STUDY OF A 4DOF UPPER-LIMB POWER-ASSIST EXOSKELETON WITH PERCEPTION-ASSIST - Second Stage of Power-Assist Topics: Biomechanical Devices; Biorobotics; Emerging Technologies In Proceedings of the First International Conference on Biomedical Electronics and Devices - Volume 1: BIODEVICES, 164-169, 2008 , Funchal, Madeira, Portugal