JPS6224726B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an encoder device, and particularly to an encoder device that can perform error correction.

Conventional devices of this type store the amount of cumulative error that has been measured in advance in the form of a cam or template, move the cam along with the scale to detect the error value at that measurement point, and calculate the amount of error according to the amount of error. The accumulated error is corrected using a phase synthesis circuit configured such that the synthesis amount changes continuously (for example, Japanese Patent Publication No. 52-69346).

This type of device has problems in terms of structure and cost.

Therefore, in order to overcome these drawbacks and obtain an encoder device that can perform highly accurate correction by adding a relatively small number of electronic devices, an encoder device having the configuration shown in Fig. 1 can be considered. .
In FIG. 1, a glass scale 1 having lattice stripes of a constant pitch is provided movably, and a displacement detector 2 photoelectrically detects the movement of the scale 1 and converts it into an electrical signal. The output of the displacement detector 2 is connected to a resistor divider 3 using an inverting amplifier 4. Note that this connection method will be described later. The tap output of the resistor divider 3 becomes the input of a semiconductor switch 5, and the output of the switch 5 is connected to be applied sequentially to a trigger circuit 6, a pulsing circuit 7, a counter 8, and a digital calculator 9, and the output of the calculator is displayed. The output is displayed on the device 10. In addition, component parts 1, 2, 6, 7, 8
This constitutes a known photoelectric linear encoder.

3, 4, and 5 constitute a phase shifter.

Next, let us look at the operation. Inside the displacement detector 2, there is a grating with the same pitch as the scale 1. When the grating is superimposed on the scale 1, the amount of light transmitted changes sinusoidally as the scale 1 moves. By using two gratings shifted by 1/4 pitch, a signal S1 with a phase of 0° and 90° is generated.
Obtain S2. Inverting amplifier 4 is connected to the output of displacement detector 2.
is inserted and the signal S1 is inverted to create a 180° signal, and the three signals are input to the resistor divider 3 whose terminal resistance value is appropriately adjusted. Then, a signal with an intermediate phase can be obtained as shown in FIG. The tap output of the resistor divider 3 which takes out signals out of phase with each other becomes the input of the semiconductor switch 5. The semiconductor switch 5 changes the signals D1 and D2 from the computer 9 to 00,
By changing like 01, 10, 11, the first
This is a two-circuit semiconductor switch that can switch four terminals from 0 to 3 in the second group. When the switch is changed, the phase difference between the outputs S4 and S5 and S1 and S2 can be changed from 0 to +67.5 degrees while maintaining the phase difference between them at 90 degrees. The outputs S4 and S5 are applied to a trigger circuit 6, where they are converted into rectangular waves. The rectangular wave output is converted into a pulse train by the pulsing circuit 7. By counting the pulse train with a counter 8, the amount of movement of the scale 1 can be digitized.

From the lattice stripes to the pulse generation is shown in FIGS. 3a to 3d. When the semiconductor switch 5 is switched, the positional relationship between the grating shown in FIG. 3a and the sine wave shown in FIG. 3b changes.
The position of pulse generation therefore changes, as is clear from FIG. 3d. Assuming that the counter 8 is reset at the origin position of the scale 1, the count value of the counter 8 indicates the absolute position of the scale 1. The calculator 9 uses the counted value to perform calculations in accordance with a pre-stored cumulative error table for scale 1, and then changes the output signals D1 and D2 to correct the error. At the same time, errors of one grid pitch or more can be corrected by directly adding a correction value to the count value of the counter 8. The corrected value is displayed on display device 1.
Displayed as 0.

The encoder device described above has the advantage that it can be made smaller at a lower cost because it requires no mechanical load by simply adding an electronic device to a conventional linear encoder. However, in this method, since the phase shifter is constructed by a resistor divider, a complicated resistor circuit is required, and there is a problem that a correction signal cannot be obtained continuously.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an encoder device that is not only capable of performing correction with higher accuracy than conventional encoder devices, but also capable of obtaining continuous correction signals at a lower cost.

FIG. 4 shows an embodiment of the present invention. In this embodiment, instead of the phase shifter composed of the resistor divider 3, inverting amplifier 4, and semiconductor switch 5 shown in FIG. 1, an inverting amplifier, a variable gain amplifier 11, and a resistor combiner 12 are connected as shown in FIG. It has a phase shifter composed of.
Other parts are the same as in FIG. 1 and are given the same reference numerals. Note that the signal _S3 in Figure 4 is the signal in Figure 1.
The signal S ₄ in FIG. ₄ corresponds to the signal S ₅ in FIG. The variable gain amplifier 11 changes the degree of amplification according to the digital signals D1 and D2 from the computer 9. On the other hand, the resistance combiner 12 creates signals with two phases of 45° and 135° from signals with three phases of 0°, 90°, and 180°. Component parts 4, 12, 13
performs the same function as components 3, 4, and 5 in FIG.

The embodiment of FIG. 4 operates in substantially the same manner as the embodiment of FIG. 1, but differs from the embodiment of FIG. 1 as follows. The counter 8 outputs a numerical value indicating the absolute position of the scale 1 as in the case of FIG.
compares the numerical value with the cumulative error correction table of scale 1 stored in advance in the storage device inside the computer, and reads out the correction value. The calculator 9 changes D1 and D2 according to the correction value and determines the gain ratio of the variable gain amplifier 11. FIG. 5 is a vector diagram showing how the phases of S3 and S4 change depending on the gain ratio of the variable gain amplifier 11. In this way, as in the case of FIG. 1, error correction can be performed by changing the phases of the signals S3 and S4 according to instructions from the computer 9. The method by which the calculator 9 determines D1 and D2 is that it is possible to directly store the data corresponding to D1 and D2 in the correction table,
In response to more complex corrections, the scale position and D1,
A method of determining D1 and D2 by storing the relationship of D2 in the form of a mathematical formula and performing calculations within the calculator 9 can also be considered.

This embodiment shown in FIG. 4 allows finer correction than in the case of FIG. 1.

As described above, according to the present invention, not only the accumulated error of the scale can be corrected with high precision, but also the error of the machine tool etc. to which the scale is attached can be corrected at the same time. Furthermore, if a temperature sensor and an A/D converter are added to the digital computer, temperature correction can be performed at the same time.

Furthermore, since the phase of the signal is changed by determining the gain ratio of the two variable gain amplifiers, (a) there is no need for a complicated resistor circuit, resulting in lower costs; and (b) there is no need for a switch circuit. (c) Faster response speed and more stable operation,
There are other effects.

The present invention is applicable not only to photoelectric type but also to magnetic type, electromagnetic type,
Can be applied to electrostatic length and angle measurement devices.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an encoder device that solves the drawbacks of conventional encoder devices, Fig. 2 is a diagram showing an example of a resistor divider, Fig. 3 is an explanatory diagram of the process from lattice stripes to generation of a pulse signal, FIG. 4 is a block diagram of an embodiment of the present invention, and FIG. 5 is a vector diagram showing the output of a computer for error correction. Explanation of symbols of main parts, 1... Scale, 2... Displacement detector, 3... Resistance divider, 4... Inverting amplifier, 5
...Semiconductor switch, 6...Trigger circuit, 7...Pulsing circuit, 8...Counting circuit, 9...Digital computer, 1
0...Display device.

Claims (1)

[Claims] 1. A displacement detector 2 that outputs two sinusoidal signals S ₁ and S ₂ with a 90 degree phase difference according to the relative displacement with respect to the scale, and receives one of the two sinusoidal signals as input. 1st
a variable gain amplifier 11; an inverting circuit 4 inputting one of the two sinusoidal signals; a second variable gain amplifier 11 inputting the output signal of the inverting circuit; 1 Vector composite signal _S3 with the output signal of the variable gain amplifier
and a vector composite signal of the other of the two sinusoidal signals and the output signal of the second variable gain amplifier.
S ₄ , a vector synthesizing means 12 for outputting S4; a counting means for inputting two vector synthesized signals from the vector synthesizing means and outputting a position signal indicating the absolute position of the displacement detector with respect to the scale; and a display device. and storing in advance a correction value corresponding to the accumulated error of the scale in correspondence with the absolute position, reading out the correction value according to the absolute position signal from the counting means, and based on the read correction value. ,
A calculator that adjusts the gains of the first variable gain amplifier and the second variable gain amplifier, and further causes the display device to display a display based on the counted value of the counting means. error-corrected encoder device.