Design, development, and fabrication of a vibration detecting robotic foot-pad using embedded PVDF strips

Abstract

This thesis shows the design, fabrication, and early characterization process of a slip-sensing foot-pad made from PVDF strips embedded in a rubber molded structure. What follows suggests a proof-of-concept for a design that can be used to detect vibrations on the edges of a teethed structure. The ability to detect localized vibrations in the embedded PVDF sensors in this foot-pad can be used in future studies to measure the contact-patch area and investigate the relationship between the change in such area and incipient slip. The future iterations of the proposed foot-pad can be used to integrate with current foot-pads worn by legged robots such as MIT Cheetah to enable them to predict slippage. An experimental procedure was used to find the effect of a localized stress on the embedded sensors' data. Three iterations of the foot-pad were designed and fabricated. Furthermore, a custom slippage tester was designed and built for future studies. The experimental results suggested that the effect of triggering on the foot-pad was highly localized since it did not affect neighboring sensors. This behavior can be used to measure changes in the contact-patch area since loss of contact between the ground and foot-pad introduces vibrations on the edges of the pad. Though further data collection and mapping should be conducted for this foot-pad to be able to predict slippage, the experimental results suggest that usage of urethane embedded PVDF sensors can be a viable and promising approach in achieving this goal by detecting the localized vibrations induced by the slip incident.