Current Issue : July - September Volume : 2017 Issue Number : 3 Articles : 5 Articles
This paper presents a triple-finger gripper driven by a piezoceramic (PZT) transducer for\nmulti-target micromanipulation. The gripper consists of three fingers assembled on adjustable\npedestals with flexible hinges for a large adjustable range. Each finger has a PZT actuator,\nan amplifying structure, and a changeable end effector. The moving trajectories of single and\ndouble fingers were calculated and finite element analyses were performed to verify the reliability of\nthe structures. In the gripping experiment, various end effectors of the fingers such as tungsten probes\nand fibers were tested, and different micro-objects such as glass hollow spheres and iron spheres with\ndiameters ranging from 10 to 800 �¼m were picked and released. The output resolution is 145 nm/V,\nand the driven displacement range of the gripper is 43.4 �¼m. The PZT actuated triple-finger gripper\nhas superior adaptability, high efficiency, and a low cost....
Pump-controlled hydraulic circuits are more efficient than valve-controlled circuits, as they\neliminate the energy losses due to flow throttling in valves and require less cooling effort. Presently\nexisting pump-controlled solutions for single rod cylinders encounter an undesirable performance\nduring certain operating conditions. This paper investigates the performance issues in common\npump-controlled circuits for the single rod actuators. Detailed analysis is conducted that identifies\nthese regions in a load-velocity plane and the factors affecting them. The findings are validated by\nexperimental results. A new design is then proposed that employs a limited throttling valve alongside\ntwo pilot operated check valves for differential flow compensation to improve the performance.\nThe valve is of the flow control type and is chosen to have a throttling effect over critical regions;\nit has the least throttling over other operating regions, thus maintaining efficiency. Experimental\nwork demonstrates improved performance in a full operating range of the actuator as compared to a\ncircuit that uses only the pilot-operated check valves. This circuit is energy efficient and capable of\nrecuperating energy....
Rock bolts, as a type of reinforcing element, are widely adopted in underground excavations\nand civil engineering structures. Given the importance of rock bolts, the research outlined in this\npaper attempts to develop a portable non-destructive evaluation method for assessing the length of\ninstalled rock bolts for inspection purposes. Traditionally, piezoelectric elements or hammer impacts\nwere used to perform non-destructive evaluation of rock bolts. However, such methods suffered\nfrom many major issues, such as the weak energy generated and the requirement for permanent\ninstallation for piezoelectric elements, and the inconsistency of wave generation for hammer impact.\nIn this paper, we proposed a portable device for the non-destructive evaluation of rock bolt conditions\nbased on a giant magnetostrictive (GMS) actuator. The GMS actuator generates enough energy to\nensure multiple reflections of the stress waves along the rock bolt and a lead zirconate titantate (PZT)\nsensor is used to detect the reflected waves. A new integrated procedure that involves correlation\nanalysis, wavelet denoising, and Hilbert transform was proposed to process the multiple reflection\nsignals to determine the length of an installed rock bolt. The experimental results from a lab test and\nfield tests showed that, by analyzing the instant phase of the periodic reflections of the stress wave\ngenerated by the GMS transducer, the length of an embedded rock bolt can be accurately determined...
A novel flux control magnetic suspension system that places control plates beside the\nmagnetic source (permanent magnet) is proposed. In a conventional flux-path control magnetic\nsuspension system, the control plates were inserted between the magnetic source and the suspended\nobject (floator). In contrast, the control plates were placed beside the magnetic source in the proposed\nsystem. In such a configuration, the effective gap becomes larger than in the conventional system.\nBasic characteristics of the proposed magnetic suspension system were studied both numerically and\nexperimentally. The numerical analyses show that the attractive force acting on the floator increases\nas the position of the lateral ring-shape control plate increases. The variation of the attractive force\nis sufficient for the stabilization of the suspension system. It is also shown that lateral force can\nbe generated by dividing the plates into halves and moving them differentially. The predicted\ncharacteristics are confirmed experimentally in a fabricated apparatus with a three-axis force sensor\nand a gap adjustment mechanism....
Nano-positioning technology has been widely used in many fields, such as microelectronics,\noptical engineering, and micro manufacturing. This paper presents a one-dimensional (1D)\nnano-positioning system, adopting a piezoelectric ceramic (PZT) actuator and a multi-objective\ntopological optimal structure. The combination of a nano-positioning stage and a feedback capacitive\ncomb sensor has been achieved. In order to obtain better performance, a wedge-shaped structure is\nused to apply the precise pre-tension for the piezoelectric ceramics. Through finite element analysis\nand experimental verification, better static performance and smaller kinetic coupling are achieved.\nThe output displacement of the system achieves a long-stroke of up to 14.7 �¼m and high-resolution\nof less than 3 nm. It provides a flexible and efficient way in the design and optimization of the\nnano-positioning system....
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