KR100575124B1 - Linear Encoder for Detecting Long Span - Google Patents

Abstract

The present invention relates to a linear encoder for detecting the absolute position of the transfer device used in the linear transfer system moving a long distance in a linear manner, such as a stocker system of a logistics device or a semiconductor manufacturing equipment, more specifically, the absolute position of the transfer device The present invention relates to a linear encoder that can quickly detect an absolute position without using a time-consuming procedure such as moving to an origin to find an.

In addition, in the case of a system using the linear motor as a driving source, it is necessary to detect the relative position of the stator and the mover of the motor for speed and position control of the linear motor. However, when the precision of the relative position detection is deteriorated, the overall control characteristics are deteriorated. Accordingly, the present invention relates to a linear encoder which detects a relative position together with absolute position detection, and whose precision is also better than before.

Linear Encoder, Step Code, Code Code, Precision Position Code, Optical Sensor, Logic Device, Signal Processing Processor

Description

Linear Encoder for Detecting Long Span}

1 is a diagram showing the absolute position detection according to the existing scheme;

2 illustrates detecting an absolute position using a laser detector.

3 is a hardware configuration diagram for signal processing according to the present invention;

4 is an encoder track diagram in accordance with the present invention.

5 is a view showing a state of reading the scale of the encoder by the optical sensor

6 is a waveform diagram showing an output signal of a precision recognition code recognized by an optical sensor;

FIG. 7 is a schematic diagram showing a state of each section of the signal waveform obtained in FIG.

8 is a combination display of segment codes according to the present invention.

Fig. 9 is a waveform diagram showing an output signal of each optical sensor

10 is a software flow chart for position detection

11 is a flowchart of an interrupt routine for position detection.

12 is a table for encoding

13 is a block diagram of a logistics system using a linear motor

Fig. 14 is an exemplary diagram showing how the scale is actually displayed.

<Description of the symbols for the main parts of the drawings>

1: linear encoder 2: guide rail

3: wheel 4: stator of linear motor

5: frame of feeder 6: mover of linear motor

10: limit dog 11: proximity sensor

12: moving cart 13: target of laser position detector

14: laser position detector 20: scale

30, 32, 34, 36, 38, 40: optical shield

31: step code 33: segment code

35: code 37: precision position code A

39: Precision Position Code B45: Optical Sensor

50: signal processor 51: filter

52: logic element 55: signal processing processor

The present invention relates to a linear encoder that can quickly detect the position of the transfer device, and more particularly, it is possible to simultaneously measure the absolute position and relative position of the transfer device used in the linear transfer system moving a long distance linearly. To a linear encoder.

The conventional technology regarding the linear encoder is divided into two as follows.

First, as shown in FIG. 2, the limit dog 10 which detects the absolute position is fixed to the ground and the proximity sensor 11 is installed in the moving cart 12 as shown in FIG.

When the proximity sensor 11 returns to the position of the limit dog 10, the returned signal is detected by the proximity sensor 11, and the position value at this time is reset to make this position the absolute origin. When the moving trolley falls by a predetermined distance around the absolute origin identified above, the distance from the absolute origin is calculated and the absolute position of the moving trolley 12 is calculated.

However, the present invention has the following problems.

First, there is a problem in that the home position must be set again through the home position return even when a power failure occurs, a power failure, or a power interruption occurs.

Second, there is a problem in that excessive time is taken when the moving cart is far away due to the above cause.

Third, an encoder for detecting an absolute position uses a binary code, which has a problem in that an absolute encoder having a large number of bits must be used to recognize a long distance because the number of positions that can be recognized is small.

Another conventional technique is to use a sensor that directly detects the absolute position such as the laser position detector 14 together with the linear encoder or alone. The laser position detector 14 detects the absolute position to the target 13 at all times by converting the reflected time into a distance by irradiating a laser onto the fixed target (reflective plate) 13. That is, the distance from the laser position detector 14 is calculated using the position of the target 13 as the origin, and the absolute position of the moving cart 12 is detected.

However, in the case of the present invention, not only the responsiveness of position detection is limited, but also because the laser detection apparatus is generally used for long-range detection, there is a problem in that the position accuracy is poor at a close distance.

In addition, there is a problem that a hydraulic correction procedure or a separate limit switch is required to know the relative position between the motor and the stator of the motor.

The present invention has been made to solve the above problems, the object of the present invention is as follows.

First, the objective is to be able to detect the absolute position even after the power failure or the power is turned off even if the minimum unit is moved from the current position without origin return.                         

Secondly, the objective of the present invention is to enable accurate position discrimination without increasing the number of optical sensors even when moving over a long distance.

Third, in the case of long distance as well as short distance, it is possible to determine the position more accurately than before without increasing the optical sensor.

Fourthly, to obtain the relative position between the stator and the mover, a separate device is not necessary and the relative position can be obtained in the process of obtaining the absolute position.

In order to achieve the above object, a step code for dividing a scale into a predetermined section, a segment code for indicating a segment having a different width in each of the divided sections, a code code for determining a sign of the segment and the segment code and A scale having a precision position code for measuring the width of the code code;

An optical sensor for converting each code displayed on the scale into pulses;

It includes a signal processor for detecting the correct position by analyzing the pulse for each section.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The linear encoder of the present invention, as shown in Figure 3, the optical sensor 45 and the pulse generated by the optical sensor to recognize the scale 20 consisting of the encoder track and the code portion displayed on the scale 20 and converts it into a pulse The signal processing unit 50 is configured to process.

The signal processor 50 includes a filter 51, a logic element 52, and a signal processor 55.

The filter 51 removes noise from the output generated by the five optical sensors 50 installed in each track and inputs it to the programmable logic device 52. The logic element 52 generates data 53 and an interrupt signal 54 required by the signal processing processor 55 using respective pulse strings input from the filter 51.

In addition, the signal processor 55 recognizes a code for each section based on data input from the logic device 52.

 4 is a scale 20 of an encoder of the present invention, which is composed of five effective code portions 31, 33, 35, 37, 39 and five optical shields 30, 32, 34, 36, 38.

Here, each of the effective code portions 31, 33, 35, 37, and 39 are processed so that the optical sensor 45 can recognize the code or have a slit or blockage. The part becomes a blocked part and the white part becomes a slit.

5 is a view showing an optical sensor 45 for recognizing the code of the scale 20. The optical sensor 45 for recognizing the valid code includes the light source 46 and the light receiving element with the scale 20 therebetween. 47 are facing each other, and the light from the light source 46 is directed to the light receiving element 47. At this time, the logic 0 or 1 is recognized depending on whether the light emitted from the light source 46 is sensed by the light receiving element 47.

In the present invention, the valid code portion is largely composed of a step code 31, a segment code 33, a code code 35, and precision position codes 37 and 39. In addition, the five optical shields (30, 32, 34, 36, 38) are located between the valid code portion to allow the optical sensor 45 to correctly recognize the valid code.

The step code 31 alternates as a code for displaying a certain section 41, in this case 40 [mm] section, which is alternately 0 and 1. FIG. This code becomes a unit section for determining the absolute position, and a specific code is assigned to each section.

The segment code 33 is a code that is divided into different widths in the step code 31 and is used to distinguish the codes in the sections, respectively, and 0 and 1 are alternately engraved regardless of the arrangement order. The segment shown in FIG. 5 consists of three parts, and is represented by A, B, and C, respectively. Specific codes are assigned according to the combination of these codes, that is, the arrangement order. That is, the number of segments can be changed as needed, and accordingly the display of the segments is A, B, C, D,... Can be extended to

 The sign code 35 is a code corresponding to the segment code 33 in a 1: 1 manner and determines a sign of each segment, that is, + and-. In Figure 4, the hatched part is recognized as-and the non-hatched part as +. This code portion is used for the purpose of extending the use area of the absolute position code as described later.

 The precision position codes A (37) and B (39) are scales for measuring the precise position in each section, and 0 and 1 are engraved in the unit of 1 [mm] in the present invention. The precision position codes A 37 and B 39 are engraved to be moved 90 degrees in phase. Therefore, the pulse train generated by the optical sensor 45 can be multiplied, and the actual position measurement accuracy is 0.25 [mm].

The precision location code will be described in more detail below.

FIG. 6 is a waveform diagram showing an output signal recognized by an optical sensor of a precision position code, and FIG. 7 is a schematic diagram illustrating a state change of the signal shown in FIG.

In Fig. 6, the precision position code A (37) is displayed alternately ascending (A = 1 or B = 1) and falling (A = 0 or B = 0) at periodic intervals, and the precision position code B (39) is described above. It can be seen that the phase difference is 90 degrees with A (37).

In FIG. 7, the state of each section of the signal shown in FIG. 6 is defined, S0 is A = 0, B = 0, S1 is A = 1, B = 0, and S2 is A = 1, B = 1. , S3 is A = 0, B = 1.

In the state diagram, when A and B inputted as S0-> S1-> S2-> S3 change, the counter value increases, and when S3-> S2-> S1-> S0 changes, the counter value decreases. Here each state must move to the next state only. That is, the movement from S0 directly to S2 is not allowed.

As shown in FIGS. 6 and 7, when one cycle is 1 mm, the signal of the precision position code is changed by a quarter cycle (0.25 mm), and the counter increases or decreases as the constant sequence is changed. I can see it goes.

This phase shift will also be used to determine the direction of travel. That is, by detecting the rising edge (A = 1 or B = 1) of each pulse to determine the forward or reverse direction by which one is input first, this is implemented by hardware logic in the logic element 52 of FIG. do.

FIG. 8 shows a combination of distinguishable arrangements in a section 100 consisting of three segments 101, 102, and 103. Each segment has a different width, denoted A, B, and C here. These three segments can be six combinations as shown in FIG. 8 according to the arrangement order, and in addition, the code code 35 shown in FIG. 4 is arranged in a 1: 1 correspondence to each segment.

As described above, each corresponding code may be set to 0 or 1, and if the corresponding code is 0, it may be set to lowercase letters a, b, and c. If the corresponding code is 1, it may be assigned to uppercase letters A, B, and C.

The segment and code allocated as described above can be combined as follows.

 (A, B, C) (A, C, B) (B, A, C) (B, C, A) (C, A, B) (C, B, A)

 (a, B, C) (a, C, B) (B, a, C) (B, C, a) (C, a, B) (C, B, a)

 (A, b, C) (A, C, b) (b, A, C) (b, C, A) (C, A, b) (C, b, A)

 (A, B, c) (A, c, B) (B, A, c) (B, c, A) (c, A, B) (c, B, A)

 (a, b, C) (a, C, b) (b, a, C) (b, C, a) (C, a, b) (C, b, a)

 (A, b, c) (A, c, b) (b, A, c) (b, c, A) (c, A, b) (c, b, A)

 (a, B, c) (a, c, B) (B, a, c) (B, c, a) (c, a, B) (c, B, a)

 (a, b, c) (a, c, b) (b, a, c) (b, c, a) (c, a, b) (c, b, a)

가지 경우의 표시가 가능하나 본 코드는 3개 코드와 1개의 부호 코드의 조합으로

가지 경우를 표시할 수 있음을 보여주고 있다. As you can see, 48 segments can be generated with 3 segments and 1 sign code. In the above combination, the first combination is a case where all segments are combined only with a + sign, one and two down are -sign combinations, and the last is a combination of only -signs. Typically, four bits in binary code

It can be displayed in one case, but this code is a combination of 3 codes and 1 sign code.

It can be shown that there are cases.

FIG. 9 shows the pulse train output by the five optical sensors 45 on the time axis. The segment code 60, the segment code 61, the code code 62, the precision position code A 63 and the B 64 are shown in FIG. )

The section code 60 alternately generates 0 and 1 each time the section is changed to distinguish each section. In addition, the segment code 61 can be combined with the code code 62 to distinguish each segment in the interval.

As shown in the figure, the segment code 61 is displayed in lower case when the code code is 0, and in capital letters when the code code is 1. Through this, even if the segment of the same waveform can be seen that differently recognized depending on whether the code code is 0 or 1.

10 shows a software flow diagram of a signal processing processor 55 for processing pulse input from an optical sensor.

This software, which is executed at regular time intervals, starts (70) and first reads the five status signals T0, T1, T2, T3, and T4 from the logic element 51 (71). Where T0 is the direction determination signal generated by the logic element, T1 is the interval pulse 60, T2 is the segment pulse 61, T3 is the sign pulse 62, T4 is the precision position pulse A 63, B 64. The pulses are multiplied by the combination of. This flowchart is for the case with five segments (A, B, C, D, E) as shown in FIG. Next, the state of T1 is checked (72), and if T1 is 1, execution is performed toward (81) or otherwise (73). While T1 is 0 (73), that is, the following program is executed for one interval.

Since there are five segments in one section, T2 creates five rising or falling edges, and each time an interrupt is generated and two counters are used to determine the width of T2, that is, the width of the segment pulse and the width of the sign pulse, that is, the width of T4. Counting by the number of pulses generates the following five count combinations.

(n1, s1), (n2, s2), (n3, s3), (n4, s4), (n5, s5)

That is, the number of pulses n1-n5 and the sign s1-s5 corresponding to each segment are determined (74).

  Next, for each combination, as shown in FIG. 10, the code is found using the segment index ni and the code index si (75). Here, the state of the direction input T0 is determined (76) and the program is executed in the forward direction (78) and in the reverse direction (77) in order to determine whether the generated code starts from the left side or the right side first.

According to the direction, it is possible to generate a 5-digit code by performing the calculation as (77) and (78). This code is a unique code assigned to each absolute position to check the absolute position section through a table or an appropriate operation (79). The absolute position section divides a moving position in a predetermined unit in advance and assigns a unique code number to each of the divided positions. For example, the code at the point A is 91234, the code at the point B is 43212, and the code at the point C is 42331.

Therefore, if the absolute section is recognized only by one section to determine where the current position is, from the next section, the absolute position can be confirmed by only adding or subtracting according to the moving direction by the unit section interval from the already recognized absolute position section. (80).

For example, if the initial position is set to 91234, the branch B is 43212, and the branch C is 42331, and the absolute position needs to be reconstructed due to a power outage, the current position If the position code is determined to be 91234 by moving a section in, the current absolute position becomes the point A, and after that, it moves as already set. Therefore, it is no longer necessary to return to the origin to know the absolute position.

The relative distance in this section can be known simply by counting T4 pulses.

FIG. 11 is a software flow chart which is processed by interrupt separately from the flow of the program of FIG. Since there are five segments in one section, the interval between each edge of the T2 pulse is measured using the T4 pulse, and the sign of the corresponding segment is also read to generate five (segment pulse number, sign) combinations.

12 is a table for generating interval indicator ti from the combination (number of segment pulses, sign). According to this table, the (segment pulse number, sign) combination is recognized as one 5-digit code for each section, and this code is 1: 1 matched with the absolute position.

Here, the number of segment pulses was determined as follows. If the interval is 40 [mm] and the T4 pulse, that is, the precision position pulses A and B, is 1 [mm], the half cycle of the multiplied pulse becomes 0.25 [mm] and the overall precision is 0.25 [mm]. do. Thus, 40 / 0.25 = 160 [pulse], and assigning each segment a different width results in 16 + 24 + 32 + 40 + 48 = 160. These are symbols A, B, C, D, and E. The widths are 4 (0.25 × 16) mm, 6 (0.25 × 24) mm, 8 (0.25 × 32) mm, 10 (0.25 × 40) mm, It corresponds to 12 (0.25 x 48) mm. Therefore, the code can be easily identified by counting the pulses between the T2 edges.

The linear encoder according to the present invention as described above can be used in a linear motor and will be described in detail as follows.

First, the transfer system using the linear motor shown in FIG. 13 uses a linear motor composed of a stator 4 and a mover 6 as a driving source. The stator 4 of the linear motor has a recessed groove in the moving direction at regular intervals, and the mover 6 has a structure in which a winding is wound around the magnetic body between the permanent magnets to maintain a constant interval.

At this time, the stator 4 is fixed on the frame 1 and the guide rails 2 are installed at both ends, and then the object is fixed by fixing the frame 5 d and f motors of the transfer device integrated with the wheel 3 thereon. Will move. In addition, in order to detect the position, the linear encoder 7 is generally fixed to the frame 5 and used.

At this time, if the sensor is manufactured with the same pitch of the linear motor and the sensor section, the absolute position and the relative position can be known at the same time, making it easier to control the current and thrust of the motor, and always know the absolute position of the mover 6. Therefore, unnecessary homing operation can be avoided and there is no accumulation of error, thus improving the accuracy of the work.

14 shows the scale 20 of the linear encoder, which can be manufactured to a desired length through printing or laser processing.

Effects on the linear encoder according to the present invention made as described above are as follows.

First, in case of restarting after a power failure or power off, the absolute position can be known only by the movement of the minimum unit section without the procedure of confirming the absolute position such as zero point return, thereby saving time for the zero point return.

Second, as mentioned above, frequent homing is not necessary, so there is little possibility of colliding with other mobile trucks.

Third, even if the detection distance is different, since the long distance can be recognized with a small number of bits, it is economical because no additional optical sensor is required.

Fourth, since it is a non-contact type using an optical sensor, it does not generate dust in a clean area such as a semiconductor processing line.

Fifth, if the sensor section is determined and implemented in the same way as the pitch of the linear motor, the current control and the thrust control according to the relative positions of the stator and the mover of the motor become easier and the error does not accumulate. Do not.

Claims (5)

A segment code for dividing the scale into a predetermined section and displaying a step code and a segment code indicating a segment having a different width within each divided section, a code code for determining a sign of the segment, and a width of the segment code and the code code A scale with a precision position code; An optical sensor for converting each code displayed on the scale into pulses; A linear encoder for position detection, characterized in that it comprises a signal processor for analyzing the pulse of each section to detect the correct position. The method of claim 1, Wherein the signal processor is a linear encoder for position detection usable for long periods, characterized in that to give a code for each section from the output of the optical sensor and to detect the absolute position section from the given code. The method according to claim 1 or 2, And the signal processing unit can detect the relative position by counting the number of fourth pulses. The method of claim 1, The sign of the code code is a linear encoder for position detection usable for long intervals, characterized in that consisting of + or-. The method according to claim 1 or 4, The code of the segment code and the code code correspond to each other one-to-one, so that the number of codes that can be used by extending the segment and the segment code together is extended, and the linear encoder for position detection can be used for a long section. .

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