Line Tracking Car. Yi Lin& Zhenbin Zhu

Transcription

1 Line Tracking Car Yi Lin& Zhenbin Zhu Abstract The purpose of our project was to be able to build a line tracking robot. The model of the project would be composed of a microcontroller that the one used at this time was a PIC board, a tank, and the sensors used for determining the position of the tank. Basically, the main idea of the project was from the sensors. In other words, the sensor part would be most of the problems that might arise in this project. In terms of the side of sensors, we would be planning to use a line of sensor in front of the car. This line of sensor would have a number of cells. There were two types of cells being used. One was a sender cell and the other was a receiver cell, so these two forms a single pair of a sensor. For our project, we would use a pair of them in the line sensor in order to determine the position of the moving car. The way we transmit the information of the line tracking direction is to use a 555 timer in A-stable mode to generate different frequencies of the pulse to the tank. Then the tank will send the pulse to the controller. Eventually, we should have 4 different frequencies of the waves being generated by the 555 timer circuit and the pair of the sensors, so the decision of the changing direction can be made by the PIC board. To complete this project, the process of stages was as follows: (1) to assemble the components of the car the connection between the PIC board and the controller, and the line sensors with the 555 timer circuit and the tank would be done in this stage. (2) to generate the waves with four different frequencies in the output of the 555 timer circuit and to measure the output waveform in the controller--- In this stage, we should try to get four different frequencies of the waves with close to 50 duty cycle, and the four frequencies should be distinguishable to each other. (3) to program the four different frequencies of the waves This would make the tank have the determination toward the direction where it should go during the line tracking. (4) to actually test the ability of the line tracking of the car In this stage, the final model would be made. However, the corresponding difficulties in this project might be from the line tracking ability during intersection or 90 degree turn, the color contrast between the tape and the ground toward the sensitivity of the sensor, and the clearness of the wave received in the controller. Therefore, if all of the processes of the building stages were successfully completed and the possible difficulties were nicely treated, our project of the line tracking car should be perfectly performing the operation we assigned.

2 Introduction Basically, our idea is using the sensor and the 555timer, which is staying in front of the tank, to produce the different waves to determine which situation it is. Then transmit the wave to the controller to control the tank to move. Whenever a sensor move on the black tape, the sensor will be turned on and the transistor which is connecting to the sensors will be on. Then the current will pass through the the R2 main path and the branch that is controlled by the transistor. Then the resistance for R2 will be changed, so that the square wave output of the 555timer circuit will be changed. The controller receives the square wave in the earphone channel and it produces a sine wave and sends it to the broad. The broad will check the signal for the sine wave and determine which situation it is and send it back to the controller to control the tank move. Hence, the tank can follow the tape. Hardware The idea of a line following tank comes from the railroad and the track of the toy train. Once the train is off the track, it will terminally have no ability to be back on the track. Thus, the track or line following ability of an object is very important in our daily life. In this project, the track we used for the tank to be following is a rope of black tape. In this case, the Infrared light sensors are being used, so the color difference can be determined by the absorption of the receiver of the sensor. Eventually, it should be able to distinguish the color difference. However, the problem we have in this case might be the sensitivity of the sensor toward the materials of different types of the tape or the color contraction between the ground and the tape. For the first step, we built the 555 timer circuit in A-stable mode and connected the two sensors with the circuit. Basically, the circuit setup is pretty much the same as the picture shown below.

3 But, at this time we remain the only resistant R1 and separate the resistant R2 into 3 different paths. Each path has its own value of resistance. In addition, we placed one sensor on one of the paths and the other sensor on the one of the paths too. The circuit diagram of an individual is shown below. Thus, be given different colors to the sensor, the sensor will be automatically turned on and off. In this case, because the black tape is dark, the output of the sensor should have high voltage. Since the interior transistor has lower voltage in the base, the collector voltage of the interior transistor should have higher voltage. Once we know the dark color can make the output of the sensor have higher voltage and the bright color can make the output be lower voltage, we connect the output of the sensor to a transistor. This transistor is connected to one path so that the path can be open or close depending on the color difference. In order to generate four difference frequencies of square waves with close to 50 duty cycle in the output of the 555 timer circuit. The arrangement of the resistants R2 and the capacitor is shown below. After that, the output of the 555 timer circuit is connected to the tank. By doing so, the information of the signal will be transmitted to the controller of the tank by radio. Eventually, the signal we obtained in the controller is turned into Sin wave. Software In the soft ware side, we used the PIC board to measure the period of the Sin wave in the controller. The method to measure the period of the Sin wave is as follows.

4 Set voltage level=n Start Wait for the signal below the voltage level Yes---go to wait for the signal at or above the voltage level No---keep waiting until finish waiting Wait for the signal at or above the voltage level Start to time Yes---go to wait for the signal below the voltage level No---Keeping waiting Wait for the signal below the voltage level Yes---go to wait for the signal at or above the voltage level(finish) No---Keep waiting Finish---End time Display the period1 on the output Compare with period 2 If Period 1 is lower than Period 2

5 Yes--- turn left No---Compare with period 3 If Period is lower than period 3 Yes---go straight No---turn right Problem Solving ( Difficulties ): During the project, there are some of the difficulties for us. The 555 timer circuit is producing the square wave and propagating it from an earphone channel to the controller. At first, we used the 555timer to produce sound to the speaker, but the output signal that we can receive from the controller was in a very low voltage level and it has a lot of noise in it. Then, we transmit the square wave directly to the controller. After the wave transmitted to the controller, the wave has changed to the sine wave. We should add a 100M ohm between the high and low output and use the highest amplitude. Then, we can get the large signal on the oscillator and the noise has been reduced. Because the sine wave is made by the square wave which is made from the 555timer circuit, so the square wave should be close to 50% duty circle. If the duty circle is very large, then the sine wave will be very irregular. For the 90 degree turn, we will make the tank turn by the single motor. If it is going to turn left, the left motor will be turn off and the right motor will be turn on. In addition, there is a large obstacle for our project is the wave transmission will be lost when the controller is using to control the tank to move. It will make our tank move step by step as the wave is detected. Thus, there will be a propagation delay between the tank and the controller, so between each step it will stop and wait for the next wave coming. For the programming part, the difficulty is to test the period of the sine wave. The idea for it is to find the maximum value for the sine wave first, then find the minimum wave and start timing. After that, we find the second maximum and stop timing. Finally, display the period on the LED display. Then, we can use this period to determine the direction of the tank.