Department of Mechanical Engineering

Indian Institute of Technology Palakkad&nbsp;(IIT Palakkad or IIT PKD) is a public autonomous&nbsp;engineering&nbsp;and&nbsp;research&nbsp;institute located in&nbsp;Palakkad,&nbsp;Kerala. It was&nbsp;one of the five new&nbsp;IITs&nbsp;proposed in the&nbsp;2014 Union budget of India. The campus was inaugurated on 3 August 2015. The institute has 94 faculty, 978 students, and 63 non-teaching staffs.

IT Palakkad currently offers four-year Bachelor of Technology (B.Tech) and two years MS programmes in 8 different engineering disciplines including&nbsp;Computer Science, Electrical, Mechanical, Civil among others.

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IIT Palakkad

Lipid bilayer vesicles with fluid/fluid phase coexistence are promising model systems for biological cell membranes. They permit the investigation of the mechanical properties of lipid membranes that are important for understanding mechanistic aspects of biological membrane function. Comparison of experimentally obtained vesicle shapes to mechanical membrane theories has enabled us to determine the values of line tension and mean-curvature bending stiffness of liquid-ordered and -disordered membranes. An additional important parameter that controls membrane geometry is the spontaneous curvature, driven, for example, by peripheral protein coats or asymmetric lipid composition. We examine to what extent effects of differing spontaneous curvature and Gauss curvature stiffness between coexisting fluid phases can be distinguished by membrane shape analysis. We find that the equilibrium neck geometries of dumbbell-shaped vesicles and the shapes of vesicles close to budding are very similar for vesicles that differ in spontaneous curvature or Gauss curvature stiffness differences. However, the two parameters have qualitatively different influence on discontinuous budding transitions. © EPLA, 2009.

World University root node

Neck geometry and shape transitions in vesicles with co-existing fluid phases: Role of Gaussian curvature stiffness vs. spontaneous curvature

This paper provides an overview of the development of an interactive simulation system and Graphical User Interface (GUI) for an underwater robotic vehicle. Computer simulations and graphical interfaces are effective ways for studying the behavior of a system well before it is developed and deployed. It allows lot of flexibility in the design and greater scope for improvement without major financial commitments. The underwater vehicle and its sub-system properties, control inputs (parameter adjustments, maneuvers, etc), and the underwater environment are graphically represented on an user interface that can be easily accessed by the user for modifications. The interface provides convenient means to evaluate vehicle performance by means of animations, dashpot and time history plots of engineering variables of interest. The dynamic model and control algorithms, developed using standard tools are used at the back-end of the program to model and simulate various control behaviors of the vehicle. The environment conditions, parameter variations, disturbance forces etc. can be simulated using the back-end algorithm. The simulation results can be visualized using the GUI and various control strategies, navigational algorithms and path planning can be easily tested using the interface program. Few examples showing how the simulations can be used to identify design changes that can improve underwater vehicle dynamic and control performance are also provided. Copyright © 2009 by The International Society of Offshore and Polar Engineers (ISOPE).

Proceedings of the ISOPE Ocean Mining Symposium

Design of interactive simulation system and graphical user interface for underwater vehicle control and navigation

In this paper, a phase field model is developed for vesicle adhesion involving complex substrate and vesicle geometries. The model takes into account an adhesion potential that depends on the distance of vesicle to the substrate. A variational problem is solved in a 3D computational domain by minimizing the contribution of bending elastic energy and the adhesion energy under the constraints of total surface area and volume, described via a phase function. An adaptive finite element method is used to efficiently compute the numerical solutions of the model. The computational results are validated through comparison of several axisymmetric shapes with the sharp-interface ODE solution. Moreover, we compute shapes for non-axisymmetric situations to support the observation that concave substrates favor adhesion. © 2009 Elsevier Inc. All rights reserved.

Journal of Computational Physics

A phase field model for vesicle-substrate adhesion

The dynamics and diagnostics of cracked rotors have been gaining importance in recent years. Relatively few authors have addressed the problem of multi-crack assessment for rotors. In many cases there exist more than one crack on the shaft. Then the solutions or the combinations of parameters characterizing the cracks are more and the problem becomes more complicated. In this study, a new technique called amplitude deviation curve (ADC) or slope deviation curve (SDC) has been developed, which is a modification of the operational deflection shape (ODS). The effectiveness of the SDC over ODS for small cracks detection has been demonstrated in the present paper. © 2008 Elsevier Ltd. All rights reserved.

Journal of Sound and Vibration

Detection of two cracks in a rotor-bearing system using amplitude deviation curve

Modern developments in the fields of control, sensing, and communication have made increasingly complex and dedicated underwater robot systems a reality. Used in a highly hazardous and unknown environment, the autonomy and dynamics of the robots is the key to mission success. Though the dynamics of underwater vehicle system is highly coupled and non linear in nature, decoupled control system strategy is widely used for practical applications. As autonomous underwater vehicles need intelligent control systems, it is necessary to develop control systems that really take into account the coupled and non-linear characteristics of the system. In this paper, we propose a control system with a nonlinear control strategy that takes into account the above factors. So far, AUV dynamics has often been derived under various assumptions on the motion of the vehicle. However, such assumptions may induce large modelling errors and may cause severe control problems in many practical applications. We propose to use both Lyapunov and state space back stepping based non linear control to overcome the modelling errors. The strategy will be tested through simulations for a flat-fish type AUV. Basic controller design and the simulation results will be discussed in the paper. A comparison of the results for conventional method and the proposed method will also be presented. © 2008 IEEE.

2008 10th International Conference on Control, Automation, Robotics and Vision, ICARCV 2008

Coupled, non-linear control system design for autonomous underwater vehicle (AUV)

Micropipet aspiration of phase-separated lipid bilayer vesicles can elucidate physicochemical aspects of membrane fluid phase coexistence. Recently, we investigated the composition dependence of line tension at the boundary between liquid-ordered and liquid-disordered phases of giant unilamellar vesicles obtained from ternary lipid mixtures using this approach. Here we examine mechanical equilibria and stability of dumbbellshaped vesicles deformed by line tension. We present a relationship between the pipet aspiration pressure and the aspiration length in vesicles with two coexisting phases. Using a strikingly simple mechanical model for the free energy of the vesicle, we predict a relation that is in almost quantitative agreement with experiment. The model considers the vesicle free energy to be proportional to line tension and assumes that the vesicle volume, domain area fraction, and total area are conserved during aspiration. We also examine a mechanical instability encountered when releasing a vesicle from the pipet. We find that this releasing instability is observed within the framework of our model that predicts a change of the compressibility of a pipet-aspirated membrane cylinder from positive (i.e., stable) to negative (unstable) values, at the experimental instability. The model furthermore includes an aspiration instability that has also previously been experimentally described. Our method of studying micropipet-induced shape transitions in giant vesicles with fluid domains could be useful for investigating vesicle shape transitions modulated by bending stiffness and line tension. © 2008 American Chemical Society.

Journal of Physical Chemistry B

Mechanical stability of micropipet-aspirated giant vesicles with fluid phase coexistence

We obtain approximate solutions to the equations that govern the shape of giant unilamellar vesicles (GUVs) with two fluid phases. The equations involve a dimensionless small parameter related to the resistance to changes in its local mean curvature. Asymptotic solutions for the shape are obtained up to and including terms of first order in the small parameter. At this order, we determine a relationship between the tangent angle at the interface and the difference in the Gaussian curvature stiffnesses of the co-existing phases. This relationship demonstrates that a difference in the Gaussian curvature stiffnesses moves the phase boundary away from the neck, as determined in previous numerical studies. The analytical expression for the tangent angle obtained here can be used to determine elastic parameters for the membranes from experimental data. Use of the analytical expression will eliminate the need for the repeated generation of numerical solutions in the estimation of the material parameters. Our analytical solution also reduces the number of measurements needed as inputs for an existing boundary layer analysis. © 2008 Cambridge University Press.

Journal of Fluid Mechanics

A higher-order boundary layer analysis for lipid vesicles with two fluid domains

We investigate the adhesion of vesicles, under the influence of a contact potential, to substrates with various geometry. For axisymmetric configurations, we find that the transition from a free vesicle to a bound state depends significantly on the substrate shape. In general, the critical values of the contact potential at which these transitions take place are lower for a concave-shaped substrate than that for a flat-shaped substrate investigated in earlier studies. We observe that the transitions happen at higher critical values of the contact potential when the substrate is convex and illustrate how these critical values depend on the curvature of the substrate. In addition, we construct an approximate analytical solution that predicts the shape of the vesicle for large internal excess pressure and contact potential. The analytical solution leads to an inequality that relates the surface tension with the contact potential. © 2008 The American Physical Society.

Physical Review E - Statistical, Nonlinear, and Soft Matter Physics

Adhesion of vesicles to curved substrates

The increased need for underwater robotic systems for exploration of underwater resources has resulted in the development of advanced control systems and technologies to overcome the challenging issues of underwater navigation and control. Developing efficient control schemes for underwater robots to maneuver in the constrained environments, overcoming the external disturbances, has been a real challenge to researchers. In this paper, we present an attitude controller for flatfish shaped underwater vehicle as an inner loop controller for trajectory control. Here the vehicle is assumed to be positive buoyant and the pitch angle variations are significant to affect the controller. The controller is designed using robust PID controller scheme and allows easy tuning of the controller, considering nominal performance and robustness as control specifications. The stability of the vehicle is also discussed. Finally, certain numerical studies are also presented to better illustrate the controller behaviour. © 2008 IEEE.

IEEE Region 10 Colloquium and 3rd International Conference on Industrial and Information Systems, ICIIS 2008

Attitude control of flatfish shaped autonomous underwater vehicle

An important rotor fault, which can lead to catastrophic failure if undetected, is fatigue crack in the shaft. The cracked rotor problem received the first attention in 1970, since when the interest among the researchers started. Vibration behavior of cracked structures, in particular cracked rotors, has received considerable attention in the last two decades. The problem of damage and crack detection in structural components has acquired important role in recent years. However, the studies are mainly dealt with single crack. If the structure is cracked in at least two positions, the problem of crack sizing and location becomes decidedly more complex. Relatively few authors have addressed the multi-crack assessment for structures. The objective of this present study is to summarize the different studies on double/multi-cracks and to note the influences, identification methods in vibration structures such as beams, rotors, pipes, etc. And thus this paper brings out the state of the research on multiple cracks effects and their identification. © 2007 Elsevier Ltd. All rights reserved.