Current Issue : April - June Volume : 2020 Issue Number : 2 Articles : 5 Articles
In the paper a model is developed for a proposed eddy current damper using finite\nelement analysis. Several damper configurations are studied and its characteristics are analyzed.\nThe steady state performance for the configurations is compared to reach a design with an\nacceptable performance for the eddy current damper. Furthermore, the proposed designs\nperformance are compared with the traditional damper performance. It was found that the best two\ndesigns to achieve the targeted performance were to have an iron core damper or an iron core with\nan aluminum sleeve. Those two designs are economical and simple while achieving acceptable\nperformance when compared to traditional dampers and other electromagnetic damping systems....
The paper introduces a modified version of a Proportional Integral Derivative (PID)-type\niterative learning algorithm, which is very simple to implement on a digital control device for tracking\ncontrol of a continuous-time system. The simulative application of it is for controlling a V-shaped\nelectrothermal microactuator (VEM) and is carried out by using a Simscape model of VEM for the\npurpose that the asymptotic tracking behavior of system output to desired trajectory will be verified\nin a virtually real environment. Obtained simulation results confirm that the introduced iterative\nlearning algorithm has not only provided a good output tracking behavior, as expected, but also is\nrobust in the sense of reducing external disturbance effects....
Soft robotic grippers often incorporate pneumatically-driven actuators that can elastically\ndeform to grasp delicate, curved organic objects with minimal surface damage. The complexity of\nthe actuator geometry and the nonlinear stressâ??strain behavior of the stretchable material during\ninflation make it difficult to predict actuator performance prior to prototype fabrication. In this work,\na scalable modular elastic air-driven actuator made from polydimethylsiloxane (PDMS) is developed\nfor a mechanically compliant robotic gripper that grasps individual horticultural plants and fungi\nduring automated harvesting. The key geometric design parameters include the expandable surface\narea and wall thickness of the deformable structure used to make contact with the target object.\nThe impact of these parameters on actuator displacement is initially explored through simulation\nusing the Mooneyâ??Rivlin model of hyperelastic materials. In addition, several actuator prototypes\nwith varying expandable wall thicknesses are fabricated using a multistep soft-lithography molding\nprocess and are inserted in a closed ring assembly for experimental testing. The gripper performance\nis evaluated in terms of contact force, contact area with the target, and maximum payload before\nslippage. The viability of the gripper with PDMS actuators for horticultural harvesting applications\nis illustrated by gently grasping a variety of mushroom caps....
Measuring distance and thickness simultaneously is important in biological, medical,\nelectronic, and various industries. Herein, we propose a method for simultaneously measuring the\ndisplacement and thickness of transparent materials using a pulsed terahertz wave. For this technique,\na beam splitter was used to design the optical path such that the terahertz wave would incident\nthe specimen vertically to achieve centimeter measurement range and micrometer resolution.\nThe measured terahertz waveform carries peak time information reflected from the upper and\nlower surfaces of the sample, and the thickness can be calculated using the time difference between\nthe first and second reflected peaks. The displacement can also be calculated using peak time difference\nwhen the sample moves from the initial position to the changed position. For validation, an experimental\ntest was performed using aluminum, acrylic, and glass plates. The results confirmed a measurement\nrange of 1 cm with an error of less than 23 microm, and the thickness error was less than 8 microm....
Piezoelectric unimorph deformable mirrors offer a cheap solution to adaptive optics,\nwith mass production capability. However, standard solutions have significant drawbacks:\n(i) the static shape is sensitive to the temperature, and (ii) the low structural damping limits the\ncontrol bandwidth, because of the interaction between the shape control and the vibration modes\nof the mirror. This paper discusses how these two problems may be alleviated by using a mirror\ncovered with an array of actuators working in d31 mode on the back side and a ring of transducers\n(actuators and sensors) on the front side, outside the pupil of the mirror....
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