汽車倒車時防撞自動測距警報系統(tǒng)設(shè)計畢業(yè)論文-資料下載頁
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【正文】 tensity. Each system is mounted on our mobile robot “YAMABICO”[5] (Fig. 11), and the orientation of the system was changed by rotating the robot. The experimental environment is shown in Fig. 12, the experimental results of System A and B are shown in Fig. 13 and 14, respectively. The sensors were put on the origin (0, 0).Fig. 11. System B mounted on our mobile robot “YAMABICO”. The right side is a transmit and receive circuit for one direction (70mm 163。 60mm), the left side is a high voltage power supplyfor 4 transmit and receive circuits (70mm 163。 72mm). Transducers are attached to the board directly, without horns.As shown in Fig. 13, System A detected only echoes from which the transducer lineofsight is perpendicular to the wall, because the intensity of echo signal is low in this system and the echo amplitude cannot exceed a threshold level when the echo is reflected out of transducer lineofsight. As a result, it seems this system has a narrow directivity. Also, the intensity of echoes bees smaller as the angle between the transducer lineofsight and the normal direction of the wall bees larger. Then, the echo amplitude exceeds later a threshold level. Consequently, the range data lay on the arc of a circle which was contact with the wall, and its center was out of walls.Fig. 12. Experimental environment. Sensors were put at the point 0.Compared with above, Fig. 14 indicates that System B could detect echoes in every direction, because the intensity of echo signal is large enough in this system. It can be seen from this figure that the directivity of System B is wide, since the range data lay on the arc of a circle with center at the sensor. Therefore, when a robot moves, obstacles can be detected even if they have no perpendicular faces to transducer lineofsight. Consequently, the ability to detect obstacles is improved in System B.V. ConclusionIt is concluded from the abovementioned results that:178。 Obstacle detectability varys with the individual sensor system.178。 The directivity of the sensor depends on not only directivity of the transducer butsensitivity of sensor.178。 The shape of the resultant sonar map changes drastically according to the characteristics of the sensor such as sensitivity, directivity and so on.178。 Understanding of the sonar map should be done with carefulness, because the shape of sonar map may be largely different form the real shape of the environment. If the sensing ability of robot is nearly equal to it of human, we can trust the robot. Unfortunately, almost current sensors are not so intelligent and the ability is limited. So, we must be careful in the presence of the robot.References[1] Polaroid Corp., Cambridge, Massachusetts 02139, Ultrasonic Ranging System.[2] . McKerrow and . Hallam: “An Introduction to the Physics of Echolocation,”Proceedings of the Third National Conference on Robotics of the Australian Robot Association, –209, Melbourne, June 1990.[3] Yoshiaki Nagashima and Shin’ich Yuta: “Ultrasonic Sensing for a Mobile Robot to Recognize an Environment –Measuring the Normal Direction of Walls–,” Proceedings of the 1992 IEEE/RSJ International Conference on Intelligent Robots and Systems, –812, Raleigh, NC, July 1992.[4] Minho Song and Shin’ichi Yuta: “Autonomous Mobile Robot Yamabico and Its Ultrasonic Range Finding Module,” ’89 Korean Automatic Control Conference, , –714, Seoul, October 1989.[5] Shin’ichi Yuta, Sho’ji Suzuki and Shigeki Iida: “Implementation of a Small Size Experimental Selfcontained Autonomous Robot –Sensors, Vehicle Control and Description of Sensor Based Behavior–,” R. Chatila et al. Eds, Experimental Robotics II (The 2nd International Symposium on Experimental Robotics, Toulouse, June 1991), SpringarVerlag, –359, 1993.Fig. 13. Resultant sonar map for System A.Fig. 14. Resultant sonar map for Sys
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