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

A "Hybrid"vehicle is one that has the potential to operate in more than one environment. This work demonstrates a robust backstepping control algorithm for the autonomous transmedia operation of a hybrid unmanned aerial-underwater vehicle in the presence of uncertainty. The simplified mathematical model is considered to depict the entire controller design procedure. The numerical simulation is carried out to demonstrate the proposed control system's efficiency and compare it to existing PID control. The vehicle's transient behaviour is compared in six different transmedia manoeuvres between air and water. The suggested control system is evaluated for stability in aerial manoeuvres and transmedia manoeuvres with respect to the conventional PID algorithm in the MATLAB-Simulink environment to demonstrate the superiority of the proposed algorithm. © 2023 ACM.

World University root node

ACM International Conference Proceeding Series

Modelling and Robust Control of Hybrid Unmanned Aerial-Underwater Robot in the Presence of Uncertainty

Aluminium matrix composites (AMCs) have found widespread applications in automobile, aerospace and marine industries because of their attractive properties. These include good strength to weight ratio, better corrosion and fatigue resistance. Stir casting has been identified as the most suitable method to fabricate AMCs because it provides good matrix-reinforcement bonding while also being a cost-effective process for mass production. However, this process suffers from drawbacks that include cast porosity, less wettability and agglomeration of reinforcement particles. A means to overcome these disadvantages is the use of acoustic cavitation using ultrasonic vibrations which can scatter the agglomerated particles and creates a uniform distribution of particles through acoustic streaming. Since the effect of ultrasonic cavitation is extremely localized, it is often combined with stir casting method to leverage the advantages of both approaches while negating their respective demerits. This hybrid approach known as Ultrasonic Assisted Stir Casting can be used to fabricate AMCs with better mechanical properties. The regions of cavitation as well as acoustic streaming in this process are strongly influenced by parameters such as power, wave frequency and container geometry which directly impact the performance characteristics of the process. In this work, we numerically investigate the influence of acoustic parameters and geometry of the processor container on cavitation regions and acoustic streaming. Simulation results showed that the cavitation region is concentrated near to the sonotrode and the acoustic streaming results in a circulating flow within the processor container.The analysis of cavitation zones and streaming patterns in these preliminary studies without reinforcement particles is expected to provide insights to optimize the acoustic parameters for uniform distribution of particles. © 2023 Author(s).

AIP Conference Proceedings

Numerical investigation of ultrasonic cavitation in stir cast aluminium matrix melt composites

Selective laser melting (SLM) is a widely used additive manufacturing technique in which parts are made by melting a material layer by layer. SLM can be used to make complex parts with good mechanical properties. However, a large temperature gradient due to localized heating and cooling of the powder results in residual stress and deformation. Scan strategy is an important parameter that can reduce residual stress as it is directly related to the formation of temperature gradient during the process. Scan vector length, scan rotation angle, scan pattern, scan vector orientation and hatch distance are the major parameters involved in scanning. In this study, a 3D thermo-mechanical coupled numerical model is created to analyze the effect of scanning strategy on residual stress of SLM 316L steel parts. Thermal characteristics of the SLM process are modeled by considering a moving Gaussian heat source and advection-diffusion transport equations are solved along with phase change and mass conservation to obtain the temporal evolution and spatial distribution of temperatures in the manufactured component during the whole process. The obtained temperature history is fed into the mechanical model to estimate the distribution of residual stress over the entire domain. The mentioned methodology is used to perform preliminary numerical simulations for a process involving the fabrication of a component with eight layers by using a stripe scanning strategy and 30° scan rotation angle. The modeling results show that the residual stress in the Z (out of plane) direction is less than that in the other two directions. Also the residual heat which exists in the previous tracks and layers lead to the formation of larger melt pool in the subsequent layers, and the parts with the highest temperature have the minimum equivalent stress. Equivalent stress profile also shows that compressive stresses are formed at the edges and four corners of the part while tensile stress is formed at the center of the part. © 2023 Author(s).

Effect of laser scanning strategy on residual stress in selective laser melting

Laser shock peening (LSP) is a novel non-contact surface modification technique to enhance the corrosion and compression behavior of stainless steel 308L (SS308L) material for a cryogenic application. SS308L is commonly used as a weld filler, weld electrode and cryogenic environment due to its low carbon content and good mechanical and high corrosion resistance properties. In this present study, wire-arc additive manufacturing (WAAM) has been utilized to manufactured SS308L material and studied the compression, corrosion, wettability and surface properties of the material. Further, the nanosecond laser shock peening has been utilized to modify the additive-manufactured SS308L surface and mechanical properties. From the experimental results, it has been observed that the uni-directional flow path (UDFP) deposition has better corrosion resistance wettability and surface finish than the bi-directional flow path (BDFP) deposition on wire-arc additive-manufactured SS308L material due to its more uniform microstructure and smoother surface finish. In addition, the post-processing treatment (LSP) of SS308L materials has improved the compressive strength of additive-manufactured SS308L material with 20.6 and 15.9% as compared to UDFP and BDFP due to grain surface refinement and increases in dislocation density. The corrosion rate of LSP-treated materials was reduced by 20.7% compared to the UDFP materials due to the higher corrosion potential and lower corrosion current density. The higher surface roughness has produced better passive film formation to enhanced corrosion resistance in the UDFP with LSP. Finally, the microstructure and chemical composition have been analyzed using scanning electron microscope and energy-dispersive x-ray spectroscopy. Graphical Abstract: [Figure not available: see fulltext.]. © 2023, ASM International.

Journal of Materials Engineering and Performance

Post-processing of Wire Arc Additive Manufactured Stainless Steel 308L to Enhance Compression and Corrosion Behavior using Laser Shock Peening Process

Laser powder bed fusion (LPBF) process is used for fabricating complex geometries of metallic parts ranging from macro to micro size. Fabrication of a part with various curvature angles is always a great challenge due to variation in the deposition of material at the curvature. The process parameters of contour exposure of the printing part play an important role in geometrical accuracy. Hence, In this study, the contour of various curvatures (30 ∘, 60 ∘, 90 ∘, &amp; 120 ∘) is analyzed for various laser power and scanning speed. It is found that track width at the curvature is increased from 17 % to 160 % on decreasing the angle between tracks from 120 ∘ to 30 ∘ compared to the width at the track. The variation in width at curvature and track is occurred due to an increase in supplied energy because of deceleration and acceleration of the laser source at the curvature. Further, the width at the curvature gets wider during the subsequent layer deposition and increases with linear energy density due to remelting and spreading at the curvatures. © 2023, The Author(s), under exclusive licence to Springer Nature Switzerland AG.

Progress in Additive Manufacturing

Study on track width of various curvature angles in laser powder bed fusion deposition

This paper presents a novel framework for a robust motion control scheme of an eight-thruster underwater vehicle. It combines a model-free approach intertwined with a model-based approach such as sliding mode control (SMC) to counter the unknown disturbances and decouple them to provide better tracking. A proportional-integral (PI) control-like structure is taken as the first sliding surface. A proportional derivative (PD) control-like structure is proposed as the second sliding surface for trajectory tracking. This motion control works for any fully actuated or over-actuated vehicle. Initially, the dynamic model and vehicle configuration are presented. Then the vehicle’s closed-loop behavior is studied in the presence of underwater currents. Later, the study considers external disturbances and compensates them with the help of a nonlinear disturbance observer. Lyapunov’s direct method and Barbalat’s lemma ensure the asymptotic convergence of tracking errors. The proposed controller performance is evaluated using a detailed comparison study with different model-free and model-based controllers from the literature. Later, the control scheme’s effectiveness is demonstrated numerically with the help of computer-based simulations. The robustness against the parameter uncertainties, underwater currents, and unknown disturbances is also presented. © 2023, The Author(s), under exclusive licence to Springer Nature B.V.

Journal of Intelligent and Robotic Systems: Theory and Applications

Robust Motion Control of Fully/Over-Actuated Underwater Vehicle Using Sliding Surfaces

Parallel kinematic machines (PKMs) whose moving platforms realises one-translational and two-axes rotation (1T2R) motion pattern, find a wide variety of applications. However, a majority of the 1T2R PKMs suffer from singularities and parasitic motions. Higher dexterity requirements further constrict its already limited workspace volume. This paper introduces a novel 1T2R parallel mechanism to address typical issues in dexterity, singularities, and parasitic motions. The mathematical modelling covers a comprehensive analytical inverse kinematics modelling. The analyses performed evaluate mobility, singularities, and dexterity of the mechanism. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.

Mechanisms and Machine Science

Conceptual Design and Kinematic Analysis of a 1T2R Parallel Manipulator

This paper presents a detailed design of a skid-steering mobile platform with four wheels, along with a Cartesian serial (PPP) manipulator. The aim of this design is to enable the platform to perform various tasks in the agricultural process. The parallel manipulator designed can handle heavy materials in the agricultural field. An experimental robotic harvesting scenario was conducted using parallel manipulator-based end-effectors to handle heavy fruits such as watermelon or muskmelon. The conceptual and component design of the different models was carried out using the Solidworks modeling package. Design specifications and parametric values were utilized during the manufacturing stage. The mobile manipulator was simulated on undulating terrain profiles using ADAMS software. The simulation was analyzed for a duration of 15 s, and graphs depicting the distance, velocity, and acceleration were evaluated over time. Proportional derivative control and proportional derivative-like conventional sliding surface control were applied to the model, and the results were analyzed to assess the error in relation to the input and desired variables. Additionally, a structural analysis was performed to ensure minimal deformation and the highest safety factor for the wheel shaft and L bracket thickness. Throughout the fabrication and prototype development, calibration tests were conducted at various X-, Y-, and Z-axis frame mounting stages. The objective was to minimize the lateral and longitudinal deviation between the parallel linear motion (LM) rails. Once the fabrication and prototype construction was completed, field testing was carried out. All mechanical movements in the lateral and longitudinal directions functioned according to the desired commands given by the Arduino Mega, controlled via a six-channel radio frequency (RF) controller. In the context of agriculture, the grippers utilizing parallel mechanisms were also subjected to testing, demonstrating their ability to handle sizable cylindrical and spherical fruits or vegetables, as well as other relevant objects. © 2023 by the authors.

Machines

Designing and Implementing a Versatile Agricultural Robot: A Vehicle Manipulator System for Efficient Multitasking in Farming Operations

Calcium is a ubiquitous molecule and second messenger that regulates many cellular functions ranging from exocytosis to cell proliferation at different time scales. In the vasculature, a constant adenosine triphosphate (ATP) concentration is maintained because of ATP released by red blood cells (RBCs). These ATP molecules continuously react with purinergic receptors on the surface of endothelial cells (ECs). Consequently, a cascade of chemical reactions are triggered that result in a transient cytoplasmic calcium (Ca2 +), followed by return to its basal concentration. The mathematical models proposed in the literature are able to reproduce the transient peak. However, the trailing concentration is always higher than the basal cytoplasmic Ca2 + concentrations and the Ca2 + concentration in endoplasmic reticulum (ER) remains lower than its initial concentration. This means that the intracellular homeostasis is not recovered. We propose, herein, a minimal model of calcium kinetics. We find that the desensitization of EC surface receptors due to phosphorylation and recycling plays a vital role in maintaining calcium homeostasis in the presence of a constant stimulus (ATP). The model is able to capture several experimental observations such as refilling of Ca2 + in the ER, variation of cytoplasmic Ca2 + transient peak in ECs, the resting cytoplasmic Ca2 + concentration, the effect of removing ATP from the plasma on Ca2 + homeostasis and the saturation of cytoplasmic Ca2 + transient peak with increase in ATP concentration. Direct confrontation with several experimental results is conducted. This work paves the way for systematic studies on coupling between blood flow and chemical signaling and should contribute to a better understanding of the relation between (patho)physiological conditions and Ca2 + kinetics. © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.

Biomechanics and Modeling in Mechanobiology

Mathematical modeling of intracellular calcium in presence of receptor: a homeostatic model for endothelial cell

Different thruster configurations (TCs) or arrangements are used in underwater vehicles (UVs) to perform various deep-sea intervention operations. The location and arrangement of thrusters and the number of thrusters can vary the overall vehicle's performance. However, a comparison study of the effect of these different TCs or performances is yet to be available in the literature. This study will provide a base for the vehicle design and choice of thruster along with their arrangements. Therefore, in this paper, computer-based numerical simulations are conducted with these TCs using eight identical thrusters on a common vehicle platform to analyze their relative performances under different operating conditions. The performance parameters studied in this paper are position error, orientation error and energy consumed. Initially, the maximum allocated force and moments in the vehicle's fixed frame are found by giving a constant input force to the thrusters. Then the TCs are simulated with closed-loop trajectory tracking tasks of following simple to complex profiles to identify the configurations that better perform tracking the given desired trajectories. Several computer-based simulations are conducted in the presence of underwater currents. Vectored horizontal TC (inclined to surge and sway axis) and 3D vectored TCs consume more energy than horizontal and vertical TCs. Energy consumption in horizontal and vertical TC is found to be 30 % and 23 % lesser than 3D vectored TC in the absence and presence of underwater currents, respectively, for the same trajectory tracking simulation. © 2023 Elsevier Ltd

Ocean Engineering

Comparative performance investigations of the intervention-class underwater vehicle with different possible thruster configurations using eight identical thrusters