Dynamic Modelling and Control of Exoskeleton Gantry Robot

Abstract

This thesis presents the development and analysis of a dynamic model for an exoskeleton gantry used to perform neuroscience experiments in freely moving mice. The dynamic model of the exoskeleton gantry, comprised of X and Y stages, is developed, and relevant system characteristics like bandwidth and stability are studied using a theoretical and experimental approach. The predicted bandwidth of the open-loop system, using the theoretical model, is found to be 1.9 Hz and 3.8 Hz for Stage X and Y, respectively. The open-loop system was further verified experimentally using LABVIEW, and system identification was performed using MATLAB. According to the experimental results, the open-loop bandwidth of the X and Y stages was found to be 2.3 Hz and 2.76 Hz, respectively. Furthermore, the gain and phase margin of the open-loop system is used to gauge the stability of the closed-loop system. According to the theoretical model, it is expected that the bandwidth of the open and closed-loop systems increases with a decrease in payload. The gain margin and phase margin, predicted theoretically and verified experimentally, are well above the determined threshold of 2 dB for gain margin and 450 for phase margin. This ensures the stability of the closed-loop exoskeleton system. Moreover, the closed-loop bandwidth of the system is predicted using the theoretical model, and an admittance control framework is proposed. The predicted closed-loop bandwidth for the exoskeleton gantry is found to be 19.2 Hz and 16.4 Hz for X and Y stages, respectively. Furthermore, preliminary experimentation of the gantry with admittance control implementation suggests a closed-loop bandwidth of 46Hz for Stage X.