JPH07111358B2 - Absolute terrain position detection device - Google Patents

Description

The present invention relates to an absolute rotary encoder, that is, an absolute terrain rotary position detecting device.

[Conventional technology]

As shown in Fig. 2, the absolute terrain rotation type position detector is
Each coordinate position is coded on a rotor (code plate) 1 attached to an input shaft 5 and written as a light and dark pattern, and the code plate 1 and a fixed slit plate 4 for improving detection accuracy are sandwiched between the light emitting diode 3 and the light emitting diode 3. By making the photodiodes 2 face each other, the position information corresponding to each coordinate position can be obtained from the photodiodes 2 as the code plate 1 rotates due to the movement of the position detection target.

As a code written in the code plate 1, a single distance code (unit distance code) has been conventionally used. This is such that only one bit always changes between adjacent two sets of codes due to a change in address. When such a code is used, when a code in which two or more bits change at the same time, the inversion of one bit is detected at the time of code detection, but the state that the other bits are not yet inverted is inevitable. This is because it occurs and an incorrect code is output. This single distance code is desirable as the code used in the absolute terrain position detecting device for the above-mentioned reason.

The most well known of these single distance codes is the Gray code. Gray code is one-to-one with pure binary code
Corresponding to, and mutual conversion is easy. This is an advantage of the Gray code, and by converting it into a pure binary number, it becomes a code suitable for inputting as data to a computer or the like. (With the Gray code, it is difficult to distinguish the size of two codes. It's inconvenient). However, the code most easily understood by the user is a decimal number, and the code used to represent a decimal number with 0 and 1 is BCD (Binary).
Coded Decimal) code. This is a decimal number converted into a binary number for each digit, and mutual conversion of decimal ← → BCD code is easy. Table 1 shows the decimal numbers and their corresponding Gray codes, pure binary numbers, and BCD codes.

Therefore, using a Gray code output type encoder
A user who wants to obtain decimal data may convert in the order of gray, pure binary, BCD code, decimal. The problem here is that the conversion from pure binary to BCD code is not easy in a logic circuit. Therefore, it is convenient if the encoder output is BCD code from the beginning.
A CD code output type encoder has been proposed.

The conventional BCD code output type uses a read-only storage element (ROM) for code conversion. ROM
When one address is specified on the input side, the data stored in that address is output. As an example, when converting the gray code in Table 1 into a BCD code, the BCD code corresponding to the address indicated by the gray code is 0101 for the address indicated by 0011, 00101, for the address 0111, and so on. You can use the ROM that stores. FIG. 3 shows the configuration of a 360-division (one-revolution) BCD code output encoder constructed by this method.

1 to 5 in FIG. 3 are the same as those in FIG. 2, and are a code plate, a photodiode, a light emitting diode, a fixed slit plate and an input shaft, respectively. Further, 6 is an amplifier, 7 and 8 are ROMs, and 9 is a buffer. In this encoder, the light and dark parallel codes given to the photodiode 2 by the code plate 1 and the fixed slit plate 4 are waveform-shaped by the amplifier 6 and converted into the logic code of 0,1 to be the input address of the ROM 7,8. . The ROMs 7 and 8 output data (BCD code in this case) corresponding to the input and output the data via the buffer 9 to the outside.

[Problems to be solved by the invention]

The problem with the conventional device of FIG. 3 is that it requires two ROMs. ROM is more expensive than other circuit elements, and since it is large, two circuit boards are conventionally required and the cost is high. The reason why two ROMs are required here is not because the storage capacity is small, but because there are only eight output data ports on the market. In the BCD code, one decimal digit is represented by a four-digit (4-bit) binary number, so for example 360
For division, 10 outputs are required (the output is represented by 000 to 359, so the highest digit can be 00, 01, 10, 11 in four ways,
Two is fine).

On the other hand, since the input data port is 2 ⁸ <360 <29, ⁹ ports are required. However, since commercially available ROMs (in this case, P-ROMs capable of writing data) are designed for computers, most of them have 8-bit outputs even if they have more than 9 inputs. Therefore, the lower two digits in ROM7,
I had no choice but to configure ROM8 to handle the most significant digit.

Several methods have been considered to solve the above problems. Taking the example below, the output is sequentially output every two digits by time division.

A custom IC (mask ROM) with 9 inputs and 10 outputs is manufactured.

 Only the most significant digit is output by a general logic circuit.

Etc. However, the cost is rather increased,
Was not used because the initial cost was too high. Requires only one ROM to handle the lower two digits, but as long as a normal Gray code code plate is used, all bits of information are needed to determine the output of the most significant digit, which complicates the logic circuit configuration. turn into.

The present invention is intended to realize the above method with a simple configuration by configuring the code plate pattern so that the output of the most significant digit can be determined with a small amount of information.

[Means for Solving Problems] The present invention is directed to an absolute number terrain position detecting device in which the necessary division number is 10
A code plate is provided, which is divided into blocks for each 0 division and fractional blocks of 100 or less and is represented by a single distance code, and a code plate having a track for identifying each of these blocks. While taking the most significant digit of BCD code output from the logic circuit,
The feature is that the lower two digits are taken out as a BCD code output from one ROM.

[Work]

According to the solving means of the present invention, the output of the most significant digit can be determined only by the track information for identifying the block, and the track information of the lower digit is unnecessary, so that the above method is realized with a simple logic circuit configuration. be able to.

〔Example〕

An example of the light-dark pattern of the code plate according to the present invention is developed and shown in FIG. In this embodiment, the case where the total number of divisions is 360 is shown.

In FIG. 1, blocks 11 to 14 are composed of seven tracks T _{0 to} T ₆ , and are divided into 100 addresses according to the light and dark pattern of each track (only block 14 is 6
0 division). The code pattern of each block is defined to satisfy the following conditions.

Adjacent codes in the same block must differ by only one bit. That is, it must be a single distance code.

All bits (T _{0 to} T ₆ ) of adjacent codes across the boundary with other blocks must be the same. The reason for this is one block identification track (T ₇ or T ₈ ) at the boundary with other blocks.
Changes, so T ₀ ~ T ₆ must be equal to all T ₀ ~
This is because the T ₈ as a whole does not have a single distance code.

Further, since the block 11 and the block 14 are adjacent to each other in the rotation type, the code at the beginning of the block 11 must be the same as the code at the end of the block 14.

There are many kinds of such codes, but an arbitrary number of code strings can be created by utilizing the symmetry of the Gray code, for example. To briefly explain this, in the Gray code string in Table 1, when two pieces are removed from the center like 7 and 8,6 and 9,5 and 10, the remaining codes become a single distance code string. This is utilized (see Japanese Patent Application No. 58-23650 for details).

In this way, 100 code strings obtained by removing the central 28 from the 128 gray code strings corresponding to 0 to 127 are represented by [A] and assigned to the block 11. Next, a code string [A '] in which [A] is arranged in reverse order is assigned to the block 12. Of course, the end of [A] is equal to the beginning of [A '], so the above condition is satisfied. Similarly, block 13 can be assigned [A]. Since the block 14 is divided into 60, as in the case of [A], a code string created by removing 68 gray codes from 128 gray codes is arranged in the reverse order to form [B].

In this way, 360 code strings consisting of the blocks 11 to 14 can be obtained, but since the same code exists in each block, the track 15 for block identification is provided. Since two tracks 15 are required, four-division gray codes are assigned as T ₇ and T ₈ , respectively. In this way, a 360-divided code plate is obtained. Table 2 shows the relationship between these blocks and codes (the gray code column in Table 2 originally contains a code consisting of 0 and 1 but the corresponding 10
It is shown in decimal. ).

FIG. 4 shows an example in which a 360-division encoder is configured by the code plate of FIG. In FIG. 4, 1 is a code plate, 2 is a photodiode, 3 is a light emitting diode, 4 is a fixed slit plate, 5 is an input shaft, and 6 is a waveform shaping amplifier. RO
M17 receives the light reception signals of each track T ₀ through T _8, the lower 2
The digit is output as a BCD code. Track T representing the most significant digit
The signals of ₇ and T ₈ are converted into a BCD code by the exclusive OR circuit 10. The exclusive OR circuit 10 actually performs conversion from gray to pure binary, but as shown in Table 1,
Since BCD and pure binary are equal, this is output as a BCD code.

The BCD code signal of each digit is output via the buffer 19.

Thus, the circuit of FIG. 4 is the same as the conventional circuit shown in FIG. 3 in terms of the output, but in FIG.
Since only one unit is required, cost can be reduced while saving space. Although not shown in the figure, in the conventional type, a synchronization signal was used to connect the 359 and 0 addresses in addition to the originally necessary signal (the relationship between the 359 and 0 addresses is a single distance code). (It was necessary because the data collapsed), but in the embodiment of FIG. 4, the required minimum number of bits is sufficient.

[Modification]

Although the number of divisions is 360 in the above embodiment, other numbers of divisions are possible. For example, block 14 in FIG.
That would be 400 divisions. If the number of blocks is further increased, the number of divisions can be increased, but if the number of divisions is larger than 1000 (output 0 to 999), it is necessary to convert the block identification signal into 2 digit BCD.

In addition, in the above embodiment, the case of the rotary type is shown,
The same can be done with a straight line type. In addition to photoelectric type, magnetic type,
The present invention can be applied to a brush type detection mechanism.

〔The invention's effect〕

As described above, according to the present invention,
Since a code plate having a track expressed by a single distance code by dividing it into blocks for every 100 divisions and fractional blocks of 100 or less and a track for identifying each of these blocks was provided, the most significant digit is a simple logic. It can be taken out as BCD code output by the circuit configuration. Therefore, since the ROM only needs to handle the lower two digits, it is sufficient to use only one commercially available ROM. In the past, since there were two or more ROMs, there was no choice but to use two substrates, which was a factor of cost increase. In addition, the cost of the ROM itself for all electric components was not small. According to the present invention, the circuit board is 1
It becomes a single piece, and it is possible to realize a compact size and a large cost reduction.

Further, if the code plate is constructed in the pattern as shown in the embodiment, the conventionally required synchronization signal (timing signal at the time of changing from the maximum address to the zero address, in the conventional code plate, the single distance Since the sign is broken and two or more bits are inverted, this is unnecessary.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention and is an expanded view of a bright and dark pattern of a code plate. FIG. 2 is an internal configuration diagram of the absolute terrain rotation type position detecting device. FIG. 3 is a block diagram of an electric circuit of a conventional BCD output encoder. FIG. 4 is a configuration diagram of an electric circuit of a BCD output encoder using the code plate of FIG. 1 ... Rotor (code plate), 2 ... Photoelectric element (photodiode), 3 ... Light source (light emitting diode), 4 ... Fixed slit plate, 5 ... Input shaft, 11-14 ... Block, 15 …
… Block identification track, 20… Highest digit code conversion gate.

Claims (1)

[Claims] 1. A required number of divisions is a block for every 100 divisions, and 1
A code plate having a track represented by a single distance code divided into fractional blocks of 00 or less and a track for identifying each of these blocks is provided, and the most significant digit of each block is logically determined by the signal of this code plate. Absolute terrain position detection device characterized by taking out as the BCD code output from the circuit and taking out the lower two digits as the BCD code output from one ROM.