Prabhu Rajagopal

Bio: Prabhu Rajagopal is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Ultrasonic sensor & Guided wave testing. The author has an hindex of 18, co-authored 129 publications receiving 1035 citations. Previous affiliations of Prabhu Rajagopal include Imperial College London & Indian Institutes of Technology.

Bio-inspired Underwater Robot with Reconfigurable and Detachable Swimming Modules

Abstract: Maneuverability and propulsive efficiency are of much interest in autonomous underwater robots. In this paper, we present a novel underwater robot design with two reconfigurable and detachable swimming modules that would be capable of offering both maneuverability and propulsive efficiency. They are also capable of reconfiguring automatically to take two different orientations favoring reduced drag in the swimming direction. A key feature of this design is that the reconfigurability is achieved without additional actuators - helpful in the development of autonomous swarm robots with good maneuverability and efficiency.

Implementing an Adaptive Thrust Distribution Algorithm on the Robust Control System for Serial Split-Hull Underwater Vehicles

Abstract: This paper discusses designing and implementing an adaptive thrust distribution algorithm on the already robust control system for serial split-hull underwater vehicles to maximise operational efficiency. Split-hull underwater vehicles are gaining popularity in subsea operations due to their flexible hyper-redundant design and enhanced manoeuvrability. These features facilitate them to replace conventional solutions, including torpedo-shaped Autonomous Underwater Vehicles (AUVs) and Remotely Operated Vehicles (ROVs). The field of research is currently undergoing a considerable transition toward operations on subsea activities that are more economical and efficient. Thus, implementing a robust and energy-efficient control system is of utmost importance. The robust Super Twisting Algorithm (STA) based control system is used on the vehicle, and an adaptive thrust distribution algorithm is proposed and implemented to optimise the energy efficiency further. The work involves modelling the vehicle, fluid forces, torque effects, and thruster configuration matrix and implementing the adaptive weight distribution on the STA-based control system. With the help of simulations, the improvements in the control system are proved.

Ultrasonic transducers based on spray coated PZT film for in situ operation for temperatures up to 200 °C

Abstract: Ultrasonic testing is widely used for assessing the integrity of structures, and increasingly, there is much interest in the inspection of components operating at elevated temperatures. Degeneration of acoustic couplant and active element are among the challenges widely reported to develop ultrasonic piezoelectric transducers operating at higher temperatures. In our study, the development of an in situ ultrasonic transducer using spray deposited PZT slurry as the active element to perform bulk ultrasonic inspection/monitoring of components and structures operating at elevated temperatures (up to 200° C) is described. This method allows deposition of PZT coatings of thickness > 500 µm. The operation of the developed ultrasonic transducer performing pulse-echo ultrasonic measurements at 1 MHz up to 200 °C is demonstrated experimentally and compared with conventional methods. Merits and limitations to practical realisation are also discussed.

Wave visualization of ultrasonic guided waves in a metallic structure using fiber Bragg gratings

Abstract: We experimentally demonstrate the visualization of ultrasonic wave propagation in a metallic plate using a surface-bonded fiber Bragg grating sensor and non-contact excitation of the desired guided mode.

Effect of Conical Profile on the Transmission of Elastic Waves From Cylindrical Waveguide to Bulk

Abstract: This paper studies the transmission of elastic waves into test specimens for cylindrical waveguide-based ultrasonic transducers. However, to achieve better mode focusing, topographical waveguides with conical profiles were studied. Finite element simulations were used to study wave propagation and transmission into specimen samples using such “transmission horns.” Fundamental longitudinal mode L(0,1) was generated in cylindrical rods. Results from both finite element simulations and experiments show that a 50-deg conical transition profile help achieve better transmission and beam directionality into the specimen and also better reception of the back wall reflections at the waveguide as compared to a simple cylindrical rod waveguide.

Probability and Statistical Inference

Abstract: The Foundations of Statistics By Prof. Leonard J. Savage. (Wiley Publications in Statistics.) Pp. xv + 294. (New York; John Wiley and Sons, Inc.; London: Chapman and Hall, Ltd., 1954.) 48s. net.

X-ray computed tomography for additive manufacturing: a review

Abstract: In this review, the use of x-ray computed tomography (XCT) is examined, identifying the requirement for volumetric dimensional measurements in industrial verification of additively manufactured (AM) parts. The XCT technology and AM processes are summarised, and their historical use is documented. The use of XCT and AM as tools for medical reverse engineering is discussed, and the transition of XCT from a tool used solely for imaging to a vital metrological instrument is documented. The current states of the combined technologies are then examined in detail, separated into porosity measurements and general dimensional measurements. In the conclusions of this review, the limitation of resolution on improvement of porosity measurements and the lack of research regarding the measurement of surface texture are identified as the primary barriers to ongoing adoption of XCT in AM. The limitations of both AM and XCT regarding slow speeds and high costs, when compared to other manufacturing and measurement techniques, are also noted as general barriers to continued adoption of XCT and AM.