Robotic ultrasound manipulator : calibration of position and orientation measurement system

Abstract

The ultimate goal of this project is to develop a fixture for holding and manipulating an ultrasound wand as adeptly as a trained technician. From the 2D slices recorded by an ultrasound transducer, a three-dimensional image can be reconstructed. To reconstruct the 3D image, position and orientation data are needed. In the interests of space and simplicity, a sensor integrating both a gyroscope and accelerometer was chosen for these measurements. Because of the inherent error induced by integrating acceleration to yield position, it was necessary to calibrate this instrument. A fixture was constructed with preset reference points for the purposes of comparison and error analysis. As expected, the measurements obtained directly from the gyroscope were sufficiently accurate to track orientation. The position values from integration of acceleration exhibited accumulation of error over time. From these data, it was clear that a secondary reference instrument is needed for accurate position measurements.