JPH05176575A - Speed detecting method based on encoder signal - Google Patents

Abstract

PURPOSE:To ensure the detection frequency of speed detection, and to improve the accuracy of detecting speed without being subject to the effect of the mounting error of a detection means. CONSTITUTION:A first time T1 obtained by multiplying a count value J by 100musec is stored in a first time memory in S20, and a period ST acquired by adding a second time T2 previously stored in a second time memory and the first time T1 is stored in a period memory in S21. The speed of a motor is arithmetically operated on the basis of the period ST and a fixed angle and the speed value V obtained is stored in a speed memory in S22. The motor is driven and controlled so that the speed value V stored in the speed memory reaches set speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed detecting method based on an encoder signal, and more particularly to a method for detecting the speed of a slit plate each time the encoder signal from the detecting means rises or falls.

[0002]

2. Description of the Related Art Conventionally, a photo encoder (optical encoder) system is generally used to detect the rotational speed of a drive shaft of an electric motor or an engine or a rotary shaft of a driven system driven by these drive shafts. Has been adopted. That is, a circular and thin disk plate in which a plurality of slits are formed at predetermined intervals in the circumferential direction is fixed to a drive shaft of a motor, and an optical system sensor provided with a light emitting element and a light receiving element is provided with these slits. Is detected, and the rotation speed of the motor is detected based on the encoder signal output from this sensor.

By the way, when a plurality of slits are formed in the circumferential direction at intervals of approximately twice the width of the slit, encoder signals from the sensor are read at the beginning and end of each slit, and the encoder is read. Every time the signal falls (switches from "H" level to "L" level) immediately preceding rise (switches from "L" level to "H" level)
From this to the fall, the H level time of the H level period is obtained, the rotation speed of the slit plate, that is, the motor is detected based on this H level time, and at every rise of the encoder signal, from the immediately preceding fall to this rise. The L level time of the L level period is calculated, and the rotation speed of the motor is detected based on this L level time. However, the mounting position of the sensor is adjusted so that the H level time and the L level time are equal.

[0004]

As described above, when the encoder signal is read at each of the beginning and the end of each slit through the sensor and the rotation speed is detected based on these H level time and L level time, In order to equalize the H level time and the L level time of the encoder signal, the width dimension of the slit and the slit interval are designed in consideration of the optical system characteristics of the sensor, so that a high level technology is required for manufacturing the slit plate. In addition, a great amount of labor is required for the mounting work of mounting the sensor with high accuracy so that the H level time and the L level time of the encoder signal become equal, and further, as shown in FIG. 1
When the H level time becomes longer by the error time t as shown by the dotted line, there is a problem that an error occurs in the detection speeds respectively calculated based on the H level time and the L level time.

An object of the present invention is to provide a speed detection method based on an encoder signal, which can shorten the speed detection cycle time and improve the accuracy of the detection speed without being affected by the mounting error of the detection means. Especially.

[0006]

A velocity detecting method based on an encoder signal according to the present invention detects a plurality of slits formed in a slit plate at predetermined intervals in a circumferential direction or a linear direction, and detects the slits. In the speed detecting method for detecting the speed of the slit plate using the encoder signal from the means, the encoder signal is read at each start and end of each slit, and the previous time is read every time the encoder signal rises from "L" to "H". From the rising of this time to the rising of this time, the speed of the slit plate is detected using this cycle, and every time the encoder signal goes from “H” to “L”, the previous falling to the current rising The period until the descent is obtained, and the velocity of the slit plate is detected by using the period.

[0007]

In the velocity detecting method based on the encoder signal according to the present invention, the encoder from the detecting means is provided for each of the start and end of the plurality of slits formed at predetermined intervals in the circumferential direction or the linear direction on the slit plate. The signal is read,
For each rising edge of this encoder signal from "L" to "H", the cycle from the previous rising edge to this rising edge is obtained, the speed of the slit plate is detected using this cycle, and the "H" level of this encoder signal is detected. For each trailing edge from "L" to "L", the cycle from the previous trailing edge to the current trailing edge is obtained, and the speed of the slit plate is detected using this cycle. Here, as shown in FIG. 10, even if the error time is included in the H level time due to the variation in the mounting accuracy of the detecting means, the cycle (H
The level time + L level time) or the cycle from the previous fall to the current fall is not affected by the error time, so that the detection speed accuracy of the slit plate due to this cycle can be greatly improved. Further, since it is not affected by this error time, the slit plate can be easily manufactured without considering the optical system characteristics of the detecting means, and the mounting operation of the detecting means can be greatly simplified.

[0008]

According to the velocity detecting method based on the encoder signal of the present invention, as described in the section [Operation], the encoder signal is read at each of the start and end of each slit and the rising edge of the encoder signal is obtained. Every period or every fall, the speed of the slit plate is detected by the period, so the error time is not affected for this period, and the accuracy of the detection speed of the slit plate can be greatly improved. The slit plate can be easily manufactured without considering the system characteristics, the mounting work of the detecting means can be greatly simplified, and the speed can be detected at each rising and falling of the encoder signal. In addition, the speed detection cycle time can be shortened.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, 1 provided on the electronic typewriter
This is a case where the present invention is applied to a speed detection method for detecting the rotation speeds of two DC motors. As shown in FIGS. 1 and 2, side wall plates (machine frames) 2 are provided on both left and right ends inside the casing of the typewriter 1, and the platen 3 disposed between the pair of side wall plates 2 is A line feed motor (see FIG. 6) 39 is rotatably supported by both side wall plates 2 in the vicinity of both ends of the platen shaft 4, and via a driven gear (not shown) fixed to the left end of the platen shaft 4.
And is driven to rotate by a platen drive mechanism (not shown).

Between the pair of side wall plates 2, a guide shaft 5 and a guide member 6 which is substantially U-shaped in side view are further arranged in parallel with the platen 3. Next, the guide shaft 5 and the guide member are arranged. The carriage 7, which is supported by the carriage 6 so as to be movable in the left-right direction, will be described with reference to FIGS. Between the guide shaft 5 and the guide member 6, a pair of plate-shaped and substantially rectangular main frames 8 are arranged in the front-rear direction at a predetermined distance in the left-right direction. The upper ends of the first supporting portion 10 and the second supporting portion 11 of the supporting member 9 supported by the shaft 5 so as to be movable in the left-right direction and rotatably, and both of these supporting members are inserted as spacers between the main frames 8. Pins 12 and 13 are fixed to the upper ends of the parts 10 and 11 from the outside, respectively. The pair of main frames 8 constitutes the carriage body 14.

Next, the printing mechanism 15 will be described.
A DC motor 16 is supported by the main frame 8 on the right side in a state in which the DC motor 16 is prevented from rotating, and a drive shaft 17 of this motor 16 is inserted through both main frames 8 and extends to the left. Is located inside the main frames 8 from the side of the motor 16 and has a generally side-viewed side view cam 1 for printing.
8, an encoder disk 19 for detecting the rotation speed of the motor 16, a ribbon supply cam 22 for stepwise feeding the print ribbon PR, and a raising cam 21 for raising and driving the holder member 32 to the erasing position. Are fixed respectively. A cam body 20 is composed of the printing cam 18, the ribbon supply cam 22, and the lifting cam 21, and the ribbon supply cam 22 and the lifting cam 21 are integrally formed.
1 and 4 show the print start position of the print cam 18.

As shown in FIG. 4, a plurality of slits 19a are formed in an annular shape on the outer peripheral portion of the encoder disk 19 at intervals of approximately twice the slit width, and these slits 19a are detected. A photo interrupter 36 for fixing is fixed to the left main frame 8. That is, the photo interrupter 36 outputs an encoder signal to the input / output interface 85 of the control device C at each of the start end and the end of the slit 19a which is moved by the rotation of the encoder disk 19. However, the slit 19a is about 2.
They are arranged at 4 ° intervals.

At the upper ends of the rear ends of both main frames 8, a central portion of a rotary lever 23 and a lower end portion of a link 24, which are substantially V-shaped when viewed from the side, are pivoted by pins 25 and 26, respectively. The print hammer 27 which is supported and arranged in the front-rear direction so as to face the platen 3 is pivotally attached to the upper end of the link 24 at the rear end thereof, and is rotated at the center in the front-rear direction. It is pivotally attached to the upper end of the lever 23 so as to be rotatable. Further, the cam follower 2 is attached to the front end of the turning lever 23.
8 is rotatably attached to the rotary lever 2 so that the cam follower 28 always contacts the cam surface of the printing cam 18.
A tension spring 29 is attached to the upper end of the link 3 and the lower end of the link 24.
Is stretched. Reference numeral 30 is a daisy wheel rotatably driven by a wheel drive motor (see FIG. 6) 37 and a wheel drive mechanism (not shown), and reference numeral 31 is a ribbon cassette accommodating the print ribbon PR, and reference numeral 3
Reference numeral 2 denotes a holder member on which a ribbon cassette 31 is placed and which can be vertically swung via a support shaft 34 on an auxiliary frame 33 pivotally supported by a guide shaft 5 so as to be movable in the left-right direction. The carriage 7 is reciprocally driven in the left-right direction along the platen 3 via a drive wire by a carriage drive motor (see FIG. 6) 38 and a drive mechanism (not shown).

As shown in FIG. 4, the curved cam surface on the outer side of the printing cam 18 has a large radius enlargement ratio in the substantially first half portion in the sliding range in which the cam follower 28 slides. The radius expansion rate is very small in the approximately latter half portion including the striking portion where the cam follower 28 slides when the platen 3 strikes the platen 3. Moreover, the printing cam 18 is configured so that the printing hammer 27 can be pressed against the platen 3 even after the printing hammer 27 is hit.
The curved cam extends from the sliding range by a predetermined length.

Therefore, when the cam body 20 is rotated at a high speed by a predetermined angle in the print direction P in FIG. 1 from the print start position by the motor 16, the cam follower 28 rises along the curved cam surface of the print cam 18. As a result, the rotating lever 23 rotates counterclockwise, and the print hammer 27 strikes the platen 3 via the type 30a of the daisy wheel 30 and the print ribbon PR.

Here, adjustment plates 41 extending in the front-rear direction are provided outside the upper ends of both main frames 8, and the front ends of both adjustment plates 41 have the lengths formed in each main frame 8. The support shaft 42 inserted through the circular hole 8a is fixed. On the other hand, an engaging portion 44a that slidably engages with the rear end of the guide member 6 is provided at the front end of the contact member 44 whose rear end is rotatably supported by the support shaft 42. ing.

1 to 5 show an erasing mechanism 50 for raising the holder member 32 from the printing position to the erasing position so that the erasing ribbon CR, instead of the printing ribbon PR, faces the printing hammer 27 when erasing characters. A brief description will be given based on this. The ascending cam 21 and the ribbon supply cam 22 are formed as an integral cam body, and the ascending cam 21 formed on the left side of the cam body has an equal radius from the center of the cam 21. The reference cam 21a, a first inclined cam surface 21b continuously extending from the reference cam 21a in the radial expansion direction, and a second inclined cam surface continuous with the first inclined cam surface 21b at an intermediate portion and with the outer peripheral cam surface 21d. 21c and a thin-walled guide wall 21e extending from the right end portion of the second inclined cam surface 21c in the radial expansion direction, and gradually extending from the left end surface 21f of the cam 21 to the thin-walled left end portion 21g of the guide wall 21e. A guide wall 21e with a reduced wall thickness,
The guide ribs 21h are formed along the outer periphery of the guide wall 21e so as to project from the guide wall 21e toward the left end face 21f, and the left end face 21f extends in a direction in which the radius decreases from the guide wall 21e.
A guide rib 21h extending up to is formed.

Further, the driven pin 52 abutting against the ascending cam 21 is supported by a lower end portion of a support member 51 having an upper end portion fixed to a side wall 32a at the left end portion of the holder member 32 so as to be movable in the left-right direction, and a coil spring. It is always elastically urged to the right by 53. At the start of printing, the driven pin 52 causes the tip end of the pin to contact the reference cam 21a from above due to the weight of the holder member 32 as shown in FIG. The left end face 21f is brought into contact with the left end face 21f from the left. That is, the amount of vertical swing of the holder member 32 is determined by the amount of vertical movement of the driven pin 52. here,
FIG. 4 shows the positional relationship among the printing cam 18, the lifting cam 21, the driven pin 52, and the cam follower 28 at the start of printing.

Therefore, when the cam body 20 is rotated by a predetermined angle in the direction opposite to the printing direction P (referred to as the anti-printing direction) by the motor 16 from the phase angle at the start of printing shown in FIG. Since the cam surface 21b moves upward, the holder member 32 also swings upward according to the upward moving distance, and when the cam body 20 is rotated in the printing direction P after that, the driven pin 52 moves the second inclined cam surface. Since the outer peripheral cam surface 21d is reached via 21c, the holder member 32 is swung further upward and switched to the erasing position. At this time, the erasing ribbon CR is at a position facing the print hammer 27.

Here, a predetermined amount of the print ribbon PR is wound on the take-up spool before the print hammer 27 starts the print operation, and a erasing ribbon CR is wound on the take-up spool by a predetermined number after the erasing operation. An erasing ribbon winding mechanism is provided, but the description thereof is omitted because it is not directly related to the present invention. Reference numeral 61 is a ratchet connected to the take-up spool 67 of the print ribbon PR,
Reference numeral 76 is a supply spool around which the erasing ribbon CR is wound, reference numeral 77 is a take-up spool for the erasing ribbon CR, and reference numeral 78 is a ratchet connected to the take-up spool 77.

Next, the control system of the electronic typewriter 1 is shown in FIG.
The block diagram of FIG. The keyboard KB is provided with character keys including alphabet keys, numeral keys, and symbol keys, a space key, a return key, and other various function keys in the same manner as a normal keyboard.

The rotation speed control of the motor 16 will be described. The control device C detects the rotation speed using the encoder signal input from the photo interrupter 36, and at the same time, sets the PWM (pulse width) so that the rotation speed is set. The duty ratio of (modulation) control is determined, a pulse signal having the duty ratio is supplied to the drive circuit 81, and a drive current corresponding to the pulse signal is output to the motor 16.

The controller C has a CPU 87, an input / output (I / O) interface 85 connected to the CPU 87 via a bus 86 such as a data bus, a ROM 88 and an RA.
It is composed of M90. The ROM 88 has a drive control program for driving the motor 16 to execute a printing operation or an erasing operation, a drive control program for driving each of the motors 37 to 39 in association with the printing operation or the erasing operation, a character key on the keyboard KB, A control program for character printing control executed when a printable key such as a symbol key is operated is stored.

The first time memory (whose content is time T1) 91 of the RAM 90 is stored from the previous rise to the present rise at each rising edge of the encoder signal (switching from the "L" level to the "H" level). The L level time of the L level period of the latter half of the cycle is stored, or each falling edge of the encoder signal (switching from “H” level to “L” level)
Each time, the H level time of the H level period of the latter half of the cycle from the previous fall to the present fall is stored. Also, the second
The time memory (whose content is time T2) 92 stores the H level time of the H level period in the first half of the cycle from the previous rising to the current rising for each rising of the encoder signal, or each of the encoder signals. At each fall, L in the L level period in the first half of the cycle from the previous fall to this fall
The level time is stored (see FIG. 9). Cycle memory 93
Is a cycle S obtained by adding the first time T1 and the second time T2.
T is stored. The speed memory 94 stores the speed value V (rpm) of the motor 16 calculated. The counter memory 95 stores a count value J that is incremented every 100 μsec. Furthermore, in the RAM 90,
Various memories such as a buffer, a counter and a pointer for temporarily storing the data necessary for controlling the typewriter 1 and the calculation result of the CPU 87 are provided.

Next, when the character printing control is executed by the control device C of the typewriter 1, the CPU included in this control is executed.
The timing control subroutine and the speed detection control subroutine executed by the interrupt process for 87 will be described with reference to the flowcharts of FIGS. 7 and 8.
In addition, reference numeral Si (i = 20, 21, 22, ...) In the drawing represents each step.

At the same time that the character key or the symbol key is operated on the keyboard KB to execute the character print control, the time count control (see FIG. 7) is started by the interval interrupt every 100 μsec, and the count value J of the counter memory 95 is changed. It is incremented by "1" (S3
0), this control ends.

Further, after the character printing control is started, the speed detection control (see FIG. 8) is started each time the encoder signal input from the photo interrupter 36 rises or falls, and the count value J is first multiplied by 100 μsec. The first time T1 is stored in the first time memory 91 (S20), and the second time T2 already stored in the second time memory 92 and the first time T2 are stored.
The cycle ST obtained by adding the time T1 is stored in the cycle memory 93 (S21). Next, the speed calculation of the motor 16 is executed based on this cycle ST and a predetermined angle (for example, 2.4 °), and the calculated speed value V (rpm) is stored in the speed memory 94.
(S22). Next, the first time T1 is stored in the second time memory 92 as the second time T2 (S2
3), the count value J is cleared (S24), and this control ends. However, after starting this character printing control, the motor 16 is driven at a predetermined initial speed until several rising and falling encoder signals are input.

For example, as shown in FIG. 9, at the rising timing of the encoder signal indicated by arrow A, the first
The first time T1 (L level time) stored in the time memory 91 and the second time T2 stored in the second time memory 92
The rotation speed (rpm) of the motor 16 is calculated based on the cycle ST obtained by adding (H level time). Then, the drive of the motor 16 is controlled so that the calculated rotation speed becomes the set rotation speed.

As described above, even when the error time is included in the first time T1 or the second time T2 due to variations in the mounting accuracy of the photo interrupter 36, the cycle ST ( (H level time + L level time) or the cycle ST from the previous fall to the current fall is not affected by the error time, and therefore the detection speed accuracy of the motor 16 or the encoder disk 19 by this cycle ST is significantly increased. Can be improved. Further, since the detection speed is not affected by the error time, it is possible to easily manufacture the encoder disk 19 without considering the optical system characteristics of the photo interrupter 36, and the mounting work of the photo interrupter 36 is greatly simplified. Can be converted. In addition, since the rotation speed is detected every time the encoder signal rises and every time the encoder signal falls, the cycle time for speed detection can be shortened as in the conventional case.

It is also possible to additionally provide another photo interrupter and simultaneously determine the rotation direction of the motor 16 based on the phase difference between the encoder signals respectively input from these two photo interrupters. In addition, a plurality of slits 1
It is also possible to use an encoder disk in which 9a is formed at a predetermined angle in the circumferential direction. The present invention can be applied to a method for detecting the speed of a drive shaft of an electric motor or an engine, or a rotary shaft of various drive systems in industry such as machine tools and robots driven by these drive shafts. still,
The present invention is applied to a speed detection method for detecting the moving speeds of various driving bodies that are relatively moved by various actuators such as a motor and a cylinder with respect to a linear slit plate having a plurality of slits formed at predetermined intervals. Of course, you can do that.

[Brief description of drawings]

FIG. 1 is a side view of an internal mechanism of an electronic typewriter.

FIG. 2 is a view on arrow 2 of FIG.

FIG. 3 is a partial front view of the internal mechanism of the electronic typewriter.

FIG. 4 is a side view of a carriage body.

FIG. 5 is a perspective view of a lifting cam.

FIG. 6 is a block diagram of a control system of the electronic typewriter.

FIG. 7 is a schematic flowchart of a timing control routine executed in interrupt processing.

FIG. 8 is a schematic flowchart of a speed detection control routine executed in interrupt processing.

FIG. 9 is a waveform diagram of an encoder signal input from a photo interrupter.

FIG. 10 is a waveform diagram of an encoder signal for explaining the problems of the conventional technique.

[Explanation of symbols]

 16 DC Motor 19 Encoder Disk 19a Slit 36 Photointerrupter 87 CPU 88 ROM 90 RAM C Controller

Claims (1)

[Claims] 1. A speed detector for detecting a plurality of slits formed at predetermined intervals in a circumferential direction or a linear direction on a slit plate by a detecting means and detecting the speed of the slit plate using an encoder signal from the detecting means. In the method, the encoder signal is read at the beginning and the end of each slit, the cycle from the previous rising to the current rising is calculated for each rising edge of the encoder signal from “L” to “H”, and that cycle is used. The speed of the slit plate is detected, the cycle from the previous falling to the current falling is calculated for each falling edge of the encoder signal from "H" to "L", and the speed of the slit plate is calculated using this cycle. A speed detection method based on an encoder signal, characterized by detecting.