JPH11202914A - Industrial robot and its fault detecting method, and recording medium where fault detecting program for industrial robot is recorded - Google Patents

Abstract

PROBLEM TO BE SOLVED: To take a diagnosis at any time even while a production line is in operation. SOLUTION: Data of respective axes (i) constituting a robot mechanism part are inputted from a servo system which controls a servo motor (step 1). After load torque To is calculated from mass point models for the robot itself and a load and the data of the respective axes (i) in consideration of interference of other axes, the power Wo of the load side which is the product of the load torque To and an angular velocity ωi is calculated (steps 4, 5). The data of the driving current Ii of the servo motor which drives the respective axes is inputted from the servo system and multiplied by the corresponding torque constant ki of the servo motor to calculate driving torque Ti and then the power Wi of the driving side which is the product of the driving torque Ti and angular velocity ωi is calculated (steps 2, 3). The ratio (Wi /Wo ) is calculated from the power Wo of the load side and the power Wi of the driving side and compared with a previously set decision value to decide whether or not the robot mechanism part has deteriorated (steps 6, 7).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can detect the presence or absence of a failure in a robot mechanism of an industrial robot driven by a servomotor during the operation of a production line without depending on the contents of the work. The present invention relates to an industrial robot, a failure detection method thereof, and a recording medium on which a failure detection program is recorded.

[0002]

2. Description of the Related Art In an industrial robot, the gears and the like constituting a driving force transmission system of a robot mechanism mainly including an arm and a driving motor thereof wear due to long-term use, thereby reducing the operation and control accuracy. It will have adverse effects. In general, such phenomena cannot be easily predicted from the outside, and tend to be left unattended until adverse effects appear. There was often.

In order to deal with this, for example, Japanese Patent Application Laid-Open
In -123105, when the robot is in a normal state,
For example, at the time of new introduction of the robot body or at the end of regular maintenance, the robot is actually operated according to a preset reference operation pattern, the operation data at this time is measured in advance as reference data, and this reference data is It is recorded in the storage device of the control device. Then, after a predetermined operation time has elapsed, the robot is actually operated again in the same manner as the reference operation pattern, and the operation data at this time is measured. And the difference is diagnosed based on the difference. As this operation data,
According to -123105, servo control deviation (deviation) is used, so it is not necessary to provide a dedicated sensor for diagnosing the presence or absence of a failure. In addition, the arm and its drive motor, reduction gear, etc. are mainly used. It is said that there is an advantage that it is possible to make a comprehensive diagnosis of the robot mechanism that performs and the servo control system that controls the robot mechanism.

[0004]

However, Japanese Patent Application Laid-Open Publication No.
In the method of 3-123105, it is necessary to measure the operation data in the normal state of the robot for each individual robot as reference data and store the reference data. Since the robot must be operated in a pattern, there is a problem that diagnosis cannot be performed while the production line is operating.
Further, there is a problem that it is difficult to improve the diagnosis accuracy for a failure that is specialized in an actual operation pattern during the operation of the production line.

SUMMARY OF THE INVENTION The present invention has been made to solve these problems of the prior art, and is intended to solve the problem of a failure of a robot mechanism of an industrial robot driven by a servomotor during operation of a production line. Without the need to previously measure the operation data in the operation pattern in the normal state of the robot as reference data, and to perform the diagnosis at any time even during the operation of the production line. Provided is an industrial robot, a method for detecting a failure thereof, and a recording medium on which a failure detection program is recorded so that a highly accurate diagnosis can be performed even for a failure specialized in an actual operation pattern when a line is operated. The purpose is to:

[0006]

In order to achieve the above object, the present invention provides a robot arm, a servomotor for driving the robot arm via a speed reducer, and an encoder for detecting the position of the servomotor. In an industrial robot having a robot mechanism, a command position calculator for outputting a command angle θ _d of each drive shaft constituting the robot mechanism, a command angle θ _d and an actual angle θ of the servo motor obtained by the encoder a position loop for creating and outputting a position command based on _i, and speed loop to create a speed command output on the basis of the actual angular velocity omega _i obtained from the position command and the actual angle theta _i, the speed command and the servomotor a current loop that creates and outputs a current command based on the drive current I _i, based on the actual angle theta _i and the drive current I _i, the servo control system and the robot mechanism portion An industrial robot characterized by having a failure detection unit for determining the presence or absence of a failure is provided (claim 1).

[0007] Specifically, in the failure detection unit,
Work on the input side and output side of the robot mechanism calculated based on the actual angle θ _i and the drive current I _i, and the actual angular velocity ω _i and the actual angular acceleration α _i obtained by differentiating the actual angle θ _i The presence or absence of a failure in the robot mechanism is determined from the rate (claim 2).

[0008] In failure detection method performed in the fault detection section, the work of the drive side of the drive shaft on the basis of the drive current I _i and the actual angle theta _i of the servo motor for driving the drive shaft constituting the robot mechanism calculating the rate W _i, to calculate the work rate W _o of the load side of each drive shaft based on the actual angle theta _i and motion equation relating mass model of the robot mechanical unit, of the load-side work rate W _o and drive side Ratio (W _o / W) of the power of the robot mechanism of each drive shaft obtained from the power W _{i of
i} ) or the difference (W _o −W _i ) is compared with a predetermined determination value to determine whether there is a failure in the robot mechanism (claim 3).

More specifically, the processing procedure is as follows.
In a first process step, the drive current I _i of the servo motor for driving the drive shaft constituting the robot mechanism, actual angle theta _i, real angular velocity omega _i as a differential value of the actual angle theta _i, and the actual angular velocity omega _i take in the actual angular acceleration α _i as a differential value of the. In a second process step, to calculate the drive torque T _i of the respective drive shaft by multiplying the torque constant k _i of the servo motor to the drive current I _i taken in the first process step. In the third processing step, the power on the driving side of each drive shaft is the product of the driving torque T _i calculated in the second processing step and the actual angular velocity ω _i taken in the first processing step. to calculate the W _i.

In a fourth processing step, each of the equations of motion relating to the mass model of the robot mechanism and the actual angle θ _i , the actual angular velocity ω _i , and the actual angular acceleration α _i fetched in the first processing step are used. calculating the load torque T _o of the drive shaft. In the fifth process step, the load side of the work rate of each drive shaft is the product of the fourth processing actual angular velocity omega _i taken by the calculated and the load torque T _o the first processing step at step Calculate W _o . In the sixth processing step,
Load-side power W _o calculated in the fifth processing step
And the power W on the drive side calculated in the third processing step
By and _i, calculating the ratio of the work rate of the robot mechanism of the drive shaft (W _o / W _i). In the seventh processing step,
The power ratio calculated in the sixth processing step (W _o /
By comparing W _i ) with a predetermined judgment value,
It is determined whether a failure has occurred in the robot mechanism (claim 4).

[0011] In the sixth and seventh processing steps, as described in claim 4, the work of the robot mechanism portion of the drive shaft than the work rate W _i on the load side of the work rate W _o and drive side Instead of calculating the power ratio (W _o / W _i ) and comparing this with a predetermined judgment value, each drive shaft is calculated from the power W _o on the load side and the power W _i on the drive side. the difference in the work rate of the robot mechanism (W _o -W _i) is calculated, and may be compared with preset determination value this (claim 5).

The above-described failure detection method is realized by being incorporated in a robot control program as a failure detection program, and the failure detection program is provided by being recorded on a recording medium. That is, a procedure for calculating the power W _i on the drive side of each drive shaft based on the drive current I _i and the actual angle θ _i of the servo motor that drives each drive shaft constituting the robot mechanism, A procedure for calculating the load-side power W _o of each drive shaft based on the equation of motion for the mass model and the actual angle θ _i , and each drive obtained from the load-side power W _o and the drive-side power W _i a procedure for determining the presence or absence of a failure of the robot mechanism by comparing the preset determination value the ratio of work rate of the robot mechanism (W _o / W _i) or a difference (W _o -W _i) of the shaft ,
The present invention is provided as a recording medium on which a failure detection program for an industrial robot is recorded.

The operation of the above configuration will be described below.
Generally, the actual operation performance to the operation command to the drive shaft is referred to as followability. Particularly, the quality of the followability during acceleration / deceleration greatly affects the performance of the robot mechanism. Here, the robot mechanism section includes a robot arm, a servomotor 25 for driving the robot arm, and a speed reducer interposed between the robot arm and the servomotor 25 in the block diagram of the present invention shown in FIG. Have been. As the deterioration of the robot mechanism 28 progresses due to aging, the gears and the like that constitute the driving force transmission system are worn, thereby deteriorating the responsiveness particularly during acceleration and deceleration. When the followability during acceleration / deceleration deteriorates, the power W _i on the input side (input side of the servo motor 25) of the robot mechanism 28, ie, the drive side, and the output side (reduction gear side) of the robot mechanism 28, ie, the load side The difference between the power and the work rate _Wo increases. In general, during acceleration, the power W _i on the drive side appears larger than the power W _o on the load side, and conversely, during deceleration, the power W _o on the load side becomes higher than the power W _i on the drive side. Appears to grow larger.

In the present invention, by utilizing the above-described characteristics, a failure detection unit 27 is provided in the robot control device 30 shown in FIG. 1, and the failure detection unit 27 fetches data necessary for detecting a failure. , The power W _i on the input side, ie, the drive side, of the robot mechanism 28 and the robot mechanism 28
Presence of a failure of the robot mechanism 28 is to be determined by comparing the output-side or load side of the work rate W _o. Specifically, the power ratio or difference is compared with a predetermined determination value, and if not within the allowable range, it is determined that a failure has occurred.

The power W on the drive side in the failure detection unit 27
As a method of calculating the _i and the load side of the work rate W _o is work rate W _i of the drive side, provided shipped or features on the drive current I _i, and the servo motor 25 to be supplied to the servo motor 25 encoder 26 calculated from the actual angular velocity omega _i as a differential value of the actual position of the drive shaft detected by (position detector) (actual angle theta _i), also of the load-side work rate W _o
It is the actual angle theta _i described above, the actual angular velocity omega _i, and the actual angular acceleration alpha _i as a differential value of the actual angular velocity omega _i, is calculated based on the equation of motion related to the mass point model of the robot mechanism section 28.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram including a robot mechanism section 28 of the present invention. In the figure, reference numeral 25 denotes a servomotor for operating each drive shaft constituting the robot mechanism section, and reference numeral 26 denotes the position of the servomotor 25, that is, the actual drive axis. An encoder for detecting the angle θ _i , a command position calculator 21 for outputting a command angle θ _d of each drive shaft, and a controller 22 for generating and outputting a position command based on the command angle θ _d and the actual angle θ _i of the drive shaft. A position loop 23 is a position command and an actual angle θ.
a speed loop for generating and outputting a speed command based on the actual angular speed ω _i obtained by differentiating _i with a Laplace operator S as a differentiator; A current loop 27 for generating and outputting a current command based on the drive current _Ii, and a failure detection unit 27 for detecting the presence or absence of a failure in the robot mechanism 28 and the servo control system 29.

Since the failure detector 27 must constantly monitor the robot mechanism 28 and the servo control system 29 for failures, data necessary for failure detection, that is, the actual angle θ _i and the actual angular velocity ω _i. , Real angular acceleration α _i , and drive current I _i need to be captured in real time. Of these data, the actual angle θ _i is
From 6, the drive current _Ii is taken from the current detector. Further, each data of the actual angular velocity ω _i and the actual angular acceleration α _i is obtained by differentiating the actual angle θ _i , but this differentiation processing may be performed in the failure detection unit 27 or shown in FIG. The differentiator S outside the failure detection unit 27
May be performed.

FIG. 2 shows the fault detector 2 shown in FIG.
7 is a flowchart illustrating an outline of a process performed in step 7 to determine whether a failure has occurred in the robot mechanism unit 28.
In step 61, the power W on the drive side of each drive shaft is determined based on the drive current I _i of the servo motor 25 that drives each drive shaft constituting the robot mechanism 28 and the actual angle θ _i detected by the encoder 26. Calculate _i . Step 6
In 2, calculates the load side of the work rate W _o of each drive shaft based on the actual angle theta _i and motion equation relating mass point model of the robot mechanism section 28. In step 64, the work rate of the calculated load in step 62 W _o and Step 61
(W _o / W _i ) The ratio of the power of the robot mechanism of each drive shaft obtained from the power W _i on the drive side calculated in (1).
Alternatively, the presence or absence of a failure of the robot mechanism 28 is determined by comparing the difference (W _o −W _i ) with a predetermined determination value. Steps 61 and 62 can be performed in parallel.

FIG. 3 is a flowchart more specifically showing the outline of the processing shown in FIG. Step 1 (first
In processing step), captures the driving current I _i of the drive shafts, actual angle theta _i, real angular velocity omega _i, and the actual angular acceleration alpha _i. The drive current I _i is controlled by the current loop 24 and the servo motor 25.
It is taken in from a current detector provided on the transmission path between. The actual angle θ _i is fetched from an encoder 26 attached to or attached to the servomotor 25. The actual angular velocity ω _i is obtained as a value obtained by differentiating the actual angle θ _i detected by the encoder 26 with the differentiator S, and further obtained by differentiating the actual angular velocity ω _i with the differentiator S. The value is taken as the actual angular acceleration α _i . However,
The actual angular velocity ω _i and the actual angular acceleration α _i may be calculated by differentiating the acquired actual angle θ _i in the failure detection unit 27.

In step 2 (second processing step),
The driving current I _i taken in step 1 to calculate the drive torque T _i of the respective drive shaft by multiplying the torque constant k _i of the servo motor. In step 3 (third processing step), the power W _i on the drive side of each drive shaft is the product of the drive torque T _i calculated in step 2 and the actual angular velocity ω _i taken in step 1. Is calculated.

In step 4 (fourth processing step),
Calculating a motion equation relating to the mass point model of the robot mechanism section 28, the actual angle theta _i taken in step 1, the actual angular velocity omega _i, and the load torque T _o of the drive shaft by the actual angular acceleration alpha _i. Here will be described the process of calculating the load torque T _o. FIG. 4 shows an example of a mass model in a vertical articulated robot having a six-axis configuration. In the figure, reference numeral 41 denotes a mass point model of the load, and reference numerals 42 to 46 denote mass models of the second to sixth drive shafts. In addition, 51 to 56 are the first to
6 shows each drive shaft. With respect to this mass model, the torque acting on the load side of each drive shaft, that is, the load torque, is calculated by obtaining each term of the equation of motion represented by the equation (1).

[0022]

(Equation 1)

In the equation (1), the left side is a torque matrix representing the load torque acting on each axis. The first term on the right side represents torque due to inertial force, the second term represents torque due to centrifugal force and Coriolis force, and the third term represents torque due to unbalance force. Expression (1) is a general equation of motion related to the mass model of the robot, and is not an equation unique to the present invention.

In step 5 (fifth processing step),
Step 4 load torque calculated at T _o and Step 1
Calculating a work rate W _o of the load side of the drive shaft is the product of the actual angular velocity omega _i taken in. Steps 2-3
And the processing of steps 4 and 5 can be performed in parallel.

In step 6 (sixth processing step),
Based on the load-side power W _o calculated in step 5 and the drive-side power W _i calculated in step 3, the ratio of the power of the robot mechanism of each drive shaft (W _o / W _i). Or W _i / W _o ). In step 7 (seventh processing step), the ratio of the power calculated in step 6 (W
_o / W _i or W _i / W _o ) is compared with a predetermined determination value to determine whether the robot mechanism 28 has a failure. More specifically, the allowable value is β, 1 + β is the upper limit of the determination value, and 1-β is the lower limit, so that the ratio of the power of the robot mechanism unit is in the range between the upper limit and the lower limit. If it is within, it is determined that there is no failure in the robot mechanism 28.

[0026] In the step 6-7, and calculates the difference between the load side of the work rate W _o and drive side work rate than the work rate W _i of (W _o -W _i or W _i -W _o), this The difference in the power may be compared with a preset determination value. Specifically, + β is set as the upper limit of the determination value and −β is set as the lower limit. If the difference in the power is within the range between the upper limit and the lower limit, there is no failure in the robot mechanism unit 28. Is determined.

While the method for detecting a failure of an industrial robot according to one embodiment of the present invention has been described above, the processing relating to the above-described failure detection is performed in real time. Generally, it is performed in units of tens of milliseconds), so that if a failure occurs, it is immediately determined and detected. After the failure is detected, a process of stopping the operation of the robot is performed in the robot control device 30, and the failed drive axis, the failure factor, and the like are displayed on a monitor (not shown) connected to the robot control device 30. Will be.

Incidentally, such a failure detection method is realized by being incorporated in a robot control program for controlling the operation of the robot body as a failure detection program, and the failure detection program is provided by being recorded on a recording medium. That is, although not shown, the robot control device 30 shown in FIG. 1 includes a storage unit for a robot control program, a calculation unit, an interface unit, and the like. For example, a failure created by an external program creation device (not shown) The detection program is input to the storage unit of the robot control program via the interface unit, and the arithmetic unit performs a failure detection process according to the operation of the robot.

Therefore, if a flexible disk (floppy disk), which is generally used as a recording medium, is used, the failure detection program is recorded on the flexible disk, and the program transfer between the program creating device and the robot controller 30 is performed. It can be used as a means, and can also be used as a backup means for a failure detection program recorded in a storage unit of a robot control program in the robot control device 30. Further, if the storage unit of the robot control program is constituted by a ROM (Read Only Memory) or a hard disk, these can also be a recording medium in the present invention. Needless to say, other recording media such as an MO (magneto-optical disk), CD-ROM, CD-R, and magnetic tape can be used as the program transfer means and backup means. If the failure detection program is downloaded to the user's personal computer from the provider's server by communication means such as the Internet, the provider's server and the RAM or hard disk of the user's personal computer also correspond to the recording medium referred to herein. I do.

[0030]

According to the present invention, there is provided an industrial robot having a robot mechanism comprising a robot arm, a servomotor for driving the robot arm via a speed reducer, and an encoder for detecting the position of the servomotor. Based on the actual angle θ _i as position data of the servo motor driving each drive shaft constituting the unit and the drive current I _i of the servo motor, the power W _i on the drive side, which is the input side of the robot mechanism, and calculating the load side of the work rate W _o is the output side of the robot mechanism, and to determine the presence or absence of a failure of the robot mechanism than the ratio or difference of work rate of the load side and the driving side. Therefore, by using the power that changes every moment according to the actual operation pattern for the determination, the operation data in the reference operation pattern in the normal state of the robot is not measured in advance as the reference data, and the production line is not used. Diagnosis can be performed at any time during the operation of the robot, and a failure of the robot mechanism can be diagnosed even for a device that is specialized in an actual operation pattern during the operation of the production line.

The data used in the failure detection method of the present invention, that is, the actual angle θ _i and the drive current I _i are obtained by acquiring the data using an encoder or a current detector attached to the servo motor provided in the existing robot system. Because
The only hardware that the present invention adds to the prior art is the failure detection unit in the robot controller. Also,
As software, it is only necessary to add the failure detection program of the present invention to the conventional robot control program. For this reason, there is an advantage that the cost increase at the time of new production of the robot is slight, and even when the technology of the present invention is added to a conventional robot, it can be dealt with with only a slight modification.

[Brief description of the drawings]

FIG. 1 is a block diagram including a robot mechanism section 28 according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating an outline of a diagnosis procedure of the robot mechanism unit 28 according to the embodiment of the present invention.

FIG. 3 is a flowchart showing a specific example of a diagnosis procedure of the robot mechanism unit 28 according to the embodiment of the present invention.

FIG. 4 is a diagram illustrating an example of a mass model in a vertical articulated robot having a six-axis configuration.

[Explanation of symbols]

 21 Command Position Calculator 22 Position Loop 23 Speed Loop 24 Current Loop 25 Servo Motor 26 Encoder 27 Failure Detector 28 Robot Mechanism 29 Servo Control System 30 Robot Controller

Claims (6)

[Claims] An industrial robot having a robot arm comprising a robot arm, a servomotor for driving the robot arm via a speed reducer, and an encoder for detecting the position of the servomotor, wherein each of the robot mechanisms comprises a command position calculation unit for outputting a command angle of the drive shaft, and the position loop creates and outputs the position command based on the actual angle theta _i of the servo motor obtained by finger-old angle and said encoder, said position command and the Actual angular velocity ω obtained from actual angle θ _i
a speed loop to create a speed command output based on _i, a current loop for creating and outputting a current command based on the drive current I _i in the velocity command and the servomotor, the actual angle theta _i, and the drive current I An industrial robot, comprising: a failure detection unit that determines presence or absence of a failure in the robot mechanism based on _i . 2. The failure detector calculates the actual angle θ _i and the driving current I _i based on the actual angular velocity ω _i and the actual angular acceleration α _i obtained by differentiating the actual angle θ _i. 2. The industrial robot according to claim 1, wherein the presence or absence of a failure in the robot mechanism is determined based on the power on the input side and the power on the output side of the robot mechanism. 3. A failure detection method for an industrial robot comprising a robot arm, a servo motor for driving the robot arm via a speed reducer, and an encoder for detecting the position of the servo motor. The power W _i on the drive side of each drive shaft is calculated based on the drive current I _i of the servo motor that drives each drive shaft and the actual angle θ _i , and the equations of motion for the mass model of the robot mechanism and The load-side power W _o of each drive shaft is calculated based on the actual angle θ _i , and the work of the robot mechanism of each drive shaft obtained from the load-side power W _o and the drive-side power W _i is calculated. Rate ratio (W _o
/ W _i ) or the difference (W _o −W _i ) is compared with a predetermined determination value to determine whether or not the robot mechanism has a failure. Method. 4. A failure detection method for an industrial robot having a robot arm comprising a robot arm, a servomotor for driving the robot arm via a speed reducer, and an encoder for detecting the position of the servomotor. drive current I _i of the servo motor for driving the drive shaft constituting the actual angle theta _i, real corner as a differential value of the actual angular velocity omega _i, and said actual angular velocity omega _i as a differential value of said actual angle theta _i A first processing step of taking in the acceleration α _i , a second processing step of calculating a driving torque T _i of each drive shaft by multiplying the driving current I _i by a torque constant k _i of a servomotor, A third processing step of calculating a power W _i on the drive side of each drive shaft, which is a product of T _i and the actual angular velocity ω _i , a motion equation relating to a mass model of the robot mechanism; Actual angle theta _i, the product of the fourth processing step of calculating the load torque T _o of the drive shaft by the actual angular velocity omega _i, and the actual angular acceleration alpha _i, and the load torque T _o the the actual angular velocity omega _i work fifth processing step and, robot mechanism of the drive shaft than the work rate W _i of work rate of the load-side W _o and the driving side for calculating the load side of the work rate W _o of the drive shaft is Rate ratio (W _o / W _i )
And a sixth step of determining whether or not the robot mechanism has a failure by comparing the ratio of the power of the robot mechanism (W _o / W _i ) with a predetermined determination value. 7. A method for detecting a failure of an industrial robot, comprising: 5. The claimed sixth and seventh processing step according to claim 4, the difference between the load side of the work rate W _o and work rate of the robot mechanism of the drive shaft than the work rate W _i of the drive-side (W _o -W _i) and a sixth processing step of calculating, the robot mechanism section by comparing a preset determination value difference between the work rate (W _o -W _i) of the robot mechanism The method for detecting a failure of an industrial robot according to claim 4, further comprising: a seventh processing step of determining whether there is a failure. 6. A control program for detecting a failure of an industrial robot including a robot arm, a servomotor for driving the robot arm via a speed reducer, and an encoder for detecting the position of the servomotor. A power W _i on the drive side of each drive shaft is calculated based on the drive current I _i and the actual angle θ _i of the servo motor that drives each drive shaft constituting the robot mechanism. procedures and the procedures for calculating the work rate W _o of the load side of each drive shaft based the equations of motion about the mass point model of the robot mechanical unit to the actual angle theta _i, the load side of the work rate W _o and drive side The ratio (W _{o) of the} power of the robot mechanism of each drive shaft obtained from the power W _i
/ W _i ) or a difference (W _o −W _i ) with a predetermined determination value to determine whether or not the robot mechanism has a failure. A recording medium on which a failure detection program is recorded.