Abstract—This paper introduces the design of the autonomous tracing intelligent vehicle。 The software and hardware design method which realizes the autonomous tracing using the infrared reflective photoelectric sensors as the path recognition module is researched。 The system employs Freescale HCS series 16 bit single-chip microcomputer MC9SDG128 as its main controller and an array of photoelectric sensors for recognizing the path information。 Single-Chip Microcomputer energizes the servo to steer and control the speed of the DC electric motor according to the analysis of the path and speed information that from sensors。 Consequently this intelligent vehicle can track the black-guide- line automatically and move forward following the line quickly and smoothly。 The autonomous tracing principle of photoelectric sensor is presented。 The effect of sensors overall arrangement and space on the autonomous trace is discussed。84528

Keywords-photoelectric sensor; intelligent vehicle; autonomous tracing; path recognition and control

I。INTRODUCTION

Intelligent vehicle, wheel mobile robot, is an integrated intelligent system that has the function of environmental perception, path plan and automatic traffic。 As a high-tech production, the intelligent vehicle comply the automatic control, pattern recognition, sensor technology, automotive electronics, electrical, computer, machinery and many other subjects [1]。 With the development of automation, computer and information technology, smart cars has played a very important role in the industry and daily life。 Such as the lunar rover for space exploration, the handling robot in library or workshop and so on。 In recent years, smart car is used widely in the roads, logistics and flexible manufacturing systems and has become hot in the field of artificial intelligence research。

At present, the research of intelligent vehicle has been able to provide the driver assistance as well as unmanned driver in some marked road。 Normally the vehicle identifies the specific road marks and simulates the manual drive by reason。 The intelligent vehicle presented in this paper is an automatic guided vehicle and able to move automatically along the tracks in a given region。 The vehicle motion is controlled by direction and motor drive。 A black line different from the white ground is employed to guide mark。 The infrared reflective photocell is used to identify the black line and completes the trace in the shortest time。 The photoelectric sensor group is scanned by a single chip microcomputer。 The move direction can be reached

by analyzing the sensors signal and logical arithmetic。 The intelligent vehicle changes the direction by steering gear with long arm drive the front wheel。 The DC motors are employed to drive the intelligent vehicle and the velocity is adjusted by pulse wide modulate (PWM)。 In order to fast, smooth run, the intelligent vehicle must combine the path identification, servo motor and the DC motor control accurately。 This paper introduced the intelligent vehicle trace, obstacle avoidance and speed control。

II。THE TRACING PRINCIPLE OF INFRARED PHOTOELECTRIC SENSOR

By the detection mode, the photoelectric sensor is usually pided into radio-type and reflection type。 Reflective photoelectric sensor has a variety of light sources, such as infrared light-emitting diode, normal light emitting diode and laser diode。 The infrared light-emitting diode and normal light emitting diode are easily interfered by other light resources。 However the laser diode is not easy interfered because it launches the narrow frequency light and the sensor only receives a very narrow frequency range signal。 It is a pity that the laser diode sensor price is more expensive。 More uncertain factors, such as reflective surface shape, color, smooth finish, sunlight and so on, will affect the infrared reflective photoelectric sensor operation。 Therefore in order to improve system reliability and accuracy, the transmission single is usually sent to the infrared emitting diode by modulation and the photodiodes receive the modulated infrared signal。 The output signal voltage (Vout) reached by converting the received reflected light intensity is the function of the distance X between the reflector and the sensor。 When the reflector material is the same, the response curve of X and Vout is nonlinear [2][3] DŽAs shown in figure 1, suppose the output voltage reaches a certain threshold as the target, the threshold voltage of different target distance is different。