Sudeept Mohan

Energy aware real time scheduling algorithm for mixed task set

Energy consumption is one of the major limiting factors of battery operated real-time systems. Optimizing energy consumption without affecting performance and schedulability is the major topic to be researched. In this paper, an energy aware real time scheduling algorithm is proposed for a system with mixed task set consisting of both periodic and aperiodic tasks. Dynamic energy reduction techniques like Dynamic Voltage and Frequency Scaling (DVFS) is used for energy optimization without affecting the responsiveness of aperiodic tasks. Performance of the proposed algorithm is compared with non-DVS algorithm. Experimental evaluation reveals that the proposed algorithm saves 54.44% of energy in comparison with non-DVS algorithms. It achieves this with no degradation in responsiveness of the aperiodic tasks.

Cluster, Allocate, Cover: An Efficient Approach for Multi-robot Coverage

This article presents an algorithm for online multirobot coverage that proceeds with minimal knowledge of the already explored region and the frontier cells. It creates clusters of frontier cells which are designated to robots using an optimal assignment scheme. Coverage is then performed using a novel path planning technique. Many approaches that use clustering for multi-robot coverage do not specify strict time criteria for re-clustering. Moreover, the motion plans they use result in redundant coverage. To overcome these limitations, an appropriate motion plan for the robots is chosen based on the context of already covered frontiers. Dispersion of robots is vital for efficient coverage and is an emergent behavior in our approach. The efficacy of the proposed approach is tested in simulation and on a multi-robot test-bed. The algorithm performs better than some state of the art approaches.

A distributed algorithm for circle formation by multiple mobile robots

This paper suggests a distributed, decentralized approach for positioning multiple mobile robots in a circular formation in a semi synchronous setting. The problem of the circle formation with multiple robots which are arbitrarily placed on a 2D plane requires all robots to be uniformly positioned (i.e., at an equal angular distance of 2ŏ/N, where N = number of robots) on the circle circumference. The suggested approach uses explicit inter robot communication by way of message passing and forms a token ring based network. It uses the distributed solution of one of the classical synchronization problem often used in distributed systems, the Dining Philosopher Problem, for the robots to synchronize during their activation cycles.

Positioning Multiple Mobile Robots for Geometric Pattern Formation: An Empirical Analysis

This paper presents an experimental setup for absolute positioning of multiple mobile robots in an indoor environment using a low cost camera. Localization or positioning of mobile robot in its environment is crucial for deciding its future course of action. In this paper we have proposed to use an overhead camera for positioning multiple mobile robots which are required to act as a team. Also we have tested the efficacy of two existing distributed algorithms for circle formation using a team of five e-puck robots. The first algorithm is mathematically proven with many assumptions about the sensing and motion capabilities of mobile robots which are not feasible in the real world. In the second algorithm the authors have considered explicit inter robot communication and have utilized the distributed solution of a well known algorithm often discussed in distributed computing - the Dinning Philosophers Problem for the robots to synchronize during their activation cycle. The contribution of this paper is twofold i.e., first, a practical low cost, multi-robot positioning system is proposed and second, experimental evaluation of two distributed algorithms for circle formation by a team of mobile robots have been carried out. It is seen that the second algorithm outperforms the first.

Energy efficient real-time scheduling algorithm for mixed task set on multi-core processors

Energy optimisation is gaining greater significance in a wide range of systems from mobile devices to datacentres. Specifically, in battery powered real-time embedded systems where tasks are executed under hard timing constraints, energy optimisation poses a big challenge. This paper focuses on dynamic energy optimisation using a well-established technique namely dynamic voltage and frequency scaling (DVFS). This work presents a real-time scheduling algorithm that uses DVFS on mixed task system containing periodic as well as aperiodic tasks on homogeneous multi-core processor. The proposed algorithm guarantees periodic task deadlines and offers minimum aperiodic task response times. Simulation analysis shows that the proposed scheme saves more energy as compared to cycle conserving, static FVS and non-DVFS scheduling algorithms. Further, it does not result in any response time degradation of aperiodic tasks as compared to other algorithms.

Design and Development of a Real Time Scheduling Algorithm for Mixed Task Set on Multi-core Processors

This paper presents a real time scheduling algorithm for mixed task set on homogeneous multi-core platform. Periodic tasks are scheduled using Partitioned Earliest Deadline First (P-EDF) technique. Aperiodic tasks are assigned globally to different processor cores and scheduled using Total Bandwidth Server (TBS) on each core. In the proposed algorithm, the excess processing capacity of the cores left unused by the periodic tasks can be utilized by assigning aperiodic task to each core. This improves the overall utilization of individual core. Work conserving nature of global assignment reduces response time of aperiodic task. The proposed algorithm is implemented using java based simulator and tested on large number of synthetic test data. Results show improvement in utilization of individual processing core and improvement in response time of aperiodic tasks.

FAST: Synchronous Frontier Allocation for Scalable Online Multi-Robot Terrain Coverage

We propose Frontier Allocation Synchronized by Token passing (FAST), a distributed algorithm for online terrain coverage using multiple mobile robots, ensuring mutually exclusive selection of frontier cells. Many existing approaches cover the terrain in an irregular fashion, without considering the usability of the already covered region. For instance, in the task of floor cleaning in an office building, these approaches do not guarantee the cleanliness of large unbroken areas until a majority of the task is complete. FAST on the other hand, incrementally traverses the terrain generating structured trajectories for each robot. Following a structured trajectory for coverage path planning is proven to be a very powerful approach in literature. This renders large portions of the terrain usable even before the completion of the coverage task. The novel map representation techniques used in FAST render it scalable to large terrains, without affecting the volume of communication among robots. Moreover, the distributed nature of FAST allows incorporation of fault-tolerance mechanisms. Empirical investigations on maps of varied complexities and sizes both in simulation and on an A. Gautam ( ) · B. Jha · G. Kumar · J. K. Murthy · SP A. Ram · S. Mohan INSPIRE (Integrated Swarm Planning and Intelligent Robotics Engineering) Lab Birla Institute of Technology and Science, Pilani, India e-mail: avinash@pilani.bits-pilani.ac.in experimental test-bed demonstrate that the proposed algorithm performs better than some of the benchmark approaches in terms of coverage completion time and less redundant coverage.

STATE: Distributed algorithm for uniform circle formation by multiple mobile robots

Multi-robot pattern formation has a wide range of applications, such as inspection of hazardous regions, parallel and simultaneous transportation of load, area exploration, etc. This problem has been investigated both from the scientific and engineering perspectives. There is a whole body of experimental work on robot formations, and at the same, there is no dearth of theoretical research addressing the same problem. Several assumptions considered in these theoretical studies are overly simplified with an understanding that they will somehow be reasonably approximated. Although these theoretical research works are sound and complete, they do not show how an actual implementation compares with the idealized scenario. A new practical model is suggested in this paper for geometric pattern formation. This model uses approximate solutions to some of the assumptions considered in theoretical research works. A novel algorithm, STATE, is proposed and is shown to perform better than Défago and Konagaya’s algorithm for uniform circle formation. Both the algorithms are implemented on a real multi-robot test bed. A new framework for inter-robot communication is developed. It supports seamless asynchronous and non-blocking robot-to-computer, and robot-to-robot communication.

A token passing approach for circle formation by multiple mobile robots

This paper proposes a weakly centralized distributed approach for positioning multiple mobile robots in a circular formation based on token passing. The problem of the circle formation with multiple robots which are arbitrarily placed on a 2D plane requires all robots to be uniformly positioned (i.e., at an equal angular distance of 2π/N, where N = number of robots) on the circle circumference. The suggested approach is a leader-follower approach wherein it is the leader robot which computes the uniform positions on the circle circumference for all the follower robots. The problem of circle formation is divided into two sub-problems (a) leader selection and (b) finding enviable positions for the follower robots from the set of uniform positions computed by the leader robot. Both these problems are solved by token passing so as to reduce communication load on both the leader and the follower robots. The introduction of token passing makes it a weakly centralized framework thereby reducing the burden on the leader robot.