Crawling Support Using Wearable SuperLimbs: Human-Robot Synchronization and Metabolic Cost Assessment

Abstract

A pair of Supernumerary Robotic Limbs (Super-Limbs) can brace the wearer’s upper body while they work at floor level, and support them during crawling. The SuperLimbs’ motion is synchronized with the operator to mimic natural human crawling. This synchronization relies on experimental data from the operator’s observed crawl. A method for predicting the phase difference between the SuperLimbs’ hand placement and the operators desired hand placement is developed and used to coordinate the SuperLimbs’ motion with the operator’s. The experimental data is also used to design the structure of the SuperLimbs to minimize their energy consumption during crawling and regulate their actuator’s temperatures.The SuperLimbs are designed to mimic the operator’s arms while they crawl, however factors such as their limited number of degrees of freedom (DoF), compared to natural limbs, and the compliance of the connection between the SuperLimbs and the operator means that the SuperLimbs’s may dynamically interact with the wearer differently from how their natural limbs do. A simple dynamic model is constructed to assess the energy consumed by the operator as they crawl with the SuperLimbs under different coordination patterns. An optimal coordination pattern is obtained from this assessment.