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

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Recent Advances in Computational and Experimental Mechanics, Vol II

Analysis of a Double Edge Cracked Circular Ring Under Diametrical Compression

Deep neural network (DNN)-based methods are suitable for the rapid inversion of borehole resistivity measurements. They approximate the forward and the inverse problem offline during the training phase, and they only require a fraction of a second for the online evaluation (aka prediction). Herein, we have adopted a DNN-based iterative algorithm to design a borehole instrument such that the inverse solution is unique for a given earth parameterization. We select a large set of electromagnetic measurement systems routinely used in logging operations, and our DNN algorithm selects a subset of measurements that are suitable for inversion purposes. Numerical results with synthetic data confirm that this approach can provide valuable insight when designing borehole-logging instruments. © 2022 Society of Exploration Geophysicists.

Geophysics

A deep learning approach to design a borehole instrument for geosteering

Six-degree-of-freedom (6-DOF) hovering control is important for underwater robots to perform various tasks. Our previous underwater robot study, which used tilting thrusters, could not control 6-DOF motion simultaneously owing to several mechanical and control problems. In this study, we developed a new robot with tilting thrusters and improved 6-DOF hovering performance. The maneuverability of the robot was evaluated by analyzing the force and moment of the thrust vector. Based on this, a redundant tilting mechanism without constraints was designed to solve structural problems. A proportional–integral–derivative (PID)-based control design using the decomposition and compensation method (PID-DC) that is appropriate for this mechanism, was derived. The decomposition method was used to overcome the nonlinearity of the thrust vector caused by the tilting mechanism, and the null-space projection technique was applied to minimize the thrust force and avoid the boundary of the tilting angle. A compensator based on the empirical model of the tilting thruster transferred the control input to the system with regulation. Simulation and experimental results verified the validity of the controller for the 6-DOF hovering motion of the robot, and the hovering performance was significantly improved. Furthermore, the stability of the hovering performance under tidal currents was demonstrated through disturbance experiments. © 2021 Elsevier B.V.

Robotics and Autonomous Systems

Hovering control of an underwater robot with tilting thrusters using the decomposition and compensation method based on a redundant actuation model

We revisit the Partially-Saturated-Cells method (PSC) in the context of incompressible single-phase flows past stationary and moving bodies. This methodology adds a solid collision operator to the Lattice Boltzmann Equation, resulting in a unified evolution equation everywhere in the domain that suitably accounts for the boundary conditions. The unified evolution equation, which also allows for a smooth transition from solid cells to fluid cells, is dictated by the solid volume fraction, obtained using a simple geometric approach. We prove that the PSC approach exhibits nominal second-order accuracy in presence of straight and curved boundaries for pressure, although spatial order of accuracy in velocity degrades to first-order. Our analysis also reveals that PSC is approximately discretely conservative in the incompressible limit with the mass conservation errors being dependent on the lattice size and relaxation time. For simulations involving moving body problems, the method is found to introduce acceptable level of spurious force oscillations, which rapidly decrease with increasing grid resolution. To the best of the authors' knowledge, the present investigations pertaining to discrete conservation and spurious force oscillations in the PSC approach have never been discussed in literature. Extensive numerical experiments are performed involving both stationary and moving bodies, with imposed and induced motion, to assess the applicability of the PSC approach. Our findings illustrate that the inclusion of added mass effects are important for accurate force and torque computations in case of accelerating solids. Numerical investigations, that include unsteady flows featuring three degrees-of-freedom fluid-particle interactions clearly highlight the ability of the PSC approach in resolving complex hydrodynamical phenomena. This in-depth evaluation of the PSC approach conclusively demonstrates its efficacy as a promising computational framework for efficient and robust computations of incompressible fluid flows over a range of flow scenarios. © 2022 Elsevier Ltd

Computers \& Mathematics with Applications

Re-examining the partially saturated-cells method for incompressible flows with stationary and moving bodies

Abstract: Deformation until the beginning of disintegration (i.e., the first rupture time) is the first stage of a droplet’s secondary breakup in a gas stream. Experiments were performed to examine the effects of density, viscosity and surface tension of the liquid on the droplet deformation characteristics. The characteristics include droplet relative velocity, displacement and deformation. The test liquids included molten metals along with water-like liquids, offering wide ranges of density (788–6900 kg/m3), viscosity (0.86–3.63 mPa s) and surface tension (0.022–0.71 N/m). Results are presented in terms of non-dimensional numbers corresponding to each liquid property: density ratio, viscosity ratio and surface tension ratio. It was observed that the density and surface tension ratios affected the deformation aspects, but the effect of the viscosity ratio was not significant. For the liquids excluding the metals, the relative velocity of the droplet’s leeward side was significantly smaller compared to that of the windward side, at the first rupture time. The relative velocity of the droplet was observed to be higher for the liquid with higher density ratio. At low Weber numbers (We< ∼ 20), lower deformation was observed for the metals compared to other liquids. For We< ∼ 40 , higher first rupture times of low-surface-tension-ratio liquids contribute significantly to their higher displacements. Thus, it is concluded that, in addition to the Weber number, the density and surface tension ratios may need to be separately considered to characterize the droplet’s deformation phase. Graphic Abstract: [Figure not available: see fulltext.] © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.

Experiments in Fluids

Droplet deformation during secondary breakup: role of liquid properties

Wire electrical discharge machining (wire-EDM) process is having immense potential over conventional machining methods due to its non-contact nature of material removal. However, frequent and unanticipated machining failures like wire breakages negatively affect the productivity, sustainability and efficiency of the process. In this context, there is a wide scope to improve the process efficiency through online condition monitoring. A prominent aspect of EDM condition monitoring is discharge pulse discrimination. The threshold based methods which are currently being used has low accuracy and is reliant on operator's experience. In this study, a machine learning (ML) based pulse classification based on the extracted discharge characteristics is proposed. The features are extracted from the raw voltage and current senor signals collected from the machining zone during the wire EDM operation. Among the various ML models, Artificial Neural Network (ANN) classifier is found to have the maximum prediction accuracy of 98 %. Also, the effects of different discharge pulses on the productivity, surface finish and machining failures are investigated. The short circuit and arc discharges are found to cause wire breakage failure if they predominate the pulse cycle by more than 80 %. Also, short and arc sparks increase the surface roughness significantly, by up to 70 %. © 2022 IEEE.

nanoMan 2022 and AETS 2022 - 2022 8th International Conference on Nanomanufacturing and 4th AET Symposium on ACSM and Digital Manufacturing

Machine Learning Based Classification and Analysis of Wire-EDM Discharge Pulses

Journal of Micromanufacturing

Guest Editorial

Physics of Fluids

Comment on "roles of bulk viscosity on transonic shock-wave/boundary layer interaction" [Phys. Fluids 31, 096101 (2019)]

Limb disability is one of the serious problems and rehabilitation of lower limb requires an assistive force to the patient. A new design for stationary trainer for performing rehabilitation therapies for lower limb at the knee as well as hip joints in the sitting/lying positions is presented in this article. A passive orthosis (similar to an exoskeleton) is suggested in this system to provide a support to lower limb of the patient. The suggested mechanism also comprises of an active Cartesian manipulator based upon a spatial three parallel prismatic–revolute–revolute–revolute kinematic arrangement to perform the required limb therapeutic motions in the transverse/horizontal/lateral and sagittal/longitudinal plane. Numerically, the usefulness of the designed stationary trainer is confirmed using computer-based simulations along with a motion control scheme by performing various clinically suggested therapeutic motion tracking (passive range of motions) tasks. The article demonstrates the accomplishment of the control scheme for various training procedures of the lower limb. © The Author(s) 2022.

International Journal of Advanced Robotic Systems

Design and motion control scheme of a new stationary trainer to perform lower limb rehabilitation therapies on hip and knee joints

The goal of this work is to develop the next generation of coordinated optimal planning and control schemes for real-world robotic applications, with cost-effective intelligent robots that can safely and robustly perform the tasks at hand. This article presents a dual-loop optimal hierarchical control scheme for robotic manipulators consisting of outer and inner loops. The outer kinematic control loop in the operational space provides a joint velocity reference signal to the inner one. The kinematic control is formulated as a closed-loop optimal control approach to trajectory generation where the desired target (possibly time-varying) is obtained by acting upon the feedback from the actual state of the robot. The kinematic control is obtained using a closed-form analytic solution of the Hamilton-Jacobi-Bellman (HJB) equation. The proposed methodology defines the task in terms of the integral cost function, which results in a global optimal solution. The inner dynamic control loop consists of a neural network (NN)-based adaptive critic (AC) optimal tracking control scheme. The online NN approximator-based dynamic controller learns the infinite-horizon cost function related to inner loop error dynamics in continuous time and calculates the corresponding optimal control input to minimize the cost function forward in time. The stability and the performance of the proposed control scheme are shown theoretically via the Lyapunov approach and also verified experimentally using a 7-DOF Barrett WAM robot manipulator. The warehousing applications of the proposed dual-loop control scheme have been demonstrated experimentally in an exact warehouse setting. Note to Practitioners - This article was motivated by our previous experiences in the Amazon Robotics Challenge (ARC) competitions as a participant. Although the major lessons from those events revealed many important issues toward warehouse automation both from robotic vision and grasping aspects, the application aspects of control engineering to solution for these real-world problems could significantly benefit the today's highly automated society. The intention of this article is to address this situation by designing a cost-effective robot manipulator control scheme by optimizing robot manipulation trajectories in the outer loop along with the actuator input in the inner loop. Therefore, we propose a dual-loop optimal control scheme for robotic manipulations under a cost-optimal framework with guaranteed stability proof via the Lyapunov approach. This results in smoother trajectories with cost-effective control actuator inputs than the state-of-the-art methods. We believe that this work can be beneficial for academic and industrial research to design more advanced and optimized solutions in this domain. © 2004-2012 IEEE.