JPS62225908A - Position detector - Google Patents

Abstract

PURPOSE:To perform the matching of the origin point little by little at a time without requiring a wide space, in an apparatus for detecting the rotary position of a rotary shaft, by arranging a limit switch for detecting the origin at a position where the angular position from the origin is predetermined. CONSTITUTION:A limit switch LS1 for detecting a constant position is temporarily used as one for detecting the origin and, when a rotary shaft rotates to the right direction, the dock provided to the rotary shaft interferes to output a pulse signal. When an incremental type rotary encoder 1 with a Z-pulse sends out the first Z-pulse after the falling signal thereof was generated, the count value of a pulse counter 2 is reset to 0 by a Z-pulse signal. When the interval of the Z-pulse is an n-pulse, the position where the adjacent Z-pulse is generated shows an angular position of DELTAthetaXn.

Description

[Detailed Description of the Invention] The present invention relates to a position detection device using an incremental type rotary encoder with a Z pulse, which enables origin alignment within a particularly narrow operating range. The present invention relates to a position detection device.

BACKGROUND OF THE INVENTION For example, incremental rotary encoders are generally used for positioning industrial robots and their peripheral devices.

This is because incremental encoders are advantageous in terms of cost, have a small number of control wires (easier to handle), and current absolute encoders have lower resolution, etc. This is because it is inferior to incremental encoders.

However, the problem with incremental encoders is that errors accumulate and control accuracy gradually deteriorates, so an operation called home alignment is often performed to find the starting point (origin) of the pulse counter and restart counting from there. It is necessary to correct the count value.

Usually, in robots, etc., a limit switch is provided around the rotating shaft to set the origin position and the limit position of the operating range, and a dog that interferes with these limit switches is provided on the rotating shaft side to prevent the rotating shaft from rotating. The count value of the pulse counter is cleared to zero starting from the time when the dog activates the limit switch for detecting the origin point, and the counter is increased/decreased from there.
Obtaining location information.

For example, in the example shown in Figure 5+81, two limit switches (limit switches for detecting operating limits) LS, LS, These two limit switches are also used to detect the origin. Further, in the example shown in FIG. 5 (bl), in addition to the limit switches LS, . . . LS0 for detecting the operating limit, a separate limit switch LS' for detecting the origin is provided within the operating range.

For example, the procedure for updating the origin when the independent origin detection limit switch LS' shown in Figure 5 above is provided is as follows:
This will be explained using the waveform diagram shown in FIG. in this case,
An encoder with a Z pulse (an encoder that generates two pulses once per rotation of the input shaft of the encoder) is used as an incremental rotary encoder. A rotary encoder is used that can detect the direction of rotation and count the pulses by generating two pulses.

In Figure 4, Z pulses are generated as shown in Figure 4 (C1).However, in the case of the one shown in this figure, an output of 6 pulses is obtained per revolution, but in reality, the output is 10 pulses per revolution.
It has a resolution of 0 to several 100 pulses.

In this case, the origin detection limit switch L
The on/off signal of S' is shown in Figure 4 Fdl, and when the first two pulses after the falling signal of this origin pulse are input, the value of the pulse counter is cleared to 0 at this point, and then By counting up/down the pulse signal again, position information with less error is obtained.

This principle also applies to the limit switch for detecting the origin and the limit switch for detecting the operating limit shown in FIG. 5+81.

Problems with the conventional technology In general, with robots, etc., it is different when the robot is operated in a sufficiently wide space, but when the robot is used in a narrow work area due to lack of space, it is necessary to adjust the origin as described above. However, with conventional methods that require the robot to be moved to a special position, a situation occurs where the robot cannot be used.

For example, if the limit switch for detecting the origin and the limit switch for detecting the operating limits are used together as shown in Fig. 5(a), the origin cannot be adjusted unless the robot is moved to the limit position of the operating range. However, since the robot must be operated close to its operating limit, the operating range of the robot is severely restricted. Furthermore, if the origin is aligned at a part of the center of the robot's operating range as shown in No. 51!1(b),
Since the origin can be aligned near the center of the operating range that is most frequently used, this is advantageous for robots with a small footprint. However, if the origin alignment is performed in a frequently used location as mentioned above, there is a risk of interference between the workpiece and the robot when the origin alignment is performed, and an operator must be present each time the origin alignment is performed. This causes a problem.

OBJECTS OF THE INVENTION The object of the present invention is to solve the above-mentioned problems that occur because the limit switch for detecting the origin is installed at one location in the prior art.

Structure of the Invention The main means adopted by the present invention to achieve the above object is that in a device for detecting the rotational position of a rotational shaft whose rotational angle is limited to an operating limit of 360°, An incremental rotary encoder with a Z pulse installed on the motor side, a pulse counter that counts the pulse signals generated from the above incremental rotary encoder with 2 pulses, and a pulse counter installed within the operating limit of the rotation axis to calculate the angular position from the origin. is a fixed position information generating means that generates information on a plurality of predetermined fixed positions, and after the pulse signal from the fixed position information generating means is input, when the first Z pulse is input, the rotation axis is The position detecting device further comprises a reset means for resetting the value of the pulse counter to a predetermined number corresponding to the fixed position information generating means in accordance with the rotation direction at that time.

Among the above components, the fixed position information generating means may be a switch such as a limit switch similar to that described in the prior art, but may also be an absolute that is connected to the rotating shaft and outputs the absolute rotation angle of the rotating shaft. It may be a type rotary encoder.

Embodiments Next, embodiments embodying the present invention will be described with reference to FIGS. 1 to 3 to provide an understanding of the present invention.

Here, FIG. 1 is a block diagram showing the signal flow of a position detection device according to an embodiment of the present invention, FIG. 2 is a waveform diagram showing the operating state of the same position detection device, and FIG. It is a schematic plan view which shows the arrangement|positioning state of the limit switch in an example.

Note that the following examples are merely specific examples of the present invention, and are not intended to limit the technical scope of the present invention.

As shown in FIG. 1, the position detection device of this embodiment includes an incremental rotary encoder 1 with a Z pulse,
It consists of a pulse counter 2 that counts the output pulses from the rotary encoder 1, and a plurality of limit switches LS+, LS2, etc. for fixed position detection provided within the operating range of the robot, etc., as shown in Fig. 3. ,
Each of these limit switches generates a pulse signal each time by interfering with a dock (not shown) provided on a rotating shaft, typically an output shaft of a speed reducer or the like. As shown in FIG. 2, such a limit switch for detecting a fixed position is installed at a position whose angular position from the origin is known in advance.

For example, if the limit switch LS for detecting a fixed position is used for detecting the origin, and the rotating shaft is rotating to the right in the figure, then the limit switch LS shown in Fig. If the origin is the first two pulses Z0 (see Fig. 2 (c)) after the falling signal is generated, then this Z pulse Z.

The count value of the pulse counter 2 is reset to 0 by this signal. Here, if the interval between Z pulses is n pulses, the Z pulse Z on the left side of the Z pulse Z0 shown in FIG. 2(C). The position where ' is generated (left rotation in this case) is the -nth pulse, and if the interval between pulses generated from the encoder is δθ as shown in Figure 2 fat, then the 20' pulse is at an angle of -δθ x n. It will represent the location.

Therefore, O and -n are memorized together with the number of the limit switch to be activated (LS in this case, so the number is 1), and depending on the direction of rotation of the rotating shaft, if the rotation is clockwise, 0 is set.
．． If the rotation is to the left, the value of the pulse counter can be updated to an accurate value by extracting -n and replacing this value with the current value of the pulse counter.

The method described above is a method for correcting the rotational position in the vicinity of the limit switch LSI representing the origin, but it is also possible to correct the position in the vicinity of the arbitrary position inch LS□ using the same principle.

For example, considering the first limit switch LS shown in FIG. 2 (fl), if the rotation direction is to the left in FIG. The angular position of XL' can be determined in advance.For example, if the number of Z pulses counted from the origin pulse at this time is j, the above Z□'
The position of the Z pulse corresponds to the jXnth pulse, and its angular position is δθx jXn''.In addition, when the rotation direction is rightward, the Z pulse generated next to the falling signal from the beam switch L S□ The rotational position of the pulse is δ
θ×(j+1)×n°, and these jXn and (
j+1)xn pulse number corresponding to the limit switch L
Memorize it along with the number S, and press the limit switch L.
When two pulses are input next to the falling signal of SI, the counter value corresponding to each Z pulse (in this case jXn or (j+1)Xn) is set to the current pulse counter value according to the rotation direction at that time. , and update the count value.

It is preferable to update the navigator runt value only in the "home alignment" mode. In this way, in the above embodiment, the number of limit switches for fixed point position detection is, for example, 1.
, the number of count values stored correspondingly is 2xi, and the count value corresponding to each limit switch is searched according to the rotation direction and replaced with the current position of the pulse counter. It is.

Therefore, for example, in the case of a robot, if the width is generally 3.
Since it has an operating range of about 00°, for example, by installing 11 limit switches at equal intervals, it is possible to
This means that the origin (fixed point) alignment can be performed every degree.

In the above embodiment, by providing a large number of limit switches, a large number of fixed point positions are set at which the value of the pulse counter can be updated. The origin alignment may be performed only in these cases. In this case, the amount of storage required is half that of the above embodiment. In either case, if you select a limit switch that aligns the origin, the functionality will be further enhanced. However, providing many such limit switches is disadvantageous as it complicates the wiring, so an absolute encoder is attached to the rotating shaft via a high-precision rotation transmission means such as a gear, and the output from this absolute encoder is The value of the pulse counter may be updated by taking out the stored count value using the generated pulse as a signal at a fixed point.

As mentioned above, the current absolute type encoders, which are relatively inexpensive, have a low decomposition part, but have high detection accuracy, so they are considered suitable for such uses. For example, if a 3-bit absolute encoder is used, it is possible to divide into 8 equal parts. Therefore, for example, when installed in a reducer with a reduction ratio of 80, 1/
Since one Z pulse is generated for 80 rotations, one 2 pulse corresponds to 10 rotations of the motor.

Effects of the Invention As described above, the present invention provides a device for detecting the rotational position of a rotating shaft whose rotational angle is limited to an operating limit of 360°, in which an incremental type rotary with Z pulse is provided on the motor side. An encoder, a pulse counter that counts pulse signals generated from the above-mentioned 2-pulse incremental rotary encoder, and a plurality of fixed positions provided within the operating limits of the rotary axis and whose angular positions from the origin are predetermined. When the first Z pulse is input after the pulse signal from the fixed position information generating means and the fixed position information generating means is input, the value of the pulse counter is changed according to the rotational direction of the rotating shaft at that time. This position detecting device is characterized in that it is equipped with a reset means for resetting the above to a predetermined number corresponding to the fixed position information generating means, so that it can be used in robots etc. that operate within a narrow operating range. , the origin (fixed point) can be adjusted in small increments without requiring a large space, and there is no inconvenience such as interference with the workpiece when aligning the origin, making it easier for the operator to adjust the origin each time. Since there is no need for the person to be present, it is possible to provide a position detection device with good workability.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the signal flow of a position detection device according to an embodiment of the present invention, FIG. 2 is a waveform diagram showing the operating state of the same position detection device, and FIG. Schematic plan view showing the arrangement of limit switches, No. 4
The figure is a waveform diagram showing a procedure for adjusting the origin in a conventional incremental rotary encoder with Z pulses, and FIG. 5 is a schematic plan view showing the arrangement of limit switches for detecting the origin in a conventional robot. (Explanation of symbols) 1... Incremental rotary encoder with Z pulse 2... Pulse counter LFz, LS2... Limit switch for fixed point detection.

Claims (1)

[Claims] (1) In a device that detects the rotational position of a rotating shaft whose rotational angle is limited to an operating limit of 360°, an incremental rotary encoder with a Z pulse installed on the motor side, and an incremental rotary encoder with a Z pulse described above. a pulse counter that counts pulse signals generated from the encoder; a fixed position information generating means that is provided within the operating limit of the rotating shaft and that generates information on a plurality of fixed positions whose angular positions from the origin are predetermined; When the first Z pulse is input after the pulse signal from the fixed position information generating means is input, the value of the pulse counter is set according to the rotational direction of the rotating shaft at that time, and the value of the pulse counter is set to correspond to the fixed position information generating means. 1. A position detection device comprising: reset means for resetting to a predetermined number.