3DOM: a 3 degree of freedom manipulandum to investigate redundant motor control.

This paper presents a novel robotic interface to investigate the neuromechanical control of redundant planar arm movements. A unique aspect of this device is the third axis by which the wrist, and hence the pose of the arm can be fully constrained. The topology is based on a 5R, closed loop pantograph, with a decoupled wrist flexion/extension cable actuated mechanism. The design and characterization (in terms of range of motion, impedance, friction and dynamics) are described in this paper. This device is lightweight, safe and has high force capabilities and low impedance. Simple experiments illustrate the advantages of this device for the investigation of redundant motor control in humans.