Design of Intelligent Tracking Vehicle Model System Based on ATmegal6 Single Chip Microcomputer and Hierarchical Steering Module

introductionIntelligent transportation system is the development trend of transportation system in the future. Intelligent vehicle plays a very important role in intelligent transportation system. The author puts forward the intelligent tracking vehicle as an important part of building the future intelligent transportation system. Aiming at the autonomous tracking problem of the intelligent vehicle under the assumption that the future transportation system has a navigation line, the author puts forward a vision based intelligent tracking vehicle model design scheme as the solution to the hypothetical problem.The design scheme of intelligent tracking vehicle model based on vision can make use of vision to independently track forward, grade and accurately turn when the on-line type is complex and the turning radius is uncertain.

1. Overall system designThe intelligent tracking vehicle model system based on vision takes AVR MCU mega16 as the core, and is composed of MCU module, path recognition module, DC motor drive module, steering gear drive module, etc., as shown in Figure 1.The DC motor is the driving device of the vehicle, and the steering motor is used to control the driving direction of the vehicle. The intelligent tracking vehicle model makes use of vision to independently track and advance on the runway and turn accurately in grades. The road is a 318 mm wide white base plate with 18 mm wide black tape with changing line type.

2. Hardware design2.1 control moduleThe tracing car model adopts ATmegal6 with AVR core. The chip can work independently without peripheral crystal oscillator and reset circuit, which is very suitable for the requirements of intelligent tracking vehicle model. The controller module is installed on the leisuden 1:24 competition level remote control model produced by Guangdong Audi toy industry Co., Ltd.

2.2 path identification moduleThe reflective photoelectric sensor is used to distinguish black and white on the runway. The reflective photoelectric sensor has light transmitting end and light receiving end. The reflectance of the light emitted by the white background and black line to the transmitting end is different, which affects the voltage generated by the receiving end. The sensor module is composed of reflective photoelectric sensor, adjustable resistance and operational amplifier LM324, as shown in Figure 2. Realize the output of high and low levels on different tracks and independent tracking.2.3 steering motor and drive module

The H-bridge circuit is used to drive the front wheel steering motor and rear wheel drive motor of the intelligent tracking vehicle to realize the functions of left and right steering, forward, backward, acceleration and deceleration of the intelligent tracking vehicle. The driving circuit of steering motor is shown in Figure 3. The front wheel steering motor control scheme is hierarchical steering control, and the rear wheel drive motor control scheme is also open-loop control.2.4 staged steering moduleIn order to achieve accurate steering at different angles at different turning radii, a hierarchical steering circuit is designed, as shown in Figure 3. The variable resistance in the model steering gear is 1.8 4.2 K , which is connected to the A / D pin of single chip microcomputer. Voltage V is the on-chip stable reference voltage, and it can be seen that:

Take sensor 1 as an example to illustrate the calculation of hierarchical steering angle.The installation of sensor module is shown in Figure 4. All dimensions are calculated through preliminary design. Point D is the steering center of adjustable resistance of front wheel steering gear and point a is the steering center of trolley. When sensor 1 detects the black line, the front wheel steering angle and the variable resistance steering angle in the front wheel steering gear corresponding to the front wheel steering angle are calculated as:

The V3 value is linearly proportional to the variable resistance angle in the front wheel steering gear 1. Therefore, different ideal front wheel steering angles and different ideal steering a / D voltages can be calculated at different sensor detection positions. The variable resistance steering angle A1 in the front wheel steering gear can be converted by measuring V3 through the single chip microcomputer, and compared with the ideal steering a / D voltage. When V3 reaches the ideal steering a / D voltage, the single chip microcomputer controls the low level of the steering gear and the steering gear stops, Maintain steering for accurate graded steering.

3. Software design3.1 main program designC language is used for programming and debugging in icc-avr development environment. The main program flow chart is shown in Figure 5.

3.2 program design of hierarchical moduleATmegal6 can sample 8 single ended input voltages from Port A. When refsl and refs0 of the on-chip ADC multifunction register admux are set to 1, varef = 2.56 V, which is the on-chip stable reference voltage source, that is, the voltage V in Figure 3. The steering limit of intelligent tracking vehicle is 30 , and table 1 shows the corresponding calculation data of graded accurate steering of five photoelectric sensors.4. Conclusion

The design scheme of intelligent tracking vehicle model based on vision can make use of vision to independently track forward, grade and accurately turn when the on-line type is complex and the turning radius is uncertain. For the influence of ambient light, we can consider adding filter circuit and optimizing control algorithm to increase its anti-interference ability. Experiments show that the scheme has good tracking effect.