JPS6117913A - Rotary encoder - Google Patents

Abstract

PURPOSE:To measure an absolute angle without contacting by arranging the sheet which makes the PN simbol for angle detection in patterns to the shape of a circumference, by reading one part of the symbols by the reading sensor being fitted to a rotary shaft and by deciding which position of the circumference. CONSTITUTION:The count of a PN symbol generating clock is started simultaneously with the angle convertor 5 outputting a PN symbol generation starting signal 7 to a PN symbol generator 4, and after the generator 4 setting the initial stage value to the value equivalent to a rotary angle 0 deg., the generation of PN signal is started from the phase thereof. A comparator 3 compares one by one the reading data of N bits length that a detector 2 outputs with reading from a PN symbol sheet 1 and the N bits of PN symbols, and if both of them coincide with each other, a coincidence output 6 is fed to the convertor 5. The convertor 5 further reads the count value of the clock and outputs with converting to a rotary angle data.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a rotary encoder for detecting a rotation angle.

[Prior art and its drawbacks]

Conventionally, rotary encoders for detecting angles include those that measure resistance ratios using potentiometers, and those that count slits provided on the circumference. However, since potentiometers are contact type, they have problems with stability.On the other hand, slit type potentiometers count the number of slits from a reference position, so counting errors result in measurement errors, and only relative angles can be obtained. The disadvantage was that it could not be done.

[Purpose of the invention]

The present invention solves the above-mentioned drawbacks of the conventional method, and its object is to provide a means for obtaining an absolute angle without contact.

[Structure and effects of the invention]

The present invention includes a sheet in which a PN code arranged along the inner circumference of a rotary encoder is turned into an o-turn, a detector attached to a rotating shaft so that a part of this sheet can be read without contact, and a PN code generator. A comparator that compares the read sequence with the contents of the PN code generation register, and a converter that converts the comparison result into angle information.

According to the present invention configured as described above, since the reading of the PN code is performed without contact, stable reading is possible, and since the read PN code indicates an absolute position, it is possible to read the PN code in a non-contact manner. The absolute angle can be obtained from the detector output without the need for

[Explanation of Examples]

Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a cross-sectional view of a rotary encoder, where ■ is a PN code sheet, and 2 is a detector for reading the code no♀ turn.

The detector rotates around the rotation axis, and the opposite PN code?
You can always read the turn.

The PN code pattern can be read by either an optical method or a magnetic method, and in the case of the optical method, the pattern can be read by a CCD or a photodiode array, and in the case of the magnetic method, the pattern can be read by a magnetic spatula F or a Hall element.

As an example of the PN code and Q-turn, a digital code sequence converted into a bar code as it is can be used.

Figure 2 shows the entire electric circuit configuration by expanding the PN code sheet [1] in the rotary encoder shown in Figure 1, and 3 represents the code string read from the code sheet and P
A comparator for comparing the contents of the N code generator register 4,
When these code strings match, a match signal 6 is sent to the angle converter 5.
Output.

The angle converter 5 supplies a PN code generation start signal 7 to the PN code generator 4, and the P'N code generator 4 generates a PN code from the reference phase determined by this start signal 7 and sends it to the comparator 3. A PN code subsequence 8 is output. This PN code has a total code length of 2n-1 bits, where n is the number of stages of the shift register constituting the PN code generator 4, and within this total code length, subsequences of n bits or more with different starting points are all different. . (This is a + turn. The present invention utilizes this property to obtain the absolute value of the position (angle). 9 is a clock generator.

FIG. 3 shows a time chart of each signal in the circuit of FIG. Next, the operation of each part will be explained in detail according to the time chart shown in FIG.

The angle converter 5 outputs the PN code generation start signal 7 to the PN code generator and simultaneously starts counting the PN code generation clock.

The PN code generator 4 sets the initial value of the generation register to a value corresponding to the rotation angle x by the start signal 7, and then starts generating the PN code from that phase.

The comparator 3 compares the N-bit length read data outputted from the detector 2 one by one with the N-bit length of the PN code, and outputs a coincidence output 6 to the angle converter 5 if they match.

The angle converter reads the count value of the PN code generation clock using the coincidence signal 6, converts it into rotation angle data, and outputs it.

Detector 2 detects 2 of the code pattern changes on the PN code sheet.
The code pattern is read by an array sensor arranged at twice the density.

The number of array sensors is 2N+ for the comparison PN code length N.
All data is loaded into a 2N+1 bit shift register in IQ parallel.

Shift register output is 1, 3.5..., 2N+
Only 1 and odd numbers are output to the comparator 3 in parallel.

Comparator 3 compares the detector output with PN code subsequence 8 and stores the result. Next, issue a shift command to detector 2,
Shift the contents of the shift register of the detector by 1 bit. The output before being shifted is SQ', and the output after shifting is 81.

The comparator performs the same comparison for Sl as for SO. Furthermore, S2 is obtained by another 1-bit shift command and a similar comparison is made. From the results of these three comparisons, 5O1S2 and PN
If the code subsequences match, let it be “matching pa”, Sl, 82
The case where the and PN code subsequences match is defined as a "(+) half-bit match." In this way, rotation angle information can be obtained within a half-bit error range of the PN code and Q turn sheet.

FIG. 4 is a time chart showing these comparison signals. In this example, the S1 output and the S2 output match the PN code subsequence, and from this, a (+) half-bit-scattered output is obtained.

To obtain angle information from these matching signals, the following equation can be used, assuming that the PN code sequence length is M bits, the measurement angle range is C and the PN code generation clock count value when the θτ comparator outputs the matching signal. Angle information η is obtained.

■1 However, in order to improve measurement accuracy, a longer PN code sequence is required.
It is only necessary to increase the resolution of the PN code sheet.

In this way, it is possible to realize a rotary encoder that can always obtain rotation angle information regardless of the initial state.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a detector of a low-return encoder according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing the overall configuration of a low-return encoder equipped with the detector of FIG. 1, and FIG. 1 is a time chart of signals of each part of the device, and FIG. 4 is a time chart showing the processing concept of a comparator for the detector output in FIG. 1. 1...PN code sheet, 2...detector, 3...
・Comparator, 4... PN code generator, 5.
... Angle converter, 6... Match signal, 7...
- PN code generation start signal, 8... PN code segment, 9... PN code generation clock generator.

Claims (1)

[Claims] A sheet patterned with PN codes used for angle detection is arranged in a circumferential manner, and a part of the code on the sheet is read by a pattern reading sensor attached to a rotating shaft so as to rotate along the circumference, and the entire circumference of the sheet is read. A rotary encoder characterized in that it is equipped with means for determining the position of the rotary encoder and measuring the rotation angle.