1 Introduction
Robot competition is a kind of confrontation activity that has been rapidly developed in recent years. It involves artificial intelligence, machinery, electronics, sensors, precision machinery and many other fields. Through the competition, students can develop their innovative consciousness, hands-on ability, team writing ability and so on. Among them, the fire fighting competition is one of the most extensive and influential robot competitions.
The rules of the game are to simulate the firefighting of firemen in life. The robot starts from point H, looks for any candles placed in four rooms, and tries to destroy them. The walls of the competition venue are 33cm high and are made of wood and black in color. The dimensions are shown in Figure 1. For the game, the lower the score, the better. In addition, depending on the mode selected, the corresponding factor is multiplied when scoring.
2 system hardware design
2.1 overall system design
The system is based on the ATmega32 microcontroller, which is an 8-bit microcontroller with low power consumption based on enhanced RISC architecture. Its features are: 1K with 32K bytes of programmable Flash; 2K bytes of on-chip SRAM data memory; 1024 bytes of on-chip programmable EEPROM data memory. 2 slices contain the JTAG interface. 3 peripheral interface. Two 8-bit timer/counters with separate, preconfigurable prescalers; one 16-bit timer/counter; four-channel PWM outputs; eight 10-bit ADCs; 32 programmable I/Os mouth. 4 low power consumption, the maximum operating frequency is 16MHz.
According to the rules of the fire fighting competition, it is equipped with a collision sensor, a gray sensor, a flame sensor and an infrared sensor. Two motors are controlled by two PWMs to drive the fire extinguishing robot, and the other fire extinguishing motor is directly driven by the I/O port through the photocoupler.
2.2 system power section
When the system adopts a single power supply circuit, it is relatively simple, but considering the large current at the moment of starting the motor, the power supply voltage is unstable, which affects the stability and reliability of the operation of the single chip and the input circuit. Therefore, a dual power supply scheme is adopted. The motor power supply is completely isolated from the microcontroller power supply. The microcontroller and sensor circuit are powered by 8V, and the motor is powered by 12V. Increasing the supply voltage of the motor can increase the speed of the robot and thus improve the performance of the fire.
2.3 motor drive part
The robot needs to be controlled to drive at a suitable speed. In the process of extinguishing the fire, it is necessary to find the fire source at a faster speed, and to prevent the performance of the game from being affected by the collision. The speed of the car is controlled by two DC motors. The L298 driver chip is one of the small DC motor driver chips with superior performance. It can be used to drive two DC motors or bipolar stepper motors. At a voltage of 6-46V, a rated current of 2A can be supplied. The L298 also has an overheating auto-shutdown function and feedback current detection. In order to ensure the normal operation of the L298, it is recommended to install an off-chip freewheeling diode. The two-way PWM driver L298N is directly output by the ATmega32 microcontroller. By adjusting the duty cycle of the PWM modulation pulse, precise speed regulation can be achieved. The pulse frequency has an effect on the motor speed, the pulse frequency is high in continuity, but the load capacity is poor; the pulse frequency is low. The direction of rotation of the motor is controlled by two I/O lines of PD2 and PD3.
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