Conventionally, various types of moving bodies for carrying people or things have been distributed. Moreover, a moving body of an autonomous traveling type has been proposed as a moving body, and thereby is able to be used not only for transportation but also for monitoring (guard) of surroundings. Then, regardless of being used for transportation or being used for monitoring, and regardless of being the autonomous traveling type or not, some moving bodies have an object recognition unit mounted thereon. The object recognition unit is provided for avoiding collision with another moving body or an obstacle, and examples thereof include an active sensor for sensing an obstacle or one that recognizes an obstacle from a captured image by using a camera that photographs surroundings in a front side or the like. Examples of the active sensor include a radio wave radar and a laser range finder which utilize a reflected wave.
Patent Literature 1 discloses a contact avoidance support apparatus of a vehicle, which supports contact avoidance with an obstacle by, when a front-side obstacle sensor senses a distance of an obstacle in front of a vehicle, calculating a target speed of the vehicle in accordance with the distance to the obstacle and controlling a braking force on the basis of the target speed. Note that, in the apparatus, the calculated target speed is corrected in accordance with any of a steering angle and a steering angle speed of a steering wheel and accelerator opening by an operation of a driver.
Description will be given for setting of a target speed of an obstacle sensing vehicle with use of a technique according to Patent Literature 1 by taking a laser range finder as an example of the front-side obstacle sensor with reference to FIG. 1A to FIG. 2B. A laser range finder F illustrated in FIG. 1A emits laser light from a light emission surface Fa thereof, and, in a case of assuming a flat plane that is distant by a predetermined distance, scans it at a scanning pitch H in a horizontal direction and at a scanning pitch V in a vertical direction, receives a reflected wave at each scanning point, and measures a distance d by a reception timing thereof. In this manner, the laser range finder F is able to recognize an object (and measure a distance) within the distance d, in which detection is possible, as to each of measurement points prescribed by the scanning pitches H and V.
FIG. 1B illustrates a top view of the laser range finder F of FIG. 1A. In a case where there is an obstacle D, the obstacle D is able to be recognized at a position of a distance d1, as exemplified in FIG. 1C in which a viewpoint is similar to that of FIG. 1B. Moreover, it is possible to recognize a shape and a depth of the obstacle D by distribution of the distance d1. When description is given with a viewpoint facing a front side from the light emission surface Fa, the obstacle D is to be recognized at a position exemplified in FIG. 1D. Note that, in FIG. 1D, an example in which the obstacle D has a stick shape is cited for simplification.
By using such a laser range finder F (one that has measurement points each 16 points of which are arrayed in the horizontal direction and each 10 points of which are arrayed in the vertical direction as illustrated in FIG. 1D), an obstacle is recognized, and a target speed is set in accordance with the recognized obstacle (part surrounded by a rectangular) D.
Description will be given specifically with reference to FIG. 2A. A case where an obstacle (object) is to go across from the right to the left in a front side of the laser range finder F is cited here as an example. In this case, as time elapses as time 0, 1, 2, 3, and 4, the number of measurement points at each of which the laser range finder F measures a distance to be short changes to 0, 7, 14, 7, and 14, respectively. It is set that the time 0 is time when determination is made as being risky while a moving body that mounts the laser range finder F thereon is traveling at high speed. When a threshold of the determination is set to be 10 here, determination is made as being risky in a case where the number of measurement points at each of which a distance is shorter than a predetermined distance is 10 or more, and when determination is made as being risky, the target speed is set to be a value of a low speed, and when determination is made as being safe, the target speed is set to be a value of a high speed. Thereby, a speed of the moving body changes as illustrated in FIG. 2B.
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