JPH0425388A - Detection device for position of industrial robot - Google Patents

Abstract

PURPOSE:To drastically simplify the device structure and to eliminate the need for a gear mechanism, by arranging two position detectors at the input side of a speed reducing mechanism. CONSTITUTION:The rotation of the output side of the member to be driven, i.e. a speed reducing mechanism 2 is led to the input side of the speed reducing mechanism 2 via the output shaft 2f and detection shaft 19 of the speed reducing mechanism 2. The rough positional information of the member 2 to be driven is then detected by the 2nd position detector 5 arranged at this input side and the absolute position of the member 2 to be driven is detected by composing the detection result thereof with the dense position information fed from a 1st position detector 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a position detection device for detecting the absolute rotational position of a rotating shaft of an arm or the like in an industrial robot such as an arc welding robot.

[Prior Art] Traditionally, as a position detection device for an industrial robot, an incremental encoder is used, and a limit switch (home limit switch) is provided at the operating limit, and the following home position adjustment work is performed when the power is turned on. After that, position detection is performed. In other words, after the robot is moved to its operating limit, the limit switch is activated, and the robot is moved in the opposite direction, the first Z pulse (one per revolution) output from the incremental encoder causes
Reset the counter. From then on, as the robot moves, the incremental encoder outputs 9
A and B pulses having a phase difference of 0'' are counted up and down by a counter, and the count value is used as position information of the robot.

However, the incremental type position detection means using such an incremental encoder requires a fairly complicated work of adjusting the origin when the power is turned on.

Therefore, conventionally, various devices have been proposed that are equipped with two absolute position detectors (detecting the absolute rotation angle within one rotation) such as multi-rotation absolute encoders and resolvers.

For example, two absolute position detectors are installed across a reducer with a relatively large reduction ratio, and one absolute position detector detects coarse positions, while the other absolute position detector detects fine positions. , means for synthesizing these detection results to detect the absolute position of multiple rotations.

With such a multi-rotation absolute type position detection means, the absolute angle of each axis can be obtained immediately after the power is turned on due to its principle, so the origin alignment described above is not necessary and the space required for origin alignment work can be saved. Can be omitted. In addition, since the detection results are basically data equivalent to the angle of the motor shaft and its multiple rotations, it is possible to obtain a highly accurate angle of the robot arm, etc. that actually moves via the reducer. become.

Incidentally, in order to provide two absolute position detectors as described above, a device having a configuration as shown in FIG. 5 has been proposed. In FIG. 5, 50 is an arm of an industrial robot, 50a is a rotating shaft of arm 50, 51 is a deceleration mechanism connected to one end of the rotating shaft 50a, and 52 is a deceleration mechanism 5.
a drive motor 53 for rotationally driving the arm 50 via 1;
54 is a first absolute position detector connected to the rotating shaft of the drive motor 52; The gear mechanism 55 is composed of two spur gears 55a and 55b.

With such a configuration, the first absolute position detector 53 detects detailed position information, and the second absolute position detector 54 detects coarse position information, and from these position information, the absolute position information of the arm 50 is detected. The positions are combined.

[Problems to be Solved by the Invention] However, in the conventional position detection device for an industrial robot, it is necessary to provide the gear mechanism 55 in order to provide the absolute position detector 54 on the output side of the deceleration mechanism 51, that is, on the arm 50 side. However, the structure around the arm 50 becomes complicated, which is disadvantageous in terms of design around the arm 50.

The present invention aims to solve such problems,
It is an object of the present invention to provide a position detection device for an industrial robot that is equipped with two absolute position detectors and has a simplified structure by allowing these absolute position detectors to be arranged compactly.

[Means for Solving the Problems] In order to achieve the above object, the position detection device for an industrial robot of the present invention includes first and second position detectors provided on the input side and the output side of the deceleration mechanism, respectively. , which detects the absolute position of the driven member based on the absolute rotation angle signal from these position detectors, an input shaft of the speed reduction mechanism provided coaxially with the output shaft of the speed reduction mechanism and formed hollow;
The detection shaft has one end fixed to the output shaft and is guided to the input side of the deceleration mechanism by passing through the hollow part of the input shaft, and a second position detector provided at the other end of the detection shaft. It is characterized by

[Function] In the above-described position detection device for an industrial robot of the present invention,
The rotation of the driven member, that is, the output side of the speed reduction mechanism, is guided to the input side of the speed reduction mechanism via the output shaft and the detection shaft of the speed reduction mechanism. Then, coarse position information of the driven member is detected by the second position detector disposed on the input side, and the detection result is combined with the fine position information from the first position detector. Thus, the absolute position of the driven member is detected.

[Embodiments of the invention] Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 3 show a position detection device for an industrial robot as a first embodiment of the present invention, FIG. 1 is a cross-sectional view showing its main parts, and FIG. 2 is a block diagram showing its circuit configuration. , FIG. 3 is a block diagram showing a modification of the circuit configuration.

As shown in FIG. 1, in this embodiment, a lever 24 for driving the upper arm (not shown) of the robot via a link mechanism (not shown) is used as a driven member, and this lever 24 is driven. A case where the present invention is applied to a portion will be explained.

In order to rotate the lever 24 around the S1 axis, the lever 24 is connected to the output shaft 2f of the reduction mechanism (harmonic reduction gear) 2 by a bolt 24a, and the input shaft 2d of the reduction mechanism 2 is connected to the pulley 18. It is connected to the drive motor 3 via a timing belt 17 and a pulley 16.

Here, the pulley 18 is attached to the input shaft 2d, the pulley 16 is attached to the rotating shaft 3a of the drive motor 3, and the timing belt 17 is wound around these pulleys 16 and 18. Due to this.

The rotational driving force of the drive motor 3 is applied to the pulley 16. It is transmitted to the speed reduction mechanism 2 via the timing belt 17 and the pulley 18, and after being decelerated by the speed reduction mechanism 2, it is transmitted to the lever 24 through the output shaft 2f. Note that the drive motor 3 is connected to the fixed side (frame) 39 of the robot.
The timing belt 17 is mounted in such a way that it can be moved slightly in the vertical direction in FIG. 1 with respect to the fixed side 39 in order to adjust the tension of the timing belt 17.
The timing belt 17 can be fixed at a position where the tension is appropriate.

The drive motor 3 arranged in this way has its rotating shaft 3a.
A first resolver (first position detector) 4 is attached that generates an absolute rotation angle signal (fine position information on the input side of the reduction gear mechanism 2) within a finite angle range (for example, 180° or 360'). ing.

Further, the speed reduction mechanism 2 includes a circular spline 2a, a wave generator 2b, and a flex spline 2C.
The circular spline 2a is connected to the bolt 3.
8 is attached to the fixed side 39, and a flex spline 2C is attached to the output shaft 2f. Further, the input shaft 2d of the reduction mechanism 2 is supported on the fixed side 39 by a bearing 35, and the output shaft 2f of the reduction mechanism 2 is supported on the fixed side 39 and the arm (lower arm) 23 by bearings 36 and 37, respectively. It is pivotally supported.

The input shaft 2d of the deceleration mechanism 2, which is provided coaxially with the output shaft 2f of the deceleration mechanism 2, has a hollow portion 2e formed along its axis. Further, one end side of a detection shaft 19 is fixed to the output shaft 2f by a bolt 19a, and this detection shaft 19 is guided to the input side of the deceleration mechanism 2 through the hollow part 2e of the input shaft 2d. The other end of the input shaft 19 is exposed outside the input shaft 2d.

The other end of the detection shaft 19, which is exposed to the outside, is connected via a coupling 34 to a rotor that generates an absolute rotation angle signal (coarse positional information on the output side of the deceleration mechanism 2) of the detection shaft 19 within a finite angle range. Two resolvers (second position detectors) 5 are attached. This resolver 5 is fixed to a fixed side 39 by a resolver fixing fitting 33.

Note that the reference numeral 40 in FIG. 1 indicates an oil seal.

The apparatus of this embodiment is constructed as shown in FIG. 2 in order to detect the absolute position based on the absolute rotation angle signals from the two resolvers 4 and 5 provided in this manner. In FIG. 2, reference numerals 6 and 7 are a common CO8 excitation circuit and a SIN excitation circuit that are always connected to the resolvers 4 and 5 to simultaneously excite these resolvers 4 and 5, and these CO8 excitation circuits 6. Resistors 9 and 10 are interposed between the SIN excitation circuit 7 and the resolver 5, respectively, and the impedance of the excitation phase of the second resolver 5 is set higher than the impedance of the excitation phase of the first resolver 4. There is.

Further, reference numeral 8 denotes a common R sum processing circuit which receives the absolute rotation angle signals from the resolvers 4 and 5 and performs waveform processing. The connection is sequentially switched and connected. 12 is one resolver/digital converter (hereinafter referred to as an R/D converter) connected to the R sum processing circuit 8;
This R/D converter 12 digitizes the absolute rotation angle signal from each resolver 4, 5 after processing by the R-sum processing circuit 8 and outputs it in bits.

Furthermore, 13 is a resolver/pulse converter (hereinafter referred to as an R/P converter) attached to the R/D converter 12, and this R/P converter 13 has an absolute rotation angle from the first resolver 4. This converts a signal into an incremental pulse, which is a two-phase pulse (A pulse and B pulse) with a 90° phase difference. 14 is A from the R/P converter 13
A pulse counter 15 counts up and down pulses and B pulses, and performs absolute position calculation processing and switching control of the switch 11 as described below based on data (position information) from the R/D converter 12 and the pulse counter 14. Arithmetic device 1 (CPU), 15a to 15e are arithmetic device 1
5, registers 15a and 15b
are for storing the absolute rotation angle signals (digital values) of the resolvers 4 and 5 from the R/D converter 12, and use a general-purpose register, RAM, etc. in the arithmetic unit 15.

The registers 15c and 15d are for storing the absolute rotation angle signals (digital values) from the resolvers 4 and 5 at that time, respectively, with the basic posture of the robot (e.g., a vertically or horizontally determined angle) as a mechanical reference. A backed up version, ROM, etc. is used. The register 15e is
It stores the absolute position initial value calculated as described later, and is constituted by a RAM or the like.

Since the device according to the first embodiment of the present invention is configured as described above, the lever 24 receives the rotational driving force of the drive motor 3 decelerated by the speed reduction mechanism 2 through the output shaft 2f, and the lever 24 is rotated. The upper arm is driven to swing through a link mechanism connected to 24.

At this time, the rotation of the lever 24 is caused by the rotation of the output shaft 2 of the deceleration mechanism 2.
f and the detection shaft 19 to the outside (input side) of the input shaft 2d of the deceleration mechanism 2, and is transmitted to the second resolver 5 attached to the detection shaft 19. This results in
As the lever 24 rotates (swings the upper arm), rough positional information on the output side of the deceleration mechanism 2 is obtained by the resolver 5. Further, detailed positional information on the input side of the speed reduction mechanism 2 is obtained by the resolver 4.

In this embodiment, the absolute position I! of the rotating shaft 3a of the motor 3 is determined as follows. (that is, the position of the lever 24) is detected.

First, when the power is turned on, the switch 11 is sequentially switched to the resolver 4 side/resolver 5 side by a command from the arithmetic unit 15, and the R sum processing circuit 8 and the R/D converter 12
Then, the position information (absolute rotation angle signal) from each resolver 4, 5 is input to the arithmetic unit 15 as a parallel digital value, and each digital value is input to the register 15a, 1.
5b. Here, for example, each resolver 4.5 is an IX resolver (one that generates one cycle of signals in one rotation), and the R/D converter 12 has 4096 pulses (
12 bits)/1 period. In addition, the basic posture of the robot, for example, vertically and horizontally, is set as a mechanical standard, and the absolute rotation angle signals (digital values) from each resolver 4 and 5 at that time are P 1o t P 2
6 and stored in the registers 15c and 15d (this work is normally performed by the manufacturer at the time of initial adjustment of the robot).

Now, when the power is turned on, the switch 11 is first switched to the resolver 4 side, the absolute rotation angle signal from the resolver 4 at that time is stored in the register 15a as a digital value P1, and then the switch 11 is switched to the resolver 5 side. is switched, and the absolute rotation angle signal from the resolver 5 at that time is stored in the register 15b as a digital value P2.

Based on the data stored in the registers 15a to 15d, the arithmetic unit 15 calculates the initial absolute position value at power-on in a first-order manner.

That is, the difference between the position information P2 from the second resolver 5 and the reference position information P2 is multiplied by the number N equivalent to the reduction ratio of the reduction mechanism 2 to obtain the number 4 equivalent to one cycle of the first resolver 4.
096, and the integer part is taken as the number of rotations or the number of cycles (coarse position information; upper bits of position information) of the second resolver 5. On the other hand, position information P from the first resolver 4
1 and the reference position information P1° is defined as position information within one rotation or one period (dense position information; lower bits of position information). This can be expressed as the following equation (1).

f((P2-P2゜)XN/4096)X4096+(
P, -Pl. )...(1) However, f() represents the integer part of the numerical value in ().

In addition, if the power is turned on near P0 valve P1°, f
(P2 Px.)XN/
The decimal part of 4096 is corrected so that it almost matches (P knee P1°)/4096. For example, the decimal part above is 0°9
5 and (px Pl.)/4096 is 0.05, then as equation (1), f((P a P za
)XN/4096)X4096+1 is used.

Now, the upper bits and lower bits of the position information obtained as described above are used as the initial value (absolute position initial value) of the position information when the power is turned on, and the register 15e of the arithmetic unit 15 is used.
After the first resolver 4 is stored in the R/D converter 12, the switch 11 is connected to the resolver 4 so that the first resolver 4 is always connected.
The R/P converter 13 attached to the R/D converter 12 outputs two phase A and B incremental pulses in response to the absolute rotation angle signal from the resolver 4.

The incremental pulses are constantly counted up and down by the pulse counter 14, and the count value and the initial value stored in the register 15e are summed by the arithmetic unit 15, and the summed result is output as position information.

In this embodiment, the case where incremental pulses are obtained by the R/P converter 13 is explained.
Without using the R/P converter 13 or pulse counter 14, the third
As shown in the figure, a counter 14A is provided between the R/D converter 12 and the arithmetic unit 15, and the digital value from the first resolver 4 is used as it is, and only the upper bits are processed by the counter 14A using carry and borrow signals. It may be configured to count.

As described above, according to the first embodiment of the present invention, the speed reduction mechanism 2 for power reduction can be utilized, and at the same time, a gear mechanism, timing belt, etc., as in the past, is not used on the 8-force side of the speed reduction mechanism 2. , 2ili resolvers 4 and 5 can be placed on the input side of the deceleration mechanism 2, which greatly simplifies the device structure, and since no gear mechanism is used, there is no effect of backlash caused by gears, etc. can be avoided.

In addition, in this embodiment, in particular, the speed reduction mechanism 2 and the drive motor 3 are
This has the advantage that the length in the axial direction can be significantly shortened.

Further, according to this embodiment, immediately after the power is turned on, the absolute position initial value is created using the multi-rotation absolute type detection method using the two resolvers 4 and 5, and then the incremental type detection method is used. Adopting the detection method, the first
Since the absolute position is detected by adding up the incremental pulses created based on the dense position information from the resolvers 4 to the initial value, the absolute position is detected by adding up the incremental pulses created based on the dense position information from the resolvers 4 and 5. There is no need to perform synthetic calculation processing on the absolute rotation angle signal, the calculation load on the calculation device 15 and the like is reduced, and detection accuracy can be greatly improved with a simple configuration.

Furthermore, in this embodiment, in addition to using and switching the common R/D converter 12 for the two resolvers 4 and 5, the excitation circuit JI 6 and 7 and the R sum processing circuit 8 are also used for the two resolvers 4 and 5. 5
Since the configuration is designed to be common to both resolvers 4 and 5, an R/Dll converter is provided for each resolver 4 and 5.

There is no need to provide an excitation circuit, an R sum processing circuit, etc., and the electrical circuit required for the device is halved compared to the conventional one.

In addition, the signal cable between the robot and the control panel used to require 3 pairs per resolver, but now requires only 4 pairs with 2 resolvers. , 5, it is sufficient to provide only the electric circuit required for one resolver, which greatly simplifies the device configuration.

Equipment costs can also be significantly reduced.

By the way, by switching the two resolvers 4 and 5, the R/D
When connecting to the converter 12 (R sum processing circuit 8) and the excitation circuit 6.7 As in this embodiment, the excitation circuit 6.7 is left connected to the two resolvers 4 and 5, The number of switches can be saved. Furthermore, dividing into two resolvers 4 and 5 on the robot side is extremely advantageous as it saves signal cables between the robot and the control panel.

At this time, if the excitation times M6 and M7 are not strong, the impedance of the excitation phase of the resolvers 4 and 5 will
This will disturb the IN curve, COS curve, and their phases. In terms of circuitry, there is usually a volume or the like for adjusting this, and the impedance of this excitation phase usually changes depending on the position of the detector. When there is one resolver, the total error is considered in consideration of this impedance change, but when there are two resolvers as in this embodiment, the error may be doubled.

Therefore, in this embodiment, the second resolver 4 is
By increasing the winding impedance of the excitation phase of the first resolver 5 by about 2 to 3 times, and by interposing resistors 9 and 10 in series with the excitation phase of the second resolver 5, the excitation of the first resolver 4 is increased. Disturbances are kept to a minimum. As a result, the absolute rotation angle signal (fine position information) from the first resolver 4, which is directly involved in motor control and tends to include rotational irregularities and position errors, is protected from changes in the impedance of the second resolver 5, and is Detection accuracy can be obtained. As mentioned above, when a resistor 9.10 (or inductance) is inserted in the excitation phase, the output (detector) of the second resolver 5 becomes smaller, so it is necessary to adjust this by adjusting the transformation ratio, etc. You may also do so.

Next, a second embodiment of the present invention will be described. FIG. 4 is a sectional view showing a main part of a position detection device for an industrial robot as a second embodiment of the present invention.

Incidentally, in FIG. 4, the same reference numerals as those described above indicate the same parts, so the explanation thereof will be omitted.

In the first embodiment described above, the case where the speed reduction mechanism 2 and the drive motor 3 were connected via the pulleys 16, 18 and the belt 17 was explained, but in the second embodiment of the present invention,
As shown in FIG. 4, the input shaft 2d of the reduction mechanism 2 and the rotation shaft 3a of the drive motor 3 are directly connected, and the rotation shaft 3a of the drive motor 3 is also directly connected to the rotation shaft 4a of the first resolver 4. has been done.

Therefore, in this embodiment, the rotating shaft 3a of the drive motor 3 and the rotating shaft 4a of the first resolver 4 are provided along the axes of the rotating shafts 3a, 4a so as to communicate with the hollow portion 2e of the input shaft 2d. Hollow parts 3b and 4b are respectively formed in the detection shaft 19, one end of which is fixed to the output shaft 2f, and the detection shaft 19 is connected to the input shaft 2d.
Hollow portion 2e and hollow portions 3b, 4 of rotating shafts 3a, 4a
b to the outside of the first resolver 4 (deceleration mechanism 2
(input side), and is exposed to the other end of the detection shaft 19 or to the outside of the resolver 4.

The second resolver 5 is attached to the other end of the detection shaft 19 exposed to the outside via a coupling 34. Note that this resolver 5 has resolver fixing fittings 33.
is fixed to the outside of the first resolver 4.

With such a configuration, the second embodiment of the present invention can obtain the same effects as the first embodiment.

In particular, in the second embodiment of the present invention, the entire device can be constructed slimly, which is advantageous when the present invention is applied to the wrist of a robot.

In the above embodiment, the case where the resolvers 4 and 5 are used as the two position detectors has been described, but an absolute encoder may also be used.

In this case, the excitation circuits 6 and 7 and the R/D converter 12 are not necessary (some kind of converter may be necessary depending on the signal format such as the Gray code). In this case, ■ one of the first absolute encoders that detects dense position information.
Create a carry-borrow signal at the rotation boundary and use this to create the upper bit, or ■ Provide the first absolute encoder with a function that simultaneously generates an incremental pulse in addition to the absolute rotation angle signal, and use this incremental pulse as a pulse. By counting with a counter, the same effect as in the above embodiment can be obtained.

In addition, in the above embodiment, the lever 2 for swinging the upper arm is
Although the case where the present invention is applied to the drive unit of No. 4 has been described, the present invention is not limited thereto, and is similarly applicable to drive units such as other joints.

[Effects of the Invention] As detailed above, according to the position detection device for an industrial robot of the present invention, the two position detectors are arranged on the input side of the deceleration mechanism, so that the structure of the device can be reduced. In addition to being greatly simplified, since no gear mechanism or the like is used, the effect of backlash caused by gears or the like can be avoided.

[Brief explanation of the drawing]

1 to 3 show a position detection device for an industrial robot as a first embodiment of the present invention, FIG. 1 is a cross-sectional view showing its main parts, and FIG. 2 is a block diagram showing its circuit configuration. , FIG. 3 is a block diagram showing a modification of the circuit configuration,
FIG. 4 is a sectional view showing the main parts of a position detection device for an industrial robot as a second embodiment of the present invention, and FIG. 5 is a schematic configuration diagram showing a conventional position detection device for an industrial robot. . In the figure, 2 - reduction mechanism, 2a - circular spline, 2b - wave generator, 2C - flex spline, 2d - human power shaft, 2e - hollow part, 2f - output shaft, 3 - drive motor, 3 a - rotating shaft, 3b-hollow part, 4-first resolver (first position detector)-4a-
Rotating shaft, 4b-hollow part, 5-second resolver (second position detector), 6-CO5 excitation circuit, 7-8IN excitation circuit, 8-R phase processing circuit, 9.10-resistance, 11- Switch, 12 Resolver/digital (R/D) converter, 13-
Resolver/pulse (R/P) converter, 14.14A pulse counter, 15-processing unit (CPU), 15 a ~
15 e-register, 16-pulley, 17 timing belt, 18-pulley, 19-detection shaft, 19a-bolt, 23-arm (lower arm), 24 lever (driven member),
24 a-bolt, 33 resolver fixing metal fittings, 34-coupling, 35-37-bearing, 38-bolt,
39-fixed side (frame), 40-oil seal. Patent applicant: Kobe Steel, Ltd.

Claims (1)

[Scope of Claims] First and second position detections provided on the input side and output side of the speed reduction mechanism of a drive unit, which is formed by connecting a drive motor to a driven member of an industrial robot via a speed reduction mechanism, respectively. In the position detection device for an industrial robot that detects the absolute position of the driven member based on an absolute rotation angle signal from a device, the speed reduction mechanism is provided coaxially with the output shaft of the speed reduction mechanism and formed hollow. an input shaft; a detection shaft having one end fixed to the output shaft and guided to the input side of the reduction mechanism through a hollow portion of the input shaft; and the detection shaft provided at the other end of the detection shaft. 1. A position detection device for an industrial robot, characterized in that it is equipped with a position detector.