本文的亮点在于通过施加旋转磁场对胶囊运动状态监视和解算胶囊pose。主要阐述了在旋转磁场下，含有内置磁传感器的胶囊，通过观察和计算自身检测到的磁场，来反解出自身所处的状态 “synchronous”，“step-out”，还是 “stuck（stationary）”，当胶囊“stuck（stationary）”时，胶囊内传感器收集到的一个周期磁场为一个椭圆形；当胶囊“synchronous”时，胶囊内部传感器收集到的一周期磁场集中在一小段圆弧（点）；当胶囊“step out”时，胶囊内部传感器收集到的一周期磁场散落在一个椭圆形。而“step-out”和 “stuck（stationary）”都是胶囊的不正常状态，“synchronous”是正常状态，每次进入不正常状态都要尽快脱离，进入正常状态。总的来说，内置磁传感器胶囊具有此天生的优势，非常容易判断状态正常与否，而状态的判断恰好又是胶囊同步内环闭环的重要基础，其他闭环驱动定位算法也都会碰到建立胶囊同步内环的问题。
用于磁胶囊内窥镜的闭环控制的本体磁场感知
Proprioceptive magnetic-field sensing for Close-loop Control of magnetic capsule endoscopes [1]
Paper Link
Authors: Katie. M. Miller, etc.
2012，IEEE/RSJ International Conference on Intelligent Robots and Systems
一种传感器配置被设计，确保在胶囊的内部的永磁铁中心的一个三维磁场测量没有来自磁铁本身的干扰。它被实验展示了来自这些传感器的数据提供了必要的信息来在三种可能的胶囊状态中分辨：同步旋转，失步，和卡住。一个闭环控制器被实现来控制胶囊的领角来防止失步，同时提供最小场大小来确保胶囊以一些期望的速度同步旋转。
A sensor configuration was designed that ensures a three dimensional magnetic field measurement at the center of the capsule’s internal permanent magnet without interference from the magnet itself. It was experimentally shown that the data from these sensors provides necessary information to distinguish between the three possible capsule states: synchronous rotation, step-out, and stuck. A close-loop controller was implemented to control the lead angle of the capsule to prevent step-out, while providing the smallest field magnitude that will enable the capsule to synchronously rotate at some desired speed.
[1]: Miller, Katie M., et al. “Proprioceptive magnetic-field sensing for closed-loop control of magnetic capsule endoscopes.” 2012 IEEE/RSJ International Conference on Intelligent Robots and Systems. IEEE, 2012.