Exoskeleton robots are categorized as rehabilitating and assisting robots which could be applied in other applications such as power augmentation systems, haptic systems, and virtual reality. Considering the increasing number of old people and those who suffer from physical weakness and some kinds of disabilities, the need of exploiting the rehabilitation mechanisms and processes is one of the most important issues in this field. In this paper a simple upper limb exoskeleton with one degree of freedom is studied and developed. The joint torque estimation corresponding to the biological movements as well as safety issues are considered. Kinematic parameters of the upper limb are needed to design the robot, thus a mechanism is designed to derive this set of data. Then a prototype of the exoskeleton is introduced, whose mechanical design, actuation and power transmission method as well as its selection criteria are discussed here. The mechanical design section is followed by electrical circuits and devices. Finally, the performance of robot is evaluated using a test-rig mechanism which examines how the kinematical parameters of arm could be tracked by our approach.