JPH03120420A - Absolute encoder - Google Patents

Abstract

PURPOSE:To obtain the absolute encoder which is decreased in the number of signal cables and has high practicability by providing a parallel-series converting means, a transmitting means, and a series-parallel converting means. CONSTITUTION:A one-track type absolute code which represents (n)-bit position information is formed on a code plate 11. A detection part 9 is provided with (n) sensors which read the momentary relative positions of the code plate 11 and detection part 9 in their relative motion out of the absolute code pattern on the code plate 11 as an (n)-bit code signal in parallel and outputs the (n)-bit position information on the relative positions of the code plate 11 and detection part 9 according to the code signal. The parallel-series converting means 1 arranges codes which are detected by the sensors in parallel on a time base according to a specific clock to generate a signal and the transmitting means 6 transmits the converted code to the series-parallel converting means 2 as electric pulses propagated in a cable, an FM radio wave propagated in a space, etc. The means 2 reconverts the received serial signal into the (n)-bit parallel signal.

Description

[Detailed Description of the Invention] Field of Application in the CA Industry] The present invention is suitable for application to, for example, controlling the rotation angle of a motor in a precision positioning device such as an X-Y stage.
Regarding absolute encoders with improved practicality.

C. Prior Art] A code plate with a unique code pattern corresponding to each rotation angle or position coordinate is detected by an appropriate sensor, and the rotation angle of the rotation axis or the position coordinate of the linearly moving body is output as an electrical signal. The use of absolute encoders is expanding with the progress of equipment automation in various fields, but in some fields including semiconductor manufacturing equipment, higher resolution and higher resolution are required as equipment operations become more complex and precise. , a high number of bits as well as high reliability and practicality are required.

Figure 2 shows the patent application filed earlier by the applicant in 1983-17.
An example of the absolute encoder according to the invention of No. 2557 is shown, and the coordinate track 11 is
This is an absolute encoder that outputs relative position coordinate values between the measuring section 9 and the coordinate track 11 to the data lines D1 to D5 of the coordinate conversion memory 4 by reading a 5-bit absolute code from the coordinate conversion memory 4.

The coordinate track 11 in this conventional example is a 1-track type 5-bit absolute code expressed in a light and dark pattern, and this code is a reflected light provided in a measuring section 9 that moves relative to the coordinate track 11 in the direction of the arrow. Five bits are detected in parallel by detection type sensors S1 to S5. The measurement unit 9 also includes a Schmitt trigger 18 for shaping the waveform of the 5-bit code signal detected by the sensors S1 to S5. On the other hand, the arithmetic unit 1O includes a matching unit 3 that performs input adjustment (including level and isopedance) of parallel code signals sent from the measurement unit 9, and an address line A1.
A coordinate conversion memory 4 is provided which parallel-converts manually input bit signals and outputs them to data lines D1-D5.

Further, the output connector 19 of the measurement section 9 and the input connector 20 of the calculation section 10 are connected by five signal cables 21 to 25.

In this conventional example, the sensors S1 to S5 simultaneously read five bits of the absolute code of the coordinate track 11, and each bit signal is calculated as a parallel signal via the output connector 19, signal cables 21 to 25, and input connector 20. The coordinates are inputted to the matching unit 3 of the section 10, where they are input adjusted, and then converted into practical coordinate values, such as a BCD code, in the coordinate conversion memory 4.

[Problem to be solved by the invention] Measurement unit 9 of the above-mentioned 5-bit absolute encoder
and the calculation unit 10 are connected by five signal cables 21 to 25 for transmitting 5-bit parallel information. 10 is connected with a larger number of parallel signal cables depending on the number of bits.

With the increasing resolution of angle detection performance required in the field of semiconductor manufacturing equipment, encoders with an even greater number of bits are being manufactured. This makes the cable bundle less flexible, hinders encoder handling, and complicates fabrication and repair. In addition, disconnections occurred, reducing reliability, and the connectors and the like became huge, which hindered miniaturization of the entire encoder system. Furthermore, if priority was given to the flexibility of the cable, problems such as susceptibility to noise due to incomplete noise shielding and inability to handle high frequencies occurred, impairing practicality.

An object of the present invention is to provide a highly practical absolute encoder with a reduced number of signal cables.

[Means for Solving the Problems] The absolute encoder according to the present invention includes a code plate (11) in which an absolute code pattern for giving a position signal is formed in one track, and a code plate (11) that is movable relative to the code plate and that can encode the code. A one-track absolute encoder comprising a detection section (9) provided with a predetermined plurality of sensors for parallel detection, and a parallel-to-serial conversion means for converting the code detected by the sensor into a serial signal. (1), transmission means (6) for transmitting the output of means (1), and serial-to-parallel conversion means (2) for converting the serial signal transmitted by means (6) into a parallel position signal.
It has been established that

[Function] In the absolute encoder according to the present invention, a one-track absolute code that provides n-bit position information is formed on the code plate (11) as a pattern that is a combination of transparent parts and opaque parts, for example. On the other hand, the detection part (
9) involves reading in parallel the momentary relative positions of the code plate (11) and the detection unit (9) as n-bit code signals from the absolute code pattern of the code plate (11). sensors are provided. However, if a plurality of sensors are provided per bit in order to improve detection accuracy, the total number of sensors provided is n or more. The detection section (9) outputs n-bit position information indicating the relative position of the code plate (11) and the detection section (9) according to the parallel n-bit code signals detected by these sensors.

In the absolute encoder according to the present invention, parallel -
The serial conversion means (1) converts the codes detected in parallel by the sensors into serial signals by arranging them on the time axis according to a predetermined clock. The transmission means (6) transmits the code converted into a serial signal to the next serial-to-parallel conversion means (2) as an electric pulse propagating through a cable, an FM radio wave propagating in space, or the like. The serial-parallel conversion means (2) is
It converts the received serial signal into an n-bit parallel signal again, and it can be returned to the n-bit code format detected by the sensor, that is, the 1-track absolute code format, but it is not possible to change the input format to the next stage. Accordingly, it is practical to use a signal format such as a BCD code.

[Example] An example of the present invention will be described with reference to the drawings. This embodiment is an attempt to reduce the number of signal cables by applying the present invention to the absolute encoder described in the prior art section.

FIG. 1 shows a schematic configuration of an absolute encoder according to an embodiment of the present invention, and similarly to the conventional example, the sensor S1
By reading the 5-bit absolute code from the coordinate track 11 using ~S5, the coordinate transformation memory 4
The measurement unit 9 and the coordinate track 1 are connected to the data lines DI to D5.
This outputs the relative position coordinate value with respect to 1.

The coordinate track 11 in this embodiment is a 1-track type 5-bit absolute code expressed in a light and dark pattern, and this code is a reflected light provided in a measuring section 9 that moves relative to the coordinate track 11 in the direction of the arrow. Five bits are detected in parallel by detection type sensors s1 to s5. The measurement unit 9 also includes a shift register 1 that once stores the 5-bit code signal detected by the sensors S1 to S5 and sequentially transfers each bit signal of the code signal to the output line according to the clock from the oscillator 5. Sensor S1~S
an oscillator 5 that generates a first clock for accumulating code signals in the shift register 1 at a position avoiding code pattern boundaries where the output of the oscillator 5 becomes unstable; and a second clock for transferring each bit signal at predetermined time intervals. Equipped with.

This oscillator 5 detects a control track (not shown) consisting of an incremental pattern formed in parallel with the coordinate track 11 with another sensor (not shown), and performs the synchronization control of each clock as described above. On the other hand, the arithmetic unit 10 has a shift register 2 that once accumulates the serial signals transferred from the measurement unit 9 and outputs them all at once to five output lines according to the first clock from the oscillator 5, and a shift register 2 that outputs the serial signals transferred to the address lines A1 to A5. A coordinate conversion memory 4 that parallel-converts input bit signals and outputs them to data lines D1 to D5, and an address line A of the coordinate conversion memory 4! - A matching box 3 that adjusts the input input to A5 (including level and impedance). Further, the output connector c9 of the measurement section 9 and the input connector C10 of the calculation section io are connected by a signal cable 6.7.

Now, in this embodiment, the 5-bit code signals detected in parallel from the coordinate track 11 by the sensors S1 to S5 are taken into the shift register 1 according to the first clock, and then output into one output according to the second clock. Output as serial information on the line. This output is connected to connector C9.
, signal cable 6, and connector CIO to the shift register 2, where it is taken in and stored as the original parallel code signal. The shift register 2 rewrites the signal on each output line into the code signal accumulated every first clock, and this 5-bit parallel signal is input-adjusted by the matching unit 3 and sent to the address lines A1 to A5 of the coordinate conversion memory 4. data line D1 after being converted into practical coordinate values.
- Output to D5.

According to this embodiment, in addition to requiring fewer signal cables to transmit code signals as serial information,
Since the codes are detected in parallel, the relative position coordinates of the coordinate track 11 and the measurement unit 9 can be determined without having to move relative to each other even when the power is turned on. It has the advantage that by converting a code signal consisting of a solitary code, a code signal in an easy-to-use format such as an absolute order BCD code or a bleed code can be obtained.

[Effects of the Invention] The absolute encoder according to the present invention includes a parallel-to-serial conversion means (1) on the signal sending side and a serial-to-parallel conversion means (2) on the signal receiving side, and converts the code signal in the transmission means (6). Since the signal is transmitted as a serial signal with each bit signal arranged on the time axis, the number of channels required for the transmission means (6) is reduced.

For example, when a cable is used as the transmission means (6), even if complete noise shielding is performed, the cable is thin and flexible, making it easy to handle the encoder and simplifying its manufacture and repair. In addition, reliability is improved because disconnections are less likely to occur, and practicality is also improved, such as making it easier to downsize the entire encoder system together with the necessary connectors.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a general configuration including a signal system circuit of an absolute encoder according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing a general configuration including a signal system circuit of a conventional absolute encoder. [Explanation of symbols of main parts] S1 to S5...Sensor 6.7...Signal cable 1.2...Shift register

Claims (1)

[Scope of Claims] A code plate (11) in which an absolute code pattern giving a position signal is formed in one track, and a predetermined plurality of sensors that are movable relative to the code plate and detect the codes in parallel. 1 consisting of a detection section (9) provided with
A track-type absolute encoder, comprising: parallel-to-serial conversion means (1) for converting the code detected by the sensor into a serial signal; transmission means (6) for transmitting the output of the means (1); An absolute encoder characterized in that it is provided with serial-to-parallel conversion means (2) for converting the serial signal transmitted by (6) into a parallel position signal.