Thiyagarajan Ranganathan

Bio: Thiyagarajan Ranganathan is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Underwater & Linear actuator. The author has an hindex of 4, co-authored 10 publications receiving 37 citations.

Design and analysis of an underwater quadrotor - AQUAD

Abstract: A new configuration of underwater robotic vehicle, named AQUAD, is presented here. It is a configuration with four thrusters in a plane which is inspired from an aerial quadrotor system. The system is designed considering the hydrodynamic challenges, and mathematically modelled using Newton-Euler approach. A PID controller is used to control the attitude of the system and implemented with the model to analyze its behavior. The system is commanded with various inputs and the performance of the model with the controller is studied. A prototype of AQUAD is being developed and the system is to be tested in real time.

Modelling and Dynamic Analysis of a Novel Hybrid Aerial – Underwater Robot - Acutus

Abstract: Hybrid multi domain vehicles are of great interest in due to their ability to traverse between different medium. The objective behind developing such hybrid vehicle/robot is to combine the capabilities of systems operating in various domains. Very few vehicles are presently being developed which can traverse underwater and can fly in air. Development of systems with capability to traverse both in air and water is highly challenging because of the contrasting properties of the traversing domains. In this paper, we propose one such vehicle which can be used as a remotely operated vehicle (ROV) underwater and can fly as a quadrotor. Design of such system is critical, as the dimensions and other related parameters like the mass and volume has to be optimal for both aerial and underwater traversal. Hence the system mathematically modelled to analyze the dynamics of the system and the same has been used to optimize the dimensions and the overall performance of the result. This paper presents the detailed design, mathematical model of the system and the preliminary simulation results using the developed model. An experimental prototype is being developed to analyze and validate the concept.

Theoretical and Experimental Investigations on the Design of a Hybrid Depth Controller for a Standalone Variable Buoyancy System— vBuoy

Abstract: Design of controllers for underwater vehicles is challenging due to their nonlinear dynamics, time-varying model parameters, and environmental disturbances, which are difficult to measure or estimate. Conventional linear controllers sometimes fail to handle these issues effectively and hence it is necessary to design special controllers that are robust under such circumstances. Variable buoyancy (VB) engines are used in many underwater vehicles and standalone buoyancy modules are being developed for multiple underwater applications. Design and analysis of a hybrid depth controller for a single degree of freedom, standalone VB module, vBuoy, is presented in this paper. The design and mathematical model of the vBuoy is presented along with its open-loop performance analysis. A hybrid controller, which captures the best characteristics of a proportional–integral–derivative controller, a linear quadratic regulator, and a sliding mode controller, is designed for the depth control of the module. Based on the desired transient and steady-state behavior of the system, a supervisory controller is used to switch between the conventional controllers. The comparison of simulation results between the proposed hybrid controller and the conventional controllers shows a significant improvement in the closed-loop performance. The performance is evaluated using the parameters such as rise time, percentage overshoot, settling time, and root mean square error. The same has been implemented in an experimental vBuoy prototype to verify the performance of the hybrid controller and also to validate the robustness of the controller. Based on the simulation and experimental results, it was observed that the hybrid controller improves the trajectory tracking performance by 28%–33%.

Design and Analysis of Cascaded Variable Buoyancy Systems for Selective Underwater Deployment

Abstract: Variable Buoyancy systems for selective deployment has been designed and the analysis of dynamics is discussed in this paper. Multiple interconnected VB modules have specific advantages in positioning the payloads like sensors and communication equipment at various depths to collect strategically important subsea data. The design of metallic bellow based Variable Buoyancy Systems (VBS) is presented along with the dynamic analysis of the module. The dimensions of the VB module are optimised to give best performance at the desired depth of operation. Effect of anchoring the module to a base station and cascading multiple modules for deploying at various depths have been studied in detail. Simulation results show that the cascaded VB modules can be successfully deployed for selective applications under various operating conditions.

Design and analysis of cable-connected metallic bellows as Variable Buoyancy Modules

Abstract: Design of a variable buoyancy system with metallic bellows for underwater applications is presented here. Metallic bellow with a Linear Actuator is proposed as the Variable Buoyancy module. The metallic bellow is approximated as a cylinder and modelled mathematically to study the behavior of the module underwater. The response of the system at different initial orientation and the velocity of the system at different positive buoyancy are studied. The dynamics of the module, when anchored to an underwater platformand the motion characteristics of the module with various buoyancy levels are studied. Two similar modules are then cascaded one above the other and their performance is analyzed with alternative sequence of actuation.

Guidance And Control Of Ocean Vehicles

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Fish-inspired robots: design, sensing, actuation, and autonomy--a review of research.

Abstract: Underwater robot designs inspired by the behavior, physiology, and anatomy of fishes can provide enhanced maneuverability, stealth, and energy efficiency. Over the last two decades, robotics researchers have developed and reported a large variety of fish-inspired robot designs. The purpose of this review is to report different types of fish-inspired robot designs based upon their intended locomotion patterns. We present a detailed comparison of various design features like sensing, actuation, autonomy, waterproofing, and morphological structure of fish-inspired robots reported in the past decade. We believe that by studying the existing robots, future designers will be able to create new designs by adopting features from the successful robots. The review also summarizes the open research issues that need to be taken up for the further advancement of the field and also for the deployment of fish-inspired robots in practice.

Influence of propeller configuration on propulsion system efficiency of multi-rotor Unmanned Aerial Vehicles

Abstract: Multi-rotor Unmanned Aerial Vehicles make use of multiple propellers, mounted on arms, to produce the required lift. This article investigates the influence on propulsion system efficiency in hover due to the configuration of these propellers. Influence of pusher or puller configuration of the propeller, number of blades, shape and dimensions of the arm, coaxial and overlapping propellers, is presented. A dedicated test bench that allows testing of various experimental setups is designed and built in order to realistically represent multi-rotor arms. Test results show that a two-bladed pusher configuration is most efficient and slenderness of the arm has more influence on efficiency than shape. A coaxial propulsion system approaches the efficiency of a single-prop system at high disk loadings. Finally, interference effects due to overlapping propellers are discussed.

Current Algorithms, Communication Methods and Designs for Underwater Swarm Robotics: A Review

Abstract: As technology advances, the places we have been able to explore have drastically increased. However, the advancements in the underwater realm have staggered behind both the exploration of surface and air domains. This is due in part to the challenges that arise when placing a robot in water. One current shift has seen the use of a swarm of robots that are cheaper and are of a lower quality, that work together to accomplish a common goal, as opposed to using a single expensive robot. Swarm robotics benefits from being more tolerant of catastrophic failure and can cover large areas in smaller time frames. However, unlike other advancements in technology, underwater swarm robotics have struggled to compete with its counterparts on the surface and in the air. This is mainly due to the problems with communication underwater, the hazardous environment, the cost and difficulties with construction of underwater robots. This article conducts a literature review into the current state of underwater swarm robotics; it covers the design of the underwater robots, the methods used by the individual robot to perceive their environment, how they can localize to said environment, the methods of communication available underwater, centralized and decentralized control, the basis of swarm algorithms, the behaviors that are exhibited when a swarm works collectively and how swarms have been applied underwater.