JP7358049B2 - Control methods, programs, recording media, robot systems, and article manufacturing methods - Google Patents

Description

The present invention relates to a robot diagnostic method, a robot diagnostic device, a control program, a recording medium, a production system, and an article manufacturing method for diagnosing a failure in a drive system that drives joints of a robot device.

Conventionally, various robot devices have been used at production sites for industrial products, and in recent years, robot devices equipped with multi-axis, multi-joint robot arms that can perform more complex operations have become widespread.

The configurations of the robot arm of this type of industrial robot device can be categorized according to the structure of links and joints, such as a vertical multi-joint configuration and a horizontal multi-joint configuration. However, in both arm configurations, the structure of the joint drive system is similar, and the driving force of the motor that is the rotational drive source is transferred to the driven side link by a transmission system such as a pulley, belt, reducer (gear), etc. A configuration is used that transmits the following information.

For example, as the operating time of the motor driving force transmission system that constitutes such a robot arm increases, the probability of failure or performance deterioration increases. Such failures and performance deterioration include an increase in the amount of backlash due to wear of the teeth of the reducer, and backlash due to loosening of the screws that secure the pulley and motor shaft. Due to such failures and performance deterioration, the angle transmission accuracy of each joint decreases, resulting in a decrease in the motion accuracy of the robot arm. Therefore, in recent years, various techniques regarding failure diagnosis of robot arms have been proposed.

For example, in Patent Document 1 listed below, it is considered to detect a section where the motor torque value detected by the torque detection means is almost zero as a section where backlash occurs between drive gears. In Patent Document 1, failure is determined by comparing the backlash amount obtained from the motor rotation amount during the same section with a threshold value. In addition, in Patent Document 2 below, in order to detect play in the joint between the motor shaft and the pulley, the motor rotational position is detected at a specific control cycle, and the amount of movement per unit time for each control cycle is integrated over a certain period of time. A method has been considered that compares the value obtained using the above method with a threshold value.

Japanese Patent Application Publication No. 9-201745 Japanese Patent Application Publication No. 2009-142956

However, in Patent Document 1, the target of failure diagnosis is limited to only the reduction gear. Further, in Patent Document 2, the target of failure diagnosis is limited to only the fastening portion of the pulley. That is, the target of failure diagnosis in these conventional techniques is limited to a specific location. Therefore, when trying to use a device with a limited number of diagnostic targets as in Patent Documents 1 and 2, if the configuration of the drive system of each part of the robot arm is different, it is necessary to arrange a different diagnostic device for each drive system configuration. There is a possibility that the entire robot device becomes complicated.

An object of the present invention is to make it possible to universally detect failures or performance deterioration in components of a drive system for joints of a robot device, and to specify components related to failures or performance deterioration.

One aspect of the present invention is a method for controlling a robot system including a robot, at least two devices that transmit a first torque from a motor that drives joints of the robot and output it as a second torque, and a control device. A first torque acquisition step in which the control device acquires the first torque when the rotation direction of the motor is reversed; and a first torque acquisition step in which the control device acquires the second torque when the rotation direction of the motor is reversed. a second torque acquisition step of acquiring a second torque of the at least two devices based on the first torque, the second torque, and data for identifying a failure state of each of the devices; This control method is characterized in that it includes the step of identifying a device that is in a failure state.

According to the above configuration, when the rotation direction of the motor is reversed, the drive torque, the output torque, and the profile data that can identify the failure part of the drive system are compared, and the drive system of the joint of the robot device is configured. It is possible to universally detect failures or performance deterioration in parts.

FIG. 1 is an explanatory diagram schematically showing a robot system capable of implementing the present invention. FIG. 2 is an explanatory diagram showing the configuration of joints of the robot arm in FIG. 1. FIG. 3 is an explanatory diagram showing a motor shaft side pulley in FIG. 2. FIG. FIG. 1 is a block diagram showing the configuration of a control system of a robot diagnostic device according to an embodiment of the present invention. 1 is a block diagram showing the functional configuration of a control device in Embodiment 1 of the present invention. FIG. FIG. 3 is a waveform chart showing drive torque and output torque in a state where no failure or performance deterioration occurs. FIG. 3 is an explanatory diagram showing profile data used for failure determination. (a) shows the configuration around the motor shaft pulley in its proper state, as well as the drive torque and output torque, and (b) shows the surroundings of the same pulley in a faulty state where the set screw of the motor shaft pulley has loosened. FIG. 3 is an explanatory diagram showing the configuration, driving torque, and output torque. FIG. 2 is a flowchart showing a main part of drive control of a robot joint according to an embodiment of the present invention. FIG. 3 is a flowchart showing the flow of a failure diagnosis program in Embodiment 1 of the present invention. It is a block diagram showing the functional composition of a control device in Embodiment 2 of the present invention. FIG. 7 is a flowchart showing the flow of a failure diagnosis program in Embodiment 2 of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. Note that the configuration shown below is just an example, and for example, the detailed configuration can be changed as appropriate by those skilled in the art without departing from the spirit of the present invention. Moreover, the numerical values taken up in this embodiment are reference numerical values, and do not limit the present invention.

In the above, we have referred to problems that occur in the drive system of the joints of robot devices using expressions such as "failure or performance deterioration" that refer to a range of failures that have a certain range. In the following, since it is cumbersome to describe each of the terms "failure or performance deterioration," failures within the scope of the above-mentioned "failure or performance deterioration" will be expressed simply by the word "failure." In the following, when we say "failure," we mean an event equivalent to the above-mentioned "failure or performance decline." In the following, when we say "failure", we mean a range of failures that have a certain range, including, for example, damage or wear and tear of the members of the mechanism to a decrease in the control accuracy of the mechanism.

<Embodiment 1>
Embodiment 1 of the present invention will be described below with reference to FIGS. 1 to 10. FIG. 1 shows a schematic configuration of a robot system 500 that can perform robot diagnosis according to the present invention. As shown in FIG. 1, the robot system 500 includes a robot device 100 that performs operations related to assembly and processing on a workpiece W in order to manufacture articles such as industrial products or their parts. The robot system 500 also includes a robot control device 200 that controls the robot device 100 and a teaching pendant 300 connected to the robot control device 200. The robot system 500 can be placed in a production line (production system) for manufacturing articles such as industrial products or their parts so as to perform a specific work process.

The robot device 100 includes, for example, a six-axis multi-joint robot arm 101 and a hand (end effector) 102 connected to the tip of the robot arm 101. Although the robot arm 101 has a vertical multi-joint configuration, the present invention can be implemented in the same manner even if the robot arm 101 has other link connection configurations such as a parallel link configuration.

The robot arm 101 includes a base portion 101a fixed to a workbench, a plurality of links 121 to 126 that transmit displacement and force, and a plurality of joints 111 to 116 that connect the links 121 to 126 so as to be pivotable or rotatable. , is equipped with. Note that in this embodiment, since the plurality of joints 111 to 116 have almost the same configuration, the description of the joint 112 that connects the link 121 and the link 122 will be replaced with the description of the other joints 111 and 113 to 116. shall be taken as a thing. Furthermore, a joint having the same configuration as joint 112 may be provided at at least one of the plurality of joints 111 to 116 of robot arm 101.

As shown in FIG. 2, the joint 112 includes a servo motor (motor) 1 attached to a link 121, an encoder 11 that detects the rotation angle of the servo motor 1, and a reducer 12 that decelerates the output of the servo motor 1. It is equipped with. Further, the joint 112 includes a torque sensor 15 for detecting torque on the output side of the reducer 12. Note that a brake unit or the like may be provided between the servo motor 1 and the encoder 11, if necessary, to maintain the posture of the robot arm 101 when the power is turned off.

A motor shaft pulley 3 is attached to a motor shaft 2 that is the output shaft of the servo motor 1. Further, a reducer side pulley 6 is attached to the reducer input shaft 7, and the servo motor 1 driving force is transmitted to the speed reducer 12. Bearings 8, 9, and 10 are arranged on the link 121, and the motor shaft 2, reducer input shaft 7, and link 122 supported through these bearings can rotate smoothly.

A torque sensor 15 is attached to the output side of the drive system (transmission system), for example, the output side of the reduction gear 12. The torque sensor 15 connects the reducer 12 and the link 122, transmits the driving torque between them, and detects the magnitude thereof. The torque acquired from the torque sensor 15 is sometimes referred to as "output torque" hereinafter, with the intention of referring to the torque on the output side of the drive system of the joint. In addition, in the control shown below, it is necessary to obtain the drive torque generated by the input side of the drive system (transmission system), especially the servo motor 1. Below, an example will be shown in which the drive torque is calculated based on the drive current. . However, it is also possible to obtain the drive torque generated by the servo motor 1 by placing a sensor similar to the torque sensor 15 on the input side of the drive system (transmission system), for example, on the input side of the motor shaft side pulley 3. It will be done.

FIG. 3 shows a main part of the motor shaft side pulley 3 in an enlarged manner. As shown in the figure, in this configuration, a part of the motor shaft 2 is cut out linearly, and the motor shaft 2 and the motor shaft side pulley 3 are fixed with a set screw 4 so that they can rotate together. The belt 5 is, for example, a so-called cogged belt, and teeth as shown in the figure are formed on its surface, and by meshing with teeth (not shown) formed on the motor shaft side pulley 3, the rotation of the motor shaft side pulley 3 is controlled by the belt. 5. Naturally, the reducer side pulley 6 is also configured in the same manner as described above.

The speed reducer 12 is a spur gear and includes a driving gear 13 that is an input section and a driven gear 14 that is an output section. The drive gear 13 is connected to the reducer input shaft 7 , and the driven gear 14 is connected to a torque sensor 15 . The driven gear 14 has a larger diameter and a larger number of teeth than the drive gear 13.

Generally, the ratio of the number of teeth of a driven gear to the number of teeth of a drive gear (=number of teeth of driven gear/number of teeth of drive gear) can be treated as a reduction ratio. For example, when the reduction ratio is N, the rotation speed of the driven gear is reduced to 1/N of the rotation speed of the drive gear. That is, the rotation of the servo motor 1 is input to the reducer 12 via the motor shaft 2, the motor shaft pulley 3, the belt 5, the reducer pulley 6, and the reducer input shaft 7, and the drive system (transmission system). This configuration of the transmission system controls the speed at which the links 121 and 122 rotate relative to each other, or the torque generated by their joints.

For example, a strain gauge type torque sensor can be used as the torque sensor 15 (the same applies to a torque sensor disposed on the input side of the drive system). In the strain gauge method, when torque is applied to the torque sensor 15, the amount of strain in the elastic body is measured with a strain gauge attached to the elastic body, and the torque can be obtained as a detected amount corresponding to the measured amount of strain.

In this embodiment, the joints 111 to 116 and links 121 to 126 of the robot arm 101 have the configuration described using the joint 111 as an example. However, below, control related to the joint 111 and the link 121 will be explained, and it is not necessarily essential that the completely similar configurations be arranged for the other joints and links. Furthermore, in the above one-joint drive system, the motor shaft 2, motor shaft side pulley 3, belt 5, reducer side pulley 6, reducer input shaft 7, and reducer 12 will be referred to as a transmission system 16 below. There is.

FIG. 4 shows the structure of a control system of a robot control device 200 that performs failure diagnosis (robot diagnosis) of the robot device 100 in this embodiment. In this embodiment, it is assumed that the control device that performs failure diagnosis is the robot control device 200 that controls the position and orientation of the robot device 100 or its control circuit, particularly the CPU 201, but the arrangement of the control device that performs failure diagnosis The implementation form does not limit the present invention. For example, a control device that performs failure diagnosis, which will be described later, may be a device such as a robot system control device that controls a robot system in which the robot device 100 is arranged. As such a robot system control device, for example, an integrated control device called a PLC or a sequencer that integrally controls production equipment arranged on a production line can be considered. Further, for example, a control device that performs failure diagnosis, which will be described later, may be configured by an external terminal externally attached to the robot device 100, a PC, a server computer, or the like. Alternatively, a control device that performs failure diagnosis, which will be described later, may be built into the robot device 100. Note that when a failure diagnosis, which will be described later, is performed using a control device different from the robot control device 200, control information related to the drive torque of the servo motor 1, the output torque of the drive system, etc., is transmitted to the failure diagnosis via an appropriate communication means. shall be transmitted to the control device that performs the diagnosis. Any network or control signal line may be used as the communication means for transmitting this control information.

As shown in FIG. 4, the robot control device 200 includes a CPU (computation unit) 201, a ROM 202, a RAM 203, an HDD (storage unit) 204, a recording disk drive 205, and various interfaces 211 to 216. We are prepared.

A ROM 202, a RAM 203, an HDD 204, a recording disk drive 205, and various interfaces 211 to 216 are connected to the CPU 201 via a bus 217. The ROM 202 stores basic programs such as BIOS. The RAM 203 is a storage device that temporarily stores arithmetic processing results of the CPU 201.

The HDD 204 constitutes a storage unit that stores various data etc. that are the results of calculation processing by the CPU 201, and stores, for example, programs for causing the CPU 201 to execute various calculation processing (for example, a failure location determination program 331 to be described later). do. The CPU 201 executes various calculation processes based on programs recorded (stored) in the HDD 204 . The recording disk drive 205 can read various data, control programs, etc. recorded on the recording disk 206. Note that the recording disk 206 is composed of a removable recording medium such as various optical disks, for example. If a control program to be described later is stored on the recording disk 206, the recording disk 206 constitutes a computer-readable recording medium of the present invention.

A teaching pendant 300 that can be operated by a user is connected to the interface 211 . The teaching pendant 300 outputs the input target joint angles of the joints 111 to 116 to the CPU 201 via the interface 211 and the bus 217. Further, the encoder 11 is connected to the interface 212 and outputs a pulse signal to the CPU 201 via the interface 212 and the bus 217. Similarly, the torque sensor 15 is connected to the interface 213 and outputs a voltage signal to the CPU 201 via the interface 213 and the bus 217. Further, connected to the interfaces 214 and 215 are a monitor 311 on which various images and text information are displayed, and an external storage device 312 such as a rewritable nonvolatile memory or an external HDD. As will be described later, the monitor 311 can be used, for example, to output information that can identify the presence or absence of a failure in a joint of the robot device 100 or the failure location (failure location).

Further, a servo control device 313 is connected to the interface 216. The CPU 201 outputs drive command data indicating the control amount of the rotation angle of the motor shaft 2 of the servo motor 1 to the servo control device 313 via the bus 217 and the interface 216 at predetermined time intervals, for example. The servo control device 313 calculates the amount of current output to the servo motor 1 based on the drive command input from the CPU 201, supplies the current to the servo motor 1, and controls the joints 111 to 116 of the robot arm 101. Perform angle control. That is, the CPU 201 controls the driving of the joints 111 to 116 by the servo motor 1 via the servo control device 313 so that the angles of the joints 111 to 116 become the target joint angles.

Here, the functional configuration performed by the CPU 201 and the HDD 204 when executing a failure diagnosis program, for example, a failure location determination program 331 and a torque acquisition program 330, which will be described later, will be described with reference to FIG. FIG. 5 shows a functional block configuration of a control system of a robot system 500 according to the first embodiment.

As shown in FIG. 5, the following functional blocks are configured by the CPU 201 executing a failure location determination program 331, which will be described later. These include, for example, a joint reversal motion determination unit 401, a motor current acquisition unit 402, a drive torque calculation unit 403, an output torque acquisition unit 404, a backlash time calculation unit 405, a torque difference calculation unit 406, and a failure This is a location determination unit 407. Further, the RAM 203 includes a torque storage section 408, and the HDD 204 (or ROM 202) includes a profile storage section 409.

The motor current acquisition unit 402 A/D converts the three-phase current values flowing through the servo motor 1 at each specific control cycle (for example, every 100 μsec cycle), and obtains the three-phase current values from the A/D converted values. demand. The current value is calculated from the A/D converted value using a conversion formula determined from the current detection sensitivity coefficient of the current detection IC. Note that here, the A/D conversion value or the current value may be passed through a low-pass filter to remove noise.

The drive torque calculation unit 403 vector-converts the three-phase current acquired by the motor current acquisition unit 402 to obtain the q-axis current iq, and further multiplies the torque constant _Kt by the reduction ratio N to obtain the drive torque τ _i (=N× K _t ×i _q ) is calculated. The calculated driving torque τ _i is stored in the torque storage unit 408. Here, the q-axis current i _q is a component that contributes to torque in the three-phase current, and can be determined by the following equations (1) and (2). Further, i _u , i _v , and i _w represent three-phase currents, and θ represents the electrical angle of the servo motor 1.

The output torque acquisition unit 404 performs A/D conversion on the output signal of the torque sensor 15, and obtains the output torque τ _o from the A/D conversion value. The output torque τ _o is stored in the torque storage section 408 . Conversion from the A/D converted value to the output torque τ _o is performed using a torque conversion formula. This torque conversion formula is obtained by sampling the A/D conversion value when a specific torque is applied to the torque sensor 15 alone, and from the relationship between the applied torque and the A/D conversion value.

The torque storage unit 408 is an area that separately stores time series data of the driving torque τ _i and the output torque τ _o , and has a ring buffer structure. The drive torque τ _i and the output torque τ _o begin to be saved from the start of the robot arm 101, and after a certain period of time (for example, 10 seconds) has passed, the oldest data is replaced with the latest data. With such ring buffer control, it is possible to always store the latest data that goes back a certain amount of time from the current point in time.

When called by the servo control device 313, the joint reversal motion determination unit 401 counts pulse signals received from the encoder 11 to determine the rotation angle. The failure location determination program 331 is read out at a timing when a predetermined period of time (for example, 4 seconds) has elapsed from the timing at which the rotation direction (sign of the rotation angle) is reversed.

Normally, the operation of the robot arm 101 consists of a plurality of process operations. In the present embodiment, it is assumed that the user can set in the servo control device 313 in advance, for example, failure diagnosis timing definition information that defines whether failure diagnosis is to be performed in a process operation. Alternatively, it is also possible to automatically create definition information for failure diagnosis timing, as will be described later.

Next, the failure location determination program 331 in this embodiment will be explained. The failure location determination program 331 of this embodiment is configured to be able to detect that a joint drive system has failed and a failure location has occurred, and also to be able to specify the failure location.

The backlash time calculation unit 405 refers to the time series data of the output torque τ _o stored in the torque storage unit 408. The output torque τ _o has a waveform as shown in FIG. 6, for example. Note that the driving torque τ _i and the output torque τ _o stored in the torque storage unit 408 may be, for example, digitized numerical data, but analog waveforms are shown in FIG. 6 for ease of understanding. ing.

In FIG. 6, the solid line corresponds to the output torque τ _o and the dashed line corresponds to the drive torque τ _i . At this time, the time during which the output torque τ _o is approximately zero is defined as a backlash time T _bl . This backlash time _Tbl is the time during which backlash occurs between the driving gear 13 and the driven gear 14.

The torque difference calculation unit 406 calculates the drive torque τ _i calculated by the drive torque calculation unit 403 and stored in the torque storage unit 408 and the output torque τ _o acquired from the torque sensor 15 and stored in the torque storage unit 408. Reference time series data. For example, data as shown in FIG. 6 is stored as the drive torque τ _i and the output torque τ _o . In FIG. 6, the difference between the minimum value of the drive torque τ _i and the minimum value of the output torque τ _o at the backlash time T _bl is the torque difference τ _io .

The failure location determination unit 407 uses the backlash time _Tbl calculated by the backlash time calculation unit 405, the torque difference _τio calculated by the torque difference calculation unit 406, and the failure location determination profile stored in the profile storage unit 409. 332 (FIG. 7). This allows fault diagnosis to be performed.

FIG. 7 shows an example of the logical structure of the failure location determination profile 332, with backlash time plotted on the horizontal axis and torque difference plotted on the vertical axis. The failure location determination profile 332 in FIG. 7 is profile data indicating which of the motor shaft side pulley 3, belt 5, reduction gear side pulley 6, and reduction gear 12 of the transmission system 16 of the robot arm 101 is in failure. Profile data including such a failure profile is created in a storage area such as the ROM 202 in the form of a table memory that stores numerical values in multiple dimensions, for example.

For example, by comparing the torque difference τ _io calculated by the torque difference calculation unit 406 with the failure location determination profile 332, the following failure diagnosis becomes possible. For example, when the torque difference τ _io calculated by the torque difference calculation unit 406 is 0≦τ _io <τ _a , it is indicated that the motor shaft side pulley 3 is malfunctioning. Further, when τ _a ≦τ _io <τ _b, it is indicated that the belt 5 is in failure. Further, when τ _b ≦τ _io <τ _c, it is indicated that the reducer side pulley 6 is at fault. Furthermore, when τ _c ≦τ _io and the backlash time T _bl calculated by the backlash time calculation unit 405 is T _bl ≧T _a , it is indicated that the reducer 12 is malfunctioning.

FIG. 8A shows the state around the motor shaft pulley 3 during normal operation, and the drive torque τ _i and output torque τ _o at that time. FIG. 8(b) shows the state at the time of failure and the drive torque τ _i and output torque τ _o at that time.

As shown in FIG. 8(a), under normal conditions, the set screw 4 is in a sufficiently tightened state. In this state, the motor shaft 2 is fixed with a set screw 4 so as not to rotate relative to the motor shaft pulley 3, and the motor shaft 2 and the motor shaft pulley 3 move together, and the servo motor 1 transmits power. At this time, the drive torque τ _i and the output torque τ _o are, for example, as shown in the graph at the bottom of FIG. 8(a).

On the other hand, as shown in FIG. 8(b), in the event of a failure, the tightening of the set screw 4 is loosened, and a play (gap) is generated between the motor shaft 2 and the motor shaft side pulley 3. When the servo motor 1 is driven, the motor shaft 2 moves relative to the motor shaft pulley 3 until the backlash (gap) is eliminated. At this time, the drive torque τ _i and the output torque τ _o become as shown in the lower graph of FIG. 8(b). That is, while the motor shaft 2 is moving relative to the motor shaft pulley 3, the load torque applied to the servo motor 1 becomes smaller, and the driving torque τ _i becomes smaller. As a result, the torque difference τ _io becomes 0≦τ _io <τ _a , and by referring to the failure location determination profile 332, it can be determined that the motor shaft side pulley 3 has failed.

In this embodiment, as described above, failure is determined by comparing the value of the torque difference between the actual drive torque τ _i and the output torque τ _o with the value of the torque difference stored in the failure location determination profile 332. It is carried out. However, it is also possible to store profile data in other formats in the failure location determination profile 332.

For example, as shown in FIG. 8, when a transmission device fails, a waveform having a unique shape may occur in the change in the difference between the actual drive torque τ _i and the output torque τ _o . Therefore, it is conceivable to store, in the failure location determination profile 332, profile data that can identify a failure in a transmission device included in the drive system, and that represents, for example, a waveform of a change in torque difference. As a result, by comparing the waveform of the change in the difference between the actual drive torque τ _i and the output torque τ _o with the profile data stored in the failure location determination profile 332, a failure in a specific transmission device of the drive system can be detected. can be detected. The data format to be stored as profile data is arbitrary as long as it can identify the unique change characteristics of the torque difference, such as the quadratic differential of the torque difference that expresses the waveform of the change in the torque difference, or the timing (time) of an inflection point. The format may be used.

When it is determined that the transmission system 16 of the robot arm 101 has failed, the failure location determining unit 407 outputs information that can identify the occurrence of the failure or the location of the failure, such as warning information, to the monitor 311. The format of information output by the failure location determination unit 407 may be any format, such as display output to the monitor 311, output to a printer, audio output using a buzzer sound, synthesized voice, or the like. For example, in the display output format, in addition to text information such as "A failure has occurred in the joint xx (reducer/xx pulley)", in the case of a warning, the drive torque τ _i , the output torque τ _o, and the torque difference Control information such as τ _io and backlash time T _bl may be displayed simultaneously. Further, a part of the above display example may be replaced with an arbitrary icon or symbol instead of text information. Further, the failure location determination unit 407 may transmit a stop signal for the servo motor 1 to the servo control device 313 in order to emergency stop the joint in question.

Next, a method of designing profile data constituting the failure location determination profile 332 shown in FIG. 7 will be described. The assembly/transfer operations in the production equipment in which the robot system 500 is used are repeated predetermined operations, and the torque applied to the joints 112 of the robot arm 101 during the same operation is approximately the same each time. Therefore, a failure diagnosis timing is determined in a predetermined assembly/transfer operation. This failure diagnosis timing definition information is set to always include the reversal motion of the joint 112. Alternatively, it is also possible to automatically create the definition information of the reversal fault diagnosis timing. For example, if the CPU 201 analyzes the teaching information for controlling the robot arm 101, it is possible to determine a specific movement of a specific joint, for example, the timing at which the rotation of the joint is reversed, or the interval including that timing.

The failure location determination profile 332 is designed from the torque applied to the joint 112 at the failure diagnosis timing. For example, at the time of failure diagnosis, the tightening of the set screw 4 becomes loose as shown in FIG. 8(b), and play occurs between the motor shaft 2 and the motor shaft side pulley 3. In that case, the load torque applied to the servo motor 1 is approximately zero until the backlash is eliminated, so the current flowing through the servo motor 1 is a no-load current. The drive torque is obtained by multiplying the no-load current by the torque constant Kt and the reduction ratio N, and the same value becomes τ _a in the failure location determination profile 332.

In addition, when the teeth of the belt 5 are worn and slip between the belt 5 and the pulley 6 on the reducer side, the torque applied to the servo motor 1 is the starting torque, the torque required to turn the inertia of the motor shaft side pulley 3, and the belt 5. This is the sum of the torque generated by the frictional force between the pulley 6 on the reduction gear side and the pulley 6 on the reduction gear side. That is, the same value becomes τ _b in the failure location determination profile 332.

Further, a set screw (not shown) that fixes the reducer input shaft 7 and the reducer side pulley 6 becomes loose, and the reducer input shaft 7 and the reducer side pulley 6 move relative to each other. In that case, the torque applied to the servo motor 1 is the sum of the starting torque and the torque for moving the motor shaft side pulley 3, belt 5, and reduction gear side pulley 6, and the same value becomes τ _c in the failure location determination profile 332. .

Further, the normal amount of backlash between the driving gear 13 and the driven gear 14 in the reducer 12 is predefined in the specifications of the reducer. The backlash amount is converted into a pulse value of the encoder 11, and the backlash occurrence time is determined from the pulse value and the rotational speed of the joint 112 at the failure diagnosis timing, and the same value becomes _Ta in the failure location determination profile 332. Note that the rotational speed is the same as the rotational speed of the joint 112 when the robot arm 101 operates in the production equipment.

The failure location determination profile 332 designed by the above method may be stored in the profile storage unit 409 in a format such as a threshold data list, or may be stored as a lookup table. Alternatively, τ _a , τ _b , τ _c , and T _a may be determined experimentally in advance.

Next, driving torque calculation and output torque acquisition of the robot arm 101 will be explained with reference to FIG. 9. FIG. 9 shows the flow of processing operations for calculating the drive torque of the robot arm 101 and obtaining the output torque. Each step (control process) shown in FIG. 9 is executed by the CPU 201 reading out the torque acquisition program 330 stored in the HDD 204.

In FIG. 9, the motor current acquisition unit 402 acquires the three-phase current of the servo motor 1 at every control period (for example, 100 μsec) (step S1). In step S2, the driving torque calculation unit 403 converts the three-phase current into _{a q} -axis current iq, and further calculates the driving torque τ _i from the current and stores it in the torque storage unit 408. The data storage format in the torque storage section 408 at this time is arbitrary. In this manner, in the present embodiment, the drive torque is acquired via the drive current of the servo motor 1 in the drive torque acquisition step.

Similarly, the output torque acquisition unit 404 acquires the output torque τ _o from the torque sensor 15 at every control period (for example, 100 μsec) and stores it in the torque storage unit 408 (step S3).

In step S4, the joint reversal motion determination unit 401 determines the rotation angle from the pulse signal obtained from the encoder 11, and when the rotation angle is reversed, in step S5, the failure location determination program 331 stored in the HDD 204 is read out and executed. Thereafter, the torque acquisition program 330 of FIG. 9 ends. Note that if the rotation angle is not reversed, the torque acquisition program 330 immediately ends without executing step S5.

Next, a process for determining a failure location in the transmission system 16 of the robot arm 101 will be described with reference to FIG. 10. FIG. 10 shows the flow of processing for determining a failure location in the transmission system 16 of the robot arm 101. Each step shown in FIG. 10 is executed by the CPU 201 reading out the failure location determination program 331 stored in the HDD 204.

When a predetermined period of time (for example, 4 seconds) has elapsed since the failure location determination program 331 was read, the backlash time calculation section 405 and the torque difference calculation section 406 are instructed to acquire the data stored in the torque storage section 408. It is executed (step S11).

In step S12, the backlash time calculation unit 405 calculates the backlash time _Tbl . Furthermore, in step S13, the torque difference calculation unit 406 calculates the torque difference τ _io .

If the calculated torque difference τ _io satisfies the condition 0≦τ _io <τ _a in step S14, the motor shaft side pulley 3 is determined to be a failure location in step S15, and this fact is displayed on the monitor 311. If the same condition is not satisfied, step S16 is executed.

In step S16, if the torque difference τ _io satisfies the condition τ _a ≦τ _io <τ _b , the belt 5 is determined to be a failure location in step S17, and this fact is displayed on the monitor 311. If the same condition is not satisfied, step S18 is executed.

In step S18, if the torque difference τ _io satisfies the condition τ _b ≦τ _io <τ _c , the reduction gear pulley 6 is determined to be a failure location in step S19, and this fact is displayed on the monitor 311. If the same condition is not met, step S20 is executed.

If the backlash time T _bl satisfies the condition T _bl ≧T _a in step S20, the reducer 12 is determined to be a failure location in step S21, and this fact is displayed on the monitor 311. If the same condition is not met, there is no failure in the transmission system 16 and it is normal, and the failure location determination program 331 is terminated.

If it is determined that there is a failure at any location, the above-mentioned arbitrary format identification information that can identify the failure location is displayed on the monitor 311, and then a stop signal is sent to the servo control device 313 in step S22. Thereby, it is possible to bring a robot device that has a failure in a specific part of a joint to an emergency stop. Thereafter, the failure location determination program 331 is terminated.

As described above, according to the robot system 500 of the first embodiment, a failure in the transmission system 16 (drive system) of the robot arm 101 can be detected. Furthermore, even if the transmission system 16 includes a plurality of parts such as pulleys and reducers that use different transmission methods, the faulty part can be identified. Failure diagnosis using the failure location determination program 331 can be performed without disassembling the robot arm 101, for example, by comparing the drive torque of the drive system motor, the output torque of the drive system, and profile data created in advance.

<Embodiment 2>
FIG. 11 shows a functional configuration of a robot system 500 according to the second embodiment. FIG. 11 shows the configuration of a control device that performs failure diagnosis as a functional block diagram in the same format as FIG. 5 of the first embodiment. In this embodiment, the basic configuration of the robot system 500 is assumed to be the same as that in Embodiment 1, and redundant explanation will be omitted below. Further, the same reference numerals will be used below for the same or similar constituent members as in the first embodiment described above, and detailed description thereof will be omitted.

In the first embodiment, the rotation speed at the failure diagnosis timing is treated as being the same as the rotation speed when the failure location determination profile 332 is designed. However, due to the takt time of the production equipment in which the robot system 500 is used, the rotation speed may change from the rotation speed when the failure location determination profile 332 is acquired. In that case, it is necessary to correct the backlash time T _bl according to the rotation speed. This correction means will be described below.

Below, the configuration and control thereof that correct the backlash time T _bl in accordance with the rotational speed, which is different from the first embodiment, will be mainly explained. First, functional blocks realized when the CPU 201 and the HDD 204 execute the control program to correct the backlash time T _bl according to the rotational speed according to the second embodiment will be described with reference to FIG. 11. . FIG. 11 is a functional block diagram showing a control system of a robot system 500 according to the second embodiment.

The backlash time correction unit 410 in FIG. 11 calculates the rotation angle by counting the pulse signals received from the encoder 11, and calculates the rotation speed from the amount of variation in the rotation angle. Furthermore, the corrected backlash time Tbl _' is determined using, for example, the following equation (3). In the formula (3) below, T _bl is the backlash time calculated by the backlash time calculation unit 405, ω ₀ is the rotation speed when the failure location determination profile 332 is designed, and ω ₁ is the rotation speed when the failure location determination profile 332 is designed. It is the rotational speed of time.

The corrected backlash time T _bl' is the time when the rotational speed is converted to ω ₀ , and the failure location determination profile 332 can be used for failure location determination. Through the above-described processing, according to the second embodiment, even if the rotational speed of the joint has changed since the time when the failure location determination profile 332 was designed, the backlash time can be corrected by the rotational speed, so that an appropriate failure diagnosis can be performed. can be carried out.

FIG. 12 shows a flowchart showing the processing operation of the failure location determination program 331 according to the second embodiment. Each step shown in FIG. 12 is executed by the CPU 201 reading out the failure location determination program 331 stored in the HDD 204.

FIG. 12 is a flowchart corresponding to FIG. 10 of the first embodiment, and in FIG. 12, the same or equivalent steps as in FIG. 10 are given the same step numbers. In the following, only the parts of the failure location determination program 331 shown in FIG. 12 that are different from the processing of the first embodiment shown in FIG. 10 will be explained. In FIG. 12, the difference from the process of the first embodiment shown in FIG. 10 is that the corrected backlash time acquisition process in steps S32, S33, and S34 is performed instead of the corrected backlash time acquisition process in step S12 in FIG. The point is that it is used.

Step S11 in FIG. 12 is equivalent to step S11 in FIG. 10, and in step S32, the backlash time T _bl is obtained similarly to step S12 in FIG. Subsequently, in step S33, the backlash time correction unit 410 counts the pulse signals received from the encoder 11 to determine the rotation angle, and further calculates the rotation speed. In step S34, the backlash time correction unit 410 calculates a corrected backlash time _Tbl' from the backlash time _Tbl and the rotational speed obtained in step S33 using the above equation (3). Thereafter, the same control as in FIG. 10 of the first embodiment is performed using the corrected backlash time T _bl' acquired in step S34.

As explained above, according to the present embodiment, the backlash time T _bl can be corrected by the backlash time correction unit 410. As a result, according to the present embodiment, even if the rotational speed of the joint has changed from the rotational speed at which the failure location determination profile 332 was designed, it is possible to appropriately diagnose the failure of the drive system of the joint of the robot device. I can do it.

The present invention provides a program that implements one or more of the functions of the embodiments described above to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device reads and executes the program. This can also be achieved through processing. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

DESCRIPTION OF SYMBOLS 1...Servo motor (motor), 3...Motor shaft side pulley, 5...Belt, 6...Reducer side pulley, 11...Encoder, 12...Reducer, 15...Torque sensor, 100...Robot device, 101...Robot arm, 111 to 116...Joint, 200...Robot control device, 201...CPU, 204...HDD, 300...Teaching pendant, 500...Robot system, W...Work.

Claims (23)

A method for controlling a robot system comprising a robot, at least two devices that transmit a first torque from a motor that drives a joint of the robot and output it as a second torque, and a control device,
a first torque acquisition step in which the control device acquires the first torque when the rotation direction of the motor is reversed;
a second torque acquisition step in which the control device acquires the second torque when the rotation direction of the motor is reversed;
The control device identifies a device that is in a failure state among the at least two devices based on the first torque, the second torque, and data for identifying a failure state of each of the devices. A specific step of
A control method characterized by: In the control method according to claim 1,
The second torque is obtained by a torque sensor provided on the output side of the at least two devices.
A control method characterized by: The control method according to claim 1 or 2,
the data is profile data;
A control method characterized by: The control method according to any one of claims 1 to 3,
In the identifying step, the control device determines which of the at least two devices is in a failure state by comparing a torque difference, which is a difference between the first torque and the second torque, with the data. identify the equipment that is
A control method characterized by: In the control method according to any one of claims 1 to 4,
In the identifying step, the control device includes data for identifying failure states of the first torque, the second torque, and each of the devices, as well as data for determining whether backlash occurs between the at least two devices. identifying which of the at least two devices is in a faulty state based on the time of the interval and the data corresponding to the backlash;
A control method characterized by: In the control method according to claim 5,
In the specific step, the control device corrects the time based on the speed of the motor when the backlash occurs and the speed of the motor when data corresponding to the backlash is acquired. to identify a device in a failure state among the at least two devices;
A control method characterized by: In the control method according to any one of claims 1 to 6,
In the identifying step, the control device determines a failure state of the at least two devices based on a changing shape of a waveform of a difference between the first torque and the second torque and data corresponding to the waveform. Identify the device that is
A control method characterized by: The control method according to any one of claims 1 to 7,
The at least two devices include any one of a reducer, a pulley, and a belt.
A control method characterized by: 9. The control method according to claim 1, wherein when the rotational direction of the motor is reversed, backlash occurs in a reduction gear provided in the robot. The control method according to claim 9 ,
The control device determines that a first pulley provided on the rotating shaft of the motor is in a failure state based on the first torque, the second torque, and the torque generated in the motor when the motor is in a no-load state. determine whether or not
A control method characterized by: The control method according to claim 10 ,
The failure state of the first pulley is a state in which play is occurring between the rotating shaft and the first pulley.
A control method characterized by: The control method according to any one of claims 9 to 11 ,
The control device includes the first torque, the second torque, the starting torque of the motor, the torque necessary to rotate the first pulley provided on the rotating shaft of the motor, the belt, and the speed reducer. and determining whether or not the belt is in a failure state based on the torque generated by friction with a second pulley provided in the belt.
A control method characterized by: The control method according to claim 12 ,
The failure state of the belt is a state in which the teeth of the belt are worn;
A control method characterized by: The control method according to any one of claims 9 to 13 ,
The control device operates the first torque, the second torque, the starting torque of the motor, a first pulley provided on the rotating shaft of the motor, a second pulley provided on the speed reducer, and a belt. determining whether or not the reduction gear and a second pulley provided in the reduction gear are in a failure state based on the torque for the reduction gear;
A control method characterized by: The control method according to claim 14 ,
The failure state of the speed reducer and the second pulley provided in the speed reducer is a state in which a screw fixing the input shaft of the speed reducer and the second pulley provided in the speed reducer is loosened.
A control method characterized by: The control method according to any one of claims 1 to 15 ,
an output step in which the control device outputs information that can identify the device that is in a failure state and that is identified in the identifying step;
A control method characterized by: The control method according to claim 16 ,
The control device performs the output step at least one of display output to a display device, output to a printer device, audio output to an audio output device, and stopping of the joint having a device in a failure state. execute using
A control method characterized by: The control method according to claim 17 ,
The control device displays the information on the display device using at least one of characters, torque values, backlash times, icons, and symbols.
A control method characterized by: The control method according to any one of claims 1 to 18 ,
The control device obtains the first torque based on a current flowing through the motor, a torque constant, and a reduction ratio.
A control method characterized by: A program capable of executing the control method according to claim 1 . A computer-readable recording medium storing the program according to claim 20 . A robot system comprising a robot and a control device that acquires the states of at least two devices that transmit a first torque from a motor that drives joints of the robot and output it as a second torque,
a first torque acquisition step in which the control device acquires the first torque when the rotation direction of the motor is reversed;
a second torque acquisition step in which the control device acquires the second torque when the rotation direction of the motor is reversed;
The control device identifies a device that is in a failure state among the at least two devices based on the first torque, the second torque, and data for identifying a failure state of each of the devices. the specific process to be carried out,
A robot system characterized by: A method for manufacturing an article, comprising manufacturing the article using the robot system according to claim 22 .

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