion of the first arm 73 via, for example, a bearing (not shown).

[0042] The rotational force transmitted from the motor 21 is transmitted to the sun gear 234 via the input shaft 237, and the sun gear 234 rotates in a predetermined direction around the axis O1. When the sun gear 234 rotates, each planetary gear 235 rotates (rotates on its own axis) around the axis O2 while rotating (revolves) around the axis O1. Due to the revolution of each planetary gear 235 around the axis O1, the carrier 236 rotates around the axis O1, and the output shaft 238 rotates around the axis O1. As a result, the rotation of the output shaft 238 is decelerated by the planetary gear 235 and is slower than the rotation of the input shaft 237. Therefore, the rotational speed of the input shaft 237 is decelerated and output from the output shaft 238. As a result, the first arm 73 can be rotated relative to the base 71 at a decelerated speed, and the rotational torque of the first arm 73 can be increased.

[0043] The rotation speed ratio of the output shaft 238 with respect to the input shaft 237, that is, the reduction ratio of the first speed reducer 23, is not particularly limited, but the preferred range will be described later.

[0044] Although not shown, the input shaft of the second speed reducer 33 is connected to a motor 31 fixed to the base end portion of the second arm 74, and the output shaft of the second speed reducer 33 is fixed to the tip end portion of the first arm 73.

[0045] Conversely, the input shaft of the second speed reducer 33 may be connected to a motor 31 fixed to the tip end portion of the first arm 73, and the output shaft of the second speed reducer 33 may be fixed to the base end portion of the second arm 74.

[0046] And, based on the same principle as above, the second arm 74 can rotate with respect to the first arm 73.

[0047] The internal gear 233 is more elastic than the sun gear 234 and the planetary gear 235. However, it is sufficient that the internal gear 233 is more elastic than the planetary gear 235. Thereby, backlash can be suppressed, and the position accuracy of each part during the operation of the robot arm 72 can be further improved.

[0048] As used herein, "elasticity" is determined not only by the material but also by the shape, etc., and refers to the property that the deformation occurring when a force is applied to an object returns to its original state when the application of the force is released. A high elasticity means that the speed of returning to the original state is fast when the application of the force is released. That is, "elasticity" as used herein is different from the property determined by the material such as Young's modulus.

[0049] The frame 231, the internal gear 233, the sun gear 234, the planetary gears 235, the carrier 236, the input shaft 237, and the output shaft 238 are made of, for example, a metal material or a hard resin material.

[0050] Thus, the first speed reducer 23 which is a planetary gear type speed reducer includes a ring-shaped internal gear 233, a sun gear 234 disposed inside the internal gear 233 and concentric with the internal gear 233, a plurality of planetary gears 235 meshing with both the internal gear 233 and the sun gear 234, and a carrier 236 rotatably supporting each planetary gear 235. The internal gear 233 has higher elasticity than the planetary gears 235. Thereby, backlash can be suppressed, and the position accuracy of each part of the robot arm 72 can be further improved. As a result, the work by the operation of the robot arm 72 can be performed more accurately.

[0051] Note that the present invention is not limited to the above configuration, and the internal gear 233 may have the same elasticity as the planetary gears 235, or may have lower elasticity than the planetary gears 235.

[0052] In the first speed reducer 23, the gear trains of the sun gear 234 and the plurality of planetary gears 235 are provided in one row. By minimizing the number of gear trains in this way, in the first speed reducer 23, the loss during torque transmission can be reduced. Furthermore, the weight reduction of the first speed reducer 23 can be achieved.

[0053] The internal gear 233, the sun gear 234, and the planetary gear 235 are each preferably a helical gear. That is, the internal gear 233, the sun gear 234, and the planetary gear 235 are preferably helical gears. Thereby, the meshing area between the teeth can be increased compared to spur gears, and the surface pressure on the tooth surface can be reduced. Therefore, relatively high torque can be transmitted smoothly and efficiently.

[0054] Note that the present invention is not limited to the above configuration, and the internal gear 233, the sun gear 234, and the planetary gear 235 may be other types of gears such as spur gears.

[0055] Such planetary gear type speed reducers (the first speed reducer 23 and the second speed reducer 33) have the following advantages 1, 2, and 3.

[0056] (Advantage 1) Compared with a harmonic gear type speed reducer having the same maximum outer diameter, the viscous resistance of the grease is low and the torque loss is small. Therefore, when operating at the same rotational speed, using a planetary gear type speed reducer enables sensitive operation while suppressing power consumption.

[0057] (Advantage 2) Compared with a harmonic gear type speed reducer, the rigidity is high, and in particular, vibration of the output shaft 238 can be suppressed.

[0058] (Advantage 3) Compared with a harmonic gear type speed reducer, the reverse drive efficiency is good. That is, in a rotation in which the output shaft 238 is used as the input side and the input shaft 237 is used as the output side, the torque loss is small. Therefore, the correlation between the input and the output, that is, the correlation between the stress received by the collision of the robot arm 72 and the back electromotive force generated in the motors 21 and 31 is high, and the responsiveness of the output to the input is high.

[0059] Note that not all of the speed reducers 23 and 33 need to be planetary gear type speed reducers, and for example, speed reducers such as an eccentric swing type or a harmonic gear type may be used. However, at least one is constituted by a planetary gear type speed reducer.

[0060] The power transmission mechanisms 42 and 52 had a configuration having a belt and pulleys, but the present invention is not limited thereto, and various speed reducers as described above may be used.

[0061] In such a robot 7, when a force is applied to the motors 21, 31, 41, and 51 such that they rotate in a direction opposite to the driving direction under the control of the detection device 8, a back electromotive force is generated. For example, as shown in FIG. 5, when a force in the direction of arrow B is applied to the first arm 73 rotating in the direction of arrow A due to, for example, a collision with an object, a back electromotive force is generated in the motor 21. On the other hand, when a force in the direction of arrow C is applied to the first arm 73 rotating in the direction of arrow A, an overcurrent is generated in the motor 21.

[0062] Depending on the moving direction of each of the arms 73 and 74, the types of the motors 21, 31, 41, and 51, the situation such as whether it is during work or direct teaching, etc., which motor generates a back electromotive force or an overcurrent varies. Hereinafter, the case where the first arm 73 is rotating in the direction of arrow A in FIG. 5 around the first rotation axis J1 will be described.

[0063] The detection device 8 detects the state of the robot 7 based on the current value of the back electromotive force. The "state of the robot" includes an abnormal state. The abnormal state of the robot 7 means a state in which an object such as a person, a workpiece, a tool, another robot, or an obstacle in the surroundings (hereinafter collectively referred to as "object" in this specification) contacts or collides with the robot 7, a failure of each part as described in the second embodiment, etc., and an event other than the operation of executing a pre-specified operation program occurs to the robot 7. Hereinafter, the state where an object contacts the robot arm 72 will be described as an abnormal state. Note that the "state of the robot" includes, in addition to the abnormal state, for example, a state during the execution of direct teaching.

[0064] As shown in FIG. 4, the detection device 8 includes a control unit 81, a storage unit 82, and a communication unit 83.

[0065] The control unit 81 is composed of, for example, at least one CPU (Central Processing Unit), reads out and executes various programs such as operation programs stored in the storage unit 82. The signals generated by the control unit 81 are transmitted to each part of the robot 7 via the communication unit 83, and the signals from each part of the robot 7 are received by the control unit 81 via the communication unit 83.

[0066] The storage unit 82 stores various programs and the like executed by the control unit 81. Examples of the storage unit 82 include those configured to have a volatile memory such as a RAM (Random Access Memory), a non-volatile memory such as a ROM (Read Only Memory), a removable external storage device, and the like.

[0067] The storage unit 82 stores programs and the like for executing the state detection method of the present invention. By the control unit 81 reading out and executing the program, the state detection method of the present invention can be executed.

[0068] The communication unit 83 transmits and receives signals between the detection device 8 and the robot 7 or external devices using an external interface such as a wired LAN (Local Area Network) or a wireless LAN. In this case, communication may be performed via a server (not shown), or communication may be performed via a network such as the Internet.

[0069] As shown in FIG. 4, the control unit 81 has, as functional units, a drive control unit 811, an acquisition unit 812, and a detection unit 813. These functional units can control the drive of the robot arm 72 and detect an abnormal state of the robot 7.

[0070] The drive control unit 811 controls the energization conditions for the motors 21, 31, 41, and 51 according to the program stored in the storage unit 82. That is, the drive control unit 811 generates drive signals for the motors 21, 31, 41, and 51, outputs these drive signals to drive the motors 21, 31, 41, and 51, and controls the operation of the robot arm 72. Thereby, the robot arm 72 can operate as per the program.

[0071] The acquisition unit 812 acquires the current value due to the back electromotive force generated in the motor 21. As described above, when the robot arm 72 contacts an object during the driving of the robot arm 72, a back electromotive force is generated in the motor 21 due to the reaction force.

[0072] During the driving of the robot arm 72, the acquisition unit 812 monitors whether a back electromotive force is generated in the motor 21, and when a back electromotive force is generated, calculates its current value. For example, as shown in FIG. 5, when a force in the direction of arrow B is applied to the first arm 73 rotating in the direction of arrow A, a back electromotive force is generated in the motor 21.

[0073] Note that the acquisition unit 812 may be configured to obtain the current value calculated by another processor without performing the calculation of the current value.

[0074] The detection unit 813 detects an abnormal state of the robot 7 based on the current value acquired by the acquisition unit 812. Specifically, when the detection unit 813 determines that the current value acquired by the acquisition unit 812 has reached a predetermined value I0 which is the threshold value, it determines that an object has contacted the robot arm 72. That is, when the current value acquired by the acquisition unit 812 is IA and the predetermined value is I0, the detection unit 813 determines that an object has contacted the robot arm 72 when it determines that IA ≧ I0 is satisfied.

[0075] The predetermined value I0 is a value at which it can be considered that an object has contacted, and can be obtained experimentally in advance, for example. The predetermined value I0 is stored in the storage unit 82.

[0076] When the detection unit 813 detects an abnormal state, the drive control unit 811 generates a drive signal for the robot arm 72 to stop or decelerate, outputs this drive signal, and controls the drive of the motor 21. Thereby, safety can be enhanced.

[0077] According to such a detection device 8, an abnormal state of the robot 7 can be detected based on the current value due to the back electromotive force generated in the motor 21. In particular, as described above, since the planetary gear type reduction gear has the above-described advantage 2, it is superior in vibration damping property compared to the harmonic gear type reduction gear.

[0078] Furthermore, since it has the above-described advantage 3, as shown in FIG. 5, when a force in the direction of arrow B is applied to the first arm 73 rotating in the direction of arrow A, the force is efficiently and responsively transmitted to the motor 21 via the first reduction gear 23. Therefore, a back electromotive force is generated efficiently and responsively in the motor 21.

[0079] From the above, in the robot 7 having the first reduction gear 23 which is a planetary gear type reduction gear, if it is configured to detect an abnormal state of the robot 7 based on the current value due to the back electromotive force generated in the motor 21, the abnormal state can be detected with high accuracy, it is excellent in vibration damping property, and the work by the operation of the robot arm 72 can be performed with high accuracy.

[0080] As described above, the robot system 1 of the present invention includes a base 71, a first arm 73 and a second arm 74 which are arms connected via a first joint portion 2K which is a joint portion including a motor 21 and a first reduction gear 23 which is a planetary gear type reduction gear, and a robot arm 72 connected to the base 71, a robot 7 including the same, an acquisition unit 812 that acquires a current value due to the back electromotive force generated in the motor 21, and a detection unit 813 that detects the state of the robot 7 based on the current value acquired by the acquisition unit 812, and a detection device 8 including the same. Thereby, the state of the robot 7 can be detected with high accuracy, and the work by the operation of the robot arm 72 can be performed with high accuracy.

[0081] The detection device 8 of the present invention includes a base 71, a first arm 73 and a second arm 74 which are arms connected via a first joint portion 2K that is a joint portion including a motor 21 and a first speed reducer 23 which is a planetary gear type speed reducer, and a robot arm 72 connected to the base 71, and detects the state of the robot 7. The detection device 8 has an acquisition unit 812 that acquires a current value due to the back electromotive force generated by the motor 21, and a detection unit 813 that detects the state of the robot 7 based on the current value acquired by the acquisition unit 812. Thereby, the state of the robot 7 can be accurately detected, and the work by the operation of the robot arm 72 can be accurately performed.

[0082] In addition, in the present embodiment, the motor 21 has been described with attention, but the abnormal states as described above can be similarly detected for the motors 31, 41, and 51. The abnormal state may be detected for all of the motors 21, 31, 41, and 51, or the abnormal state may be detected for any one, two, or three of these motors.

[0083] Further, it is also possible to configure to detect the back electromotive forces of a plurality of motors among the motors 21, 31, 41, and 51 and comprehensively determine an abnormal state, that is, contact of the robot arm 72 with an object.

[0084] In the above description, the case where a force in the direction of arrow B is applied to the first arm 73 rotating in the direction of arrow A in FIG. 5 has been described. However, even when a force in the direction of arrow C is applied, the detection unit 813 can detect an abnormal state. When a force in the direction of arrow C is applied to the first arm 73 rotating in the direction of arrow A, for example, due to the collision of an object, the motor 21 rotates in the direction opposite to that when a force in the direction of arrow B is applied. As a result, an overcurrent is generated in the motor 21. The acquisition unit 812 acquires the current value of this overcurrent, and the detection unit 813 detects an abnormal state based on the current value. Specifically, the detection unit 813 compares the current value with a predetermined value, which is the threshold value of the current value. When it is determined that the predetermined value has been reached, it is determined that an object has come into contact with the robotic arm 72. This predetermined value may be the same value as the predetermined value I0 described above, or may be a different value.

[0085] In this way, the acquisition unit 812 acquires the current value in each of the forward and reverse rotation directions of the motor 21. Thereby, an abnormal state, particularly contact or collision of the robotic arm 72 with an object, can be detected in either the forward or reverse direction with respect to the rotation direction of the robotic arm 72.

[0086] Note that the present invention is not limited to the above configuration, and the acquisition unit 812 may be configured to acquire only the current value in the reverse direction of the motor 21.

[0087] When the current value acquired by the acquisition unit 812 reaches a predetermined value, the detection unit 813 determines that an object has come into contact with the robotic arm 72. Thereby, it is possible to accurately detect that an object has come into contact with the robotic arm 72. Therefore, for example, measures such as decelerating or stopping the robotic arm 72 after detection can be taken, contributing to an improvement in safety.

[0088] Note that the present invention is not limited to the above configuration, and the detection unit 813 may be configured to determine that an object has come into contact with the robotic arm 72 when the current value acquired by the acquisition unit 812 exceeds 0.

[0089] Also, when the weight of the power transmission mechanism 22 of the first joint portion 2K is G1, the weight of the power transmission mechanism 32 of the second joint portion 3K is G2, the weight of the power transmission mechanism 42 of the third joint portion 4K is G3, and the weight of the power transmission mechanism 52 of the fourth joint portion 5K is G4, in the robot 7, it is preferable to satisfy the condition that weight G1 > weight G2 > weight G3 > weight G4. That is, the configuration is such that the weight becomes lighter as it goes toward the tip side of the robot arm 72. That is, the power transmission mechanisms 32, 42, and 52 of the second joint portion 3K, the third joint portion 4K, and the fourth joint portion 5K, which are joint portions on the tip side of the first speed reducer 23, are lighter in weight than the first speed reducer 23. By adopting such a configuration, even if a planetary gear type speed reducer is used as the first speed reducer 23, the moment of inertia of the robot arm 72 during operation can be suppressed. Therefore, it is possible to achieve both low power consumption and agile operation.

[0090] Next, an example of the state detection method of the present invention will be described with reference to the flowchart shown in FIG. 6.

[0091] First, in step S101, the drive control unit 811 drives the robot arm 72 based on a previously specified program.

[0092] Next, in step S102, the acquisition unit 812 acquires a current value. That is, the current value due to the back electromotive force generated in the motor 21 is acquired.

[0093] Next, in step S103, the detection unit 813 determines whether the current value is equal to or greater than a predetermined value. That is, it is determined whether IA ≧ I0 is satisfied. In step S103, if it is determined that IA ≧ I0 is satisfied (step S103: YES), the process proceeds to step S104, and if it is determined that IA ≧ I0 is not satisfied (step S103: NO), the process returns to step S102.

[0094] In step S104, the drive control unit 811 generates a drive signal to stop the robot arm 72, outputs this drive signal, and controls the drive of the motor 21 and the like. In this case, normally, only the motor 21 among all the motors 21, 31, 41, and 51 is controlled to stop or decelerate, but it is not limited to this. All the motors 21, 31, 41, and 51 may be stopped or decelerated, or control may be performed to stop or decelerate the motor 21 and any one or more of the motors 31, 41, and 51. Furthermore, control may be performed to stop the motor 21 and decelerate any one or more of the motors 31, 41, and 51.

[0095] When the detection device 8 detects an abnormal state, the "abnormal state" may be notified by a notification unit (not shown). Examples of the notification method of the notification unit include lighting of a lamp, voice notification, display on a display unit such as a display, and the like.

[0096] As described above, the state detection method of the present invention has a first arm 73 and a second arm 74 which are arms connected via a first joint portion 2K which is a joint portion including a base 71 and a motor 21 and a first reduction gear 23 which is a planetary gear type reduction gear, and a robot arm 72 connected to the base 71. It is a state detection method for detecting the state of the robot 7, and includes a first step (step S102) of acquiring a current value due to the back electromotive force generated in the motor 21, and a second step (step S103) of detecting the state of the robot 7 based on the current value acquired in the first step. Thereby, the state of the robot 7 can be accurately detected, and the work by the operation of the robot arm 72 can be accurately performed.

[0097] <Second Embodiment> FIG. 7 is a block diagram of a robot system according to the second embodiment of the present invention.

[0098] Next, a second embodiment of the robot system, state detection method, and detection device of the present invention will be described with reference to FIG. 7. Hereinafter, the description will focus on the differences from the first embodiment, and the description of the same matters will be omitted.

[0099] The robot system 1 of this embodiment includes a robot 7 and a detection device 8 that controls the driving of each part of the robot 7 and detects an abnormal state of the robot 7.

[0100] As shown in FIG. 7, the detection device 8 has a control unit 81, and the control unit 81 includes, as functional units, a drive control unit 811, an acquisition unit 812, a detection unit 813, and a failure prediction unit 814.

[0101] The failure prediction unit 814 predicts failures of each component of the robot 7 as abnormal states. Examples of each component of the robot 7 include motors 21, 31, 41, and 51, a first reduction gear 23, a second reduction gear 33, a spline nut 751, a ball screw nut 752, a belt, a pulley, and the like.

[0102] The failure prediction unit 814 generates a learning model 815 by machine learning. Note that generating the learning model 815 by machine learning means repeatedly learning from input data, finding features, trends, etc. that can be read from each input data, and generating the learning model 815 while applying the results to new input data for prediction.

[0103] The learning model 815 refers to something that receives an input value, performs evaluation and determination, and outputs the result as an output value. The input value is the current value of each of the motors 21, 31, 41, and 51, the detection result of the detection unit 813, information on whether each component of the robot 7 has failed, and the like. The output value is an estimated value of the failure prediction of each component of the robot 7.

[0104] The failure prediction unit 814 can be constructed using, for example, a recurrent neural network. Specifically, the failure prediction unit 814 can have a configuration including an input layer, an intermediate layer, and an output layer. Each piece of information is connected to the information of adjacent layers by the network, and a larger network is developed. Also, it is preferable that a plurality of intermediate layers are provided. Thereby, weighting can be performed on the importance of information in each layer of the intermediate layer, and more accurate failure prediction can be performed.

[0105] Also, in a recurrent neural network, the information of the intermediate layer at the previous time can be replaced with the information of the intermediate layer at the current time to construct a network. Therefore, a network considering time-series information can be constructed. As a result, more accurate failure prediction can be performed.

[0106] Note that as learning methods in the failure prediction unit 814, there are supervised learning, unsupervised learning, and learning methods combining these. In the case of supervised learning, more accurate failure prediction can be performed by reflecting the output value or its pass / fail result in the input value. In the case of unsupervised learning, a large amount of data sets of input value and output value pairs are prepared in advance and given to the failure prediction unit 814, so that a model that learns the characteristics in those data sets and estimates the result from the input, that is, the relationship can be inductively acquired. Therefore, even without information regarding the determination of the pass / fail of failure prediction, an abnormality can be detected. As a result, the omen of the failure of the component parts can be clearly detected. For example, by applying, for example, the error backpropagation method to a recurrent neural network, unsupervised learning becomes possible and an abnormality can be detected.

[0107] In this way, the detection device 8 has a failure prediction unit 814 that predicts the failure of the robot 7 by performing machine learning based on the current values of the motors 21, 31, 41, and 51. Thereby, the failure of the robot 7 can be predicted.

[0108] The failure prediction result by the detection device 8 may be notified by a notification unit (not shown). The notification method of the notification unit is the same as that described in the first embodiment.

[0109] <Third Embodiment> FIG. 8 is a flowchart for explaining an example of a third embodiment of the state detection method of the present invention.

[0110] Hereinafter, a third embodiment of the robot system, the state detection method, and the detection device of the present invention will be described with reference to FIG. 7. Hereinafter, the description will focus on the differences from the first embodiment, and the description of the same matters will be omitted.

[0111] An example of the state detection method of the present invention will be described with reference to the flowchart shown in FIG. 8.

[0112] First, in step S201, the drive control unit 811 drives the robot arm 72 based on a program specified in advance.

[0113] Next, in step S202, the acquisition unit 812 acquires a current value. That is, the current value due to the back electromotive force generated in the motor 21 is acquired.

[0114] Next, in step S203, the detection unit 813 determines whether the current value is greater than or equal to a first threshold value. That is, when the first threshold value is I0A, it is determined whether IA≥I0A is satisfied. The first threshold value I0A is a relatively small value that can be regarded as an object having come into contact, and can be obtained experimentally in advance, for example. The first threshold value I0A is stored in the storage unit 82.

[0115] In step S203, if it is determined that IA≥I0A is satisfied (step S203: YES), the process proceeds to step S206, and if it is determined that IA≥I0A is not satisfied (step S203: NO), the process proceeds to step S204.

[0116] In step S206, a drive signal is generated to reduce the speed of the robot arm 72, and this drive signal is output to control the drive of the motor 21 or the like. That is, in step S206, without stopping the robot arm 72, the speed of the robot arm 72 is reduced to mitigate the impact of contact with the object. Note that which motor is to be controlled is as described in step S104 of the first embodiment described above. Also, when the robot 7 incorporates a brake, the brake may be actuated.

[0117] In step S204, the detection unit 813 determines whether the current value is greater than or equal to the second threshold value. That is, when the second threshold value is I0B, it is determined whether IA≥I0B is satisfied. The second threshold value I0B is a value that is a predetermined value larger than the first threshold value. The second threshold value I0B can be experimentally obtained in advance, for example. The second threshold value I0B is stored in the storage unit 82.

[0118] In step S204, if it is determined that IA≥I0B is satisfied (step S204: YES), the process proceeds to step S205. If it is determined that IA≥I0A is not satisfied (step S203: NO), the process proceeds to step S202, and the following steps are sequentially repeated.

[0119] In step S205, a drive signal is generated to stop the robot arm 72, and this drive signal is output to control the drive of the motor 21 or the like. That is, in step S205, the robot arm 72 is stopped to enhance safety. In this step, all the motors of the motors 21, 31, 41, and 51 are stopped.

[0120] As described above, in this embodiment, two threshold values are prepared, and the control of the drive of the robot arm 72 is varied according to which threshold value is reached. Thereby, according to the degree of the abnormal state, that is, according to the degree of the collision, the control of the robot arm 72 can be performed step by step, and both the improvement of safety and the improvement of work efficiency can be achieved.

[0121] <Fourth Embodiment> FIG. 9 is a schematic configuration diagram of a robot system according to the fourth embodiment of the present invention.

[0122] Hereinafter, a fourth embodiment of the robot system, the state detection method, and the detection device of the present invention will be described with reference to FIG. 9. Hereinafter, the description will focus on the differences from the first embodiment, and the description of the same matters will be omitted.

[0123] As shown in FIG. 9, the robot 7 of the present embodiment is a single-arm six-axis vertical articulated robot in the present embodiment, and includes a base 11 and a robot arm 10. Further, an end effector 20 can be attached to the tip of the robot arm 10. Note that examples of the end effector 20 include those listed in the end effector 76 described in the first embodiment.

[0124] The base 11 is a support that supports the robot arm 10 in a drivable manner at its proximal end side, and is fixed to, for example, the floor in a factory. The robot 7 is electrically connected to the detection device 8 via a relay cable by the base 11. Note that the connection between the robot 7 and the detection device 8 is not limited to a wired connection as in the configuration shown in FIG. 1, and may be a wireless connection, for example. Further, it may be connected via a network such as the Internet.

[0125] In the present embodiment, the robot arm 10 includes a first arm 12, a second arm 13, a third arm 14, a fourth arm 15, a fifth arm 16, and a sixth arm 17, and these arms are connected in this order from the base 11 side.

[0126] The base 11 and the first arm 12 are connected via a joint portion 171. The first arm 12 is rotatable around a first rotation axis extending in the vertical direction with respect to the base 11 as a rotation center. In this way, the first rotation axis coincides with the normal line of the floor surface of the floor on which the base 11 is fixed, and the entire robot arm 10 can rotate in either the positive or negative direction around the axis of the first rotation axis.

[0127] The first arm 12 and the second arm 13 are connected via a joint portion 172. And the second arm 13 can rotate with respect to the first arm 12 about a second rotation axis extending in the horizontal direction as the rotation center.

[0128] The second arm 13 and the third arm 14 are connected via a joint portion 173. And the third arm 14 can rotate with respect to the second arm 13 about a third rotation axis extending in the horizontal direction as the rotation center. The third rotation axis is parallel to the second rotation axis.

[0129] The third arm 14 and the fourth arm 15 are connected via a joint portion 174. And the fourth arm 15 can rotate with respect to the third arm 14 about a fourth rotation axis parallel to the central axis direction of the third arm 14 as the rotation center. The fourth rotation axis is orthogonal to the third rotation axis.

[0130] The fourth arm 15 and the fifth arm 16 are connected via a joint portion 175. And the fifth arm 16 can rotate with respect to the fourth arm 15 about a fifth rotation axis as the rotation center. The fifth rotation axis is orthogonal to the fourth rotation axis.

[0131] The fifth arm 16 and the sixth arm 17 are connected via a joint portion 176. And the sixth arm 17 can rotate with respect to the fifth arm 16 about a sixth rotation axis as the rotation center. The sixth rotation axis is orthogonal to the fifth rotation axis.

[0132] Also, the sixth arm 17 is the robot tip portion located at the most distal side in the robot arm 10. This sixth arm 17 can be displaced together with the end effector 20 by the drive of the robot arm 10.

[0133] The joint parts 171 to 176 each incorporate a motor and a speed reducer (not shown). It is not necessary for all of the speed reducers to be planetary gear type speed reducers. For example, speed reducers such as eccentric swing type or harmonic gear type may be used. However, at least one of them is constituted by a planetary gear type speed reducer. In particular, it is preferable that all of the speed reducers of the joint parts 171 to 176 are constituted by planetary gear type speed reducers, or that all of the speed reducers of the joint parts 171 to 173 are constituted by planetary gear type speed reducers.

[0134] Also in this embodiment, the energization conditions of each motor are controlled by the detection device 8, and an abnormal state is detected in the same manner as in the first embodiment. That is, the acquisition unit 812 acquires the current value due to the back electromotive force generated in at least one of the motors, and the detection unit 813 detects the abnormal state of the robot 7 based on the current value acquired by the acquisition unit 812. Thereby, it is possible to accurately detect an abnormal state and accurately perform the work by the operation of the robot arm 72.

[0135] As described above, the robot system, the state detection method, and the detection device of the present invention have been described based on the illustrated embodiments. However, the present invention is not limited to these, and the configurations and processes of each part in the robot system, the state detection method, and the detection device can be replaced with any configurations and processes having the same functions. Also, other arbitrary components and processes may be added to the robot system, the state detection method, and the detection device.

Description of Reference Numerals

[0136] 1... Robot system, 2... Motor unit, 2K... First joint part, 3... Motor unit, 3K... Second joint part, 4... First drive mechanism, 4K... Third joint part, 5... Second drive mechanism, 5K... Fourth joint part, 7... Robot, 8... Detection device, 10... Robot arm, 11... Base, 12... First arm, 13... Second arm, 14... Third arm, 15... Fourth arm, 16... Fifth arm, 17... Sixth arm, 20... End effector, 21... Motor, 22... Power transmission mechanism, 23... First reduction gear, 31... Motor, 32... Power transmission mechanism, 33... Second reduction gear, 41... Motor, 42... Power transmission mechanism, 51... Motor, 52... Power transmission mechanism, 71... Base, 72... Robot arm, 73... First arm, 74... Second arm, 75... Working head, 76... End effector, 81... Control unit, 82... Memory unit, 83... Communication unit, 171... Joint part, 172... Joint part, 173... Joint part, 174... Joint part, 175... Joint part, 176... Joint part, 231... Frame, 233... Internal gear, 233A... Internal teeth, 234... Sun gear, 234A... Teeth, 235... Planet gear, 235A... Teeth, 236... Carrier, 237... Input shaft, 238... Output shaft, 751... Spline nut, 752... Ball screw nut, 753... Spline shaft, 811... Drive control unit, 812... Acquisition unit, 813... Detection unit, 814... Fault prediction unit, 815... Learning model, I0... Predetermined value, I0A... First threshold value, I0B... Second threshold value, J1... First rotation axis, J2... Second rotation axis, J3... Third rotation axis, O1... Axis, O2... Axis, S101... Step, S102... Step, S103... Step, S104... Step, S201... Step, S202... Step, S203... Step, S204... Step, S205... Step, S206... Step

Claims

1. A robot comprising: a base; and a robotic arm connected to the base via a joint portion having a motor and a planetary gear reduction mechanism, the robotic arm being connected to the base; and a detection device having: an acquisition unit that acquires a current value due to a back electromotive force generated by the motor; and a detection unit that detects a state of the robot based on the current value acquired by the acquisition unit.

2. The robot system according to claim 1, wherein the acquisition unit acquires the current value in each of the forward and reverse rotation directions of the motor.

3. The robot system according to claim 1 or 2, wherein the detection unit determines that an object has contacted the robotic arm when the current value acquired by the acquisition unit reaches a predetermined value.

4. The planetary gear reduction mechanism includes: a ring-shaped internal gear; a sun gear disposed inside the internal gear and concentric with the internal gear; a plurality of planetary gears meshing with both the internal gear and the sun gear; and a carrier that rotatably supports each of the planetary gears. The robot system according to claim 1, wherein the internal gear is more elastic than the planetary gear.

5. The robot system according to claim 1, wherein the detection device has a failure prediction unit that predicts a failure of the robot by performing machine learning based on the current value.

6. A state detection method for detecting a state of a robot comprising: a base; and a robotic arm connected to the base via a joint portion having a motor and a planetary gear reduction mechanism, the robotic arm being connected to the base, the method comprising: a first step of acquiring a current value due to a back electromotive force generated by the motor; and a second step of detecting a state of the robot based on the current value acquired in the first step.

7. A detection device for detecting a state of a robot comprising: a base; and a robotic arm connected to the base via a joint portion having a motor and a planetary gear reduction mechanism, the robotic arm being connected to the base, the detection device comprising: an acquisition unit that acquires a current value due to a back electromotive force generated by the motor; and a detection unit that detects a state of the robot based on the current value acquired by the acquisition unit.

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