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Improving Performance of Cable Robots by Adaptively Changing Minimum Tension in Cables
Saeed Abdolshah,Giulio Rosati 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.18 No.5
Higher tension in cables of a cable-driven parallel robot is preferable due to increased stiffness, higher disturbance rejection, better trajectory tracking performance and more precise motion; however, cable tension augmentation can result in saturation of actuators and high-energy consumption. This paper is devoted to investigate if dynamically changing the minimum tension in cables can allow achieving an efficient motion in term of power consumption, while preserving good trajectory tracking performance. The proposed method changes the minimum tension on-the-fly according to stiffness, dynamics of the system, and error values as feedback. A simple cable robot prototype has been used to compare traditional fixed minimum tension utilization, and the proposed approach. Experimental results showed that application of our method improves motion accuracy and reduces energy consumption of the robot.
Investigation into Hand Impact Force During Forward Falls on Uneven Terrain
Saeed Abdolshah,Nader Rajaei,Yasuhiro Akiyama,Yoji Yamada,Shogo Okamoto 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.3
Outdoor falls predominantly occur because of environmental factors, such as tripping caused by uneven terrain; as a result, the faller may land on an uneven surface. Forward falls are among the most frequent causes of fractures. Previous investigations concentrated on the evaluation of impact forces acting on the hand/wrist on even terrains; however, further studies are necessary to evaluate the impact force during forward falls on uneven surfaces, which may occur frequently in daily activities. This study investigated the distal/proximal hand impact force during forward falls on even/uneven terrain. A series of fall experiments in which the distal and proximal areas of the hand contacted the ground simultaneously (even surface) or at different times (uneven surface) was conducted. The results showed that the magnitude of the peak impact forces acting on the distal and proximal areas are strongly associated with the terrain shape and the contact timing. Although in all experiments, a significant portion of the impact force was exerted on the proximal area of the hand, the earlier distal-ground contact reduced the peak proximal impact force significantly. The results of this study are beneficial for finding strategies to reduce fall-related injuries and the design of protective gloves and wrist guards to satisfy fracture prevention requirements.