Algorithm Research And Device Design Of The Six-degree-of-freedom Electromagnetic Positioning

Six-degree-of-freedom electromagnetic positioning technology has no sightblocking restriction and obtains six-degree-of-freedom information which candescribe motion state of target vividly. It has important application value in the fieldof virtual reality, medical auxiliary and motion state analysis. Currently, our countrylacks of mature six-degree-of-freedom electromagnetic positioning products that wedesign independently, products we use are foreign brands. This paper has studiedelectromagnetic positioning algorithm and its implementation on the DSP platform,developed a prototype integrated with transmitting and receiving unit. It providesreference for the development of related six-degree-of-freedom electromagneticpositioning products.The main contents of this paper are as follows:(1) Analyze basic principle of electromagnetic positioning and the composition ofsix-degree-of-freedom electromagnetic positioning system, and give spatialcoordinate model and magnetic vector calculation model. Study on rotation matrix,eular angle and quaternion three classical positioning algorithms and simulatealgorithms, and then summarize computational complexity and related characteristicsof each algorithm based on quantitative and qualitative analysis of simulation results,and then choose rotation matrix algorithm to be theoretical basis of practicalelectromagnetic positioning algorithm.(2) Design signal processing flow of device and simulate the features oftransmitting and receiving signals. Core processing unit generates three differentfrequency sinusoidal signals, amplify amplitude and power of signals, and then usingthese signals to drive source simultaneously. And then transmit partial pressure ofdriving signal to receiving unit as a reference signal. Receiving antenna receivessignals by electromagnetic induction. And then select receiving signals and referencesignal using time sharing option. After filtering and amplifying signals, use analog todigital conversion circuit converts signal into data that core processing unit canprocess. Calculate position and attitude parameters using rotation matrix algorithmand send information to PC display unit through serial port. Design and implementhardware circuit of core processing unit based on the flow.(3) Design software program of device according to practical solution forpositioning algorithm. Firstly, sample receiving signal of the device and select the starting point of reference signal by using threshold detection method. Secondly,implement synchronous demodulation for receiving signal of each axis and designdigital low-pass filter to pross signal. Thirdly, extract the desired signal to implementFFT and matrix fitting according to the different frequency of transmitting signals.Calculate parameters by using rotation matrix algorithm and finally display the spatialposition of target on the interface of PC software, besides, show the attitudeinformation in this position at the same time.(4) Set up a complete six-degree-of-freedom electromagnetic positioning deviceintegrated with the signal transmitting unit, receiving unit. Test the positioning deviceand use test results to verify the processing effect of the practical solution. Summarizedevice index parameters from test results at the same time. The device can achievepositioning in the spherical space within a radius of1.2m, refresh frequency is38Hz,positioning distance error is1.5cm, the average error of attitude angle is7degrees.The main contribution and innovation of this paper include:(1) Propose a practical solution for six-degree-of-freedom electromagneticpositioning algorithm based on DSP and verify feasibility and effectiveness of thesolution through simulation. Implement the singnal sampling, threshold detection,synchronous demodulation, low pass filter, FFT, the rotation matrix algorithm, serialcommunication program using C language, develope PC software based on VisualStudio2010software and MFC framework.(2) Design a signal processing solution for the device. The core processing unitgenerates three different frequency sinusoidal signal, three signals are loaded onto thesource simultaneously. The wave is stable and strong under the continuous excitationof sinusoidal signal and can effectively guarantee the positioning range. The sourcedoes not need to do time-division processing and three axis antenna receive datasimultaneously without waiting, thus simplify the hardware circuit and avoid thecomplex circuit and slow positioning problems of traditional time-division device, soit can ensure real-time positioning.(3) Design and implement core processing unit circuits, including: DSP minimumsystem, boost circuit, ADC, DAC, serial communication circuit. Develope asix-degree-of-freedom electromagnetic positioning device prototype integrated withthe signal transmitting and receiving unit finally.The test results show that the device can achieve six-degree-of-freedom positioningand provide solution for dealing with electromagnetic positioning signal and designof device, it is of some referential value to the applications.