| The Single Fiber Scanning Endoscope is designed with a resonant fiber scanner at the distal end of a thin flexible shaft to produce a flying spot scan for image acquisition purposes. Based on results from large scale prototypes, dynamic nonlinearities during large amplitude vibrations of the resonant fiber scanner result in distortions in the two-dimensional scan pattern and the acquired images.; A nonlinear state-space dynamic model of the Single Fiber Scanning Endoscope is developed to understand scan distortion caused by nonlinear scan dynamics and as the basis for nonlinear state-space tracking controllers to remove those distortions. The non-planar nonlinear partial integro-differential equations for the continuum dynamics of a resonating base excited cantilever undergoing large scale vibrations are reduced to a set of state-space coupled Duffing equations with centripetal acceleration. Models for internal and aerodynamic damping are investigated.; To verify the validity of the system model, the analytic frequency response is determined for three typical scan patterns: raster, spiral and propeller scans. The analytic and experimental frequency responses are compared near resonance for various input amplitudes and for all three scan patterns. The model parameters are also estimated from the frequency response. The experimental frequency responses match the predicted frequency responses for all three scan patterns, for various amplitudes, and using the same model parameters.; A robust state-space controller with feedback linearization has been simulated and implemented to force the resonant fiber scanner to follow the three reference scan patterns. Acquired images using the spiral scan at 250 x 250 pixel resolution demonstrate improved image fidelity over previous images taken with open-loop scanning. |
