Design of intelligent rescue robot car based on single chip microcomputer

0 Introduction
In recent years, earthquake disasters have occurred frequently. The most harmful ones are the Wenchuan earthquake in China in 2008 and the Japan earthquake this year. During this period, there are countless earthquakes with less harmful effects around the world. These earthquakes have brought people tragic casualties and huge economic losses. We cannot prevent earthquake events from happening, but there are still many things we can do, among which the rescue of the wounded is an important task.
Of course, the post-disaster environment is complicated, which is a challenge to the requirements of rescue tools, and the detection of life after the disaster is also a very important issue. Based on these two points, we designed a simple intelligent rescue robot car, and achieved good results through on-site demonstration.

1 Overall framework of the intelligent car
The overall framework can be divided into three parts: environmental image acquisition part, motor drive part and central data processing part. The system block diagram is shown in Figure 1.

2 Control module
The most important part of the intelligent rescue vehicle is its brain - the central processing system. It is not only responsible for processing the image data sent by the environmental image acquisition part, but also for converting this information into the driving control signal of the motor, so that the whole vehicle moves forward according to the predetermined rules, and at the same time, it also controls some other auxiliary equipment. These can be achieved by general single-chip microcomputers, but for the rescue vehicle driving in a complex environment, one thing is very important, that is, strong anti-interference ability to the outside world, so we choose Microchip's 8-bit microcontroller PIC. In addition to the strong anti-interference ability just mentioned, this controller also has the advantages of fast speed and good portability. [page]

3 Power module
The rescue vehicle is powered by a rechargeable battery. Since the operating voltages of the microcontroller, camera and motor are different, we prepared two solutions: one is to use analog circuits for voltage stabilization; the other is to use a dedicated integrated voltage stabilization chip. Through actual operation and comparison, the second solution was finally selected. Its main advantages are: a. The peripheral circuit is simple, and only simple filtering is required; b. It can provide a stable output voltage; c. It is simple to make and low cost. The power supply system block diagram is shown in Figure 2.

Since the camera needs a voltage of 9 to 12V to work properly, and the voltage of the rechargeable battery is only 6 to 7.2V. Therefore, a DC-DC boost circuit becomes necessary. The DC-DC voltage conversion uses the MC34063A integrated circuit, which integrates a temperature compensator, a comparator, a dynamic current band-limited duty cycle controllable oscillator and a high current output driver.

4 Motor drive module
The two motors that drive the robot to walk require different speeds to achieve turning. The selected driver chip is L293D, which contains 4 output channels, with a maximum output peak current of 12A, and can drive two DC motors to work at the same time; its signal input and enable terminals receive signals from the microcontroller to control the on and off of the motor and the forward and reverse rotation, and can also adjust the motor
speed (PWM mode) by inputting square wave signals with different duty cycles to the enable terminal. As shown in Figure 3, the IN port is connected to the control signal, the OUT port is connected to the two ends of the motor, and the EN port is connected to the enable signal. When a group of IN port inputs are high/low or low/high levels, the forward/reverse rotation of the motor can be achieved. When a group of IN port inputs are all high or low level, the motor will stop. When the EN enable terminal is high level, the corresponding port input signal is valid; otherwise, the input signal is invalid. By inputting PWM wave at the EN terminal and adjusting the duty cycle of the PWM wave, the motor can be steplessly adjusted.

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5 Obstacle crossing part
Obstacle crossing is undoubtedly the outstanding feature of this intelligent rescue robot. Traditional rescue robots focus on how to rescue, but ignore the dangers of the road, which makes the rescue robot go but never return. We fully realize this and have made considerable improvements in the obstacle crossing part. Three wheels are meshed through gears to form a large wheel. When the ultrasonic module detects an obstacle, the entire large wheel flips over, allowing it to smoothly cross the obstacle and reach the destination, as shown in Figure 4.

6 On-site acquisition part
The rescue site environment is complex and there are many potential dangers. Rescuers may find it difficult to enter, but they must accurately grasp the environment of the site to create favorable conditions for rescue work. The above problems are well solved by high-definition cameras. In order to achieve multi-directional shooting of the scene, the servo is used to control its rotation angle, and the reduction motor controls its lifting. Then, the picture is sent to the host computer interface through the wireless video transmission module for the reference of rescuers.

7 Life detection module
The life detection module is also an indispensable part of the rescue robot, because in order to rescue the wounded, the position of the wounded must be detected first, which requires a life detection module.
BISS0001 is a high-performance sensor signal processing integrated circuit. The static current is extremely small, and a passive pyroelectric infrared sensor can be formed with a pyroelectric infrared sensor and a small number of peripheral components. The schematic diagram is shown in Figure 5.

8 Conclusion
Based on the single chip microcomputer, we designed a simple robot rescue vehicle. Through the demonstration, our design has certain value and practicality.