MODELLING AND SIMULATION OF HUMAN. MIDDLE EAR PROSTHESIS

Abstract

Human hearing is an important sensing organ and any deficiency in its nor- mal behavior induces serious hazards to working life. Reconstruction of middle ear with passive and active prosthesis is found as a remedy to recover normal behav-ior of human ear. Appropriate implantation of actuator is very tedious job while actively reconstructing- the human middle ear. Investigation of dynamic behavior of reconstructed human ear is the primary goal of the present work. Formulation of an actuator model to overcome problems due to its improper implantation, is also a motivation for current dissertation. Solo multibody system models for one- and three-dimensional actuator are created and simulated to analyze individual dynamical responses. Measurements on a real pizeo-electric actuator are carried out with Laser Doppler Vibrometer and internal parameters (stiffness and damping) are identified. Passive and ac-tive reconstruction of middle ear is also modelled with a piston prosthesis and an actuator respectively. Sound transfer through human ear can be described by linear models, but for pathological cases or reconstruction or for high sound pres-sure case, a nonlinear description of ear model is necessary. Nonlinear behavior of various joints and actuator coupling is included to properly simulate the real life situations. While implanting the actuator in a pathological human ear, a surgeon is always interested to know the value of actuator excitation for a particular kind of disease. It is always desired that first an actuator is implanted in the human ear and then suitable excitation is applied to restore the damaged hearing. Inverse dynamics of human middle ear is analyzed to compute appropriate excitation of actuator for guiding the ossicular chain in a particular fashion. Actively reconstructed model of human middle ear is found to be fruit-ful, as it shows some recovery in pathological behavior of human ear. Three-dimensional actuator model partially fulfills its need of creation, as it demonstrates a reduction in change of stapes motion with variation in actuator orientation angle. Nonlinear description of parameters realistically includes their effect by approach-ing human ear behavior towards reality. Actuator excitation for a desired stapes motion is computed for a direct force applying actuator and a force actuator is suggested instead of displacement actuator for this purpose.