Faculty Publications
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Publications by NITK Faculty
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Item Computation of lightning induced voltages on telecommunication subscriber lines(Institute of Electrical and Electronics Engineers Inc., 2002) Kannu, P.D.; Thomas, M.J.The electric and magnetic fields produced by a lightning stroke in the vicinity of a telecommunication line can illuminate the line and it can acquire induced overvoltages which may be detrimental to the equipments connected to the telecommunication line. The magnitude and waveshape of the electromagnetic fields produced by lightning as well as the induced voltage on telecommunication line are influenced by the finite conductivity of the ground. In this paper, the induced transient voltages on an overhead telecommunication subscriber line due to a nearby lightning stroke to the ground are computed. From the results it is seen that the induced voltage is bipolar for all the observation points except at the line midpoint for the lightning striking point location chosen in this study. It is also observed that the finite ground conductivity decreases the magnitude of the induced voltage at the line terminations where as it increases the induced voltage as the line mid point is approached. The results obtained in this study will be useful in evolving a suitable lightning protection scheme for the rural telephone exchanges which are interconnected using overhead lines instead of underground cables as in the case of urban exchanges. At the same time these rural telephone exchanges have become more vulnerable to transient overvoltages as they are being converted into digital ones with their susceptibility levels for transient overvoltages being much lower than the old electromechanical exchanges. © 2001 Convenor.Item Computation of radiated electromagnetic fields from a lightning return stroke(Institute of Electrical and Electronics Engineers Inc., 2003) Kannu, P.D.; Thomas, M.J.This paper presents the computed electric fields produced by a lightning return stroke. It is observed that the rate of rise of lightning current does not influence the vertical component of electric field. The negative pre-pulse magnitude of the horizontal electric field increases with time derivative of the lightning current where as the initial negative peak of the horizontal electric field increases in direct proportion to the return stroke velocity. © 2003 Society of EMC Engineers.Item A Comparative Analysis between Sliding Mode Control and Super Twisting Sliding Mode Control Applied on a Quadcopter(Institute of Electrical and Electronics Engineers Inc., 2024) Vijapur, S.; Jungade, O.A.; Thomas, M.J.The use of quadcopters has grown exponentially in countless fields. With the ever-growing demand for automation in today's world, algorithms for the autonomous control of drones have become a major area of research. In this paper, we implement two control strategies, namely Sliding Mode Control (SMC) and Super Twisting Sliding Mode Control (STSMC), on a 6 Degree of Freedom quadcopter model and compare their performance. Using Fast Fourier Transforms, the two controllers are analysed to enable an effective comparison of the chattering in the control input by defining a suitable index. With this index, we observe a decrease of two orders of magnitude in the chattering present in the input given by the STSMC controller. © 2024 IEEE.Item Simulink-Based Comparative Study and Selection of a Controller for a Waist-Assistive Exoskeleton(Springer Science and Business Media Deutschland GmbH, 2024) Thomas, M.J.; Mohanta, J.; Sahoo, S.; Santhakumar, S.This paper describes the conceptual design and comparative simulation study of three controller strategies—Proportional Integral Derivative (PID), PD-based Computed Torque Control and PD-based Sliding Mode Control (SMC) for a waist-assistive exoskeleton. The exoskeleton is modelled in Simulink, and its joint control is simulated for a predefined desired trajectory. The motor, joint and link parameters are incorporated into the Simulink model to match the properties and evaluate the performance similar to the real-time system. In addition, MSC ADAMS-based simulation study is also performed to validate the dynamic model of the exoskeleton. The preliminary study indicates that the SMC controller shows better tracking accuracy than the other two strategies. The proposed exoskeleton is designed to reduce the effort taken by the user during regular sit-to-stand and weight-lifting operations. It is intended to lower the strain the lumbar muscles take during standing and lifting operations over the long run. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.Item Development of Pneumatic Soft Gripper for Effective Material Handling(Institute of Electrical and Electronics Engineers Inc., 2024) Naveen, S.; Panigrahi, S.; Vinit, A.; Sudar, I.H.; Thomas, M.J.Recent times have shown a drastic transition in robotics from rigid to soft mechanisms. The reason is that soft robots offer safer human-robot interactions, reduce weight and also offer strong environmental adaptability. However, the inherent characteristics of soft materials to exhibit multiple degrees of freedom (DoF) make it challenging to control their movements. Therefore, this paper presents the development of a soft gripper with simple architecture to effectively and economically manipulate delicate objects. The gripper constructed using silicon rubber has an air cavity to actuate its opening and closing pneumatically. This paper presents the different stages of its construction and demonstrates its application on a 4 DoF robotic arm for handling delicate objects. A simulation study of the structural parameters of the proposed soft gripper is also carried out using ANSYS finite element software. The preliminary results show the superior adaptability of the soft gripper in handling objects of various shapes and sizes. The proposed system can find application in food, biomedical and electronic industries. © 2024 IEEE.Item Development of an Intuitive Autonomous Ground Robot for Indoor Delivery Applications(Springer Science and Business Media Deutschland GmbH, 2025) Peter, J.; Thomas, M.J.; Gokulkrishna, S.; Cholappally, K.; Santhakumar, S.Efficient and reliable parcel delivery services are always desired in different sectors such as hospitals, offices, industries and households. One promising solution to meet, this need is the application of Autonomous Mobile Robots (AMRs) capable of navigating complex indoor environments to deliver packages and goods. Generally, AMRs are used for the last-mile delivery of parcels. The end users of such robots have different skill sets, and the robot must have a simple user interface to ensure easy usability. This paper presents an AMR with an intuitive Graphic User Interface (GUI) and aesthetic design. It is enough for the end user to define the goal locations on the resulting map shown on the robot screen. The AMR will autonomously navigate to the given goal location. Besides, the effectiveness of sensor fusion and a comparative study of various combinations of sensor fusion are also described in this paper. In addition, the application of LiDAR odometry and its performance is also analyzed in this paper. The primary objective of this study is to identify an approach that improves the AMR’s tracking accuracy and makes it suitable for dynamic work environments. This paper describes the development of an AMR for last-mile delivery purposes, and its proof of concept is evaluated on the fabricated prototype. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.Item Academic Insights and Future Prospects of Soft Robotics: Architecture, Material, Control and Application(Springer, 2024) Thomas, M.J.; Santhakumar, S.Soft Robotics is an emerging field with the potential to address real-world problems with newer possibilities and safer human–robot interactions. Generally, soft robots comprise materials with moduli ranging from 104 to 109 Pa. The significant characteristics of soft robots include their high flexibility, compatibility, and superior environmental adaptability. Despite the several advantages of soft robots, many physical limitations exist due to their structural compliance and the viscoelastic behaviour of the material which leads to non-linear deformations in the material. This very reason necessitates sophisticated and novel sensing, actuation and non-linear control methods for soft robots. This review paper provides a comprehensive understanding of the advancements in soft robots and finally outlines the gaps in this field, currently limiting their usage in several applications. The pros and cons of the various technologies are discussed, and possible strategies for the superior performance of soft robots and their prospects are outlined in this paper. © Indian Institute of Science 2025.Item Soft autonomous mobile manipulators in agricultural automation – a review(Emerald Publishing, 2025) Khan, T.; Thomas, M.J.Purpose – This review paper aims to illustrate the potential of soft autonomous mobile manipulators (SAMM) in agriculture tasks involving harvesting and crop monitoring. Design/methodology/approach – This paper systematically analyzes the major components involved: soft grippers, actuation and control methods, localization and path planning of mobile robots and integrated motion planning of mobile manipulators in agricultural environments. Findings – While mobile robots and soft manipulators show promising individual developments, their integration faces significant challenges. Critical issues include real-time control implementation, environmental adaptability and coordinated task execution between mobility and manipulation systems. Originality/value – This study addresses a significant gap in the literature, as there is currently no comprehensive review examining soft mobile manipulation systems and their integration into agricultural applications. By providing an in-depth analysis of core components, planning strategies and applications that combine delicate manipulation with efficient navigation, this work is a reference for researchers and practitioners developing state-of-the-art agricultural robotics. © 2025 Emerald Publishing LimitedItem Development, optimization, and prototyping of a simplified sit-stand mechanism for lower limb impairments(Springer Science and Business Media Deutschland GmbH, 2025) George, S.P.; Thomas, M.J.; Mathew, M.; Gangadharan, N.; Varghese, A.K.A sit-stand device for rehabilitation should be simple in its design, easy to manufacture, and convenient for individuals with mobility impairments to use. This paper proposes a design framework and prototyping process for developing an assisted sit-to-stand mechanism tailored to the specific limitations faced by individuals with lower limb impairments. The study incorporates a functional kinematic and kinetic design to ensure the mechanism’s usability across a diverse range of individuals. Recognizing the critical challenges faced by individuals with spinal cord injuries (SCI) and subsequent paralysis, the design philosophy integrates considerations specifically aimed at this population. A simplified circular design trajectory is presented for individuals with muscle paralysis, focusing on the synthesis of an electrically actuated mechanism. A four-bar linkage is modeled to represent the mechanism in the sagittal plane. The functional attributes of the device are determined, and kinematic synthesis is performed to ensure comfort during the sit-to-stand motion. This is achieved by minimizing the actuator’s travel distance during the lift. The velocity and acceleration profiles of the linear actuator are determined after applying boundary conditions. An optimal configuration is selected based on minimizing the displacement of the electric actuator. A human body model based on a 50th percentile male was developed to simulate a motion study of the sit-stand and validate the trajectory using the motion study module in SOLIDWORKS™. An optimum sit-to-stand linkage design was synthesized, and the corresponding prototype was fabricated. The independent anthropometric dimensions on which the design depends are the thigh length and the weight. The sagittal linkages for lifting were calculated and tested through simulation with a human body model to replicate the sit-to-stand movement. The prototype was evaluated on an able-bodied individual. A key design feature was the repositioning of support from the armpit to the hip, thereby reducing user discomfort and improving ergonomics. The motion study revealed that the trajectory of the hip joint (H-point) followed a nearly circular curvature. Stability analysis using a mannequin confirmed a static stability margin of 1 and showed that the device would tip forward only if the deceleration exceeded 35.8 m/s2, which is significantly higher than typical human-induced accelerations—indicating safe operation during use. The prototype fabricated demonstrated the intended sit-to-stand functionality and validated the design approach. The motion analysis confirmed ergonomic hip support and smooth joint trajectories. While the initial testing was successful on an able-bodied subject, further evaluation involving individuals with spinal cord injuries is recommended for final adjustments. This work presents a cost-effective and customizable framework for manufacturing sit-to-stand assistive devices, scalable for variations in body weight and thigh length. © International Federation for Medical and Biological Engineering 2025.