JP7006203B2 - Trajectory setting device - Google Patents

Description

The present disclosure relates to a technique for setting a trajectory used for traveling in automatic driving.

The following Patent Document 1 describes a technique for setting a route to be traveled based on information on the surroundings of a vehicle in automatic driving.

Japanese Unexamined Patent Publication No. 2015-72650

However, as a result of detailed examination by the inventor, the following problems have been found in the prior art.
That is, when traveling along the travel route, the planned locus, which is a locus representing the position of the vehicle in the roadway, is set according to the surrounding conditions. In particular, when no obstacle is recognized in the lane in the same traveling direction as the own vehicle, the planned locus is set so that the vehicle travels in the center of the lane. Therefore, for example, when the lane width is narrow and the vehicle passes by a large vehicle, the driver may feel that the vehicle is closer than necessary to the oncoming vehicle.

On the other hand, it is also conceivable to detect an oncoming vehicle and correct the traveling route. However, if the detection accuracy of the sensor that detects an oncoming vehicle is unstable due to a bad environment, etc., if the detection of the oncoming vehicle is delayed, sudden steering to avoid a dangerous situation will occur, causing the driver to feel uneasy. There was a possibility that it would end up.

One aspect of the present disclosure is to provide a technique for suppressing the occurrence of sudden steering in order to avoid a dangerous situation in automatic driving.

The locus setting device according to one aspect of the present disclosure includes a setting unit (20: S190) and a correction unit (20: S200 to S250).
The setting unit sets a planned locus, which is a series of data representing the position of the vehicle in the route width direction on the planned route on which the vehicle travels. When the lane width of the lane in which the planned locus is set by the setting unit is less than the preset lower limit width, the correction unit sets the planned locus in a direction in which it becomes easy or unnecessary to take action to deal with the danger assumed in advance. to correct.

According to such a configuration, it is possible to suppress the occurrence of sudden steering for avoiding a dangerous situation in a vehicle that automatically drives according to a planned trajectory. For example, assuming the appearance of an oncoming vehicle, by correcting the planned trajectory in the direction away from the oncoming lane, when the oncoming vehicle actually appears, the coping action for the appearance of the oncoming vehicle is executed with a margin. It can be done or the coping action itself can be eliminated. As a result, it is possible to suppress the occurrence of sudden steering in automatic driving.

In addition, the reference numerals in parentheses described in this column and the scope of claims indicate the correspondence with the specific means described in the embodiment described later as one embodiment, and the technical scope of the present disclosure is defined. It is not limited.

It is a block diagram which shows the structure of the driving support system 1. It is explanatory drawing about a parameter. It is a flowchart of the locus setting process executed by a processing unit. It is explanatory drawing which shows the search range of a lane marking. It is explanatory drawing which shows the search range of a track boundary. It is explanatory drawing which illustrates the case where the planned locus is corrected. It is explanatory drawing which illustrates the case where a planned locus is not corrected. It is explanatory drawing which illustrates the corrected schedule locus. It is explanatory drawing which illustrates the planned locus which is not corrected.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.
[1. Constitution]
As shown in FIG. 1, the driving support system 1 includes a driving support device 2 mounted on a vehicle and a server 3 capable of wireless communication with the driving support device 2. Hereinafter, the vehicle on which the driving support device 2 is mounted is referred to as a own vehicle.

The server 3 stores learning data representing an average traveling locus calculated by learning in association with map data. The travel locus is a series of data representing the position of the vehicle in the route width direction in the travel route of the vehicle. The training data is generated as follows. That is, the travel locus measured when the vehicle travels on the road is acquired from a plurality of vehicles, and learning is executed using the acquired travel locus. However, here, the measurement results in an environment where there are no stationary vehicles such as stopped vehicles or pedestrians whose relative speed to the own vehicle is close to the own vehicle speed in the area on the road belonging to the same traveling direction as the own vehicle are used. Be done.

When the server 3 receives the position information indicating the current position of the vehicle and the direction information indicating the traveling direction of the vehicle from the driving support device 2 that is the request source, the server 3 moves from the position indicated by the position information to a predetermined distance in the direction indicated by the direction information. The learning data of the crossing track is returned to the requester.

The operation support device 2 includes a processing unit 20. The processing unit 20 corresponds to a locus setting device. Further, the driving support device 2 may include a position detection sensor 21, an environment recognition sensor 22, an in-vehicle communication unit 23, a map database 24, an out-of-vehicle communication unit 25, and a vehicle control unit 26.

The position detection sensor 21 is a sensor that receives a signal for specifying the current position of the own vehicle and outputs the signal to the processing unit 20. For example, a sensor using the Global Positioning System (hereinafter referred to as GPS) can be used. Not limited to this, sensors used for autonomous navigation such as a vehicle speed sensor and a gyroscope may be used together.

As shown in FIG. 2, the environment recognition sensor 22 detects various objects existing in the recognition target area 42 in front of the own vehicle 41. The recognition target area 42 is a region of the road on which the own vehicle is traveling that belongs to the same traveling direction as the own vehicle, that is, another lane having the same traveling direction as the lane in which the own vehicle is traveling (hereinafter referred to as the own lane). And at least a shoulder or roadside zone located on the left side of the vehicle in the direction of travel. The environment recognition sensor 22 includes at least a camera that acquires an image (hereinafter referred to as a front image) obtained by capturing an image of the recognition target area 42. The camera may be a stereo camera or a monocular camera. The environment recognition sensor 22 may include at least one of a lidar and a millimeter wave radar instead of or in combination with the camera. LIDAR is a device that detects the position of an object that reflects light by irradiating light and receiving the reflected light.

The in-vehicle communication unit 23 executes communication via an in-vehicle LAN that connects various devices mounted on the vehicle to each other. LAN is a local area network. The in-vehicle communication unit 23 acquires detection signals from various sensors that detect the behavior of the vehicle via the in-vehicle LAN. The behavior of the vehicle to be detected includes at least speed.

The map database 24 stores map data related to the road on which the vehicle can travel. The map data has at least map information regarding the position and type of the road, facilities around the road, and road information indicating the shape of the road. Road information includes information such as the curvature, slope, and road structure of a road, which indicates the direction in which the road extends, such as a straight line or a curve. The road information further includes the position of the lane marking line (that is, the center line of the lane, the lane boundary line, the outside line of the lane, etc.), the position of the lane boundary, the number and position of lanes, and the width of each lane (hereinafter referred to as lane width). Contains the information needed to identify.

The lane center line is a lane marking that separates the oncoming lanes. The lane boundary line is a lane marking line that separates lanes when there are a plurality of lanes in the same direction. The outside line of the road is a lane marking line located on the leftmost side in the direction of travel. The track boundary is a boundary on the opposite side of the road shoulder or the roadside zone from the outside line side of the road. Further, for example, the position of the roadway center line is expressed by the positioning coordinate system used by the position detection sensor 21, and the positions of the lane boundary line, the roadway outside line, and the roadway boundary are expressed by the distance from the roadway center line. .. Further, as shown in FIG. 2, the lane width of the own lane extracted from the road information is defined as WK. Further, let C be the width of the own vehicle, which is known information.

The out-of-vehicle communication unit 25 acquires the learning data stored in the server 3 by wireless communication with the server 3. The out-of-vehicle communication unit 25 may use, for example, a mobile phone network, a road-to-vehicle communication facility, a dedicated wireless communication network, or the like.

The vehicle control unit 26 executes processing such as steering and warning related to automatic driving according to a scheduled trajectory set by the processing unit 20. The planned locus is a travel locus on which the own vehicle is scheduled to travel.
The processing unit 20 includes a microcomputer having a CPU 201 and, for example, a semiconductor memory such as RAM or ROM (hereinafter, memory 202). Each function of the processing unit 20 is realized by the CPU 201 executing a program stored in a non-transitional substantive recording medium. In this example, the memory 202 corresponds to a non-transitional substantive recording medium in which a program is stored. In addition, when this program is executed, the method corresponding to the program is executed. The processing unit 20 may include one microcomputer or a plurality of microcomputers.

The method for realizing the functions of the processing unit 20 is not limited to software, and some or all of the functions may be realized by using one or a plurality of hardware. For example, when the above function is realized by an electronic circuit which is hardware, the electronic circuit may be realized by a digital circuit, an analog circuit, or a combination thereof.

[2. process]
Next, the locus setting process executed by the processing unit 20 will be described with reference to the flowchart of FIG. When the driving support device 2 is activated, this process is repeatedly executed at a preset cycle.

When this process is activated, the processing unit 20 acquires the current position in S110 according to the detection signal from the position detection sensor 21.
In S120, the processing unit 20 acquires a front image from the environment recognition sensor 22.

In S130, the processing unit 20 acquires the map information around the current position acquired in S110 from the map database 24. As shown in FIG. 2, the map information is acquired for the peripheral area 43 of the own vehicle 41 including the recognition target area 42 by the environment recognition sensor 22.

In S140, the processing unit 20 executes a range setting process for setting a search range to be searched when recognizing a division line and a track boundary in the front image. Specifically, as shown in FIGS. 4 and 5, from the current position acquired in S110 and the position of the lane marking and the track boundary shown in the map information, the position of the lane marking in the forward image La, The positions Lc of Lb and the runway boundary are estimated, and the range of the preset margin width M centered on the estimated positions La, Lb, and Lc is set as the search range. The margin width M may be different between the lane marking line and the track boundary.

In S150, the processing unit 20 recognizes lane markings (hereinafter referred to as non-center lane markings) and track boundary candidates other than the roadway center line detected in the search range in the forward image as non-center lane markings and track boundaries. Executes the reference setting process for setting the allowable range of the judgment parameter used when judging whether or not the judgment is allowed.

In the reference setting process, the distance from the center line of the roadway is used as a determination parameter for both the non-central division line and the track boundary. Specifically, the distance from the center line of the roadway extracted from the map information to the non-central lane marking or the lane boundary is Wm, and the distance from the center line of the roadway extracted from the front image to the non-central lane marking or the lane boundary is Ws. The permissible range is set as shown in the equation (1). However, α is a real number satisfying 0 <α <1. α is appropriately set according to the resolution of the environment recognition sensor 22 used for recognizing the lane markings and the track boundaries, and may be different between the non-central lane markings and the track boundaries.

なお、Ｓ１４０及びＳ１５０の処理は、探索範囲及び許容範囲の算出に必要な情報が地図情報に含まれていない場合は、省略してもよい。その場合、探索範囲、許容範囲は、予め設定された固定値を用いる。例えば、区画線の探索範囲は画面全体とし、走路境界の探索範囲は車線外側線の左側全体とすることが考えられる。

The processing of S140 and S150 may be omitted if the map information does not include the information necessary for calculating the search range and the allowable range. In that case, a preset fixed value is used for the search range and the allowable range. For example, the search range of the lane marking may be the entire screen, and the search range of the track boundary may be the entire left side of the lane outside line.

In S160, the processing unit 20 executes a division line recognition process for recognizing a division line from the front image acquired in S120. Specifically, the processing unit 20 extracts a candidate line that is a candidate for the lane marking from the search range of the lane marking set in S140, and specifies one of the candidate lines as the lane center line. Since the method for specifying the lane center line is known and is not a main part of the present invention, the description thereof is omitted here. Next, the distance Ws from the lane center line to the candidate line other than the lane center line is calculated from the front image, and if the distance Ws satisfies the equation (1), the candidate line is recognized as a lane marking. At this time, based on the positional relationship between the extracted lane markings, map information, and the like, the type of the lane marking, that is, any of the lane center line, the lane boundary line, the lane outside line, and the like is also identified.

In S170, the processing unit 20 executes a boundary recognition process for recognizing the track boundary from the front image acquired in S120. Specifically, the processing unit 20 extracts a candidate line that is a candidate for the track boundary from the search range of the track boundary set in S140. Further, the distance Ws from the center line of the lane to the candidate line is extracted from the forward image, and if the distance Ws satisfies the equation (1), the candidate line is recognized as a track boundary.

In S180, the processing unit 20 executes an object recognition process for recognizing an object from the front image acquired in S120. Specifically, the processing unit 20 extracts various objects by using a known method such as pattern matching. Further, the position of the extracted object and the relative velocity with the object are also detected by using the detection signals from the lidar and the millimeter wave radar included in the environment recognition sensor 22. Then, based on the own vehicle speed acquired via the in-vehicle communication unit 23 and the relative speed of the extracted object, it is identified whether or not the extracted object is a stationary equivalent such as a pedestrian or a stopped vehicle. .. Here, an object whose relative speed with respect to the own vehicle is less than a preset stationary threshold value is referred to as a stationary equivalent object.

In S190, the processing unit 20 sets a scheduled locus according to the traveling route provided from the outside and the recognition results in S160 to S180. Basically, it is set so that the vehicle runs in the center of the vehicle lane. However, if there are stationary equivalents in the same direction track, the planned trajectory is set so that a safe distance is maintained between them and the stationary equivalents. The same-direction track is an area between the center line of the road including the position of the own vehicle and the boundary of the track. Further, if there are stationary equivalents on both the left and right sides of the own lane, the planned locus is set so as to travel at an intermediate position between the two obstacles.

In S200, the processing unit 20 determines whether or not the stationary equivalent object recognized in S180 exists in the same-direction track recognized in S160 and S170. If there is a stationary equivalent, it is assumed that it is not necessary to correct the planned locus, and the process proceeds to S260. If there is no stationary equivalent, the process proceeds to S210. When there is no stationary equivalent, the planned locus set in S190 is usually located in the center of the own lane.

In S210, the processing unit 20 determines whether or not the lane width of the lane in which the scheduled locus is set is less than the preset lower limit width. If the lane width is equal to or greater than the lower limit width, it is assumed that it is not necessary to correct the planned locus, and the process proceeds to S260. If the lane width is less than the lower limit width, the process proceeds to S220.

In S220, the processing unit 20 acquires learning data regarding the travel route in front of the own vehicle from the server 3. Specifically, the information request indicating the current position and the traveling direction acquired in S110 is transmitted to the server 3 via the out-of-vehicle communication unit 25. The server 3 returns the learning data about the traveling route within the preset range according to the current position and the traveling direction indicated in the information request.

In S230, the processing unit 20 determines whether or not the learning data could be acquired from the server 3. If the training data can be acquired, the process proceeds to S240, and if the training data cannot be acquired, the process proceeds to S250.

In S240, the processing unit 20 sets the learning data acquired in S220 as a corrected scheduled locus, and proceeds to S260.
In S250, the processing unit 20 shifts the scheduled locus set in S190 by the calculated shift amount S according to the equation (2) in the direction away from the lane center line, that is, in the direction approaching the track boundary side. And proceed to S260.

ＷＫは区画線幅、Ｃは車幅、ＷＫｆは基準区画線幅、Ｃｆは基準車幅である。基準区画線幅ＷＫｆは、例えば、道路構造令では、一般国道における１日２万台以上の車両が走行する対象となる種別１種１級の道路幅が最大３．５ｍであるため、これを用いてもよい。基準車幅Ｃｆは、例えば、道路構造令では、一般乗用車とされる小型自動車の車幅が１．７ｍと定義されているため、これを用いてもよい。また、区画線幅ＷＫは、実測値でもよいし地図情報から抽出される値であってもよい。

WK is the lane marking width, C is the vehicle width, WKf is the reference lane marking width, and Cf is the reference vehicle width. The standard lane marking width WKf is, for example, according to the Road Structure Ordinance, because the maximum road width of Class 1 Class 1 for which more than 20,000 vehicles travel on general national highways per day is 3.5 m. You may use it. The reference vehicle width Cf may be used, for example, because the Road Structure Ordinance defines that the width of a small vehicle, which is regarded as a general passenger car, is 1.7 m. Further, the division line width WK may be an actually measured value or a value extracted from the map information.

In equation (2), the narrower the lane marking width S is than the reference lane marking width Sf, and the vehicle width C is the reference vehicle width Cf, with the upper limit of the shift amount at which the vehicle does not protrude from the outside line of the road to the lane boundary side. The larger the value, the larger the shift amount.

In S260, the processing unit 20 generates a command for controlling the vehicle according to the scheduled trajectory set in S190 or the corrected scheduled trajectory set in either S240 or S250, and the processing unit 20 generates a command to the vehicle control unit 26. Output and end this process.

In this embodiment, S120 is an image acquisition unit, S130 is a map information acquisition unit, S140 is a range setting unit, S150 is a reference setting unit, S160 to S170 are line recognition units, S180 is an object recognition unit, and S190 is a setting unit. , S200 to S250 correspond to the correction unit, and S220 corresponds to the learning data acquisition unit.

[3. motion]
In the driving support system 1, as shown in FIG. 6, when the lane width is less than the lower limit and there is no stationary equivalent in the lane in the same direction, the planned trajectory set in S190 is set from the center line of the lane to the lane boundary side. Make a correction to shift to. That is, when there are no pedestrians or stopped vehicles that hinder driving, the planned trajectory is corrected so that the coping action for the appearance of the oncoming vehicle becomes easy or unnecessary.

Further, in this case, if the learning data can be acquired from the server 3, the learning data is used as the corrected scheduled trajectory. That is, the traveling locus adopted by many drivers in the past is set as the scheduled locus. In other words, in a driving route where the road width is narrow and many drivers travel at a position shifted from the center of the own lane to the lane boundary side in order to keep a distance from the oncoming vehicle, it is not necessary to obtain the shift amount by processing. However, a scheduled trajectory similar to the corrected scheduled trajectory can be obtained.

In the driving support system 1, as shown in FIG. 7, even if the lane width is less than the lower limit width, if the stationary equivalent 44 exists in the same direction track, the planned trajectory set in S190 is used as it is. .. That is, in order to reduce steering such as collision avoidance with respect to a stationary equivalent object, the planned locus set in consideration of these obstacles is used as it is.

8 and 9 exemplify a planned locus when the own vehicle enters a road having a lane width equal to or more than the lower limit width and a road having a lane width less than the lower limit width. As shown in FIG. 8, when there is no stationary equivalent, the planned trajectory is corrected in the direction away from the center line of the roadway (that is, the oncoming lane) instead of the center of the own lane. As shown in FIG. 9, when a stationary equivalent object exists, the planned route is set so as to travel in the center of the own lane even if the vehicle approaches the center line of the roadway.

[4. effect]
According to the above-described embodiment described in detail above, the following effects are obtained.
(1) According to the driving support system 1, when the lane width of the lane in which the planned locus is set is less than the lower limit width, the correction is performed to shift the planned locus to the lane boundary side. Therefore, the vehicle can be driven on a trajectory that makes it easy or unnecessary to take action to deal with the appearance of an oncoming vehicle. That is, it is possible to suppress the occurrence of sudden steering.

(2) According to the driving support system 1, when a stationary equivalent exists, the planned trajectory set in consideration of the stationary equivalent is used as it is, so that the safety of the stationary equivalent is ensured. Can be done.

(3) According to the driving support system 1, when the learning data exists in the server 3, the scheduled locus is corrected by using the learning data, so that the processing load required for the correction of the scheduled locus can be reduced.

(4) According to the driving support system 1, a search is performed using map information when recognizing a lane marking or a track boundary required for setting or correcting a planned trajectory according to the information obtained from the environment recognition sensor 22. The range and the allowable range of judgment parameters are set. Therefore, the processing load in these recognition processes can be reduced, and the deterioration of the recognition accuracy can be suppressed even in an environment where the detection accuracy of the environment recognition sensor 22 becomes unstable (for example, rain or fog). It can realize robust recognition. As a result, the reliability of setting and correcting the scheduled trajectory can be improved.

[5. Other embodiments]
Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and can be variously modified and implemented.

(A) In the above embodiment, the correction amount for the planned trajectory is changed according to the width of the lane marking and the vehicle width, but the correction amount is not limited to this. For example, depending on the width from the outside line of the road to the boundary of the track, that is, the width of the shoulder or the roadside zone, the wider these widths may be, the larger the correction amount may be.

(B) In the above embodiment, the correction amount of the planned trajectory is limited so that the vehicle does not protrude from the outside line of the road to the boundary side of the track, but the present invention is not limited to this. For example, depending on the situation, the correction amount may be set so as to allow the vehicle to protrude from the outside line of the road.

(C) In the above embodiment, the distance from the center line of the roadway to the non-central division line and the boundary of the track is used as the determination parameter, but the determination parameter is not limited to this. As the determination parameter, for example, in the case of a lane marking, the line width or lane marking width of the lane marking may be used, and in the case of a track boundary, the width from the outside line of the road to the lane boundary may be used.

(D) A plurality of functions possessed by one component in the above embodiment may be realized by a plurality of components, or one function possessed by one component may be realized by a plurality of components. .. Further, a plurality of functions possessed by the plurality of components may be realized by one component, or one function realized by the plurality of components may be realized by one component. Further, a part of the configuration of the above embodiment may be omitted. Further, at least a part of the configuration of the above embodiment may be added or replaced with the configuration of the other above embodiment. It should be noted that all aspects included in the technical idea specified from the wording described in the claims are embodiments of the present disclosure.

(E) In addition to the locus setting device described above, a system having the locus setting device as a component, a program for operating a computer as the locus setting device, and a non-transitional actual recording of a semiconductor memory or the like in which this program is recorded. The present disclosure can also be realized in various forms such as a medium and a trajectory setting method.

1 ... Driving support system, 2 ... Driving support device, 3 ... Server, 20 ... Processing unit, 21 ... Position detection sensor, 22 ... Environment recognition sensor, 23 ... In-vehicle communication unit, 24 ... Map database, 25 ... External communication unit, 26 ... vehicle control unit, 41 ... own vehicle, 42 ... recognition target area, 43 ... surrounding area, 44 ... stationary equivalent, 201 ... CPU, 202 ... memory.

Claims (8)

A setting unit (20: S190) for setting a planned locus, which is a series of data representing the position of the vehicle in the route width direction on the planned route on which the vehicle travels.
When the lane width of the lane in which the scheduled locus is set by the setting unit is less than the preset lower limit width, the scheduled locus is corrected in a direction that facilitates or eliminates the action for dealing with the danger assumed in advance. The correction unit (20: S200 to S250) configured to do so,
Equipped with
The coping action is an action of avoiding an oncoming vehicle.
The correction unit is configured to correct the planned locus in a direction in which the position of the vehicle is away from the boundary line with the oncoming lane.
Trajectory setting device. The locus setting device according to claim 1 .
A line recognition unit (20) configured to recognize a lane marking line including a road center line and a road outside line existing in front of the vehicle, and a road boundary which is a boundary of a road including a lane and a road shoulder or a roadside zone. : S160, S170)
The correction unit is configured so that the narrower the lane width of the lane in which the scheduled route is set, the larger the correction amount of the scheduled trajectory.
Trajectory setting device. The locus setting device according to claim 2 .
The correction unit is a track setting device configured to limit the correction amount of the planned track so that the vehicle does not protrude from the outside line of the road to the boundary side of the track. The locus setting device according to claim 2 or 3 .
Further, an object recognition unit (20: S180) configured to recognize at least a stationary equivalent object existing in front of the vehicle and whose relative speed with the vehicle is less than a preset stationary threshold value is further provided. Prepare,
The correction unit is configured to correct the planned trajectory when the stationary equivalent object is not recognized in the region between the roadway center line where the vehicle is located and the track boundary by the object recognition unit. Trajectory setting device. The locus setting device according to any one of claims 2 to 4 .
An image acquisition unit (20: S120) that acquires a front image of the front of the vehicle, and
A map information acquisition unit (20: S130) configured to acquire map information in front of the vehicle, and
At least one of the lane marking line and the track boundary is set as a detection target, and a search range that is a range for searching the detection target on the front image is set according to the information about the detection target shown in the map information. The range setting unit (20: S140) configured as described above,
Based on the map information, it is configured to set an allowable range of determination parameters used when determining whether or not the target candidate, which is the candidate for the detection target extracted from the front image, is the detection target. Reference setting unit (20: S150) and
Further prepare
The line recognition unit selects the target candidate when the determination parameter of the target candidate detected within the search range of the front image is within the permissible range set by the reference setting unit. Configured to be recognized as a detection target,
Trajectory setting device. The locus setting device according to claim 5 .
The detection target includes at least the division line, and the detection target includes at least the division line.
The determination parameter is a locus setting device which is the width between the division lines. The locus setting device according to claim 5 or 6 .
At least including the track boundary as the detection target,
The determination parameter is a locus setting device which is the width between the division line and the track boundary. The locus setting device according to any one of claims 1 to 7 .
To acquire the learning data corresponding to the planned trajectory set by the setting unit from the server that stores the learning data obtained by learning the traveling loci of a large number of vehicles based on the measured values in association with the map. Further equipped with a learning data acquisition unit (20: S220) configured in
The correction unit is configured to use the training data as the corrected scheduled locus when the training data is present.
Trajectory setting device.

Images