JP7267725B2 - Robot control method, program, recording medium, robot system, article manufacturing method - Google Patents

Description

The present invention relates to an inspection method for a robot device, a control program for a robot device, and a robot system, which includes a drive source for driving joints and whose position and orientation are controlled based on trajectory data.

2. Description of the Related Art In recent years, in the field of industrial production, production (manufacturing) devices using multi-joint robot devices (hereinafter referred to as robot devices) capable of realizing complicated and high-speed manufacturing operations of articles like human hands are becoming widespread. In a robot device capable of this type of complex motion, the higher the degree of freedom of motion of the robot arm, the greater the possibility that the robot arm will come into contact with or interfere with other objects such as workpieces and tools in the surrounding environment during work. There is For example, if a robot arm comes into contact with a surrounding object or the like and a shock is applied to a speed changer (reducer) arranged at a joint of the arm, there is a risk that a failure such as tooth jumping may occur in the speed reducer.

An actuator that drives the joints of this type of robot arm is composed of, for example, a servomotor and a transmission. This type of transmission is generally configured as a speed reducer because of the relationship between the rotational speed range of a rotary drive source such as a servomotor and the rotational speed range for rotating the link of the arm. Therefore, hereinafter, a speed reducer may be exemplified as a typical transmission used in this type of robot device.

As this transmission, a transmission using a strain wave gear mechanism, which can obtain a large reduction ratio compared to its size and shape, is widely used. In a speed changer (reducer) using this strain wave gear mechanism, there is a possibility that failure such as tooth skipping may reduce the accuracy of joint angle transmission and reduce the operating accuracy of the robot arm.

In view of the circumstances as described above, in recent years, various techniques have been proposed regarding interference and collision of robot arms.

As a technology to detect the state of the transmission of joints after arm interference and collision, for example, torque detection when the joint other than the joint to be inspected is temporarily stopped and a predetermined position command is given only to the target joint to perform a predetermined operation. A technique for judging an abnormality of a transmission by comparing a value with a reference value has been proposed (see Patent Document 1).

JP 2009-202335 A

In the technique described in Patent Document 1, since the joints other than those to be inspected are stopped, the movement differs from that in the normal operation based on the trajectory data, and the area through which the arm and hand pass is also the same as in the normal operation. It is different from Therefore, when an attempt is made to perform an inspection, there is a risk of colliding with peripheral equipment, such as equipment for saving workpieces and tools, which are installed so as not to collide with each other during normal operation. In order to avoid this danger, it was necessary to remove the robot from the apparatus and set it up in a large working space for inspection, or to temporarily evacuate the surrounding related equipment. Moreover, if such a workaround is implemented, in addition to work to restore the robot and peripheral equipment, work to confirm the positional accuracy is also required, so there is a problem that it takes a long time to restore the device.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to shorten the recovery time of the device by enabling the state of the transmission to be detected safely and at high speed while the robot is installed on the device.

In order to solve the above-described problems, the present invention provides a control method for a robot having a plurality of joints and controlled based on a predetermined trajectory for executing a normal motion , wherein the predetermined joint among the plurality of joints is driven to make natural vibration. operating the predetermined joint at a speed, operating the robot so that the robot maintains the predetermined trajectory, acquiring the amplitude of the natural vibration of the predetermined joint, and obtaining the state of the predetermined joint based on the amplitude A control method characterized by obtaining

According to the above configuration, it is possible to inspect the joints of the robot apparatus using the resonance phenomenon more safely than before, and shorten the time until the apparatus is restored.

1 is a perspective view showing the overall configuration of a robot device according to an embodiment of the present invention; FIG. FIG. 2 is a cross-sectional view showing a configuration near a joint of the robot apparatus of FIG. 1; 3 is a block diagram showing the configuration of a control device of the robot device of FIG. 2; FIG. 3 is a block diagram of a functional configuration of a control device of the robot device of FIG. 2; FIG. 2 is a flow chart showing a control procedure for inspection of the robot apparatus of FIG. 1; FIG. 4(a) to 4(f) each show a procedure for generating an inspection operation that maintains a production trajectory in inspection (or diagnosis) of the robot apparatus of FIG. 1; FIG. 2 is a flow chart diagram showing a calculation procedure for calculating a judgment value A from a result of vibration inspection in inspection of the robot apparatus of FIG. 1; FIG. 2(a) and 2(b) are diagrams each showing a method of FFT processing when generating a determination value A in the inspection process (inspection mode) of the robot apparatus of FIG. 1. FIG.

DETAILED DESCRIPTION OF THE INVENTION Embodiments for carrying out the present invention will now be described with reference to the embodiments shown in the accompanying drawings. It should be noted that the embodiment shown below is merely an example, and, for example, details of the configuration can be changed as appropriate by those skilled in the art without departing from the scope of the present invention. Further, the numerical values taken up in the present embodiment are reference numerical values and do not limit the present invention.

The robot apparatus according to the present embodiment is an industrial robot apparatus that performs assembly work, etc., and has functions for detecting and preventing deterioration of the transmission of the robot apparatus, particularly failures (functions capable of inspecting the state). It has The term "failure" as used in the present embodiment includes not only the unusable state of the transmission but also the normal unusable state in which the transmission cannot be used for normal purposes. This normal unusable state means, for example, a state in which the allowable range (usually usable state) for the usage conditions required for a predetermined application is exceeded.

As described above, the transmission of the joint of the robot device is generally configured as a speed reducer based on the relationship between the rotation speed range of the rotary drive source such as the servomotor and the rotation speed range for rotating the link of the arm. There are many. For this reason, the speed reducer will be exemplified below as a typical transmission used in this type of robot apparatus.

In this embodiment, the (deterioration) state of a speed reducer using a strain wave gear mechanism is inspected through the resonance phenomenon that occurs in the joints of the robot device. The detection of the deteriorated state of the transmission of the joint portion of the robot device through the resonance phenomenon of the joint portion is based on the following principle.

If the speed reducer is damaged due to the above-described cushioning or collision, an angle transmission error occurs due to tooth skipping or the biting of small pieces caused by the damage. This angle transmission error is, for example, the error between the input angle on the primary side of the speed reducer and the output angle obtained on the secondary side of the speed reducer via the gear ratio.

On the other hand, the joints of a robot that uses a speed reducer that uses strain wave gears have a resonance frequency f (Hz: natural frequency) as shown in the following equation (1).

Here, f is the resonance frequency (Hz: natural frequency) of the vibration system including the speed reducer, K is the spring constant of the speed reducer, and J is the load inertia (Kgm2) of the load driven by the joint provided with the speed reducer. be. Among them, the spring constant K is a constant term and is unique to each type of speed reducer. Also, J corresponds to the moment of inertia applied to the target joint axis, and its magnitude varies depending on the posture of the robot arm.

Also, the speed reducer is a rotary drive system, and the resonance frequency f (Hz: natural frequency) corresponds to the rotation speed R (rpm: rotation speed per minute) as in the following equation (2).

Therefore, when the rotation speed of the input side of the speed reducer reaches the rotation speed R that satisfies the equation (2), a resonance phenomenon occurs in the joint. In other words, when the joint is driven, speed unevenness matching the resonance frequency f occurs in the vicinity of the driving rotation speed of the equation (2).

There is a relationship between the angle transmission error of such a speed reducer and the magnitude of resonance. For example, if a reduction gear gear chipped due to a sudden overload such as a collision is periodically bitten by other teeth, it will cause an angle transmission error, and if it matches the resonance frequency, the arm is normal. It resonates more greatly than in a normal state. Also, even if there is no damage to the gears, if the reducer (whole) is elliptically distorted, the web generator, which is one of the parts that make up the strain wave gearing mechanism of the reducer, will deform periodically, causing similar damage. resonates greatly with

As described above, it can be considered that the resonance phenomenon that occurs in the joints of the robot manifests itself in the form of vibration of the joints that can be detected by the encoder or the current sensor as the angular transmission error of the speed reducer. Therefore, by measuring the intensity of resonance, such as the amplitude, that occurs in the joints (reducer of the robot arm) of the robot arm, and comparing this resonance amplitude with a predetermined reference value as an index (reference) value corresponding to the angular transmission error, deceleration can be achieved. machine can be inspected (or diagnosed).

When performing this inspection (or diagnosis), the safest robot movement on the device is on a trajectory preset for normal operation. In other words, since there are no obstacles on the trajectory originally set for production or the like, it can be said that it is basically safe as long as other peripheral devices do not protrude. Therefore, by performing an inspection operation that generates resonance while maintaining a trajectory predetermined for normal operation, inspection can be safely performed on the apparatus.

By the way, robots generally have multiple joints that operate at the same time, and their postures change every second. Therefore, the moment of inertia applied to each joint is not constant, and the resonance frequency of the joint also changes moment by moment. In order to generate resonance while maintaining the same trajectory as the production operation, the number of rotations of the drive source of the target joint is controlled according to the changing resonance frequency, while other joints follow the determined production trajectory . Adjust to maintain.

1 to 3 show an example configuration of a robot system 500 in which the present invention can be implemented. FIG. 1 schematically shows the overall configuration of a robot system 500. As shown in FIG. FIG. 2 shows a cross-sectional structure near one joint of the robot system 500 of FIG. 3 shows the configuration of the control device 200 of the robot system 500 of FIG.

As shown in FIG. 1, the robot system 500 includes a robot device 100 that assembles a workpiece W, a control device 200 that controls the robot device 100, and a teaching pendant 300 connected to the control device 200.

The robot apparatus 100 includes a 6-axis articulated robot arm 101, a hand (end effector) 102 connected to the tip of the robot arm 101, and a force sensor (not shown) capable of detecting a force acting on the hand 102. It has

The robot arm 101 includes a base portion 103 (base) fixed to a workbench, a plurality of links 121 to 126 that transmit displacement and force, and a plurality of joints that connect the links 121 to 126 so as to be able to turn or rotate. 111-116. In this embodiment, the configurations of the joints 111 to 116 are basically the same. For this reason, in the following description, regarding the configuration common to the joints 111 to 116, the configuration of the joint 112 between the link 121 and the link 122 will be described as a representative, and the other joints 111, 113 to 116 will be specifically described. explanation is omitted. This embodiment can be implemented if at least one of the joints 111 to 116 of the robot arm 101 has the same configuration as the joint 112 .

As shown in FIG. 2, the joint 112 includes a servomotor (motor) 1 as a rotational drive source and a speed reducer 11 for reducing (speed-changing) the output of the servomotor 1 (transmission). The rotation angle (output side rotation angle) of the joint 112 on the output side of the speed reducer 11 is detected by the output side encoder 16 (rotary encoder). The output-side encoder 16 and the input-side encoder 10, which will be described later, have the same configuration as a general rotary encoder, and are configured by optical or magnetic type rotary encoder devices.

The servomotor 1 can be composed of, for example, an electromagnetic motor such as a brushless DC motor or an AC servomotor. The servomotor 1 includes a rotating portion 4 composed of a rotating shaft 2 and a rotor magnet 3, a motor housing 5, bearings 6 and 7 that rotatably support the rotating shaft 2, and a stator coil that rotates the rotating portion 4. 8 and . The bearings 6 , 7 are provided in the motor housing 5 and the stator coil 8 is attached to the motor housing 5 . Also, the servomotor 1 is surrounded by a motor cover 9 . The servo motor 1 may be provided with a brake unit for maintaining the posture of the robot arm 101 when the power is turned off, if necessary.

The speed reducer 11 includes a web generator 12 as an input section, a circular spline 13 as an output section, and a flexspline 14 arranged between the web generator 12 and the circular spline 13 . The web generator 12 is connected to the other end side of the rotating shaft 2 of the servomotor 1 . Circular spline 13 is connected to link 122 . Flexspline 14 is connected to link 121 . That is, the connecting portion between the rotating shaft 2 of the servomotor 1 and the web generator 12 is the input side of the speed reducer 11 , and the connecting portion between the flexspline 14 and the link 121 is the output side of the speed reducer 11 . Then, the rotation shaft 2 of the servo motor 1 is decelerated to 1/N (reduced by the deceleration ratio N) via the decelerator 11, and the links 121 and 122 rotate relatively. The rotation angle on the output side of the speed reducer 11 at this time is the actual output angle, that is, the angle of the joint 112 .

An output-side encoder (output-side angle sensor) 16 is provided on the output side of the speed reducer 11 and detects the relative angle between the link 121 and the link 122 . Specifically, the output-side encoder 16 generates an output-side pulse signal as the joint 112 is driven (relative movement between the link 121 and the link 122), and outputs the generated output-side pulse signal to the control device 200. . A cross roller bearing 15 is provided between the link 121 and the link 122 , and the link 121 and the link 122 are rotatably connected via the cross roller bearing 15 .

An input-side encoder (input-side angle sensor) 10 can be arranged on the rotary shaft 2 of the servomotor 1, that is, on the input side of the speed reducer 11. FIG.

The hand 102 includes a plurality of fingers capable of gripping the work W and an actuator (not shown) that drives the plurality of fingers, and is configured to be able to grip the work by driving the plurality of fingers. The force sensor detects forces and moments acting on the hand 102 when the hand 102 grips the work W with a plurality of fingers.

As shown in FIG. 3, the control device 200 includes a CPU (arithmetic unit) 201, a ROM 202, a RAM 203, an HDD (storage unit) 204, a recording disk drive 205, and various interfaces 211 to 215. ing.

A ROM 202 , a RAM 203 , an HDD 204 , a recording disk drive 205 and various interfaces 211 to 215 are connected to the CPU 201 via a bus 216 . The ROM 202 stores basic programs such as BIOS. A RAM 203 constitutes a storage area for temporarily storing results of arithmetic processing by the CPU 201 .

The HDD 204 is a storage unit that stores various data that are the results of arithmetic processing by the CPU 201, and records a control program 330 (including, for example, an inspection program described later) for causing the CPU 201 to execute various arithmetic processing. It is a thing. The CPU 201 executes various arithmetic processes based on a control program 330 recorded (stored) in the HDD 204 . The recording disk drive 205 can read various data and programs recorded on the recording disk 331 .

In particular, a control program 330 corresponding to a later-described control procedure executed by the computer (CPU 201) is stored in the HDD 204 (or ROM 202) of FIG. 3, for example. Storage means such as the ROM 202 and HDD 204 constitute a computer-readable recording medium. Also, (part of) computer-readable recording media such as the ROM 202 and HDD 204 may be configured by removable flash memory devices or magnetic/optical disks. In addition, a program corresponding to the control procedure described later executed by the computer (CPU 201) may be downloaded via a network, etc., and may be installed, for example, in the HDD 204, or may be configured to update software installed therein. .

A teaching pendant 300 operated by a user is connected to the interface 211 . The teaching pendant 300 is provided with a user interface including a display device such as an LCD panel and a keyboard. Using this user interface, the user can perform a teaching operation of the robot device 100 . As a result, it is possible to specify the position and orientation (teaching point) of a reference point set on the hand of the robot arm 101, for example, and to specify the joint angles of the joints 111-116. Teaching pendant 300 outputs the input target joint angles of joints 111 to 116 to CPU 201 via interface 211 and bus 216 .

The output-side encoders 16 of the joints 111 to 116 of the robot arm 101 are connected to the interface 212 . The output encoder 16 outputs a pulse signal corresponding to the joint angle to the CPU 201 via the interface 212 and the bus 216 as described above. Furthermore, a monitor 311 and an external storage device 312 (rewritable nonvolatile memory, external HDD, etc.) can be connected to the interfaces 213 and 214, respectively. The monitor 311 is, for example, a display device such as an LCD panel, and is used for monitor display of the control state of the robot device 100, and can also be used to display information and warning messages related to inspection processing, which will be described later.

A servo control device 313 is connected to the interface 215, and the CPU 201 performs servo control via the bus 216 and the interface 215 at predetermined intervals with drive command data indicating the control amount of the rotation angle of the rotary shaft 2 of the servomotor 1. Output to device 313 .

The servo control device 313 calculates the amount of current output to the servo motors 1 of the joints 111 to 116 of the robot arm 101 based on the drive command received from the CPU 201 . The servo control device 313 supplies a current corresponding to the obtained current value to the servo motor 1, thereby controlling the joint angles of the joints 111 to 116 of the robot arm 101. FIG. That is, the CPU 201 can control the driving of the joints 111 to 116 by the servomotor 1 via the servo control device 313 so that the angles of the joints 111 to 116 become the target joint angles.

Here, with reference to FIG. 4, the functions executed by the control device 200 when executing the inspection program of this embodiment (for example, FIG. 5 described later) will be described. Each functional block in FIG. 4 is implemented by computer (CPU 201) hardware and its software. Especially the software part is stored in computer-readable recording media, such as ROM302 and HDD204.

The functional configuration of FIG. 4 includes an actual output angle calculator 402 , a resonance amplitude calculator 404 that calculates an angle transmission error due to resonance from the rotation angle, and a joint state determiner 406 . Further, the functional configuration of FIG. 4 includes an amplitude reference value storage unit 405 for inspecting the joint speed reducer 11 and an angle information storage unit 403 for storing and accumulating the output side rotation angle detected by the output side encoder 16. , a testing motion storage unit 407 that stores testing motions, and a testing motion generation unit 408 that generates testing motions.

The actual output angle calculator 402 counts the output side pulse signal (s401) received from the output side encoder 16 to obtain the output side rotation angle (s402), and outputs it to the servo controller 303 and the angle information storage section 403. The servo control device 303 controls the joint of the servo motor 1 while referring to the actual output angle information (s402) output from the actual output angle calculation unit 402 based on the inspection motion information s407 stored in the inspection motion storage unit 407. Angle control.

The actual output angle calculation unit 402, the resonance amplitude calculation unit 404, the joint state determination unit 406, and the inspection motion generation unit 408 are implemented by a CPU that operates according to a program for executing this embodiment. However, it is not limited to this, and may be realized by separate hardware.

The testing motion information s407 defines testing motions during joint testing, is generated by the testing motion generation unit 408 based on trajectory data predetermined for normal motions, and is stored in the testing motion storage unit. 407. Since the characteristics indicated by the formulas (1) and (2) differ for each joint (111 to 116), the inspection motion information s407 has different contents for each joint (111 to 116) to be inspected. In particular, the motion information for inspection s407 generates motion data for inspection such that the joint to be inspected passes through a path based on the trajectory data at a driving speed at which the joint to be inspected resonates. In addition, corresponding to the natural frequency of the joint to be inspected that changes according to the posture of the robot arm, the rotational speed on the input side of the reduction gear is maintained at a constant multiple of the natural frequency, and the trajectory used as the reference Based on the data, adjustments are made to maintain the same trajectory as the normal motion trajectory . Such an inspection operation enables safe inspection on the apparatus.

The angle information storage unit 403 accumulates the angle information (s402) output from the actual output angle calculation unit 402. FIG. The reference value storage unit 405 stores the reference value s405 required for determination, and outputs it to the joint state determination unit 406. FIG. The resonance amplitude calculation unit 404 reads out the accumulated angle information s403 from the angle information storage unit 403, calculates the judgment value A (s404) necessary for the examination, and outputs it to the joint state judgment unit 406. The joint state determination unit 406 compares the reference value s405 output from the reference value storage unit 405 and the determination value A (s404) calculated from the resonance amplitude calculation unit 404, and determines the joint state of the robot.

The angle information storage unit 403, the reference value storage unit 405, and the inspection operation storage unit 407 are all stored in the HDD 204, but may be other storage devices such as RAM.

Next, inspection processing of the joints (111 to 116) performed in the above configuration will be described with reference to FIG. FIG. 5 shows the flow of inspection processing (inspection mode) of the joints (111 to 116) of the present embodiment, which is executed under the control of the control device 200, particularly the CPU 201, in the above configuration.

In the present embodiment, as described above, the state of the joint is inspected by utilizing the resonance phenomenon that occurs at a frequency centered on the resonance frequency corresponding to the natural frequency of the joint in question in a posture conforming to the production operation.

The inspection process (inspection mode) in FIG. 5 is performed during regular inspection of the robot and after an event such as unintended interference or collision occurs. As a trigger for executing the inspection process (inspection mode) of FIG. 5, for example, an operation of selecting an inspection mode by an operator using a user interface such as the teaching pendant 300 can be considered.

The inspection process (inspection mode) in FIG. 5 is performed for each axis of the joints (111 to 116). When an operator (user) selects an inspection process (inspection mode), an axis to be inspected is determined in step S501 of FIG. The inspection process (inspection mode) in FIG. 5 is configured to be executed from a specific axis (joint) to all axes (all joints). Control may be performed for only one or more axes. It is usually desirable to perform the examination on all axes (all joints). The order of the joints to be inspected may be in order from the axis closest to the base portion 103, or the user may designate any order.

Next, in step S502, the reference value s405 of the axis to be inspected and the inspection motion information s407 are read from the reference value storage unit 405 and the inspection motion storage unit 407, respectively. The reference value storage unit 405 and the inspection operation storage unit 407 can be arranged in the form of a data file, for example, in the HDD 204 or the like. These reference values s405 and inspection motion information s407 differ for each joint (111 to 116) to be inspected. This is because, for example, the characteristics expressed by equations (1) and (2) differ for each joint (111-116). Therefore, the reference value s405 and the inspection motion information s407 are prepared for each axis (inertia) in the reference value storage unit 405 and the inspection motion storage unit 407, and the information corresponding to the joint in question is individually stored at the stage of performing the inspection. Read into a work area such as the RAM 203 . Alternatively, when the inspection mode is selected, the reference values and inspection operations for all axes may be read into a work area such as the RAM 203 at once.

In step S503, the joint is inspected. That is, the servo control device 303 drives the axis to be inspected according to the inspection operation information s407 read in step S502. At this time, the pulse value (s401) obtained from the output side encoder 16 is counted by the actual output angle calculation unit 402 at regular intervals, and the value (s402) converted into actual output angle information is stored in the angle information storage unit 403.・Accumulate.

The processing of the checking operation in step S503 is shown in detail as steps S5031-5037 in the right column of FIG. Steps S5031 to S5037 constituting step S503 will now be described in detail.

When the inspection motion is started in step S5031, first, in step S5032, the servo control device 303 moves the robot arm 101 to the starting posture based on the inspection motion information s407 read in step S502.

Next, in step S5033, the angle information storage unit 403 is enabled to store and accumulate the actual output angle information (s402), and the actual output angle information (s402) output from the actual output angle calculation unit 402 is stored. Enable buffer.

Subsequently, in step S5034, the servo control device 303 drives the target joint with a specific motion pattern corresponding to the inspection motion information s407 read in step S502. During this time, the pulse value (s401) obtained from the output-side encoder in step S5035 is successively converted into actual output angle information (s402) by the actual output angle calculator 401, and stored and accumulated in the angle information storage unit 403. Go (step S5036).

When the inspection operation ends, the storage buffer of the angle information storage unit 403 is closed in step S5037, and the shaft output angle information (s402) is saved. It is desirable that the interval at which the pulse value (s401) is read from the output-side encoder 16 be an acquisition cycle that matches the control cycle of the servo control device 303. FIG.

In step S504, the actual output angle information (s402) accumulated in the angle information storage unit 403 in step S503 is processed, and the vibration amplitude of the angle due to resonance is calculated as the determination value s404 (A).

Steps S505 and S506 correspond to an inspection process for inspecting the state of the speed reducer 11. FIG. First, in step S505, the determination value A (s404) calculated in step S504 is compared with the reference value Alim (s405) read in step S502. Here, if the determination value A (s404) exceeds the reference value Alim (s405), it is determined that the reduction gear 11 of the inspection shaft is damaged. Depending on the result of this determination, "the reduction gear is not damaged" in step S506 or "the reduction gear is damaged" (warning message) is output in step S507. These test messages may be output using, for example, the monitor 311 or the display of the teaching pendant 300, or may be output by voice using voice output means (not shown).

When step S505 ends, it is checked in step S508 if there are any joints (axes) that have not yet been tested. If there are any joints (axes) that have not yet been inspected, the process returns to S501, repeats the same processing as above, and inspects all the joints (axes) to be inspected.

As described above, the inspection process (inspection mode) as shown in FIG. 5 can be performed for each joint. In the inspection process (inspection mode) as shown in FIG. 5, a resonance amplitude acquisition step is performed for each specific joint to be inspected. At that time, the motion information for inspection s407 used corresponds to the natural frequency of the target joint, maintains a rotational speed at which the rotational speed on the input side of the reducer is a constant multiple of the natural frequency, and serves as a reference. Define inspection motions that are adjusted to maintain the same production trajectory as the original production trajectory . The natural frequency of the joint in question can be calculated in advance by equation (1), and the rotation speed of the input shaft of the speed reducer at that time can be determined in advance by equation (2).

Therefore, by performing the inspection process (inspection mode) as shown in FIG. 5 for each joint, the judgment value A of the resonance amplitude of the joint can be obtained. The judgment value A of the resonance amplitude can be calculated as, for example, the maximum value of the amplitude of frequency components centered on the resonance frequency. Then, by comparing this judgment value A with a reference value Alim (s405) set for each joint in the same way as the motion information for inspection s407, the joint is inspected, for example, whether damage has occurred (or life has expired). has arrived). The test results can be notified to the user, such as by outputting a display message (or voice message). The output of these messages can be performed, for example, by display output on the monitor 311 or the display of the teaching pendant 300, audio output using an audio output means (not shown), or the like.

The outline of the inspection process (inspection mode) in this embodiment is as shown in FIG. 5, and the details of the robot control performed in the above inspection process (inspection mode) will be further described below.

In this embodiment, the inspection motion defined for each joint by the inspection motion information s407 is a motion that generates resonance in the joint to be inspected while maintaining a predetermined trajectory for normal work. It is characterized by what it does. The inspection motion information s407 is generated by the inspection motion generation unit 408 based on predetermined trajectory data, and stored in the inspection motion storage unit 407. FIG.

The user of the robot selects at least one production motion for each joint and sets it as an inspection motion. At this time, in order to reliably generate resonance, it is desirable to select a motion in which the joint to be inspected moves relatively greatly. Specifically, it is preferable to select an operation in which the speed reducer input shaft of the target joint rotates three times or more.

By the way, as is clear from equations (1) and (2), two factors, namely, the attitude of the robot arm and the motion speed (driving speed) of the joints, affect the aspect of the resonance of the robot joints that occurs during inspection. do. When the posture of the robot arm 101 changes, the magnitude of the load inertia changes according to equation (1). It will operate according to the speed change defined by equation (2).

Generation of an inspection operation based on a production operation will be specifically described with reference to FIGS. Consider a case where the moment of inertia J of the target joint gradually increases with the posture of the robot. This can be easily understood by imagining the second joint when extending the arm horizontally as shown by the solid line from the state shown by the dotted line in FIG. 6(a), for example. At this time, the moment of inertia J applied to the second joint can be calculated from the posture of the robot and the weight of each part as a general dynamics problem. To go.

At this time, the resonance frequency of the target joint changes as the posture changes, as shown in FIG. 6C from Equation 1. In order to generate resonance in the joint, the rotation speed of the drive source should be set so that the input-side shaft of the speed reducer driven by the drive source has a rotation speed that is a constant multiple of the resonance frequency. This multiple is preferably 1/2 times the resonant frequency. This is because the flex spline and circular spline of the speed reducer are in contact at two points. In other words, since the tooth of the flexspline passes through the damaged part twice per rotation of the web generator, if the rotation speed of the input shaft of the speed reducer is 1/2 times the resonance frequency, the frequency of the generated vibration will be the resonance frequency of the target joint. This is because it matches the frequency. From the equation (2), the rotational speed of the speed reducer input shaft is as shown in FIG. 6(d). This makes it possible to determine the rotation speed of the drive source according to the orientation of the target joint. This is the speed command value.

Next, while maintaining the determined rotational speed of the driving source, the position command value is adjusted in the direction of time in order to operate to the point specified in the inspection operation. As a method of adjustment, for example, as shown in FIG. There is a method to extend the command value by multiplying it in the time direction. So far, we have been able to determine the motion only for the target joint.

Subsequently, based on the motion of the target joint determined above, the motion of other joints is adjusted so as to maintain the trajectory of the production motion. As a method of adjustment, for example, as shown in FIG. There is a method of setting each joint angle at that time to each joint.

The inspection motion information s407 generated in this manner has the same trajectory as the production motion and can cause resonance in the target joint. Machine condition can be inspected. In addition, by generating inspection motion information s407 for all axes using this method, all joints mounted on the robot can be inspected on the apparatus.

The examination posture illustrated in FIG. 6A and the examination sequence (inspection motion) as shown in FIG. .

Next, with reference to FIG. 7, a configuration example of processing for calculating the angle transmission error due to resonance from the actual output angle information (s402) accumulated in the angle information storage unit 403 in step S504 of FIG. 5 will be described in detail. FIG. 7 shows a specific processing example after step S504 in the left column of FIG. 5. Step S504 is composed of steps S5041 to S5044.

In step S5042, one data is read out from the actual output angle information (s402) accumulated in the angle information storage section 403 and output to the resonance amplitude calculation section 404. FIG.

Subsequently, in step S5043, unnecessary components are excluded from the read actual output angle information (s402). That is, since the actual output angle information (s402) includes a vibration component due to resonance on the movement of the test motion itself, it is necessary to extract only the resonance component from the vibration component. As a method of extracting the resonance component, there is a method of performing FFT processing for transforming the inspection data from the time domain to the frequency domain.

This FFT processing will be further described with reference to FIG. As shown in FIG. 8A, the FFT processing is performed by providing a certain FFT interval and shifting the interval little by little from the head of the read actual angle information (s402). By doing so, it is possible to accurately capture the vibration of the robot that changes according to the change in posture. It is desirable that the section at this time is set to a degree or more in which the frequency component of interest can be acquired. For example, when focusing on 10 Hz, the time interval is set wider than 100 msec. Also, it is desirable to make the interval shift width as small as possible within a settable range. The FFT result (s5043) thus obtained is output as an amplitude value with respect to time t and frequency f, and is expressed as a color map in FIG. 8(b).

Next, in step S5044, a determination value A is obtained from the FFT result. From the FFT result (s5043) output in step S5043, the component that matches twice the rotation speed of the speed reducer input shaft of the target joint in the inspection motion (that is, the resonance frequency of the joint calculated by equation (1)) is detected and used as the judgment value A of the resonance amplitude. The rotation speed of the reduction gear input shaft of the target joint in the inspection motion can be obtained from the inspection motion information s407.

The processing after step S505 in FIG. 8 is the same as that described in FIG. A notification or warning message is output according to the

As the reference value Alim (s405) used in this determination (S505), since the value detected by the output side encoder 16 is angle information, for example, an allowable angle error can be used as this reference value (permissible value). Conceivable. Specifically, it is conceivable to use the specification value of the angular transmission error of the speed reducer 11 as the reference value. As such a specification value of the angular transmission error, a value published as a catalog specification of the speed reducer 11 may be used. In that case, the standard value Alim (s405) actually used for the joint can be determined by using the published catalog value or by adding or subtracting an appropriate margin.

Note that since a different type of speed reducer 11 may be used for each joint, this reference value Alim (s405) also needs to be prepared for each joint. At step S5041 in FIG. 8, the reference value Alim (s405) prepared for the joint to be inspected is read from the reference value storage unit 405, of course. Further, as the reference value Alim (s405), the positional deviation required for the target joint is calculated from the required positional accuracy of the hand of the robot arm 101 in addition to the above-mentioned specification value of the angle transmission error. may be used as a reference value.

As described above, according to the present embodiment, the motion data for inspection is generated such that the joints resonate while maintaining a predetermined production trajectory . By operating the robot based on this data and obtaining the joint resonance amplitude and using it to determine failure, it is possible to perform inspections while avoiding collisions with objects placed around the robot system. Become. For this reason, there is an effect that determination of replacement of parts of the robot device can be quickly performed on the device. In addition, the state of the transmission arranged at the joint of the robot device can be accurately determined according to the resonance amplitude of the joint measured via the output side angle sensor that measures the rotation angle of the rotation shaft on the output side of the transmission (reduction) gear. Able to judge quickly.

The configuration for inspecting the state of the transmission (reducer) for each inspection process (inspection mode) by comparing the resonance amplitude measured in the current inspection process (inspection mode) with the reference value has been described above. However, it is also possible to inspect the state of the transmission (reducer) by using the state of change (for example, rate of change) between the resonance amplitude acquired in the past inspection process and the resonance amplitude acquired in the current (current) inspection process. be done. For this purpose, for example, the resonance amplitude measured in the inspection process (inspection mode) is stored in a database arranged in the HDD 204 or the like. Then, the rate of change in resonance amplitude is calculated from the joint resonance amplitude acquired in the current inspection process (inspection mode) and the resonance amplitude acquired in the past inspection process, and the state of the transmission is inspected based on the calculated rate of change. do. For example, a threshold value for the rate of change is determined in advance, and if a rate of change in resonance amplitude that exceeds this threshold value (for example, steep) is detected, the transmission is damaged or has reached the end of its service life. A check can be made that it has arrived and needs to be replaced.

In the above embodiment, a method using an output-side encoder was shown in order to more accurately inspect the state of the speed reducer. However, inspection using this technique is possible.

In the above embodiment, the driving speed is determined based on the resonance frequency. However, it is also possible to generate a trajectory for inspection within a range in which the resonance frequency has a certain width and the driving speed has a certain width. good. Although the amplitude width itself at the time of resonance becomes somewhat smaller, if a certain degree of resonance occurs and failure inspection can be performed, it is not necessary to determine the trajectory based on the value of the resonance frequency.

The inspection method of the robot device shown in the above embodiment can be applied to various robot systems (robot devices) used for manufacturing various articles (industrial products), for example. The configuration of the robot system (robot device), for example, the configuration of the robot arm, is arbitrary, and the inspection method of the present invention can be implemented in any robot system (robot device) having a joint that connects two or more links. . By inspecting the joints of a robot system using the inspection method according to the present invention, it is possible to reliably inspect and confirm the state of the transmission of the joint (presence or absence of failure or damage), and the joint (transmission) can be properly inspected. state can be maintained. Therefore, the robot system can be used to manufacture the target article with high accuracy and high yield.

Further, the method of inspecting the robot device shown in the above embodiment can be considered more generally as a method of inspecting a rotary drive device comprising a rotary drive source (motor) and a transmission. In that case, the inspection method of the rotary drive device of the present invention exemplified in the above embodiment can be implemented in various mechanical devices as a method of inspecting the rotary drive device comprising various rotary drive sources (motors) and transmissions. can.

The present invention supplies a program that implements one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and one or more processors in the computer of the system or device read and execute the program. processing is also feasible. It can also be implemented by a circuit (for example, ASIC) that implements one or more functions.

1 Servo motor (motor)
2 rotating shaft 11 speed reducer (transmission)
16 output side encoder (output side angle detection means)
100 robot device 111 to 116 joints 200 control device 201 CPU (arithmetic unit)
204 HDD (storage unit)
300 teaching pendant 402 actual output angle calculation unit 403 angle information storage unit 404 resonance amplitude calculation unit 405 reference value storage unit 406 joint state determination unit 407 motion storage unit for inspection 408 motion generation unit for inspection s401 output side encoder pulse s402 output side angle Information s403 Accumulated angle information s404 Decision value A
s405 Reference value for judgment s407 Operation information for inspection 500 Robot system W Work

Claims (29)

In a control method for a robot having a plurality of joints and controlled based on a predetermined trajectory for executing normal motion ,
operating the predetermined joint of the plurality of joints at a driving speed at which the predetermined joint vibrates naturally, operating the robot so that the robot maintains the predetermined trajectory, and increasing the amplitude of the natural vibration of the predetermined joint; and get
obtaining the state of the predetermined joint based on the amplitude;
A control method characterized by: In the control method according to claim 1,
The predetermined joint is provided with a drive source and a reduction gear that reduces the output from the drive source,
obtaining a state of the speed reducer based on the amplitude;
A control method characterized by: In the control method according to claim 1 or 2,
obtaining the state by comparing the amplitude with a reference value;
A control method characterized by: In the control method according to claim 1 or 2,
Obtaining a rate of change by comparing the amplitude with an amplitude at a past timing different from the timing at which the amplitude was obtained, and obtaining the state based on the rate of change;
A control method characterized by: In the control method according to claim 2,
Diagnosing whether the speed reducer is out of order based on the amplitude;
3. The control method according to claim 2, characterized by: In the control method according to claim 2,
The drive source is a motor that rotates,
A control method characterized by: In the control method according to any one of claims 1 to 6,
The driving speed corresponds to a natural frequency of the natural vibration that changes according to a change in posture of the robot.
A control method characterized by: In the control method according to claim 7,
setting the driving speed to be a constant multiple of the natural frequency of the predetermined joint;
The inspection method according to claim 7, characterized in that: In the control method according to any one of claims 1 to 7,
changing the driving speed within a range including a driving speed at which resonance occurs as the natural vibration at the predetermined joint;
A control method characterized by: In the control method according to claim 9,
The range includes a drive speed that is ½ times the resonance frequency at which the resonance occurs.
A control method characterized by: In the control method according to any one of claims 1 to 10,
A command value for the predetermined joint in the operation for obtaining the state is set so that the amount of driving the predetermined joint in the predetermined trajectory matches the amount of driving the predetermined joint in the operation for obtaining the state. change over time,
A control method characterized by: In the control method according to claim 11,
extending the command value of the predetermined joint in the time direction;
A control method characterized by: In the control method according to claim 11 or 12,
setting command values for the plurality of joints based on the command values for the predetermined joints and the predetermined trajectory;
A control method characterized by: In the control method according to claim 13,
The angle information corresponding to the command value of the predetermined joint in the predetermined trajectory and the angle information of the plurality of joints corresponding to the angle information corresponding to the command value of the predetermined joint also in the operation for acquiring the state. setting command values for the plurality of joints to
A control method characterized by: In the control method according to claim 2,
The predetermined joint is provided with a first sensor that measures the rotation angle of the rotation shaft on the output side of the speed reducer and a second sensor that measures the rotation angle of the rotation shaft on the input side of the speed reducer,
Acquiring the amplitude based on a difference in angle information output from the first sensor and the second sensor;
A control method characterized by: In the control method according to any one of claims 1 to 15,
notifying a user of said state;
A control method characterized by: 17. The control method of claim 16,
The notification is performed by at least one of display by display means and audio output by audio output means.
A control method characterized by: In the control method according to claim 16 or 17,
outputting a trigger to cause the user to acquire the state;
A control method characterized by: In the control method according to any one of claims 16 to 18,
Allowing the user to specify the order of the joints for which the states are acquired among the plurality of joints;
A control method characterized by: In the control method according to any one of claims 1 to 19,
the predetermined trajectory of the normal action is set according to the work to be executed by the robot;
A control method characterized by: A control method according to claim 20, wherein
The work is work for causing the robot to perform production,
A control method characterized by: In the control method according to claim 2,
When the robot is operated to maintain the predetermined trajectory, the input shaft of the speed reducer at the predetermined joint rotates three times or more.
A control method characterized by : In the control method according to claim 15,
performing FFT processing by dividing the angle information output from the second sensor into predetermined sections;
A control method characterized by : 24. The control method of claim 23,
The predetermined interval is a time interval of 100 msec,
A control method characterized by : In the control method according to claim 23 or 24,
A shift width is set for the predetermined section,
A control method characterized by : A program for causing a computer to execute the control method according to any one of claims 1 to 25 . 27. A computer-readable recording medium storing the control program according to claim 26 . In a robot system comprising a robot having a plurality of joints and controlled based on a predetermined trajectory for executing normal motions, and a control device ,
The control device
operating the predetermined joint of the plurality of joints at a driving speed at which the predetermined joint vibrates naturally, operating the robot so that the robot maintains the predetermined trajectory, and increasing the amplitude of the natural vibration of the predetermined joint; and get
obtaining the state of the predetermined joint based on the amplitude;
A robot system characterized by: 29. A method of manufacturing an article, comprising manufacturing an article using the robot system according to claim 28 .

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