Journal Articles
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Item Modeling and experimental validation of valve and pumping actuator of a piezo-hydraulic pump(Zibeline International Publishing Sdn. Bhd., 2019) Nayak, S.; Rao, M.; Rao, R.This paper presents experimental investigations on valve actuator and pumping actuator of a piezo-hydraulic pump with active valves. Quadratic arm flexurally amplified piezoelectric actuators (QAFAPA) are designed for the pumping actuator and the valve actuator. Simulations are carried out to determine the voltage-displacement characteristics of the QAFAPA using MATLAB/Simulink software. To perform the pumping action, slotted pumping diaphragm is designed considering acrylic as the material and is analyzed for its stiffness using ANSYS analysis software. The slotted pumping diaphragm is fabricated, and the stiffness is experimentally determined which matched well with the analysis result. One pumping actuator and one actuator similar for inlet and outlet valve is developed. Voltage-displacement experiments are carried out on the valve actuator and the pumping actuator. Further, the displacement of the slotted pumping diaphragm when assembled with pumping actuator is experimentally determined. Simulation and experimental results were compared, and the results obtained were in good agreement with each other. © 2019 Zibeline International Publishing Sdn. Bhd. All rights reserved.Item Recent trends in piezoelectric actuators for precision motion and their applications: a review(IOP Publishing Ltd, 2021) Mohith, S.; Upadhya, A.R.; Karanth P, K.P.; Kulkarni, S.M.; Rao, M.The need for precision positioning applications has enormously influenced the research and development towards the growth of precision actuators. Over the years, piezoelectric actuators have significantly satisfied the requirement of precision positioning to a greater extent with the capability of broad working stroke, high-accuracy, and resolution (micro/nano range) coupled with the advantage of faster response, higher stiffness, and actuation force. The present review intends to bring out the latest advancement in the field of piezoelectric actuator technology. This review brings out the specifics associated with the development of materials/actuators, the working principles with different actuation modes, and classifications of the piezoelectric actuators and their applications. The present article throws light on the design, geometrical features, and the performance parameters of various piezoelectric actuators right from unimorph, bimorph, and multilayer to the large displacement range actuators such as amplified actuators, stepping actuators with relevant schematic representations and the quantitative data. A comparative study has been presented to evaluate the pros and cons of different piezoelectric actuators along with quantitative graphical comparisons. An attempt is also made to highlight the application domains, commercial and future prospects of technology development towards piezoelectric actuators for precision motion applications. The organization of the paper also assists in understanding the piezoelectric materials applicable to precision actuators. Furthermore, this paper is of great assistance for determining the appropriate design, application domains and future directions of piezoelectric actuator technology. © 2020 IOP Publishing Ltd.Item Stability of breakwater defenced by a seaward submerged reef(2006) Shirlal, K.G.; Rao, S.; Ganesh, V.; Rao, M.The stability of a uniformly sloped conventional rubble mound breakwater defenced by a seaward submerged reef is investigated using physical model studies. Regular waves of wide ranging heights and periods are used. Tests are carried out for different spacings between two rubble mound structures (X/d=2.5-13.33) and for different relative heights (h/d=0.625-0.833) and relative widths (B/d=0.25-1.33) of the reef. It is observed that a reef of width (B/d) of 0.6-0.75 constructed at a seaward distance (X/d) of 6.25-8.33 breaks all the incoming waves and dissipates energy and protects the breakwater optimally. © 2005 Elsevier Ltd. All rights reserved.Item Ocean wave transmission by submerged reef-A physical model study(2007) Shirlal, K.G.; Rao, S.; Rao, M.Ocean waves can be destructive as steeper waves due to their high energy eroding the sandy beaches. During storm surge or high tide, the water level rises and if large waves occur, they will break closer to the beach, releasing enormous amount of energy resulting in strong currents. This causes heavy loss of beach material due to large-scale erosion. If these waves are made to break prematurely and away from the beach, they can be attenuated so as to reduce beach erosion. The reef, which is a homogeneous pile of armour units without a core, breaks the steeper ocean waves, dissipates a major portion of their energy and transmits attenuated waves. This paper experimentally investigates the armour stone stability of the submerged reef and the influence of its varying distance from shore and crest width on ocean wave transmission. © 2007 Elsevier Ltd. All rights reserved.Item Hydraulic performance of tandem breakwater with concrete cubes as armour units(2009) Rao, M.; Shirlal, K.G.; Rao, S.; Bharadwaj, P.Tandem breakwater system consists of a conventional breakwater protected by a seaward submerged reef. The paper discusses physical model study on the hydraulic performance of an isolated as well as tandem breakwater system subjected to varying wave climate and water depths, while keeping a constant crest width of submerged reef. The breakwater in both the cases are armoured with concrete cubes and the submerged reef is constructed with natural stones. It is found that the isolated breakwater is damaged for all waves except those of period 2.5 s. While a submerged reef of crest width (B) 0.40m placed at a seaward spacing(X) of 2.5m transmits only 52% to 81% of the incident wave height and thereby reduces the wave force on the main structure which inturn protects the inner main breakwater completely without causing any damage.Item Development of concrete armoured protected breakwater structure(CAFET INNOVA Technical Society 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2011) Rao, M.; Rao, S.; Shirlal, K.G.The present work involves the physical model study of stability of conventional single breakwater and the reef protected breakwater, constructed with concrete cube as an artificial armour unit. Regular waves of wide ranging heights and periods are used. The tests are carried out for different spacings between the two structures (X/d = 2.5-13.33) and for different relative heights (h/d = 0.625-0.833) and relative widths (B/d = 0.25-1.33) of the reef. It is observed that a reef of width (B/d) of 1.0-1.33 constructed at a seaward distance (X/d) of 6.25-8.33 exhibits a transmission coefficient (Kt) of 0.38-0.708, wave dissipates energy and protect the breakwater optimally. © 2011 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.Item Physical model studies on stability of concrete armoured breakwaters(2011) Rao, M.; Rao, S.; Shirlal, K.G.; Prashanth, J.; Balakrishna Rao, K.As the breakwater construction started moving in to deeper waters, the wave load on its armour increased resulting in usage of heavier armour units inviting environmental and logistical problems. With the advancement in the technology, concrete armour units have been extensively replacing the natural stones with benefits such as saving in the material and cost while reducing loads on the seabed and helping in construction of environment etc. Tandem breakwater and berm breakwater could be the alternative solutions for the above said case. This paper presents the two cases of physical model studies on the stability of concrete armoured structures, one with tandem breakwater and another on berm breakwater. Both the models are subjected to monochromatic waves with varying characteristics. From the study it was observed that in case of tandem breakwater the crest width of submerged reef and the distance between breakwater and reef are the defining parameter while in case of berm breakwater the height of the berm and its width are the characteristic factors in reducing the breakwater damage. © 2011 Taylor & Francis Group, LLC.Item Displacement characteristics of a piezoactuator-based prototype microactuator with a hydraulic displacement amplification system(Korean Society of Mechanical Engineers, 2015) Rao, M.; Rao, R.In this study, a new piezoactuator-based prototype microactuator is proposed with a hydraulic displacement amplification system. A piezoactuator is used to deflect a diaphragm which displaces a certain volume of hydraulic fluid into a smaller-diameter piston chamber, thereby amplifying the displacement at the other end of the piston. An electro-mechanical model is implemented to estimate the displacement of a multilayer piezoelectric actuator for the applied input voltage considering the hysteresis behavior. The displacement characteristics of the proposed microactuator are studied for triangular actuation voltage signal. Results of the experiments and simulation of the displacement behavior of the stacked piezoactuator and the amplified displacement of the prototype actuator were compared. Experimental results suggest that the mathematical model developed for the new piezoactuator-based prototype actuator is capable of estimating its displacement behavior accurately, within an error of 1.2%. © 2015, The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.Item Performance evaluation of ANFIS and SVM model in prediction of wave transmission over submerged reef of tandem breakwater(CESER Publications Post Box No. 113 Roorkee 247667, 2017) Kuntoji, G.S.; Rao, S.; Rao, M.; Mandal, S.Tandem breakwater plays a unique role in protecting the ports. It is an innovative breakwater concept consisting of conventional breakwater and a submerged reef operating in tandem. As the depth-limiting behaviour of reef, the tandem possesses less design risk for extreme events. For a tandem breakwater, the transmitted wave over the submerged reef plays avital role in the safety of the emergent breakwater. Coastal structures like breakwaters are massive in terms of size as well as in the costs. Any structure before finally being constructed has to be subjected to model investigations for its safety against the design parameters. The soft computing techniques such as ANFIS (Adaptive Neuro Fuzzy Inference system) and SVM (Support Vector Machine)models are developed using experimental data points to predict the hydraulic performance of submerged reef of tandem breakwater. The performances of two models are validated with measured data, with the help of statistical measures namelyRMSE (Root MeanSquare-Error), CC (CorrelationCo-efficient), SI (Scatter-Index) andNSE (Nash-Sutcliff Efficiency). The results testify that SVM model performed better with 0.965 CC, 0.0557 RMSE, 0.9113 NSE and 0.1503 SI compared to ANFIS model with 0.935 CC, 0.0754 RMSE, 0.869 NSE and 0.00233 SI. © 2017 by International Journal of Ecology & Development.Item Investigation on the performance of valveless pump for microdelivery of the fluid, fabricated using tool-based micromachining setup(World Scientific Publishing Co. Pte Ltd wspc@wspc.com.sg, 2017) Veeresha, R.K.; Rao, M.; Rao, R.; Tauro, A.M.Micropump is an integrated part of microfluidic system and is a boon to the field of miniaturization, owing to its helping hand in numerous applications mainly in biomedical, electronic cooling, fuel cells, spacecraft, etc. In this paper, an attempt is made to design and fabricate valveless pump, with active and passive valves. The actuation element used is piezowafer, piezowafer was experimentally tested and compared with simulated values from ANSYS for its peak displacement and these displacements were used to find volume pumped by pump. The pumping volumes found by experimentation are in good agreement with the simulated results. Further fabrication of valveless pump is carried out by using tool-based micromachining center which is a novel type of fabrication technique in micromachining. Through experiments, the optimum frequency of the pump was found to be 60Hz at an actuating voltage of 150V. The maximum head that a pump could pump was found to be 0.051m with pressure of 500.13Pa. The flow rate of the pump had a decreasing trend with increase in head. © 2017 World Scientific Publishing Company.