Research And Implementation Of The Key Technique For Portable Electronic Whiteboard

The Electronic Whiteboard, which has been collected the state- of-art electronic technology, the software technology and many kinds of other high tech method research and development and so on, is a high-tech product. It uses the electromagnetic induction or ultrasonic principle, the infrared orientation technology, unifying of the computers and projecting apparatus may realize paperless work and teaching. The Electronic Whiteboard may replace the ordinary blackboard in the classroom instruction to carry on operation, writing, drawing, cleaning and so on, but also may apply it to pull the screen, the searchlight, photographs and so on the special effect and the application skill vividly causes the classroom to be interesting. The Electronic Whiteboard, besides in the classroom instruction application, in the other work, design, training and so on also has a more widespread application of space. But most of the existing whiteboard products are too heavy and bulky to carry, and transport and installation are inconvenient.This dissertation obtains the Jilin Province science and techno- logy development plan project'Characteristic Product Development of Digitized Electronic Whiteboard based on Infrared Laser Technology'(No.20040303) subsidization, studies the portable Electronic Whiteboard the key technology and its research and design implementation.In the existing Electronic Whiteboard products, the wireless orientation Electronic Whiteboard which controls based on the pressure, based on the electromagnetic induction wireless orientation Electronic Whiteboard , all relies on the infrared wireless orientation Electronic Whiteboard as well as based on the CCD scanning wireless orientation Electronic Whiteboard in the very great degree the whiteboard pan material structure perhaps fixedly installs on the pan the infrared tube array perhaps the CCD scanning component, these kinds of whiteboard then take along are impossible to realize; But is not big based on the ultrasonic orientation Electronic Whiteboard to the plate dependence, moreover the receiver design is also quite flexible, thereby this dissertation selects the ultrasonic orientation technology to study the portable Electronic Whiteboard design and implementation.This dissertation to the portable Electronic Whiteboard receiver hypothesis for the slanting length of side is a 8cm isosceles right triangle module, this will undoubtedly increase the positioning accuracy of the system requirements, if still using the traditional pulse take along the method on to be very difficult to guarantee the precision. Thus to locates the theory in this dissertation the research as well as to delay the choice of extraction method on the system become the system research key points and the difficulties.In this dissertation, through research of ultrasonic theory, we select the pulse ultrasonic wave by Ranging law, and according to their own ultrasonic signal waveform characteristics, the ultrasonic profile which receives on the different situation uses the different algorithm withdraws when extends the information, thus implementation orientation. Then, the system computation quantity increases, if still use the microchips to realize calculates the ability and real-time all is facing a severe test, thus this system selected the digital signal processor (DSP) to realize the system algorithm. so, this dissertation studies the portable Electronic Whiteboard and the existing ordinary Electronic Whiteboard difference mainly manifests in: On the one hand, the design of integrated systems, small and portable that is, pay attention to the considerations; On the other hand, the system has partially introduced DSP in algorithm processing, namely attention digitization considerations.This dissertation has studied the ultrasonic orientation theory, proposed four aspects needed in the implementation ultrasonic orientation, and specifically studies its implementation, which can be summed up as: Selects the synchronous signal to record ultrasonic signal the outset time; Selects the digital signal processor (DSP) as well as the match ADC chip to guarantee the system to the pointing accuracy and the timely request; Separately uses the dynamic double threshold value algorithm, the correlation function algorithm in view of different written as well as the zero examination algorithm to extract the ultrasonic signal arrive information, thus extracting delay, and positioning..The full dissertation is divided into six chapters, as follows: Chapter one elaborated Electronic Whiteboard present situation, Electronic Whiteboard application; and specifically elaborates the research object portable Electronic Whiteboard superiority, the composition and the performance indicators. Simultaneously, it pointed out the focus of this dissertation work and overall mentality. Chapter two elaborated the commonly used orientation method for ultrasonic orientation Electronic Whiteboard and the ultrasonic wave orientation theory, and the portable Electronic Whiteboard orientation principle which detailed elaboration this dissertation studies in this foundation.Chapter three detailed two questions of elaboration ultrasonic orientation which needs to be solved in the portable Electronic Whiteboard implementation: one is the ultrasonic time reference point choice and its implementation; another is the system orientation operation object ultrasonic signal reception and gathering. And in the elaboration system writes the signal pen color information recognition as well as the power-saving mode, such as the design and the implementation.Chapter four elaborated in detail different situation ultrasonic when extends withdraws the algorithm and its design and implementation for this system.Chapter five is system performance tests.Chapter six is summary of this dissertation work, as well as the system wait for the solution question. This dissertation creative work lies in:(1) Through analysis of dynamic range of the ultrasound signal received by the Electronic Whiteboard system, a kind of ADC chip is properly selected, and its sampling mode is set based on the precision of localization system;(2) After analyzing the waveform characteristics of ultrasound signals, and referring to the threshold detection algorithm and dual- threshold detection algorithm, the algorithm of dynamic dual- threshold delay extraction is presented with the actual research in this dissertation, and is realized by programming in the system;(3) Through analyzing the waveform of ultrasound signals received by the continuous points, and referring to the correlation function algorithm, the two-step correlation time-delay extraction algorithm is realized through DSP programming;(4) Through analyzing the waveform of ultrasound signals received by the volatility points, and referring to the zero detection algorithm, the envelope differential and zero detection time-delay extraction algorithm are realized through DSP programming.This dissertation system test result indicated that, this system has the better positioning accuracy, stability, reliability is also better. But there are still some system problems to be further studies, mainly are:(1) Design and implementation of ultrasonic adjustable amplify- ing electric circuit;(2) Temperature demarcating.