JPH0736992B2 - Industrial robot origin alignment required / unnecessary determination device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] In the present invention, in an industrial robot such as an arc welding robot, when a power failure occurs during its operation, it is necessary to perform an origin alignment operation after the power failure is resolved. The present invention relates to a device for determining whether or not.

[Prior Art] Generally, when controlling an industrial robot such as an arc welding robot, it is necessary to detect the rotation angle of each rotation axis (movable part) of the arm or the like with high accuracy, and the power is turned off. It is desired to be able to detect the absolute rotation angle of each rotary shaft without performing the origin alignment operation when the power is subsequently turned on again.

Therefore, conventionally, a rotation angle detecting device as shown in FIG. 6 has been proposed. In FIG. 6, 1 is an arm of an industrial robot, 1a is a rotation axis of the arm 1, 2 is a speed reducer, 3 is a motor for rotating the arm 1 through the speed reducer 2, and 4 is a speed reducer 2 and a motor. A resolver that is connected to the rotation shaft 1a of the arm 1 via 3 to detect an absolute rotation angle (θ) within a predetermined rotation angle (for example, one rotation or 360 °), 5 is a driver that excites the resolver 4, and 6 is a driver. A resolver / digital (R / D) converter for converting the detection signal from the resolver 4 into a digital signal, and 7 is a resolver for converting the detection signal from the resolver 4 into pulses and converting it into an incremental signal having A, B, and Z phases. It is a pulse (R / P) converter. Where Z
The phase pulse signal is for origin setting, and the A and B phase pulse signals are output with a 90 ° phase difference.The direction of rotation can be detected by checking the relationship between these pulse signals. ing.

Also, 8 is an up-down counter, A from R / P converter 7, counts the pulse signals of the B-phase, the lower bits 2 ⁰ to the absolute rotational angle within one rotation of the 8-bit 256 divided motor 3
Outputs at 2 ^7, corresponding to one rotation of the motor 3
2 ⁷ carry, counting the borrow signal, and outputs at the upper bit 2 ^{8-2 15} as the absolute rotation speed of the motor 3. 9 first memory for storing a count value for the lower bits 2 ^{0-2 7} from the detection signal (1 absolute within the rotation angle of rotation) up-down counter 8 from the resolver 4 at the time when the power is turned off, 10 Are the upper bits 2 ⁸ to 2 ¹⁵ from the up / down counter 8 at the time of power off.
The second memory 11 for storing the count value for the power-off state is a real detection signal from the resolver 4 digitized by the R / D converter 6 when the power is turned on again, and a power-off detection signal stored in the first memory 9. Comparator for comparing, 12 is a compensator,
Depending on the comparison result from the comparator 11 (details will be described later),
After the power-off count value stored in the second memory 10 is corrected to the actual count value corresponding to the actual absolute rotation speed, the corrected value is stored in the upper bits 2 ⁸ to 2 of the up / down counter 8.
^It is set to ¹⁵ .

In the above-mentioned device, when the power is turned on again, the R / D converter 6
Actual detection signal from the resolver 4 digitized is adapted to be set to the lower bit 2 ^{0-2 7} from the up-down counter 8 by. The first memory 9 and the second memory 10 are composed of a non-volatile memory, a battery-backed RAM, or the like.

With the above-described configuration, at the time of normal rotation angle detection, the origin is first adjusted, and then the excitation phase (sin ω
The detection phase sin (ωt +) from the resolver 4 which has received t, cosωt)
θ) is output, the absolute rotation angle θ within one rotation of the motor 3 is obtained from this detection phase, and the detected signal is the R / P converter 7
Pulsed by. And pulse signal (A, B phase)
Is counted by the up / down counter 8,
The absolute rotation angle of within one rotation from the lower bit 2 ^{0-2 7} is output, the absolute from the upper bit 2 ^{8-2 15} of the motor 3 speed is output, 1 the absolute rotation angle within the rotation, (absolute The absolute rotation angle of the motor 3 is detected as the sum of (rotation speed) × 360 °.

When the device is turned off while the origin is once adjusted and the rotation angle is detected, the detection signal from the resolver 4 at that time is the lower bit 2 from the up / down counter 8. together and stored as a count value in the first memory 9 for ^{0-2 7,} upper bits 2 ^{8-2 15} from the up-down counter 8 at the same time is stored in the second memory 10. At this time, by turning off the power, the count value in the up / down counter 8 is reset, but the stored contents in the memories 9 and 10 are not volatilized.

Further, when the power is turned off, the motor 3 is braked by a brake (not shown), and even if the arm 1 receives an external force (gravitational moment or the like) by the time the power is turned on again, it is ± 180 ° or more. Do not rotate. In this way, the difference in the rotation angle of the motor 3 when the power is turned off and when the power is turned on again is ±
Within 180 °, the absolute rotation angle of the motor 3 can be corrected and detected as follows, and the origin alignment operation can be made unnecessary.

That is, when the power is turned on again after the power is turned off, first, the detection signal from the resolver 4 is digitized by the R / D converter 6 and increased as an absolute rotation angle within one rotation when the power is turned on again. Lower bit of down counter 8
It is also input to the comparator 11 together with a renewed set input to the 2 ^{0-2 7.} In the comparator 11, the actual detection signal from the resolver 4 is compared with the detection signal when the power is turned off, which is input from the first memory 9, and a correction command is output to the corrector 12 according to the difference. Here, when the comparison result in the comparator 11 [(actual detection signal from the resolver 4)-(detection signal from the first memory 9 when the power is off)] is -180 ° to + 180 °, a correction command is output. No, second when −360 ° to −180 °
Count value when the power is turned off from the memory 10 (upper bit 2 ⁸
While adding only 1 ~ 2 ^15), and outputs the correction command to the corrector 12 to subtract only 1 from the count value when the 180 ° to 360 °.

As a result, even if the motor 3 receives external force and rotates during the power-off period to cross the zero detection point of the resolver 4,
The number of rotations of the motor 3 is not miscounted when the power is turned on again, and the comparator 11 and the compensator 12 allow the second memory
The power-off count value stored in 10 is corrected to the actual count value corresponding to the actual absolute rotation speed including rotation during the power-off period, and then the upper bits 2 ⁸ to 2 ^{15 of the} up-down counter 8 Is set to.

Therefore, even if the motor 3 rotates during the power-off period,
When the power is turned on again, the absolute rotation angle of the motor 3 is the sum of the absolute rotation angle within 1 rotation from the resolver 4 and (actual count value obtained by correction) × 360 °. Is accurately detected as the output of the power source and the rotation angle of the motor 3 during power off does not exceed ± 180 °, the origin alignment work is not required when the power is turned on again.

[Problems to be Solved by the Invention] By the way, if the power is turned off while the operation of the industrial robot is stopped, the posture of the industrial robot is usually sufficiently maintained by the braking force of the brake of the motor 3, so the power is turned off. The rotation angle of the motor 3 during the period has an error of only the amount of backlash of the brake and never exceeds ± 180 °. Therefore, the above-described conventional rotation angle detection device detects the absolute rotation angle of the motor 3 without performing the origin alignment operation.

In addition, if the motor 3 operates at a certain speed or less, even if the power supply on the primary side suddenly turns off (power failure state), the industrial robot detects its power failure state and then It is possible to stop within 180 ° and store the information regarding the position data at that time in the memories 9 and 10. However, if the robot is moving at a certain speed or more at the time of power failure, it becomes difficult to stop the robot within the time until the CPU that controls the industrial robot becomes inoperable due to the power failure. .

Therefore, if the power supply to the primary side is cut off during robot operation, such as a power outage, it may not be possible to make home position adjustment unnecessary from the beginning, and it may be necessary to always perform home position adjustment operation after the power outage is resolved. To be However, during actual robot operation, the robot often stops at a low speed within the range that does not require home position adjustment. Only by reducing the possible ratio, it becomes impossible to sufficiently obtain the effect of making the origin adjustment unnecessary by the rotation angle detecting device.

In order to solve such a problem, it has been proposed to determine whether or not the origin alignment is necessary after the power failure is eliminated when the power failure occurs as follows.

As shown in FIG. 7, when the power failure is detected after a lapse of time t ₁ after the power failure occurs, a stop command is input to the servo driver, and the robot gradually decreases its speed.
At this time, the position data of the same movable part of the robot is detected at least twice after the time t _{3 has} elapsed and the time t ₃ + Δt has elapsed since the detection of the power failure. Then, based on the obtained difference ΔX ₃ between the two position data, it is determined whether or not the origin alignment operation of the robot needs to be performed after the power failure is resolved. That is, [difference ΔX ₃ ] and [difference Δ in the case where the movable part can be stopped at the limit position where the origin alignment operation is unnecessary after detecting the position data.
It compares the allowable value] and corresponding to the X _3, while determining that if the difference [Delta] X ₃ exceeds the allowable value is necessary origin combined operation after a power failure persists, the difference [Delta] X ₃ is the allowable value If it is within the range, it is determined that the origin adjustment operation after the power failure is eliminated is unnecessary. In FIG. 7, ΔX ₁ is the coasting distance until the robot stops after the power failure is detected, t ₂ is the time until the robot stops after the power failure is detected, and ΔX ₂ is the time t ₃ after the power failure is detected.
Is the coasting distance from when the robot stops.

In such determination of necessity / unnecessity of origin adjustment, it is desirable to make the time t ₃ sufficiently large (preferably longer than the time t ₂ ) in order to accurately judge the necessity / unnecessity. However, in general, the time t ₂ from the detection of a power failure to the stop of the robot is considered to be about 200 msec, whereas the time during which the CPU, which is the control device of the robot, and other LSIs are operating The time required to maintain the power supply voltage) is about 100 msec. Each time varies depending on the operating conditions, but the latter operating time is determined by the residual voltage stored in the capacitor such as a capacitor after a power failure and is extremely unstable depending on the condition of the capacitor. is there. In order to extend the operation time, it is necessary to increase the capacity of the capacitor etc. and it is economically limited. Therefore, in the above-mentioned origin alignment necessity / unnecessity judgment, the CPU is operated only for about 100 msec after the power failure is detected. However, it can be said that it is the best because the time t ₃ is set to 80 msec and Δt is set to 20 msec, for example. However, as mentioned above, the CPU
Since the time of the operation is highly variable, considering the safety for the origin combined Y / N judgment is performed, it is inevitable to reduce the time t _3, the accuracy and decision execution determination Safety There is a trade-off with sex.

The present invention is intended to solve the various problems described above, and when a power failure occurs during the operation of a robot, it is possible to accurately and surely determine whether or not it is necessary to perform an origin alignment operation after the power failure is resolved. Therefore, it is an object of the present invention to provide an origin alignment necessity / unnecessity determination device for an industrial robot in which the applicable range of the origin alignment unnecessary technology is expanded.

[Means for Solving the Problems] In order to achieve the above object, the origin alignment necessity / unnecessity determination device for an industrial robot of the present invention detects (a) a power failure in a power supply system that supplies power to the industrial robot. (B) position data detection means for detecting the position data of the same movable part of the industrial robot, and (c) the same movable part stops at a limit position where the origin alignment operation is unnecessary after a power failure occurs. Allowable setting means for setting and storing the allowable value of the position data difference corresponding to the available speed, and (d) a time measuring means for measuring time while sequentially advancing at predetermined time intervals after the power failure detecting means detects a power failure, e) position data storage means for storing the latest two position data while updating the predetermined time interval, and (f) a difference between the two position data updated and stored in the position data storage means. The calculation means to be obtained, (g) Compare the difference obtained by the calculating means with the allowable value stored in the allowable value setting means, and if the difference exceeds the allowable value, perform the above (d) to (f). Repeatedly and compared with the allowable value again, it is determined that the origin adjustment is not required after the power failure is eliminated only when the difference is within the allowable value, and in other cases, it is determined that the origin adjustment is required after the power failure is eliminated. And means.

[Operation] In the above-described industrial robot origin alignment necessity / unnecessity determination device of the present invention, when a power failure occurs during the operation of the robot, this is detected by the power failure detection means, and after the detection, a predetermined same movable part of the robot is detected. With respect to, the position data detecting means continuously detects the position data at regular time intervals. Then, the determination means obtains the difference (proportional to the speed of the movable part) between the two position data from the position data detection means at a fixed time interval. This difference is sequentially obtained until the difference becomes equal to or less than a predetermined allowable value, and the determining means determines that the speed of the movable part is slow and the movable part is aligned with the origin only when the difference is within the predetermined allowable value. It stops within the range where operation is not necessary, and it is judged that the origin adjustment operation after power failure is unnecessary.

[Embodiment of the Invention] An origin alignment necessary / unnecessary judging device for an industrial robot according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows its block diagram and FIG. 2 shows its power failure detection circuit. It is a circuit diagram shown. In this embodiment, a case where the device of the present invention is applied to a rotation detecting device similar to that shown in FIG. 6 will be described. In the figure, the same reference numerals as those used above indicate the same parts, and a description thereof will be omitted.

In FIG. 1, 13 is an AC power supply that supplies electric power to an industrial robot (motor 3 etc.), 14 is a power failure detection circuit (power failure detection means) that detects a power failure of the power supply 13 system, and the details of its configuration are the second. It will be described later with reference to the drawings. Further, 15a and 15b are memories for storing the count value (rotational position data of the motor 3) from the up / down counter (positional data detecting means) 8, respectively, and each of the memories 15a and 15b is a power failure from the power failure detection circuit 14. When the detection signal is received, the count value related to the rotation angle of the motor 3 is set to a constant time interval Δt (for example, a control cycle of 20 mse).
It is stored as position data for the same movable part of the industrial robot alternately for each c).

Further, reference numeral 16 is a judging device (judging means) for judging whether or not it is necessary to perform the origin alignment operation of the industrial robot after the power failure is resolved, based on the detection result of the up / down counter 8 input via the memories 15a and 15b. ), And this determiner 16
Compares the count values from the memories 15a and 15b with each other to open a constant time interval Δt as shown in FIG.
One of the location data Pn, and P _n-1 difference _{(Pn-P n-1)} successively sought (in FIG. 3 illustrates until n = 7), a predetermined allowable value [Delta] x ₀ in advance is set as the difference Compare and compare that with a given tolerance Δ
Only when it is within x ₀ , it is judged that the origin adjustment operation after the power outage is unnecessary. In the determiner 16, the difference (Pn-Pn- ₁ ) is continuously calculated until it becomes equal to or less than a predetermined allowable value Δx ₀ .

Here, the predetermined allowable value Δx ₀ is obtained and set in advance by actual measurement, calculation, etc., and is proportional to the rotation speed of the motor 3 at which the motor 3 can be stopped at a limit position where the origin adjustment operation is unnecessary. .

On the other hand, the power failure detection circuit 14 includes a rectification circuit 17, a smoothing circuit 18, a DC-DC converter 19, and a constant voltage circuit 2 as shown in FIG.
0, determination circuit 21, transmission circuit 22 and the like.
That is, the voltage from the AC power supply 13 for which a power failure should be detected is rectified by the rectification circuit 17 and smoothed by the smoothing circuit 18, and then the level is monitored by the determination circuit 21. In the determination circuit 21, the voltage between the DC-DC converter 19 is input to the constant voltage circuit 20 such as a Zener diode and the voltage obtained as its output is set as the reference voltage, and the voltage level being monitored is If the voltage becomes lower than the reference voltage, it means that a power failure has occurred and the transmission circuit 22
A power failure detection signal (judgment start command) is output to U (including the memories 15a and 15b and the judgment device 16). The time from the occurrence of a power failure to the detection of the power failure (see t _{1 in} FIG. 3) is adjusted by the values of the capacitor C and the resistors R _{1 to} R _{3 in} the power failure detection circuit 14.

Now, before explaining the operation of the apparatus of the present embodiment configured as described above, to describe the movement of the robot when the AC power supply 13 suddenly fails during operation of the industrial robot,
The movement has, for example, a quadratic curve shape as shown in FIG. First, the power failure detection circuit 14 takes time t ₁ (for example, about 10 msec) to detect the power failure after the power failure occurs. However, when the power failure is detected, a stop command is input to the servo driver at the same time as the servo, and Gradually reduces its speed, and then the brake is applied. After that, the power supply voltage of the servo driver decreases and the stopping ability disappears, and thereafter, only the motor brake acts, and the robot finally stops. It should be noted that the time t ₂ from when the power failure is detected until the robot stops is about 200 msec.

The apparatus of the present embodiment determines the necessity / unnecessity of origin adjustment according to the flow shown in FIG. That is, an appropriate predetermined allowable value Δx ₀ is set in advance in the judging device 16, and the power failure detection circuit
When a power failure in the AC power supply 13 is detected by 14 (step S1), the position data (rotation angle of the motor 3; count value) Pn is detected by the up / down counter 8 at constant time intervals Δt from that point (step S1). S2), and are alternately stored in the memories 15a and 15b.

Then, in the judging device 16, a constant time interval Δ from the up / down counter 8 obtained via the memories 15a and 15b.
The difference (Pn-Pn _-1 ) between the two position data apart from t is obtained (step S3). If the time interval Δt is short here, the speeds V ₁ and v ₂ of the robot (motor 3) after a constant time interval Δt after the power failure detection are v ₁ ≈v ₂ and each memory is The difference (Pn-Pn _-1 ) between the position data (count values) stored in 15a and 15b is the speed when divided by the constant time interval Δt, and is proportional to the rotation speed of the motor 3.

The absolute value of the calculated difference (Pn-Pn- ₁ ) in the position data is compared with a predetermined allowable value Δx ₀ (step S4), and the difference, that is, | Pn-Pn _-1 | is the predetermined allowable value. Only when it is within Δx ₀ , the speed of the motor 3 is slow and the motor 3 stops within the range where the home position adjustment operation is not required (within ± 180 °), so it is judged that the home position adjustment operation after the power failure is unnecessary. Then, the origin alignment unnecessary flag is set and the final position data Pn is stored (step S5). The final position data Pn is stored in the memory 9,
On the other hand, the origin alignment unnecessary flag is stored in the nonvolatile memory (not shown) while being stored in 10. (For example, when the flag is set, it is stored as “0” when it is not set).

Further, in the present embodiment, the calculation of the position data difference (Pn-Pn _-1 ) is repeated until it falls within a predetermined allowable value Δx ₀ . For example, if | P ₄ −P ₃ |> Δx ₀ and | P ₅ −P ₄ | ≦ Δx ₀ , the position data P ₅ is detected, and the subsequent work is stopped. On the other hand, the condition in step S4 | Pn−P _n-1 | ≦
Before Δx ₀ is satisfied, the power supply voltage drops and the CPU
When the (determination device 16) does not operate, the origin alignment unnecessary flag is not set. Therefore, when the power is turned on again, the fifth
As shown in the figure, it is judged whether or not the origin alignment unnecessary flag is set (whether it is "1") (step S
6) If the flag has not been set, the origin adjustment work is performed (step S7). If the flag is set, the final position data Pn is used and the current value (absolute of the motor 3 Rotation angle is created (step
S8). In addition, during the work of creating the current value using the final position data Pn, if it is determined that the origin alignment is necessary,
The origin alignment work will be executed.

As described above, according to the apparatus of the present embodiment, when a power failure occurs during the operation of the robot, it is extremely unstable after the power failure to determine whether or not the origin alignment operation needs to be performed after the power failure is detected. As it is performed reliably and accurately in the state,
The applicable range of the origin adjustment unnecessary technology is greatly expanded, and the reliability of the rotation angle detection device as shown in FIGS. 1 and 6 can be improved. Further, in the present embodiment, the necessity / non-necessity of the origin adjustment is achieved by a simple configuration and in some cases only by software-like measures without adding hardware.

In the above-described embodiment, whether or not the origin alignment is necessary / unnecessary is determined only for one axis of the robot motor 3.
In an actual multi-axis robot, it is determined whether or not origin alignment is necessary as described above for each axis, and if even one axis is determined to be origin alignment, origin alignment is performed. Further, the determining unit 16 in the above embodiment may be incorporated in the CPU for robot control.

Further, in the above-described embodiment, the detection and determination work is stopped when the condition | Pn−P _n−1 | ≦ Δx ₀ is satisfied, but even if this condition is satisfied, while the CPU is operating, May continuously detect the position data, store the substantially final position data Pm immediately before the stop of the CPU, and use the position data Pm to create the current value when the power is turned on again.

[Effects of the Invention] As described in detail above, according to the origin alignment necessity / unnecessity determination device for the industrial robot of the present invention, the power failure detection means, the position data detection means, and the determination means cause the power failure during the operation of the robot. In the event of a power failure, it is configured so that it can be judged whether or not it is necessary to perform the home position alignment operation, so a simple configuration greatly expands the applicable range of the home position alignment unnecessary technology. , There is an effect that it is possible to enhance the reliability of the technology for eliminating the origin alignment.

Also, after detecting a power failure, the value is continuously compared with the permissible value at predetermined time intervals until the speed at which it can be stopped at the limit position where the origin alignment operation is not required. Even if occurs, it is possible to accurately and surely determine whether or not the origin alignment is necessary. Therefore, it is possible to detect a wide range of origin adjustment unnecessary and reduce extra origin adjustment as much as possible. Further, by reducing the predetermined time interval and the allowable value, it is possible to determine whether or not origin alignment is necessary while collecting the position data until almost the stop state is reached. Therefore, the final position data in the position data storage means is used to determine the current value. Can also be created.

[Brief description of drawings]

1 to 5 show an origin alignment necessary / unnecessary judging device for an industrial robot as an embodiment of the present invention. FIG. 1 is a block diagram thereof, and FIG. 2 is a circuit diagram showing a power failure detecting circuit thereof. , FIG. 3 is a graph for explaining the operation, FIGS.
Each of the figures is a flow chart for explaining the operation thereof. FIG. 6 is a block diagram showing a conventional rotation angle detecting device for an industrial robot, and FIG. 7 is a origin alignment necessity / unnecessity determining means for the industrial robot. It is a graph for explaining an example. In the figure, 1 ... Arm, 1a ... Rotation axis, 2 ... Reducer, 3 ... Motor, 4 ... Resolver, 5 ... Driver,
6 ... Resolver / digital (R / D) converter, 7 ... Resolver / pulse (R / P) converter, 8 ... Up-down counter (position data detecting means), 9 ... First memory, 10
…… Second memory, 11 …… Comparator, 12 …… Compensator, 13 ……
Power supply, 14 ... Power failure detection circuit (power failure detection means), 15a, 15b
...... Memory, 16 ・ ・ ・ Judgment device (judgment means), 17 ・ ・ ・ Rectification circuit, 18 ・ ・ ・ Smoothing circuit, 19 ・ ・ ・ DC-DC converter, 20
...... Constant voltage circuit, 21 …… Judgment circuit, 22 …… Transmission circuit.

Claims (1)

[Claims] 1. A power failure detecting means for detecting a power failure of a power supply system for supplying electric power to an industrial robot; and a position data detecting means for detecting position data of the same movable part of the industrial robot. , (C) Allowable value setting means for setting and storing an allowable value of position data difference corresponding to a speed at which the same movable part can stop at a limit position where origin adjustment operation is unnecessary after a power failure occurs, (d) detection of the power failure And a position data storage unit for storing the latest two position data at a predetermined time interval while updating the latest position data after the unit detects the power failure. (F) a calculating means for obtaining a difference between the two position data updated and stored in the position data storing means, and (g) a difference obtained by the calculating means and the allowance stored in the allowance value setting means. The value is compared and the difference is If it exceeds the allowable value, (d) to (f) are repeated and compared with the allowable value again, and it is determined that origin adjustment is not necessary after the power failure is canceled only when the difference is within the allowable value. However, in other cases, the origin alignment necessity / unnecessity determination device for the industrial robot is provided with a determination means for determining that the origin alignment is required after the power failure is resolved.