JP7543018B2 - Information media processing device and motor control method - Google Patents

Description

The present invention relates to an information media processing device, such as a card reader, that performs at least one of reading and writing data from and to an information media such as a magnetic card, and a motor control method that can be used in such an information media processing device.

When reading and writing data from a magnetic recording medium such as a magnetic card, the magnetic recording medium must be moved relative to the magnetic head at a specified speed. Fluctuations in the relative speed of the magnetic recording medium relative to the magnetic head may result in recording defects on the magnetic recording medium or read failures. In magnetic recording devices such as card readers, magnetic recording media such as magnetic cards are usually moved relative to the magnetic head by a transport roller driven by a motor. Since fluctuations in the rotational speed of the motor are directly linked to fluctuations in the moving speed of the magnetic recording medium, a control method is required that can precisely control the rotational speed of the motor. Even when moving the information medium relative to an information medium other than a magnetic recording medium to read and write data, it is necessary to precisely control the rotational speed of the motor that transports the information medium.

Patent document 1 discloses that in a magnetic recording device, an encoder is attached to the motor to obtain a timing signal corresponding to the rotation speed of the motor, i.e., the movement speed of the magnetic recording medium, and a clock signal is generated that defines the timing of writing data to the magnetic head according to the interval of the timing signal. In patent document 1, the clock signal is generated based on the timing signal, but it is also possible to control the motor rotation speed to be kept constant by feeding back the timing signal from the encoder.

An encoder attached to a motor generally comprises a disk attached to the motor's rotating shaft and a number of slits extending radially in the disk, which are arranged at equal intervals along the circumference of the disk. When a light-emitting section is placed on one side of such a disk and a light-receiving section on the other, the light entering the light-receiving section is interrupted as the disk rotates. The light-receiving section generates a pulse signal that corresponds to whether or not light is entering. For example, the light-receiving section generates a binary pulse signal that is "1" or on when light is entering, and "0" or off when no light is entering. In this binary pulse signal, "0" and "1" are inverted each time the amount of rotation of the disk increases by the width of the slit. Therefore, the frequency of the pulse signal is proportional to the rotation speed of the disk. Even non-optical encoders generally output binary pulse signals with frequencies proportional to the speed of motion.

Japanese Unexamined Patent Publication No. 7-130099

In an optical encoder with a disk, periods in which the light receiving section detects light and periods in which it does not detect light alternate, and the pulse signal output by the light receiving section rises when the period in which light is not detected transitions to the period in which it is detected, and falls when the period in which light is detected transitions to the period in which it is not detected. The period from the rising edge to the falling edge of this signal, i.e., the length of the period in which light is detected, is called the on-period, and the period from the falling edge to the rising edge, i.e., the period in which light is not detected, is called the off-period. When using an encoder with a disk, it is preferable that the on-period and off-period appear with a duty ratio of 50% when the disk rotates at a constant rotation speed. If the duty ratio is 50%, the rotation speed of the motor can be controlled at a high frequency by controlling the rotation speed of the motor depending on the length of the on-period immediately before the falling edge of the signal, and then controlling the rotation speed of the motor depending on the length of the off-period immediately before the rising edge of the signal. However, in reality, due to limitations in the machining precision of the slits and variations in the light detection sensitivity of the light receiving section, the duty ratio does not reach 50% even when the disk rotates at a constant rotational speed, and the length of the on period and the length of the off period often do not match.

Even if the rotation speed is constant, when the length of the on period and the length of the off period do not match, if the rotation speed of the motor is controlled at the rising and falling edges of the signal as described above, small fluctuations will occur in the rotation speed of the motor, making it unsuitable for transporting magnetic recording media. Therefore, in the past, the rotation speed of the motor was controlled based on the duration of one cycle (i.e., one cycle of the binary pulse signal output by the light receiving unit) that is the sum of the on period and the off period. In this case, the control time interval is doubled compared to when the duty ratio can be set to 50%, which is disadvantageous in terms of high-frequency control of the motor rotation speed. Increasing the number of slits provided in the disk for high-frequency control, coupled with the narrowing of the width of each slit, will increase the processing cost. It is possible to approach the duty ratio of 50% by adjusting the sensor sensitivity of the light receiving unit, but the adjustment will increase the number of work steps. Even with encoders other than optical encoders with disks, if the duty ratio is not 50% in the binary pulse signal output during uniform motion, the problems described here will occur.

The object of the present invention is to provide an information media processing device that uses an encoder to detect the speed of a motor used to transport information media such as magnetic recording media, and that can precisely control the moving speed of the information media even when the duty ratio of the binary pulse signal output by the encoder during uniform motion is not 50%, and a motor control method that can be used with such an information media processing device.

The information media processing device of the present invention has a magnetic head, a transport roller for transporting a magnetic card , a motor for driving the transport roller, and an encoder that outputs a binary pulse signal according to the amount of rotation of the motor, and performs at least one of reading and writing data from and to the magnetic card using the magnetic head while transporting the magnetic card at a constant speed relative to the magnetic head.The information media processing device has a processing unit that detects rising and falling edges in the pulse signal, and calculates a first value which is the length of the period from the previous rising edge each time a rising edge is detected, and a second value which is the length of the period from the previous falling edge each time a falling edge is detected, and a control circuit that controls the motor so that the magnetic card is transported at a constant speed based on the first value each time the first value is obtained, and controls the motor so that the magnetic card is transported at a constant speed based on the second value each time a second value is obtained.

In the information media processing device of the present invention, a first value indicating the interval between rising edges in a pulse signal from an encoder is obtained, and a second value indicating the interval between falling edges is obtained, and the motor is controlled based on these values. Since both the first value and the second value indicate the length of one period of the pulse signal, the duty ratio of the pulse signal is not affected by being not 50%. On the other hand, since control is performed every time the first value is obtained and control is performed every time the second value is obtained, control is performed twice per period of the pulse signal, so that control is performed frequently and the motor can be controlled with high accuracy. In particular, the information media processing device of the present invention makes it possible to stably read and write data from and to a magnetic card.

In the information media processing device of the present invention, the processing unit may calculate a value obtained by halving the first value and a value obtained by halving the second value, and the control circuit may control the motor using the value obtained by halving the first value and the value obtained by halving the second value. With this configuration, it becomes possible to use the conventional control routine that assumes that the duty ratio of the pulse signal is 50%.

In the information media processing device of the present invention, the encoder is, for example, an optical encoder having a disk connected to the rotating shaft of a motor , and generates a single binary pulse signal . If the present invention is applied to an optical encoder having a disk, the number of slits provided in the disk can be halved to obtain the same control accuracy, assuming that the duty ratio of the pulse signal is not 50%, and therefore it is possible to reduce the manufacturing cost of the encoder.

The motor control method of the present invention is a motor control method that controls the speed of a motor using an encoder that outputs a binary pulse signal according to the amount of rotation of the motor, so that the magnetic head can at least one of read and write data from the magnetic card while the magnetic head transports the magnetic card at a constant speed using a transport roller driven by the motor, and determines a first value which is the length of the period from the previous rising edge each time a rising edge in the pulse signal is detected, and determines a second value which is the length of the period from the previous falling edge each time a falling edge in the pulse signal is detected, and controls the motor so that the magnetic card is transported at a constant speed according to the first value each time the first value is obtained, and controls the motor so that the magnetic card is transported at a constant speed according to the second value each time a second value is obtained.

In the motor control method of the present invention, both the first value indicating the interval between rising edges and the second value indicating the interval between falling edges indicate the length of one period of the pulse signal, so there is no effect of the duty ratio of the pulse signal being not 50%. On the other hand, since control is performed each time the first value is obtained and control is performed each time the second value is obtained, control is performed twice per period of the pulse signal, so control is executed frequently and it becomes possible to control the motor speed with high precision.

In the motor control method of the present invention, a value obtained by halving the first value and a value obtained by halving the second value may be calculated, and the motor may be controlled using the value obtained by halving the first value each time the first value is obtained, and the motor may be controlled using the value obtained by halving the second value each time the second value is obtained. If configured in this way, it becomes possible to use a conventional motor speed control routine that is based on the assumption that the duty ratio of the pulse signal is 50%.

In the motor control method of the present invention, the encoder is, for example, an optical encoder having a disk connected to the rotating shaft of the motor , and generates a single binary pulse signal . If the present invention is applied to an optical encoder having a disk, the number of slits provided in the disk can be halved to obtain the same control accuracy, assuming that the duty ratio of the pulse signal is not 50%, so that the control accuracy can be improved without increasing the number of slits provided in the disk.

According to the present invention, there is provided an information media processing device that uses an encoder to detect the speed of a motor used to transport an information medium, such as a magnetic recording medium, and that can precisely control the moving speed of the information medium even when the duty ratio of the binary signal output by the encoder during uniform motion is not 50%, as well as a motor control method that can be applied to such an information media processing device.

FIG. 2 is a diagram illustrating a motor control method according to the present invention. 1 is a block diagram illustrating a card reader according to an embodiment of the present invention;

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram for explaining a motor control method based on the present invention, in which (a) is a diagram showing the schematic configuration of an optical encoder having a disk, (b) and (c) are waveform diagrams showing examples of pulse signals output from the encoder, (d) is a waveform diagram explaining a conventional processing method, and (e) is a waveform diagram explaining a method of processing signals from the encoder to execute the motor control method based on the present invention.

The encoder 1 includes a disk 11 that rotates by being connected to the rotating shaft of a motor, a number of slits 12 provided on the disk 11, a light-emitting unit 13 that includes a light-emitting diode or the like and emits light, and a light-receiving unit 14 that includes a light-receiving element. The disk 11 is also called a slit plate. The slits 12 are arranged at equal intervals along the circumferential direction of the disk 11. The light-emitting unit 13 and the light-receiving unit 14 are arranged so that the disk 11 is sandwiched between them and the light from the light-emitting unit 13 passes through the slits 5 and enters the light-receiving unit 14. The light from the light-emitting unit 13 is blocked by the disk 11, but enters the light-receiving unit 14 when the slit 12 is located on the optical path. As a result, the light entering the light-receiving unit 14 becomes intermittent each time the amount of rotation of the disk 11 increases by the width of the slits 5.

The light receiving unit 14 generates a binary pulse signal S that is "1" when light is incident and "0" when light is not incident. Ideally, when the disk 11 rotates at a constant rotation speed, as shown in FIG. 1(b), the length A of the period (on period) when this pulse signal S is "1" is equal to the length B of the period (off period) when it is "0" (i.e., A=B), and the duty ratio is 50%. However, in reality, due to the influence of the processing accuracy of the slit 12 and the sensitivity of the light receiving element in the light receiving unit 14, as shown in FIG. 1(c), even when the disk 11 rotates at a constant rotation speed, the length A of the on period and the length B of the off period in the pulse signal S are not equal (i.e., A≠B). In the following description, when the duty ratio of the pulse signal S is mentioned, it refers to the duty ratio in the pulse signal S when it is assumed that there is no fluctuation in the rotation speed of the disk 11, that is, the disk 11 rotates at a constant rotation speed.

When the length A of the on period and the length B of the off period are not equal, conventionally, as shown in FIG. 1(d), only the rising edge or the falling edge of the pulse signal S output from the light receiving unit 14 is detected, and a binary pulse signal T whose value is inverted each time it is detected is generated. The duty ratio of the pulse signal T is 50%, and the length of the period in which the value of the pulse signal T is "1" is equal to the length of the period in which the value is "0", so that, for example, the rotation speed of a motor is controlled based on the length t of the period in which the value is "1". However, the signal processing method shown in FIG. 1(d) is nothing more than dividing the pulse signal S output by the light receiving unit 4 by 1/2, and the detection accuracy is halved relative to the width of the main body of the slit 12 in the disk 11.

In the processing method according to the present invention, as shown in FIG. 1(e), both the rising and falling edges of the pulse signal S from the light receiving unit 14 are detected, and both the length of the period X from the rising edge to the next rising edge and the length of the period Y from the falling edge to the next falling edge are calculated. In the following description, the length of the period X is represented by X, and the length of the period Y is represented by Y, unless otherwise confused. Since the rising and falling edges of the pulse signal S alternate, the period Y starts in the middle of the period X, and the periods X and Y overlap. Then, when a rising edge is detected, half the length of the period X ending at that edge, that is, X/2, is calculated, and the calculated X/2 is fed back to control the motor speed. Similarly, when a falling edge is detected, half the length of the period Y ending at that edge, that is, Y/2, is calculated, and the calculated Y/2 is fed back to control the motor speed.

Although it also depends on the fluctuation of the rotation speed of the motor, X/2 and Y/2 are approximately equal to the length A of the on period and the length B of the off period in the case shown in FIG. 1(b) where the duty ratio of the pulse signal S is 50%. If the fluctuation of the rotation speed of the motor can be ignored, X/2 and Y/2 are equal to the length A of the on period and the length B of the off period in the case of A=B, respectively. This means that even if the duty ratio of the pulse signal S actually deviates from 50%, the motor speed can be controlled frequently as if the duty ratio were 50%. Therefore, when controlling the speed of an information medium, such as a magnetic recording medium, using the process shown here, the moving speed of the information medium can be precisely controlled even if the duty ratio of the pulse signal S output from the encoder 1 is not 50%.

In the above explanation, when the period X is obtained by detecting the rising edge, X/2 is calculated, and when the period Y is obtained by detecting the falling edge, Y/2 is calculated. X and Y are halved, but this is to enable control to be performed using the same control parameters as the control when the duty ratio of the pulse signal S shown in FIG. 1(b) is 50%. Halving X and Y is equivalent to multiplying X and Y by a constant of 1/2, but multiplying X and Y by the same constant does not affect the main points of control, so it is also possible to perform calculations for control using the lengths of the periods X and Y themselves. In the method based on the present invention, when the period X is obtained, the speed of the motor is controlled based on the length of the period X, and when the period Y is obtained, the motor is controlled based on the length of the period Y.

The motor control method of the present invention described above is a control method suitable for transporting information media such as magnetic recording media at a constant speed in information media processing devices such as magnetic recording devices, but it can also be used to control motors that are installed in devices other than information media processing devices and that need to be driven at a constant speed.

Figure 2 shows the configuration of a card reader that performs at least one of reading and writing data from a magnetic card, which is a magnetic recording medium, as an example of an information media processing device based on the present invention. The card reader of this embodiment is mounted on a host device such as an ATM (Automated Teller Machine) and used. The card reader includes a control circuit 20 that controls the operation of the card reader and inputs and outputs data to and from the host device, a magnetic head 21, a read/write circuit 22 provided between the magnetic head 21 and the control circuit 20, a transport roller 31 for transporting a magnetic card within the card reader, a motor 32 that drives the transport roller 31, and a motor control circuit 23 that drives the motor 32 by the output from the control circuit 20. The control circuit 20 is configured, for example, by a microprocessor. The transport roller 31 may be connected to the rotating shaft 33 of the motor 32, or may be connected to the rotating shaft 33 of the motor 32 via a drive transmission mechanism consisting of a pulley, a belt, gears, etc. In the card reader, the rotation speed of the motor 32 is controlled by the control method described using Figure 1.

The encoder 1 described with reference to FIG. 1 is attached to the rotating shaft 33 of the motor 32. The rotation of the motor 32 rotates the disk 11 in the encoder 1, and a pulse signal S is output from the light receiving unit 14 in the same manner as described above. The pulse signal S is input to the speed calculation unit 24 provided in the control circuit 20. The speed calculation unit 24 calculates the rotation speed of the motor 32 by calculating X/2 and Y/2 described in FIG. 1(e) from the pulse signal S and calculating their reciprocals. The control circuit 20 compares the calculated rotation speed with a preset rotation speed and outputs a drive command to the motor drive circuit 23 to drive the motor 32 so that the rotation speed of the motor 32 becomes the set value. When the control circuit 20 is configured by a microprocessor, the speed calculation unit 24 can be realized by a software routine executed on the microprocessor 24. Since the calculation of the reciprocals of X/2 and Y/2 involves a large computational load, the speed calculation unit 24 may calculate only the values of X/2 and Y/2, and the control circuit 20 may compare the reciprocal of the set speed with X/2 and Y/2 to control the motor 32.

In the card reader of this embodiment, even if the duty ratio of the pulse signal S output by the encoder 1 is not 50%, the speed of the motor 32 can be controlled at the timing of both the rising edge and the falling edge of the pulse signal S without causing small fluctuations in the rotation speed of the motor 32. As a result, it is possible to more precisely control the speed of the transported magnetic card, reducing failures in reading data from the magnetic card and defects in recording to the magnetic card.

Although the above describes a case where the information media processing device is a card reader, the information media processing device based on the present invention may also read and write data from magnetic recording media such as bankbooks with magnetic stripes and various tickets with magnetic recording surfaces. Furthermore, the information media processing device based on the present invention may also read and/or write data from recording media other than magnetic recording media, such as optical recording media. In addition, the encoder does not have to be an optical encoder with a disk, as long as it generates a binary pulse signal with a frequency proportional to the motor speed. In the present invention, for example, an encoder that combines a magnet and a Hall element can also be used.

1...Encoder; 11...Disc; 12...Slit; 13...Light emitter; 14...Light receiver; 20...Control circuit; 21...Magnetic head; 22...Read/write circuit; 23...Motor drive circuit; 24...Speed calculation unit; 31...Transport roller; 32...Motor; 33...Rotating shaft.

Claims (6)

An information medium processing device comprising a magnetic head, a transport roller for transporting a magnetic card , a motor for driving the transport roller, and an encoder for outputting a binary pulse signal in accordance with an amount of rotation of the motor , the information medium processing device transporting the magnetic card at a constant speed relative to the magnetic head and at least one of reading and writing data from and to the magnetic card by the magnetic head ,
a processing unit that detects a rising edge and a falling edge in the pulse signal, and calculates a first value that is a length of a period from the previous rising edge each time the rising edge is detected, and calculates a second value that is a length of a period from the previous falling edge each time the falling edge is detected;
a control circuit that controls the motor so that the magnetic card is transported at the constant speed based on the first value each time the first value is obtained, and controls the motor so that the magnetic card is transported at the constant speed based on the second value each time the second value is obtained;
An information media processing device having the above configuration. The processing unit calculates a value obtained by halving the first value and a value obtained by halving the second value,
2. The information media processing device according to claim 1, wherein the control circuit controls the motor using a value obtained by halving the first value and a value obtained by halving the second value. 3. The information media processing device according to claim 1 , wherein the encoder is an optical encoder having a disk connected to a rotating shaft of the motor, and generates the single binary pulse signal . A motor control method for controlling a speed of a motor using an encoder that outputs a binary pulse signal according to an amount of rotation of the motor, in order to carry a magnetic card toward a magnetic head at a constant speed while the magnetic head carries the magnetic card toward the magnetic head, the motor comprising:
determining a first value that is a length of a period from a previous rising edge every time a rising edge is detected in the pulse signal;
determining a second value that is a length of a period from a previous falling edge of the pulse signal every time the falling edge of the pulse signal is detected;
controlling the motor so that the magnetic card is transported at the constant speed according to the first value each time the first value is obtained;
a motor control method for controlling the motor so that the magnetic card is transported at the constant speed according to the second value each time the second value is obtained. Calculating a value obtained by halving the first value and a value obtained by halving the second value;
each time the first value is obtained, the motor is controlled using a value that is half the first value;
5. The motor control method according to claim 4 , further comprising the step of controlling the motor using a value obtained by halving the second value each time the second value is obtained. 6. The motor control method according to claim 4 , wherein the encoder is an optical encoder having a disk connected to a rotating shaft of the motor, and generates the single binary pulse signal .

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