Hemanshu Pota - Profile on Academia.edu (original) (raw)

Papers by Hemanshu Pota

Robotics and Autonomous Systems, 2006

In automatic guidance of agriculture vehicles, lateral control is not the only requirement. Much ... more In automatic guidance of agriculture vehicles, lateral control is not the only requirement. Much research work has been focused on trajectory tracking control which can provide high longitudinal-lateral control accuracy. Satisfactory results have been reported as soon as vehicles move without sliding. But unfortunately pure rolling constraints are not always satisfied especially in agriculture applications where working conditions are rough and not predictable. In this paper the problem of trajectory tracking control of autonomous farm vehicles in the presence of sliding is addressed. To take sliding effects into account, three variables which characterize sliding effects are introduced into the kinematic model based on geometric and velocity constraints. With a linearized approximation, a refined kinematic model is obtained in which sliding effects appear as additive unknown parameters to the ideal kinematic model. By an integrating parameter adaptation technique with a backstepping method, a stepwise procedure is proposed to design a robust adaptive controller in which time-invariant sliding is compensated for by parameter adaptation and time-varying sliding is corrected by a Variable Structure Controller (VSC). It is theoretically proven that for farm vehicles subjected to sliding, the longitudinal-lateral deviations can be stabilized near zero and the orientation errors converge into a neighborhood near the origin. To be more realistic for agriculture applications, an adaptive controller with projection mapping is also proposed. Both simulation and experimental results show that the proposed (robust) adaptive controllers can guarantee high trajectory tracking accuracy regardless of sliding.

Generating Lyapunov functions for power system stability estimates

Construction of Lyapunov function for power system

... Actually, it frequently occurs that Gless's function offers better results for stability... more ... Actually, it frequently occurs that Gless's function offers better results for stability judgment under a system disturbance such as faults on transmission lines. The other is to simplify determination of the desired coefficients. ... [P(x,x)]Tdx Jo = r [F(X))Tdx Jo (7) ...

Power sharing in microgrids with minimum communication control

2015 IEEE Power & Energy Society General Meeting, 2015

A new approach for wind and solar type DG placement in power distribution networks to enhance systems stability

2012 IEEE International Power Engineering and Optimization Conference, 2012

ABSTRACT This paper proposes a distributed generator (DG) placement methodology based on newly de... more ABSTRACT This paper proposes a distributed generator (DG) placement methodology based on newly defined term reactive power loadability. The effectiveness of the proposed planning is carried out over a distribution test system representative of the Kumamoto area in Japan. Firstly, this paper provides simulation results showing the sensitivity of the location of renewable energy based DG on voltage profile and stability of the system. Then, a suitable location is identified for two principal types DG, i. e., wind and solar, separately to enhance the stability margin of the system. The analysis shows that the proposed approach can reduce the power loss of the system, which in turn, reduces the size of compensating devices.

Current Status and Issues of Concern for the Integration of Distributed Generation Into Electricity Networks

ABSTRACT As existing distribution networks were designed to deliver unidirectional power to consu... more ABSTRACT As existing distribution networks were designed to deliver unidirectional power to consumers and require minimal control intervention, they result in largely passive infrastructures. The installation of distributed generation (DG) units with significant capacity in these passive networks can cause reverse power flows, which will result in some conflicts with the operation of the existing protection system. In this context, utilities around the world have started establishing requirements to ensure safe and reliable interconnection of generators in low- and medium-voltage networks. The technical grid code requirements and regulations vary considerably from country to country. However, any standard should address the critical need to make the DG marketable by providing uniform criteria and requirements relevant to the performance, operation, and safety. This paper presents a critical review of the requirements adopted by distribution companies in selected countries, such as the U.S., the U.K., Germany, and Australia, to facilitate the connection of DG. The main problems, such as voltage regulation, islanding operation, and dynamic interactions among DG and loads, are discussed to identify a few points where attention is still needed to improve the reliability of distribution systems.

European Journal of Control, 2013

In this paper, the problem of practical stability of some classes of continuous-time switched sys... more In this paper, the problem of practical stability of some classes of continuous-time switched systems is studied. The main results of this paper include some sufficient conditions concerning practical stability of continuous-time switched nonlinear systems without a common equilibria for all subsystems. In this class of switched systems, the equilibrium point varies discontinuously according to a time-dependent switching signal. So, stability with respect to a set, rather than a particular point, is discussed. Using this preliminary result, we present sufficient conditions in the form of linear matrix inequalities (LMIs) for practical stability of a particular class of switched systems without common equilibria: the switched affine systems. An illustrative example in the power system stability area is presented to show the validity of the results.

2007 46th IEEE Conference on Decision and Control, 2007

This work presents the derivation of a comprehensive mathematical model for an off-road vehicle s... more This work presents the derivation of a comprehensive mathematical model for an off-road vehicle such as an agricultural tractor that drags behind it a heavy implement. The models are being developed with the aim of designing robust controllers that will enable the high precision control of the implement's trajectory. The developed model is subjected to real conditions, such as ground undulation and uncertainty, sloping terrain, tyre slippage, and constrained steering of the tractor. The implement is assumed to possess independently steered wheels for aiding in implement alignment. A complete model is presented and simulated under varying conditions. Primarily this work demonstrates and validates the trailed vehicle system behavior when the trailing implement is subjected to large drag forces due to ground engagement and the significantly large lateral disturbances that occur in real life broad acre farming conditions.

2008 American Control Conference, 2008

This paper presents a novel application of backstepping controller for landing of a Rotary wing U... more This paper presents a novel application of backstepping controller for landing of a Rotary wing UAV (RUAV) using a tether. This algorithm is an extension of a backstepping algorithm for general rigid bodies. In this paper, we will also present the detailed analysis of flapping correction dynamics by considering the practicality involved in the system. The performance of the proposed algorithm is demonstrated by simulation results. Future work is needed to implement the algorithm onboard RUAV platforms.

Agricultural robotics: A streamlined approach to realization of Autonomous Farming

2007 International Conference on Industrial and Information Systems, 2007

This paper presents a streamlined approach to future Precision Autonomous Farming (PAF). It focus... more This paper presents a streamlined approach to future Precision Autonomous Farming (PAF). It focuses on the preferred specification of the farming systems including the farming system layout, sensing systems and actuation units such as tractor-implement combinations. The authors propose the development of the Precision Farming Data Set (PFDS) which is formed off-line before the commencement of the crop cultivation and

Resonant controllers for flexible structures

Proceedings of the 38th IEEE Conference on Decision and Control (Cat. No.99CH36304), 1999

Abstract Proposes a special type of colocated feedback controllers for flexible structures. The c... more Abstract Proposes a special type of colocated feedback controllers for flexible structures. The controllers are a parallel combination of high-Q resonant circuits. Each resonant circuit is tuned to a pole (or the resonant frequency) of the flexible structure. Experimental results ...

Distribution grid codes: Opportunities and challenges

2013 IEEE Grenoble Conference, 2013

ABSTRACT Traditional distribution networks were not originally designed to accommodate power gene... more ABSTRACT Traditional distribution networks were not originally designed to accommodate power generation facilities. The installation of distributed generation (DG) units with significant capacity in these passive networks can cause reverse power flows which will result in some conflicts with the operation of the existing protection system. In this context, utilities around the world have started establishing requirements to ensure safe and reliable interconnection of generators in low- and mediumvoltage networks. Grid interconnection is presently one of the most important issues involving DG. This paper presents a critical review of the requirements adopted by distribution companies in selected countries such as the USA, the UK, Germany and Australia to facilitate the connection of DG. Critical issues such as voltage regulation, islanding operation, dynamic interactions among DG and loads are discussed to identify a few points where attention is still needed to improve the reliability of distribution systems.

Dynamic Compensation for Control of a Rotary wing UAV Using Positive Position Feedback

Journal of Intelligent & Robotic Systems, 2011

This paper presents a novel compensation method for the coupled fuselage-rotor mode of a Rotary w... more This paper presents a novel compensation method for the coupled fuselage-rotor mode of a Rotary wing Unmanned Aerial Vehicle (RUAV). The presence of stabilizer bar limits the performance of attitude control of an RUAV. In this paper, a positive position feedback (PPF) is introduced to increase the sta- bility margins and allow higher control bandwidth. The identified model is used

IEEE Transactions on Power Systems, 1989

Recently the authors incorporated the effect of excitation control on the transient energy of a m... more Recently the authors incorporated the effect of excitation control on the transient energy of a multimachine power system during the first swing transient [11. There are strong motivations for improving the synchronous machine model applicable for first swing analysis. Among these we cite: 1. Modern excitation systems are powerful and can act extremely fast. Therefore, they can substantially alter the generator flux during the first swing transient. 2. Present day interconnected power networks are often operated close to their stability limits. Not only accurate modeling is needed for correct stability classification, but also certain problems may have a first swing in the order of several seconds. Examples are loss of generation transient and disturbances causing the so-called interarea mode. 3. The variety of stability-related problems analyzed in modern power systems makes it difficult to justify the constant flux linkage idea. In this paper the parameters of the newly developed transient energy function are computed. The critical value of this transient energy is determined, and its use, in transient stability assessment is investigated.

IEEE Power and Energy Society General Meeting, USA 2012

In this paper, a methodology for determining optimum generation capacity of multiple distributed ... more In this paper, a methodology for determining optimum generation capacity of multiple distributed generation (DG) units is presented. The proposed method is based on unbalanced three-phase optimal power flow (TOPF) using particle swarm intelligence. To solve the optimum generation capacity problem, a co-simulation platform has been used under the MATLAB and OpenDSS environment. An adaptive weight particle swarm optimization algorithm has been developed in MATLAB and the unbalanced three-phase distribution load flow (DLF) has been performed using Electric Power Research Institute's (EPRI) open source tool OpenDSS. The analysis is carried out on IEEE 123 node distribution test feeder for three different DG technologies. The results obtained from the proposed method have been compared with the results obtained from a 'brute-force search' method. This analysis shows that the proposed method finds out the optimum solution successfully while computational complexity and time is reduced extensively. Using multiple DG units with optimum generation capacity, power loss of the network is reduced significantly while voltage profile remains within stability margin.

Distributed generation (DG) units reduce electric power losses and hence improve reliability and ... more Distributed generation (DG) units reduce electric power losses and hence improve reliability and voltage profile. Determination of appropriate size and location of DG is important to maximize overall system efficiency. In this paper, an optimization method has been presented to determine the appropriate size and proper allocation of DG in a distribution network. Results obtained from this method have been compared with using the repeated load flow method. A new approach to perform repeated load flow by using simulation engine 'openDSS' COM server through Matlab programming is also introduced here. Both optimized method and repeated load flow based method have been compared for three IEEE distribution test systems. This analysis shows that using appropriate size and location of DG, total power loss in primary distribution system can be reduced significantly.

In this paper, two generalized algorithms are presented for sizing and allocating distributed gen... more In this paper, two generalized algorithms are presented for sizing and allocating distributed generation (DG) units. To determine the size and location of a single DG unit, a heuristic method based on sensitivity analysis and quadratic curve fitting technique has been proposed. Another heuristic technique based on a loss improvement index has been introduced for allocation of multiple DG units. These studies are carried out using two IEEE test distribution systems which are multi-phase and unbalanced in nature. This analysis shows that the use of appropriate size and location of DG reduces total power loss in a distribution system significantly and hence improve the steady-state voltage profile. Methodologies described in this paper gives the distribution system planner an idea about the size and location DG unit which would be the most beneficial in terms of system efficiency and stability.

Output Feedback Control Design for Interconnected Power Systems with OLTCs via Robust Decentralized Control

This paper addresses the problem of designing an output feedback decentralized control of interco... more This paper addresses the problem of designing an output feedback decentralized control of intercon- nected power systems under large changes in real and reactive loads that cause large structural changes in the system model. The controller uses only the speed of the generator as its input. On load tap changers are also incorporated in the model and in the controller design. The design is carried out within a large-scale Markov jump parameter systems framework. This has allowed for a robust guaranteed performance con- troller to be designed. Simulations were carried out to eval uate the performance of the designed controller and to compare it with state feedback controllers.

A new procedure for modeling nonlinear systems via norm-bounded linear differential inclusions

ABSTRACT There are several advantages of using linear differential inclusions (LDIs) to describe ... more ABSTRACT There are several advantages of using linear differential inclusions (LDIs) to describe nonlinear systems and other types of complex systems (such as, systems with time-varying uncertainties and/or saturation). From the control point of view, for example, it may be easier to design a controller for a nonlinear system by using a linear description of it in the form of an LDI (instead of using the nonlinear equations for the same purpose). With this premise, we focus on modeling of a class of nonlinear systems via a norm-bounded LDI (NLDI) model. One of the main contributions of the proposed modeling approach is the use of the mean-value theorem to represent the nonlinear system by a linear parameter-varying (LPV) model, which is then mapped into a polytopic LDI (PLDI) within the region of interest. To avoid the combinatorial problem that is inherent of polytopic models for medium- and large-sized systems, the PLDI is transformed into an NLDI, and the whole process is carried out ensuring that all trajectories of the underlying nonlinear system are also trajectories of the resulting NLDI within the operating region of interest. Furthermore, it is also possible to choose a particular structure for the NLDI parameters to reduce the conservatism in the representation of the nonlinear system by the NLDI model, and this feature is also one of the main contributions of this paper. A numerical example is presented at the end of this paper to demonstrate the effectiveness of this approach.

The application of a new technique, based on the theory of Markov Jump Parameter Systems (MJPS), ... more The application of a new technique, based on the theory of Markov Jump Parameter Systems (MJPS), to the problem of designing controllers to damp power system oscillations is presented in this paper. This problem is very difficult to address, mainly because these controllers are required to have an output feedback decentralized structure. The technique relies on the statistical knowledge about the system operating conditions to provide less conservative controllers than other modern robust control approaches. The influence of the system interconnections over its modes of oscillation is reduced by means of a proper control design formulation involving Integral Quadratic Constraints. The discrete nature of some typical events in power systems (such as line tripping or load switching) is adequately modeled by the MJPS approach, therefore allowing the controller to withstand such abrupt changes in the operating conditions of the system, as shown in the results.