Desktop Line Following RobotRecentlymany kind of robot contests have being opened and some interestingreports of the challenge are found on the web. The Line Following isone of the robot contests to vie running speed on the line. I build atiny line following robot which can run on the desk. It is for only apersonal toy reduced its size to less than one fifth compared totypical line following robots, not in formula. But I believe that it issuitable for in-door use in the small Japanese houses said that rabbitburrow...(^_^;. Of course I have no time to appear the robot contests :- 　

About Line FollowerTheline follower is one of the self operating robot that follows a linethat drawn on the floor. The basic operations of the line following areas follows:

1. Capture line position with optical sensorsmounted at front end of the robot. Most are using several number ofphoto-reflectors, and some leading contestants are using an imagesensor for image processing. The line sensing process requires highresolution and high robustness.
2. Steer robot to track the linewith any steering mechanism. This is just a servo operation, any phasecompensation will be required to stabilize tracking motion by applyingdigital PID filter or any other servo algorithm.
3. Control speedaccording to the lane condition. Running speed is limited duringpassing a curve due to friction of the tire and the floor.

Thereare two line styles, white line on the black floor and black line onthe white floor. Most contest are adopting the first one in line widthof between 15 and 25 millimeters.

HardwareMechanicsRightimage shows bottom view and side view of the built line followingrobot. All mechanical and electrical parts are mounted on a protoboard, and it also constitutes the chassis.
The line following robotis upheld in three points of two driving wheels and a free wheel. Thedriving wheels are made with a 7 mm dia ball bearing and a rubber tire.The free wheel is a 5 mm dia ball bearing attached loosely. To drivedriving wheels, two tiny vibration motorsthat used for cellular phone, pager or any mobile equipment are used.Its shaft is pressed onto the tire with a spring plate, the outputtorque is transferred to the wheels.
The steering mechanism is realized in differential methodthat steer the robot by difference in rotation speed between the leftwheel and the right wheel. It does not require any additional actuator,only controlling the wheel speed will do.

ATmega8 is used for the controller and it is powered by a lithiumcoin cell. The other lithium coin cell is for only motors. Separatingthe power supply into two cells is to avoid accidental reset of themicrocontroller due to voltage dip by motor current. Sixphoto-reflectors are mounted at front end of the chassis. They sensereflection rate of the floor under them. Motors are driven in PWM tocontrol rotation speed linearly. The latest circuit diagram is here.
　
SoftwareUsing photo-reflectorsTodetect a line to be followed, most contestants are using two or morenumber of photo-reflectors. Its output current that proportional toreflection rate of the floor is converted to voltage with a resisterand tested it if the line is detected or not. However the thresholdvoltage cannot be fixed to any level because optical current by ambientlight is added to the output current like the image shown right.
Mostphoto-detecting modules for industrial use are using moderated light toavoid interference by the ambient light. The detected signal isfiltered with a band pass filter and disused signals are filtered out.Therefore only the moderated signal from the light emitter can bedetected. Of course the detector must not be saturated by ambientlight, this is effective when the detector is working in linear region.
Inthis project, pulsed light is used to cancel ambient light. This issuitable for arrayed sensors that scanned in sequence to avoidinterference from next sensor. The microcontroller starts to scan thesensor status, sample an output voltage, turn on LED and sample againthe output voltage. The difference between the two samples is theoptical current by LED, output voltage by the ambient light iscanceled. The other sensors are also scanned the same above in sequence.

Above image shows the actualline position vs detected line position in center value of 640. Themicrocontroller scans six sensors and calculates the line position byoutput ratio of two sensors near the line. Thus the line position canbe detected linearly with only six sensors. All the sensor outputs arecaptured as analog value that proportioning to reflection ratio, andthe sensitivity have variety between each one of them. In this system,to remove the variations from the outputs, calibration parameters foreach sensor can be held into non-volatile memory. This can be done withonline mode.

Tracking controlTheline position is compared to the center value to be tracked, theposition error is processed with Proportional/Integral/Differencefilters to generate steering command. The line following robot tracksthe line in PID control that the most popular algorithm for servocontrol.
The proportional term is the common process in the servosystem. It is only a gain amplifier without time dependent process. Thedifferential term is applied in order to improve the response todisturbance, and it also compensate phase lag at the controlled object.The D term will be required in most case to stabilize tracking motion.The I term is not used in this project from following reasons. The Iterm that boosts DC gain is applied in order to remove left offseterror, however, it often decrease servo stability due to its phase lag.The line following operation can ignore such tracking offset so thatthe I term is not required.
When any line sensing error has occurredfor a time due to getting out of line or end of line, the motors arestopped and the microcontroller enters sleep state of zero powerconsumption.

厉害啊  这么少的原件啊，我们去年参加的索尼杯也有个小车的题目，成本可以买一辆山地自行车啊  我们不得不承认日本的电子产业确实很强

对于这个篇文章，我们可以认可的的确很多，控制思想，方法，小车大小，元器件，以及技巧上的东西，都值得我们知道，虽然做到还很难，因为这必须以强大的电子产业做基础。

好!受益了!

我就看到15个元件，算上两块电池，17个
我简单看了一下原文，能看懂一些。
车体上面的两块是纽扣锂电池，很可能是ＳＯＮＹ的
另外旁边有个６ＰＩＮ的接口，因该是下载线接口；
车体下面，后部两个小直流电动机；据它说是手机上做振子用的电动机
车体下面，前部是６个红外反射对管。用差分控制。
车体下面，前部右侧是一个Ａｔｍｅｇａ８单片机，这个都知道吧；
车体下面，前部左侧是个拨动开关，不说了
车体下面，前部中间４个应该是驱动两个电机用的４个三极管。Ｈ驱动电路；
车体下面，中间那一个元件，瞅着就像个电容，应该是给电源滤波的；
三个车路，后面两个胶轮，前面用轴承做万向轮，
说完这个，原理图也就出来了，这样就能可靠运行，真的很不错。
后记：
ＡＴＭＥＧＡ８是用的内部晶振；
中间极性钽电容我认为是个很关键的元件，因为电机负载，对电源的污染比较厉害，而单片机对电源的平稳要求又比较高，没这个电容，很让人担心啊

日本仔的电器行业真的是很强大.....值得我们借鉴......取长补短.....总有一天我们会超越------"它"-------.

好东西啊,看来要要学的东西太多了

很好很高大

不怎么看得懂英文!