JP2003204690A - Speed controller for dc motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a speed controller for a DC motor, which can accurately control the speed, without enlarging the gain in feedback control, even when shifting the target of drive at low speed. <P>SOLUTION: When a carriage is shifted as the target of drive along an encoder strip, a substantially actual shifting speed (unit: ips) can be obtained by dividing 66660d by a captured value, if the sampling time is 0.1 μsec and encoder resolution is 150 dpi. In this case, as shown in Table (A), the capture value corresponding to 30 ips becomes 2222d, and the amount of 0.5% ripple amount becomes 26H. However, in this case, the captured value corresponding to a shifting speed 8 ips becomes 8333d, and the amount of 0.5% ripple amount becomes 0AH. Accordingly, when the desired speed is 8 ips, the amount of 0.5% ripple amount is less likely to be reflected on feedback control. So if the speed is obtained, by dividing 266640d which is four times as large by a captured value as shown in Table (B), the amount of 0.5% ripple amount becomes 28H. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed control device for a DC motor, which feedback-controls the DC motor so that a drive target driven by the DC motor has a desired speed.

[0002]

2. Description of the Related Art Conventionally, the speed of a driven object driven by a direct current motor is detected via a linear encoder or a rotary encoder, and the direct current motor is feedback-controlled so that the detected speed matches a target speed. Is widely known. For example, in the field of various printers, it is considered to detect the moving speed of a carriage equipped with a head via a linear encoder and perform feedback control so that the moving speed of the carriage becomes a desired speed suitable for print control. Has been.

FIG. 5 is an external perspective view showing a partial mechanism of a general printer. As shown in FIG. 5, the printer is provided with a print head 20. The print head 20 changes the volume of the ink chamber by applying a voltage to a piezoelectric element provided in the ink chamber,
This is a so-called inkjet type head for performing printing by ejecting ink in the ink chamber from the nozzles toward the printing paper 12, which is the printing medium. The print head 20 is mounted on the carriage 14, and the carriage 14
Includes a guide shaft 16 provided in the width direction of the printing paper 12.
Has been inserted.

The carriage 14 is connected to an endless belt 17 provided below the carriage along a guide shaft 16. The endless belt 17 is a pulley 2 of a CR motor 18.
2 and another idle pulley (not shown). That is, the carriage 14 is configured to reciprocate in the width direction (main scanning direction) of the printing paper 12 along the guide shaft 16 by the rotation of the CR motor 18.

Further, slits are formed along the guide shaft 16 below the guide shaft 16 at a constant minute interval, and a linear timing slit 24 made of a translucent material is provided. Further, a sensor element 26 for reading the interval of the slits marked on the timing slit 24 and outputting a pulse signal corresponding to the position of the carriage 14 is provided on the lower front portion of the carriage 14.

The sensor elements 26 have a phase of 3 /
It is a photocoupler composed of two light emitting elements and light receiving elements that are shifted by four cycles. That is, due to the phase difference between the pulses output from these two sets of elements, the carriage 1
The moving direction of 4 is detected. The timing slit 24 and the sensor element 26 form a so-called linear encoder. The cycle of the pulse output from the sensor element 26 corresponds to the interval between the timing slits 24 and the moving speed of the carriage 14.

Further, the printing paper 12 is provided between a paper feed roller (not shown) rotated by an LF motor for paper feed (not shown) and press rollers 28, 28 provided in pair with the paper feed roller. It is sandwiched and sent vertically. A DC motor whose rotation speed is controlled by PWM control is used as the CR motor 18, and a stepping motor or a DC motor is used as the LF motor.

Here, a method of calculating the moving speed of the carriage 14 in the printer thus constructed will be described. As described above, the sensor element 26 is provided with the two light emitting elements and the light receiving elements whose phases are shifted by 3/4 cycle, and therefore the detection signal (hereinafter referred to as the encoder signal) of FIG.
As shown in (2), there are two rectangular pulses ENC1 and ENC2 whose phases are shifted by 3/4 cycle.

When the CR motor 18 is controlled, the falling edge of ENC1 is detected and the following processing is performed. First,
The moving direction of the carriage 14 can be known depending on whether the value of ENC2 at the time of detecting the edge is high or low. In addition, each time the edge is detected, the position counter is incremented or decremented according to the moving direction, and the count number of clocks counted from the edge detection to the next edge detection is acquired as the capture value Tn. Then, the reciprocal of this capture value becomes a value corresponding to the moving speed of the carriage 14, and if the CR motor 18 is feedback-controlled so that the moving speed thus calculated becomes the desired moving speed, the carriage 14 can be moved at the desired speed. It can be moved.

[0010]

However, when the carriage 14 is moved at a low speed, there is a possibility that sufficient accuracy cannot be obtained by the above method. For example, when the sampling time (clock cycle) is 0.1 μsec and the encoder resolution is 150 dpi, 66660 d (d is 1
Dividing (representing 0-ary notation) by the capture value gives almost the actual moving speed (unit: ips).

In this case, as shown in FIG.
The capture value corresponding to ips is 2222d. The calculated speed at this time is 30.0000d, and its hexadecimal notation is 1E00 if it is expressed by a fixed point with 8 bits after the decimal point.
H, the fluctuation of the capture value when the speed fluctuates by 0.5% (hereinafter referred to as 0.5% fluctuation) is 26H. On the other hand, the capture value corresponding to the moving speed of 8 ips is 833.
3d, the calculated speed at that time is 7.9999d, the hexadecimal notation is 07FFH, and the 0.5% variation is 0AH.

Now, when an integer part of a value obtained by multiplying a calculated speed result by a predetermined feedback gain is used as the control amount to be operated as feedback control, 0.5 is used when the moving speed of the carriage 14 is controlled to 8 ips.
Since the% fluctuation is 0 AH, the speed fluctuation is 0.5%.
It will be difficult to fit within. Therefore, conventionally, it was difficult to control at low speed unless the gain in feedback control is increased. In addition, increasing the gain undesirably deteriorates responsiveness. Therefore, the present invention has been made for the purpose of providing a speed control device for a DC motor, which enables accurate speed control even when the drive target is moved at a low speed without increasing the gain in feedback control.

[0013]

Means for Solving the Problems and Effects of the Invention The invention according to claim 1 made in order to achieve the above object, is a drive target driven by a DC motor, and each time the drive target is driven by a predetermined amount. A signal generating means for generating a signal, a time measuring means for measuring a time interval of the signal generated by the signal generating means, and a speed for setting a speed component calculation parameter used for obtaining the speed component of the driven object. A speed at which the speed of the drive target is calculated by dividing the speed calculation parameter setting means set by the speed calculation parameter setting means and the speed calculation parameter set by the speed calculation parameter setting means by the time interval obtained by the time measuring means. Calculating means, target speed setting means for setting the target speed of the driven object, speed calculated by the speed calculating means and set by the target speed setting means Comparing the target speed, the feedback control means for performing feedback control of the DC motor so as to match the two, the speed control device of the DC motor, comprising, when the speed of the desired drive target is small, It is characterized in that the target speed is set to be large while the speed component calculation parameter is set to be large.

In the present invention thus constituted, the signal generating means generates a signal each time the drive target of the DC motor is driven by a predetermined amount, and the time measuring means measures the time interval of the signal. Then, the speed calculation means calculates the speed of the drive target by dividing the speed component calculation parameter set by the speed component calculation parameter setting means by the time interval obtained by the time measurement means. When the speed is calculated in this way, the feedback control means compares the calculated speed with the target speed set by the target speed setting means, and performs feedback control of the DC motor so as to match them.

According to the present invention, when the desired speed of the driven object is small, the speed component calculation parameter setting means sets the speed component calculation parameter large, and the target speed setting means also increases the target speed. Set. When the velocity component calculation parameter is set to a large value, the velocity obtained by dividing it by the above time interval also has a large value. For this reason, even when the speed of the drive target is actually small, the rate at which the numerical value is rounded in the calculation process decreases.
Since the target speed is also set to a large value in accordance with this, if the above feedback control is performed in order to match the two, even when the drive target is moved at a low speed, it is possible to accurately obtain the feedback control without increasing the gain in the feedback control. The speed can be controlled. That is, it is possible to accurately control the speed at a low speed without deteriorating the responsiveness.

According to a second aspect of the present invention, in addition to the configuration of the first aspect, the speed component calculation parameter and the target speed are set such that the ratios for increasing the speed component calculation parameter and the target speed are the same. It is characterized by setting and. In the present invention, since the ratio for increasing the speed component calculation parameter and the target speed are the same, it is possible to perform the control at the low speed without changing the gain, coefficient, etc. in the feedback control. Therefore, in the present invention, in addition to the effect of the invention described in claim 1, the effect that the processing can be further simplified occurs.

The invention according to claim 3 is the invention according to claim 1 or 2.
In addition to the described configuration, the drive target is a carriage on which a head is mounted. In a carriage equipped with a head, the moving speed of the carriage is directly reflected on the printing accuracy, so that there is a strong demand for accurately controlling the moving speed. In the present invention, since the moving speed of the carriage to be driven can be accurately controlled as described above,
The effects of the invention according to claim 1 or 2 are more prominent.

According to a fourth aspect of the present invention, in addition to the configuration of the third aspect, the signal generating means is a linear encoder or a rotary encoder that generates the signal in response to driving of the carriage in the main scanning direction. It is characterized by that. When the signal generating means is a linear encoder or a rotary encoder that generates the signal in response to the driving of the carriage in the main scanning direction, there is a mechanical limitation in improving the resolution. In the present invention, as described above,
Since the moving speed at low speed can be accurately controlled even with the same resolution, the effect of the invention according to claim 3 is more remarkable.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described. FIG. 1 is an explanatory diagram showing a configuration of an energization mechanism of a CR motor 18 as a DC motor to which the present invention is applied.
The CR motor 18 is used in a printer similar to the conventional printer shown in FIG. 5, and this embodiment is characterized by the control system of the CR motor 18 as described later.

As shown in FIG. 1, two switching elements S1, S2 and S3, S4 connected in series are connected in parallel between the positive electrode Pv and the negative electrode P0 of the power source, and each switching element S1. A flywheel diode FD is connected in parallel to S4. Note that such switching elements S1 to S4 can be obtained by connecting a flywheel diode FD to a switching element such as a PNP type or NPN type transistor. A function equivalent to a wheel diode is F as a parasitic diode.
Since it is configured inside the ET, it may not be provided outside.

One terminal of the CR motor 18 is connected between the switching element S1 and the switching element S2,
The other terminal is connected between the switching element S3 and the switching element S4. Therefore, the switching elements S1 and S4 are turned on and the switching elements S2 and S4 are turned on.
When 3 is turned off, the CR motor 18 can be normally rotated by supplying a drive current in the normal rotation direction (normal rotation drive current) to the CR motor 18. On the contrary, the switching elements S2, S3
By turning on the switching elements S1 and S4, the CR motor 18 can be reversed by supplying a reverse rotation current (reverse rotation drive current) to the CR motor 18 in the reverse rotation direction.

Further, by turning on / off the switching element in a pulse shape and controlling the average amount of current supplied to the CR motor 18, the CR motor 18 can be normally rotated at a constant speed or accelerated / decelerated. it can. Further, the CR motor 18 can be decelerated more quickly by supplying the reverse current. Therefore, in the present embodiment, the switching elements S1 to S4 are connected to the CR control block 33 described below via the CR drive circuit 31 and ON / OFF is controlled, so that the carriage 14 to be driven can be appropriately controlled. It is moving at speed.

As shown in FIG. 2, the CR control block 33.
Includes a clock generation unit 35 that generates a clock signal every 0.1 μsec and a PWM cycle timer 37 that counts the clock signal over a predetermined PWM cycle.
An operation mode setting register group 39 for storing the operation mode set by the CPU is provided.

The operation mode setting register group 39 includes a velocity component calculation parameter setting register 40 for storing velocity component calculation parameters required for velocity calculation of the carriage 14.
(Corresponding to speed component calculation parameter setting means), speed control start position setting register 4 for storing the start position of speed control
1, deceleration start position setting register 42 for storing deceleration start position, initial PWM value setting register 43 for storing initial value of PWM, acceleration coefficient setting register 4 for storing acceleration coefficient
4. Target speed setting register 45 (corresponding to target speed setting means) for storing target speed, differential gain setting register 46 for storing differential gain, integral gain setting register 47 for storing integral gain, proportional gain for storing proportional gain A setting register 48, a deceleration parameter setting register 49 that stores deceleration parameters, a reverse pulse parameter setting register 50 that stores reverse pulse parameters, and a wait time setting register 51 that stores wait times are provided. The meaning of each parameter will be described later.

In addition to the above, the CR control block 33 includes an encoder edge detection section 55, a position counter 57, a cycle counter 59, a comparison processing section 61, selectors 63 and 65, a speed conversion section 67, and an acceleration control section, which will be described below. 71, feedback calculation processing unit 7 as feedback control means
3, a PWM generator 75, and a deceleration controller 80.

The detection signal of the above-mentioned sensor element 26 is input to the encoder edge detection section 55, where the falling edge of ENC1 is detected. Encoder edge detector 5
The detection result of 5 is the position counter 57 and the cycle counter 59.
Entered in. The position counter 57 increases or decreases the count value corresponding to the position of the carriage 14 based on the detection result of the encoder edge detection unit 55, and inputs the count value to the comparison processing unit 61. The comparison processing unit 61 compares the count value with the speed control start position stored in the speed control start position setting register 41 and the deceleration start position stored in the deceleration start position setting register 42, and the comparison result will be described later. Input to the selectors 63 and 65.

Further, the cycle counter 59 counts the time interval at which the above-mentioned edge is detected by the encoder edge detection section 55 and inputs it to the speed conversion section 67. That is, when the encoder edge detection unit 55 detects the above-mentioned edge, the number of clocks (hereinafter, referred to as a capture value) generated between the detection of the edge immediately before and the detection of the edge is counted and input to the speed conversion unit 67.

The speed conversion section 67 calculates the moving speed of the carriage 14 by dividing the speed component calculation parameter stored in the speed component calculation parameter setting register 40 by the input capture value. That is,
The cycle counter 59 corresponds to the time measuring means, and the speed converting section 67 corresponds to the speed calculating means.

Based on the initial PWM value stored in the initial PWM value setting register 43 and the acceleration coefficient stored in the acceleration coefficient setting register 44, the acceleration control unit 71 sets the CR
A duty value or the like for controlling the acceleration of the motor 18 in an open loop is calculated and input to the selector 63.

The feedback calculation processing section 73 sets the speed calculated by the speed converting section 67 to the target speed setting register 4
5 calculates the duty value and the like for performing feedback control to match the target speed stored in the selector 63.
To enter. Note that this calculation is performed by the differential gain setting register 46, the integral gain setting register 47,
And the data stored in the proportional gain setting register 48.

The selector 63 outputs the signal from the acceleration control section 71 to the PWM generation section 75 until the comparison processing section 61 receives an input indicating that the carriage 14 has reached the speed control start position.
After that, the signal from the feedback calculation processing unit 73 is input to the PWM generation unit 75. P
The WM generation unit 75 generates a signal to be input to the CR drive circuit 31 based on the input signal and outputs the signal to the selector 65.
To enter.

On the other hand, the deceleration control unit 80 uses the deceleration parameter stored in the deceleration parameter setting register 49, the reverse rotation pulse parameter stored in the reverse rotation pulse parameter setting register 50, and the wait time stored in the wait time setting register 51. Based on the above, a signal (for input to the CR drive circuit 31) for controlling the deceleration of the CR motor 18 in an open loop is generated and input to the selector 65.
That is, the deceleration control unit 80 gradually reduces the duty value according to the deceleration parameter and generates a reverse pulse (pulse-shaped reverse current) having a pulse width according to the reverse pulse parameter at a timing according to the wait time. By doing so, the control for decelerating the CR motor 18 is performed.

The selector 65 inputs the signal from the PWM generating section 75 to the CR drive circuit 31 until the comparison processing section 61 receives an input indicating that the carriage 14 has reached the deceleration start position, and the above-mentioned input is made. After that, the signal from the deceleration control unit 80 is input to the CR drive circuit 31. By the operation of the selector 65 and the selector 63, as shown in FIG. 3, in the acceleration section until the carriage 14 reaches the speed control start position, the CR motor 18 is open loop according to the processing of the acceleration control unit 71. The CR motor 18 is feedback-controlled according to the processing of the feedback calculation processing unit 73 in the constant speed section from the speed control start position to the deceleration start position, and the processing of the deceleration control unit 80 in the deceleration section after the deceleration start position. Accordingly, the CR motor 18 is deceleration-controlled in an open loop.

Next, the configuration and processing of the feedback calculation processing section 73 will be described in more detail. Figure 4
It is a block diagram showing the structure of the feedback calculation processing part 73 in detail. As shown in FIG. 4, the speed calculated by the speed converter 67 and the target speed stored in the target speed setting register 45 are input to the adder 81, and the difference between the two is subjected to amplification by the proportional gain 83. Then, it is input to the adder 85. In addition, the difference output from the adder 81 is
After being integrated by the integrator 91 and being amplified by the integral gain 93, it is input to the adder 85. Furthermore, the speed conversion unit 6
The speed calculated in 7 is also input to the differentiator 95, differentiated here, and then amplified by the differential gain 97, and then input to the adder 85.

The adder 85 adds the input values from the proportional gain 83 and the integral gain 93 and subtracts the input value from the differential gain 97 therefrom. The feedback calculation processing unit 73, based on the output from the adder 85,
A duty value or the like for feedback controlling the motor 18 is calculated and input to the selector 63. The amplification factors in the proportional gain 83, the integral gain 93, and the differential gain 97 are set to the values stored in the proportional gain setting register 48, the integral gain setting register 47, and the differential gain setting register 46. Further, in the calculation of each of the above parts in the feedback calculation processing unit 73, the number of decimals is 8
The calculation result is rounded with the precision of t.

In the present embodiment configured as described above,
The accuracy of the feedback control is improved by changing the setting values of the speed component calculation parameter and the target speed as follows according to the desired speed in the constant speed section (see FIG. 3). In the present embodiment, the resolution of the linear encoder (corresponding to the signal generating means) composed of the timing slit 24 and the sensor element 26 is 150 dp.
Let i be i.

When the desired speed is 30 ips, the speed component calculation parameter is 66660d. Then, the speed calculated by the speed conversion unit 67 becomes the actual moving speed of the carriage 14 (unit: ips). In this case, as shown in FIG. 7A, the capture value corresponding to 30 ips is 2222d, and the calculation speed is 30.0000.
d, its hexadecimal notation is 1E00H, 0.5% fluctuation is 2
It becomes 6H. Therefore, in the feedback calculation processing unit 73, by setting the feedback gain such that the result of applying the feedback gain to the 0.5% fluctuation amount 26H becomes 100H or more, the 0.5% fluctuation amount is controlled by the control amount. Will be reflected as the carriage 14
Can be well controlled within a range of ± 0.5% with respect to the desired speed.

On the other hand, when the desired speed is 8 ips,
The velocity component calculation parameter is quadrupled to 266640d. In this case, as shown in FIG. 7B, the capture value corresponding to 8 ips is 8333d regardless of the speed component calculation parameter, but the calculated speed corresponding to the capture value is 31.9981d, which is in hexadecimal notation. Is 1 FFF
H, 0.5% variation is 28H. Therefore, even if the desired speed is 8 ips, the desired speed is set to 30 by setting the set value of the target speed to 32.0000d, which is four times as large.
Similar to the case of ips, it can be controlled well within a range of ± 0.5%.

As described above, in this embodiment, even when the carriage 14 is moved at a low speed, accurate feedback control can be performed without increasing the gain or increasing the resolution of the linear encoder. . That is, the carriage 1 does not deteriorate in responsiveness even at low speed.
The speed of 4 can be accurately controlled to improve the printing accuracy of the printer.

The present invention is not limited to the above-described embodiments, and can be implemented in various forms without departing from the gist of the present invention. For example, a rotary encoder that detects the rotation angle of the CR motor 18 can be used as the signal generating means. Further, in the above-described embodiment, the configuration of a so-called differential preceding PID controller is adopted as the feedback calculation processing unit 73, but a configuration of a general PID controller or a proportional differential preceding PID controller is adopted. May be.

Further, in the above embodiment, the carriage 1
Although the process of setting the speed component calculation parameter to be large when the No. 4 is moved at a low speed and the process of setting the target speed to be large are individually performed, these processes may be performed at the same time.
For example, a multiplier is provided between the target speed setting register 45 and the feedback calculation processing unit 73, and the set value of the speed component calculation parameter setting register 40 (or a constant multiple thereof:
In the above example, 1 / 66660d times) may be input to the multiplier.

Further, it goes without saying that the present invention can also be applied to a speed control device for a DC motor that drives various types of driving objects other than the carriage 14.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of an energization mechanism of a CR motor according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a CR control block of the energizing mechanism.

FIG. 3 is an explanatory diagram showing a change in a control section by the CR control block.

FIG. 4 is a block diagram showing a configuration of a feedback calculation processing section of the CR control block.

FIG. 5 is an external view showing a partial mechanism of the present embodiment or a general printer.

FIG. 6 is an explanatory diagram showing the principle of speed detection in the printer.

FIG. 7 is an explanatory diagram showing speed calculation results of the present embodiment and a conventional example.

[Explanation of symbols]

12 ... Printing paper 14 ... Carriage
18 ... CR motor 20 ... print head 24 ... timing slit
26 ... Sensor element 31 ... CR drive circuit 33 ... CR control block
35 ... Clock generator 37 ... PWM cycle timer 39 ... Operation mode setting register group 40 ... Speed component calculation parameter setting register 41 ... Speed control start position setting register 42 ... Deceleration start position setting register 43 ... Initial PWM value setting register 44 ... Acceleration Coefficient setting register 45 ... Target speed setting register 46 ... Differential gain setting register 47 ... Integral gain setting register 48 ... Proportional gain setting register 49 ... Deceleration parameter setting register 50 ... Reverse pulse parameter setting register 51 ... Wait time setting register 55 ... Encoder edge Detection unit 57 ... Position counter 59 ... Cycle counter
61 ... Comparison processing unit 63, 65 ... Selector 67 ... Speed conversion unit
71 ... Acceleration control unit 73 ... Feedback calculation processing unit 80 ... Deceleration control unit 81 ... Adder 83 ... Proportional gain 85 ... Adder
91 ... Integrator 93 ... Integral gain 95 ... Differentiator
97 ... Differential gain

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2C480 CA01 CA33 CA34 CA47 CB02                       CB34 EA06 EA12 EA23                 5H571 AA06 BB07 BB10 EE01 EE02                       GG02 HA09 HB01 HC02 JJ03                       JJ13 JJ17 JJ18 JJ22 JJ23                       KK06 LL07 LL33

Claims (4)

[Claims] 1. A drive target driven by a DC motor, a signal generating means for generating a signal each time the drive target is driven by a predetermined amount, and a time interval between signals generated by the signal generating means. And a speed component calculation parameter setting means for setting a speed component calculation parameter used to obtain the speed component of the drive target, and a speed component calculation parameter set by the speed component calculation parameter setting means By dividing by the time interval obtained by the time measuring means, a speed calculating means for calculating the speed of the driven object, a target speed setting means for setting the target speed of the driven object, and the speed calculating means. The calculated speed is compared with the target speed set by the target speed setting means, and feedback control of the DC motor is performed so as to match the two. A feedback control means for performing, and a direct current motor speed control device comprising: When the desired speed of the driven object is small, the speed component calculation parameter is set to be large, and the target speed is also set to be large. DC motor speed control device characterized by: 2. The direct current according to claim 1, wherein the speed component calculation parameter and the target speed are set such that the ratios for increasing the speed component calculation parameter and the target speed are the same. Motor speed control device. 3. The speed control device for a DC motor according to claim 1, wherein the drive target is a carriage on which a head is mounted. 4. The speed control of a DC motor according to claim 3, wherein the signal generating means is a linear encoder or a rotary encoder that generates the signal in response to driving of the carriage in the main scanning direction. apparatus.