超声波测距，测量精度为1cm，可以使机器人安全避障。-Ultrasonic distance measurement accuracy of 1cm, can make the robot obstacle avoidance safety.

一个关于小车循迹，转弯，画圆和避障的源代码，非常实用。-About a car tracking, turn, draw circles and obstacle avoidance of the source code, very practical.