The six-degree-of-freedom electromagnetic tracking system calculates the six degrees of freedom parameters of the target based on the principle of electromagnetic induction, thereby uniquely determining the position and attitude of the target. How to calculate the position and attitude parameters of the target from the received analog signal is the key to affect the performance of the entire system. In some early products, the processing of the receiving signal of the sensing antenna is mainly done by analog circuit and single-chip microcomputer. Due to the low precision of the analog circuit, the performance of the single-chip microcomputer is slow, which makes the whole system unable to accurately and accurately determine the target. s position. The DSP data acquisition system proposed in this paper utilizes DSP's fast instruction execution cycle and powerful digital signal processing functions and CPLD's flexible timing and logic control functions to quickly and accurately complete the acquisition and calculation of each received signal, which is accurate. The digital receiving matrix lays a good foundation for further calculation of the six degrees of freedom parameters of the target. This paper mainly introduces the hardware design scheme and software design flow of DSP data acquisition system.
1 How the electromagnetic tracking system works
The transmitting and receiving antennas of the six-degree-of-freedom electromagnetic tracking system are three-dimensional orthogonal loop antennas. The transmitting circuit is timed to the xyz axis of the transmitting antenna
Where x is the emission matrix, which is a unit diagonal matrix, G is the total gain of the system, and H and M are coordinate transformation matrices including the position of the receiving antenna relative to the transmitting antenna and the attitude angle of the receiving antenna. Therefore, the receiving matrix is ​​the key to affect the accuracy of the target parameters.
2DSP system hardware design
According to the principle of the six-degree-of-freedom electromagnetic tracking system, in order to obtain the system receiving matrix Y, the DSP system must simultaneously acquire four analog signals: T, Rx, R y, Rz, and each channel signal is time-division multiplexed. Therefore, the system is required to accurately distinguish the data of each time segment of each channel, and then calculate the amplitude of each segment of data and send it to the computer. The hardware structure of the DSP data acquisition system is shown in Figure 3.
The four analog signals are simultaneously sampled by two A/Ds. The sampled digital bit stream is sequentially transmitted to the DSP chip through the FIFO buffer, and the DSP quickly calculates the collected digital signal, and finally the calculation result is asynchronous. The serial interface is transferred to the computer. The timing coordination between the devices is controlled by the CPLD.
Watch strap,Headphone Cover,Earbuds Cover,Earphone Cover,Headset Covers
Nantong Boxin Electronic Technology Co., Ltd. , https://www.bosencontrols.com