INVERSE ANALYSIS FOR THE RECOVERY OF FORCES APPLIED TO PHOTOELASTIC TACTILE TRANSDUCERS

In this paper, the forward and inverse analyses of one-and two-layer p hotoelastic tactile transducers are presented. For such transducers, a n applied force profile generates stresses in the photoelastic layer, making it birefringent. Consequently, circularly polarized light input to the transducer becomes elliptically polarized at the output becaus e of the introduction of a phase-lead distribution. Herein, the forwar d and inverse analyses of a one-layer photoelastic tactile transducer, under ideal conditions, are first presented. The transducer is modele d using closed form equations based on the theories of elasticity and photoelasticity, which allow the calculation of the light intensity di stribution corresponding to an applied force profile. However, to reco ver the force profile from a light intensity distribution (i.e., the i nverse problem), the phase-lead distribution must be determined first. A novel technique is described for this purpose. In the second part o f the paper, we consider the forward and inverse analyses of a two-lay er transducer, under nonideal conditions, where the light-intensity di stribution is no longer noise-free. In the forward analysis, the calcu lation of the stress distribution in the transducer is implemented by finite-element analysis. The recovery of the phase-lead distribution u nder noisy conditions, however, constitutes an ill-posed inverse probl em. A novel algorithm that accurately and effectively determines the p hase-lead distribution from a noisy light-intensity distribution is pr esented. (C) 1998 John Wiley & Sons, Inc.