Exoskeleton Arm Pronation/Supination Assistance Mechanism With A Guided Double Rod System

The wrist pronation and supination movement is important in everyday manipulation tasks. Users with limitations in this particular movement have severe impairment. While advanced upper-arm exoskeletons can assist in the pronation/supination movement, typically, the resulting exoskeleton frame that combines both the elbow joint and pronation/supination mechanism becomes heavy and bulky with a large volume. We propose a new arm pronation supination mechanism that is integrated into the exoskeleton frame and has a reduced weight and volume penalty. The mechanism functions via a double rod system, where the rods are guided through a set of specially shaped grooves that finally result in the rotation of the wrist component. The paper presents a plastic rapid prototype built using 3D additive technologies. The mechanism is actuated via a Bowden cable transmission. Its underlying kinematics are experimentally evaluated using an external motion capture system to identify its advantages and disadvantages.