Department of Electrical Engineering

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In the literature on psychophysics, it is reported that during a psychophysical experiment when a user is subjected to many trials in succession, the perception of the current trial is observed to be overly similar to the previous trial (assimilation effect), and is observed to be dissimilar to distantly past trials (contrast effect). Overall, this behavior is called the sequential effect and is a very well-established phenomenon in psychophysics. In the literature, the sequential effect has been demonstrated on loudness of sound, and has been further assumed for other perceptual modalities like haptics and vision. However, to the best of our knowledge, we have not found any experimental study either claiming its existence for kinesthetic perception or for quantifying the effect. This motivates us to study the sequential effect on kinesthetic perception. In this chapter, we take up this study and find out whether or not the sequential effect exists, and how to quantify the effect. In order to study the presence of sequential effect for kinesthetic perception, we design an experimental setup where a user is subjected to a series of random force stimuli. We record the responses for several users. Thereafter, a logistic regression model is employed to observe how much the recorded responses are affected by the past stimuli. Based on the results of the logistic regression model, we demonstrate the presence of sequential effect for the kinesthetic stimuli. We also explain how to quantify the duration over which the sequential effect persists. © 2018, Springer Nature Singapore Pte Ltd.

World University root node

Studies in Computational Intelligence

Sequential effect on kinesthetic perception

A substantial pulsation of the second-order harmonic current ripple with angular frequency $2\omega$ is reflected at the input of a single-phase inverter when loads are supplied at its output with angular frequency $\omega$. Moreover, this ripple back-propagates and injects into the source in the absence of a bulky dc-link passive filter, an active compensator or a suitable digital controller with a front-end converter in the two-stage converter. This paper proposes a new adaptive sliding mode control for a two-stage dc-dc-ac converter to reduce proliferation of ripple without compromising dynamic performance. The front-end boost converter in the considered two-stage converter interfaces a battery bank and single-phase inverter fed loads. The control shapes the output impedance of the boost converter to reduce the ripple component at battery input. Second, the proposed controller achieves good dynamic performance at line and load transients. A fast voltage recovery with small undershoot/overshoot can be achieved at transients using the proposed controller. The proposed technique is validated using a hardware of the 1-kW two-stage converter. © 1982-2012 IEEE.

IEEE Transactions on Industrial Electronics

Ripple Mitigation with Improved Line-Load Transients Response in a Two-Stage DC-DC-AC Converter: Adaptive SMC Approach

Motion estimation is one of the most crucial and time-consuming component of video compression methods. However, much research has been done to improve computational complexity at the expense of the loss in performance of matching of blocks. A novel block matching algorithm named efficient direction-oriented search is proposed. For this, the proposed algorithm firstly aims to dynamically switch between search regions based on the location of minimum distortion error. The search region dimension is also made adaptive for faster convergence. Then the computational complexity is reduced by using a proposed horizontal, vertical wings diamond search pattern and, two ±45° inclined hexagon-shaped direction-oriented search patterns. For further speed-up in the search process, partial distortion calculations are employed. A method for optimal threshold value selection based on the distortion statistics for different partial distortion calculations is presented. The performance of the proposed algorithm is evaluated for different video sequences containing: slow, medium, fast, and directional motion content. The experimental results indicate that significant improvement in speed-up can be achieved while maintaining the better peak signal-to-noise-ratio performance. For directional motion video sequences, the proposed method even outperforms the full search algorithm with a significantly lower computational cost. © 2018, The Institution of Engineering and Technology.

IET Image Processing

Efficient direction-oriented search algorithm for block motion estimation

In this paper we present the design and implementation of autopilot tracking control law for Micro Aerial Vehicle using the second order sliding mode approach. The inner loop attitude tracking control design is carried out using output feedback based second order sliding mode technique, to ensure finite time convergence of the tracking error dynamics. While addressing tracking control of a time varying reference signal, it is important to investigate the stability characteristics of the internal dynamics to ensure perfect tracking. This paper mainly addresses the output tracking control problem for a MAV and investigate the stability characteristics of the longitudinal zero dynamics during tracking. We have proposed a stability proof based on Lyapunov theory to analyze the stability of the MAV longitudinal zero dynamics during tracking. A nonlinear aircraft model obtained using aerodynamic derivatives of The Blackkite 300 mm wingspan fixed MAV is used for both control design and as well as to verify its performance against the classical control methods. Extensive hardware in-loop simulation results of the proposed control algorithm implemented on the commercially available PX4 based Pixhawk autopilot board are also presented here. © 2017, Springer Science+Business Media B.V.

Journal of Intelligent and Robotic Systems: Theory and Applications

Design and Hardware Implementation of Autopilot Control Laws for MAV Using Super Twisting Control

Control with limited resources has been studied extensively since the last decade to optimize the system performance in terms of economic and practical constraints Brockett and Liberzon (IEEE Trans Autom Control 45:1279–1289, 2000 [8]), Elia and Mitter (IEEE Trans Autom Control 46:2458–2462, 2008 [9]). In many practical applications, the state measurements available at the controller end are quantized values and the control is designed based on these quantized measurements. © Springer International Publishing AG, part of Springer Nature 2018.

Studies in Systems, Decision and Control

Event-triggered sliding mode control with quantized state Measurements

Event-triggered control is a novel control implementation strategy where control signal is updated in aperiodic manner such that the stability of the system is retained. Here, event condition is continuously monitored to generate the triggering instant. So, this minimizes resource utilization and control effort while achieving certain control objective. Recently, event-triggered sliding mode control (SMC) is proposed in [25, 31] to ensure the robust stability in the presence of disturbance. In this strategy also, the plant state is continuously monitored for generating possible triggering instant. In order to avoid this continuous measurement, we propose an event-triggering strategy which evaluates the event at periodic interval only known as discrete event-triggered control. This strategy is very appealing if the state measurements are available only at periodic intervals. Here, with this discrete state measurements, the discrete event-triggered SMC is designed to guarantee the system stability. The event is detected only at periodic intervals and the control signal is updated whenever it is violated at these periodic instants. So, there is always a guaranteed lower bound for inter event time which is the time between two sampled measurements. Simulation results are given to demonstrate the efficacy of the proposed technique. © Springer International Publishing AG 2018.

Discrete event-triggered sliding mode control

In this paper, a method to design the reduced-order sliding-mode control is proposed for the robust output tracking of an arbitrary signal for nonminimum-phase systems. The main contributions in this paper include the design of the reduced-order switching function that ensures the asymptotic tracking of an arbitrary reference signal during sliding motion, the design of the reduced-order sliding-mode controller that enforces the sliding motion in finite time, and the computation of bounds on stable and virtually stable zero dynamics that is required for the output tracking. To show the effectiveness of the proposed design method, results of implementation on the experimental setup of an inverted pendulum system are also presented here. © 1996-2012 IEEE.

Fulltext

IEEE/ASME Transactions on Mechatronics

Output Tracking of Nonminimum-Phase Systems via Reduced-Order Sliding-Mode Design

We demonstrated an ultrahigh-performance and self-powered β-Ga2O3 thin film solar-blind photodetector fabricated on a cost-effective Si substrate using a high-temperature seed layer (HSL). The polycrystalline β-Ga2O3 thin film deposited with HSL shows high performance in the solar-blind region in comparison to the amorphous Ga2O3 thin film deposited without HSL. The zero-bias digitizing sensor prototype with an HSL produces a digitized output bit with deep UV (DUV) light that exhibits a high on/off (I254 nm/Idark) ratio of &gt;103, a record-low dark current of 1.43 pA, and high stability and reproducibility over 100 cycles even after &gt;2100 h. The photodetector shows minimum persistent photoconductivity and fast response in milliseconds. The photodetector yields a responsivity of 96.13 A W-1 with an external quantum efficiency of 4.76 × 104 at 5 V for 250 nm monochromatic light. The photodetector shows a high response to even a rare weak signal of DUV (44 nW/cm2). These values are the highest reported to date for a planar β-Ga2O3 thin film based photodetector despite the use of the cost-effective substrate. The asymmetric I-V curve indicates a dissimilar Schottky barrier height at the two ends of the MSM photodetector, which is discussed as the main reason for the high response even at zero bias. This work provides the guidelines to develop a β-Ga2O3-based cost-effective, self-powered, high-performance, and fast DUV photodetector that possesses a high potential for next-generation practical solar-blind photodetector application. © 2018 American Chemical Society.

ACS Photonics

Ultrahigh Performance of Self-Powered β-Ga2O3 Thin Film Solar-Blind Photodetector Grown on Cost-Effective Si Substrate Using High-Temperature Seed Layer

2D materials are a promising new class of materials for next generation optoelectronic devices owing to their appealing optical and electrical properties. Pristine molybdenum disulfide (MoS2) is widely used in next generation photovoltaic and optoelectronic devices, but its low photo-dark current ratio prevents its use in highly efficient photo detection applications. Here, we decorated crumpled reduced graphene oxide (rGO) particles on a large-area vertically aligned MoS2 flake network to enhance the performance of the MoS2-based photodetector by forming multiple nanoscale p-n heterojunctions. The rGO/MoS2 device exhibited a significantly improved photoresponsivity of ∼2.10 A W-1 along with a good detectivity of ∼5 ×1011 Jones (Jones = cm Hz1/2/W) compared to that of the pristine MoS2 photodetector in ambient atmosphere. Moreover, the rGO/MoS2 photodetector showed a fast response of ∼18 ms with excellent stability and reproducibility in ambient air even after three months. The high performance of the photodetector is attributed to enhanced photoexcited carrier density and suppressed photo generated electron-hole recombination due to the strong local built-in electric field developed at the rGO/MoS2 interface. Our results showed that integration of rGO with MoS2 provides an efficient platform for photo detection applications. © 2018 IOP Publishing Ltd.

Nanotechnology

High-performance photodetector based on hybrid of MoS2 and reduced graphene oxide

Gallium oxide nanocrystals encapsulated in Al2O3 film on a Si substrate have been synthesized by using ion implantation followed by thermal annealing at 800 degrees C or 900 degrees C. Formation of beta-Ga2O3 nanocrystals is confirmed by transmission electron microscopy. The photoresponse of a photodetector fabricated on the implanted layer by the deposition of interdigitated electrode pattern is estimated by analyzing the current-voltage characteristics. The ratio of photocurrent at the wavelength of 250 nm and a voltage of 4 V to dark current around similar to 15 is found for the sample annealed at 900 degrees C. The spectral dependence of photoresponse for this sample demonstrates excellent solar-blind ultraviolet characteristics in the wavelength range of 250-270 nm with a rejection ratio 42 at the bias of 1 V. At the bias of 4 V, the responsivity of 50 mA/mu W upon illumination at 250 nm and a cutoff at 280 nm are observed for the 900 degrees C annealing. The sample annealed at 800 degrees C shows lower ultraviolet responsivity due to the high density of defects. The data are analyzed in relation to the generation of carriers in Ga2O3 nanocrystals and their transport in the damaged Al2O3 matrix. The reported results pave the way toward the fabrication of next generation high sensitive solar-blind photodetectors.