JPH05248893A - Backup type absolute position encoder - Google Patents

Abstract

PURPOSE:To obtain an inexpensive absolute position encoder capable of performing backup for a long time by battery constitution. CONSTITUTION:First dense rotary slits and second rough rotary slits are provided on a rotary disc 25 and a circuit counting dense signal and a circuit counting rough signals are provided. At the time of backup, the circuit is operated at a speed capable of counting only the rough signals and, at the time of the start of operation, an industrial robot is operated on the basis of the content of a rough quantity-of-rotation counter 27b (that is, at a rough absolute position). As the result of operation, an encoder is rotated and a dense quantity-of-rotation counter 27a is set to an accurate value at the point of time when the rough signal from the rotary slits changes at first and the robot is operated at a dense absolute position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backup absolute position encoder used for industrial robots and the like.

[0002]

2. Description of the Related Art Conventionally, in an industrial robot, an absolute code for detecting a rotation angle within one rotation and a Z phase for outputting a signal once per rotation are marked on a rotating disk so that the operating power is cut off (hereinafter referred to as backup). The absolute position encoder that counts this Z-phase signal is mainly used in the electric circuit built in the encoder. However, since the configuration is complicated and expensive, the absolute code is abolished and an all-backup absolute position encoder that counts the signal of the incremental encoder by an electric circuit inside the encoder is commercialized.

This backup absolute position encoder is an optical encoder, as shown in FIG.
The light from D1 passes through a slit group 5 of a rotary slit 3 provided on a rotary disk 2 and a fixed slit 4 at the rear to reach a light receiving element 6, and the rotation of an encoder is taken out as an electric signal. The output of the light receiving element 6 is detected by the rotation amount counter of the signal processing IC 8 on the control board 7 by counting the number of slits in the rotation amount counter.

Further, although the motor of the industrial robot is provided with a brake and its rotation is stopped when the power source is cut off, the rotation of the encoder cannot be avoided due to the impact on the robot arm. For this reason, the backup absolute position encoder is a device that backs up with a battery or the like to operate a necessary electric circuit on the control board 7 so that the absolute position can be known even when the power is cut off and stopped. Normally, during backup, the LED 1 is driven intermittently to reduce current consumption.

FIG. 4 is a block diagram showing the configuration of an electric circuit in a conventional backup absolute position encoder. In FIG. 4, the light from the LED 1 passes through the slit group 5 and reaches the light receiving element 6. The outputs of the light receiving elements 6a and 6b are converted into rectangular wave signals by the waveform shaping circuits 11a and 11b. This signal is called an A-phase output or a B-phase signal, and becomes an output signal to the outside when operating power is applied (hereinafter referred to as normal operation). The A-phase output and the B-phase signal are turned into an up signal a and a down signal b by the quadrupling circuit 12 and counted by the backed up rotation amount counter 13. Further, for the purpose of reducing power consumption, a timing generation circuit 14 for intermittently driving the LED 1 during the backup operation is provided. This is LED1
This is because the current consumption of is overwhelmingly large. A signal processing IC 7 is composed of the waveform shaping circuits 11a and 11b, the quadrupling circuit 12, the rotation amount counter 13 and the timing generation circuit 14.

FIG. 5 shows the A phase and B phase outputs and the LED drive signal p.
Shows the relationship. In FIG. 5, in order to correctly count the A-phase output and the B-phase output, the period T of the LED drive signal p is calculated from the minimum time when the change points of the A-phase output and the B-phase output appear.
It is necessary that ₀ (hereinafter referred to as the sampling period) be short.

[0007]

However, in the above-mentioned conventional backup type absolute position encoder, if the sampling period T ₀ is lengthened in order to reduce the power consumption during backup, the upper limit number of revolutions that can accurately count the rotation of the encoder. N ₀ is to be small. The sampling period T ₀ depends on the battery capacity and the length of the required backup time.
When deciding, but the upper limit rotation speed N ₀ is determined, there is a problem that it is difficult to obtain a practically sufficient upper limit rotation speed N _0.

The present invention solves the above-mentioned conventional problems. When the drive power supply of the industrial robot is cut off to enter the backup state, a practically sufficient upper limit rotation speed N ₀ and backup time are standard. An object is to provide a backup type absolute position encoder that can be realized with a battery configuration.

[0009]

In order to solve the above-mentioned problems, the backup type absolute position encoder of the present invention is
A backup absolute position encoder having a first rotation amount detecting means for detecting the rotation amount of the rotary disc by interposing a rotary slit provided in the rotary disc between the light emitting means and the light receiving means of A second rotation amount detection for detecting a rotation amount of the rotating disc by providing the rotating disc with a rotation slit coarser than the rotation slit, and interposing the coarse rotation slit between the second light emitting means and the light receiving means. And means for intermittently driving at least the second light emitting means in a cycle necessary to correctly detect the rough rotary slit in the backup state.

[0010]

With the above structure, in the backup state, at least the second light emitting means is intermittently driven by the driving means and rotated by the second rotation amount detecting means in a long cycle necessary for correctly detecting the coarse rotation slit. Since the rotation amount of the disk is detected, the current consumption of the encoder can be reduced by lengthening the intermittent drive cycle of the light emitting means during backup, and the backup time can be extended with a standard battery configuration The practical upper limit of rotation speed is guaranteed even when the driving power of the robot is shut off and the backup is performed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an electric circuit in a backup absolute position encoder according to an embodiment of the present invention. In FIG. 1, the backup power supply V _B is connected to the timing generation circuit 22 via a series circuit of LEDs 21a and 21b, and the timing generation circuit 22 intermittently drives the LEDs 21a and 21b during backup. Further, the backup power source V _B is used as the light receiving elements 23a, 23b, 23.
Waveform shaping circuits 24a, 24 via c and 23d in parallel, respectively.
b, 24c, 24d, respectively, the light from the LED 21a is received by the light receiving elements 23a, 23b respectively, and the waveform shaping circuits 24a, 24b respectively perform waveform shaping to form A-phase and B-phase rectangular waves, Similarly, the light from the LED 21b is received by the light receiving elements 23c and 23d respectively, and the waveform shaping circuit 24c,
At 24d, the waveforms are respectively shaped to form C-phase and D-phase rectangular waves. These LEDs 21a, 21b and light receiving elements 23a, 23b,
A rotary disk 25 is provided between 23c and 23d. The rotating disk 25 has a second rotating slit for generating C-phase and D-phase outputs, in addition to a first rotating slit for generating A-phase and B-phase outputs.
Is additionally provided, and the second rotary slit has a slit configuration that is sufficiently coarse as compared with the first rotary slit that generates A-phase and B-phase signals.

The waveform shaping circuits 24a and 24b are quadruple circuits.
It is connected to the AB rotation amount counter 27a via 26a, and the A-phase and B-phase outputs from the waveform shaping circuits 24a and 24b are quadruple circuits 26.
At a, it becomes an AB up signal and an AB down signal and is counted by the AB rotation amount counter 27a. Also, the waveform shaping circuit 24c,
24d is connected to the AB rotation amount counter 27b through the quadruple circuit 26b, and the C-phase and D-phase outputs from the waveform shaping circuits 24c and 24d become the CD up signal and the CD down signal in the quadruple circuit 26b and the AB rotation amount counter. Counted at 27b. In this way, from the LEDs 21a, 21b, the AB rotation amount counters 27a, 27
Up to b, rotation amount detecting means for detecting the rotation amount of the rotary disk 25 is provided, and the rotation amount counter is an AB rotation amount counter.
27a and a CD rotation amount counter 27b, and counts up and down signals respectively corresponding thereto. That is, a coarse second rotary slit is provided on the rotary disk 25 in addition to the dense first rotary slit, and a circuit for counting dense signals and a circuit for counting coarse signals are provided.

Further, the adder 28 comprising an OR gate which receives the CD up signal and the CD down signal from the quadruple circuit 26b has its output end connected to the AB rotation amount counter 27a. It can be said that the content of the CD rotation amount counter 27b is correct even if the encoder is rotated at the upper limit rotation speed N ₀ in the backup state by considering the driving cycle T ₁ of the LEDs 21a and 21b. There is a possibility that the contents of the will be misaligned. Therefore, a function is provided to reset and restore the AB rotation amount counter 27a at the rising and falling edges of the sum signal of the CD up signal and the CD down signal. Therefore, immediately after turning on the drive power of the industrial robot, the CD rotation amount counter
It is necessary to operate the robot a little with the contents of 27b (that is, the coarse absolute position) and to return the contents of the AB rotation amount counter 27a to the correct value before taking in the absolute position. The above timing circuit 22, waveform shaping circuits 24a, 24b, 24c, 24
d, 4 times circuit 26a, 26b, AB rotation amount counter 27a, 27
A signal processing IC 29 is configured by b and the adder 28.

FIG. 2 is a waveform diagram of an output signal in each main part of the electric circuit of the backup type absolute position encoder of FIG. 1, in which the phases A to D when the encoder makes one rotation at a constant speed.
The relationship between the phase output signal and the LED drive signal P is shown.
In FIG. 2, the repetition period of the C phase and the D phase is set to 1/4 rotation for simplicity. The period T1 of the LED drive signal P is C
By setting the phase and the change point of the D phase to be equal to or less than the minimum time (that is, 1/16 rotation) at which the change point appears, the C phase and the D phase are correctly counted.

With the above configuration, the circuit is operated at a speed capable of counting only the rough signal at the time of backup, and the industrial robot is operated at the start of the operation based on the content of the rough rotation amount counter 27b (that is, at the rough absolute position). Let Then, as a result of the operation, the encoder rotates and the dense AB rotation amount counter 27a is set to a correct value at the time when the coarse signal from the coarse rotary slit first changes, and the robot is operated at the dense absolute position.

That is, the encoder of the industrial robot does not rotate at a high speed because its rotation is suppressed by the brake in the backup state when the drive power is cut off, but some rotation such as shock and vibration is inevitable. Therefore, the absolute position should be known by operating the encoder even when it is stopped. At this time, in the backup state, the LEDs 21a and 21b are intermittently driven by the driving means at a long cycle necessary to correctly detect the coarse rotary slit, thereby reducing the current consumption of the encoder. When the driving power of the industrial robot is turned on and the operating power is supplied, the contents of the AB rotation amount counter 27a corresponding to the first rotation slit are ignored, and the CD rotation amount counter corresponding to the second rotation slit is ignored. The robot is operated with the contents of 27b (that is, with a coarse absolute position). Then, the AB rotation amount counter 27a is returned to the initial value at the signal change points of the C-phase output and the D-phase output, and thereafter, the operation at the complete absolute position becomes possible.

Therefore, when the drive power of the industrial robot is cut off to enter the backup state, a practically sufficient upper limit rotation speed N ₀ and a long backup time can be realized with a standard battery configuration. Thus, an inexpensive backup absolute position encoder can be obtained.

[0018]

As described above, according to the present invention, it is possible to provide an inexpensive absolute position encoder which guarantees a rotation speed sufficient for normal use during backup and extends the backup time.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an electric circuit in a backup absolute position encoder according to an embodiment of the present invention.

FIG. 2 is an output signal waveform diagram in an electric circuit of each main part of the backup absolute position encoder of FIG.
It is a timing diagram of D phase output and LED drive signal P.

FIG. 3 is a configuration diagram of a conventional backup absolute position encoder.

FIG. 4 is a block diagram showing a configuration of an electric circuit in a conventional backup absolute position encoder.

5 is a waveform diagram of an output signal in an electric circuit of each main part of the backup absolute position encoder of FIG.
It is a timing diagram of a phase output and an LED drive signal.

[Explanation of symbols]

 21a, 21b LED 22 Timing generation circuit 23a, 23b, 23c, 23d Light receiving element 24a, 24b, 24c, 24d Waveform shaping circuit 25 Rotating disk 26a, 26b Quadruple circuit 27a, 27b Rotation amount counter 28 Signal adder 29 Processing circuit IC

Claims (1)

[Claims] 1. A backup absolute system having a first rotation amount detecting means for detecting the rotation amount of the rotary disc by interposing a rotary slit provided in the rotary disc between the first light emitting means and the light receiving means. A position encoder,
A second amount of rotation for detecting the amount of rotation of the rotary disc by providing the rotary disc with a coarser rotary slit than the rotary slit, and interposing the coarse rotary slit between the second light emitting means and the light receiving means. A backup-type absolute position encoder provided with a detection means and a drive means for intermittently driving at least the second light emitting means at a cycle necessary to correctly detect the rough rotary slit in the backup state.