| The six degree of freedom(6-DoF)motion tracking is used for measuring,tracking and recording the motion trajectory and attitude status of objects as a High-tech system in 3D space,which is considered to be one of the key technologies of human-computer interaction,virtual reality system,robot remote control,interactive games,sports training and other application fields.In this paper,electromagnetic sensing based tracking technology(EMT)is studied,compared to the optical tracking equipment and inertial navigation technology,electromagnetic motion tracking device is low-cost,simple to assemble,and it has good penetration which the optical type lacks.Because the absolute position is calculated in EMT,there is no error accumulation problem.Therefore,the electromagnetic positioning technology has unique advantages different from the traditional tracking technologies,and there is a great potential for application and development to be tapped.However,how to improve the accuracy,real-time performance and anti-interference ability of EMT system is still a widely studied topic.The main scientific issues discussed in this paper include:(1)The magnetic field distribution model of the current carrying coil is the most important problem for solving the6-DoF parameters quickly and accurately.(2)Because of the serious attenuation of electromagnetic signal,it is very difficult to analyze the position coupling information from the weak induction voltage,which requires high reliability for filtering and demodulation.(3)In addition,the commonly used pre-calibration technology relies on manual marking,or the assistance of redundant heterogeneous positioning equipment,so an automatic and efficient calibration method on system parameters is a research hotspot for EMT system.Integrating the interdisciplinary knowledge of electromagnetics,digital signal processing,algorithm analysis and electronic circuit design,etc.,in this paper,thealternating magnetic field model and a novel 6-DoF algorithm are studied,the frequency mismatch problem in asynchronous demodulation is explored;after identifying the parameter deviation in the static environment,a new system calibration method is proposed.The electromagnetic motion tracking system with practical value is developed,and the position and orientation results are displayed in a visual way.The main research contents and characteristics can be summarized as follows:1.In the quasi-static electromagnetic field,a physical model of the non-coaxial emitter coil array on the same plane is studied.This paper will aim at the same plane layout of transmitting coil array,through the comparative analysis of magnetic field distribution characteristics under different positioning models,an integrated approach is developed to take account of both real-time and close range accuracy.2.To explore fast algorithms for computing the position and attitude of moving objects.Establishing an positioning model with equivalent simulation,studying efficient algorithms for calculating optimal 6-DoF parameters,and comparing the numerical error and convergence speed of several typical solutions.3.Design and implementation of electromagnetic tracking circuit system.Research on the technology of receiving and processing electromagnetic signals under quasi-static electromagnetic field,to explore signal separation method based on frequency division excitation and its frequency mismatch problem.The signal generator,coplanar transmitting coil array,sensing coil and data acquisition card are integrated to build a platform for verifying object tracking algorithms.4.An automatic calibration method of system parameters in static environment is proposed.Calibration is usually a complex and tedious process,this paper discusses a new method for correcting parameter bias with independent and simple configuration,so that the system can be quickly calibrated by constructing and solving the over determined equations involving all parameters.This paper adopts the research method of combining theoretical analysis with circuit implementation,new solutions are proposed to resolve basic research problems of electromagnetic tracking system,which aims at improving precision,reducing delay and noise interference.The development process of the EMT system is described in terms of research background,physical model of positioning,6-DoF solving equations,digital signal demodulation,parameter pre-calibration and test platform.These new algorithms are also compared with the existing researches to demonstrate their innovation and effectiveness.Through the depth and detailed exploration,this study can enrich the connotation of electromagnetic theory in specific circumstances,and promote the practical application of this technology in the field of motion tracking. |
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