Asokan Thondiyath

Bio: Asokan Thondiyath is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Robot & Control theory. The author has an hindex of 9, co-authored 70 publications receiving 226 citations. Previous affiliations of Asokan Thondiyath include Intuitive Surgical.

Optimisation of an Active Remote Centre of Motion Mechanism for Minimal Extracorporeal Workspace for Robotic Surgery

Abstract: Conventional laparoscopic surgical tools penetrate a patient body through a fixed point called trocar point. Surgeons maintain this pivoting point on the patient body with their coordinated hand movements. Mechanism used for achieving this kinematic constraint is known as Remote Centre of Motion (RCM) mechanism and is widely used in surgical robots. Active RCM mechanism will enable positioning the constraint point virtually anywhere within the reach of the linkage. In this work, we present an optimisation strategy for an active RCM to minimise the extracorporeal workspace. The link lengths of the active RCM mechanism have been optimised and the dexterity of the tool has been analysed for various trocar positions. Kinematic analysis of the RCM mechanism, optimisation strategy, and the results of the dexterity analysis are presented.

Differential analysis of muscle fatigue induced elbow and wrist tremor in controlled laparoscopic manoeuvring.

Abstract: Background Fatigue induced hand tremor (FIT) is a primary limiting concern for the prolonged surgical intervention in minimally invasive surgery (MIS) and robot-assisted-minimally invasive surgery (RAMIS). A thorough analysis is necessary to understand the FIT characteristics in laparoscopic tool movement. The primary aim of this study is to perform a differential analysis of the elbow and wrist tremor due to muscle fatigue in laparoscopic manoeuvring. Methods We have introduced a joint angle based tremor analysis method, which enables us to perform a differential study of FIT characteristics at the individual joint. Experimental data was acquired from a group of subjects during static and dynamic laparoscopic movement in an imitative RAMIS master manipulation scenario. A repetitive task was performed with a total span of 1 h for observing the effect of muscle fatigue. Along with the joint angle variation, surface electromyography (sEMG) signal was also studied in the analysis. Results The wrist tremor is more predominant than tremor generated at the elbow, especially in highly fatigued condition. The high-frequency tremor (>4 Hz) is contributed by the wrist joint. Moreover, the variation of the wrist and elbow tremor ratio was found to be dependent upon the experience of the surgeons. Conclusions In this work, we have investigated the attribution of elbow and wrist joints in FIT during laparoscopic tool manipulation. The outcomes may be useful for the design of robot-assisted surgical manipulator, and can be used for quality assessment of surgical training as well.

Computational Fluid Dynamic Study on the Effect of Winglet Addition in Flapping Hydrofoils to Evaluate the Propulsive Performance of Wave Gliders

Abstract: Wave Gliders have specific arrangements that convert up/down wave motion into forward propulsion. These arrangements consist of an array of hydrofoils that are pivoted to pitch within a certain range of motion. Several attempts have been made by researchers to improve the propulsion efficiency of wave gliders, some of which include: modifying hydrofoil profile, inducing asymmetry in hydrofoil pitching (flapping), varying the spacing between hydrofoils, etc. In this research work, we study the effect of adding winglets to the hydrofoils. The winglets are meant to reduce tip vortices that typically occur at hydrofoils and hence improve propulsion efficiency. Computational fluid dynamic studies have been carried out to assess the effect of adding winglets to the hydrofoil. Results show that addition of a winglet to a flapping hydrofoil improves the thrust coefficient.

A new gripper that acts as an active and passive joint to facilitate prehensile grasping and locomotion

Abstract: Among primates, the prehensile nature of the hand is vital for greater adaptability and a secure grip over the substrate/branches, particularly for arm-swinging motion or brachiation. Though various brachiation mechanisms that are mechanically equivalent to underactuated pendulum models are reported in the literature, not much attention has been given to the hand design that facilitates both locomotion and within-hand manipulation. In this paper, we propose a new robotic gripper design, equipped with shape conformable active gripping surfaces that can act as an active or passive joint and adapt to substrates with different shapes and sizes. A floating base serial chain, named GraspMaM, equipped with two such grippers, increases the versatility by performing a range of locomotion and manipulation modes without using dedicated systems. The unique gripper design allows the robot to estimate the passive joint state while arm-swinging and exhibits a dual relationship between manipulation and locomotion. We report the design details of the multimodal gripper and how it can be adapted for the brachiation motion assuming it as an articulated suspended pendulum model. Further, the system parameters of the physical prototype are estimated, and experimental results for the brachiation mode are discussed to validate and show the effectiveness of the proposed design.

Characterization of the Propulsion System for Submersible Multimedium Robotic Vehicles

Abstract: Multimedium robots are a new class of bioinspired vehicles with the ability of cross-domain transition and maneuverability across multiple domains. Such hybrid robots can transverse both in air and water, overcoming the stark differences in the motion dynamics within these mediums. Differences in the density, viscosity, and additional fluid-induced forces of the medium make the propulsion system design for multimedium robots a crucial challenge. Both unmanned aerial and remotely operated underwater vehicles rely on electrical propulsion coupled with propellers to navigate in their own respective medium of operation. However, due to the density differences in water and air, which is approximately 103 times, an aerial propeller demands higher RPM to generate significant thrust, unlike an underwater propeller. Higher water density and fluid inertia, on the other hand, demand a greater in-drive torque to spin the propeller in underwater conditions. Other critical parameters to be considered while choosing a suitable propulsion system are propeller diameter, propeller pitch, shaft torque requirements, operational RPM of motor–propeller pair, cavitation, and propeller tip deflection. This article presents an in-depth investigation and evaluation methodology to identify the feasible operating range for propellers and motors that meet the aerial and underwater thrust requirements while minimizing cavitation and propeller deflection. The thrusters (motor-propeller pair) are investigated individually, where propeller performance and physical constraints on the propeller blade are analyzed using blade elemental momentum theory (BEMT), while the motor is studied using the three-constant motor model. These subsystems are then mapped using torque equilibrium to determine their specific operational regime and overall efficiency. Numerical simulation in QPROP demonstrates that aerial thrusters can be utilized for both the mediums but with a sacrifice of overall efficiency. The optimal motor efficiency was 73.06% in aerial operation and 8.1% in underwater operation, but with increased thrust underwater due to higher fluid density, which is essentially a design tradeoff. The results of the analysis are experimentally validated and further presented as a framework for selecting an appropriate propulsion subsystem for multimedium vehicles based on the specific user-defined design requirements.

Out of the Crisis

Abstract: According to W. Edwards Deming, American companies require nothing less than a transformation of management style and of governmental relations with industry. In Out of the Crisis, originally published in 1982, Deming offers a theory of management based on his famous 14 Points for Management. Management's failure to plan for the future, he claims, brings about loss of market, which brings about loss of jobs. Management must be judged not only by the quarterly dividend, but by innovative plans to stay in business, protect investment, ensure future dividends, and provide more jobs through improved product and service. In simple, direct language, he explains the principles of management transformation and how to apply them.

Guidance And Control Of Ocean Vehicles

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Surgical Instrument with Shiftable Transmission

Abstract: A surgical tool having an elongated shaft having a proximal end and distal end. A surgical end effector is located about the distal end. The surgical end effector has a plurality of effector mechanisms comprising a plurality of degree of freedoms. An effector body is located at the proximal end. The effector body includes a plurality of motor interfaces for driving the plurality of effector mechanisms. A transmission is coupled to the effector body

The Foldable Drone: A Morphing Quadrotor That Can Squeeze and Fly

Abstract: The recent advances in state estimation, perception, and navigation algorithms have significantly contributed to the ubiquitous use of quadrotors for inspection, mapping, and aerial imaging. To further increase the versatility of quadrotors, recent works investigated the use of an adaptive morphology, which consists of modifying the shape of the vehicle during flight to suit a specific task or environment. However, these works either increase the complexity of the platform or decrease its controllability. In this letter, we propose a novel, simpler, yet effective morphing design for quadrotors consisting of a frame with four independently rotating arms that fold around the main frame. To guarantee stable flight at all times, we exploit an optimal control strategy that adapts on the fly to the drone morphology. We demonstrate the versatility of the proposed adaptive morphology in different tasks, such as negotiation of narrow gaps, close inspection of vertical surfaces, and object grasping and transportation. The experiments are performed on an actual, fully autonomous quadrotor relying solely on onboard visual-inertial sensors and compute. No external motion tracking systems and computers are used. This is the first work showing stable flight without requiring any symmetry of the morphology.

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.