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

Control and guidance of Autonomous Underwater Vehicle (AUV) is tedious process as it is an underactuated model where the numbers of inputs to the actuator are less than the number of degrees-of-freedom to be controlled; also the dynamics of AUV is affected by internal interruptions like sensor noise and exterior distractions namely hydrodynamic effects and ocean current. The difficulty of uncertainty in the vehicle dynamics can be handled by adaptive control, chosen based on its clarity using conventional controller like Proportional-Integral-Derivative (PID) and also by intelligent Fuzzy Logic Control (FLC). To increase the quality of these autonomous systems, model-based control strategies such as Internal Model Control (IMC) and Model Predictive Control (MPC) has been focused in this paper. The control operation includes motion planning and trajectory generation tasks which provide the desired vehicle depth location as a function of time and subsequently the controller determines required stern angle position, based on the sensor measurements. The comparative result shows that Model based control strategies exhibits better performance than the classical controls. © 2016 IEEE.

World University root node

OCEANS 2016 - Shanghai

Relative analysis of controller effectiveness for vertical plane control of an autonomous underwater vehicle

This paper presents a comparative analysis of three degrees of freedom planar parallel robotic manipulators (x, y and θz motion platforms) namely 2PRP-PPR, 2PRR-PPR, 3PPR (Hybrid), 3PRP (Hephaist) and 3PPR U-base in terms of optimal kinematic design performance, static structural stiffness and dynamic performance (energy and power consumption). Kinematic and dynamic performance analyses of these platforms have been done using multibody dynamics software (namely ADAMS/View). Static stiffness of the above-mentioned manipulators have been analysed, compared using the conventional joint space Jacobian stiffness matrix method, and this method has been verified through a standard finite-element software (namely NASTRAN) as well. The size of the fixed base or aspect ratio (width/height) can be varied for various working conditions to understand its design parameters and optimal design aspects which are depending on the fixed base structure. Different aspect ratios (fixed base size) are considered for the comparative analyses of isotropy, manipulability and stiffness for the above-mentioned planar parallel manipulators. From the numerical simulation results, it is observed that the 2PRP-PPR manipulator is associated with a few favourable optimum design aspects such as singularity-free workspace, better manipulability, isotropy, higher stiffness and better dynamic performance in terms of power and energy requirement as compared to other planar parallel manipulators. © 2016 Taylor & Francis and The Robotics Society of Japan.

Advanced Robotics

Performance investigations on optimum mechanical design aspects of planar parallel manipulators

Inconel 706 is a recently developed superalloy for aircraft application, particularly in turbine disk which is among the most critical components in the gas turbine engines. Recently, wire electrical discharge machining (WEDM) attained success in machining of gas turbine components which require complex shape profiles with high precision. To achieve the feasibility in machining of these components, the research work has been conducted on Inconel 706 superalloy using WEDM process. And, the effect of different wire materials (i.e., hard brass wire, diffused wire, and zinc-coated wire) on WEDM performance characteristics such as cutting speed, surface topography, surface roughness, recast layer formation, residual stresses, and microstructural and metallurgical alterations have been investigated. Even though, zinc-coated wire exhibits improved productivity, hard brass wire was found to be beneficial in terms of improved surface quality of the machined parts. Additionally, lower tensile residual stresses were obtained with hard brass wire. However, diffused wire has a moderate effect on productivity and surface quality. Under high discharge energy, higher elemental changes were observed and also the white layer was detected. © 2016, ASM International.

Journal of Materials Engineering and Performance

Effect of Wire Material on Productivity and Surface Integrity of WEDM-Processed Inconel 706 for Aircraft Application

Grinding nowadays is extensively used for machining of superalloys. Inconel 718 is a Ni-based superalloy which is known as difficult to grind material (DTG) due to its inherent properties like high hardness, high hot strength, severe strain hardening and low thermal conductivity. In the present work, grindability of Inconel 718 using conventional abrasive grinding wheels has been experimentally explored. Ground surfaces have been characterized after grinding with silicon carbide (SiC) and alumina (Al2O3) wheels under dry condition. Surface integrity of the ground product has been studied using surface characterization techniques like Energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Further, the surface behavior of the ground surface has been investigated using microscopic images, micro-hardness tests, and surface roughness measurements. The major conclusion of the present work is that Inconel 718 can be ground more efficiently using alumina grinding wheels compared to the SiC grinding wheel. In the case of SiC wheel, it has been found that the severe attritious wear of the wheel took place primarily due to the chemical reaction between SiC grits and workpiece material at a higher grinding temperature. The mechanism for such attritious wear has been studied, and it appears to be a dissociation of SiC at higher temperature. © 2015 The Society of Manufacturing Engineers.

Journal of Manufacturing Processes

An investigation on surface burn during grinding of Inconel 718

Sound radiation from a rectangular, baffled and perforated piston vibrating harmonically is investigated in the two dimensional wavenumber domain. The perforations are in the form of an array of uniformly distributed circular holes. Perforation ratios in the piston and the baffle are independently chosen and this generalization is later used to represent a more practical case of a perforated piston fixed in an unperforated baffle. It is found that there exists a 'coupling' of the different wavenumbers of the spatially averaged fluid particle velocity field. Analytical expressions for the radiated power and the radiation efficiency are derived in an integral form. The results are presented and compared with those from a finite element solver (COMSOL). The COMSOL results are different due to dissimilar perforate impedance and flow continuity models adopted in their solver. The effect of the perforation ratio on the radiation efficiency of a perforated piston is also discussed.

a 2-D Wavenumber Domain Formulation for the Radiation Efficiency of a Perforated Piston Fixed in a Baffle With an Arbitrary Perforation Ratioc

This paper addresses a robust tracking control of an autonomous underwater vehicle-manipulator system (UVMS) based on terminal sling mode control in task space along with a disturbance observer. The effectiveness of the proposed scheme is demonstrated using numerical simulations having a serial planar manipulator (two rotary joints) on an underwater vehicle in a horizontal plane. An inverse dynamic solution for the system is obtained using the Newton-Euler method incorporating hydrodynamic and dynamic coupling effects. Performance of the proposed scheme is compared under various control schemes and demonstrated numerically for a predefined trajectory of the end effector (in task space). © 2015 ACM.

ACM International Conference Proceeding Series

A robust task space position tracking control of an underwater vehicle manipulator system

This paper proposes a modular lightweight three degrees of freedom (DOF) vertical planar parallel robotic manipulator with a singularity free working region and that which is partially decoupled. It also addresses the inverse dynamics of the proposed manipulator supported by a robust sliding mode control along with an active disturbance compensation which has been improvised for the proposed vertical planar parallel robotic manipulator in the presence of parameter uncertainties and external disturbances. Disturbance vector comprising of disturbances due to the system dynamic variations namely payload and parameter variations, frictional effects and other additional (unmodelled) effects have been estimated and compensated through the disturbance observer. To demonstrate the effectiveness of the proposed controller, simulations and experiments with a desired characteristic trajectory are performed and, the proposed controller performances have been compared with traditional controllers and recent developed controllers to illustrate the usefulness and efficacy of the proposed controller. © 2015 Elsevier Ltd. All rights reserved.

Mechanism and Machine Theory

Inverse dynamics and robust sliding mode control of a planar parallel (2-PRP and 1-PPR) robot augmented with a nonlinear disturbance observer

In the dynamic analysis of rotors supported on journal bearings, Reynolds equation is solved at each time step. In the present work, Reynolds equation is solved using pseudospectral method to estimate fluid film forces. Fluid pressure is approximated by a finite number of Chebyshev polynomials along the bearing length and Fourier series along the bearing circumference. Fluid domain is reduced to a finite set of algebraic equations with pressure at specific grid points as variables using collocation method. Unlike in finite element method (FEM), spectral method uses higher order global basis functions which guarantee high accuracy and lower computational time. A comparison study of fluid film forces for a bearing geometry with an L/D ratio of 0.25 with short bearing theory, solution of Reynolds equation using FEM and pseudospectral method (PSM) is presented. Two different elements are studied in FEM: 3 node triangular element and 9 node quadrilateral element. Computational time taken for one time pressure calculation is also compared. Pseudospectral method is found to be efficient than FEM for a converged solution. © Springer International Publishing Switzerland 2015.

Mechanisms and Machine Science

Dynamic analysis of rotors supported on journal bearings by solving reynolds equation using pseudospectral method

An experimental investigation on forced response of a first stage compressor mistuned bladed disc rotor is performed in an operational aero-engine. It is desired to evaluate the maximum blade amplitude response of the bladed disc for the existing blade mistuning pattern depending on blade mode, exciting engine order, and aerodynamic influences. Finite element analysis on a single cantilever blade is performed and the possible resonances are estimated. Bench tests on a stand-alone blade are conducted to verify the finite element predictions. Experiments are conducted on a full-scale core engine using blade tip timing system. Blade tip timing system utilizes noncontacting sensors installed on the engine casing which provides vibration responses of all the blades in a rotor. The vibration responses obtained from blade tip timing system is validated using simultaneously measured strains from a few blade-mounted strain gages. A good correlation is observed between the predicted and measured blade responses. The effect of blade mistuning on the amplitude resonant response of the bladed disc is explored experimentally. It is observed that the maximum amplitude response of the blades due to forced resonant excitation is far below the fatigue limits for the prevailing blade mistuning pattern. The present exercise of quantifying the blade resonant responses through efficient implementation of the blade tip timing system is crucial to understand and thus avoid high-cycle fatigue, which is one of the most serious problems in aero-engine development. © IMechE 2015.

Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering

Experimental investigation on forced response of mistuned bladed disc rotor in an aero-engine

Vapour bubble growth in film boiling occurs as a result of the increase in disturbances at the liquid vapour interface. Increase in heat flux stimulates these disturbances with the included effects of buoyancy and capillary forces acting at the interface. The present report is focussed on the analysis of the effect of electrohydrodynamics (EHD) on the heat transfer rate and bubble behaviour in saturated film boiling with different wall superheat. The analysis is done with the increasing electric field intensity to observe the space averaged Nusselt number variation and the growth rate of the interface. The destabilizing nature of the electric field force results in the faster rate of bubble release with decreasing distance between adjacent bubbles which verify the decrease in the critical wavelength of disturbance. Combined level-set and volume of fluid (CLSVOF) technique is utilized to capture the liquid-vapour interface. © 2021, Begell House Inc. All rights reserved.