Department of Electrical Engineering

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IIT Jodhpur

In this paper, we study the collective motion of individually controlled planar particles when they are coupled through heterogeneous controller gains. Two types of collective formations, synchronization and balancing, are described and analyzed under the influence of these heterogeneous controller gains. These formations are characterized by the motion of the centroid of the group of particles. In synchronized formation, the particles and their centroid move in a common direction, while in balanced formation the movement of particles possess a fixed location of the centroid. We show that, by selecting suitable controller gains, these formations can be controlled significantly to obtain not only a desired direction of motion but also a desired location of the centroid. We present the results for N-particles in synchronized formation, while in balanced formation our analysis is confined to two and three particles. © 2013 AACC American Automatic Control Council.

World University root node

Proceedings of the American Control Conference

Collective behavior with heterogeneous controllers

As of now, nuclear reactors all over the world employ output feedback controllers for control of total power and spatial power distribution. An output feedback controller can be designed through a conventional approach, e.g., by plotting the root loci of the system. This is demonstrated in this chapter with application to the 17 node AHWR model. © 2013, Springer-Verlag Berlin Heidelberg.

Lecture Notes in Control and Information Sciences

Output feedback control design

In this paper, a suboptimal flow controller design for connection-oriented communication network via reduced model is proposed. Network is modeled as an nth order discrete system whose available bandwidth variations at the bottlenecked link act as an exogenous unmatched disturbance. The proposed scheme is characterized by a simple first order design which is applied to nth order systems through aggregation. Effect of bandwidth variation at the congested node which is modeled as a disturbance, is well accounted in controller design with widely adopted delay-based disturbance estimation. Performance of the proposed scheme is validated through Matlab and ns simulations. Simulation results shows that all the proposed reduced order control scheme tracks the desired queue length effectively under the adverse influence of unmatched disturbances. © 2013 IEEE.

IEEE International Conference on Industrial Informatics (INDIN)

Discrete-time flow control for connection-oriented communication network via reduced model

In this technical note, a novel methodology for robust finite-time stabilization of a chain of uncertain fractional order integrator is proposed. This is achieved by first designing a nominal controller which stabilizes the system in finite time. An integral sliding-mode like surface and a switching controller is proposed such that when the system is on the surface the equivalent value of the integral sliding-mode control is the negative of the disturbance and hence the disturbance is cancelled. An improved strategy with more general kind of uncertainty is also proposed. Numerical examples are presented to illustrate the proposed methods. © 1963-2012 IEEE.

IEEE Transactions on Automatic Control

Finite-time stabilization of fractional order uncertain chain of integrator: An integral sliding mode approach

A Stewart platform manipulator is 6 degrees of freedom parallel robot with a superior performance over serial robots. The forward kinematic problem of a Stewart platform is to determine the actual position and orientation of the movable platform with respect to the base for a given set of leg lengths. The existing analytical methods to solve this problem give multiple solutions, out of which an exact and practical solution has to be selected. A novel method based on non linear autoregressive model with exogenous input (NLARX) using wavelet network is proposed in this paper for the identification of forward kinematic model of a Stewart platform. For a given position of the platform, the leg lengths are estimated using inverse kinematics. This information is used to identify and validate the NLARX model. The simulation results show the ability of the estimated NLARX model to represent the dynamic behavior of the Stewart platform in the forward kinematic mode. © 2013 IEEE.

The forward kinematic modeling of a Stewart platform using NLARX model with wavelet network

Sliding mode control is a well established non-linear control technique which ensures a robust performance in presence of matched uncertainties and disturbances. The only shortcoming of this control strategy is that the control signal generated, which provides the robustness is highly discontinuous and may lead to chattering. Recent advances in higher order sliding mode control indicate that the use of second order sliding mode control ensures the basic advantages of sliding mode control, that of robustness while maintaining continuous and chatter-free control. The super twisting algorithm which is the most popular second order sliding mode control can provide for finite time convergence against the matched uncertainties only. Here, a methodology has been proposed so that this algorithm can be extended to cater for unmatched uncertainties, particularly those arising from uncertain system matrix A. The proposed scheme is then applied for roll control of missile. Copyright © 2013 Inderscience Enterprises Ltd.

International Journal of Automation and Control

Roll autopilot design using second order sliding mode

Singular perturbation methods have successfully been used in control applications to deal with multi-time-scale systems, by which the system is decomposed into a ‘slow’ subsystem and one or more ‘boundary layer’ or ‘fast’ subsystems[56]. A system expressed in explicit singularly perturbed form generally has a small parameter ε appearing as a multiplier to the derivative of the ‘fast’ variables. Here, the system decomposition is achieved by setting ε =0 and solving for the ‘fast’ subsystem variables in terms of the ‘slow’ ones, and then substituting them in the ‘slow’ subsystem equations[58]. © 2013, Springer-Verlag Berlin Heidelberg.

Direct block diagonalization and composite control of three-time-scale systems

Here, we report high voltage MOSFET modeling using BSIM6 model. The model has two components - intrinsic MOSFET channel of LDMOS modeled by BSIM6 and a drift region modeled by non-linear drift resistance. BSIM6 is the next generation bulk MOSFET model in BSIM family of models. It also have the model of Self Heating Effect (SHE) which is very important for high power devices like LDMOS. This model shows good behaviour over wide range of gate and drain bias conditions including convergence. Some of the effects like Quasi-saturation, self-heating and impact ionization are modelled by the combination of BSIM6 and drift-resistance models. We have validated this model on the simulated characteristics generated by TCAD and then, on the measured characteristics of a LDMOS device, where it shows excellent accuracy over entire bias range. © 2013 IEEE.

Asia Pacific Conference on Postgraduate Research in Microelectronics and Electronics

High voltage LDMOSFET modeling using BSIM6 as intrinsic-MOS model

The temperature dependent electrical transport behavior of n-n InGaN/Si heterostructures grown by plasma-assisted MBE was studied. Structural characteristics of the as-grown InGaN epilayers were evaluated high resolution X-ray diffraction and composition of InGaN was estimated from photoluminescence spectra using standard Vegard's law. Current density-voltage plots (J-V-T) revealed that the ideality factor (η) and Schottky barrier height (SBH) (Φ b) are temperature dependent and the incorrect values of the Richardson's constant (A) produced, suggests an inhomogeneous barrier at the heterostructure interface. The higher value of the ideality factor compared to the ideal value and its temperature dependence suggest that the current transport is mainly dominated by thermionic field emission. © 2012 Elsevier B.V. All rights reserved.

Current Applied Physics

Electrical transport studies of MBE grown InGaN/Si isotype heterojunctions

This paper proposes a protection scheme against voltage sag, swell, over voltage and under voltage to address the difficulties faced due to voltage fluctuations. Voltage sag and swells in the supply are detected and the relay circuit operates accordingly. This relay circuit along with a simulated graph has been shown. The passage of current through the circuit to be protected is allowed to flow only when no faults are observed. Hence the protective relay circuit prevents the output load from the hazardous effects of overvoltage and under voltage. © 2013 IEEE.