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.

&nbsp;

IIT Palakkad

This paper analyses two kinds of models for Mobile robots having two and four independently rotatable power wheel configurations, respectively. Both the models were analysed for performance based on mechanical design and kinematic control aspects. A scissors mechanism was employed on the robots to equip them with weight lifting capabilities which are controlled by a linear actuator. The robot can be used for various purposes including inventory management, shop-floor assistance and warehouse automation. In the end, a simple computed velocity control kinematic model was developed for both the models and results were compared. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

World University root node

Lecture Notes in Mechanical Engineering

Design and Control of Mobile Robots with Two and Four Independent Rotatable Power Wheels

This article implies an improved backstepping control technique for the operational-space position tracking of a kinematically redundant mobile manipulator. The mobile manipulator thought-out for the analysis has a vehicle base with four mecanum wheels and a serial manipulator arm with three rotary actuated joints. The recommended motion controller provides a safeguard against the system dynamic variations owing to the parameter uncertainties, unmodelled system dynamics and unknown exterior disturbances. The Lyapunov's direct method assists in designing and authenticating the system's closed-loop stability and tracking ability of the suggested control strategy. The feasibility, effectiveness and robustness of the recommended controller are demonstrated and investigated numerically with the help of computer based simulations. The mathematical model used for the computer-based simulations is derived based on a real-time mobile manipulator and the derived model is further verified with an inbuilt gazebo model in a robot operating system (ROS) environment. In addition, the proposed scheme is verified on an in-house fabricated mobile manipulator system. Further, the recommended controller performance is correlated with the conventional backstepping control design in both computer-based simulations and in real-time experiments. © 2021 Defense Scientific Information and Documentation Centre. All rights reserved.

Fulltext

Defence Science Journal

Performance investigations of an improved backstepping operational-space position tracking control of a mobile manipulator

The purpose of this study was to develop a closed-loop machine vision system for wire electrical discharge machining (EDM) process control. Excessive wire wear leading to wire breakage is the primary cause of wire EDM process failures. Such process interruptions are undesirable because they affect cost efficiency, surface quality, and process sustainability. The developed system monitors wire wear using an image-processing algorithm and suggests parametric changes according to the severity of the wire wear. Microscopic images of the wire electrode coming out from the machining zone are fed to the system as raw images. In the proposed method, the images are pre-processed and enhanced to obtain a binary image that is used to compute the wire wear ratio (WWR). The input parameters that are adjusted to recover from the unstable conditions that cause excessive wire wear are pulse off time, servo voltage, and wire feed rate. The algorithm successfully predicted wire breakage events. In addition, the alternative parametric settings proposed by the control algorithm were successful in reducing the wire wear to safe limits, thereby preventing wire breakage interruptions. © 2021, Shanghai University and Periodicals Agency of Shanghai University and Springer-Verlag GmbH Germany, part of Springer Nature.

Advances in Manufacturing

Machine-vision-based electrode wear analysis for closed loop wire EDM process control

The present study investigates numerically the conjugate heat transfer in a two-dimensional planar sudden expansion flow. The governing equations are solved using an unstructured solver based on the finite volume method. The results show the effects of Reynolds number, thermal conductivity ratio, Prandtl number and solid slab thickness on the conjugate heat transfer characteristics. The outcome of this study is presented in the form of local Nusselt number, average Nusselt number and interface temperature along the solid-fluid interface. It is observed that for the given range of Reynolds number, i.e. Re ≤ 100 , the fluid flow is found to be symmetric. It is further revealed that the heat transfer increases along the interface with the increase of Reynolds number, thermal conductivity ratio and Prandtl number whereas it decreases with the increase of solid slab thickness. © 2021, The Institution of Engineers (India).

Journal of The Institution of Engineers (India): Series C

Numerical Analysis of Conjugate Heat Transfer in a Planar Sudden Expansion Flow

Metal additive manufacturing (AM) is gaining momentum among modern manufacturing techniques due to its flexibility in fabricating complex shaped components with minimum scrap. However, the technology cannot be directly employed in producing parts on a larger scale because of the poor surface integrity and average mechanical properties. This highlights the importance of post processing AM components with suitable methods that can overcome these limitations. The existing finishing methods for AM components such as laser polishing, chemical polishing, abrasive finishing, mechanical polishing and other hybrid combinations have their own limitations. Difficulty in accessing complex part surfaces, loss of dimensional accuracy and deterioration in material surface and properties are some of the major challenges related to existing finishing methods. In the present work, wire electrical discharge polishing (WEDP) technique has been proposed in improving the surface integrity and mechanical properties of metal AM components. Experiments were carried out on selective laser melted (SLM) stainless steel (SS316 L) specimens at different settings of pulse duration and servo voltage. A detailed investigation into surface finish and morphology was performed to determine the enhancement in surface integrity after WEDP. In addition, investigations were conducted to evaluate the improvement in mechanical properties such as microhardness and tribological performance. The irregularities/defects over the SLM surface were removed and a maximum finish of 0.739 μm was achieved. A negligible amount of wire material was migrated to the SS316 L workpiece surface after WEDP process. Moreover, reduction in crystallite size and microstrain was obtained based on results from XRD analysis. Martensite formation and shift in peaks were also evident from XRD pattern after WEDP process. An increase in microhardness (∼ 317 HV) at the subsurface and reduction in coefficient of friction (∼ 0.35) were also achieved. Based on aforementioned results, WEDP showed excellent capability in improving the surface integrity and mechanical properties thereby providing a promising hybrid option for combining with metal AM technology. © 2020 Elsevier B.V.

Journal of Materials Processing Technology

Improving the surface integrity and mechanical properties of additive manufactured stainless steel components by wire electrical discharge polishing

4th World Congress on Micro Nano Manufacturing (WCMNM)

Surface micro-layer modification of selectively laser melted TiAl alloy using wire electrical discharge polishing

This work discusses the development of a sharp interface immersed boundary (IB) method for viscous compressible flows and its assessment for accurate computations of wall shear and heat fluxes in hypersonic flows. The IB method is implemented in an unstructured Cartesian finite-volume (FV) framework and resolves the geometric interface sharply on the nonconformal mesh through direct imposition of boundary conditions employing a local reconstruction approach. The efficacy of the IB-FV solver is investigated for canonical high-speed viscous flows over a range of Mach numbers. The numerical results indicate that the surface pressure and shear stress distributions are computed with reasonable accuracy, whereas surface heat fluxes for aerodynamically blunt configurations are underpredicted. Employing a set of carefully designed experiments and simple diagnostic tools, we probe the possible causes for the underprediction in heat flux. We show that there exist two sources of error - one due to grid resolution and the other due to solution reconstruction, with the latter being more prominent and responsible for the observed underprediction in heat fluxes. Studies reveal that the heat flux estimates are sensitive to the choice of temperature reconstruction and linear interpolations could lead to poor estimates of heat flux. Our investigations conclusively point out the fact that existing polynomial-based reconstruction approaches for sharp interface IB techniques are not necessarily adequate for heat transfer predictions in high Reynolds number hypersonic flows. © 2021 American Physical Society.

Physical Review E

Role of solution reconstruction in hypersonic viscous computations using a sharp interface immersed boundary method

Metal powders are often made by gas atomization of liquid metal. During the process, liquid metal which flows from a melt delivery tube (MDT) is atomized by high speed gas discharging from a gas nozzle. In this work, the effect of the melt delivery tube position on atomization outcomes such as the yield, mass median diameter and spread of the particle size distribution, is studied experimentally. A melt atomization setup (pilot-scale) is used to produce tin powder by gas-atomization. Three MDT positions, namely, intruded, extruded and flush with respect to the gas nozzle, are chosen for this study. Three pressure regimes (atmospheric, aspiration and pressurization) are established by varying the relative distance between the MDT and the gas nozzle exit for the three positions. Experimental investigations revealed that the intruded position produces powder with lower mean particle sizes and lower spread than the extruded configuration. The intruded position also gives a significantly higher yield compared to the extruded and flush positions at low gas flow rates and hence appears to be the most suited for metal atomization using a free-fall configuration. © 2021 The Society of Powder Technology Japan

Advanced Powder Technology

Experimental investigation on the effect of melt delivery tube position on liquid metal atomization

This paper proposes a lying/sitting type lower-limb rehabilitation robot based on a three degrees of freedom spatial parallel kinematic manipulator namely “The Orthoglide” along with an actuated rotational degree of freedom at the end-effector for the purpose of lower-limb rehabilitation treatments. This rehabilitation robot is an end-effector/foot-plate based mechanism which controls the ankle-joint movements to assist physiotherapists in performing therapeutic treatments along with a passive orthosis (supporting system). The conceptual and detail design of the rehabilitation device is presented along with its kinematics. Further, the functional validation of the proposed robot in terms of the kinematic motion capabilities to provide physiological motions like knee flexion-extension, hip adduction-abduction and hip flexion-extension are also investigated. The required safety features for the proposed rehabilitation robot in terms of mechanical constraints and non-actuated joints are also discussed. © 2021, Springer Nature Singapore Pte Ltd.

A New Sitting-Type Lower-Limb Rehabilitation Robot Based on a Spatial Parallel Kinematic Machine

This research work emphasizes the equations of motion of a ground-based vehicle-manipulator system that constitutes of a spatial six degree of freedom serial manipulator and is modelled considering the dynamic coupling and other effects. Subsequently, a robust double-loop motion control scheme is applied for the end effector trajectory tracking of the vehicle-manipulator system. Simulation experiments based on real-time system parameters are accomplished to elucidate the essence of the recommended control scheme. The outcomes of this work emphasize that the proffered motion control scheme is suited to the similar kinematically redundant robotic systems and is effective even in the existence of unknown external disturbances and system uncertainties. © 2021, The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.