Department of Electrical Engineering

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Tactical missiles are used against various aerial/ground targets which can be stationary or maneuvering. Tactical missiles should have highly efficient control scheme in order to intercept such targets with acceptable miss distance. It is known that aerodynamic characterization of the missile with high accuracy is very difficult. In addition to this, the inability to model the external disturbances make the autopilot design very difficult. Hence, the need for a robust control arises in the presence of parametric uncertainties and unmodelled external disturbances. Sliding Mode Control (SMC) which has got invariance property against external disturbances and the model inaccuracies has been applied to this plant. This paper concentrates on application of higher order sliding mode control for the roll autopilot design of a tactical missile. Conventionally, the roll autopilot is designed with roll angle and roll rate feedbacks. The addition of roll acceleration feedback helps to obtain a tighter control of roll dynamics especially during high angle of attack requirements. However, the roll acceleration is neither measurable nor estimable by numerical differentiation of roll rate feedback. A differentiator based on Super Twisting Algorithm (STA) is explored to estimate roll acceleration from roll rate measurement. The use of roll acceleration feedback in the autopilot ensures tight control of roll dynamics. The robust sliding mode control gains are designed using Linear Matrix Inequalities (LMI) based technique. © 2016 IEEE.

World University root node

2016 Indian Control Conference, ICC 2016 - Proceedings

Roll autopilot design of a tactical missile using higher order sliding mode technique

In this paper, flicker noise behavior of lateral non-uniformly doped MOSFET is studied using impedance field method. Our study shows that Klaassen Prins (KP) method, which forms the basis of noise model in MOSFETs, underestimates flicker noise in such devices. The same KP method overestimates thermal noise by 2-3 orders of magnitude in similar devices as demonstrated in Roy et al. (2007). This apparent discrepancy between thermal and flicker noise behavior lies in origin of these noises, which leads to opposite trend of local noise power spectral density vs doping. We have modeled the physics behind such behavior, which also explain the trends observed in the measurements (Agarwal et al., 2015). © 2015 Elsevier Ltd. All rights reserved.

Solid-State Electronics

Analysis and modeling of flicker noise in lateral asymmetric channel MOSFETs

The formulation of effective mobility for fully depleted silicon-on-insulator (FDSOI) transistors is a very challenging task. As vertical electric field (Eeff) changes it's sign from positive to negative according to the front and back channel dominance which results in non-unique relationship between Eeff and carrier distribution. This is the first time, when a predictive mobility model for wide range of back gate biases, solely dependent on technology parameters (front and back gate oxide thickness Tox/box, threshold voltage Vth, front/back gate bias Vfg/bg and flat-band voltage Vfb) is proposed. This predictive mobility model allows the user to predict the deviation in device characteristics due to the variations in the device structure. © 2016 IEEE.

2016 IEEE International Conference on Electron Devices and Solid-State Circuits, EDSSC 2016

Predictive effective mobility model for FDSOI transistors using technology parameters

In this letter, we present a unified compact model, which accurately captures carrier transport from the drift-diffusion to ballistic regime. This is a single unified model, which accounts for carrier degeneracy effects in ballistic transport. The model is implemented into the industry standard compact models for FinFETs, fully depleted silicon-on-insulator (FDSOI) devices and bulk MOSFETs: 1) Berkeley Spice model for common multi-gate; 2) Berkeley Spice model for independent multi-gate; and 3) BSIM6. The model is validated with experimental data and TCAD simulations for FDSOI devices, FinFETs, and bulk MOSFETs. © 1980-2012 IEEE.

IEEE Electron Device Letters

Unified compact model covering drift-diffusion to ballistic carrier transport

This paper presents a variable phase shifter in Substrate Intergrated Waveguide (SIW) technology for beam steering antenna application. With this design, the phase difference between antenna array elements can be varied which results in changing the direction of maximum radiation. The proposed structure is designed by interfacing of a 3 dB directional coupler and - 300 phase shifter. The optimized design produces 30% bandwidth at 10 GHz operating frequency. In the 8.5-11.5 GHz band, isolation between input ports is higher than 20 dB and the return loss is better than 15 dB. By changing the feeding port, the phase difference of 600±20 and 1190±1.50 between the direct and coupled port are achieved. This circuit is useful in beam steering radar application. © 2016 IEEE.

2016 IEEE Antennas and Propagation Society International Symposium, APSURSI 2016 - Proceedings

Design of SIW variable phase shifter for beam steering antenna application

In this paper, the design of microstrip patch antenna fed by Halfmode Substrate Integrated Waveguide (HMSIW) is presented. The proposed microstrip patch antenna is placed at an inset in the open end of the HMSIW separated by a narrow slot. The HMSIW is excited to generate dominant TE10HM mode. The amount of inset of the patch in the HMSIW helps to get impedance matching and as a result, the incident wave couples easily from HMSIW to patch antenna. The proposed antenna resonates at 10.5 GHz with the bandwidth of 500 MHz (4.76%) and cross polarization level lower than -21dB. © 2015 IEEE.

2015 IEEE Applied Electromagnetics Conference, AEMC 2015

Design of microstrip patch antenna using Half-Mode Substrate Integrated Waveguide feeding technique

In this letter, a novel design technique to realize planar self-diplexing slot antenna using substrate integrated waveguide (SIW) technology is presented. The proposed antenna uses a bowtie-shaped slot backed by SIW cavity, which is excited by two separate feedlines to resonate at two different frequencies in X-band (8-12 GHz). By properly optimizing the antenna dimensions, a high isolation of better than 25 dB between two input ports is achieved, which helps to introduce self-diplexing phenomenon in the proposed design. The behavior of the individual cavity modes at two resonant frequencies is explained using half-mode theory. The proposed antenna resonates at 9 and 11.2 GHz with unidirectional radiation pattern and a high gain of 4.3 and 4.2 dBi, respectively. © 2016 IEEE.

IEEE Antennas and Wireless Propagation Letters

Design of Self-Diplexing Substrate Integrated Waveguide Cavity-Backed Slot Antenna

The discrete application of a continuous control designed using continuous time model of a plant is common practice. The work in this chapter evaluates new conditions required to be satisfied by the parameters of a sliding mode control so designed, such that the plant response remains bounded under such discrete application of the control. This work is taken forward to propose a generalized reaching law for discrete time sliding mode designs. This generalized reaching law is more flexible in its choice of functions and parameters, enabling it to deal with potentially new problem scenarios. A new problem in which the disturbance affecting the system is bounded by known functions, instead of a constant bound, is solved utilizing this generalized reaching law. © The Institution of Engineering and Technology 2016.

Recent Trends in Sliding Mode Control

A generalized reaching law for discrete-time sliding mode

Seismocardiography (SCG) measures the precordial vibrations using a sensor called accelerometer, which is of small size and low weight. These features support better attachment of it to the subject's body and hence get less affected by the slow motion of the subject. However, noise generated due to the footsteps, while walking, contaminates the SCG signal. Therefore, in this paper, a novel method is proposed to remove these contaminations from the SCG signal. A three-Axis accelerometer was attached to the chest wall such that heart sound components are reflected in the z-Axis while the motion noise due to footstep will be seen in the x-Axis. To remove the noise components from the heart signal (z-Axis), the location of footsteps from the x-Axis are identified and the corresponding components from the z-Axis are removed. After noise removal fundamental heart sounds (FHS), S1 and S2, are identified using Otsu's threshold method. The obtained results show that the proposed algorithm outperforms the state-of-The-Art methods. It efficiently removes most of the contamination due to footsteps and identifies the heart sound components. © 2016 IEEE.

International Conference on Digital Signal Processing, DSP

A novel method for suppression of motion artifacts from the seismocardiogram signal

The paper presents an analysis of sliding mode control of discrete time systems with relative degree greater than one. The analysis leads us to obtain finite time stability of the output as well as the states of the system in absence of uncertainties, taking the output as the sliding variable. The simple equivalent control with state feedback guarantees this. In presence of uncertainties in the system model, the states and the output are ultimately bounded if the uncertainties are bounded in nature. It is also shown in the latter case, that the robustness of the output can be increased when the relative degree is more than one. © 2016 IEEE.