JP2012191810A - Ripple extractor, vehicle seat and ripple extraction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect ripple components included in current signals of a motor without using a cutoff frequency variable type filter.SOLUTION: A ripple extractor 3 extracts ripple components including in current signals of a motor 2. The ripple extractor 3 includes: a current/voltage converter 10 for converting the current signals of the motor 2 to voltage signals; a filter 40 for filtering the voltage signals converted by the current/voltage converter 10 and attenuating the ripple components; and a differential amplifier 50 for taking a difference between the voltage signals converted by the current/voltage converter 10 and output signals of the filter 40.

Description

  The present invention relates to a ripple extraction device, a vehicle seat, and a ripple extraction method.

  A movable part is provided in a vehicle seat, an electric door mirror, a power window, and the like, and the movable part is driven by a motor. In order to accurately control the position and speed of the movable part by the control device, it is necessary to detect the rotational position of the motor in operation. A sensor is used to detect the rotational position of the motor. That is, a sensor (for example, a hall element, an encoder, a reed switch sensor) is provided in a motor or the like, a signal synchronized with the rotation of the motor in operation is output by the sensor, and the output signal of the sensor is detected by a detection circuit (for example, a comparator or It is input to the control device via the AD converter.

  However, using a sensor increases the cost. Thus, a technique has been proposed in which the rotational position of the motor is detected by a circuit subsequent to the motor using a motor current signal without using a sensor (see, for example, Patent Document 1 and Patent Document 2). When the motor is operating, the current signal of the motor includes a direct current component, a low frequency component, a high frequency noise, and the like, and further, a pulsation synchronized with the rotation of the motor (hereinafter referred to as ripple). ) Ingredients are also included. In the techniques described in Patent Document 1 and Patent Document 2, a ripple component is extracted by processing a current signal of a motor by a subsequent circuit. Specifically, a DC component, a low frequency component, and a high frequency noise are removed from the motor current signal by a filter in the subsequent circuit, and the ripple component is passed. Since the frequency of each component of the motor current signal fluctuates due to environmental changes, a switched capacitor filter capable of varying the cut-off frequency is used as the filter of the subsequent circuit. Specifically, a signal that has passed through the switched capacitor filter is fed back to the arithmetic circuit, and the arithmetic circuit calculates a cutoff frequency from the feedback signal to set the cutoff frequency of the switched capacitor filter.

Japanese Patent Laid-Open No. 2003-9585 JP 2008-283762 A

However, switched capacitor filters are expensive.
In the conventional technology, the cutoff frequency of the switched capacitor filter is set by feedback control. Therefore, if the frequency of each component of the motor current signal changes transiently or rapidly, the cutoff frequency is set. May be delayed and the ripple component may not be detected accurately.
Therefore, the problem to be solved by the present invention is included in the motor current signal without using the variable cutoff frequency filter, even if the frequency of each component of the motor current signal fluctuates due to environmental changes. It is to be able to accurately detect the ripple component.

  The invention according to claim 1 for solving the above problems is a ripple extraction device in which a ripple extraction device extracts a ripple component contained in a current signal of a motor, and converts the current signal of the motor into a voltage signal. A current-to-voltage converter, a filter for filtering the voltage signal converted by the current-voltage converter, a differential amplifier for taking a difference between the voltage signal converted by the current-voltage converter and an output signal of the filter And a ripple extraction device.

  The invention according to claim 2 is the ripple extraction device according to claim 1, wherein the filter attenuates a ripple component in the voltage signal converted by the current-voltage converter.

  According to a third aspect of the present invention, the filter is converted by the current-voltage converter so that the lower the frequency of the component included in the voltage signal converted by the current-voltage converter, the lower the attenuation factor. The ripple extraction device according to claim 1, wherein the ripple extraction device is a low-pass filter that attenuates a voltage signal.

  The invention according to claim 4 is the ripple extraction device according to claim 3, wherein a cutoff frequency of the filter is set lower than a frequency of the ripple component.

  According to a fifth aspect of the present invention, the filter is converted by the current-voltage converter so that the attenuation rate is higher as the frequency of the component included in the voltage signal converted by the current-voltage converter is lower. The ripple extraction device according to claim 1, wherein the ripple extraction device is a high-pass filter that attenuates a voltage signal.

  The invention according to claim 6 is the ripple extraction device according to claim 5, wherein a cutoff frequency of the filter is set higher than a frequency of the ripple component.

  The invention according to claim 7 is such that the filter has a higher attenuation factor as the frequency of the component included in the voltage signal converted by the current-voltage converter in the low frequency region below the low cutoff frequency is lower. The frequency of the component included in the voltage signal converted by the current-voltage converter in a high frequency range that attenuates the voltage signal converted by the current-voltage converter and exceeds a high cutoff frequency higher than the low cutoff frequency The voltage signal converted by the current-voltage converter is attenuated such that the lower the value is, the lower the attenuation factor, and the current-voltage converter in the frequency band between the low cutoff frequency and the high cutoff frequency. The ripple extraction device according to claim 1, wherein the ripple extraction device is a bandpass filter that passes the converted voltage signal. .

  The invention according to claim 8 is the ripple extraction device according to claim 7, wherein the low cutoff frequency of the filter is set higher than the frequency of the ripple component.

  The invention according to claim 9 is the ripple extraction device according to claim 7, wherein the high cutoff frequency of the filter is set lower than the frequency of the ripple component.

  The invention according to claim 10 is the ripple extraction device according to any one of claims 1 to 9, wherein the filter is a filter including one or a plurality of resistors and capacitors.

  An invention according to an eleventh aspect includes a seat body having a movable part, the ripple extracting device according to any one of the first to tenth aspects, and the motor, and the movable part is driven by the motor. This is a vehicle seat.

  The invention according to claim 12 is a ripple extraction method for extracting a ripple component included in a current signal of a motor, wherein the current signal of the motor is converted into a voltage signal, the converted voltage signal is filtered, It is a ripple extraction method that takes a difference between a converted voltage signal and the filtered voltage signal.

According to the first, second, and twelfth aspects, when the voltage signal converted by the current-voltage converter is filtered by the filter, the ripple component is attenuated. Since the difference between the voltage signal of the current-voltage converter and the output signal of the filter is obtained by the differential amplifier, the difference becomes a ripple component. Even if the frequency of each component of the motor current signal fluctuates due to environmental changes, the obtained ripple component is the difference between the voltage signal of the current-voltage converter and the output signal of the filter, so it is included in the motor current signal A ripple component can be detected with high accuracy.
In addition, since the ripple component is extracted using the filter and the differential amplifier, it is not necessary to use a variable cutoff frequency filter as the filter. Therefore, the cost of the filter can be reduced.
Since this ripple extraction device is not a closed loop circuit such as a feedback control circuit, even if the frequency of each component of the motor current signal changes transiently or rapidly, the ripple component can be detected accurately.

  According to the third and fourth aspects of the present invention, if the voltage signal converted by the current-voltage converter is obtained by superimposing a ripple component and a low-frequency component having a frequency lower than that of the ripple component, the current of the motor Even if the frequency of each component of the signal changes due to environmental changes, the ripple component is accurately detected as a difference by the differential amplifier.

  According to the fifth and sixth aspects of the present invention, if the voltage signal converted by the current-voltage converter is obtained by superimposing a ripple component and a high-frequency component having a higher frequency than the ripple component, the current signal of the motor Even if the frequency of each component changes due to environmental changes, the ripple component is accurately detected as a difference by the differential amplifier.

  According to the seventh and eighth aspects of the invention, if the voltage signal converted by the current-voltage converter is obtained by superimposing a ripple component and a low-frequency component having a frequency lower than that of the ripple component, the current of the motor Even if the frequency of each component of the signal changes due to environmental changes, the ripple component is accurately detected as a difference by the differential amplifier.

  According to the seventh and ninth aspects of the present invention, if the voltage signal converted by the current-voltage converter is obtained by superimposing a ripple component and a high-frequency component having a higher frequency than the ripple component, the current signal of the motor Even if the frequency of each component changes due to environmental changes, the ripple component is accurately detected as a difference by the differential amplifier.

  According to the invention of claim 10, since the filter is a filter composed of a resistor and a capacitor, the configuration of the filter is simple, and the cost of the filter can be reduced.

  According to the eleventh aspect of the invention, it is possible to detect the ripple component included in the current signal of the motor with high accuracy, and to reduce the cost of the filter and the vehicle seat.

It is the block diagram which showed the motor control apparatus which concerns on embodiment to which this invention is applied. It is a timing chart showing a waveform of a motor current signal. It is a timing chart showing a waveform of a motor current signal. It is the figure which showed the waveform of the input signal and output signal of a current-voltage converter, a high pass filter, a band pass filter, a filter and a differential amplifier, an amplifier, and a waveform shaping part. It is the graph which showed the frequency characteristic of the filter. It is a circuit diagram showing a filter and a differential amplifier. It is the timing chart which showed the waveform of the input signal and output signal of a filter and a differential amplifier. It is the side view which showed the sheet | seat main body of the vehicle seat. It is the graph which showed the frequency characteristic of the filter. It is the graph which showed the frequency characteristic of the filter.

  EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated using drawing. However, the embodiments described below are given various technically preferable limitations for carrying out the present invention, but the scope of the present invention is not limited to the following embodiments and illustrated examples.

FIG. 1 is a block diagram of the motor control device 1.
The motor control device 1 includes a motor 2, a ripple extraction device 3, a computer 4, a storage unit 5, a motor driver 6, and the like.

  The motor 2 is a direct current motor. When a current flows through the motor 2, the motor 2 rotates and the motor 2 generates a periodic ripple in the current. The current signal of the motor 2 will be described with reference to FIGS. FIG. 2 is a chart showing changes in the level of current flowing through the motor 2 when the motor 2 is driven. FIG. 3 is a chart showing an enlarged scale of time and current in part A shown in FIG.

In FIG. 2, time T1 is timing when the motor 2 is started, and time T2 is timing when the motor 2 starts to operate stably. Time T3 is a timing when the movable part driven by the motor 2 comes into contact with a stopper or the like and the transmission mechanism that transmits the power of the motor 2 to the movable part starts to be restrained. Time T4 is timing when the motor 2 stops.
As shown in FIGS. 2 and 3, the current signal of the motor 2 includes a DC component, a ripple component, and one or more frequency components (AC component), and the frequency component and the ripple component are superimposed on the DC component. Of the current signal of the motor 2, the high frequency component in which the current level has changed abruptly is noise (see, for example, symbol n). Note that FIG. 3 is illustrated as having no high frequency noise component.

In a period P1 from time T1 to time T2, the ripple component r1 and a low frequency component having a frequency lower than the ripple component r1 are superimposed on the direct current component. Immediately after the start of the motor 2 in the period P1, the current level of the low frequency component is large due to the influence of the inertial force, and then the current level of the low frequency component gradually decreases with time. Immediately after the start of the motor 2, the amplitude of the ripple component r1 having a higher frequency than the low frequency component is large, and thereafter, the frequency of the ripple component r1 gradually increases with time, and the amplitude of the ripple component r1 is increased over time. It gradually decreases with the progress of.
In the period P2 from time T2 to time T3, the ripple component r2 and the low frequency component having a frequency lower than the ripple component r2 are superimposed on the DC component, the DC component is substantially constant and stable, and the frequency of the low frequency component and The amplitude is stable, and the frequency and amplitude of the ripple component r2 are stable. The reason why the frequency of the ripple component r2 is higher than the frequency of the low frequency component is that a plurality of coils built in the motor 2 have a difference in winding resistance.
In a period P3 from time T3 to time T4, the frequency of the low frequency component of the motor current signal is lowered, and the current level of the low frequency component gradually increases with time. In the period P3, the frequency of the ripple component r3 of the motor current signal gradually decreases with the passage of time, and the amplitude of the ripple component r3 gradually increases with the passage of time.

  The frequency and amplitude of the low frequency component and the ripple component of the current signal of the motor 2 are affected by various environments (for example, load on the motor 2, environmental temperature, power supply voltage of the motor 2, etc.). Therefore, when the environment changes, the frequency and amplitude of the low frequency component and the ripple component change.

  The ripple extraction device 3 extracts a ripple component from the current signal of the motor 2, pulses the ripple component, and outputs a pulse signal obtained by pulsing the ripple component to the computer 4. The ripple extraction apparatus 3 and the ripple extraction method using the ripple extraction apparatus 3 will be specifically described.

  As shown in FIG. 1, the ripple extraction device 3 includes a current-voltage converter 10, a high-pass filter 20, a band-pass filter 30, a filter 40, a differential amplifier 50, and an amplifier 60. And a waveform shaping unit 70. FIG. 4 is a diagram for explaining input signals and output signals of the current-voltage converter 10, the high-pass filter 20, the band-pass filter 30, the filter 40 and the differential amplifier 50, the amplifier 60, and the waveform shaping unit 70. In FIG. 4, the period in which the input signal and the output signal of the current-voltage converter 10, the high-pass filter 20, and the band-pass filter 30 are shown is from the time T1 to the beginning of the period P2 in FIG. A period in which the input signals and output signals of the filter 40, the differential amplifier 50, the amplifier 60, and the waveform shaping unit 70 are shown is a part of the period P2 in FIG.

  The current / voltage converter 10 inputs a current signal of the motor 2. The current-voltage converter 10 converts the input current signal of the motor 2 into a voltage signal. Specifically, the current-voltage converter 10 includes a resistor 11, the resistor 11 is connected between the ground and the motor 2, and the current signal of the motor 2 is converted into a voltage signal between the resistor 11 and the motor 2. Converted. The current-voltage converter 10 outputs the converted voltage signal to the filter 40 and the differential amplifier 50 via the high-pass filter 20 and the band-pass filter 30. The current-voltage converter 10 may be one using an operational amplifier (for example, a negative feedback current-voltage converter).

The high-pass filter 20 receives the voltage signal converted by the current-voltage converter 10 (output signal of the current-voltage converter 10). The high-pass filter 20 passes a high-frequency component of the voltage signal converted by the current-voltage converter 10 (an output signal of the current-voltage converter 10) and attenuates a low-frequency component. That is, the high pass filter 20 removes a DC component from the voltage signal converted by the current-voltage converter 10. The high pass filter 20 outputs a signal with the low frequency component attenuated to the filter 40 and the differential amplifier 50 via the band pass filter 30.
The high-pass filter 20 is one using an operational amplifier (for example, a negative feedback high-pass filter or a positive feedback high-pass filter) or one using a resistor / capacitor (for example, a CR high-pass filter).

The bandpass filter 30 inputs the voltage signal converted by the current-voltage converter 10 via the highpass filter 20. The band-pass filter 30 passes a component in a predetermined frequency band of the voltage signal (the output signal of the high-pass filter 20) converted by the current-voltage converter 10, and attenuates a component outside the predetermined frequency band. That is, the band-pass filter 30 removes high-frequency noise components from the voltage signal (output signal of the high-pass filter 20) converted by the current-voltage converter 10, and removes low-frequency components that could not be removed by the high-pass filter 20. Remove. The bandpass filter 30 outputs a signal obtained by attenuating a component outside a predetermined frequency band to the filter 40 and the differential amplifier 50.
The band pass filter 30 uses an operational amplifier (for example, a multiple negative feedback type band pass filter, a multiple positive feedback type band pass filter) or a resistor / capacitor.

  The filter 40 receives the voltage signal converted by the current-voltage converter 10 through the high-pass filter 20 and the band-pass filter 30, and filters the signal. The filter 40 outputs the filtered signal to the differential amplifier 50.

FIG. 5 is a graph showing the frequency characteristics of the filter 40.
As shown in FIG. 5, the filter 40 is a band pass filter. The filter 40 passes the component in the intermediate frequency band between the low cutoff frequency fc1 and the high cutoff frequency fc2 in the voltage signal (the output signal of the bandpass filter 30) converted by the current-voltage converter 10. . Low cut-off frequency fc1 <high cut-off frequency fc2. The cut-off frequency refers to a frequency at which the output power is 1/2 of the input power. That is, the frequency at which the gain G is −3 db is the cutoff frequency.
Further, the filter 40 attenuates a component in a low frequency range lower than the low cutoff frequency fc1 in the voltage signal (the output signal of the bandpass filter 30) converted by the current-voltage converter 10. Specifically, in the low frequency range lower than the low cut-off frequency fc1, the filter 40 has a lower component frequency included in the voltage signal (the output signal of the bandpass filter 30) converted by the current-voltage converter 10. The low frequency band component of the voltage signal (the output signal of the band pass filter 30) converted by the current-voltage converter 10 is attenuated so that the attenuation rate becomes higher.
Further, the filter 40 attenuates a component in a high frequency region exceeding the high cut-off frequency fc2 in the voltage signal (the output signal of the bandpass filter 30) converted by the current-voltage converter 10. Specifically, in a high frequency region exceeding the high cut-off frequency fc2, the filter 40 attenuates as the frequency of the component included in the voltage signal (the output signal of the bandpass filter 30) converted by the current-voltage converter 10 decreases. The high frequency component of the voltage signal (the output signal of the bandpass filter 30) converted by the current-voltage converter 10 is attenuated so that the rate becomes lower.

  As shown in FIGS. 2 and 3, the current signal of the motor 2 is obtained by superimposing a ripple component and a low frequency component having a frequency lower than that of the ripple component. The frequency of the ripple component is checked in advance by experiments, measurements, etc., and in the circuit design of the filter 40, the high cutoff frequency fc2 of the filter 40 is set to the frequency of the ripple component (for example, the frequency of the ripple component due to temperature change). , The frequency at room temperature). Therefore, the filter 40 has a ripple component in the voltage signal (the output signal of the band pass filter 30) converted by the current-voltage converter 10 that is lower in frequency than the low frequency component (the frequency of the low frequency component is lower than that of the ripple component). Attenuate with high attenuation factor. That is, the filter 40 removes the ripple component more efficiently than the low frequency component. Therefore, the filter 40 outputs a signal from which the ripple component has been removed to the differential amplifier 50.

  The differential amplifier 50 inputs the voltage signal converted by the current-voltage converter 10 via the high-pass filter 20 and the band-pass filter 30 and also receives the output signal of the filter 40. The differential amplifier 50 takes the difference between the input output signal of the filter 40 and the voltage signal converted by the current-voltage converter 10 (the output signal of the bandpass filter 30), and amplifies the difference. The differential amplifier 50 outputs a differential signal representing the difference to the amplifier 60.

  FIG. 6 is a circuit diagram illustrating an example of the filter 40 and the differential amplifier 50. FIG. 7A is a timing chart showing the waveform of the voltage signal in the A section shown in FIG. 6, and FIG. 7B is a timing showing the waveform of the voltage signal in the B section shown in FIG. FIG. 7C is a timing chart showing the waveform of the voltage signal in the portion C shown in FIG.

  As shown in FIG. 6, the filter 40 includes a high pass filter 41, a low pass filter 42, and a high pass filter 43. The output of the band pass filter 30 is connected to the input of the high pass filter 41, the output of the high pass filter 41 is connected to the input of the low pass filter 42, and the output of the low pass filter 42 is connected to the output of the high pass filter 43.

The high pass filter 41 is a secondary CR high pass filter. That is, the high pass filter 41 includes a capacitor 41a, a resistor 41b, a capacitor 41c, and a resistor 41d. Note that the high-pass filter 41 may be a primary CR high-pass filter including one capacitor and a resistor. Further, the high-pass filter 41 may be a third-order or higher CR high-pass filter.
The low pass filter 42 is a secondary RC low pass filter. That is, the low-pass filter 42 includes a resistor 42a, a capacitor 42b, a resistor 42c, and a capacitor 42d. The low-pass filter 42 may be a primary RC low-pass filter including one resistor and a capacitor. Further, the low-pass filter 42 may be a third-order or higher RC low-pass filter.
The high pass filter 43 includes a capacitor 43a.

  The differential amplifier 50 includes resistors 51 and 52, an operational amplifier 53, a coupling capacitor 54, a bias circuit 55, and the like. The output terminal of the operational amplifier 53 is connected to the inverting input terminal of the operational amplifier 53 via the resistor 52, and negative feedback is applied to the operational amplifier 53. The output signal of the filter 40 (the output signal of the high pass filter 43) is input to the inverting input terminal of the operational amplifier 53 via the resistor 51, and the output signal of the band pass filter 30 is supplied to the operational amplifier via the coupling capacitor 54 and the bias circuit 55. 53 is input to the non-inverting input terminal. The coupling capacitor 54 removes a direct current component of the output signal of the band pass filter 30. The bias circuit 55 includes resistors 56 and 57 connected in series between the power supply voltage and the ground. The bias circuit 55 applies a bias voltage to the output signal of the bandpass filter 30 from which the DC component has been removed by the coupling capacitor 54, and raises the reference level of the output signal of the bandpass filter 30. Note that the coupling capacitor 54 and the bias circuit 55 may be omitted.

  The differential signal output by the differential amplifier 50 is a ripple component of the voltage signal converted by the current-voltage converter 10. Because the difference signal output by the differential amplifier 50 represents the difference between the output signal of the bandpass filter 30 and the output signal of the filter 40, the frequency of each component of the current signal of the motor 2 changes due to environmental changes. In addition, ripples included in the current signal of the motor 2 can be detected with high accuracy.

  As shown in FIGS. 1 and 6, the amplifier 60 receives the differential signal (the output signal of the operational amplifier 53) output by the differential amplifier 50. The amplifier 60 amplifies the differential signal output by the differential amplifier 50 and outputs it to the waveform shaping unit 70. The amplifier 60 is, for example, a negative feedback amplifier.

  The waveform shaping unit 70 inputs the differential signal (the output signal of the operational amplifier 53) output from the differential amplifier 50 via the amplifier 60. The waveform shaping unit 70 shapes the waveform of the differential signal (the output signal of the amplifier 60) output by the differential amplifier 50 into a rectangular wave. Specifically, the waveform shaping unit 70 has a comparator, and the comparator compares the differential signal (the output signal of the amplifier 60) output by the differential amplifier 50 with a reference voltage, thereby allowing the differential amplifier 50 to The output differential signal (the output signal of the amplifier 60) is converted into a pulse signal. The waveform shaping unit 70 outputs a pulse signal shaped into a rectangular wave to the computer 4.

  The computer 4 includes a CPU, a RAM, a ROM, and the like. In the ROM, a program readable by the computer 4 is stored. The RAM provides a work area for the computer 4. The computer 4 reads a program stored in the ROM, performs processing according to the program, and implements various functions by the program. For example, the computer 4 functions as the following means by a program.

  The computer 4 functions as an activation unit that issues a command related to the rotation direction and an activation command to the motor driver 6. The computer 4 functions as input means for inputting the output signal of the waveform shaping unit 70. The computer 4 functions as a counter that counts the number of pulses of the output signal of the waveform shaping unit 70. The computer 4 functions as speed calculation means for calculating the rotation speed (the number of rotations per unit time) of the motor 2 by measuring the time between pulses of the output signal of the waveform shaping unit 70. The computer 4 functions as a rotation amount calculation means for calculating the rotation amount of the motor 2 (corresponding to the movement amount and position of the movable part driven by the motor 2) based on the number of pulses counted by the counter. The computer 4 functions as speed setting means that calculates a set speed based on the counted number of pulses, the calculated rotation speed, or the calculated rotation amount, and issues a command for the set speed to the motor driver 6. The computer 4 functions as a stop unit that determines a stop timing based on the counted number of pulses, a calculated rotation speed, a calculated rotation amount, or the like, and issues a stop command to the motor driver 6 at the stop timing. The computer 4 functions as a recording unit that temporarily stores the counted number of pulses, the calculated rotation speed, the calculated rotation amount, the set speed, the stop timing, and the like in the RAM or the storage unit 5.

  The storage unit 5 is a readable / writable storage medium such as a nonvolatile memory or a hard disk.

  The motor driver 6 drives the motor 2 in accordance with a command from the computer 4. That is, when the motor driver 6 receives the start command and the rotation direction command from the computer 4, the motor driver 6 starts the motor 2 in the rotation direction. The motor driver 6 drives the motor 2 at the set speed according to the set speed command received from the computer 4. When the motor driver 6 receives a stop command from the computer 4, the motor driver 6 stops the motor 2.

  The motor control device 1 shown in FIG. 1 is used for a vehicle seat. The vehicle seat includes the motor control device 1 shown in FIG. 1 and the seat body 90 shown in FIG. 7, and the movable part of the seat body 90 is driven by the motor 2. The number of movable parts of the seat body 90 and the number of motors 2 are preferably the same. When there are a plurality of motors 2, a motor driver 6 and a ripple extracting device 3 are provided for each motor 2, and a computer 4 and the storage unit 5 are common to all the motors 2.

  The sheet body 90 will be specifically described. The seat body 90 includes a rail 91, a seat bottom 92, a backrest 93, a headrest 94, an armrest 95, a legrest 96, and the like.

  The seat bottom 92 is mounted on the rail 91, the seat bottom 92 is provided so as to be movable in the front-rear direction by the rail 91, and the motor 2 drives the seat bottom 92 in the front-rear direction. The front part of the seat bottom 92 is provided to be movable up and down, and another motor 2 drives the front part of the seat bottom 92 in the vertical direction. The rear part of the seat bottom 92 is provided so as to be movable up and down, and another motor 2 drives the rear part of the seat bottom 92 in the vertical direction. The backrest 93 is rotatably connected to the rear end portion of the seat bottom 92 by a reclining mechanism, and another motor 2 raises and lowers the backrest 93 with respect to the seat bottom 92. The headrest 94 is connected to the upper end of the backrest 93 so as to be able to move up and down and rotate, and another motor 2 drives the headrest 94 in the vertical direction, and another motor 2 undulates the headrest 94 back and forth. The armrest 95 is rotatably connected to the side surface of the backrest 93, and another motor 2 drives the armrest 95 from the horizontal state to the vertical state and vice versa. A legrest 96 is rotatably connected to the front end portion of the seat bottom 92, and another motor 2 drives the legrest 96 from a flipped state to a suspended state or vice versa.

The ripple extraction device 3, the motor control device 1, and the vehicle seat as described above produce the following effects.
(1) Since the high cut-off frequency fc2 of the filter 40 is set lower than the frequency of the ripple component in the circuit design of the filter 40, the ripple component can be removed by the filter 40.
(2) The differential amplifier 50 outputs the output signal of the bandpass filter 30 (the voltage signal converted by the current-voltage converter 10 from which the DC component and the high-frequency noise component are removed) and the output signal of the filter 40 The difference between the voltage signals converted by the current-voltage converter 10 from which the DC component, the high-frequency noise component, the ripple component, etc. are removed is taken and output as a difference signal. Therefore, the output signal of the differential amplifier 50 is a ripple component in the voltage signal converted by the current-voltage converter 10. Because the output signal of the differential amplifier 50 is a differential signal, even if the frequency of each component of the current signal of the motor 2 fluctuates due to environmental changes, the ripple component is accurately extracted, Ripple can be detected with high accuracy.
(3) Of the frequency characteristics shown in FIG. 5, the output of the differential amplifier 50 can be obtained even if the frequency of the ripple component fluctuates due to temperature change because the sloped portion in the region higher than the high cutoff frequency fc2 is used. The signal is accurately extracted as a ripple component.
(4) Since the ripple component is extracted by the filter 40 and the differential amplifier 50 using the frequency characteristics of the filter 40, it is not necessary to use a variable cutoff frequency filter for the filter 40. Therefore, the cost of the filter 40 can be reduced.
(5) Since the ripple extraction device 3 is not a closed loop circuit such as a feedback control circuit, it is possible to accurately detect ripples even if the frequency of each component of the current signal of the motor 2 changes transiently or rapidly. it can.
(6) Since the filter 40 is a filter including resistors 41b, 41d, 41a, and 41c and capacitors 41a, 41c, 41b, 41d, and 43a, the configuration of the filter 40 is simple, and an increase in the cost of the filter 40 is suppressed. Can do.
(7) Since the ripple component is extracted by the filter 40 and the differential amplifier 50 using the frequency characteristics of the filter 40, it is not necessary to use a variable cutoff frequency filter for the high-pass filter 20 or the band-pass filter 30. Therefore, the cost increase of the high pass filter 20 and the band pass filter 30 can be suppressed.
(8) Since the DC component of the voltage signal converted by the current-voltage converter 10 is removed by the high-pass filter 20, the processing of the band-pass filter 30, the filter 40, and the differential amplifier 50 following the high-pass filter 20 is performed. Exactly done.
(9) Since the component outside the predetermined frequency band of the voltage signal converted by the current-voltage converter 10 is attenuated by the band-pass filter 30, the processing of the filter 40 and the differential amplifier 50 subsequent to the band-pass filter 30 is performed. Exactly done.

[Modification]
The embodiments to which the present invention can be applied are not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit of the present invention. Hereinafter, modified examples will be described. The following modifications may be combined as much as possible.

[Modification 1]
In the circuit design of the filter 40, the low cut-off frequency fc1 of the filter 40 shown in FIG. 5 is set to be higher than the frequency of the ripple component (for example, the frequency at normal temperature) while taking into account fluctuations in the frequency of the ripple component due to temperature changes. Has been. Therefore, the filter 40 attenuates the ripple component of the voltage signal (the output signal of the bandpass filter 30) converted by the current-voltage converter 10 higher than the high-frequency component (the high-frequency component has a higher frequency than the ripple component). Decay at a rate. That is, the filter 40 removes the ripple component more efficiently than the high frequency component. Therefore, the filter 40 outputs a signal from which the ripple component has been removed to the differential amplifier 50.

  In this case, the current signal of the motor 2 and the input signals of the filter 40 and the differential amplifier 50 are obtained by superimposing a ripple component and a high frequency component having a higher frequency than the ripple component.

[Modification 2]
The filter 40 may be a low-pass filter having a frequency characteristic as shown in FIG. 9 instead of the band-pass filter. The filter 40 passes the component below the cutoff frequency fc3 among the voltage signal (the output signal of the bandpass filter 30) converted by the current-voltage converter 10, and attenuates the component exceeding the cutoff frequency fc3. Specifically, in a high frequency region exceeding the cut-off frequency fc3, the filter 40 decreases the attenuation rate as the frequency of the component included in the voltage signal (the output signal of the bandpass filter 30) converted by the current-voltage converter 10 decreases. Is attenuated so that the voltage signal converted by the current-voltage converter 10 (the output signal of the bandpass filter 30) is attenuated.

  In the circuit design of the filter 40, the cut-off frequency fc3 of the filter 40 shown in FIG. 9 is set to be lower than the frequency of the ripple component (for example, the frequency at normal temperature) while taking into account the fluctuation of the ripple component frequency due to temperature change. ing. Therefore, the filter 40 has a ripple component in the voltage signal (the output signal of the band pass filter 30) converted by the current-voltage converter 10 that is lower in frequency than the low frequency component (the frequency of the low frequency component is lower than that of the ripple component). Attenuate with high attenuation factor. That is, the filter 40 removes the ripple component more efficiently than the low frequency component. Therefore, the filter 40 outputs a signal from which the ripple component has been removed to the differential amplifier 50.

  In this case, the current signal of the motor 2 and the input signal of the filter 40 and the differential amplifier 50 are obtained by superimposing a ripple component and a low frequency component having a frequency lower than that of the ripple component.

  When the filter 40 is a low-pass filter, the high-pass filters 41 and 43 shown in FIG. 6 are omitted, the output of the band-pass filter 30 is connected to the input of the low-pass filter 42, and the output of the low-pass filter 42 is connected via the resistor 51. The inverting input terminal of the operational amplifier 53 is connected.

[Modification 3]
The filter 40 may be a high-pass filter having a frequency characteristic as shown in FIG. 10 instead of the band-pass filter. The filter 40 passes a component having a cutoff frequency fc4 or higher in the voltage signal (the output signal of the bandpass filter 30) converted by the current-voltage converter 10, and attenuates a component lower than the cutoff frequency fc4. Specifically, in the low frequency region below the cut-off frequency fc4, the filter 40 attenuates as the frequency of the component included in the voltage signal (the output signal of the bandpass filter 30) converted by the current-voltage converter 10 decreases. The voltage signal (the output signal of the bandpass filter 30) converted by the current-voltage converter 10 is attenuated so that the rate becomes higher.

  In the circuit design of the filter 40, the cut-off frequency fc4 of the filter 40 shown in FIG. 10 is set to be higher than the frequency of the ripple component (for example, the frequency at normal temperature) while taking into account fluctuations in the ripple component frequency due to temperature changes. ing. Therefore, the filter 40 attenuates the ripple component of the voltage signal (the output signal of the bandpass filter 30) converted by the current-voltage converter 10 higher than the high-frequency component (the high-frequency component has a higher frequency than the ripple component). Decay at a rate. That is, the filter 40 removes the ripple component more efficiently than the high frequency component. Therefore, the filter 40 outputs a signal from which the ripple component has been removed to the differential amplifier 50.

  When the filter 40 is a high pass filter, the low pass filter 42 shown in FIG. 6 is omitted, and the output of the band pass filter 30 is connected to the input of the high pass filter 41.

[Modification 4]
The filter 40 may be a band stop filter instead of a band pass filter.

[Modification 5]
One or both of the high pass filter 20 and the band pass filter 30 may be omitted. When the high-pass filter 20 is omitted, the output of the current-voltage converter 10 is connected to the input of the band-pass filter 30. When the band pass filter 30 is omitted, the output of the high pass filter 20 is connected to the input of the filter 40 and the input of the differential amplifier 50. When both the high-pass filter 20 and the band-pass filter 30 are omitted, the output of the current-voltage converter 10 is connected to the input of the filter 40 and the input of the differential amplifier 50.

[Modification 6]
The motor control device 1 is incorporated in an electric door mirror device, and a movable part of the electric door mirror device (for example, a storage mechanism that stores and unfolds the mirror housing with respect to the door, a tilt mechanism that swings the mirror up and down with respect to the mirror housing, a mirror) A pan mechanism that swings the mirror to the left and right with respect to the housing may be driven by the motor 2 of the motor control device 1. The motor control device 1 may be incorporated in the power window device, and the movable portion (for example, window regulator) of the power window device may be driven by the motor 2.

[Modification 7]
The filter 40 may use an operational amplifier (for example, a negative feedback low-pass filter, a positive feedback low-pass filter, a multiple negative feedback band-pass filter, or a multiple positive feedback band-pass filter).

[Modification 8]
In the above-described embodiment, since the waveform shaping unit 70 converts the differential signal output by the differential amplifier 50 into a pulse signal, the waveform shaping unit 70 is a 1-bit AD converter. On the other hand, the resolution of the waveform shaping unit 70 may be 2 bits or more, and the waveform shaping unit 70 may convert the differential signal output by the differential amplifier 50 into a digital signal.

DESCRIPTION OF SYMBOLS 2 Motor 3 Ripple extraction apparatus 4 Computer 10 Current-voltage converter 20 High pass filter 30 Band pass filter 40 Filter 50 Differential amplifier 60 Amplifier 70 Waveform shaping part 90 Sheet | seat main body

Claims (12)

A ripple extraction device for extracting a ripple component contained in a motor current signal,
A current-voltage converter that converts a current signal of the motor into a voltage signal;
A filter for filtering the voltage signal converted by the current-voltage converter;
A ripple extraction device comprising: a differential amplifier that takes a difference between a voltage signal converted by the current-voltage converter and an output signal of the filter.   The ripple extraction device according to claim 1, wherein the filter attenuates a ripple component in the voltage signal converted by the current-voltage converter.   The filter is a low-pass filter that attenuates the voltage signal converted by the current-voltage converter such that the lower the frequency of the component included in the voltage signal converted by the current-voltage converter, the lower the attenuation factor. The ripple extraction device according to claim 1 or 2, wherein   The ripple extraction device according to claim 3, wherein a cutoff frequency of the filter is set lower than a frequency of the ripple component.   The filter is a high-pass filter that attenuates the voltage signal converted by the current-voltage converter so that the lower the frequency of the component included in the voltage signal converted by the current-voltage converter, the higher the attenuation rate. The ripple extraction device according to claim 1 or 2, wherein   The ripple extraction device according to claim 5, wherein a cutoff frequency of the filter is set to be higher than a frequency of the ripple component.   The filter is converted by the current-voltage converter so that the lower the frequency of the component included in the voltage signal converted by the current-voltage converter in the low frequency range below the low cutoff frequency, the higher the attenuation factor. The lower the frequency of the component included in the voltage signal converted by the current-voltage converter in the high frequency range exceeding the high cutoff frequency higher than the low cutoff frequency, the lower the attenuation factor. The voltage signal converted by the current-voltage converter is attenuated so that the voltage signal converted by the current-voltage converter is passed in a frequency band between the low cutoff frequency and the high cutoff frequency. The ripple extraction device according to claim 1, wherein the ripple extraction device is a band-pass filter.   The ripple extraction device according to claim 7, wherein the low cutoff frequency of the filter is set to be higher than a frequency of the ripple component.   The ripple extraction device according to claim 7, wherein the high cutoff frequency of the filter is set lower than the frequency of the ripple component.   The ripple extraction device according to any one of claims 1 to 9, wherein the filter is a filter including one or a plurality of resistors and a capacitor. A seat body having a movable part;
The ripple extraction device according to any one of claims 1 to 10,
The motor,
A vehicle seat in which the movable part is driven by the motor. A ripple extraction method for extracting ripples included in a motor current signal,
Converting the current signal of the motor into a voltage signal;
Filtering the converted voltage signal;
A ripple extraction method for taking a difference between the converted voltage signal and the filtered voltage signal.

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