JPH0549165B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for detecting the absolute rotation angle of an arm or the like in an industrial robot.

[Prior art] Generally, when controlling industrial robots, etc.
A detection device that can detect the rotation angle of each rotation axis of the arm etc. with high precision is required, and such a rotation angle detection device can be constructed at a lower cost than an absolute type detection device, which has a complicated structure and is therefore expensive. Simple incremental detection devices are commonly used.

Conventionally, this rotation angle detection device has six and seven
There is something like the one shown in the figure. In FIGS. 6 and 7, 1 is an arm of an industrial robot, 2 is a motor that rotationally drives the arm 1 via a reduction gear (not shown), and 3 is a pulse encoder (PE). This pulse encoder 3 is connected to the rotating shaft of the motor 2, and as shown in FIG. It outputs a Z pulse signal as well as A and B pulse signals for rotation angle detection. Here, the A and B pulse signals are output with a phase difference of 90°, and the direction of rotation can be detected by looking at the sequential relationship between these A and B pulse signals.

In addition, 4 is a striker fixed to arm 1;
5 is placed on the fixed side and is turned on by striker 4,
6 is an up-down counter that counts the number of A and B pulse signals from the pulse encoder 3 and outputs the count value as a rotation angle. It is a zero signal generator. This zero signal generator 7 receives the Z pulse signal from the pulse encoder 3 in response to an on/off signal from the limit switch 5, and generates an up/down counter 6.
This is to set the origin of.

Furthermore, 8 is a main control device which receives the count value from the up-down counter 6 as the rotation angle of the arm 1 and controls the drive of the arm 1.

With the above configuration, when detecting the rotation angle,
First, when the arm 1 starts moving from its original position, as shown in FIG.
As the B pulse signal begins to be output, the striker 4 comes into contact with the limit switch 5, turning it from off to on. Then, after the limit switch 5 is turned on, the zero signal generator 7 resets the up-down counter 6 at the time when the Z pulse signal is first input to the zero signal generator 7 as the origin. A clear signal is output to perform home alignment.

Thereafter, the up-down counter 6 determines the rotation direction based on the A and B pulse signals inputted from the pulse encoder 3, and counts up or down the A and B pulse signals depending on whether the rotation direction is forward or backward.

In this way, the count value (16 bits is shown in FIG. 7) counted by the up-down counter 6 is output as the mechanical angle to be detected.

[Problems to be Solved by the Invention] However, in the conventional rotation angle detection device as described above, it is necessary to perform home alignment to reset the up-down counter 6 before starting detection or before restarting detection after turning off the power. Must be. Since the limit switch 5 is installed near the stroke end that the arm 1, etc. does not normally reach (for the purpose of increasing the life of the limit switch 5, etc.), when adjusting the origin, the movement is quite large and moves to the stroke end, which takes time. , the robot arm, etc. will have to perform complicated operations in a narrow space with various devices placed nearby, and there is a high risk of damage to the robot or peripheral devices. It is hoped that

Therefore, when the power is turned off after home alignment has been performed, the count value of the up-down counter 6 is stored as rotation angle data in a non-volatile memory (bubble memory, EEPROM, etc.) or in a battery-backup RAM. A method is used to store it in a At this time, when the power is turned off, a brake within the motor 2 is used to firmly fix the arm 1 and the like so that they do not move. Then, when the power is turned on again and detection is restarted, the rotation angle data stored in the memory is forcibly set in the up-down counter 6, or the rotation angle data is used to start the count from the up-down counter 6. I am trying to correct the value.

With this configuration, when the power is turned on again, the count value of the up-down counter 6 becomes a value corresponding to the shape (position) of the robot, making it unnecessary to adjust the origin.

However, such a rotation angle detection device assumes that the robot arm, etc. is completely fixed by braking, but there is some play in the brake, and even if the fluctuation due to this play is a few pulses, When the device is turned on and off several times, errors due to backlash accumulate, resulting in a discrepancy between the detected rotation angle and the position of the robot. For this reason, consideration must be given to aligning the origin at least once a week in the sense of refreshing.

Additionally, while the power is off, the robot arm may rotate while dragging the brake due to contact with a worker or the gravitational moment. In such cases, the rotation angle is not counted at all, resulting in a large detection error. become.

Furthermore, in order to solve this problem, a method has been developed in which the current consumption of the counter is designed to be extremely small and the counter is backed up by a battery. In addition, encoders that incorporate this battery and counter into encoders have even been developed. However, since this backup battery is generally consumed in about one month, if more time passes than that, problems similar to those described above will occur.

The present invention attempts to solve the above-mentioned problems, and even if a rotating member such as an arm rotates between when the power is turned off and when the power is turned on again, when the power is turned on again, the rotating member does not rotate. By making it possible to set the device to a state where the absolute rotation angle can be detected regardless of the amount of rotation, there is no need to perform any home alignment work when the power is turned on, eliminating problems associated with home alignment, and improving the accuracy of absolute rotation angle detection. An object of the present invention is to provide a rotation angle detection device for an industrial robot that has improved performance.

[Means for Solving the Problems] Therefore, the rotation angle detection device for an industrial robot of the present invention is attached to the rotation shaft of a rotating member and detects a predetermined rotation angle (one rotation or a finite angle) of the rotation shaft.
an absolute rotation angle detector that detects an absolute rotation angle within a certain range; a pulse generation means that outputs a pulse signal at each predetermined rotation angle as the rotating member rotates; and a pulse generation means that counts the pulse signal from the pulse generation means. In the rotation angle detection device, the pulse counter is configured to detect a predetermined posture detection signal from the absolute rotation angle detector when the rotary member is in a predetermined posture, and a pulse counter for the predetermined posture of the rotary member. first and second storage means each storing a count value of the pulse counter at a predetermined posture after initialization; and a state in which the rotating member is set near the predetermined posture when the power of the rotation angle detection device is turned on again. a comparison means for comparing the actual detection signal from the absolute rotation angle detector and the detection signal at the predetermined posture from the first storage means;
The present invention is characterized in that a correction means is provided for correcting the count value at the predetermined posture from the second storage means to an actual count value corresponding to the actual mechanical angle in accordance with the comparison result.

[Function] In the above-mentioned rotation angle detection device for an industrial robot according to the present invention, the detection signal at a predetermined posture from the absolute rotation angle detector when the rotating member is set in a predetermined posture (absolute rotation angle within a predetermined rotation angle) is detected. ) and a count value (a multiple of the predetermined rotation angle) by the pulse counter after initializing the pulse counter for the predetermined attitude of the rotating member (a multiple of the predetermined rotation angle) are stored in first and second storage means, respectively. . When the power is turned on, the comparison means compares the experimental signal from the absolute rotation angle detector with the predetermined attitude detection signal in the first storage means with the rotating member set near the predetermined attitude. In accordance with the difference, the correcting means corrects the predetermined attitude count value in the second storage means to an actual count value corresponding to the actual mechanical angle.

Therefore, even if the rotating member rotates between when the power is turned off and when the power is turned on again, after the power is turned on again, the rotation angle detection device (pulse The absolute rotation angle of the rotating member is calculated as the sum of (the predetermined rotation angle) x (the corrected actual count value) and the actual detection signal from the absolute rotation angle detector. Accurately detected.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a rotation angle detection device for an industrial robot as a first embodiment of the present invention. , 1 is an arm of an industrial robot as a rotating member, 1a is a rotating shaft of the arm 1, 2 is a motor that rotationally drives the arm 1 via a reducer 2a, and 9 is an arm 1 via a reducer 2a and a motor 2. An absolute encoder is an absolute rotation angle detector that is connected to the rotation shaft 1a of the motor and detects the absolute rotation angle (θ) within a predetermined rotation angle (one rotation of the motor shaft). It is divided into 256 8-bit parts and output as lower bits ²⁰ to ²⁷ . In addition, 10 receives the zero signal from the absolute encoder 9 and outputs the motor shaft 1.
The pulse generator is a pulse generator that outputs two pulse signals Z ₁ and Z ₂ with a 90° phase shift as shown in Fig. 2 for each rotation.
The direction of rotation can be detected by looking at the relationship between Z ₁ and Z ₂ .

Reference numeral 11 designates an up-down counter as a pulse counter that counts pulse signals Z ₁ and Z ₂ from the pulse generator 10, and calculates the absolute rotational speed of the motor shaft of the motor 2 based on the count value by upper bits (2 ⁸ ~ ²¹⁵ 8 bits).

Note that Z ₁ and Z ₂ are equivalent to the carry-borrow signal for the ²⁷ most significant bits of the absolute rotation angle output, and the up-down counter 11 may of course be driven by the carry-borrow signal.

On the other hand, 12 is a first memory serving as a first storage means for storing a detection signal (absolute rotation angle within one rotation of the motor shaft) from the absolute encoder 9 when the arm 1 is in a certain predetermined attitude. , 13 is a second memory as a second storage means for storing the predetermined posture count value from the up-down counter 11 when the arm 1 is in the above predetermined posture, and 14 is a comparator as a comparison means. The actual detection signal from the absolute encoder 9 is compared with the detection signal at the predetermined attitude stored in the first memory 12 with the arm 1 set at the predetermined attitude. Further, 15 is a corrector as a correction means, and according to the comparison result from the comparator 14 (details will be described later), the second memory 13
After correcting the predetermined attitude count value stored in , to an actual count value corresponding to the actual absolute rotational speed, the corrected value is set in the up-down counter 11.

Note that the first memory 12 and the second memory 13
is non-volatile memory (bubble memory or EEPROM)
etc.) or battery backed up RAM.
Consists of etc.

In addition, if the predetermined posture is determined in advance, ROM
It is better to store (write) it in (read-only memory).

Since the rotation angle detection device according to the first embodiment of the present invention is configured as described above, during normal rotation angle detection, the absolute encoder 9 directly detects the absolute rotation angle within one revolution of the motor 2. It is detected as the lower bits ²⁰ to ²⁷ , and is also detected by the pulse generator 10 and up/down counter 11.
The absolute rotation number (count value) of motor 2 is obtained as the upper bits ²⁸ to ²¹⁵ , and the absolute rotation number of motor 2 is obtained as the sum of the absolute rotation angle within one rotation and (absolute rotation number) x 360°. Angle (that is, rotation axis 1a
absolute rotation angle) is detected.

Now, after adjusting the origin or some other initialization, before turning off the power for the first time, set the posture of the entire industrial robot, including arm 1, etc., to an appropriate predetermined posture that is easy for the robot to take. The predetermined attitude detection signal from the absolute encoder 9 is stored in the first memory 12, and the predetermined attitude count value from the up-down counter 11 in the same state is stored in the second memory 13.

For example, in the case of a welding robot, as shown in FIGS. 3a and 3b, a torch 1 installed at the tip of the upper arm 16
7 is aligned with the tip of the positioning jig 18 fixed on the floor to position the three degrees of freedom, and the wrist angle is determined using a spirit level 19 etc. attached to the torch 17, and a predetermined posture is obtained. decide. Alternatively, marks may be provided for each degree of freedom and the predetermined posture may be determined by matching these marks. For example, as shown in FIG. 3c, the turntable 20
Positioning marks (or holes, dents, protrusions, etc.) 21 are provided on the movable part and fixed part of the
As shown in FIG. 3d, a through hole 23 for positioning is provided between the upper arm 16 and the lower arm 22, and a pin is inserted into this for positioning.

Note that after the power is turned off, the count value in the up-down counter 9 is reset, but the count value in the memory 1
The contents stored in 2 and 13 will not be volatile.

Then, after storing the detection signal and count value in the predetermined posture in the memories 12 and 13 as described above, when the power is turned off and then turned on again, the entire robot including the arm 1 etc. Guide the posture to the above posture using the inching button, etc. in the same manner as teaching. At this time, the means explained with reference to FIGS. 3a to 3d is used to confirm whether the robot's posture has reached the predetermined posture.

When the robot is set to the predetermined attitude, the experimental output signal from the absolute encoder 9 in that state and the predetermined attitude detection signal from the first memory 12 are input to the comparator 14 and compared. A correction command is output to the corrector 15 according to the difference.

By the way, when the robot is set to the above-mentioned predetermined posture after the power is turned on, this predetermined posture and the memories 12, 1
If the data in 3 completely matches the data in memories 12 and 13, the data in memories 12 and 13 can be used as is as the absolute rotation angle. Since this is performed using a measuring instrument that has a 100-degree angle, there is a slight discrepancy between the data in the memories 12 and 13 (however, the rotation of the motor shaft does not exceed 90 degrees). If such a deviation occurs, the rotation angle of the arm 1, etc. when resetting to the above-mentioned predetermined posture may cross the zero detection point of the absolute encoder 9 (for example, it may deviate from 10° in the negative direction and become 350°). degree or deviates from 350° in the positive direction to 10°), and in such cases, if the count value at the predetermined posture in the memory 13 is used as is, the rotation of the motor 2 will be only one rotation. This will cause a detection error.

Therefore, in this embodiment, the predetermined attitude detection signal is stored in the first memory 12, and compared in the comparator 14 with the actual detection signal from the absolute encoder 9 at the time when the robot is set in the predetermined attitude. , If the comparison result [(actual detection signal from absolute encoder 9) - (detection signal at predetermined attitude from first memory 12)] is between -90° and +90°, no correction command is output. The count value at the predetermined posture from the second memory 13 is directly set in the up-down counter 11, and in the case of -360° to -270°, the second
A correction command is output to the corrector 15 so as to add 1 to the predetermined posture count value from the memory 13, while a correction is made to subtract 1 from the predetermined posture count value in the case of 270° to 360°. A correction command is output to the device 15. Here, it is assumed that the motor axis of motor 2 does not deviate by more than 90° in the data in memories 12 and 13 when the robot is reset to a predetermined posture, but it is assumed that the motor axis does not deviate by more than 180°. In this case, when the comparison result in the comparator 14 is between -180° and +180°, no correction command is output, and when the comparison result is between -360° and -180°, 1 is added to the predetermined attitude count value from the second memory 13. On the other hand, when the angle is from 180° to 360°, the count value at the time of the predetermined posture is corrected so as to be subtracted by 1.

Note that if the above comparison result obtained by the comparator 14 is outside the above angle range,
For safety, an alarm may be output as abnormal value detection.

As a result, when the posture of the entire robot including arm 1 is set when the power is turned on, even if the set position is a position that crosses the zero detection point of the absolute encoder 9, the absolute rotation speed of the motor 2 can be changed. Comparator 14 without miscounting
The corrector 15 corrects the predetermined posture count value stored in the second memory 13 to an actual count value corresponding to the actual absolute rotational speed, and then sets it in the up-down counter 11.

Therefore, during the power off period, arm 1 and motor 2
Even if the motor 2 rotates due to an external force, when the power is turned on again, the device is set to a state where the absolute rotation angle can be detected regardless of the amount of rotation, and the absolute rotation angle of the motor 2 is determined as the absolute rotation angle. encoder 9 to 1
It is now accurately detected as the sum of the absolute rotation angle within the rotation and (actual count value obtained by correction) x 360°.

As described above, according to the first embodiment of the present invention, the predetermined posture can be maintained without being affected by the rotation of the arm 1 (that is, the motor 2) that occurs between when the power is turned off and when the power is turned on again. Since the up-down counter 11 is set based on this, there is no need for home alignment or strict mastering (calibration) when the power is turned on again, and the accuracy of detecting the absolute rotation angle is greatly improved. That's what I do.

Next, a description will be given of a rotation angle detection device as a second embodiment of the present invention. FIG. 4 is a block diagram thereof. This second embodiment is different from the first embodiment. The only difference is that instead of using the absolute encoder 9 as the absolute rotation angle detector, a resolver 24 is used.

In FIG. 4, 24 is connected to the rotating shaft 1a of the arm 1 via the reducer 2a and the motor 2, and detects the absolute rotation angle (θ) within a predetermined rotation angle (one rotation of the motor shaft). 24a is a driver that excites the resolver 24; 25 converts the detection signal from the resolver 24 into a digital signal, divides the absolute rotation angle within one rotation of the motor into 256 8 bits, and outputs the lower bits 2 ² to 2. The pulse converter 10 is a resolver/digital (R/D) converter that outputs as ⁷ , and every time it receives a zero signal from this R/D converter 25, the pulse converter 10 outputs pulse signals Z ₁ , Z ₂ or a carry borrow signal. R/
The bit output from the D converter 25 is stored in the first memory 12 as a predetermined attitude detection signal or an actual detection signal.
and is input to the comparator 14. The rest of the configuration is completely the same as that of the first embodiment, so a description thereof will be omitted.

With the above-described configuration, in this second embodiment, during normal rotation angle detection, the resolver 24 receives the excitation phase (sinωt, cosωt) from the driver 24a and outputs the detection phase sin(ωt+θ). The absolute rotation angle θ within one rotation of the motor 2 is obtained,
The detection signal is digitized by the R/D converter 25 and obtained as lower bits 2 ⁰ to ^{2 7} , and the absolute rotation of the motor 2 is obtained by the pulse generator 10 and up/down counter 11 as upper bits 2 ⁸ to 2 ¹⁵ . The number (count value) is obtained, 1
The mechanical angle of the motor 2 (that is, the mechanical angle of the rotating shaft 1a) is detected as the sum of the absolute rotation angle within the rotation and (absolute rotation number) +360°.

In addition, the functions of the first memory 12, second memory 13, comparator 14, and corrector 15 are exactly the same as in the first embodiment, and the second embodiment also has the same functions as in the first embodiment. Effects can be obtained.

Finally, to explain a rotation angle detection device as a third embodiment of the present invention, FIG. 5 is a block diagram thereof, and in this embodiment, as in the second embodiment,
A resolver 24 is used as an absolute rotation angle detector. Further, in FIG. 5, 26 is a resolver/digital (R/D) converter that converts the detection signal from the resolver 24 into a digital signal, and 27
is a resolver/pulse (R/P) converter as a pulse generating means that pulses the detection signal from the resolver 24 and converts it into an incremental signal having A, B, and Z phases. Here, the Z-phase pulse signal is for setting the origin, and the A and B-phase pulse signals are output with a 90° phase difference.By looking at the sequential relationship of these pulse signals, the rotation direction can be determined. It is becoming detected.

Further, 28 is an up/down counter as a pulse counter, and the A and B signals from the R/P converter 27 are
It counts the phase pulse signals and outputs the absolute rotation angle within one rotation of the motor 2 divided into 256 8 bits as the lower bits 2 ⁰ to 2 ⁷ . The A and B phase pulse signals (the Z phase pulse signal may also be used) output from the P converter 27 are counted, and the upper bits 2 ⁸ to 2 ¹⁵ are calculated as the absolute rotation number of the motor 2.
This is what is output at.

In this third embodiment, the output from the lower bits 2 ⁰ to 2 ⁷ of the up-down counter 28 is
While being inputted to the first memory 12 and the comparator 14 as a predetermined posture detection signal or an actual detection signal, the upper bit 28 of the up-down counter ²⁸
The output from ~2 ¹⁵ is output to the second memory 13 as a count value at the time of the predetermined posture. Also, comparator 1
The actual detection signal input to the up-down counter 28 is obtained from the R/D converter 26, and the count value corrected by the corrector 15 is set in the upper bits ²⁸ to ²¹⁵ of the up-down counter 28. The rest of the configuration is completely the same as that of the first embodiment, so the explanation will be omitted.

In the device of the third embodiment, when the power is turned on again, the actual detection signal from the resolver 24 digitized by the R/D converter 26 is transferred to the lower bits 20 ^{to 27} from the up/down counter 28. It is now set.

With the above-described configuration, in this third embodiment, during normal rotation angle detection, after the origin is aligned, the detected phase is output from the resolver 24 in the same manner as in the second embodiment.
sin(ωt+θ) is output, an absolute rotation angle θ within one rotation of the motor 2 is obtained from this detection phase, and the detection signal is converted into a pulse by the R/P converter 27. By counting the pulse signals (A, B phases) with the up-down counter 28, the absolute rotation angle within one revolution is output from the lower bits ²⁰ to ²⁷ , and the motor output is output from the upper bits ²⁸ to ²¹⁵ . The rotation speed (count value) of 2 is output, and the mechanical angle of the motor 2 (that is, the mechanical angle of the rotating shaft 1a) is detected as the sum of the absolute rotation angle within one rotation and the rotation speed +360°.

In addition, the functions of the first memory 12, second memory 13, comparator 14, and corrector 15 are exactly the same as those in the first embodiment, and the third embodiment is also exactly the same as the first embodiment. Effects can be obtained.

In addition, in the above-mentioned embodiments, in any case,
The corrected count value by the corrector 15 is sent to the counter 11.
Alternatively, the compensator 15 corrects the count value at the predetermined posture from the second memory 13, and then converts the corrected count value into the count value after the power is turned on (the count value after the power is turned on). (zero at the time of input) may be added.

[Effects of the Invention] As detailed above, according to the rotation angle detection device for an industrial robot of the present invention, even if the rotating member rotates due to external force during the power off period, the amount of rotation is detected. Since the rotation angle detection device is set based on the predetermined posture without being affected by There is no need for any alignment work or strict mastering (calibration) work, which greatly improves the detection accuracy of absolute rotation angles, and makes it possible to create a complete multi-rotation type absolute rotation angle detection device at an extremely low cost and with a simple configuration. There are effects that can be obtained.

In addition, as an encoder, we have prepared a rotary plate that generates an absolute signal for one rotation or less, and for multiple rotations, we have a counter inside the encoder of a low current consumption type and also have a built-in small battery. An electronic absolute encoder has been developed that includes absolute signals. Even in such an encoder, the internal battery cannot be used forever and the counter may be reset when the battery runs out, but even in such a case, the present invention allows easy initialization.

[Brief explanation of the drawing]

1 to 3 show a rotation angle detection device for an industrial robot as a first embodiment of the present invention.
The figure is a block diagram of the robot, FIG. 2 is a waveform diagram showing pulse signals from the pulse generator, and Figures 3a to 3d are diagrams for explaining means for setting the robot to a predetermined posture. FIG. 4 is a block diagram showing a rotation angle detection device for an industrial robot as a second embodiment of the invention, and FIG. 5 is a block diagram showing a rotation angle detection device for an industrial robot as a third embodiment of the invention. 6 to 8 show a conventional rotation angle detection device for an industrial robot. FIG. 6 is a front view of a rotating member to which the device is applied, FIG. 7 is a block diagram thereof, and FIG. The figure is a timing chart for explaining the pulse signal output from the pulse encoder and the origin setting means. In the figure, 1...an arm as a rotating member;
1a...Rotating axis, 2...Motor, 2a...Reducer, 9...Absolute encoder as an absolute rotation angle detector, 10...Pulse generator as pulse generation means, 11...Pulse counter 12...first memory as first storage means, 13...second memory as second storage means, 14...comparator as comparison means, 15...as correction means corrector, 24
...Resolver as absolute rotation angle detection means, 24
a... Driver, 25, 26... Resolver/digital (R/D) converter, 27... Resolver/pulse (R/P) converter as pulse generation means,
28...Up-down counter as a pulse counter.

Claims (1)

[Claims] 1. An absolute rotation angle detector that is attached to the rotating shaft of the rotating member and detects the absolute rotation angle within a predetermined rotation angle of the rotating shaft, and outputs a pulse signal at each of the predetermined rotation angles as the rotating member rotates. and a pulse counter that counts the pulse signals from the pulse generating means, the mechanical angle of the rotating member is determined based on the detection signal from the absolute rotation angle detector and the count value by the pulse counter. A rotation angle detection device that outputs corresponding angle information, comprising: a first storage means for storing a predetermined posture detection signal from the absolute rotation angle detector when the rotary member is in a predetermined posture; A second step for initializing the pulse counter for a predetermined posture and storing a count value obtained by the pulse counter during the predetermined posture at the predetermined posture.
storage means, and when the rotation angle detecting device is powered on again, the actual detection signal from the absolute rotation angle detector and the first storage means are stored with the rotation member set near the predetermined posture. a comparison means for comparing the detection signal at the predetermined posture of the
and a correction means for correcting the count value at the predetermined posture from the second storage means to an actual count value corresponding to the actual mechanical angle in accordance with the comparison result by the comparison means. Robot rotation angle detection device.