JP2007220020A - Self-propelled cleaner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a self-propelled cleaner which receives ultrasonic wave or electromagnetic wave, which is originated from a VW device positioned in the rear part of a progress direction, without increasing the number of reception sensors, and does not invade a cleaning prohibition area. <P>SOLUTION: When one of obstacle sensors 17a-17c does not receive the ultrasonic wave 6a, a control part 16 allows a driver 15 to rotate an apparatus body 1 by 90° (s6). Then the state of the apparatus body 1 is changed from (A) in a figure 6 into (B) in the figure 6. The control part 16 determines whether one of the obstacle sensors 17a-17c receives the ultrasonic wave or not (s7). When one of the sensors 17a-17c receives the ultrasonic wave 6a, the control part 16 determines the existence of a virtual wall so as to allow the driver 15 to rotate the apparatus body 1 by 180° (s8). Accordingly, the state of the apparatus body 1 is changed from (B) in the figure 6 into (C) in the figure 6, so that the apparatus body 1 goes straight and travels in the direction (a) of a cleaning area without invading the cleaning prohibition area. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a self-propelled cleaner that autonomously travels an apparatus main body and sucks and cleans dust falling on a floor or the like.

  2. Description of the Related Art In recent years, self-propelled cleaners having an autonomous running function for autonomously running the apparatus main body and an automatic cleaning function for sucking and cleaning garbage falling on a floor or the like have been developed.

  FIG. 7 is an explanatory view showing a configuration of a main part of a conventional self-propelled cleaner, a cleaning prohibited area, and a cleaning area. Self-propelled cleaner 100 has a nozzle (not shown) for sucking dust on the floor, a brush 13 for splashing dust on the floor, and a dust collection chamber for storing the sucked dust (automatic cleaning function). (Not shown) and a suction unit (not shown) having a suction fan and a suction fan motor for introducing dust into the dust collection chamber. The self-propelled cleaner 100 includes a driving wheel 12, autonomous traveling means (not shown) having a motor for driving the driving wheel 12, and a reception sensor 18 as autonomous traveling functions.

The reception sensor 18 is disposed only in front of the apparatus main body 100 in the traveling direction, and receives the ultrasonic wave 6a or the electromagnetic wave 6a transmitted from the transmission unit 6 of the virtual wall (hereinafter, VW) apparatus 2.
In FIG. 7, three reception sensors 18 are arranged, but there may be other numbers. The other number is, for example, two on both sides of the front of the apparatus main body 100 in the traveling direction. Further, although the receiving sensor is used, an obstacle sensor may be used. The obstacle sensor has a transmission function for transmitting ultrasonic waves and a reception function for receiving ultrasonic waves reflected from the obstacles. The reception function of the obstacle sensor is the same as that of the reception sensor.

  The VW device 2 is an ultrasonic transmitter or an electromagnetic wave transmitter, and creates a virtual wall 6a by transmitting the ultrasonic wave 6a or the electromagnetic wave 6a. For example, the user can set in advance a cleaning prohibition area on the upper left side with the wall 3 and the virtual wall 6a and a cleaning area on the lower right side with the wall 3 and the virtual wall 6a (FIG. 7). And see FIG. 8 described later).

  And the self-propelled cleaner 100 cleans the floor by controlling the suction part while autonomously running in the cleaning area by a certain distance unit. Moreover, the self-propelled cleaner 100 determines whether or not the reception sensor 18 receives ultrasonic waves or electromagnetic waves every time the vehicle travels the predetermined distance. The constant distance is a predetermined distance, for example, 50 cm.

  FIG. 8 is an explanatory view showing a state in which the self-propelled cleaner enters the cleaning prohibited area when the self-propelled cleaner is caused to travel by the conventional control method. If it is determined that the reception sensor 18 is receiving the ultrasonic wave 6a or the electromagnetic wave 6a, the apparatus main body 100 rotates and travels in the direction of FIG.

On the other hand, a self-propelled cleaner as described in Patent Document 1 has been proposed. This self-propelled cleaner has three driving wheels for self-propelling the apparatus main body, three reception sensors arranged at the front and rear of the apparatus main body, detecting obstacles, and a traveling control means for controlling the driving wheels. Is provided.
The travel control means advances the apparatus main body straight forward until the reception sensor detects a front obstacle. Then, the traveling control means once stops when it detects an obstacle ahead, and then changes the direction by a predetermined angle and moves backward by a predetermined distance. Further, the travel control means once stops when the vehicle travels backward by a predetermined distance, and then changes the direction by a predetermined angle and advances the apparatus main body straight forward until the reception sensor again detects an obstacle ahead. Thereafter, the traveling control means repeats this operation.
JP 2002-321179 A

  However, since the receiving sensor 18 is disposed only in front of the apparatus main body 100 in the traveling direction, the receiving sensor 18 cannot receive the ultrasonic wave 6a or the electromagnetic wave 6a transmitted from the VW device 2 located behind the traveling direction (see FIG. 8).

Therefore, the conventional self-propelled cleaner 100 may travel in the direction of FIG. 8B without noticing the virtual wall 6a. In other words, the cleaning-prohibited area may be entered. In particular, when the driving mode is random driving, the cleaning-prohibited area is often entered.
Therefore, the conventional self-propelled cleaner 100 has a problem of cleaning a cleaning prohibited area that the user does not want to be cleaned. Specifically, important paper or the like placed in the cleaning prohibited area may be sucked.

  Moreover, in patent document 1, although three receiving sensors are arrange | positioned also in the advancing direction back of an apparatus main body, compared with the self-propelled cleaner 100, the manufacturing cost of a self-propelled cleaner will become high. There was a problem.

  The present invention is intended to solve such a conventional problem, and enables the reception of ultrasonic waves or electromagnetic waves transmitted from a VW device located rearward in the traveling direction without increasing the number of receiving sensors, and prohibits cleaning. An object of the present invention is to provide a self-propelled cleaner that does not enter an area.

  The self-propelled cleaner of the present invention has the following configuration in order to solve the above problems.

(1) a receiving sensor that receives ultrasonic waves or electromagnetic waves transmitted from an ultrasonic transmitter or electromagnetic wave transmitter;
In a self-propelled cleaner provided with autonomous traveling means that rotates a driving wheel to autonomously travel the apparatus main body, and the reception sensor receives the ultrasonic waves or the electromagnetic waves, the apparatus main body rotates to travel.
The reception sensor is disposed only in the forward direction of the apparatus main body,
The autonomous traveling means autonomously travels the device main body in a certain distance unit, and determines whether the reception sensor receives the ultrasonic wave or the electromagnetic wave every time the device main body travels the certain distance. And
When the autonomous traveling means determines that the reception sensor does not receive the ultrasonic wave or the electromagnetic wave, the autonomous traveling unit rotates the apparatus main body sideways in the traveling direction or backward in the traveling direction, and the reception sensor detects the ultrasonic wave or the electromagnetic wave. Is determined again.

In this configuration, the electromagnetic wave is a concept including light and radio waves. An ultrasonic transmitter or an electromagnetic wave transmitter is a virtual wall device. Further, the fixed distance is a predetermined distance, for example, 50 cm.
In this configuration, it is assumed that the ultrasonic transmitter or electromagnetic wave transmitter creates a virtual wall by transmitting the ultrasonic wave or electromagnetic wave. Specifically, the user presets a cleaning prohibited area and a cleaning area across a virtual wall.
Under such circumstances, the self-propelled cleaner is traveling autonomously by a certain distance unit.
When the autonomous traveling means determines that the reception sensor does not receive the ultrasonic wave or the electromagnetic wave, the autonomous traveling means rotates the apparatus main body laterally or backward in the traveling direction, and the reception sensor detects the ultrasonic wave or the electromagnetic wave. Is determined again. The purpose of this is to be able to receive ultrasonic waves or electromagnetic waves regardless of the direction from which the ultrasonic waves or electromagnetic waves are transmitted to the main body of the apparatus, and to prevent the self-propelled cleaner from noticing the virtual wall. It is.
When the autonomous traveling means determines again that the reception sensor does not receive the ultrasonic wave or the electromagnetic wave, the autonomous traveling means travels assuming that there is no virtual wall. Here, it is assumed that there is no virtual wall as a result of searching for a sufficiently virtual wall.
On the other hand, if the said autonomous traveling means judges that the said reception sensor is receiving the said ultrasonic wave or the said electromagnetic wave, it will consider that there exists a virtual wall and will rotate this apparatus main body, and will drive | work.
As described above, there is an effect that it is possible to prevent the self-propelled cleaner from entering the cleaning prohibited area without increasing the number of reception sensors. In addition, since it is not necessary to increase the number of reception sensors, the manufacturing cost of the self-propelled cleaner can be reduced.

(2) The two reception sensors are arranged only on both sides of the front of the apparatus main body in the traveling direction,
When the autonomous traveling unit determines that the reception sensor is not receiving the ultrasonic wave or the electromagnetic wave, the autonomous traveling unit rotates the apparatus main body at any angle from 70 degrees to 110 degrees.

(3) One of the reception sensors is arranged at the center part in the forward direction of the apparatus main body and two at both side parts,
When the autonomous traveling unit determines that the reception sensor is not receiving the ultrasonic wave or the electromagnetic wave, the autonomous traveling unit rotates the apparatus main body at any angle from 70 degrees to 110 degrees.

  According to the present invention, it is possible to prevent the self-propelled cleaner from entering the cleaning prohibited area without increasing the number of reception sensors. In addition, since it is not necessary to increase the number of reception sensors, the manufacturing cost of the self-propelled cleaner can be reduced.

  Hereinafter, the self-propelled cleaner which is an embodiment of the present invention is explained.

FIG. 1 is a block diagram showing a configuration of a main part of a self-propelled cleaner that is an embodiment of the present invention. The self-propelled cleaner 1 has, as an automatic cleaning function, a nozzle (not shown) for sucking dust on the floor, brushes 13a to 13c for splashing dust on the floor, and dust collection for storing the sucked dust. And a suction section 30 (see FIG. 2 described later) having a suction fan and a suction fan motor for introducing dust into the dust collection chamber.
The brushes 13a to 13c are located at the rear part of the apparatus main body 1 and are rotatable.

Moreover, the self-propelled cleaner 1 has a pair of drive wheels 12a and 12b on both sides of the apparatus main body 1, drive motors 11a and 11b corresponding to the drive wheels 12a and 12b, and a drive motor 11a as an autonomous running function. And 11b, respectively, and motor drivers 15a and 15b, respectively, and an obstacle sensor 17 that detects an obstacle.
In this embodiment, the driven wheel is omitted for the sake of simplicity. The driven wheels are each composed of a pair of wheels arranged to face each other at an appropriate interval in order to ensure stability during travel of the apparatus main body 1.

  The motor drivers 15a and 15b control the operation of the drive motors 11a and 11b based on the control signal given from the control unit 16, respectively.

  In addition, distance sensors 14a and 14b that measure the travel distance of the self-propelled cleaner 1 and output distance data are provided on the rotation shafts of the drive motors 11a and 11b.

  The obstacle sensor 17 is provided in front of the apparatus main body 1 in the traveling direction. The obstacle sensor 17 is provided on the front side of the apparatus main body 1, and is provided on the left and right sides of the apparatus main body 1 to detect an obstacle in front of the apparatus main body 1. It is divided into sensors 17a and 17c.

  The obstacle sensor 17 has a transmission function for transmitting ultrasonic waves and a reception function for receiving ultrasonic waves. The obstacle is detected by transmitting an ultrasonic wave from the obstacle sensor 17 and receiving the ultrasonic wave reflected from the obstacle. Further, detection of a virtual wall 6a described later is performed by receiving an ultrasonic wave 6a transmitted from a virtual wall device 2 described later.

  In addition, although the three obstacle sensors 17a-17c are provided, this is in order to detect a front obstacle more reliably, Comprising: One or two may be sufficient. In the case of two, it is preferable to arrange the device main body 100 on both sides in front of the traveling direction. In this embodiment, ultrasonic waves are used to detect obstacles, but electromagnetic waves may be used. The frequency of the ultrasonic wave is a predetermined frequency that is determined in advance.

  Signals output from the distance sensors 14 a and 14 b and the obstacle sensors 17 a to 17 c are transmitted to the control unit 16.

Further, an operation panel 22 described later is provided on the upper part of the self-propelled cleaner 1 and is provided with a switch for setting the length of the cleaning area in the vertical and horizontal directions, a switch for starting or stopping the driving, and the like. The operation panel 22 is connected to the control unit 16.
The self-propelled cleaner 1 also includes a battery (not shown) that supplies power to each part of the apparatus main body 1.

  FIG. 2 is a block diagram showing a control unit of the self-propelled cleaner and an arrangement of its peripheral part according to the embodiment of the present invention. As shown in FIG. 2, the control unit 16 includes interfaces 19 a and 19 b, a main controller 20, and a counter 24.

  The interface 19 a performs processing such as amplification and level shift on the detection signals output from the obstacle sensors 17 a to 17 c and outputs the detection signals to the main controller 20.

  The distance sensors 14a and 14b attached to the rotation shafts of the right drive motor 11a and the left drive motor 11b detect the number of rotations per unit time and give the detected result to the counter 24 in the control unit 16. The counter 24 counts the number of rotations to calculate the travel distance, and gives the result to the main controller 20.

  The operation panel 22 includes a switch for setting the length of the cleaning area in the vertical and horizontal directions, a switch for selecting a travel mode, a switch for starting or stopping cleaning, and the like. 22 is connected to the main controller 20 of the control unit 16. The traveling mode is, for example, random traveling or traveling along a wall. Random running is a mode in which the room is cleaned while running randomly.

  The main controller 20 has a ROM (not shown) for storing a control program, and a RAM (not shown) as a work field for processing the control program and each information. The traveling mode is a mode related to the control program.

  The main controller 20 is given information regarding the dimensions of the cleaning area, the running mode, the start of cleaning, and the like input to the operation panel 22. Furthermore, the main controller 20 controls driving of the right drive motor 11a and the left drive motor 11b based on the presence or absence of a front obstacle detected by the obstacle sensors 17a to 17c and the travel distance calculated by the counter 24. A control signal is output to the interface 19b.

The interface 19b performs processing such as amplification on the control signal and outputs it to the drivers 15a and 15b.
The drivers 15a and 15b control the right drive motor 11a and the left drive motor 11b, respectively, based on the control signal.

  The rotation control of the motor 11 that rotates the drive wheels 12 performed by the main controller 20 is PWM control. The main controller 20 individually controls the rotational speeds of the two drive wheels 12 and controls the traveling direction of the apparatus body 1. The main controller 20 performs rotation control of the motor 11 according to the above-described traveling mode.

FIG. 3 is an explanatory diagram showing a configuration of a main part of the self-propelled cleaner, which is an embodiment of the present invention, a cleaning prohibited area, and a cleaning area. The obstacle sensor 17 receives the ultrasonic wave 6 a transmitted from the transmission unit 6 of the virtual wall (hereinafter referred to as VW) device 2.
The VW device 2 is an ultrasonic transmitter, and creates a virtual wall 6a by transmitting the ultrasonic wave 6a. It is assumed that the user presets a cleaning prohibition area on the upper left side with the wall 3 and the virtual wall 6a and a cleaning area on the lower right side with the wall 3 and the virtual wall 6a.
In this embodiment, ultrasonic waves are used to create a virtual wall, but electromagnetic waves may be used.

  And the self-propelled cleaner 1 cleans the floor surface by controlling the suction unit 30 while autonomously running in the cleaning area in a fixed distance unit. The certain distance is a predetermined distance. The self-propelled cleaner 1 determines whether or not the obstacle sensor 17 receives an ultrasonic wave every time the vehicle travels the predetermined distance. Hereinafter, in order to simplify the description, the fixed distance is 50 cm.

  Here, the obstacle sensor 17 corresponds to the “reception sensor” of the present invention. The VW device 2 corresponds to the “ultrasonic transmitter” of the present invention. The control unit 16, the driver 15, the drive motor 11, and the distance sensor 14 correspond to the “autonomous traveling means” of the present invention.

FIG. 4 is a flowchart performed by the control unit of the self-propelled cleaner according to the embodiment of the present invention. This operation is performed when a cleaning start instruction is given on the operation panel 22. The cleaning start instruction is, for example, that a switch for starting cleaning is pressed on the operation panel 22. It is assumed that the self-propelled cleaner 1 is set to random travel.
In FIG. 4, the detection of the obstacle is omitted in order to simply explain the detection of the virtual wall 6 a.

  When there is a cleaning start instruction, the control unit 16 drives the suction fan motor to the suction unit 30 (s1). Thereby, a suction fan rotates and self-propelled cleaner 1 starts automatic cleaning.

  Next, the control unit 16 instructs the motor driver 15 to drive the drive motor 11 so that the apparatus main body 1 travels straight forward (s2). Thereby, the driving wheel 12 rotates and the self-propelled cleaner 1 starts autonomous traveling.

  The control unit 16 determines whether or not the apparatus main body 1 has traveled 50 cm (s3). This determination is made by referring to the counter 24 of the control unit 16.

After waiting for 50 cm, the control unit 16 instructs the motor driver 15 to stop the drive motor 11 and stop the apparatus main body 1 (s4).
Here, it is assumed that the apparatus main body 1 is stopped in the vicinity of the virtual wall 6a due to the stop of the traveling of s4 (see FIG. 3).

  And the control part 16 judges whether any of the obstacle sensors 17a-17c is receiving the ultrasonic wave (s5).

  When it is determined that the ultrasonic wave is received, that is, when any of the obstacle sensors 17a to 17c receives the ultrasonic wave 6a, the control unit 16 rotates the apparatus main body 1 by 180 degrees by the driver 15 (s8), and s2 Proceed to and continue processing. That is, the apparatus main body 1 rotates in the traveling direction (c) and travels straight (see FIG. 3).

  In s5 determination affirmation, the case where the virtual wall 6a was able to be detected by the relationship of the stop position of the apparatus main body 1 is assumed.

On the other hand, in s5 determination negative, the case where the apparatus main body 1 stops in the position as shown in FIG. 5 is assumed.
FIG. 5 is an explanatory view showing a state when the self-propelled cleaner according to the embodiment of the present invention stops at a virtual wall. FIG. 6 is an explanatory diagram showing a flow from when the self-propelled cleaner according to the embodiment of the present invention stops traveling until a virtual wall is detected and rotated 180 degrees.
FIG. 6A is an enlarged view of FIG. That is, the apparatus main body 1 is currently placed in the state shown in FIG.

  In the position of FIG. 5, the obstacle sensors 17 a to 17 c are arranged only in front of the apparatus main body 100 in the traveling direction, and therefore cannot receive the ultrasonic wave 6 a transmitted from the VW device 2 positioned behind in the traveling direction.

Therefore, the following control method is performed.
If it is determined in s5 that no ultrasonic wave has been received, that is, if any of the obstacle sensors 17a to 17c has not received the ultrasonic wave 6a, the control unit 16 rotates the apparatus main body 1 by 90 degrees to the driver 15. (S6). Then, the apparatus main body 1 changes from the state of FIG. 6A to the state of FIG.

  And the control part 16 judges whether any of the obstacle sensors 17a-17c is receiving the ultrasonic wave (s7).

s6 and s7 are intended to prevent the virtual wall from being noticed by allowing the ultrasonic wave to be received no matter what direction the ultrasonic wave is transmitted to the apparatus main body 1. Therefore, in this embodiment, although it is rotated 90 degrees in s6, it is not limited to this. As long as the ultrasonic wave can be received from any direction from 360 degrees to the apparatus main body 1, it can be received any number of times. You may rotate right behind. In this embodiment in which three obstacle sensors 17 are arranged only in front of the apparatus main body 1 in the direction of travel of the apparatus main body 1 at intervals as shown in FIG. 1, any angle from 70 degrees to 110 degrees is preferable.
In addition, even when two devices are disposed only on both side portions in front of the traveling direction of the apparatus main body 1, any angle from 70 degrees to 110 degrees is preferable.

  If it is determined that an ultrasonic wave is received, that is, if any of the obstacle sensors 17a to 17c receives the ultrasonic wave 6a, the control unit 16 considers that there is a virtual wall and causes the device body 1 to drive the driver 15. (S8), the process proceeds to s2 and the process is continued. That is, the apparatus main body 1 changes from the state of FIG. 6B to the state of FIG. 6C, and travels straight in the direction (a) of the cleaning area without entering the cleaning prohibited area (see FIG. 5).

  As described above, the self-propelled cleaner 1 can be prevented from entering the cleaning prohibited area without increasing the obstacle sensors 17. Moreover, since it is not necessary to increase the number of the obstacle sensors 17, the manufacturing cost of the self-propelled cleaner 1 can be suppressed.

  On the other hand, if it is determined in s7 that no ultrasonic wave has been received, the control unit 16 regards that there is no virtual wall, proceeds to s2, and continues the processing. Here, it is assumed that there is no virtual wall as a result of searching for a sufficiently virtual wall.

The block diagram which showed the structure of the principal part of the self-propelled cleaner which is embodiment of this invention The block diagram which showed the control part of the self-propelled cleaner which is embodiment of this invention, and the structure of the periphery part. Explanatory drawing which showed the structure of the principal part of the self-propelled cleaner which is embodiment of this invention, and the cleaning prohibition area | region and the cleaning area | region. The flowchart which the control part of the self-propelled cleaner which is an embodiment of the present invention performs Explanatory drawing which showed a mode when a self-propelled cleaner stopped at a virtual wall when running a self-propelled cleaner which is an embodiment of the present invention. Explanatory drawing which showed the flow until the self-propelled cleaner which is an embodiment of the present invention stops a run, detects a virtual wall, and rotates 180 degrees Explanatory drawing which showed the structure of the principal part of the conventional self-propelled cleaner, the cleaning prohibition area, and the cleaning area Explanatory drawing which showed a mode that a self-propelled cleaner invades a cleaning prohibition area when a self-propelled cleaner is made to run by a conventional control method.

Explanation of symbols

1-Self-propelled cleaner 2-VW device 3-Wall 6 Transmitter 6a-Electromagnetic wave or ultrasonic wave, virtual wall 11-Drive motor 12-Drive wheel 13-Brush 14-Distance sensor 15-Driver 16-Control Part 17-obstacle sensor 18-reception sensor 19-interface 20-main controller 22-operation panel 24-counter 30-suction part 100-conventional self-propelled cleaner

Claims (4)

A receiving sensor for receiving ultrasonic waves transmitted from an ultrasonic transmitter;
In a self-propelled cleaner provided with autonomous running means for rotating the drive main body to autonomously travel the apparatus main body, and when the reception sensor receives the ultrasonic wave, the apparatus main body is rotated to travel.
Two of the reception sensors are arranged only on both sides of the front of the apparatus main body in the traveling direction, or one is arranged at the center of the front of the main body of the apparatus and two on both sides,
The autonomous traveling means autonomously travels the device main body in a certain distance unit, and determines whether the reception sensor receives the ultrasonic wave every time the device main body travels the certain distance,
When the autonomous traveling means determines that the reception sensor is not receiving the ultrasonic wave, the autonomous traveling means rotates the apparatus main body at any angle from 70 degrees to 110 degrees, and the reception sensor receives the ultrasonic wave. Self-propelled vacuum cleaner that judges again whether or not. A receiving sensor for receiving ultrasonic waves or electromagnetic waves transmitted from an ultrasonic transmitter or electromagnetic wave transmitter;
In a self-propelled cleaner provided with autonomous traveling means that rotates a driving wheel to autonomously travel the apparatus main body, and the reception sensor receives the ultrasonic waves or the electromagnetic waves, the apparatus main body rotates to travel.
The reception sensor is disposed only in the forward direction of the apparatus main body,
The autonomous traveling means autonomously travels the device main body in a certain distance unit, and determines whether the reception sensor receives the ultrasonic wave or the electromagnetic wave every time the device main body travels the certain distance. And
When the autonomous traveling means determines that the reception sensor does not receive the ultrasonic wave or the electromagnetic wave, the autonomous traveling unit rotates the apparatus main body sideways in the traveling direction or backward in the traveling direction, and the reception sensor detects the ultrasonic wave or the electromagnetic wave. Self-propelled vacuum cleaner that judges again whether or not it is received. Two receiving sensors are arranged only on both sides of the front of the apparatus main body in the traveling direction,
3. The self-running according to claim 2, wherein the autonomous running means rotates the apparatus main body at any angle from 70 degrees to 110 degrees when the receiving sensor determines that the ultrasonic wave or the electromagnetic wave is not received. Type vacuum cleaner. The reception sensor is arranged at one central portion and two at both side portions in the forward direction of the apparatus main body,
3. The self-running according to claim 2, wherein the autonomous running means rotates the apparatus main body at any angle from 70 degrees to 110 degrees when the receiving sensor determines that the ultrasonic wave or the electromagnetic wave is not received. Type vacuum cleaner.

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