说明：  本系统主要是设计一个简单的比例放大器，使小车能以指定的速度运动。采用“自下而上”，“分层”建模思想而设计的。主要包括了理论分析与设计、仿真系统的创建、仿真结果、仿真操作说明、结论等五部分。使用Matlab7.1实现
(This system is mainly to design a simple proportional amplifier, so the car can be specified speed of movement. " Bottom up" and " layered" modeling idea. Include theoretical analysis and design, the creation of the simulation system, the simulation results, simulation instructions, conclusions of five parts.)