“The intelligent transportation system is the development trend of the future transportation system, and the intelligent vehicle plays a very important role in the intelligent transportation system. The author proposes that the intelligent tracking vehicle is an important part of the construction of 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, a vision-based intelligent tracking vehicle model design scheme is proposed. , as a solution to this hypothetical problem.
“
introduction
The intelligent transportation system is the development trend of the future transportation system, and the intelligent vehicle plays a very important role in the intelligent transportation system. The author proposes that the intelligent tracking vehicle is an important part of the construction of 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, a vision-based intelligent tracking vehicle model design scheme is proposed. , as a solution to this hypothetical problem.
The vision-based intelligent tracking car model design scheme can use vision to track and move forward autonomously and graded and precise steering when the line is complex and the turning radius is uncertain.
1. Overall system design
The vision-based intelligent tracking car model system takes the AVR single-chip MEGA16 as the core, and is composed of a single-chip microcomputer module, a path recognition module, a DC motor drive module, and a steering gear drive module, 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 car model uses vision to independently track and move forward on the runway, and grades and turns accurately. The road is a 318 mm wide white base plate with an 18 mm wide black tape in the middle with changing line patterns.
2. Hardware design
2.1 Control module
The tracking car model adopts the ATMEGAl6 of the AVR core. The chip can work independently without external crystal oscillator and reset circuit, which is very suitable for the requirements of intelligent tracing car model. The controller module is installed on the Leisu Deng 1:24 competition-level remote control car model produced by Guangdong Audi Toys Industrial Co., Ltd.
2.2 Path recognition module
The reflective photoelectric sensor is used to distinguish black and white on the runway. The reflective photoelectric sensor has a light emitting end and a light receiving end. The white background and the black line have different reflections on the light emitted by the transmitting end, thus affecting the voltage generated by the receiving end. The sensor module is composed of a reflective photoelectric sensor, an adjustable resistor and an operational amplifier LM324, as shown in Figure 2. It can output high and low levels on different tracks and track independently.
2.3 Steering motor and drive motor drive module
The H-bridge circuit is used to drive the front wheel steering motor and the 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 steering motor drive circuit is shown in Figure 3. Among them, the front wheel steering motor control scheme is graded steering control, and the rear wheel drive motor control scheme is also open-loop control.
2.4 Hierarchical Steering Module
In order to achieve precise steering at different angles at different turning radii, a graded steering circuit is designed, as shown in Figure 3. The resistance value of the variable resistor in the steering gear of the car model is 1.8-4.2 kΩ, and 1 is connected to the A/D pin of the single-chip microcomputer. The voltage V is the on-chip stable reference voltage, and it can be seen that:
Taking the No. 1 sensor as an example, the calculation of the graded steering angle is explained.
The installation of the sensor module is shown in Figure 4. All dimensions have been designed and calculated in the early stage. Point D is the steering center of the adjustable resistance of the front wheel steering gear, and point A is the steering center of the car. When the No. 1 sensor detects the black line, the steering angle of the front wheel and the steering angle of the variable resistance in the front wheel steering gear corresponding to the steering angle of the front wheel are calculated as:
The value of V3 is linearly proportional to the variable resistance angle α1 in the front wheel steering gear. Therefore, different sensor detection positions can calculate different ideal front wheel steering angles and different ideal steering A/D voltages. V3 is measured by a single-chip microcomputer, You can convert the variable resistance steering angle a1 in the front wheel steering gear, and compare it with the ideal steering A/D voltage. When V3 reaches the ideal steering A/D voltage, the single-chip microcomputer controls the steering gear to a low level, the steering gear stops and keeps Steering to achieve precise graded steering.
3. Software design
3.1 Main program design
Use C language to program and debug under the ICC-AVR development environment. The main program flow chart is shown in Figure 5.
3.2 Program Design of Hierarchical Modules
ATMEGAl6 can sample 8 single-ended input voltages from port A. When the REFSl and REFS0 of the ADC multi-function register ADMUX in the chip are set to 1, VAREF=2.56 V, which is the stable reference voltage source on the chip, that is, the voltage V in Figure 3. The steering limit of the intelligent tracking vehicle is ±30°. Table 1 shows the corresponding calculation data of the graded accurate steering of the five photoelectric sensors.
4. Conclusion
The vision-based intelligent tracking car model design scheme can use vision to track and move forward autonomously and graded and precise steering when the line is complex and the turning radius is uncertain. For the impact of ambient light, consider adding a filter circuit and optimizing the control algorithm to increase its anti-interference ability. Experiments show that this scheme has a good tracking effect.
The Links: QM150DY-2HBK NT156WHM-N32