Asokan Thondiyath

An algorithm for cooperative task allocation in scalable, constrained multiple robot systems

The current trends in the robotics field have led to the development of large-scale multiple robot systems, and they are deployed for complex missions. The robots in the system can communicate and interact with each other for resource sharing and task processing. Many of such systems fail despite the availability of necessary resources. The major reason for this is their poor coordination mechanism. Task planning, which involves task decomposition and task allocation, is paramount in the design of coordination and cooperation strategies of multiple robot systems. Task allocation mechanism allocates the task in a mission to the robots by maximizing the overall expected performance, and thereby reducing the total allocation cost for the team. In this paper, we formulate a heuristic search-based task allocation algorithm for the task processing in heterogeneous multiple robot system, by maximizing the efficiency in terms of both communication and processing cost. We assume a set of decomposed tasks of a mission, which needs to be allocated to the robots. The near-optimal allocation schemes are found using the proposed peer structure algorithm for the given problem, where the number of the tasks is more than the robots present in the system. The cost function is the summation of static overhead cost of robots, assignment cost, and the communication cost between the dependent tasks, if they are assigned to different robots. Experiments are performed to verify the effectiveness of the algorithm by comparing it with the existing methods in terms of computational time and quality of solution. The experimental results show that the proposed algorithm performs the best under different problem scales. This proves that the algorithm can be scaled for larger system and it can work for dynamic multiple robot system.

Combining Lean and Six Sigma in the context of Systems Engineering design

Purpose – The purpose of this paper is to present a combined framework for system design using Six Sigma and Lean concepts. Systems Engineering has evolved independently and there are numerous tools and techniques available to address issues that may arise in the design of systems. In the context of systems design, the application of Six Sigma and Lean concepts results in a flexible and adaptable framework. A combined framework is presented here that allows better visualization of the system-level components and their interactions at parametric level, and it also illuminates gaps that make way for continuous improvement. The Deming’s Plan-Do-Check-Act is the basis of this framework. Three case studies are presented to evaluate the application of this framework in the context of Systems Engineering design. The paper concludes with a summary of advantages of using a combined framework, its limitations and scope for future work. Design/methodology/approach – Six Sigma, Lean and Systems Engineering approaches...

Dominant component in muscle fatigue induced hand tremor during laparoscopic surgical manipulation

Accuracy of laparoscopic surgery gets affected by the hand tremor of the surgeons. Though cognitive load is inevitable in such activity which promotes tremor, muscle fatigue induced tremor is significant among the most important sources of tremor. Characteristic of fatigue induced hand tremor and its dominant directional properties are reported in this work. For a fixed laparoscopic tool grip with temporally synchronized predefined task protocols, characteristics of fatigue induced tremors have been studied. Dominant component of tremor was found to be in the sagittal plane in case of both static and dynamic tasks. In order to relate it with the muscle fatigue level, spectral properties of surface electromyography (SEMG) were also investigated simultaneously. A study of transient effect on tool positioning was also included, which conjointly advocates the other experimental results on fatigue induced hand tremor as well.

Empirical Mode Decomposition-based filtering for fatigue induced hand tremor in laparoscopic manipulation

Fatigue induced hand tremor (FIT) is an unavoidable phenomenon, which substantially limits the accuracy of the surgical manipulation for long duration laparoscopic surgeries. Filtering intended motion from tremor is a challenging task as the properties of tremor change with increasing muscle fatigue levels. Muscle fatigue induced hand tremor has highly nonlinear and nonstationary characteristics that need a filtering strategy different from the conventional filters. Empirical Mode Decomposition (EMD) based filters have become popular in the recent past for its enhanced nonlinear signal handling capability. EMD based filtering strategy is case specific in nature as the EMD does not have any general analytical formulation unlike other (Kernel based) popular filtering techniques. In this work, we have addressed the tremor filtering issue with the help of EMD and the probability distribution characteristics analysis of Intrinsic Mode Functions (IMF) of the tremulous laparoscopic tool trajectory. A modified distribution asymmetry measure was employed to find out the threshold IMF for reconstruction of tremor free motion at different fatigue levels. In order to find the robustness of the proposed technique, the compensation strategy has been tested extensively on synthetic signal and experimentally acquired signals. Filtering threshold at different fatigue levels was also demonstrated for various subjects. Despite the time-varying properties of tremor, the proposed filtering strategy substantiates its efficacy to diminish the effect of tremor which was not possible by the conventional fixed cut-off filtering techniques.

Design and analysis of a novel quadrotor system - VOOPS

This paper presents the design and analysis of a quadrotor with a novel configuration, VOOPS-Vertically Offset Overlapped Propulsion System. The objective of this configuration is to increase the payload capacity of a quadrotor without increasing the overall dimension and without compromising endurance. This has been achieved by vertically offsetting the propellers and allowing propeller overlaps so that an increase in propeller size can be achieved without any increase in the overall dimensions. The design details and the dynamic model of the VOOPS configuration are presented. The constraints on the design parameters such as propeller offset and overlap are determined using propeller deflection model and geometry respectively. The effects on change in the design parameters of VOOPS configuration were studied using bench tests and performance simulation of quadrotor with VOOPS configuration were carried out. Practical implementation of VOOPS configuration is also discussed.

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

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 platform- and 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.

Design and analysis of an underwater quadrotor - AQUAD

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.

Development of virtual reality based robotic surgical trainer for patient-specific deformable anatomy

The need for training surgeons for robotic surgeries is increasing with the increase in number of laparoscopic procedures performed with robots. The commercial simulators available are expensive and hence not available to all. This paper provides a method to develop a virtual reality based simulator with open source software and a game engine. Another feature included in the simulator is the use of patient-specific organ models. This is advantageous since it is safe and less expensive compared to other simulators, and also is more flexible due to the use of game engine. For a realistic simulation, a model of tool-tissue interaction is carried out between the tool and an external tumour using the method described. The reconstructed geometric organ model, after being meshed, is integrated into the laparoscopic surgical simulation system consisting of a haptic interface device and a graphic display.

Hardware-in-the-Loop verification for 3D obstacle avoidance algorithm of an underactuated flat-fish type AUV

Hardware-in-the-Loop (HIL) simulations play a major role in the field of testing of Autonomous Underwater Vehicle (AUV) well before the actual vehicle is developed and deployed in the water. This paper discusses the real-time verification of a 3D obstacle avoidance algorithm of an underactuated flat-fish type AUV using hardware-in-the-loop simulation tool. Software-In-the-Loop (SIL) models are developed in MATLAB/Simulink environment and the HIL simulation is performed using dSPACE environment. The development of HIL test bench and the simulation results are presented in this paper. The results show that the HIL simulation is an effective tool for the verification of control algorithms and the developed obstacle avoidance algorithm can be used in real-time for the flat-fish type AUV.

Obstacle Avoidance Using Multi-Point Potential Field Approach for an Underactuated Flat-Fish Type AUV in Dynamic Environment

This paper presents a multi-point potential field (MPPF) method for obstacle avoidance of Autonomous Underwater Vehicles (AUV) in a 2D dynamic environment. In this method, an arc of predefined radius on a semicircle in the positive x-axis around the bow of an AUV is discretized into equiangular points with centre as the current position. By determining the point at which the minimum potential exists, the vehicle can be moved towards that point in 2D space. Here the analytical gradient of the total potential function is not calculated as it is not essentially required for moving the vehicle to the next position. The proposed obstacle avoidance algorithm is interfaced with the dynamic model of an underactuated flat-fish type AUV. The obstacle avoidance algorithm generates the path elements to the trajectory planner and the vehicle tracks the trajectory. The details of the algorithm and simulation results are presented.