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

This study aims to create an image processing algorithm that categorises the wire electric discharge machine (WEDM) processed finish cut surfaces, based on surface microdefects. The algorithm also detects the defect locations and suggests alternate parameter settings for improving the surface integrity. The proposed automated analysis is more precise, efficient and repeatable compared to manual inspection. Also, the method can be used for automatic data generation to suggest parameter changes in closed loop systems. During the training phase, mean, standard deviation and defect area fraction of enhanced binary images are extracted and stored. The training dataset consists of 27 WEDM finish cut surface images with labels, ‘coarse', ‘average' and ‘smooth'. The trained model is capable of categorising any machined surface by detecting the microdefects. If the machined surface image is not classified as a smooth image, then alternate input parameter settings will be suggested by the model to minimise the microdefects. This is done based on the Euclidean distance between the current image datapoint and the nearest ‘smooth' class datapoint.

World University root node

Journal of Micromanufacturing

Image processing algorithm for detection, quantification and classification of microdefects in wire electric discharge machined precision finish cut surfaces

In a recently published work (Sheng, 2020), Sheng identified inconsistencies in the concepts and principles leading to the Navier–Stokes equations and proposed a new asymmetric “friction tensor” to resolve these inconsistencies. We show that this friction tensor can be interpreted as the non-isotropic part of a vorticity-influenced viscous stress tensor following the analysis in Berdahl and Strang (1986). The asymmetric stress tensor however violates the principles of mechanical equilibrium in fluid flows that are free of external or body couples and is therefore non-physical in classical continuum hydrodynamics. We refute the arguments in favour of the asymmetric stress tensor in Sheng (2020) whilst also demonstrating that the friction tensor leads to the incorrect form of the Navier–Stokes equations in non-Cartesian co-ordinates and its ability to recover the correct governing equations in Cartesian co-ordinates is fortuitous. © 2020 Elsevier Masson SAS

European Journal of Mechanics, B/Fluids

Critique on “A revisit of Navier–Stokes equation”

Additive manufacturing has advantages of fabricating complex parts at very greater speed with complete freedom for designer. LENSTMis an additive manufacturing that uses 3D CAD model for depositing metal products directly from metal powder. The effect of process parameters like Laser Power, Scan speed, powder flow rate and working distance on Porosity, instrumented Vickers Hardness and Bulk Hardness Top and Bottom layers for LENSTMdeposited components were investigated and the values are compared with wrought alloy. The density and Hardness obtained from LENSTMSamples are Higher than that of Conventional Methods. The Laser Power was significant factor according to Taguchi Analysis. © 2021 Elsevier Ltd. All rights reserved.

Materials Today: Proceedings

Effect of process parameters on micro hardness, bulk hardness and porosity of LENSTMdeposited SS 316L alloy

A simple computational model was created to predict the vaporization rates of droplets of urea-water-solution (UWS) evaporating in a hot air stream. A single-component evaporation model, which was based on Abramzon-Sirignano's vaporization model, was adapted to handle UWS droplets and the governing equations were solved numerically in MATLAB®. The temperature and species concentrations within the droplet were assumed to be uniform and various methods available in literature were employed to estimate important thermophysical properties such as saturation vapor pressures, partial pressures, vaporization enthalpy and vapor diffusivities. The suitability and limitations of the computational model were assessed by comparing the results with experimental data on UWS droplets evaporating under forced convective conditions. The temperatures considered in this study ranged from 373 K to 673 K and the corresponding relative air velocities were between 1.5 m/s and 4.3 m/s. The model was found to be able to capture the two-stage vaporization behavior of the UWS droplet (except crystallization, puffing and micro-explosion) with reasonable accuracy. While the first-stage vaporization rates, predicted by the model, were accurate to within 1.8% to 17.7%, the accuracies of the second-stage vaporization rates were significantly dependent on the methods used to estimate fluid properties such as the vapor pressures and the vaporization enthalpy. © 2020 Elsevier Ltd

International Journal of Heat and Mass Transfer

A computational model for the evaporation of urea-water-solution droplets exposed to a hot air stream

The conceptual design of a new sitting-type lower-limb rehabilitation robot along with simplified motion control for its passive range of motion therapies is put forth here. The suggested system’s design is demonstrated and verified using computer-based numerical simulations. For this, the desired motion trajectory is generated with the help of a clinically obtained gait data-set. The robustness of the proposed simplified motion control scheme is verified with the variation of the physical parameters of the patients’ limb. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2020.

Mechanisms and Machine Science

Conceptual Design and Control of a Sitting-Type Lower-Limb Rehabilitation System Established on a Spatial 3-PRRR Parallel Manipulator

This paper considers a resolved kinematic motion control approach for controlling a spatial serial manipulator arm that is mounted on a vehicle base. The end-effector's motion of the manipulator is controlled by a novel kinematic control scheme, and the performance is compared with the well-known operational-space control scheme. The proposed control scheme aims to track the given operational-space (end-effector) motion trajectory with the help of resolved configuration-space motion without using the Jacobian matrix inverse or pseudo inverse. The experimental testing results show that the suggested control scheme is as close to the conventional operational-space kinematic control scheme. © 2020, DESIDOC

Fulltext

Defence Science Journal

Simplified motion control of a vehicle-manipulator for the coordinated mobile manipulation

Intervention-class autonomous underwater vehicles (AUVs) have to execute complex tasks such as underwater inspection and manipulating objects which demand high manoeuvrability along with good stability. Due to these contrasting capabilities, often the vehicle control activity demands high actuator outputs with almost zero time response. This condition leads to actuator saturation and limits the vehicle response to the control inputs. Another factor to be considered is the thrusters hydrodynamic constraints during propulsion which results in a highly nonlinear and coupled equations of motions. This forms the basic motivation to design a suitable nonlinear control methodology by considering the empirical data based thrust modelling, drag effects of the propulsion, and interaction effects of the external appendages and the hull of the vehicle. The capability of the proposed control strategy is evaluated by implementing a trajectory tracking problem. The simulation results prove the capability of the proposed control strategy to execute complex tasks in the presence of actuator saturation and hydrodynamic constraints. © 2020 IEEE.

2020 Global Oceans 2020: Singapore - U.S. Gulf Coast

Control of a vectorial propulsion underwater vehicle considering thruster hydrodynamics constraints and actuator saturation

Complex and interactive robot manipulation skills, such as playing a game of table tennis against a human opponent, are a novel problem with multifaceted challenges. Accurate dynamic trajectory generation in order to respond to the tennis ball from the opponent and a novel control scheme for robust and high-performance tracking of the ball in such dynamic situations is a prerequisite to winning the game. In this paper, the dynamic movement primitives (DMPs) are employed for the stable generation of dynamic trajectories in the presence of environmental uncertainties such as ball position and velocity, opponent position and velocity and so on. In DMP, kernels parameters need to be found from expert demonstrations using a learning technique. To mitigate environmental uncertainties by accurate reconstruction of novel dynamic trajectories by combining multiple DMPs, we propose a piecewise linear canonical system (PLCS)-based modified DMP in contrast to the standard exponential canonical system (ECS)-based DMP. To enhance effectiveness and performance, a novel learning technique based on Lyapunov stability is embedded with the above-developed formulation. We show that the proposed learning technique is faster, has the best steady state error performance, and requires almost half the kernels than the state of the art. Next, to intercept the dynamic moving ball in real-time using the DMP, a novel control scheme is needed and designed using fuzzy fractional order sliding mode control. The control scheme results in chatter free tracking of the desired trajectories because the control law is free from sgn( cdot ) function. The tracking control performance is guaranteed theoretically via the Lyapunov approach and also verified through simulations and experiments. Finally, we have developed a complete system (including a vision system for tracking the ball) using a real 4 degrees-of-freedom (DOFs) Barrett Wam robotic arm and show that the proposed overall framework is able to respond to a hanging ball with high accuracy. © 1993-2012 IEEE.

IEEE Transactions on Control Systems Technology

Dynamic Trajectory Generation and a Robust Controller to Intercept a Moving Ball in a Game Setting

The article describes the structure of the lower limb rehabilitation system based on serial RRRR mechanism as a passive orthosis and an active parallel 3-PRRR mechanism. A mathematical model of the kinematics of the RRRR mechanism is presented. A description of a numerical method for determining the workspace of the RRRR mechanism based on the approximation of solutions of nonlinear inequalities systems to provide the required rotation angles in joints for rehabilitation is considered. A calculation algorithm, a software, and a visualization system for export the three-dimensional workspaces in STL format are synthesized. The results of mathematical modeling and analysis of the results are presented. © 2020, The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG.

A numerical method for determining the workspace of a passive orthosis based on the rrrr mechanism in the lower limb rehabilitation system

Cryogenic machining is one of the emerging manufacturing techniques in the field of metal cutting industries due to the new stringent environmental regulations in terms of utilization and disposal of chemically contaminated conventional coolants. The method of supply of cryogenic coolants at the machining zone significantly influences the machined product functional performance. In this context, it is necessary to understand the turning process performance under various methods of cryogenic coolant supply. The present review article highlights the knowledge of new cryogenic cooling approaches in the turning process and its effect on process performance during the machining of various materials. Following the new cryogenic cooling approaches, a review on optimization and modeling of the cryogenic turning process was reported. From the review, it was observed that novel cryogenic cooling methods positively affect the turning performance characteristics like surface roughness, tool wear, chip morphology and surface integrity, respectively. It was observed that the cryogenic machining improves the product functional performance when compared to dry, conventional (flood cooling) and minimum quantity lubrication machining processes, respectively. Finally, future directions were discussed. © 2020 Taylor & Francis Group, LLC.