【正文】 ctric sensors is , the maximum speed is the flow chart of the stable operation system. The location of a smart car is determined by the feedback value of photoelectric sensors. The analog signal values of photoelectric sensors which have detected black line are transformed into digital signal values. The values are between 0 and 255. Then the smart car system makes a judgment to determine which sensor value is less than 80. The lesser values show that the sensors have detected the location of the black line. Then its mark bit is set into 0 in C++ program. And the CPU calculates the coordinates according to the mark bit. The smart car system will send the 4 corresponding PWM pulse to the steering gear and get a required angle for the smart car according to the coordinates. For example, if , 1, 2, 7, 8, 9 sensors detect the black line, we can conclude that the smart car will deviate from the straight trajectory. The smart car system will make the smart car decelerate early and give the required speed and angle while the smart car is moving along the curvy trajectory. When , 5 sensors detect the black line, it can be claimed that the smart car is moving along the straight trajectory. Therefore the smart car will speed up. Figure 3. Tracking control algorithm flow chart C. Smart Car Tracking Control Algorithm 1) Straight Trajectory Control Algorithm: Running in a straight line is a basic and important requirement for a smart car. In this case the smart car can achieve the maximum speed and the maximum acceleration. The maximum speed is about 9m/s10m/s or faster. The straight line algorithm can be implemented as the cesures depicted in Figure 4. The smart car system determines the straight control algorithm according to the path information which is detected by the photoelectric sensors and calls the appropriate procedure to control the motor speed and the steering angle. 2) Curvy Trajectory and Stype Trajectory Control Algorithms: When the smart car system detects the curvy trajectory, it ran under the manner that takes the shortcut. In other words the smart car moves along the inner of the trajectory rather than followes the trajectory. 5 Figure 4. Straight trajectory control strategy When the central point is deflective, the smart car will appear deflective phenomenon. The smart car system laid the foundation for taking the near way in the curvy trajectory. After the smart car system records the information of the first circle, it can distinguish the next corner information directly and turn left or right while the smart car is running in the second circle. Then it can cross the curvy trajectory according to a smaller radius, reduce the distance and save the time. Figure 5 is the control strategy for the curvy trajectory. Figure 5. Curvy trajectory control strategy While the smart car is moving along the Stype trajectory, if the speed can not be controlled effectively, it may run out of the runway. Figure 6 and Figure 7 show the Stype control strategy. The smart car system records the digital signal values of the AD module and pares with the number 255, if the values of sensors of the right are less than 255, set A1=1。Email: Abstract—In this paper, target identification and trajectory technology are analyzed. The tracking control algorithm based on the photoelectric sensors is proposed. The algorithm utilizes the errors of the location and the signal of route as input parameters, to regulate the output angle of the steering gear. The smart car system includes the straight trajectory control algorithm, the curvy trajectory control algorithm and the Stype trajectory control algorithm according to the different characteristic of the trajectories. The experiment shows that, by using the proposed algorithm, the smart car can move smoothly along the straight trajectory, the curvy trajectory and the Stype trajectory with satisfied accuracy. Index Terms—photoelectric sensor, black trajectory, smart car I. INTRODUCTION A smart car system is posed of the power supply module, the sensor module, the Direct Current (DC) driving motor module, the p