Dynamic Simulation and Control of Exoskeletal Devices for an Astronaut’s Hand and Leg

Abstract

Humanity is in the edge of space exploration, but severe health problems arise as space missions increase in time. The STAMAS European project focuses on two relevant problems, hand fatigue during extravehicular Activities (EVAs) and lower libs chronic physiological degradation. To counteract these health conditions it proposes two demonstrators, an astronaut semi-passive leg exercising device and an EVA hand support exoskeleton. In the current research project controller strategies have been analysed to determine a suitable control architecture for both devices and an interactive simulation tool was developed to simulate and visualize the device behaviour. The main features of the interactive tool include the astronaut hand, leg and device actuator dynamics, the device kinematics with the force attack points and a simulation of the air pressure during EVAs. The chosen controller uses an impedance feedforward control architecture. The torque controlled human simulation includes an accurate 22 degrees of freedom representation of the human hand and an 8 degrees of freedom leg, that were modelled as serial robots with rotational joints, actual link lengths, mass and moments of inertia. Denavit-Hartenberg's recursive method was used for kinematics analysis and the recursive Newton-Euler formulation was used to calculate on-line the dynamics of the system.