Embedded Files
The final design solution incorporates the use of two independent sensors to simulate the position of the otoscope tip with 6 degrees of freedom (DOF). The first of these sensors is a magnetometer, which is a magnet sensor that detects the magnetic flux density in three orthogonal directions in 3D space. While an electromagnet is moved around in the surrounding space, this changes the detected value and therefore by coupling multiple magnet sensors together, a localization method was used to predict a position in 3D space. Additionally, an inertial measurement unit (IMU) was used to track the yaw, pitch, and roll angle rotations that the otoscope tip experienced.
Magnetometer
In order to translate the detected magnetic flux densities to a localized 3D position in cartesian coordinates, 4 magnet sensors are used in this design. Three of these sensors are placed in a plane relative to another, whereas the fourth sensor is placed below this plane. Using these four magnetic flux density values along with the governing equation mentioned in chapter 4, the following algorithm shown in figure 4 can be used to solve for the localized 3D position in cartesian coordinates.
Inertial Measurement Unit (IMU)
To complete the 6 DOF tracking necessary to simulate the motion of the otoscope tip, an IMU is used to record the orientation of this point. An IMU consists of a 3D accelerometer and 3D gyroscope that measures the external force and angular velocity experienced by the sensor, respectively. By implementing a discrete time complementary filter as shown in figure x2 below, measurements from the gyroscope and accelerometer can be converted to a measurement of angular displacement.
MATLAB Graphical User Interface
The position and the orientation of the tip of the otoscope recorded by the magnetometers and the IMU, respectively, are displayed on a graphical user interface through the MATLAB application. In this interface, the shape of the otoscope will be illustrated as points that move continuously with time and will be shown relative to the ear mold, which is displayed as a stationary unit.
Video Demonstration of Final Design
Video Demonstration of Final Design
video-1654149750.mp4Hardware Development
Hardware Development
The instrumented otoscope was custom made to include the necessary components of the permanent magnet, IMU, and LED light.
Otoscope Interior Design
Otoscope Interior Design
Otoscope Exterior Design
Otoscope Exterior Design
Housing Unit
The housing unit was made using medical grade 304 stainless steel, as this material is non-magnetic and therefore would not create magnetic disturbances in the system.
Additionally, this housing unit consists of a circular, removable ear mold piece that has the magnet sensors on the back. This allows one to switch the model of the ear mold to the desired size, while maintaining the origin of the ear canal as the origin defined by the magnetometers.
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