JPH04235610A - Abnormality detector for industrial robot - Google Patents

Abstract

PURPOSE:To obtain an abnormality detector for industrial robot by detecting the abnormality of an absolute position detector means et all times and in reel time while the robot is working and suppressing surely and always the abnormality that is caused by the position control of the robot. CONSTITUTION:In a step 12 the value detected by an absolute position detector means like an absolute encoder, etc., is periodically held while an industrial robot is working. In a step 15 the held detection value is compared with the value detected by a relative position detector means like an incremental encoder, etc. Then in a step 20 the abnormality is decided based on the integrated result of the generating frequency of difference produced et a level higher then the prescribed value between both values compared with each other.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting an abnormality in position detection means necessary for controlling a robot.

0002

[Prior Art] Controlling a robot requires continuous detection of the position (posture) of the robot body (manipulator). For this purpose, a position detector is usually provided for each movable part of the manipulator to collect position data. I'm starting to get it.

[0003] Conventionally, therefore, robot devices have been known that detect the position of a robot using an absolute position detector called an absolute encoder and a relative position detector such as an incremental encoder consisting of a pulse generator. However, in this case, the absolute encoder is used to detect the current value of the robot when the robot device is powered on, and thereafter, while the robot is moving, the incremental encoder is used to capture the robot position and It was customary to proceed with control.

[0004] This is because, in general, it is easier to obtain higher resolution with an incremental encoder than with an absolute encoder, and in addition, with an absolute encoder, it takes longer to read the current value of the position detection data than with an incremental encoder. This is because it takes time, and on the other hand, once the power is turned off and then turned on again, the incremental encoder cannot know the current position of the robot.

By the way, in the above example, the absolute encoder is used only when the power of the robot device is turned on, so a robot control device that is designed to make efficient use of the encoder has been proposed. This can be found in Japanese Patent Application Laid-open No. 1-197813.

In other words, in the example of this publication, the detected value by the incremental encoder and the detected value by the absolute encoder are compared each time the robot stops moving, and when a discrepancy appears in the detected values, the absolute encoder at that time is compared. The value detected by the incremental encoder is set to be replaced with the value detected by the incremental encoder.This corrects the detected value of the incremental encoder that may be caused by noise, etc., and provides highly accurate position control at all times. That's how I do it.

[0007]

[Problems to be Solved by the Invention] The above-mentioned conventional technology does not take into consideration the case where an abnormality occurs in the absolute position detection means consisting of an absolute encoder, etc., and when an abnormality occurs, the In addition, since the detected value of the incremental encoder is set by the absolute position data from the absolute encoder where the abnormality occurred, an abnormality will occur in the robot's position control from now on, leading to the risk of a dangerous situation occurring. There was a problem.

The present invention provides an abnormality detection device for an industrial robot that can detect an abnormality in the absolute position detection means in real time during robot operation, and can always reliably suppress the occurrence of abnormality in the robot's position control. It is intended for the purpose of providing.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the present invention periodically detects a detected value by an absolute position detecting means such as an absolute encoder during robot operation.
It is equipped with a means that enables comparison with a value detected by a relative position detection means such as an incremental encoder, and a means for cumulatively counting the number of times a difference of more than a predetermined value appears in the comparison result of the detected value by this means. be.

0010

[Operation] The means for making the comparison described above compensates for the difference in detection time between the detected value by the absolute position detecting means, which takes a relatively long time to read, and the detected value by the relative position detecting means, which can be read out in a short time. The integrated counting means works to ensure that abnormalities can be detected, and works to suppress accidental false detections such as abnormalities in the data transmission system or abnormalities due to noise, so that abnormalities can always be detected reliably.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The abnormality detection device for industrial robots according to the present invention will be explained in detail below with reference to the illustrated embodiments. First, FIG. 2 is a configuration diagram when an embodiment of the present invention is applied to a welding robot device. In the figure, 1 is a robot main body (manipulator), which is an articulated robot with a 6-axis configuration. 2 is a robot control device, the details of which will be described later. 3
is a programming unit that is used when teaching robots. 4 is the playback console, which allows operations such as starting and stopping during automatic driving. 5 is a welding machine, which is mainly composed of a welding power supply section and an interface section; 6 is a welding wire; a wire feeder 7 sends the welding wire to a torch 8 attached to the wrist of the robot body 1; It is intended to be supplied.

FIG. 3 is a block diagram of the robot control device 2, which is roughly divided into three blocks. First, A is the main CPU section, which is mainly in charge of robot operation commands and control necessary for the man-machine interface. Next, B is a servo CPU section, which is mainly responsible for controlling the robot's motion. And C is a servo amplifier.

Further, D is a motor section representing motors M1 to M6 for driving each joint of the robot body 1, and E is a motor section representing incremental encoders IE1 to IE6 attached to the shafts of each joint driving motor M1 to M6. Represents the encoder section that includes. Next, AE1 to AE6 are absolute encoders, which are attached to the shafts of the respective joint drive motors M1 to M6 included in the motor section D.

[0014] First, the configuration of the main CPU section A will be explained. The CPU-A 30 performs management processing for the entire equipment. 31 is ROM-A, and when the power is turned on, the CP
A program describing the processing to be executed by the U-A 30 is stored. 32 is a RAM-A, into which various processing programs stored in the bubble memory 35 are loaded and executed by the CPU-A 30. 33 is a communication interface (I/F) which has a two-channel communication function, one for communicating with the programming unit 3 and the other for communicating with the playback console 4. Further, 34 is also a communication interface (I/F), which is used for communication with the welding machine 5.

36 is DPRAM (dual port RAM)
The main CPU section A and servo CPU section B are connected to this D.
Information is exchanged via PRAM36. In addition, 43
is a data bus that serves to connect each device in the main CPU section A.

[0016] Next, the servo CPU section B will be explained. This is for executing the instructions written into the DPRAM 36 by the main CPU section A. For this purpose, first,
A CPU-B37 is provided. And this CPU
-B37 executes all servo-related processing, and most of the main processing related to the present invention is processed by this CPU-B37. 38 is ROM-B, CPU-B37
It functions to store programs to be executed. 3
Reference numeral 9 denotes a RAM-B, which functions to store and hold the results of an operation during the execution of a program in the ROM-B 38 by the CPU-B 37.

[0017] 40 is a timer, and the CPU-B
Used to interrupt 37. In other words, the CPU-B 37 issues commands to the servo motor and executes the main processing of the present invention at fixed intervals determined by the timer 40. 41 is a D/A converter, and the CPU-
It functions to convert the digital current command value for each servo motor calculated by B37 into an analog value and supply it to the servo amplifier C. As a result, the output of this servo amplifier C drives each joint drive motor M1 to M6.
is driven, and the robot 1 is operated.

A counter section 42 includes six independent counters, each of which corresponds to one of the incremental encoders IE1 to IE6 and is incremented by pulses therefrom. Therefore, the CPU-B 37 can know the current position of the robot body 1 detected by the incremental encoders IE1 to IE6 by reading the count values of the respective counters. Note that 44 is a data bus that serves to connect each device in the servo CPU section B.

By the way, as mentioned above, absolute encoders AE1 to AE6 are attached to the shafts of the joint drive motors M1 to M6 of the motor section D, and as a result,
The CPU-B 37 can know, via the D/A converter 41, the current position of the robot body 1 detected by these absolute encoders AE1 to AE6.

Next, the operation of this embodiment will be explained with reference to the flowchart in FIG. 1. As mentioned above, the process shown in FIG. B37 is executed sequentially at a fixed time period of, for example, 300 msec.

[0021] Absolute encoders AE1 to AE6
The comparison between the current position data (ABS data) detected by the robot body 1 and the current position data (iNC data) detected by the incremental encoders IE1 to IE6 is
must be executed for each axis, so first, in step 10, the axis number is initialized to 1. In this example, the initial value is set to 1, but any number i may be used as the initial value if it does not exceed the number of axes (6 in this case), that is, in this case, if i≦6. good.

Next, in step 11, a counter for counting the occurrence of an abnormality in each encoder, that is, an abnormality counter is cleared. Note that this abnormality counter is
It may be configured with a soft counter using B39.

[0023] Next, in step 12, the above-mentioned ABS
data, i.e. absolute encoders AE1 to A
Necessary to read the current position data detected by E6,
Executes latch command output processing. In response to this latch command, the servo amplifier C starts a process of sequentially reading ABS data from the absolute encoders AE1 to AE6 and storing it in a predetermined buffer.

By the way, it takes a relatively long time to store data into the buffer using this latch command.
Without waiting for the end of this process, the process proceeds to the next step 13, where the above-described iNC data, that is, the current position data detected by the incremental encoders IE1 to IE6, is latched and read. That is, in this step 13, the count value of the counter corresponding to the axis number in the counter section 42 is taken out and set in the RAM-B39.

[0025] By the time the process in step 13 is finished, the ABS data has already been stored in the buffer, so in the following step 14, this ABS data is read out from the buffer and stored in the RAM. -Write to B39. Therefore, by the processing in steps 10 to 14 so far, two types of data necessary for comparison, namely A
BS data and iNC data are now prepared.

Therefore, in the next step 15, a comparison and determination process of these data is executed. The conditions for this comparison and determination are as follows. P≦R

... ... (1)
P: Absolute value of (ABS data) - (iNC data) R: Judgment value Further, the judgment value R is determined as follows. P=(Ki-Ka)×R
max×t/60 …… ……
(2) Ki: Incremental encoder IE1 to IE6

Resolution [ppr] K
a: Absolute encoders AE1 to AE6


Resolution [ppr]
Rmax: Maximum rotation speed [rpm] of joint drive motors M1 to M6 t:
Comparison period [sec] Note that this comparison period t is the execution period of the process in FIG. 1, and in the case of the above example, 30
It becomes 0mS.

In this way, if the comparison judgment detection based on equation (1) in step 15 is YES (affirmative), that is, if the absolute value P of the difference between the ABS data and the iNC data is less than or equal to the judgment value R, the encoder It is determined that there is no abnormality, and in this case, the process proceeds to the next step 36.First, 1 is added to the axis number here so that the process moves to abnormality detection for the next axis.Subsequently, in step 17, the axis number is As a result of adding 1 to the number, it is determined whether this axis number exceeds the number of axes that the robot body 1 has, that is, 6 in this example, and the result is NO (negative), that is, 6 or less. When , the process returns to step 11 and the same process is executed for the next axis.On the other hand, when the result is YES, step 18 is executed to return the axis number to 1, and then the process returns to step 11. .

[0028] When the comparison judgment detection based on equation (1) in step 15 is NO, the corresponding axis numbers of the incremental encoders IE1 to IE6 or the absolute encoders AE1 to AE6 are selected. This indicates that some kind of abnormality has occurred, so in this case, proceed to step 19. First, in step 19, the abnormality counter is incremented.
That is, 1 is added to the count value at that time, and then in step 20, the value of the abnormality counter to which this 1 has been added is compared with a predetermined determination value n, and the result is YES, that is, the value of the abnormality counter is determined. If the value n has been reached, proceed to the next step 21 and execute the robot emergency stop process, but if this is not the case and the result is NO, that is, the numerical value of the abnormality counter has not reached the judgment value n. In this case, it cannot be determined that an abnormality has occurred in the incremental encoders IE1 to IE6 or the absolute encoders AE1 to AE6 corresponding to the axis number at this time, and the process returns to step 12 and the error is determined again for the same axis number. This allows the process to be repeated.

Therefore, according to this embodiment, while the robot is operating, the incremental encoders IE1 to IE6
The data of the absolute encoders AE1 to AE6 are constantly and repeatedly monitored at fairly short intervals, and the cumulative number of times these discrepancies occur is checked for each axis. Abnormalities can be detected based on the results. In some cases, it is possible to reliably bring the robot to an emergency stop, and it is possible to reliably prevent the robot from running out of control or positional deviation due to encoder abnormalities.

By the way, the emergency stop process in step 21 of FIG. 1 is not limited to the above-described robot emergency stop process, but may also include processes such as displaying an abnormality occurrence on a suitable display device or displaying an abnormality using an alarm. It's okay,
By doing so, it is possible to facilitate a more appropriate response when the robot is stopped.

Further, in the above embodiment, an absolute encoder is used as the absolute position detection means of the robot, but the present invention is not limited to this, but a potentiometer type ( It may also be implemented by a position detector (variable resistor type).

[0032]

According to the present invention, the absolute position detecting means can be used efficiently in a robot device that uses both the absolute position detecting means and the relative position detecting means to detect the position of the robot body, and the data transmission system By suppressing accidental false detections such as abnormalities caused by noise or noise, the reliability of abnormality detection is improved, and unnecessary robot stoppages due to false detections are prevented. can be expected to significantly improve operating rates without compromising safety.

[Brief explanation of the drawing]

FIG. 1 is a flowchart illustrating the operation of an embodiment of an abnormality detection device for an industrial robot according to the present invention.

FIG. 2 is a configuration diagram of a robot device to which an embodiment of the abnormality detection device for an industrial robot according to the present invention is applied.

FIG. 3 is a block diagram of a control system in an embodiment of the abnormality detection device for an industrial robot according to the present invention.

[Explanation of symbols]

1 Robot body 2 Robot control device 3 Programming unit 4 Playback console 5 Welding machine 6 Welding wire 7 Wire feeding device 8 Torch A Main CPU section B Servo CPU section C Servo amplifier D Motor part M1~M6　Joint drive motor

Claims (4)

[Claims] Claim 1: In an industrial robot that detects the posture of a robot body by using both an absolute position detecting means and a relative position detecting means, the absolute position detecting means is used at preset intervals during robot operation. means for starting latching of the output signal of , means for comparing the data after completion of latching by this means with the data of the relative position detection means at each cycle, and a preset error in the comparison result by this means. The present invention is characterized in that it includes means for sequentially cumulatively counting the number of times that the range is exceeded, and when the cumulative count result by this means reaches a preset judgment number, abnormality occurrence processing is executed. Anomaly detection device for industrial robots. 2. An abnormality detection device for an industrial robot according to claim 1, wherein said absolute position detection means is an absolute encoder, and said relative position detection means is an incremental encoder. 3. An abnormality detection device for an industrial robot according to claim 2, wherein said absolute encoder is a potentiometer type position detector. 4. The control device for an industrial robot according to claim 1, wherein the abnormality occurrence processing is at least one of abnormality occurrence display processing and robot main body emergency stop processing.