JPH07106079B2 - Motor drive system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] The present invention enables smooth acceleration / deceleration of a motor by making a transition between a plurality of speed levels along an optimal drive curve in a step motor drive system. In addition, the noise and vibration associated with the conventional rapid acceleration / deceleration are significantly reduced.

[Industrial application field]

The present invention relates to a driving method for a step motor used in, for example, a thermal printer, and more particularly to a motor driving method for realizing high-speed and optimum transition between a plurality of speed levels.

In particular, in a thermal line printer that prints with a linear head having a length of one line while feeding a sheet with a motor, the printing speed was previously limited according to the driving ability of the head. The driving speed was not a problem, but since the head with an IC has been put into practical use recently and high-speed printing has become possible, a motor drive system that can sufficiently cope with this has become necessary.

[Conventional technology]

Conventionally, for example, as a motor drive system for realizing high-speed printing in the above-mentioned thermal printer, as shown in FIG. 8, the print area is driven at a constant speed level according to the drive capacity of the head, and the line feed space area is driven. There is a system that only drives at a high speed level.

[Problems to be solved by the invention]

In the above-mentioned conventional motor drive system, as is apparent from FIG. 8, since acceleration and deceleration at the time of changing the speed level are performed rapidly and substantially linearly, a large noise is generated immediately after the acceleration and deceleration, and There is a problem in that the vibration of the motor causes the print quality to be adversely affected.

In view of the above problems, it is an object of the present invention to provide a motor drive system that enables smooth acceleration / deceleration of a motor and can significantly reduce noise and vibration.

[Means for solving problems]

The motor drive system of the present invention has a plurality of speed levels for driving the step motor at a constant speed, and when making a transition from any first speed level among them to any second speed level, this transition is performed. Based on the number of steps involved and the first and second speed levels, the maximum speed level that can be taken during the transition, the optimum acceleration curve from the first speed level to the maximum speed level, and the maximum speed level The optimal deceleration curve up to a speed level of 2 is determined.

[Action]

According to the present invention, when transitioning from the first speed level to the second speed level, the first speed level reaches the above-mentioned maximum speed level along the optimum acceleration curve, and further, from this maximum speed level to the optimum deceleration curve. Along to a second speed level. In this way, acceleration and deceleration are carried out along the optimum curve, so that the acceleration and deceleration are extremely smooth, and noise and vibration are significantly reduced.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit block diagram of a thermal line printer to which an embodiment of the present invention is applied. This circuit is CPU1, RO
M2, RAM3, frame memory 4, external I / O5, Kanji CG for expansion
(Character generator) 6, memory management register 7 and the like. The ROM 2 stores a program routine, a timetable, etc., which will be described later. RAM3 is a work buffer RAM and is also used as a loading unit for a CG data expansion routine. The frame memory 4 has a storage capacity of, for example, 64 KBytes, and has a data loading unit for a load data expansion program and a CG.
It is used as a conversion data rearrangement unit. The external I / O 5 is, for example, a Centronics parallel interface (parallel interface conforming to Centronics) 8, a sensor 9,
Data is input and output to and from the panel (switch, LED, etc.) 10, head 11, motor 12 for paper feeding, and the like. The memory management register 7 is a management register unit for managing the RAM 3 and the frame memory 4.

Next, the main processing in this embodiment will be described with reference to FIG.

First, the Centronics parallel interface 8 receives data, and when a line feed command is input, the CPU 1 checks the state in the RAM 3. That is, the number of steps stored in the RAM3 (the number of steps of the motor 12 for feeding the paper, "constant speed printing step number", "acceleration step number",
Check the current level (current speed level) and final level (final target speed level).

The speed level corresponds to the speed at which the motor 12 is driven at a constant speed, and n steps (n ≧) depending on the print density.
2) It is set.

Subsequently, the CPU 1 calculates the optimum transition curve based on the above check. Here, the transition curve is a speed curve (acceleration curve or deceleration curve) drawn when the speed level is switched, and a normal distribution curve is used in this embodiment. This curve is
It is obtained as follows.

That is, as the acceleration curve when the speed level changes, Using, the series expansion of this equation yields Therefore, the velocity curve f (x) is Can be obtained at. By substituting specific numerical values for A, l, and m in this equation as appropriate and performing curve approximation, an optimum speed curve can be found. For example, A = 1.8, l =
An optimal velocity curve can be obtained when 9, m = 5.
Therefore, by creating this speed curve f (x) between each speed level, the number of levels n and direction (acceleration and deceleration)
According to the above, for example, 2 × _n C ₂ transition curves as shown in FIG. 5 are obtained.

Therefore, in CPU1, based on the number of steps, the current level, and the final level obtained by the above check,
The optimum curve is obtained from the above 2 × _n C ₂ transition curves. The process for obtaining the optimum curve is shown in FIG.

In the figure, if there is a line feed command, first step
Calculate the constant speed print width (width of the area printed at constant speed) with a ₁ ,
Linefeed width (the width from the beginning of the line to the beginning of the next line) to determine if it exceeds the constant speed printing width in step a _2. If not exceeded, i.e. if the constant speed printing regions overlap portion and the next constant-speed printing area, because breaking space is no width, set only "constant-speed printing step number" in step a _3, the remaining "conversion The "speed step number", "constant speed feed step number", and "deceleration step number" are set to zero. As a result, constant speed printing is performed as it is.

On the other hand, when it is determined in step a ₂ that the line feed width exceeds the constant speed print width, it is determined that there is a line feed space width, and the process proceeds to step a ₄ . In step a _4, by subtracting the constant speed printing width from line feed, determine the breaking space width. The area widths such as the line feed width, the constant speed print width, and the line feed space width are all obtained by the number of steps. Next step
Proceed to a ₅ to calculate the final level according to the print density, and check whether this final level is appropriate for the line feed space width (step number). That is, since the minimum number of steps (s) required for the speed to shift by one level is predetermined (for example, s = 4), when there is a difference of only m levels between the current level and the final level, Requires the line feed space width to be s × m steps or more, and confirms whether such a condition is satisfied. Then in step a _6, to set the current level and final level.

Next, the line feed space width obtained in steps a _{4 to} a ₆ above,
Based on the current level, and the final level, obtaining an optimum curve at step a _7. In this process, first, the curve index table (speed level 0 to
n-1 case is shown in Fig. 4 (a)), and the minimum required for speed rising (acceleration) and falling (deceleration) when transitioning from the current level to the final level through the maximum speed level. Calculate the number of steps. As described above, the minimum number of steps required for the speed to make one level transition is fixed, and is, for example, 4 steps. A specific method of using the curve index table will be described later.

If the minimum number of steps required for the acceleration and deceleration is obtained, the starting point level and the ending point level during acceleration, and the starting point level and the ending point level during deceleration are determined, and the optimum curves (acceleration curve and deceleration curve) are determined accordingly. The optimum curve is
If the starting level is i and the ending level is j, then RO
Curve address CURV _{i, j} (0 ≦ i, j ≦ n−1) is selected from the curve address table stored in M2 (the case where the speed level is 0 to n−1 is shown in FIG. 4 (c)). ) Is taken out. Each curve address CURV in the curve address table
_{i and j} correspond to the respective transition curves shown in FIG.

When the optimum curve (curve address CURV _{i, j} ) is obtained as described above, the CPU 1 reads the ROM2 in advance based on FIG. 3 (b).
Stored timetable within the curve address CURV _i from among (FIG. 4 _(d)), extracts the time data contained in _j (step b _1), performs the timer setting of the motor 12 (step b ₂ ). As a result, the motor 12 is driven along the optimum curve.

The above time table represents the transition curve corresponding to the curve address CURV _{i, j} as a series of time data consisting of time intervals between steps.
_{i, j} contains a number of time data equal to the minimum number of steps required for the velocity level to reach from i to j. For example, CURV _0,0 , CURV _1,1 , ..., CURV
_Since there is no change in the speed level (constant speed) _{, n-1 and n-1} each contain one piece of time data. CURV _0,1
Where k is the minimum number of steps required for the velocity level to reach 0 to 1, k time data T _0,0 , T
₀ , ₁ , ..., T _{0, k−1} are included. Also, CURV _{i, j}
And CURV _{j, i} contain the same number of time data arranged in opposite directions.

The motor 12 is driven as described above at the time of line feed of the printer. A specific example of the above-described processing for obtaining the optimum curve will be described with reference to FIG.

First, if there is a line feed command, in step c ₁ the line feed width l
= 0, that is, whether the print area of this time and the print area of the next time overlap with each other is confirmed. If l = 0, the process proceeds to step c ₂ to set the speed level L ₁ = L ₂ = L ₃ = 0. Here, the speed levels L ₁ and L ₃ are the above-mentioned current level and final level, respectively, and the speed level L ₂ is the maximum speed level that can be taken at the time of line feed. Since L ₁ , L ₂ and L ₃ are all set to 0, n stages (here, n = 8)
Is set to the lowest of the speed levels. That is, the motor speed does not change and remains constant.

If l ≠ 0 in step c ₁ , it is determined in step c ₃ whether l exceeds a constant (maximum width of line feed),
Proceed to step c ₄ only if not exceeded. In step c ₄ , the constant speed print width is calculated by the number of steps of the motor, and this is put in A. Then, in step c ₅ , it is determined whether A is larger than l, that is, whether the constant speed print width is larger than the line feed width. For l <A, the process proceeds to step c ₆ as no breaking space, together put l to A, to B = C = D = 0, the procedure proceeds to step c _2. here,
A, B, C, and D represent the constant speed printing step number, the acceleration step number, the constant speed feeding step number, and the deceleration step number, respectively. That is, in step c _6, since there is no breaking space is set only the number of steps for the constant speed printing.

If l ≧ A in step c ₅ , it is determined that there is a line feed space, and the process proceeds to step c ₇ , and the last final level in L ₃ is entered in L ₁ as the current current level. Then c ₈
Then, the line feed space width is obtained by subtracting A from l, and this value is put into l. Next, in step c _9, it is determined whether the next line can be printed, that is, whether there is print data for the next line. If printing is not possible, the final level L ₃ = 0 is set in step c ₁₀ , and step c ₁₃ Proceed to. Printing possible, the print duty calculated in step c _11, obtaining the final level L ₃ based on the results. After that, in step c ₁₂ , it is determined whether or not L ₃ = 0. If L ₃ ≠ 0, the process proceeds to step c ₁₃ . In step c _13, it determines whether the number of steps required to reach the current level L ₁ to the last level L ₃ is in line feed space. If there is a required number of steps, proceed directly to step c ₁₆ . Without the number of steps required shifts to step c _14, a transition can speed level taking into L ₃ in the number of steps of breaking space component, the process proceeds to this step c ₁₆ after stored in the work (WORK) region. On the other hand, if the next line in the L ₃ = 0 in step c ₁₂ only paper feed proceeds from the addition of the number of steps of the next line to the line feed space width l in step c ₁₅ to step c _16.

At step c ₁₆ , the minimum number of steps required to reach the current level L ₁ to the final level L ₃ is subtracted from the line feed space width l, and the value is put into l. Followed by step c _17, whether the subtraction value l is greater than 0, that is, whether there newline space to accelerate, l ≦ 0
The acceleration step number B and the deceleration step number D from a 0 in the case of only step c _18, the process proceeds to step C _19.

In step c ₁₉ , the above-mentioned curve index stable (when the speed level is 0 to n−1 is shown in FIG.
As an example thereof, the case where n = 8 is shown in FIG. 7B) is used to obtain each step number (acceleration step number B, constant speed feed step number C, subtraction step number D).

As an example, consider a case where the current level L ₁ = 1, the final level L ₃ = 5, the line feed space width l = 35 steps, and the minimum number of steps required to make one level transition is 4. In this case, it is first judged whether or not the speed level L ₁ = 1 can be reached to L ₂ = 7 (maximum speed level) to L ₃ = 5. First, since the intersection point of the vertical axis “1” and the horizontal axis “7” of the curve intex table shown in FIG. 4 (b) is “6”, transition from L ₁ = 1 to L ₂ = 7. It can be seen that at least 6 × 4 = 24 steps are required.
Then, since the intersection of the vertical axis “7” and the horizontal axis “5” is “2”, at least 2 × is required to transition from L ₂ = 7 to L ₃ = 5.
It can be seen that 4 = 8 steps are required. From these, it can be seen that at least 24 + 8 = 32 steps are required for acceleration and deceleration. Compared with this, there is a margin in the line feed space width l = 35 steps (32 <35), so the speed level L ₂ = 35 = 32 = 3 for constant speed feed step by 7
It can be decided as a step. From the above, acceleration step B = 24, constant speed (speed level 7) feed step C
= 3 and deceleration step D = 8 steps, it is possible to reach L ₃ = 5 from L ₁ = 1 to L ₂ = 7 in the line feed space.

If the line feed space width l is less than 32 steps (for example, 30 steps), the constant speed feed level L ₂ is lowered by 1 level to 6 (= 7-1), and similarly accelerated (L ₁ =
Calculate the number of steps from 1 to L ₂ = 6) and deceleration (from L ₂ = 6 to L ₃ = 5). Then, it can be seen that 5 × 4 = 20 steps are required for acceleration and 1 × 4 = 4 steps are required for deceleration, so 30− (20 + 4) = 6 steps can be given for constant speed feeding. Even in other cases, the number of steps can be obtained in the same manner as above.

When step numbers B, C, and D are obtained in step c ₁₉ ,
The process proceeds to step c _20. Here, in step c ₁₉ , L ₁
When only one of acceleration step number B or deceleration step number D is set to 0 under the condition of = L ₃ , the non-zero one and the step number are set to constant speed feed step number C to correct the irrationalities. In addition, both B and D are set to 0.

Above way the number of steps by B, C, the current level L ₁ proceeds to step c ₂₁ When D allocation is completed, JOG level L _2, based on the final level L _3, as shown in Figure 4 (c) The curve address CURV _{i, j} is obtained from the curve address table. That is, two curve addresses CURV _{i, j} obtained as (i, j) = (L ₁ , L ₂ ) and (L ₂ , L ₃ ) correspond to the acceleration curve and the deceleration curve, respectively. In this way, the optimum curve after the line feed can be obtained.

Next, an example of the motor drive by the above processing in the present embodiment is shown in FIGS. 6 (a) and 6 (b). FIG. 7A shows a standard transition curve, in which the current level 0 reaches the maximum level n−1 along the acceleration curve r _{0, n−1} and the constant speed feed is performed at the maximum level. After that, the deceleration curve r
_The final level 0 is reached along _n−1,0 (= −r _{0, n−1} ). FIG. 7B shows a transition curve when the current level i (> 0) transits to the final level 0. When the line feed space is sufficient, the final level is reached through the highest level n-1. As the line feed space becomes narrower, the maximum level drops, and the transition is made along the acceleration and deceleration curves (or only the deceleration curve) without constant feed. Thus, n speed levels are set according to the print density, and the optimum curve is selected according to each level and the line feed space width.

As described above, in this embodiment, since the motor is accelerated and decelerated along a smooth normal distribution curve when the printer feeds a line, the noise and vibration associated with the conventional rapid acceleration and deceleration can be significantly reduced. The printing quality can be improved accordingly. Also, since various tables can be used to simplify the arithmetic processing, it is possible to use only one CPU, which previously required two CPUs, which simplifies the device configuration and reduces the cost. Price realization is realized.

In the above embodiment, a normal distribution curve is used as the transition curve, but if it is a curve that changes smoothly during acceleration / deceleration,
It may be a curve other than the normal distribution curve. Further, in the mechanism having a relatively small moment of inertia, smooth motor driving was possible by the driving method of the above-mentioned embodiment, but the symmetry of the acceleration curve and the deceleration curve collapses as the moment of inertia increases, It is necessary to use an asymmetric curve as shown in FIG. This can be realized by adding a correction to the method of the above embodiment.

Further, the present invention can be applied to various devices using a step motor other than the thermal printer.

〔The invention's effect〕

According to the motor drive system of the present invention, since the acceleration and deceleration of the motor are performed along the optimum curve, very smooth acceleration / deceleration is possible, and therefore noise and vibration during the acceleration / deceleration of the motor are significantly reduced. be able to.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of a thermal line printer to which an embodiment of the present invention is applied, FIG. 2 is a block diagram showing a main processing flow in the embodiment, and FIG. FIG. 3 (b) is a flowchart showing the process for obtaining the optimum curve in FIG. 3, FIG. 3 (b) is a flowchart showing the process for setting the motor timer in the same embodiment, and FIG. A flowchart showing an example, FIGS. 4A, 4B, 4C, and 4D show a curve index table used in the above processing, an example of a curve index table, a curve address table, and a time table, respectively. FIG. 5 is a diagram showing an example of a transition curve used in the same embodiment, FIGS. 6 (a) and 6 (b) are diagrams showing an example of driving a motor in the same embodiment, and FIG. Shows the acceleration and deceleration curve according to another embodiment of the invention (when the inertia moment of the heavy load), FIG. 8 is a diagram showing an example of driving the motor in the prior art. 1 ... CPU, 2 ... ROM, 3 ... RAM, 12 ... motor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-305796 (JP, A) JP-A-63-157698 (JP, A) JP-A-62-285862 (JP, A) JP-A-62- 221899 (JP, A) JP-A-61-9197 (JP, A) Actually developed 54-618 (JP, U)

Claims (6)

[Claims] 1. A step motor, which is driven at a constant speed at any one of a plurality of speed levels to move a movable object, from any first speed level of the plurality of speed levels. In the motor drive method for making a transition to the second speed level of the above in any number of steps, for all of the two speed levels that can be combined in the plurality of speed levels, the minimum speed between the two speed levels is minimized. A transition curve capable of continuous and smooth transition with the number of steps is previously obtained, and the arbitrary number of steps required for the transition from the first speed level to the second speed level and the transition with the transition curve Determining the maximum possible speed level during the transition from the first speed level to the second speed level, based on the minimum number of steps required for From among the above, a transition curve that rises from the first speed level to the maximum speed level is selected as an optimum acceleration curve, and a transition curve that processes from the maximum speed level to the second speed level is set as an optimum deceleration curve. And changing the speed of the stepping motor from the first speed level to the maximum speed level via the optimum acceleration curve, and then from the maximum speed level to the second speed level via the optimum deceleration curve. A motor drive method characterized by switching to. 2. A timetable in which the transition curve is represented by time data consisting of time intervals between steps is created in advance, and time data corresponding to the optimum acceleration curve and the optimum deceleration curve is selected from the timetable. The motor drive system according to claim 1, wherein the motor drive system is taken out. 3. The motor drive system according to claim 2, wherein the transition curve is a normal distribution curve. 4. The movable object is a printing sheet in a thermal printer.
The motor drive system according to any one of items 1 to 3. 5. The motor drive system according to claim 4, wherein the plurality of speed levels are determined according to print density in the thermal printer. 6. The method according to claim 4 or 5, wherein the number of steps involved in the transition is the number of steps corresponding to the line feed space width in the thermal printer.
The motor drive method described in the item.