JP2017091087A - Autonomous mobile body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an autonomous mobile body capable of reducing the possibility of contact and collision with an obstacle during travelling regardless of material and reflectance of the obstacle, when a light receiving part is a position sensitive detector (PSD).SOLUTION: An autonomous mobile body 100 includes: a light emission part 11; a light receiving part 12; a distance detection part 20; a storage part 30; and a travelling speed control part 51. The light emission part 11 projects ranging light on an obstacle. The light receiving part 12 receives incoming reflection light from the obstacle, so as to output two signals according to an incident position. The storage part 30 stores a plurality of filter parameters associated with the intensity of received light at the light receiving part 12. The travelling speed control part 51 controls a travelling speed according to the intensity of the received light of the reflection light which has entered the light receiving part 12. The distance detection part 20 for detecting a distance to the obstacle by using the two signals selects the filter parameter corresponding to the intensity of the received light of the reflection light which has entered the light receiving part 12 from the storage part 30, so as to use it for the detection of the distance.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an autonomous mobile body.

  2. Description of the Related Art An autonomous mobile body such as a self-propelled vacuum cleaner that detects an obstacle existing in a traveling space by a non-contact sensor and performs traveling control so as to avoid contact or collision with the obstacle is known. Patent Document 1 includes an infrared sensor having a light emitting element (light emitting part) that emits infrared light and a light receiving element (light receiving part) that receives infrared light that has reached and reflected the obstacle, and the infrared light reflected by the obstacle. An autonomous moving body that detects the position of an obstacle from the incident position in the light receiving element is described.

JP 2007-193538 A

  When the light receiving part is a position detecting element (PSD: Position Sensitive Detector), the light receiving intensity of the reflected light from the obstacle varies depending on the material and reflectance of the obstacle. For example, when the obstacle is a step on the floor surface, the light receiving intensity of the reflected light from the floor step varies depending on the material of the floor surface (carpet, tile, stone, tatami, etc.). Further, if the floor surface reflectance varies depending on the color of the floor surface and whether or not the floor surface is glossy, the light receiving intensity of the reflected light from the steps on the floor surface is different. If the light receiving intensity of the light reflected from the obstacle is weak, the position detection accuracy decreases. For this reason, depending on the material and reflectivity of the obstacle, the position of the obstacle cannot be detected accurately, and there is a possibility that the obstacle may come into contact with or collide with the obstacle.

  The present invention has been made in view of the above background, and when the light receiving unit is a PSD, it can autonomously reduce the risk of contact with and collision with an obstacle during travel, regardless of the material or reflectance of the obstacle. The object is to provide a moving body.

  The present invention is an autonomous mobile body that is travel-controlled according to the distance to an obstacle existing in the travel space, and a light emitting unit that projects distance measuring light onto the obstacle, and the obstacle of the distance measuring light A light receiving unit that receives reflected light from an object and outputs two signals corresponding to the incident position, a distance detection unit that detects a distance to an obstacle using the two signals, and a light receiving unit that receives the light. A storage unit that stores a plurality of filter parameters associated with the intensity; and a moving speed control unit that controls a moving speed according to the received light intensity of the reflected light incident on the light receiving unit. A filter parameter corresponding to the received light intensity of the reflected light incident on the light receiving unit is selected from the storage unit, and the filter parameter is used in the detection of the distance.

  According to the present invention, when the light receiving unit is a PSD, it is possible to reduce the risk of contact with or collision with an obstacle during travel, regardless of the material and reflectance of the obstacle.

It is a block diagram which shows schematic structure of the autonomous mobile body concerning this Embodiment. It is a figure explaining the detection method of the distance from an autonomous mobile body to an obstruction by a distance sensor. It is a figure explaining the preservation | save format of the noise filter in a memory | storage part. It is a figure explaining control of the moving speed of the autonomous mobile body by a moving speed control part. It is a flowchart which shows the flow of the process which detects the distance from an autonomous mobile body to an obstruction using the filter parameter according to received light intensity.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram illustrating a schematic configuration of the autonomous mobile body 100. As shown in FIG. 1, the autonomous mobile body 100 includes a distance sensor 10, a distance detection unit 20, a storage unit 30, a travel unit 40, and a travel control unit 50.

  The distance sensor 10 is a sensor for detecting the distance from the autonomous mobile body 100 to the obstacle H, and includes a light emitting unit 11 and a light receiving unit 12. The light emitting unit 11 is, for example, an infrared light emitting element (IRED: Infrared-emitting diode), and projects the distance measuring light P <b> 1 onto the obstacle H. The light receiving unit 12 is a position detecting element (PSD: Position Sensitive Detector). When the reflected light P2 from the obstacle H of the ranging light P1 is incident, the light receiving unit 12 outputs two signals (photocurrents I1 and I2) according to the incident position of the reflected light.

  The distance detection unit 20 detects the distance from the autonomous mobile body 100 to the obstacle H using the two signals output from the light receiving unit 12. Details of the method for detecting the distance from the autonomous mobile body 100 to the obstacle H will be described later. The storage unit 30 stores a plurality of filter parameters associated with the received light intensity at the light receiving unit 12. Here, the filter parameter is the number of samplings of the noise filter applied to remove noise in the detection of the distance from the autonomous mobile body 100 to the obstacle H via the distance sensor 10.

  The traveling unit 40 includes a pair of left and right wheels and a motor that drives the wheels. The wheels rotate independently on the left and right. The autonomous mobile body 100 moves forward or backward by rotating both wheels simultaneously. Moreover, the autonomous mobile body 100 turns when each wheel rotates in a different direction or when one wheel stops and the other wheel rotates.

  The travel control unit 50 includes information D1 on the distance to the obstacle H detected by the distance detection unit 20 such that the autonomous mobile body 100 travels without contacting or colliding with the obstacle H present in the travel space. The traveling unit 40 is controlled based on the above. In addition, the travel control unit 50 includes a moving speed control unit 51. The moving speed control unit 51 controls the moving speed according to the received light intensity of the reflected light incident on the light receiving unit 12. Details of the control of the moving speed of the autonomous mobile body 100 by the moving speed control unit 51 will be described later.

Here, a method for detecting the distance from the autonomous mobile body 100 to the obstacle H in the distance detection unit 20 will be described below. The principle of triangulation is used to detect the distance from the autonomous mobile body 100 to the obstacle H.
FIG. 2 is a diagram for explaining a method for detecting the distance from the autonomous mobile body 100 to the obstacle H in the distance detection unit 20. As shown in FIG. 2, the distance measuring light P <b> 1 emitted by the light emitting unit 11 is collected by the light projecting lens 13 and emitted toward the obstacle H. The reflected light P2 from the obstacle H enters the light receiving unit 12 through the light receiving lens 14 and forms an image at the incident position N.

  The light receiving unit 12 outputs two signals (photocurrents I1 and I2) corresponding to the incident position N. When the distance from the center line C of the incident position N is x and the total length of the light receiving unit 12 is t, the ratio of the two photocurrents I1 and I2 is I1 / I2 = (t / 2 + x) / (t / 2−x ). When the equation is transformed, x = {(I2−I1) / (I1 + I2)} × (t / 2).

  The distance L between the light projecting lens 13 and the obstacle H, the distance S between the light projecting lens 13 and the light receiving lens 14, and the focal length of the light receiving lens 14 (the distance between the light receiving lens 14 and the imaging surface of the light receiving unit 12). Let f. The distance L between the light projecting lens 13 and the obstacle H is regarded as the distance from the autonomous mobile body 100 to the obstacle H. Since L: S = f: x based on the principle of triangulation, the distance L between the projection lens 13 and the obstacle H can be expressed as L = S × (f / x). Substituting the above formula for the distance x from the center line C of the incident position N, L = S × f / {(I2−I1) / (I1 + I2)} / (t / 2).

  The total length t of the light receiving unit 12, the distance S between the light projecting lens 13 and the light receiving lens 14, and the focal length f of the light receiving lens 14 are predetermined values. Therefore, the distance from the autonomous mobile body 100 to the obstacle H (distance L between the light projecting lens 13 and the obstacle H) is detected by measuring the two photocurrents I1 and I2 output from the light receiving unit 12. Can do.

  Depending on the material and the reflectance of the obstacle H, the light receiving intensity of the reflected light P2 from the obstacle H in the light receiving unit 12 is different. For example, when there is a step on a carpet or a black floor surface, the received light intensity of reflected light incident on the light receiving unit 12 decreases. Due to the characteristics of the PSD, if the received light intensity of the reflected light P2 from the obstacle H in the light receiving unit 12 is small, the influence of noise increases, and the detection accuracy (position detection accuracy) of the distance from the autonomous mobile body 100 to the obstacle H is increased. descend.

  The sum (I1 + I2) of the photocurrents I1 and I2 output from the light receiving unit 12 when receiving the reflected light P2 is a value corresponding to the magnitude of the received light intensity of the reflected light P2. That is, if the sum of photocurrents (I1 + I2) is relatively large, the position detection accuracy by the distance sensor 10 is relatively high, and if the sum of photocurrents (I1 + I2) is relatively small, the position detection accuracy by the distance sensor 10 is relative. Lower. Therefore, the received light intensity can be detected by obtaining the sum (I1 + I2) of the photocurrents I1 and I2.

  In the detection of the distance from the autonomous mobile body 100 to the obstacle H via the distance sensor 10, if the influence of noise is large, it is necessary to increase the number of samplings of the applied noise filter. The distance detection unit 20 selects a filter parameter (sampling number) corresponding to the received light intensity of the reflected light incident on the light receiving unit 12 from the storage unit 30. Then, the filter parameter of the noise filter applied in the detection of the distance from the autonomous mobile body 100 to the obstacle H is the filter parameter selected from the storage unit 30.

  FIG. 3 is a diagram for explaining the storage mode of the filter parameters in the storage unit 30. As shown in FIG. 3, the plurality of filter parameters are stored in association with the corresponding received light intensity. The filter parameter NA is an optimum filter parameter of the noise filter when the received light intensity is A. Similarly, the filter parameter NB is the optimum filter parameter of the noise filter when the received light intensity is B, the filter parameter NC is the received light intensity C, and the filter parameter ND is the received light intensity D. . The received light intensities A to D have different sizes.

  As described above, the sum (I1 + I2) of the photocurrents I1 and I2 output from the light receiving unit 12 when receiving the reflected light P2 is a value corresponding to the magnitude of the received light intensity of the reflected light P2. The sum of the photocurrents I1 and I2 (I1 + I2) may be used. The received light intensity and the number of filter parameters stored in the storage unit 30 are not limited to four. If the received light intensity and the number of filter parameters to be stored in the storage unit 30 are increased, it becomes possible to select a filter parameter that is more suitable for the received light intensity of the reflected light incident on the light receiving unit 12. The accuracy of detecting the distance up to can be further improved.

A method for determining the filter parameter of the noise filter corresponding to the received light intensity stored in the storage unit 30 will be described below.
In a situation where the actual distance (true distance) from the autonomous mobile body 100 to the obstacle H is known, detection of received light intensity and the distance sensor 10 for a plurality of conditions with different materials and reflectivities of the obstacle H. The distance from the autonomous mobile body 100 to the obstacle H via is detected. Under each condition, the filter parameter (sampling number) of the noise filter to be applied is determined so that the detected distance (detected distance) from the autonomous mobile body 100 to the obstacle H approaches the true distance. In this way, a plurality of filter parameters corresponding to the received light intensity can be determined.

Control of the moving speed of the autonomous mobile body 100 by the moving speed control unit 51 will be described below.
As described above, when the received light intensity is small, it is necessary to increase the sampling number of the applied noise filter. For example, in FIG. 3, when the magnitude relationship between the received light intensities A to D is A>B>C> D, the magnitude relationship between the filter parameters (number of samplings) corresponding to each received light intensity is NA <NB <NC. <ND.

  If the number of samplings of the noise filter is increased, the time delay due to the noise filter increases, and the responsiveness in detecting the distance to the obstacle H by the distance sensor 10 decreases. Here, the responsiveness is the time required for the distance from the autonomous mobile body 100 to the obstacle H to be detected after the autonomous mobile body 100 recognizes the obstacle H. In order to prevent the autonomous mobile body 100 from contacting or colliding with the obstacle H while detecting the distance from the autonomous mobile body 100 to the obstacle H, the autonomous mobile body 100 is used when the received light intensity is small. It is necessary to reduce the movement speed.

  FIG. 4 is a diagram for explaining the control of the movement speed of the autonomous mobile body 100 by the movement speed control unit 51. As shown in FIG. 4, when the received light intensity detected via the distance sensor 10 is relatively large, the moving speed control unit 51 relatively increases the set value of the maximum speed of the autonomous moving body 100. When the received light intensity detected via the distance sensor 10 is relatively small, the moving speed control unit 51 relatively reduces the set value of the maximum speed of the autonomous moving body 100. By doing in this way, it can prevent that the autonomous mobile body 100 contacts or collides with the obstacle H, while detecting the distance from the autonomous mobile body 100 to the obstacle H.

A flow of processing for detecting the distance from the autonomous mobile body 100 to the obstacle H using a filter parameter corresponding to the received light intensity will be described.
FIG. 5 is a flowchart showing a flow of processing for detecting the distance from the autonomous mobile body 100 to the obstacle H using a filter parameter corresponding to the received light intensity. As shown in FIG. 5, first, the distance detection unit 20 detects the received light intensity of the reflected light from the obstacle H incident on the light receiving unit 12 of the distance sensor 10 (step S1). Next, the distance detection unit 20 selects a filter parameter corresponding to the received light intensity detected in step S1 from the storage unit 30 (step S2). Subsequent to step S2, the moving speed of the autonomous mobile body 100 corresponding to the detected light reception intensity is selected (step S3). Subsequently, the distance from the autonomous mobile body 100 to the obstacle H is detected by applying a noise filter using the filter parameter selected in step S2 (step S4). While the autonomous mobile body 100 is traveling, the processing from step S1 to step S4 is repeated.

  As described above, when the light receiving unit is a PSD, the noise applied in the detection of the distance from the autonomous mobile body 100 to the obstacle H measured through the distance sensor 10 according to the received light intensity of the reflected light incident on the light receiving unit. By selecting the filter parameter of the filter, it is possible to reduce the possibility of contact with or collision with an obstacle during traveling, regardless of the material and reflectance of the obstacle.

  Note that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 100 Autonomous mobile body 10 Distance sensor 11 Light emission part 12 Light receiving part 20 Distance detection part 30 Memory | storage part 40 Traveling part 50 Traveling control part 51 Movement speed control part I1, I2 Output current H Obstacle

Claims (1)

An autonomous mobile body that is travel-controlled according to the distance to the obstacle present in the travel space,
A light emitting unit that projects distance measuring light onto an obstacle;
A light receiving unit that receives reflected light from an obstacle of the distance measuring light and outputs two signals according to the incident position;
A distance detector that detects the distance to the obstacle using the two signals;
A storage unit for storing a plurality of filter parameters associated with the received light intensity at the light receiving unit;
A moving speed control unit that controls the moving speed according to the received light intensity of the reflected light incident on the light receiving unit,
The distance detection unit is an autonomous mobile body that selects a filter parameter corresponding to the received light intensity of the reflected light incident on the light receiving unit from the storage unit, and uses the filter parameter in the distance detection.

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