Motion tracking systems are getting more and more widespread with the newest technologies. There is a growing demand for wireless, sensor-based tracking of different devices and describing their attributes of motion. The most important fields of application are navigation systems, smart consumer electronics devices, games with virtual reality and even military or medical applications.
In my thesis I present the idea and the design of another useful device based on motion tracking, the digital pen. Like in the case of many other tools or devices, ordinary pens will may someday be fully replaced by their smart versions. The digital pens can store or even translate the handwriting information into digital characters for later use. To detect the writing or the drawing, the movement of the tip of the pen is measured by sensors, and then transformed so its path can be determined. Using multiple sensors and sensor fusion can result in more accurate data, for this reason I use an Inertial Measurement Unit, which contains both an accelerometer and a gyroscope. In this paper I introduce the operation of the chosen sensors, how can relevant information be acquired from the data they provide and the possibility of fusing them. I implement the method of double integration to transform the acceleration data into linear position and evaluate its advantages and disadvantages. To ensure the wireless operation I use a Bluetooth module. In order to create an actual portable, small device to write with, I design a printed circuit board, that can provide all the necessary functions in one, inside of the pen. I design the appearance as well in a 3D CAD software. Finally, I investigate the possibility of using the results of this project as an input to a character recognition system, of which I describe the operation at the end of the paper.