作者简介：王倩，女，1976年7月出生，师从于成都理工大学李宏穆教授，
2009年6月毕业于成都理工大学测试计量技术及仪器专业，于2009年6月获硕士学位。
摘要
无人驾驶汽车作为现代高科技与汽车技术相结合的产物，是汽车工业今后发展的主流方向。它主要是利用车载传感器、全球定位系统、激光扫描仪、雷达等监控技术感知周围环境信息、车辆位置和障碍物信息，传入车内计算机系统加以分析、辨识、判断，用以控制车辆改变行驶状态，从而使车辆能安全、准确地在道路上行驶。自上世纪七十年代国外就已经开始研发此类产品，目前已初步迈入实用化阶段，但现今的主要研究方向着重于高速公路环境与城市环境的无人驾驶汽车研发，对特殊环境下使用的无人驾驶汽车关注不够。
而本次设计的无人驾驶观光车是应用于野生动物园这一特殊单一环境的。由于野生动物园园区面积大，观光路线长，动物为区域自由放养，要求游人步行或骑车游览不太现实，一般都采用观光车搭载游人观光。考虑到野生动物园路况相对较好，没有其它车辆与行人的干扰，行驶中车辆速度缓慢（约为7KM/h），无须多级变速，自动观光车也无需实现过多的功能，其无人驾驶技术要求并不高，造价相对低廉，有较高的开发应用价值。
由于园区道路的坡度起伏不大，一般不会出现路障，观光车几乎无须急停或频繁起动，也不需快速启动、瞬间加速、负载爬坡，因此也就没有较大的瞬时功率、快速的动态响应等要求。而永磁无刷直流电机功率密度大、效率高，加之体积小、惯性低、响应快，非常适用于电动汽车的驱动系统。而考虑到园区路面平坦，行使路线较短，车辆行驶速度均匀而缓慢，几乎为额定负载行驶，因此使用两个600w无刷直流电机以双前轮轴驱驱动方式驱动车轮，这样机械结构简单，重量轻，价格低廉、易于维护。
此外自动观光车是一种自动寻迹汽车，坐满乘客后能沿一闭合环线自动循环行进，行进路线上设定3-5个停车观光点，自动观光车到点能自动停车。此外野生动物园作为一种半开放园区，或许会有动物偶然出现于道路上，所以自
动观光车还应具有遇障停车的功能。因此，采用目前最新的低功耗、速度高、片内硬件资源丰富的高性价比的单片机系列AVR的ATMEGA16单片机作为该观光车的控制系统。作为目前最新的单片机系列之一，它尤其适用于电池供电、便携式以及电机驱动等系统。
本文设计采用在车辆座位下方安装一弹簧触点开关，在车辆底部安装3个扩散反射型红外线传感器，另外在前车尾端设置一组红外线发射器，后车前端设置对应的一组红外线接收器以及2个超声波传感器。
同时由于是若干辆无人驾驶自动观光车在园区沿一封闭路线依次循环前行，所以需要在路面中央沿行
进路线铺设一条黑线条，用于车辆寻轨。在定点停车处铺设一条与路中央黑线条垂直成900的黑停车线。
当观光车上乘坐有游客后，座椅下的弹簧触点开关被触发，单片机接收到触点开关输入的信号，控制电机启动，车辆运行。运行过程中，单片机不断读取3个寻迹红外线传感器的状态信号，控制两个电机以高、低两级不同的速度运转，使观光车不断左右转向以修正路线，始终能沿路面黑线条前进。
同时单片机还不断读取长距离超声波测距传感器和前车障碍判断红外线传感器的状态信号，当超声波传感器检测到前方障碍，而红外线传感器没有检测到前车发出的红外线信号，单片机则将前方障碍判定为动物，立刻控制电机停转，观光车远距离停车；若超声波传感器检测到前方障碍，而红外线传感器也检测到前车发出的红外线信号，单片机则将前方障碍判定为车辆，则控制电机由高速转为低速，当与前车距离小于某一定值后，单片机才会控制电机停转，观光车近距离停车。
而当观光车到达停车点以后，遇见路面上的黑停车线，3个寻迹红外传感器状态同时变化，单片机控制车辆停止运行，游客下车游玩。若停车点已经停有车辆，则由于前方有车，观光车尚未到达停车点也会依次排队停车等候。当前方车辆依序前移，而本车尚未乘坐游客，则由单片机控制车辆以低速前移，直至与前车的距离小于一定值后停行或遇停车线停行。而当本车坐满游客后，检测到前方没有障碍后，忽略停车线，车辆前进。
考虑到观光车是采用电池驱动，且车速缓慢，没有外力撞击危险，从节省能耗、提高行驶里程的角度出发，要求车身重量越轻越好，最佳方法就是合理选取汽车外壳的材料。虽然现今铝合金材料与各种复合材料已经被大量应用，但价格过于高昂，为了在保证使用安全的前提下尽可能降低成本，因此采用工程塑料制作车身外壳。
作为观光用车，要求其外形应该既有亲和力又有现代感，所以采用流线造型，曲线柔和，尽可能取消复杂的形态设计，既利于加工制造、降低成本，又显得简洁大方。车身高度尽可能降低，既能降低车辆重心，使其行驶平稳，又显得造型
美观舒展。此外为扩大视野、减轻车重，取消了车窗设计。由于车辆载重设定为4人，采用前后双排长条座位，以压缩车身尺寸。为无人驾驶，所以观光车无须设计方向盘，但安装有一透明遮阳顶棚。
此外，无人驾驶自动观光车所处的是一个自然环境，四周彩丰富多样，但大多为低纯度的自然。因此，观光车的主调选用明度高、纯度低的各序列灰粉宝石蓝系，使观光车易于辨识，又不会过于明艳，以免对园区动物产生刺激。
关键词：电动汽车 无人驾驶 传感器 单片机
Wildlife Park Unmanned Sightseeing Vehicles
Designing Application
Introduction of the author: Wangqian, female, w as born in July, 1976.whose tutor was Professor Li Hongmu . He graduated from Chengdu University of Technology in test measurement tec h nology and instruments major and was granted the Master Degree in June, 2009.
Abstract
Unmanned car, as the combination of modern high-technology and car technology, is the mainstream of the future car industry. Generally speaking, it utilizes certain supervising technology such as vehicle-mounted sensor，global positioning system，laser scanner and radar to perceive the information such as surrounding environment, position of the car, obstacles in the way. After analyzing, classifying and judging, the information can serve to direct the driving of the car, making it move safely, correctly on the road. Research about this kind of products has begun abroad since 1970’s and now has come to practical usage. However, today’s research about unmanned car focus more on the exploration of the one that drives on express high way or in city environment but less on that in some particular situations.
This new designed unmanned touring car is specially applied to wild animal zoos. With large space, l
ong touring route and freely-raised animals in it, tourists are seldom required to visit the zoo by foot or cycling but using a touring car. What’s more, without any other vehicles and passengers, the road condition is comparatively better and cars there drive slowly (about 7km/h) and steadily for viewing. Thus, auto-touring cars have no need to function in many aspects and no high driving technique is required. In short, their costs are low but worthwhile to be explored.
Given that roads in the zoo undulate little and obstacles are few, touring cars even do not have to be stopped suddenly or started frequently. Above that, few instant starts, sudden accelerations or climbing with certain weight are needed and it requires no high Instantaneous power，no quick dynamic response, etc. As indicated, BLDCM suits the driving system of the electric-powered car most as it is featured by its big power density, high efficiency, quick response, small inertia and volume.
Considering that roads in the zoo are also flat and short, cars there always drive slowly and steadily even just like driving with rated load。So, to use two 600w BLDCM to start the car in the way of double-front wheel Shaft drive can make our starting machine simple, light, cheap and easy to be maintained.
Apart from that, the auto-touring car is a kind of spot-detecting cars. It can take
its passengers circling automatically along a closed route and stop when it reaches to the parking spots which are designed beforehand. In the wild animal zoo, there may be some animals appearing suddenly in the way, so the car should also have the ability to stop whenever it meets obstacles. Accordingly, to adopt the most advanced, low-exhausting, high speed, Chip hardware resource-rich, high performance-price ratio ATMEGA16 microcontroller from A VR series as the control system of this touring car is the best choice. Ranked as the most advanced series of microcontroller，it is particularly designed for battery-powered, portable and motor-started.
These designs indicate that we can install a spring contact switch under the seat and diffuse reflection type infrared sensor under the base of the car. Besides, another two sets of infrared sensors are fixed in the tail of the proceeding car and at the head of the following car a set of infrared receiver and two ultrasonic sensors are added.
Meanwhile, as the cars are orderly circling the route, it’s better to lay a black line in the middle of the route which can help the car to detect and stop automatically at the parking spots which are marked by another black line vertical to the straight one.
When the passengers get on the car, the spring switch under the seat is on and the signal is delivere
d to the microcontroller which directs the car to start and function. During the driving, the microcontroller keeps on reading the 3 signals from the infrared sensor to alternate the speed, making the touring-car turning left or right to follow the route and keep along with the black line all the time.
At the same time, the microcontroller continually reads out the signals from the long-distance ultrasonic distance measurement sensor and the obstacle-detecting infrared sensor in the proceeding car. When the ultrasonic distance measurement sensor find out obstacles but infrared sensor receives no infra-red signal from the proceeding car, the microcontroller then take the obstacle as an animal and immediately make the car stop at a long distance. When the infrared sensors receives signals, the microcontroller then take it as a car and turn to the low speed until the distance from the proceeding car reaches to the limited one. After that, it stops the car nearby.
When the car arrives at the parking spot and meets the horizontal black line, all the 3 spotting infrared sensor act together. Then the microcontroller makes the car stop to let the passengers down. Sometimes other parking cars may be there, and then it will stop to wait for a position. After the parking cars move away, they go forward. If there are no passengers, the microcontroller will make the car move slowly until it gets to the horizontal line or meet the distance limit with the procee
无人驾驶汽车价格ding car; if passengers are all on, it will neglect the line and move forward after no obstacles are found.
The touring cars are powered by battery, and they move slowly with no danger of being crashed by other force. Thus, in order to save the energy and continue a longer
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