No abstract

Exoskeleton is a wearable active device used to augment human power in upper or lower extremities. One of the most important application of these devices is to help the disable people to compensate the lack of functionality or rehabilitate. The main scope of this research is to design a prototype of a light, wearable robotic exoskeleton to rehabilitate the upper extremity in stroke patients at home. For this purpose mechanism of a wearable exoskeleton will be proposed compatible with upper extremity DOFs with minimum number of actuators which is constructed inexpensively. This idea proposes to provide an efficient, lightweight, and cost-effective device which was available for the patients at home to eliminate the demand of expensive and professional therapists. The conceptual design of such a system should be offered studying the actuation mechanism and degrees of freedom of the upper extremity for compatibility and safety issues of the proposed system. The novelty of this paper goes to the elbow actuator and minimize the number of actuators.

In laser-assisted machining (LAM), the laser source is focused on the workpiece as a thermal source and locally increases the workpiece temperature and makes the material soft ahead of the cutting tool so using this method, the machining forces are reduced, which causes improving the surface quality and cutting tool life. Machinability of advanced hard materials is significantly low and conventional methods do not work effectively. Therefore, utilizing an advanced method is inevitable. The product life and performance of complex parts of the leading industry depends on surface integrity. In this work, the surface integrity features including microhardness, grain size and surface roughness (Ra) and also the maximum cutting temperature were investigated experimentally in LAM of Ti-6Al-4V. According to the results, cutting speed has inverse effect on the effectiveness of LAM process because with increasing speed (15 to 63 m/min), temperature decreases (524 °C to 359 °C) and surface roughness increases (0.57 to 0.71 μm). Enhancing depth of cut and feed has direct effect on the process temperature, grain size, microhardness and surface roughness.

Surface integrity of workpieces after machining processes is one of the most essential requirements of engineers in advanced industries, since it has significant effect on performance and service life of the components. Based on this, thermal and mechanical loads generated by machining are responsible for change in mechanical properties of the machined workpiece and consequently, they should be controlled. Among them, Ti-6Al-4V is utilized extensively by engineers because of its excellent properties. Therefore, at the present study, extensive experiments were conducted to characterize the performance of machining operation regarding the surface integrity of Ti-6Al-4V super alloy. Hence, the effect of experimental conditions on microhardness profile, surface roughness, grain size, and maximum machining temperature was studied. The results indicated that, cutting speed is a predominant parameter for enhancement of surface microhardness and increase in feed rate has the striking influence on thermal loads enhancement. The results also demonstrated that, increasing depth of cut has the lower influence on grain size variation.