Detection method, robot system, and program

Abstract

To provide a detection method, a robot system, and a program for detecting an overload state of a power transmission mechanism while simplifying a device configuration and reducing costs.SOLUTION: A detection method for detecting an overloaded state of a power transmission mechanism using a motor as a drive source includes: a first step of acquiring torque information which is time-varying information of output torque of the motor; a second step of detecting time T during which torque saturation occurs in the motor based on a predetermined torque saturation value and the torque information; a third step of obtaining a torque estimated value F1 of the output torque of the motor based on length of the detected time T; a fourth step of comparing a reference value F0 of the output torque corresponding to a maximum load allowable by the power transmission mechanism with the obtained torque estimated value F1; and a fifth step of giving notification of an overloaded state of the power transmission mechanism when a comparison result in the fourth step is F1≥F0.SELECTED DRAWING: Figure 4

Description

Technical Field

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

Background Art

[0002] For example, the robot described in Patent Document 1 has a robot arm including a plurality of arms and a joint portion that rotatably connects adjacent arms, and drives this robot arm to a desired posture to perform operations such as transporting, assembling, processing, and inspecting a workpiece. A joint mechanism is installed in each joint portion of this robot arm as a drive portion for rotationally driving the arm. The joint mechanism has a motor and a speed reducer that decelerates the rotational speed of the motor.

[0003] Also, in Patent Document 1, a friction drive mechanism is connected to the output shaft of the motor. The friction drive mechanism has a contact portion that contacts the output shaft of the motor, and the output torque of the motor can be adjusted by adjusting the contact load of the contact portion. Further, for example, when a torque in the direction opposite to the output torque of the motor is applied to the joint, the torque in the opposite direction can be released by reducing the contact load of the contact portion. Therefore, it is possible to prevent an excessive load from being applied to the joint. That is, an overload state can be detected and eliminated.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the configuration described in Patent Document 1, it is necessary to provide a friction drive mechanism to detect an overload state. As a result, the cost increases and the device configuration becomes complicated.

[0006] The detection method of the present invention is a detection method for detecting an overload state of a power transmission mechanism having a motor as a drive source, a first step of acquiring torque information which is information on the output torque of the motor over time; a second step of detecting a time T during which torque saturation has occurred in the motor based on a predetermined torque saturation value and the torque information; a third step of obtaining a torque estimated value F1 of the output torque of the motor based on the length of the detected time T; a fourth step of comparing a reference value F0 of the output torque corresponding to the maximum load that the power transmission mechanism can withstand with the obtained torque estimated value F1; and a fifth step of notifying an overload state of the power transmission mechanism when the comparison result in the fourth step is F1≧F0.

[0007] The robot system of the present invention includes a robot having a robot arm having a motor and a power transmission mechanism, and a control device that drives the motor to control the operation of the robot arm. The control device includes an acquisition unit that acquires torque information which is information on the output torque of the motor over time, a detection unit that detects a time T during which torque saturation has occurred in the motor based on a predetermined torque saturation value and the torque information, a calculation unit that obtains a torque estimated value F1 of the output torque of the motor based on the length of the detected time T, and a comparison unit that compares a reference value F0 of the output torque corresponding to the maximum load that the power transmission mechanism can withstand with the obtained torque estimated value F1. When the comparison result of the comparison unit is F1 ≧ F0, it includes a notification signal generation unit that generates a notification signal for notifying an overload state of the power transmission mechanism.

[0008] The program of the present invention is a program for detecting an overload state of a power transmission mechanism having a motor as a drive source, a first step of acquiring torque information which is information on the output torque of the motor over time; a second step of detecting a time T during which torque saturation has occurred in the motor based on a predetermined torque saturation value and the torque information; a third step of obtaining a torque estimated value F1 of the output torque of the motor based on the length of the detected time T; a fourth step of comparing a reference value F0 of the output torque corresponding to the maximum load that the power transmission mechanism can withstand with the obtained torque estimated value F1; When the comparison result in the fourth step is F1 ≧ F0, it is for executing a fifth step of notifying an overload state of the power transmission mechanism.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

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

[0011] <Embodiment> FIG. 1 is a schematic configuration diagram of a robot system according to an embodiment of the present invention. FIG. 2 is a block diagram of the robot system shown in FIG. 1. FIG. 3 is a graph showing an example of torque information. FIG. 4 is a flowchart for explaining an example of the 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, "vertical" means not only the case where it coincides with the vertical, but also the case where it is inclined slightly with respect to the vertical, for example, within ±10°. Also, in this specification, "parallel" means not only the case where two objects coincide with each other, but also the case where they are inclined slightly from parallel, for example, within ±10°.

[0014] The robot system 1 shown in FIG. 1 executes the detection method of the present invention and includes a robot 7 and a control device 3 that controls the driving of each part of the robot 7.

[0015] The robot 7 in this embodiment is a scalar robot and is used, for example, in various operations such as holding, transporting, assembling, processing, and inspecting workpieces such as electronic components. However, the use of the robot 7 is not particularly limited. Also, the robot 7 may be other than a scalar robot, for example, a 6-axis articulated robot, a dual-arm robot, or the like.

[0016] As shown in FIG. 1, the robot 7 includes a base 71 and a robot arm 72 rotatably connected to the base 71. The robot arm 72 has a first arm 73 whose base end portion 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 portion is connected to the tip end portion of the first arm 73 and rotates around a second rotation axis J2 along the vertical direction with respect to the first arm 73.

[0017] A work head 75 is provided at the tip of the second arm 74. The work head 75 includes 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 the central axis thereof 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.

[0018] 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.

[0019] The robot 7 has a first joint portion 4K that rotatably connects the base 71 and the first arm 73, and a motor unit 4 for rotating the first arm 73 about a first rotation axis J1 with respect to the base 71 is installed in the first joint portion 4K.

[0020] The robot 7 also has a second joint portion 6K that rotatably connects the first arm 73 and the second arm 74, and a motor unit 6 for rotating the second arm 74 about a second rotation axis J2 with respect to the first arm 73 is installed in the second joint portion 6K.

[0021] The robot 7 also has a first drive mechanism 791 that rotates the spline nut 751 to rotate the spline shaft 753 about the third rotation axis J3, and a second drive mechanism 792 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. The second drive mechanism 792 is installed below the first drive mechanism 791.

[0022] The first drive mechanism 791 has a motor 793, and the second drive mechanism 792 has a motor 794. When the motor 793 is driven, the spline nut 751 rotates in a predetermined direction, and the spline shaft 753 rotates around the third rotation axis J3. Also, when the motor 794 is driven, the ball screw nut 752 rotates in a predetermined direction, and the spline shaft 753 moves in the vertical direction.

[0023] As shown in FIG. 2, the motors 793 and 794 are electrically connected to the control device 3. The energization conditions such as the energization pattern, energization timing, and energization amount to the motors 793 and 794 are controlled by the control device 3.

[0024] The motor unit 4 has a motor 41 and a power transmission mechanism 42 having the motor 41 as a drive source. The motor 41 generates a driving force for rotating the first arm 73 with respect to the base 71. The motor unit 6 has a motor 61 and a power transmission mechanism 62 having the motor 61 as a drive source. The motor 61 generates a driving force for rotating the second arm 74 with respect to the first arm 73.

[0025] The motors 41 and 61 are not particularly limited, but for example, servo motors such as AC servo motors and DC servo motors are preferable. The same applies to the motors 793 and 794 described above, and they may be the same as the motors 41 and 61 or may be of different types and configurations.

[0026] Although not shown in the drawings, the motors 41 and 61 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. The energization pattern, energization timing, energization amount, etc. to each winding provided in the stator are controlled by the control device 3.

[0027] The power transmission mechanism 42 transmits the driving force of the motor 41, which is the power source, to the adjacent arm, and the power transmission mechanism 62 transmits the driving force of the motor 61, which is the power source, to the adjacent arm. The power transmission mechanism 42 includes a speed reducer 421 and a pulley and an endless belt (not shown). Similarly, the power transmission mechanism 62 also includes a speed reducer (not shown), a pulley, and an endless belt. Note that in the power transmission mechanisms 42 and 62, the pulley and the endless belt may be omitted.

[0028] As the speed reducer 421, for example, a speed reducer such as an eccentric swing type, a planetary gear type, or a harmonic gear type can be used. The same applies to the speed reducer in the power transmission mechanism 62.

[0029] Note that in the first joint portion 4K and the second joint portion 6K, various elements such as the types and models of the motors 41 and 61, the types and models of the speed reducers in the power transmission mechanisms 42 and 62, the weight, and the allowable transmission torque value may be different.

[0030] As shown in FIG. 2, the control device 3 includes a control unit 31, a storage unit 32, and a communication unit 33. These units are connected to be communicable with each other via, for example, a bus.

[0031] The control unit 31 is composed of, for example, at least one CPU (Central Processing Unit), reads out and executes various programs such as an operation program stored in the storage unit 32. The signal generated by the control unit 31 is transmitted to each part of the robot 7 via the communication unit 33, and the signal from each part of the robot 7 is received by the control unit 31 via the communication unit 33. Thereby, the robot arm 72 can execute a predetermined operation under predetermined conditions.

[0032] Also, the storage unit 32 stores a program of the present invention for executing the detection method of the present invention. By the control unit 31 reading out and executing the program of the present invention, the detection method of the present invention can be executed.

[0033] The storage unit 32 stores various programs and the like executed by the control unit 31. Examples of the storage unit 32 include those configured with 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.

[0034] Examples of the various programs stored in the storage unit 32 include a working operation program, a program for executing the detection method of the present invention, and the like.

[0035] The communication unit 33 transmits and receives signals between the control device 3 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.

[0036] Here, with the driving of the robot arm 72, various factors cause loads on the first joint portion 4K and the second joint portion 6K. In particular, when the output torque of the motor 41 becomes excessively large, an overload is applied to the power transmission mechanism 42 and it enters an overload state, and when the output torque of the motor 61 becomes excessively large, an overload is applied to the power transmission mechanism 62 and it enters an overload state.

[0037] Conventionally, it has been necessary to separately provide a friction drive mechanism to detect an overload state, which increases the cost and complicates the device configuration. In contrast, in the present invention, an overload state can be detected by simple control without separately providing a device such as a friction drive mechanism, and the device configuration can be simplified. This will be described below. Hereinafter, attention will be paid to the motor 41 and the power transmission mechanism 42, and the case of detecting an overload state of the speed reducer 421 of the power transmission mechanism 42 will be described.

[0038] As shown in FIG. 2, the control unit 31 includes, as functional units, an acquisition unit 311, a detection unit 312, a calculation unit, a comparison unit 314, and a notification signal generation unit 315.

[0039] The acquisition unit 311 executes a first step of acquiring torque information FA, which is information on the output torque of the motor 41 over time. The acquisition unit 311 obtains the torque information FA based on energization information such as the energization pattern, energization timing, and energization amount of the motor 41. Since there is a correlation between the energization information of the motor 41 and the output torque of the motor 41, the torque information FA can be obtained by calculating the output torque of the motor 41 over time from the energization information of the motor 41. The torque information FA is information on the output torque of the motor 41 over time, and can be represented, for example, as a graph with the horizontal axis representing time (ms) and the vertical axis representing the torque value (kgf) of the output torque, as shown in FIG. 3.

[0040] In the present embodiment, the acquisition unit 311 always acquires the torque information FA while the robot arm 72 is being driven. However, the present invention is not limited to this configuration, and for example, a configuration may be adopted in which a time period during which the output torque is likely to increase is extracted based on an operation program, and the torque information FA is acquired only during the extracted time period.

[0041] The detection unit 312 executes a second step of detecting the time T during which torque saturation has occurred in the motor 41, that is, the torque saturation time, based on a predetermined torque saturation value Fz and the torque information FA. That is, the detection unit 312 detects the cumulative value of the time T when the torque value in the torque information FA reaches the torque saturation value Fz. The torque saturation value Fz is a value determined for each type of motor, and in the case of the motor 41, it is the rated maximum value of the output torque of the motor 41. The torque saturation value Fz is stored in advance in the storage unit 32.

[0042] For example, in the torque information FA shown in FIG. 3, the output torque of the motor 41 (the torque value in the torque information FA) reaches the torque saturation value Fz between time t1 and time t2. In this case, the time T during which torque saturation has occurred is t2 - t1 (ms).

[0043] The calculation unit 313 executes a third step of obtaining a torque estimated value F1 of the output torque of the motor 41 based on the detected length of the time T. The torque estimated value F1 is a value indicating the load of the speed reducer 421 connected to the motor 41. In addition to the output torque from the motor 41, a load (torque applied to the input shaft or output shaft) due to the inertial force of the robot arm 72 or the like is applied to the speed reducer 421. That is, when the torque of the motor 41 is saturated, in addition to the torque saturation value Fz, a load due to the inertial force of the robot arm 72 or the like is applied. The torque estimated value F1 is a value obtained by summing these. Since there is a correlation between the torque estimated value F1 and the time T during which torque saturation occurs, the torque estimated value F1 can be obtained based on a function showing the relationship between the time T and the torque estimated value F1. Specifically, the torque estimated value F1 can be obtained by adding a value obtained by multiplying the torque saturation value Fz by the coefficient k of the time T.

[0044] The coefficient k is obtained by experimentally driving the robot arm 72 and measuring the time T during which torque saturation occurs and the torque input to the speed reducer 421, and is stored in the storage unit 32.

[0045] That is, the calculation unit 313 obtains the torque estimated value F1 by calculating F1 = Fz + T × k. As can be seen from this function, the torque estimated value F1 is increased as the cumulative value of the time T increases.

[0046] The comparison unit 314 executes a fourth step of comparing the reference value F0 of the output torque corresponding to the maximum load that the speed reducer 421 of the power transmission mechanism 42 can tolerate with the obtained torque estimated value F1. That is, it is determined whether F1 ≥ F0. The reference value F0 may be a value determined by a design value, or may be a value obtained by multiplying the value determined by the design value by a desired coefficient (safety factor), for example, 0.8. The reference value F0 is stored in the storage unit 32. The case where F1 ≥ F0 is defined as the overload state of the speed reducer 421.

[0047] When the comparison result of the comparison unit 314 is F1 ≧ F0, the notification signal generation unit 315 executes the fifth step of notifying the overload state of the speed reducer 421 of the power transmission mechanism 42. When the comparison result by the comparison unit 314 is F1 ≧ F0, the notification signal generation unit 315 generates a notification signal for notifying the overload state of the speed reducer 421 of the power transmission mechanism 42. There are, for example, the following three patterns in the notification signal generated by the notification signal generation unit 315. Note that two or more of the following patterns 1, 2, and 3 may be combined.

[0048] (Pattern 1) The robot system 1 has a voice generation unit (not shown), such as a speaker, for notifying by voice, and the notification signal generated by the notification signal generation unit 315 is a drive signal for driving the voice generation unit.

[0049] (Pattern 2) The robot system 1 has a display unit (not shown), such as a liquid crystal display, for notifying by visual recognition, and the notification signal generated by the notification signal generation unit 315 is a drive signal for driving the display unit.

[0050] (Pattern 3) It can be notified by reducing the speed of the robot arm 72. In this case, the notification signal generated by the notification signal generation unit 315 is a drive signal for driving the motors 41 and 61.

[0051] In the robot system 1 as described above, torque information FA, which is information on the output torque of the motor 41 over time, is acquired, the time T during which torque saturation occurs in the motor 41 is detected, and based on the length of the detected time T, a torque estimated value F1 of the output torque of the motor 41 is obtained. Then, the obtained torque estimated value F1 is compared with a reference value F0, and when F1 ≥ F0, in the power transmission mechanism 42, in this embodiment, it is set as an overload state of the speed reducer 421. According to such a configuration, while omitting the separate installation of a device for detecting torque such as a conventional friction drive mechanism, the overload state can be accurately detected. Therefore, while achieving cost reduction and simplification of the device, the overload state of the power transmission mechanism can be accurately detected. In particular, when introducing a system for detecting the overload state to an existing robot model, since it can be introduced only by changing the software without changing the device configuration, it is advantageous for introducing this system to an existing robot model.

[0052] As described above, the robot system 1 of the present invention includes a robot 7 including a robot arm 72 having a motor 41 and a power transmission mechanism 42, and a control device 3 that drives the motor 41 to control the operation of the robot arm 72. The control device 3 includes an acquisition unit 311 that acquires torque information FA, which is information on the output torque of the motor 41 over time, a detection unit 312 that detects the time T during which torque saturation occurs in the motor 41 based on a predetermined torque saturation value Fz and the torque information FA, a calculation unit 313 that obtains a torque estimated value F1 of the output torque of the motor 41 based on the length of the detected time T, a comparison unit 314 that compares a reference value F0 of the output torque corresponding to the maximum load that the power transmission mechanism 42 can tolerate with the obtained torque estimated value F1, and a notification signal generation unit 315 that generates a notification signal for notifying the overload state of the power transmission mechanism 42 when the comparison result of the comparison unit 314 is F1 ≥ F0. Thereby, while omitting the separate installation of a device for detecting torque such as a conventional friction drive mechanism, the overload state of the power transmission mechanism 42 can be accurately detected. Therefore, while achieving cost reduction and simplification of the device, the overload state of the power transmission mechanism 42 can be accurately detected.

[0053] In the present embodiment, the case of detecting the overload state of the speed reducer 421 of the power transmission mechanism 42 has been described. However, the present invention is not limited to this, and a configuration for detecting the overload state of a part other than the speed reducer 421 included in the power transmission mechanism 42, for example, an endless belt or a pulley, may be used.

[0054] Further, the present invention may be configured to detect the overload state of the speed reducer of the power transmission mechanism 62, or may be configured to detect the overload state of a part other than the speed reducer included in the power transmission mechanism 62, for example, an endless belt or a pulley.

[0055] Further, the present invention may be configured to detect the overload state of the first drive mechanism 791, which is a power transmission mechanism having the motor 793 as a drive source, or may be configured to detect the overload state of the second drive mechanism 792, which is a power transmission mechanism having the motor 794 as a drive source.

[0056] Furthermore, the present invention may be configured to detect two or more of the above overload states simultaneously or in any order. Thereby, the overload state of each power transmission mechanism included in the robot arm 72 can be detected, which is more preferable for optimizing the driving of the entire robot arm 72. In any of the above cases, according to the object for which the overload state is detected, the coefficient k and the reference value F0 are stored in the storage unit 32, respectively.

[0057] Next, an example of the detection method of the present invention will be described with reference to the flowchart shown in FIG. 4.

[0058] Hereinafter, the operation program stored in the storage unit 32 will be read out and described starting from the point where the robot arm 72 is being driven.

[0059] First, in step S101, torque information FA is acquired. That is, the acquisition unit 311 obtains the torque information FA based on energization information such as the energization pattern, energization timing, and energization amount to the motor 41. Such step S101 is the first step. The torque information FA is information on the output torque of the motor 41 over time, and for example, as shown in FIG. 3, it can be represented by a graph with the horizontal axis being time (ms) and the vertical axis being the torque value (kgf) of the output torque.

[0060] Next, in step S102, the time T during which torque saturation occurs is detected. That is, the detection unit 312 detects the cumulative value of the time T when the torque value in the torque information FA reaches the torque saturation value Fz.

[0061] For example, in the torque information FA shown in FIG. 3, the output torque reaches the torque saturation value Fz between time t1 and time t2. In this case, the time T during which torque saturation occurs is t2 - t1 (ms). Such step S102 is the second step.

[0062] Next, in step S103, a torque estimated value F1 is obtained. That is, the calculation unit 313 obtains the torque estimated value F1 of the output torque of the motor 41 based on the detected length of time T. Specifically, the calculation unit 313 obtains the torque estimated value F1 by calculating F1 = Fz + T × k. Such step S103 is the third step.

[0063] Next, in step S104, it is determined whether F1 ≥ F0. That is, the comparison unit 314 compares the reference value F0 of the output torque corresponding to the maximum load that the speed reducer 421 of the power transmission mechanism 42 can tolerate with the obtained torque estimated value F1. Such step S104 is the fourth step.

[0064] In step S104, if it is determined that F1 ≥ F0 (YES), the process proceeds to step S105. On the other hand, in step S104, if it is determined that F1 < F0 (NO), the process proceeds to step S106.

[0065] In step S105, the notification signal generation unit 315 generates a notification signal and performs notification based on this notification signal. That is, the notification signal generation unit 315 generates and outputs a notification signal for notifying the overload state of the speed reducer 421 of the power transmission mechanism 42, and performs notification based on the notification signal. Examples of the type of the notification signal and the method of notification include the aforementioned patterns 1, 2, 3, and combinations thereof. Such step S105 is the fifth step.

[0066] Next, in step S106, the control unit 31 determines whether the execution of the operation program has been completed. In step S106, if it is determined that the execution of the operation program has been completed, the process ends. If it is determined that the execution of the operation program has not been completed, the process returns to step S101 and the subsequent steps are repeated.

[0067] As described above, the detection method of the present invention is a detection method for detecting the overload state of the power transmission mechanism 42 having the motor 41 as a drive source, including a first step of acquiring torque information FA which is information on the output torque of the motor 41 over time, a second step of detecting the time T during which torque saturation occurs in the motor 41 based on a predetermined torque saturation value Fz and the torque information FA, a third step of obtaining a torque estimated value F1 of the output torque of the motor 41 based on the length of the detected time T, a fourth step of comparing a reference value F0 of the output torque corresponding to the maximum load that the power transmission mechanism 42 can tolerate with the obtained torque estimated value F1, and a fifth step of notifying the overload state of the power transmission mechanism 42 when the comparison result in the fourth step is F1≧F0. Thereby, while omitting the separate installation of a device for detecting torque such as a conventional friction drive mechanism, the overload state of the power transmission mechanism 42 can be accurately detected. Therefore, the overload state of the power transmission mechanism 42 can be accurately detected while reducing the cost and simplifying the device.

[0068] In the present embodiment, the detection method and program of the present invention have been described when applied to the robot system 1. However, the present invention is not limited to this, and it is applicable to any device equipped with a motor and a power transmission mechanism.

[0069] Also, in the third step, as the cumulative value of time T increases, the torque estimated value F1 is increased. Thereby, the torque estimated value F1 can be obtained more accurately.

[0070] Also, in the third step, the torque estimated value F1 is obtained based on a function showing the relationship between time T and the torque estimated value F1. Thereby, the torque estimated value F1 can be obtained more accurately.

[0071] Also, in the third step, calculations are performed based on the following formula (1). F1 = Fz + T × k…(1) (where k is a coefficient and Fz is the rated maximum value of the output torque of the motor) Thereby, the torque estimated value F1 can be obtained more accurately.

[0072] Also, it is preferable to target each of the plurality of motors 41 and 61, set a reference value F0 for each of the motors 41 and 61, and execute the first step, the second step, the third step, and the fourth step. Thereby, the overload state of each of the power transmission mechanisms 42 and 62 can be detected.

[0073] Further, the program of the present invention is a program for detecting an overload state of a power transmission mechanism 42 having a motor 41 as a drive source, and includes a first step of acquiring torque information FA which is information on the output torque of the motor 41 over time, a second step of detecting a time T during which torque saturation has occurred in the motor 41 based on a predetermined torque saturation value Fz and the torque information FA, a third step of obtaining a torque estimated value F1 of the output torque of the motor 41 based on the length of the detected time T, a fourth step of comparing a reference value F0 of the output torque corresponding to the maximum load that the power transmission mechanism 42 can tolerate with the obtained torque estimated value F1, and a fifth step of notifying an overload state of the power transmission mechanism 42 when the comparison result in the fourth step is F1≧F0. By executing such a program, it is possible to accurately detect the overload state of the power transmission mechanism 42 while omitting the separate installation of a device for detecting torque such as a conventional friction drive mechanism. Therefore, it is possible to accurately detect the overload state of the power transmission mechanism 42 while reducing the cost and simplifying the device.

[0074] Note that, in the present embodiment, the program of the present invention is stored in the storage unit 32, but the present invention is not limited to this, and it may be stored in other storage devices, storage media, clouds, etc.

[0075] As described above, the detection method, robot system, and program of the present invention have been described based on the illustrated embodiments. However, the present invention is not limited to this, and the configurations and processes of each part in the detection method, robot system, and program can be replaced with any configurations and processes having the same functions. Further, other arbitrary components and processes may be added to the detection method, robot system, and program.

Explanation of Reference Numerals

[0076] 1... Robot system, 3... Control device, 4... Motor unit, 4K... First joint part, 6... Motor unit, 6K... Second joint part, 7... Robot, 31... Control unit, 32... Memory unit, 33... Communication unit, 41... Motor, 42... Power transmission mechanism, 61... Motor, 62... Power transmission mechanism, 71... Base, 72... Robot arm, 73... First arm, 74... Second arm, 75... Working head, 76... End effector, 311... Acquisition unit, 312... Detection unit, 313... Calculation unit, 314... Comparison unit, 315... Notification signal generation unit, 421... Reducer, 751... Spline nut, 752... Ball screw nut, 753... Spline shaft, 791... First drive mechanism, 792... Second drive mechanism, 793... Motor, 794... Motor, F0... Reference value, F1... Torque estimated value, FA... Torque information, Fz... Torque saturation value, T... Time, t1... Time, t2... Time, J1... First rotation axis, J2... Second rotation axis, J3... Third rotation axis, S101... Step, S102... Step, S103... Step, S104... Step, S105... Step, S106... Step

Claims

1. A detection method for detecting an overload state of a power transmission mechanism having a motor as a driving source, comprising: a first step of obtaining torque information which is information on the output torque of the motor over time; a second step of detecting a time T during which torque saturation has occurred in the motor based on a predetermined torque saturation value and the torque information; a third step of obtaining a torque estimated value F1 of the output torque of the motor based on the length of the detected time T; a fourth step of comparing a reference value F0 of the output torque corresponding to the maximum load that the power transmission mechanism can withstand with the obtained torque estimated value F1; a fifth step of notifying an overload state of the power transmission mechanism when the comparison result in the fourth step is F1≧F0.

2. The detection method according to claim 1, wherein in the third step, the torque estimated value F1 is increased as the cumulative value of the time T increases.

3. The detection method according to claim 1 or 2, wherein in the third step, the torque estimated value F1 is obtained based on a function showing the relationship between the time T and the torque estimated value F1.

4. The detection method according to claim 3, wherein in the third step, calculations are performed based on the following formula (1). F1 = Fz + T × k... (1) (where k is a coefficient and Fz is the rated maximum value of the output torque of the motor)

5. The detection method according to claim 1, which is applied to each of a plurality of the motors, the reference value F0 is set for each motor, and the first step, the second step, the third step, and the fourth step are executed.

6. A robot comprising a robot arm having a motor and a power transmission mechanism, and a control device for driving the motor to control the operation of the robot arm, wherein the control device includes an acquisition unit for acquiring torque information which is information on the output torque of the motor over time, a detection unit for detecting a time T during which torque saturation has occurred in the motor based on a predetermined torque saturation value and the torque information, a calculation unit for obtaining a torque estimated value F1 of the output torque of the motor based on the length of the detected time T, and a comparison unit for comparing a reference value F0 of the output torque corresponding to the maximum load that the power transmission mechanism can withstand with the obtained torque estimated value F1. A robot system, comprising: a notification signal generation unit that generates a notification signal for notifying an overload state of the power transmission mechanism when a comparison result of the comparison unit is F1 ≥ F0. **Claim 7** A program for detecting an overload state of a power transmission mechanism having a motor as a drive source, a first step of obtaining torque information which is information on the output torque of the motor over time; a second step of detecting a time T during which torque saturation has occurred in the motor based on a predetermined torque saturation value and the torque information; a third step of obtaining a torque estimated value F1 of the output torque of the motor based on the length of the detected time T; a fourth step of comparing a reference value F0 of the output torque corresponding to the maximum load that the power transmission mechanism can withstand with the obtained torque estimated value F1; a program for executing a fifth step of notifying an overload state of the power transmission mechanism when a comparison result in the fourth step is F1 ≥ F0.

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