Second Generation Tactile Imaging System for Mechanical Properties Estimation

Abstract

The Tactile Imaging System (TIS), developed in the Control, Sensor, Network, and Perception (CSNAP) Laboratory at Temple University, is a novel non-invasive method to measure the size and elastic modulus of inclusions. In this thesis, we revamped TIS to enlarge the contact area and replaced the lens to provide clearer shape information. We investigated different lighting sources and configurations in order to obtain clearer images of the target. We also improved the illuminating circuit using a constant current driver and a Pulse Width Modulation (PWM) dimming to stabilize the light brightness. After confirming the ability to obtain clearer images of the target, we compared the newly revamped TIS with the older version. The results showed that the images are clearer with a 214% larger interrogation area. We compared the accuracies of two tactile imaging systems using the depth, size and elastic modulus estimation algorithms. The results indicated that the second generation TIS (TIS G2) has better performance in all three parameters. TIS G2's error for depth estimation was 1.4%, which is 5.78% better than first generation TIS (TIS G1). TIS G2's error for size estimation was 5.28%, which is 0.96% better than first TIS G1. TIS can only calculate relative elasticity of the phantoms. We made five phantoms with varying stiffnesses and TIS G1 could not differentiate different stiffnesses, while TIS G2 recognized four out of five phantoms' relative stiffness. Finally, we performed a t-test to see whether the differences in G1 and G2 are statistically significant. The results showed that there are significant differences between the two systems.