JPH0736991B2 - 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 restricting an industrial robot such as an arc welding robot, it is necessary to detect the rotation angle of each rotation axis (movable part) such as an arm 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 phase difference of 90 ° .The direction of rotation can be detected by checking the pipe diameter of these pulse signals. Has become.

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 detection signal stored in the first memory 9 and the actual detection signal from the resolver 4 digitized by the R / D converter 6 when the power is turned on. A comparator for comparison, 12 is a compensator, which corresponds to the actual absolute rotational speed of the power-off count value stored in the second memory 10 according to the comparison result from the comparator 11 (details will be described later). After correcting to the actual count value, the correction value is set to the upper bits 2 ⁸ to 2 ^{15 of the} up / down counter 8.
To be set to.

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 will not be miscounted when the power is turned on again.
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 it exceeds a certain level, the industrial robot will be controlled due to a power failure.
It becomes difficult to stop the robot within the time until the CPU becomes inoperable.

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 stopping the possible ratio, it becomes impossible to sufficiently obtain the effect of making the origin adjustment unnecessary by the rotation angle detecting device.

The present invention is intended to solve such a problem, and when a power failure occurs during the operation of the robot, it is possible to determine whether or not the origin alignment operation needs to be performed after the power failure is resolved. In addition, 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 according to the present invention detects a power failure in a power supply system that supplies power to an industrial robot. Means, position data detection means for detecting position data of the same movable part of the industrial robot, and timekeeping for measuring a predetermined time in a period until the same movable part comes to rest after the power failure detection means detects a power failure. Means for storing the first position data from the position data detecting means after the power failure detecting means detects the power failure, and the second position data from the position data detecting means when the time measuring means measures the predetermined time. Set the position data storage means to store and the allowable value of the position data difference corresponding to the speed at which the same movable part can stop at the limit position where the origin alignment operation is unnecessary after a power failure occurs. An allowable value setting means for storing the calculated value, a calculating means for calculating a difference between the first position data and the second position data stored in the position data storage means, and a difference calculated by the calculating means and the allowable value. The allowable value stored in the value setting means is compared, and if the error exceeds the allowable value, it is determined that the origin alignment operation is required after the power failure is resolved, and the difference is within the allowable value. In this case, it is provided with a judging means for judging that the origin alignment operation after the power failure is eliminated is unnecessary.

[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 detects at least two position data at predetermined time intervals, and the position data storing means stores the position data. Then, the determination means obtains a difference (proportional to the speed of the movable portion) between the two position data stored in the position data storage means, and this difference is a permissible value (a predetermined value, and the movable portion stores the position data). The difference is proportional to the velocity of the movable part at the time when the difference is obtained when the vehicle can be stopped at a limit position where the origin adjustment operation is unnecessary. Therefore, when the difference exceeds the permissible value, the determining means does not stop within a range in which the origin adjustment operation is unnecessary after the speed of the movable portion is stored, and the origin adjustment after the power failure is eliminated. It is determined that the operation is necessary. On the other hand, if the difference is within the allowable value, the speed of the movable part is slow and the movable part stops within the range where the origin alignment operation is unnecessary after storing the position data, and the origin alignment operation after the power failure is eliminated is unnecessary. judge.

[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. Reference numerals 15a and 15b are non-volatile memories (position data storage means) for storing and storing the count value (rotational position data of the motor 3) from the up / down counter (position data detection means) 8, respectively. When 15 and 15b receive the storage command (power failure detection signal) from the power failure detection circuit 14, the two count values at a predetermined time interval regarding the rotation angle of the motor 3 are used as two count values for the same movable part of the industrial robot. It is stored as position data. The count values are stored in the memories 15a and 15b at the same time as the count values are stored in the memories 9 and 10.

Further, reference numeral 16 is a judgment device (judgment device) for judging whether or not the origin alignment operation of the industrial robot needs to be performed after the power failure is resolved, based on the data (detection result of the up / down counter 8) stored in the memories 15a and 15b. Means) and this determiner
The 16 obtains the difference obtained by comparing the two count values from the memories 15a and 15b, compares the difference with a preset allowable value, and if the difference exceeds the allowable value, eliminates the power failure. While it is determined that the later origin adjustment operation is necessary, if the difference is within the allowable value, it is determined that the origin adjustment operation after the power failure is eliminated is unnecessary.

Here, the above-mentioned allowable value is the following value which is previously obtained and set by actual measurement, calculation or the like. That is, the motor 3 stores the count value after detecting the position data, that is, the memory 15a,
This is the difference between the position data (count values) stored in each of the memories 15a and 15b in the case of stopping at a limit position where the origin alignment operation is unnecessary after storing in 15b. That is, this allowable value is proportional to the rotation speed of the motor 3 at which the motor 3 can be stopped at the 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
Power failure detection signal (memory command) to U (including memories 15a and 15b)
Is output. 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.

Before explaining the operation of the apparatus of the present embodiment configured as described above, the movement of the robot when the AC power supply 13 suddenly fails during the operation of the industrial robot is shown by a speed change. As shown. First, power failure detection circuit 14
However, after a power failure occurs, the time t ₁ (for example,
However, if a power failure is detected, a stop command is input to the servo driver at the same time as the servo (point P ₁ ), the robot gradually slows down, and then the brake is activated (point P ₁ ). P ₂ ; For example, 50msec after the occurrence of power failure). After that, the power supply voltage of the servo driver is reduced there is no stopping capability (point P _3), thereafter, subjected to the action of only the motor brake, the robot eventually stopped (point P _4). After detecting a power failure,
The time t ₂ before the robot stops is about 200 msec.

A simpler illustration of FIG. 3 is as shown in FIG. Here, the time t ₃ from the power failure detection by the power failure detection circuit 14
After the lapse of time, it is assumed that two position data of the motor 3 (count value of the up / down counter 8) are stored in the memories 15a and 15b at a predetermined time interval Δt.
If t is a short time, as shown in FIG. 4, the speeds v ₁ and v ₂ of the robot (motor 3) at times t ₃ and t ₃ + Δt after the power failure detection are v ₁ ≈v ₂ , Further, the difference between the position data (count values) stored in the memories 15a and 15b becomes the speed when divided by the time interval Δt, and is therefore proportional to the rotation speed of the motor 3 in the predetermined time interval.

Further, when the movement of the robot shown by the speed change in FIG. 4 is shown as a position, the change in the position becomes a quadratic curve as shown in FIG. After the power failure is detected, the coasting distance ΔX ₁ until the robot stops is almost proportional to the square of the speed at the time of the power failure detection, and the time t ₂ until the stop is substantially proportional to the speed at the time of the power failure detection. Similarly, the coasting distance ΔX ₂ from the time t ₃ after the detection of the power failure at which the position data is stored / stored in the memories 15a and 15b until the robot stops is ₂ times the speed at the time of storage.
It is almost proportional to the square.

Here, a specific numerical example of the allowable value preset in the determiner 16 will be shown. Now, assuming that the maximum rotation speed Nmax of the robot motor 3 is 50 times / second, t ₂ = 200 msec (= 0.2
Sec), t ₃ = 0, Δt = 20 msec (= 0.02 sec), and the speed decrease due to Δt can be ignored, and if a power failure is detected at the maximum rotation speed Nmax, each memory 15a,
The difference in the rotation angle (position data) of the motor 3 stored in 15b is Nmax × Δt = 50 × 0.02 = 1 rotation. The number of rotations of the motor 3 from the power failure detection to the stop is (1/2) × Nmax × t ₂ = (1/2) × 50 × 0.2 = 5 rotations. In the rotation angle detection device shown in FIG. 1, as in the case described with reference to FIG. 6, unless the rotation angle of the motor 3 during power off or power failure exceeds ± 180 ° (1/2 rotation), Although the origin adjustment work is not necessary at the time of reclosing, if the motor 3 rotates 5 times and exceeds 1/2 rotation during the power failure as described above, the origin adjustment operation must be performed after the power failure is resolved. Therefore, when the difference in the rotation angle (position data) of the motor 3 stored in each of the memories 15a and 15b is one rotation, it is necessary to perform the origin alignment operation after the power failure is resolved. On the contrary, when the rotation speed v of the motor at the time of the power failure detection when the number of rotations of the motor 3 from the detection of the power failure to the stop is 1/2 rotation is calculated as (1/2) × v × [(v / Nmax) × t ₂ ] = 1/2 v × [(v / 50) × 0.2] = 1 ∴v≈15.8 revolutions / second. Therefore, in the numerical example shown here, the memory 15a,
If the rotation speed of the motor 3 at the time when the position data is stored in 15b is 15.8 rotations / second or less, the motor 3 will stop within the range where origin alignment is unnecessary after the power failure is resolved. At this time, if the difference between the position data of the memories 15a and 15b is 15.8 × 0.02≅0.32 rotations or less, the motor 3 will be stopped within the range where origin adjustment is not necessary after the power failure is resolved. That is, in the numerical example shown here, the allowable value to be preset in the determiner 16 is the count value corresponding to 0.32 rotation.

In the numerical example shown here, t ₃ = 0,
Actually, if this t ₃ can be increased, the allowable speed can also be increased, which is advantageous in judgment. Further, since the time t ₂ from the detection of the power failure to the stop is different depending on the load inertia and the motor capacity, it is desirable to determine it for each axis of the robot.

As shown in the above specific numerical example, the judging device 16 has an appropriate allowable value set in advance, and the power failure detection circuit
When a power failure in the AC power supply 13 is detected by 14, the memories 15a, 15b will be released after an appropriate time (t ₃ ) has elapsed from that point.
Further, two position data (rotation angle of the motor 3; count value) with a time interval Δt detected by the up / down counter 8 are respectively stored and stored.

Then, at the time of eliminating the power failure, in the judging device 16, the memory 15a,
The difference between the two position data stored in 15b is calculated, and this difference is compared with the preset allowable value as described above to determine whether or not the origin alignment operation is necessary.

In other words, in the present embodiment, when the difference between the position data exceeds the allowable value, the determiner 16 determines that the rotation speed of the motor 3 is fast when the position data is stored and the motor 3 is within the range where the origin adjustment operation is unnecessary ( It does not stop within ± 180 °), and it is determined that the origin adjustment operation is required after the power failure is resolved.

On the other hand, if the difference in the position data is within the allowable value, the rotation speed of the motor 3 during storage of the position data is slow and the motor 3 stops within the range where the origin adjustment operation is not necessary (within ± 180 °). As described above with reference to FIG. 6, the memories 9 and 10, the comparator 1
The absolute rotation angle of the motor 3 is detected by the functions of 1 and the corrector 12. Therefore, the determiner 16 determines that the origin alignment operation after the power failure is eliminated is unnecessary.

As described above, according to the apparatus of the present embodiment, when a power failure occurs during the operation of the robot, it is possible to determine whether or not the origin alignment operation needs to be performed after the power failure is resolved with a simple configuration. Depending on the software, only software-like measures are performed without adding hardware, so the applicable range of the origin adjustment unnecessary technology is greatly expanded, and the rotation angle detection device as shown in Figs. The reliability can be increased.

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.
The actual multi-axis robot determines whether or not origin alignment is required as described above for each axis and determines that origin alignment is required when even one axis exceeds the allowable value. Further, the determining unit 16 in the above embodiment may be incorporated in the CPU for robot control.

[Effects of the Invention] As described in detail above, according to the origin alignment necessity / unnecessity determination device for an industrial robot of the present invention, the robot is configured by the power failure detection means, the position data detection means, the position data storage means, the determination means, and the like. If a power outage occurs during the operation of, it is possible to determine whether or not it is necessary to perform home position adjustment operation after the power outage is resolved. Is greatly expanded, and there is an effect that the reliability of the technology for making origin adjustment unnecessary can be improved.

[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. 3 to 5 are graphs for explaining the operation, and FIG. 6 is a block diagram showing a conventional rotation angle detecting device for an industrial robot. 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 (position data storage means), 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 power to an industrial robot, a position data detecting means for detecting position data of the same movable part of the industrial robot, and the power failure detecting means. A time measuring means for measuring a predetermined time in a period after the power failure is detected until the same movable part comes to rest; and a first position data is stored from the position data detecting means after the power failure detecting means detects the power failure, Position data storing means for storing second position data from the position data detecting means when the time measuring means measures the predetermined time, and speed at which the same movable part can stop at a limit position where origin adjustment operation is unnecessary after a power failure occurs Tolerance value setting means for setting and storing the tolerance value of the position data difference corresponding to the first position data and the second position data stored in the position data storage means. Computation means for obtaining the difference between the position data and the tolerance value stored in the tolerance value setting means are compared with each other. If the difference exceeds the tolerance value, a power failure occurs. And a determination unit that determines that the home position alignment operation after the power failure is eliminated is necessary when the difference is within the allowable value. An industrial robot origin alignment required / unnecessary determination device.