JP2002250637A - Detecting means for reference position of mobile body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable highly accurate reference position detection by reducing detection error of the reference position due to detection error of a sensor of a linear encoder. SOLUTION: In this reference position detection method of a moving body, a solid black part 13 having no slit is formed on a scale 10 of the linear encoder, and while moving the moving body by a stepping motor, the sensor 11 of the linear encoder detects the solid black part 13, to thereby detect the reference position of the moving body. In the method, the moving body is moved in the prescribed reference position detection position, and the stat end 13a and the finish end 13b of the solid black part 13 is detected by the sensor 11, and the intermediate point, between a start end corresponding position Xa which corresponds to the start end 13a of the solid black part 13 detected by the sensor 11 and a finish end corresponding position Xb which corresponds to the finish end 13b of the solid black part 13 detected by the sensor 11, is used as the reference position Xc of the moving body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a reference position of a moving body, and more particularly, to a method for detecting an absolute position of a moving body in a moving body position detecting device using a linear encoder. The present invention relates to a method for detecting a position (reference position).

The present invention can be applied to the detection of the reference position of various moving objects. For example, the present invention is applied to the detection of the reference position of an ink carriage which is a moving object in an ink jet printer.

[0003]

2. Description of the Related Art FIG. 1 shows an ink carriage (moving body) (1) in an ink jet printer to which the present invention is applied.
2 shows a main part of the position detecting device.

The carriage (1) is equipped with a cyan ink cartridge (2), a magenta ink cartridge (3), a yellow ink cartridge (4), and a black ink cartridge (5). The carriage (1) is a linear slide shaft (6)
Slidably supported by a timing belt (7), and driven by a stepping motor (8) to drive the belt (7) to reciprocate in a straight line along the slide shaft (6). Let me do.

The position detecting device includes a photoelectric linear encoder scale (10) disposed along the movement path of the carriage (1) and a sensor (11) of the linear encoder fixed to the carriage (1). The details are shown in FIG.
It is shown in (a).

The scale (10) is linear and has a slide shaft.
It is arranged parallel to (6). On the scale (10), a number of slits are formed at equal intervals in the length direction, and a plurality of slits are formed at portions near the left end of the portions (12a) and (12b) where the slits are formed. A black solid portion (13) without a slit is formed over a corresponding predetermined length. Of the slits, the shorter part on the left side than the solid black part (13) is the left slit part (12a), the solid black part (1
The longer part on the right side than 3) is called the right slit part (12b), and these are collectively referred to by the reference numeral (12).

The sensor (11) is arranged so as to sandwich the scale (10). The slit (12) of the scale (10) detects a slit to generate a pulse, and the black solid portion (13) generates a pulse.
No pulse is generated.

In an apparatus using a moving body such as an ink-jet printer, it is necessary to detect the absolute position of the moving body and position the moving body. Can be detected, but the absolute position cannot be detected.
Therefore, as described above, a solid black portion is provided on the scale of the linear encoder to detect the reference position for positioning, and based on this, the absolute position of the moving body is detected.

In the above ink jet printer,
When the printing operation is not performed, the carriage (1) is stopped at a predetermined standby position in the left slit portion (12a).
When starting the printing operation, the carriage (1) passes through the solid black portion (13) from the standby position and passes through the right slit portion (12).
It is moved to the right until it reaches b), and the reference position is detected while passing through the solid black portion (13), as described later. During the subsequent printing operation, the carriage (1) moves the right slit portion (12b). At this time, the absolute position of the carriage (1) is detected based on the reference position using the right slit portion (12b), whereby the position of the carriage (1) is controlled. When the printing operation is completed, the carriage (1) is moved to the left, passes through the solid black portion (13), returns to the standby position, and stops at that position.

Next, with reference to FIG. 4, a description will be given of a method of detecting a reference position in a conventional position detecting device for the carriage (1) of an ink jet printer. 4 (a) shows the positional relationship between the scale (10) and the sensor (11), and FIG. 4 (b) shows the output of the sensor (11) at each position on the scale (10).
Indicates a driving step of the stepping motor (8). Since the carriage (1) moves integrally with the sensor (11), in this specification, the carriage (1)
The position of represents the position of the carriage (1),
The position of the sensor (11) is represented by the number of output pulses.

As shown in FIG. 4, when the sensor (11) moves to the right, no pulse is output while the sensor (11) is passing through the solid black portion (13). As a result, the start (left end) (13a) or the end (right end) (13b) of the solid black portion (13) is detected and used as a reference position for positioning. Since the stepping motor (8) moves the sensor (11) by a fixed distance (step) by pulse driving, if no pulse is output from the sensor (11) for a predetermined driving step or more, the solid black portion (13) It is determined that the vehicle is passing through the black solid portion (13).
(13a) can be detected. However, even when the carriage (1) moves to the extreme positions at both ends of the moving range and does not move any further, there is a possibility that no pulse is output from the sensor (11) for a predetermined drive step or more. Therefore, actually, by detecting that a pulse is output again after completely passing through the solid black portion (13), the solid black portion (13) is detected.
(13b) is detected and set as a reference position.

More specifically, FIG.
While the sensor (11) passes through the left slit portion (12a) as shown by, a pulse is output from the sensor (11), but as shown by the position X2, the sensor (11) Part (1
When reaching the vicinity of the starting end (13a) of 3), no pulse is output. Note that a state where a pulse is output from the sensor (11) is referred to as a state with a pulse, and a state where no pulse is output is referred to as a state without a pulse. In this way, the state changes from the state with the pulse to the state without the pulse, and if the state without the pulse continues while the stepping motor (8) is driven by m steps, the solid black passes through the starting end (13a). It is determined that the vehicle is passing through the portion (13). In this determination, the impulse noise in the output of the sensor (11) is ignored. Further, the position of the sensor (11) when it is determined that the state without a pulse continues for m steps and the solid black portion (13) is being passed is indicated by X3 in FIG. As shown by the position X4, the sensor (11) is
When the pulse reaches the vicinity of the end (13b) of (3), the pulse is output again from the sensor (11) .If the pulsed state continues while the stepping motor (8) is driven by n steps, the sensor ( 11) passes through the end (13b) and the solid black part (13)
Is completely passed, and it is determined that the left slit portion (13b) has been reached. Alternatively, after it is determined that the sensor (11) is passing through the solid black portion (13) at the position X3,
When the number of output pulses of (11) reaches i, that is, when the state changes from no pulse to a state with pulses and the pulse of i is output, the sensor (11) detects the solid black portion (13). Is determined to have passed completely. The state with a pulse continues for n steps, or the pulse of i is output,
The position of the sensor (11) when it is determined that it has completely passed through the solid black portion (13) is indicated by X5 in FIG. And
The position X4 at which the pulse starts to be output again or the position X5 determined to have completely passed the solid black portion (13) are set as reference positions. Thereafter, as shown by the position X6, for example, while the sensor (11) is moving in the right slit portion (12b), the state with the pulse continues, so that the pulse from the sensor (11) is used as described above. The absolute position of the sensor (11) can be detected based on the detected reference position.

[0013]

In the above-described conventional method for detecting the reference position of a moving object, an error occurs in the detection of the end of the solid black portion by the sensor of the linear encoder, and the detection error of the reference position is reduced. It becomes equal to the detection error at the end,
There is a problem that the detection accuracy of the reference position deteriorates.

Next, this problem will be described in detail with reference to FIG. Fig. 5 (a) shows the scale (10) and the sensor
FIGS. 5B and 5C show the positional relationship of FIG.
The output of the sensor (11) at each position of (0) is shown. FIG. 5B shows the output of an ideal sensor (11) when there is no detection error, and FIG. 5C shows the output of an actual sensor (11).

In an ideal case where there is no detection error,
As shown in FIG. 5 (b), the sensor (11) is located at a position (start position) Xao corresponding to the start (13a) of the solid black portion (13) or at a position (end position) Xbo corresponding to the end (13b). When positioned correctly, a change with or without a pulse (change from a state with a pulse to a state without a pulse) or a change with or without a pulse (change from a state without a pulse to a state with a pulse) occurs On the outside of the solid black portion (13) (on the side of the slit portion (12)), there is a pulse, and inside the solid black portion (13), there is no pulse. However, actually, since there is a detection error of the sensor (11), a position (a starting end corresponding position) Xa at which a change occurs with / without a pulse or a position (end corresponding position) Xb at which a change occurs with / without a pulse,
It deviates from the start position Xao or the end position Xbo. The shift of the start end corresponding position Xa or the end corresponding Xb occurs inside the solid black portion (13) from the start end position Xao or the end position Xbo. That is, the sensor (11) detects the start (1
This is because the slit of the outer slit portion (12) continues to be detected up to a certain distance even if the slit is located inside the end (3a) or the end (13b). When the positions Xa and Xb at which the change with / without the pulse or the change with / without the pulse occurs are shifted, the starting end (13
An error occurs in the detection result of a) or the end (13b). Start position X corresponding to start position Xao or end position Xbo
a or the magnitude of the deviation of the end corresponding position Xb is determined by the sensor (1
1), and the left end (13
a) and the right end (13b) are different. This deviation, that is, the sensor (1
Assuming that the maximum value of the variation of the detection error in 1) is E, the detection error α at the left end (13a) and the right end (13
The detection error β in b) is expressed by the following equation, and the maximum E
Error occurs.

0 ≦ α ≦ E (1) 0 ≦ β ≦ E (2) Conventionally, as described above, the end corresponding position Xb detected by the sensor (11) is used as it is as the reference position. Alternatively, since the reference position is obtained based on this, the maximum value of the detection error of the reference position also becomes E, which is the same as the maximum value of the detection error of the end (13b). Generally, the maximum value E of the detection error is large and may be several times or more the driving resolution of the stepping motor (8). For example, in the case of the conventional apparatus, the driving resolution of the stepping motor (8) is 0.2 mm and the sensor (11)
Is up to about 0.93 mm. However, the above-mentioned 0.2 mm and 0.93 mm are examples of numerical values, and have different values depending on a used motor, sensor, configuration, and the like.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, to reduce the detection error of the reference position due to the detection error of the linear encoder sensor, and to detect the reference position of a moving object with high accuracy. It is to provide a method.

[0018]

According to the present invention, there is provided a method of detecting a reference position of a moving object, comprising the steps of: providing a scale of a linear encoder along a moving path of the moving object reciprocated by a stepping motor; A sensor of a linear encoder that generates a pulse by detecting a slit of this scale during movement of the scale is provided on the moving body, and a position detecting device of the moving body that detects a position of the moving body based on a pulse from this sensor. A method of detecting a reference position of a moving body by providing a solid black portion without a slit over a predetermined length on a scale, and detecting the solid black portion by a sensor while the moving body is moving. Moved in the predetermined reference position detection direction, the start and end of the solid black portion are detected by the sensor, and the solid black portion detected by the sensor is detected. It is characterized in that the starting end corresponding position corresponding to the starting end, the reference position of the moving body midpoint between end corresponding position corresponding to the end of the black solid portion detected by the sensor.

By setting an intermediate point between a starting end corresponding position corresponding to the starting end of the solid black portion detected by the sensor and an end corresponding position corresponding to the end of the solid black portion detected by the sensor as a reference position of the moving body, The maximum value of the detection error of the reference position is half of the maximum value of the detection error of the sensor, that is,
It is half of the conventional reference position detection error.

Next, the reason will be described with reference to FIG. FIG. 3 is a drawing corresponding to FIG. 5 of the related art, and the same portions are denoted by the same reference numerals.

In FIG. 3, as in FIG. 5, the detection error of the sensor (11) at the left end (13a) of the solid black portion (13) is α, and the detection error at the right end (13b) is β. Assuming that the maximum value of the error is E, α and β are given by the above equations.
It is represented by (1) and (2).

Assuming that the length of the solid black portion (13) is L, the distance Ao from the left end (13a) of the solid black portion (13) to the intermediate point Xco when there is no error is given by the following equation. expressed.

Ao = L / 2 (3) In the actual case where the detection error at the left end (13a) is α and the detection error at the right end (13b) is β, the solid black portion detected
Assuming that the distance from the left end (13a) of the intermediate point Xc of (13) is A,
This is represented by the following equation.

A = {(L−β) + α} / 2 (4) Therefore, assuming that a detection error of the actual intermediate point Xc with respect to the ideal intermediate point Xco is γ, this is represented by the following equation. Is done.

Γ = | A−Ao | (5) By substituting the relations of equations (3) and (4) into equation (5), equation (5) is obtained.
Is rewritten as:

Γ = | α−β | / 2 (6) From this equation and the above equations (1) and (2), the range of γ is represented by the following equation.

0 ≦ γ ≦ E / 2 (7) From this, the maximum value of the detection error of the intermediate point, that is, the reference position Xc is half the maximum value E of the detection error of the sensor (11). Understand.

Therefore, according to the method of the present invention, the detection error of the reference position due to the detection error of the sensor of the linear encoder can be reduced, and the accuracy of the reference position detection can be improved.

After the reference position of the moving body is detected by the method of the present invention, the absolute position of the moving body is detected based on the reference position, and the movement of the moving body is controlled based on the detected absolute position.

In the method of the present invention, for example, the number of driving steps of the stepping motor and the number of output pulses of the sensor are measured, and the start corresponding position and the end corresponding position of the solid black portion are detected from these relationships.

Normally, the driving resolution of the stepping motor is lower than the resolution of the sensor of the linear encoder. Therefore, if only the number of driving steps of the stepping motor is used to determine the reference position, the starting position and the end position can be detected. An error corresponding to the driving resolution of the stepping motor is added.

As described above, the number of driving steps of the stepping motor and the number of output pulses of the sensor are measured together, and from the relationship between the two, the position of the intermediate point between the start corresponding position and the end corresponding position is determined by the resolution level of the sensor. By calculating, it is possible to suppress the occurrence of an error corresponding to the drive resolution of the stepping motor and to increase the detection accuracy.

In the above method, for example, the moving body is moved from a predetermined measurement start position in a reference position detection direction,
The number of output pulses Pa of the sensor from the measurement start position to the detection of the start position of the solid black portion, the measurement end position at which it is detected that the solid black portion has been completely detected after detecting the end corresponding position of the solid black portion Sensor output pulse number P up to
b, and the number of drive steps S of the stepping motor from the measurement start position to the measurement end position are measured, and the ratio R of the resolution of the sensor to the resolution of the step of the stepping motor is used as the measurement completion position by the following equation. Distance D from sensor to reference position expressed in number of sensor output pulses
Is calculated.

D = (RS-Pa + Pb) / 2 According to this, the position of the intermediate point between the start-end equivalent position and the end-end equivalent position is determined using the relationship between the number of driving steps of the stepping motor and the number of output pulses of the sensor. Can be accurately calculated, the detection error of the reference position due to the detection error of the sensor of the linear encoder can be reduced, and the reference position can be detected with high accuracy.

In the above method, for example, when the output of the sensor changes from the state with the pulse to the state without the pulse, and the state without the pulse continues for a predetermined number of drive steps or more, the sensor detects the start end of the solid black portion. It is determined that the signal has passed, and the position when the output of the sensor changes from the state with the pulse to the state without the pulse is defined as the start end corresponding position.

According to this, the start end corresponding position can be detected with high accuracy, and the reference position can be detected with high accuracy.

In the above method, for example, when the output of the sensor changes from a state without a pulse to a state with a pulse and the state with a pulse continues for a predetermined number of driving steps or more, the sensor terminates the black solid portion. It is determined that the pulse has passed, and the position when the state changes from the state without the pulse to the state with the pulse is set as the terminal corresponding position, and the position when the state with the pulse continues for the predetermined number of drive steps is set as the measurement end position. .

According to this, the end-corresponding position and the measurement end position can be detected with high accuracy, and a highly accurate reference position can be detected.

In the above method, for example, when the output of the sensor changes from a state without a pulse to a state with a pulse, and when a predetermined number or more of pulses are output, the sensor passes through the end of the solid black portion. Judgment is made, and the position when the state changes from the state without the pulse to the state with the pulse is set as the terminal corresponding position, and the position when the predetermined number of pulses are output is set as the measurement end position.

According to this, the end-corresponding position and the measurement end position can be detected with high accuracy, and a highly accurate reference position can be detected.

In the above method, for example, the stepping motor is stopped at the measurement end position.

According to this, by stopping the stepping motor at the measurement end position, it is possible to accurately detect the absolute position of the moving body after the detection of the reference position.

[0043]

Embodiments of the present invention will be described below with reference to FIG.

The position detecting device to which the reference position detecting method according to this embodiment is applied is the one in the ink jet printer shown in FIG. FIG. 2 is a drawing corresponding to FIG. 4 of the related art, and the same portions are denoted by the same reference numerals.

Also in this embodiment, when the printing operation is not performed, the carriage (1) is moved to the left slit portion (12a).
At a predetermined standby position. This standby position is a measurement start position Xs for detecting a reference position described later.
The method of detecting the reference position is different from that of the conventional case, but the operation of the carriage (1) thereafter is the same as that of the conventional case.

For detection of the reference position, the sensor (11) is moved from the measurement start position Xs to the right through the solid black portion (13) to the measurement end position Xe of the right slit portion (12b) described later. By doing so. Then, while the sensor (11) is passing through the solid black portion (13), a starting end corresponding position Xa at which a change with / without a pulse occurs and an end corresponding position Xb at which a change with / without a pulse are detected. The position Xc of these intermediate points is set as a reference position.

Next, a method of detecting the reference position will be described in detail with reference to FIG.

First, at the measurement start position Xs, the sensor (1
At the same time as the movement to the right in 1) is started, the counting of the number of output pulses of the sensor (11) and the number of driving steps of the stepping motor (8) is started. When the sensor (11) is solid black (1
If the state with or without the pulse occurs after passing through the start position Xao of 3) and the state without the pulse continues for a predetermined number of steps (for example, m steps), the sensor (11) passes through the start position Xao. It is determined that the black solid part (13) is passing,
The count value Pa of the number of output pulses at that time is stored, and
Reset the count value. Since the pulse is not output during the passage of the solid black portion (13) after the change with and without the pulse at the start end corresponding position Xa, the count value P
a is the number of output pulses from the measurement start position Xs to the start end corresponding position Xa. Next, if the sensor (11) reaches the position just before the end position Xbo, a change occurs without a pulse and with a pulse, and the state with a pulse continues for a predetermined number of steps (for example, n steps), the sensor (11) Passes the end position Xbo,
Judging that it has completely passed the solid black portion (13) and reached the measurement end position Xe, the stepping motor (8) was stopped,
The sensor (11) is stopped at the measurement end position Xe, and the count value Pb of the number of output pulses and the count value S of the driving step at that time are stored. Since no pulse is output from the change of the presence or absence of the pulse at the start end corresponding position Xa to the change of the absence or presence of the pulse at the end corresponding position Xb, the count value Pb of the output pulse stored at this time is stored. Is the number of output pulses from the end corresponding position Xb to the measurement end position Xe. Further, the count value S of the driving step stored at this time is the measurement start position X
The number of drive steps from s to the measurement end position Xe. When the ratio of the resolution of the sensor (11) to the resolution of the driving step of the stepping motor (8) is R, and the number of driving steps S is converted into the number of output pulses, R · C is obtained. The number of output pulses (= RC) is represented by Ps.

When the sensor (11) is stopped at the measurement end position Xe as described above, the following equation is used to calculate the intermediate point between the start end corresponding position Xa and the end corresponding position Xb from the measurement end position Xe. , That is, the distance D to the reference position Xc.

D = (R · S−Pa + Pb) / 2 (8) As a result, the absolute position of the measurement end position Xe with respect to the reference position Xc can be determined. Thereafter, the sensor ( The absolute position of the sensor (11) can be detected using the number of output pulses of (11).

The above equation (8) is derived as follows.

In FIG. 2, when the distance from the start point corresponding position Xa to the end point corresponding position Xb is B, this is represented by the following equation.

B = Ps-Pa-Pb = RS-Pa-Pb (9) The distance D from the measurement completion position Xe to the reference position Xc is represented by the following equation.

D = Pb + B / 2 (10) Therefore, by substituting B of equation (9) into this,
Equation (8) above is obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a part of an ink carriage position detecting device in an ink jet printer to which a moving object reference position detecting method of the present invention is applied.

FIG. 2 is an explanatory diagram showing an example of a method of detecting a reference position of a moving object according to the present invention.

FIG. 3 is an explanatory diagram illustrating that a detection error of a reference position is reduced by the method of the present invention.

FIG. 4 is an explanatory diagram illustrating a conventional method of detecting a reference position of a moving object.

FIG. 5 is an explanatory diagram for explaining occurrence of a detection error in a conventional method of detecting a reference position of a moving object.

[Explanation of symbols]

 (1) Carriage (8) Stepping motor (10) Scale (11) Sensor (12) Slit (13) Solid black part

Claims (7)

[Claims] A linear encoder scale is provided along a movement path of a moving body reciprocated by a stepping motor, and a pulse is generated by detecting a slit of the scale during movement of the moving body to generate a pulse. A sensor is provided on a moving body, and in a moving body position detecting device that detects the position of the moving body based on a pulse from the sensor, a black solid portion without a slit is provided on a scale over a predetermined length to move the moving body. A method for detecting the reference position of the moving body by detecting the solid black portion by a sensor, wherein the moving body is moved in a predetermined reference position detection direction, and the start and end of the solid black portion are detected by the sensor. The start position corresponding to the start end of the solid black portion detected by the sensor and the end of the solid black portion detected by the sensor. A method for detecting a reference position of a moving body, wherein an intermediate point between the corresponding end corresponding position is set as a reference position of the moving body. 2. The moving body according to claim 1, wherein the number of driving steps of the stepping motor and the number of output pulses of the sensor are measured, and the start corresponding position and the end corresponding position of the solid black portion are detected based on the relationship. Reference position detection method. 3. A sensor output pulse number P from a measurement start position to a reference position detection direction until a movable body is moved from a predetermined measurement start position to a position corresponding to a start end of a solid black portion.
a, the number of output pulses Pb of the sensor from the position corresponding to the end of the solid black portion to the measurement end position when it is detected that the solid black portion has completely passed, and the stepping motor from the measurement start position to the measurement end position Using the ratio R of the resolution of the sensor to the resolution of the step of the stepping motor, and the distance R expressed as the number of output pulses of the sensor from the measurement completion position to the reference position, using the following formula: 3. The method according to claim 2, wherein D is calculated. D = (RS · Pa + Pb) / 2 4. When the output of the sensor changes from a state with a pulse to a state without a pulse, and the state without a pulse continues for a predetermined number of drive steps or more, it is determined that the sensor has passed the beginning of the solid black portion. 4. The method according to claim 3, wherein a position when the output of the sensor changes from a state with a pulse to a state without a pulse is set as a start end corresponding position. 5. When the output of the sensor changes from a state without a pulse to a state with a pulse and the state with a pulse continues for a predetermined number of driving steps or more, it is determined that the sensor has passed the end of the solid black portion. The position at the time of changing from the state without the pulse to the state with the pulse is set as the terminal corresponding position, and the position when the state with the pulse continues for the predetermined number of drive steps is set as the measurement end position. The method for detecting a reference position of a moving object according to claim 3. 6. When the output of the sensor changes from a state without a pulse to a state with a pulse and a predetermined number or more of pulses are output, it is determined that the sensor has passed the end of the solid black portion, and no pulse is detected. 4. The moving body according to claim 3, wherein a position when the state changes from the state of (1) to the state with a pulse is set as a terminal corresponding position, and a position when the predetermined number of pulses are output is set as a measurement end position. Reference position detection method. 7. The method according to claim 3, wherein the stepping motor is stopped at the measurement end position.