A study on improvement and application of intra oral jaw tracking device in six-degree of freedom

本研究的目的是开发一种利用两个正交相磁场的新型颌骨跟踪器。该设备的总体特点如下。1)该装置以六个自由度独立测量上下颌骨的运动。2)上下颌之间没有机械连接，不妨碍任何自然的颌骨咀嚼功能；3)精度为10微米，采样率为300赫兹；4)口腔内传感器部件足够小，不会干扰日常牙科临床中使用的任何牙科实践。该装置包括大的初级线圈和小的次级线圈，这些线圈连接到上下颌骨上。钳口的位置与二次线圈在磁场作用下的输出信号相对应。一次线圈：1)60 cm立方体空芯线圈2)180 cm立方体空芯线圈3)坡莫合金芯线圈45 cm×38 cm×18 cm长方体2。鉴相器：1)比较器和16位升降计数器2)FFT研究表明，要进行极高分辨率的颌骨运动分析，需要18-24位A/D转换器、位CPU和1024-8192点的FFT分析，解决了研制新型颌骨跟踪器的所有基本技术问题。

The Purpose of this research is to develop a new jaw tracking device by using two magnetic fields in quadrature phase. The overall features of this device are as follows. 1) The device measures upper and lower jaws movement independently in six degrees of freedom. 2) That has no mechanical connection between upper and lower jaws and does not prevent any natural jaw function as mastication, 3) The accuracy is 10 micrometer and sampling rate is 300 Hz, 4) The intra oral sensor parts are small enough not to disturb any dental practice usuing in daily dental clinics.The device involves large primary coils which make magnetic fields and small secondary coils which are attached to upper and lower jaws. Locations of jaw are correspond with out-put signals of secondary coils induced by magnetic fields.We tested several type devices.1. Primary coil : 1) Air core coil of 60cm cube2) Air core coil of 180cm cube3) Permalloy core coil of 45cmx38cmx18cm rectangular parallelepipes2. Phase detector : 1) Comparator and 16 bit up-down counter2) FFTThis study revealed that 18-24 bit A/D converter, 64 bit CPU and 1024-8192 points FFT analysis are required for extremely high resolution jaw movement analysis.All basic technical problems for developing the new jaw tracking device are resolved by this study.