Current Issue : January - March Volume : 2020 Issue Number : 1 Articles : 5 Articles
This study addresses the problem in designing pneu-net actuators to achieve specific target trajectories for particular applications.\nThe finite element analysis (FEA) method is used to study the sensitivity of 9 design parameters to bending deformation of\nactuators, and the results of FEA demonstrate that the width of the chamber and the width of the middle layer have great influence\non the bending performance. Besides, the relations between the bending angles of actuators with different width parameters and\nthe pressure are always highly linear. Using FEA and the cubic polynomial fitting algorithm, a unified bending model of the pneunet\nactuator is established with three crucial design parameters (i.e., segment length, chamber width, and middle-layer width). An\noptimum design method based on the bending model and genetic algorithm (GA) is put forward to automatically adjust these\nthree crucial parameters to realise trajectory matching. The method is developed to be an effective solution for the problem in\nmatching the target trajectory with the experimental results achieved on an actuator designed by imitating a human index finger.\nFurthermore, the results of the experiment also verify that the actuator can achieve stable grasping, and the proposed method has\nan important directive to design pneu-net actuators for their application in the fields of robotics, rescue, and detection....
Various actuator topologies are discussed for the purpose of powering periodic processes\nand particularly walking robots. The Clutched Parallel Elastic Actuator (CPEA) is proposed to reduce\nthe energy consumption of active exoskeletons. A nonlinear model of the CPEA is presented in\naddition to the mechanical design. The CPEA prototype is operated with a passive load on the\nwalking trajectory of the hip joint. The actuator is controlled with a cascaded position control and a\nsuperimposed Iterative Learning Controller (ILC). The controller was chosen to ensure comparability\nbetween active and deactivated spring operation. The application of the CPEA has the potential to\nincrease efficiency in the design of exoskeletons....
The present study intends to provide the photoelastic coefficient and thermal expansion coefficient needed to use an FBGembedded\nCFRP rod (smart rod) as strain sensor. Due to the monolithic combination of the FBG sensor with a CFRP rod, the\nsmart rod is likely to exhibit thermal and mechanical properties differing from those of the bare FBG sensor. A tensile test\nshowed that the photoelastic coefficient of the smart rod is 0.204, which is about 7.3% lower than the 0.22 value of the bare\noptical FBG.......................
The paper aims to develop improved acoustic-based structural health monitoring (SHM) and\nnondestructive evaluation (NDE) techniques, which provide the waves directivity emitted by the angle\nbeam wedge actuators in thin-walled structures made of plastic materials and polymeric composites.\nOur investigation includes the dispersive analysis of the waves that can be excited in the studied\nplastic panel. Its results allowed to find two kinds of generated acoustic waves-anti-symmetric\nLamb waves (A0) and shear horizontally polarized SH waves (SS0). The bounds of the chosen\nfrequency range for the experimental and numerical studies were accepted as a compromise between\nthe desire to obtain a high defect resolution by generating short waves, their adjustable directivity,\nand maximum propagation length. The finite element model for the transducer was built by using\nthe results of an actuator structure experimental study. The frequency response functions for the\nactuator current and oscillation amplitude of the footprint surface demonstrated good agreement.\nThe found eigenfrequencies of the actuatorâ??s structure were used for the numerical and experimental\nstudy of the Lamb and SH wave generation and propagation in a thin-walled plastic panel. Our\nresults convincingly demonstrated the satisfactory directivity of the actuated waves at their excitation\non the frequencies that corresponded to the natural modes of the actuator oscillation. The authors\nassume that an efficient use of the proposed technique for other analyzed quasi-isotropic materials\nand applied actuators can be provided by preliminary research using a similar approach and methods\npresented in this article....
Mechanically responsive materials are promising as next-generation actuators for soft\nrobotics, but have scarce reports on the statistical modeling of the actuation behavior. This research\nreports on the development and modeling of the photomechanical bending behavior of hybrid\nsilicones mixed with azobenzene powder. The photo-responsive hybrid silicone bends away from the\nlight source upon light irradiation when a thin paper is attached on the hybrid silicone. The time\ncourses of bending behaviors were fitted well with exponential models with a time variable, affording\nfitting constants at each experimental condition. These fitted parameters were further modeled using\nthe analysis of variance (ANOVA). Cubic models were proposed for both the photo-bending and\nunbending processes, which were parameterized by the powder ratio and the light intensity. This\nmodeling process allows such photo-responsive materials to be controlled as actuators, and will\npossibly be effective for engineering mechanically responsive materials....
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