Modification of a 3D Haptic Robotic Device to Study Upper Limb Movement and Proprioceptive Reflexes

Abstract

The New Arm Coordination Trainer in 3D (NACT-3D) is a mechatronic device developed to investigate upper limb movement and quantify human proprioceptive reflexes through haptic interaction. This thesis evaluates whether the NACT-3D meets the technical requirements necessary to perturb the human arm at frequencies suitable for system identification, while simultaneously generating realistic 3D haptic environments. The NACT-3D integrates admittance and impedance control with multimodal sensing, offering capabilities beyond existing robotic platforms. Experimental testing was conducted using perturbation signals and optical tracking to assess the device's bandwidth, while SPACAR simulations were used to model theoretical performance under various conditions. Results show that the NACT-3D’s actuation system has sufficient force output and bandwidth; however, the current manipulator's high inertia and mechanical play significantly limit performance. Without the manipulator, the system achieves bandwidths above 40 Hz, but with the manipulator attached, performance drops below 6 Hz. Simulation results indicate that a redesigned manipulator can restore performance, enabling the system to meet its operational target. These findings demonstrate that although the current configuration is inadequate for high-speed perturbations, targeted improvements to the manipulator can enable the NACT-3D to become a robust tool for studying neuromechanical control and reflex modulation.