Dynamic Modelling and Control of Exoskeleton Gantry Robot

Abstract

This thesis presents the development and analysis of dynamic model of an exoskeleton gantry used to perform brain studies in freely moving mice for neuroscience experiments. The dynamic of model of the exoskeleton gantry comprised of X and Y stages is developed, and relevant system characteristics like bandwidth and stability are studied using theoretical model to predict the system behavior. The predicted bandwidth of the open loop system is found to be 1.9Hz and 3.8Hz for the Stage X and Y respectively using the theoretical model. The open loop system was further verified experimentally using LABVIEW and an experimental model was generated using computer software. 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 open loop system is also used to gauge the stability of the closed-loop and the gain and phase margin are studied for the same purpose. According to theoretical studies, it is expected that the bandwidth of the open and closed loop system is expected to increase with a decrease in payload. The gain margin and phase margin are predicted theoretically and verified experimentally are well above the determined threshold of 2dB 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 19.2Hz and 16.4Hz 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.