JPH044532B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an absolute address type photoelectric position detection device.

2. Description of the Related Art Rotary encoders are conventionally known as devices for optically reading positions in machine tools and the like. This uses a code plate to detect the brightness change of the analog value of the mechanical rotational position of the shaft using a photoelectric method, and digitally encodes it.There are two types of encoders: incremental encoder and absolute encoder. The present invention relates to an absolute encoder that performs position detection using absolute addresses.

The inside of the absolute encoder is constructed as shown in FIG. At each angular position, a code corresponding to the angular position is engraved on the rotational code plate 1 as a light and dark pattern using gray code, BCD code, or the like. A light emitting diode 2 and a photodiode 3 are disposed facing each other on the rotary code plate 1 with the plate sandwiched therebetween. When the rotary code plate 1 rotates as the input shaft 5 rotates, some of the light emitted from the light emitting diodes passing through the fixed slit plate 4 is transmitted and some is blocked according to the pattern. The transmitted light is received by the photodiode 3, and by detecting the light receiving position, the rotational position of the shaft is determined as an absolute address, and thereby the position of the object to be detected is detected.

In such a device, each position data inscribed as a bright and dark pattern on the rotary code plate 1 is composed of a plurality of bits in the radial direction. For this reason, when position data changes over multiple bits at once, it may vary slightly due to errors in pattern engraving or mounting eccentricity between the input shaft 5 and the center of the pattern engraved on the rotation code plate 1. This may result in erroneous data being detected during the optical detection process. Therefore, the code engraved on the rotary code plate is a Gray (single distance binary) code that does not generate ambiguous codes during photoelectric reading; in other words, only a 1-bit change occurs when the code of an adjacent address changes. An absolute address type rotational code plate is manufactured using a built-in absolute encoder, and the position data detected by the built-in absolute encoder is code converted into the required final output code using a memory circuit such as ROM or P-ROM. decode or change to appropriate function)
However, when outputting as a digital code, it is necessary to synchronize the readout timing to prevent misreading due to variations in variation between each bit.

This invention uses a memory circuit to convert position data obtained from an absolute encoder (including both rotary type and linear type) into a code in an absolute address type photoelectric position detection device to obtain data in a desired format. Erroneous detection is prevented by synchronizing the timing of reading data using a bit detection signal.

The present invention will be described in detail below with reference to embodiments of the accompanying drawings.

FIG. 2a is a linear representation of the bright and dark pattern engraved on the rotary code plate of the absolute encoder. The shaded area is the light blocking area,
The other parts are transparent parts. Here, the case where Gray codes are used is shown.

In this case, the synchronization signal is generated by extracting the edges (rising and falling) of the pulse signal (referring to the detection signal of the bright and dark pattern) at each bit and taking the logical sum of the edges, as shown in Figure 2b. Obtainable. In other words, the signal width of the synchronization signal is set longer than the conversion time by the memory circuit,
Synchronization of the read signal is applied to the outside at the falling edge of this synchronization signal. As a result, when a rising edge or falling edge is detected in any bit, the timing delayed by a predetermined period until the next rising edge or falling edge is detected in any bit is obtained from the data obtained from the memory circuit. This prevents erroneous reading due to variations in changes between bits of the memory circuit.

FIG. 3 is an example of a circuit that implements the method of FIG. 2. In FIG. 3, 11 is a rotation code plate (a plate-shaped member), 12 is a light emitting diode, 13 is a photodiode (12 and 13 constitute a photocoupler), 14 is a fixed slit plate, and 15 is an input shaft. The light emitted from the light emitting diode 12 is received by the photodiode 13 via the transparent portion 11a of the rotary code plate 11 and the fixed slit plate 14. The output of the photodiode 13 corresponding to each bit is shaped into a square wave signal by a comparator amplifier 20. This comparison amplifier 20
The portion up to this point corresponds to the detection means. Comparison amplifier 2
The pulse signal of each bit output from 0 is a ROM (read only memory) corresponding to a memory circuit.
21. The ROM 21 performs code conversion, and reads out data corresponding to the output data of the comparator amplifier 20 as an address signal.
Code conversion in ROM21 converts data input in Gray code to binary code (pure binary code).
What is decoded into BCD (binary coded decimal code) or an appropriate function, that is, a function value corresponding to the rotation angle of the input shaft 15 (sin, cos, tan, sin ^-1 , cos ^-1 ,
tan ^-1 , log, e ^x, etc.) into binary code or BCD code, etc. can be selected as appropriate.
The output data of ROM21 is buffer driver 2
2 as an electrical digital code output.

In the synchronization signal generation circuit 23 (synchronization signal generation means), an edge trigger mono multivibrator 24
is for extracting the edges (rising and falling edges) of the pulse signal at each bit of the comparator amplifier 20. The edges extracted for each bit are logically summed by an OR circuit 25, and this signal is used as a synchronizing signal for reading output data. That is, as described above, synchronization of the read signal is provided externally at the falling edge of this synchronization signal. This results in
Since the output of the ROM 21 is read out at a timing outside of the bit change, erroneous detection is prevented. still,
The time width of this synchronizing signal is set to be longer than the code conversion time of the ROM 21 and shorter than the period until the edge of the next pulse signal occurs as shown in FIG. 2b. The time width can be adjusted by the pulse width of the one shot pulse in the edge trigger monomultivibrator 24.

As mentioned above, in Fig. 3, a function is provided to output a synchronization signal to prevent misreading of the final output code. It is possible to set all bit outputs to "1" (or "0") state for the code conversion time (synchronized with the falling edge of the synchronization signal), or to set the buffer driver circuit 22 in the encoder to It is also possible to provide a latch circuit to generate and output a synchronized code within the encoder, and in this case, the code reading synchronization signal shown in FIG. 3 is not output to the outside of the encoder. An example of the signal processing described above is shown in FIG.
Furthermore, if an element with a latch (D-type flip-flop with clock synchronization) is used for the buffer driver 22, the output of the buffer driver 22 shown in FIG. 3 can have a completely synchronized absolute code. In this case as well, a code reading synchronization signal to the outside of the encoder is not required.

Although the above embodiment shows the case where the present invention is applied to a rotary encoder, a linear scale (a light and dark pattern is arranged in the moving direction of the object to be detected, photocouplers are placed opposite to each other with the pattern in between, and their positional relationship is detected) The present invention can also be applied to a device that detects the position of an object by changing it linearly as the object moves.

As explained above, according to the present invention, since the absolute encoder synchronizes when reading each bit signal, there is no possibility that erroneous data will be detected.

Furthermore, since there is no need to provide a dedicated synchronization bit for generating a synchronization signal on a plate-shaped member, the plate-shaped member can be the same as the conventional one, and the device does not become larger.

[Brief explanation of drawings]

Fig. 1 is a perspective view schematically showing the internal structure of an absolute rotary encoder, Fig. 2 is a diagram explaining how to achieve synchronization in the embodiment shown in Fig. 3, and Fig.
The figure is a block diagram showing one embodiment of this invention.
This figure is a block diagram showing an example of a modification of the usage of the synchronization signal in FIG. 3. 1, 11... Rotation code plate (plate-shaped member), 11
a... Transparent part, 2 and 3, 12 and 13... Photocoupler (2, 12... Light emitting diode, 3, 13
... photodiode), 4, 14 ... fixed slit plate, 5, 15 ... input shaft, 20 ... comparison amplifier, 21 ... ROM (memory circuit), 22 ... buffer driver, 23 ... synchronization signal Generation circuit (synchronization signal generation means).

Claims (1)

[Scope of Claims] 1. The information of each bit of a code representing each address information is carved into a plate-like member as a combination of a part that transmits and a part that blocks light, and the code is inserted with the plate-like member in between. A photocoupler is placed at a position corresponding to each bit of the code, these photocouplers detect each bit information of the code, and a code composed of a combination of detection signals of these bits is generated between the plate-shaped member and the photocoupler. a detection means for outputting absolute address information representing the relative positional relationship of the detection means; a memory circuit for converting the code outputted from the detection means into a code of an appropriate format; and each outputted from the detection means. The rising and falling edges of the bit detection signal are detected, and when a rising edge or falling edge is detected in any bit,
Next, synchronization for instructing a timing that is delayed from the code conversion time by the memory circuit as the read timing of the data obtained from the memory circuit until a rising or falling edge is detected in any bit. An absolute address type photoelectric position detection device comprising synchronization signal generation means for generating a signal.