The field of robot-assisted physical rehabilitation and robotics technology for providing support to the elderly population is rapidly evolving. Lower limb robot aided rehabilitation and assistive technology have been a focus for the engineering community during the last three decades as several robotic lower limb exoskeletons have been proposed in the literature as well as some being commercially available. Numerous manufacturing techniques and materials have been developed for lower limb exoskeletons during the last two decades, resulting in the design of a variety of robot exoskeletons for gait assistance for elderly and disabled people. One of the most important aspects of developing exoskeletons is the selection of the most appropriate proper material. The material selection strongly influences the overall weight and performance of the exoskeleton robot. The most suitable fabrication method for material is also an important parameter for the development of lower limb robot exoskeletons. In addition to the materials and manufacturing methods, the actuation method plays a vital role in the development of these robot exoskeletons. Even though various materials, manufacturing methods and actuators are reported in the literature for these lower limb robot exoskeletons, there are still avenues of improvement in these three domains. In this review, we have examined various lower limb robotic exoskeletons, concentrating on the three main aspects of material, manufacturing, and actuation. We have focused on the advantages and drawbacks of various materials and manufacturing practices as well as actuation methods. A discussion on future directions of research is provided for the engineering community covering the material, manufacturing and actuation methods.

All pre-stressed structures called as tensegrity structures have been introducing into robotics, modern architectural designs, and medical necessities called bio-tensegrity, space structure alternates, and many other emerging technologies because of its numerous useful properties. Six bar tensegrity ball robot structure has an essential importance in the field of robotics due to its deployable, movable, deformable, and easily controllable capabilities. This structure has 6 rigid bars (in compression) and 24 flexible strings (in tension) that are connected in such a 12 nodes arrangement that provides the highest spatial symmetrical shape to this structure among most of the tensegrity structure. In this paper, the internal forces of bars and strings on each node have been studied, and the force equation on every node has been developed. Furthermore, the balance of all bars and strings forces on the whole structure has been analytically verified to assure the structure remains statically pre-stressed under the zero net effect of all internal forces applied by bars and strings.