Dr. Shikha Tripathi joined Amrita Vishwa Vidyapeetham, School of Engineering, Bangalore campus, in July 2009. Currently, she is serving as Professor & Chairperson, Department of Electronics & Communication Engineering. Prior to this, she was working as Group Leader (Head), Electronics & Instrumentation Group at BITS Pilani, Pilani campus. She was at BITS, Pilani from 1998 to 2009. She was with Tata Consultancy Services, Mumbai as Assistant System Analyst during 1992 and 1993 and Faculty Member, Department of Electronics & Communication Engineering, Bangalore University during 1994 to 1997.

Her research interests include wavelet based Image Compression, image watermarking, Digital Signal/image Processing, Architectures for transforms used in signal processing applications and Control algorithms for robotics. Currently she is working on emotion recognition from speech & face, music signal processing using wavelets, architectures for multi transforms used in signal/image processing applications and control algorithms for stability of biped robots walking on uneven/flexible terrains.

She is reviewer for many journals and conferences of repute in India and abroad.

Administrative Activities at Amrita University

  • Chairperson, Department of Electronics & Communication Engineering (July 2011- Present)
  • Vice-Chairperson, Department of Electronics & Communication Engineering (July 2010-June 2011)
  • Chairman, BOS, Undergarduate Programs (ECE & EIE)
  • Chairman, BOS, Postgraduate Program (CESP)
  • Member, BOS, Postgraduate Program (VLSI)
  • Professor-in-charge, ECI Student Forum (February 2010 - June 2011)
  • Member & Convener, Institute Consultative Committee since April 2010
  • Member, Library Committee (June 2010 - June 2011)
  • Fest Chair, Aarohan, Amrita Science Fest ( in January 2010 & October 2010)



  • International Conference on Power and Energy Systems: Towards Sustainable Energy (PESTSE 2014), 13-15, March,2014, IEEE PES
  • International Conference on VLSI Systems, Architecture, technology and Applications (VLSI-SATA 2015), 8-10, January 2015, IEEE CAS, IEEE CS, IEEE Bangalore Section
  • International Conference on VLSI Systems, Architecture,Technology and Applications (VLSI-SATA 2016) – 2nd Edition, 10-12, January 2016, IEEE CAS, IEEE Bangalore Section


  • National Workshop on Trends and Developments in Sensors and Instrumentation(TDSI 2011), 8-9, April 2011, sponsored by National Instruments.
  • National Workshop on Trends and Developments in Signal Processing and Applications (TDSPA2013), 27th - 28th April 2013, in association with Texas Instruments
  • National Workshop on Electronic System Level Design and Verification (ESLDV 2014), 14th-15th November 2014, sponsored and supported by Bluespec,AMD,ARM Synopsys,Intel,Mentor Graphics,CVC
  • National Workshop on Trends and Development in Photonics and Optical Communication (TDPOC 2016), 28–29, March 2016, sponsored by IEEE Photonic Society and supported by Fiber Optic Services Pvt. Ltd. and IEEE COMSOC
  • Workshop on ‘5G Internet of Things’ together with GISFI standardization series meetings, 21st to 23rd July 2016, sponsored by GISFI, supported by IEEE COMSOC

Professional Bodies/Societies

  • Member, IEEE, USA, RAS
  • Member, ACM, USA
  • Member, Systers, USA (Women in technical aspects of computing)
  • Senior Member, International Association of Computer Science and Information Technology, USA
  • Life Member, ISTE, India


Publication Type: Journal Article
Year of Conference Publication Type Title
2016 Journal Article B. Akanksh, Vekkot, S., and Tripathi, S., “Interconversion of emotions in speech using TD-PSOLA”, Advances in Intelligent Systems and Computing, vol. 425, pp. 367-378, 2016.[Abstract]

Emotional speech plays a major role in identifying the mental state of the speaker. The presented work demonstrates the significance of incorporating dynamic variations in prosodic parameters in speech for the effective conversion of one emotion to another. Most existing methods focus on the incorporation of emotions in synthetically generated neutral speech. The proposed model discusses the usage of TD-PSOLA as an important tool in converting one emotion to another for speech samples in English language. It analyses the significance of various prosodic parameters in distinct emotions and explores how prosodic modifications to one emotion can result in different perceived emotions. The paper explores a technique for interconversion of emotions in synthesised speech and demonstrates a methodology for prosodic modifications on an English database. © Springer International Publishing Switzerland 2016.

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2016 Journal Article S. Vekkot and Tripathi, S., “Inter-emotion conversion using dynamic time warping and prosody imposition”, Advances in Intelligent Systems and Computing, vol. 530, pp. 913-924, 2016.[Abstract]

The objective of this work is to explore the importance of parameters contributing to synthesis of expression in vocal communication. The algorithm discussed in this paper uses a combination of Dynamic Time Warping (DTW) and prosody manipulation to inter-convert emotions among one another and compares with neutral to emotion conversion using objective and subjective performance indices. Existing explicit control methods are based on prosody modification using neutral speech as starting point and have not explored the possibility of conversion between inter-related emotions. Also, most of the previous work relies entirely on perception tests for evaluation of speech quality post synthesis. In this paper, the objective comparison in terms of error percentage is verified with forced choice perception test results. Both indicate the effectiveness of inter-emotion conversion by speech with better quality. The same is also depicted by synthesis results and spectrograms. © Springer International Publishing AG 2016. More »»
2015 Journal Article P. Suja and Tripathi, S., “Analysis of emotion recognition from facial expressions using spatial and transform domain methods”, International Journal of Advanced Intelligence Paradigms, vol. 7, pp. 57-73, 2015.[Abstract]

Facial expressions are non-verbal signs that play an important role in interpersonal communications. There are six basic universally accepted emotions viz., happiness, surprise, anger, sadness, fear and disgust. An emotion recognition system is used for recognising different expressions from the facial images/videos and classifying them into one of the six basic emotions. Spatial domain methods are more popularly used in literature in comparison to transform domain methods. In this paper, two approaches viz., cropped face and whole face methods for feature extraction are implemented separately on the images taken from Cohn-Kanade (CK) and JAFFE databases. Classification is performed using K-nearest neighbour and neural network. The results are compared and analysed. The results suggest that transform domain techniques yield better accuracy than spatial domain techniques and cropped face approach outperforms whole face approach for both the databases for few feature extraction methods. Such systems find application in human computer interaction, entertainment industry and could be used for clinical diagnosis. Copyright © 2015 Inderscience Enterprises Ltd.

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2015 Journal Article I. Mamatha, T.S.B. Sudarshan, Tripathi, S., and Bhattar, N., “Triple-Matrix Product-Based 2D Systolic Implementation of Discrete Fourier Transform”, Circuits, Systems, and Signal Processing, vol. 34, pp. 3221–3239, 2015.[Abstract]

Realization of N -point discrete Fourier transform (DFT) using one-dimensional or two-dimensional systolic array structures has been developed for power of two DFT sizes. DFT algorithm, which can be represented as a triple-matrix product, can be realized by decomposing N into smaller lengths. Triple-matrix product form of representation enables to map the N -point DFT on a 2D systolic array. In this work, an algorithm is developed and is mapped to a two-dimensional systolic structure where DFT size can be non-power of two. The proposed work gives flexibility to choose N for an application where N is a composite number. The total time required to compute N -point DFT is 2 ( N 1 - 1 ) + N 2 + N for any N = N 1 N 2 . The array can be used for matrix–matrix multiplication and also to compute the diagonal elements of triple-matrix multiplication for other applications. The proposed architecture produces in-order stream of DFT sequence at the output avoiding need for reordering buffer. Large sized DFT can be computed by repeatedly using the proposed systolic array architecture. More »»
2013 Journal Article S. Kochuvila, Tripathi, S., and Sudarshan, T. S. B., “Stability of an Underactuated Passive Biped Robot Using Partial Feedback Linearization Technique”, Applied Mechanics and Materials, vol. 394, pp. 456–462, 2013.[Abstract]

This paper discusses the problem of achieving stable walking of a compass gait biped robot on a slope. A reference trajectory for stable walking is generated using Lagrangian dynamics of the biped robot. It is shown that an underactuated robot can follow the reference trajectory using a control law based on feedback linearization with respect to both hip and ankle joints. The results are compared in terms of Mean Square Error (MSE). The validity of the proposed controller is carried out using simulation studies.

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2013 Journal Article R. Karthikeyan, Bhargav, C., Koneru, K., Syam, G., and Tripathi, S., “Enhanced Model Reference Adaptive Control Using Smith Predictor”, Applied Mechanics and Materials, vol. 367, pp. 363–368, 2013.[Abstract]

<p>The main aim of a control system is to repress the instabilities caused by nonlinearities of the system. Dead time is considered to be one of the most significant nonlinearities of a system. Dead time compensators play a vital role in reducing the dead time effects on the processes only to a minute extent. This paper proposes a method to overcome this problem by using Enhanced Model Reference Adaptive Control (MRAC) incorporating Smith Predictor. MRAC belongs to class of adaptive servo system in which desired performance is expressed with the help of a reference model. Enhanced MRAC consists of a fuzzy logic controller which provides adaptation gain to MRAC without human interference. A dead time compensator incorporated in the enhanced MRAC solves the problem of instabilities caused by dead time to a greater extent.</p>

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2013 Journal Article Ra Karthikeyan, Manickavasagam, Kb, Tripathi, S., and Murthy, K. V. Vc, “Neuro-fuzzy-based control for parallel cascade control”, Chemical Product and Process Modeling, vol. 8, 2013.[Abstract]

<p>This paper discusses the application of adaptive neurofuzzy inference system (ANFIS) control for a parallel cascade control system. Parallel cascade controllers have two controllers, primary and secondary controllers in cascade. In this paper the primary controller is designed based on neuro-fuzzy approach. The main idea of fuzzy controller is to imitate human reasoning process to control ill-defined and hard to model plants. But there is a lack of systematic methodology in designing fuzzy controllers. The neural network has powerful abilities for learning, optimization and adaptation. A combination of neural networks and fuzzy logic offers the possibility of solving tuning problems and design difficulties of fuzzy logic. Due to their complementary advantages, these two models are integrated together to form more robust learning systems, referred to as adaptive neuro-fuzzy inference system (ANFIS). The secondary controller is designed using the internal model control approach. The performance of the proposed ANFIS-based control is evaluated using different case studies and the simulated results reveal that the ANFIS control approach gives improved servo and regulatory control performances compared to the conventional proportional integral derivative controller.</p>

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2012 Journal Article S. Kochuvila, Tripathi, S., and T.S.B, S., “Compass Gait Biped Robot Based on Partial Feedback Linearization”, Advances in Autonomous Robotics, Lecture Notes in Computer Science (LNCS),Springer Link, vol. 7429/2012, no. 117-127, 2012.
2011 Journal Article S. Tripathi, Chandalia, H. Bac, Rao, P. Vad, Badgandi, Mae, Patni, Raf, Subbanna, P. Ka, Shetty, Ra, and Kumar, Hag, “Improved glycaemic control with no weight gain: A 26-week, open label, non-randomised, noninterventional observational study on type 2 diabetes subjects using insulin detemir”, Journal of the Indian Medical Association, vol. 109, pp. 275-278, 2011.[Abstract]

The aim of this study was to evaluate the weight change from baseline while using insulin detemir in subjects with type 2 diabetes mellitus under normal clinical practice conditions. It was a multicentre, open label, non-randomised, non-interventional, observational, safety and efficacy study in subjects using insulin detemir for the treatment of type 2 diabetes mellitus. In this study, the mean body weight decreased marginally by -0.8 kg at the end of week 26 from baseline. Change in mean body weight during the study was not statistically significant (p>0.05). There was a statistically significant (p< 0.05) change in waist circumference (-0.7 cm) from baseline at week 26. Mean fasting plasma glucose reduced significantly (p<0.0001) from 199.1 mg/dl at initiation of insulin detemir to 141.3 mg/dl at week 13 and 115.8 mg/dl at week 26. Mean HbA1c reduced significantly (p<0.0001) from 9.2% at initiation of insulin detemir to 7.8% at week 13 and 7.2% at week 26. Insulin dose changed marginally from the baseline (15.1 units) to week 26 (15.3 units). Majority of the subjects (89%) were on once daily insulin detemir. Before initiating insulin detemir proportion of subjects experiencing at least one episode of hypoglycaemia during the past four weeks was 8.8%(n=884). It was reduced 2.4% (n=241) at week 13 and 1.6% (n=164) at week 26 following initiation of insulin detemir. There were no major nocturnal hypoglycaemic episodes during 26 weeks of insulin detemir therapy. In conclusion, this study indicates that insulin detemir is safe, effective and weight neutral. More »»
2010 Journal Article S. Tripathi, Ramesh, N., Bernito, A., and Neeraj, K. J., “A DWT based Dual Image Watermarking Technique for authenticity and watermark protection”, Signal and Image Processing: an international journal (SIPIJ), vol. 1, pp. 34–45, 2010.[Abstract]

In this paper we propose a DWT based dual watermarking technique wherein both blind and non-blind algorithms are used for the copyright protection of the cover/host image and the watermark respectively. We use the concept of embedding two watermarks into the cover image by actually embedding only one, to authenticate the source image and protect the watermark simultaneously. Here the DWT coefficients of the primary watermark (logo) are modified using another smaller secondary binary image (sign) and the midfrequency coefficients of the cover/host image. Since the watermark has some features of host image embedded in it, the security is increased two-fold and it also protects the watermark from any misuse or copy attack. For this purpose a new pseudorandom generator based on the mathematical constant p has been developed and used successfully in various stages of the algorithm. We have also proposed a new approach of applying pseudo-randomness in selecting the watermark pixel values for embedding in the cover image. In all the existing techniques the randomness is incorporated in selecting the location to embed the watermark. This makes the embedding process more unpredictable. The cover image which is watermarked with the signed-logo is subjected to various attacks like cropping, rotation, JPEG compression, scaling and noising. From the results it has been found that it is very robust and has good invisibility as well. More »»
2009 Journal Article V. Mathuranathan, Satyanarayan, M. N., and Tripathi, S., “DSP Implementation of QPSK and 8-QAM Transmitter for Software Defined Radio”, The IUP Journal of Telecommunications, vol. 1, pp. 54–62, 2009.[Abstract]

Future wireless communication services will require a reconfigurable transmitter capable of switching between several modulation techniques. Reconfigurability could be achieved by defining thetransmitter in software. To adapt to different wireless standard, future radios have to be implemented in software. Software modem radios for 2 and 2.5 Generations have already been implemented (Jeffrey, 2002). In this paper, software defined transmitter capable of switching between Quadrature Phase Shift Keying (QPSK) and 8-Quadrature Amplitude Modulation (QAM) techniques has been implemented on a Digital Signal Processor (DSP) TMS320VC5416 platform. A single coupled standard quadrature recursive oscillator has been used in the design instead of two oscillators required for the two modulation schemes. This saves program memory. The results obtained are in accordance with the simulation and theoretical analysis. More »»
2009 Journal Article S. Tripathi, Pawan, A., and Bansal, A., “Skew Estimation in Document Images Using Wigner-Ville Time-Frequency Functions”, CiiT International Journal of Digital Image Processing, 2009.
2005 Journal Article S. Tripathi, Husami, N., Desai, A. Vamsi, and Satija, A., “New Quantization Based Watermarking Scheme For Digital Images”, International Conference on Systemics, Cybernetics & Informatics (ICSCI-2005), 2005.[Abstract]

Authenticity and integrity of digital media is of primary concern in transmission and reception of multimedia data. We propose a digital image watermarking scheme that depends solely on the secrecy of the security key and not that of the watermarking algorithm. The proposed digital watermarking scheme is based upon Discrete Cosine Transform and uses properties of the transform to achieve the least visible distortion in the watermarked image. The proposed technique involves a unique method for spreading, embedding and extracting the watermark. It allows for five separate levels of security, all of which must be affirmed to. The watermarked images were subjected to image cropping, JPEG lossy compression and other destructive attacks with a minimum level of 65% extraction. The proposed technique also supports implementation using Discrete Wavelet Transforms (DWT). Keywords: Digital Watermarking, quantization, iscrete Cosine Transform, Discrete Wavelet Transform

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2003 Journal Article S. Tripathi and Jain, R. C., “A Modified Image Coder using HVS Characteristics”, 2003.
Publication Type: Book Chapter
Year of Conference Publication Type Title
2016 Book Chapter V. P. Kalyan Kumar, Suja, P., and Tripathi, S., “Emotion Recognition from Facial Expressions for 4D Videos Using Geometric Approach”, in Advances in Signal Processing and Intelligent Recognition Systems: Proceedings of Second International Symposium on Signal Processing and Intelligent Recognition Systems (SIRS-2015) December 16-19, 2015, Trivandrum, India, S. M. Thampi, Bandyopadhyay, S., Krishnan, S., Li, K. - C., Mosin, S., and Ma, M. Cham: Springer International Publishing, 2016, pp. 3–14.[Abstract]

Emotions are important to understand human behavior. Several modalities of emotion recognition are text, speech, facial expression or gesture. Emotion recognition through facial expressions from video play a vital role in human computer interaction where the facial feature movements that convey the emotion expressed need to be recognized quickly. In this work, we propose a novel method for the recognition of six basic emotions in 4D video sequences of BU-4DFE database using geometric based approach. We have selected key facial points out of the 83 feature points provided in the BU-4DFE database. A video expressing emotion has frames containing neutral, onset, apex and offset of that emotion. We have identified the apex frame from a video sequence automatically. The Euclidean distance between the feature points in apex and neutral frame is determined and their difference in corresponding neutral and the apex frame is calculated to form the feature vector. The feature vectors thus formed for all the emotions and subjects are given to Random Forests and Support Vector Machine (SVM) for classification. We have compared the accuracy obtained by the two classifiers. Our proposed method is simple, uses only two frames and yields good accuracy for BU-4DFE database. We have determined optimum number of key facial points that could provide better recognition rate using the computed distance vectors. Our proposed method gives better results compared with literature and can be applied for real time implementation using SVM classifier and kinesics in future. More »»
2016 Book Chapter D. KrishnaSri, Suja, P., and Tripathi, S., “Emotion Recognition from 3D Images with Non-Frontal View Using Geometric Approach”, in Advances in Signal Processing and Intelligent Recognition Systems, Springer, 2016, pp. 63–73.[Abstract]

Over the last decade emotion recognition has gained prominence for its applications in the field of Human Robot Interaction (HRI), intelligent vehicle, patient health monitoring, etc. The challenges in emotion recognition from nonfrontal images, motivates researchers to explore further. In this paper, we have proposed a method based on geometric features, considering 4 yaw angles (0°, +15°, +30°, +45°) from BU-3DFE database. The novelty in our proposed work lies in identifying the most appropriate set of feature points and formation of feature vector using two different approaches. Neural network is used for classification. Among the 6 basic emotions four emotions i.e., anger, happy, sad and surprise are considered. The results are encouraging. The proposed method may be implemented for combination of pitch and yaw angles in future. © Springer International Publishing Switzerland 2016.

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2016 Book Chapter P. Suja, Thomas, S. Mariam, Tripathi, S., and Madan, V. K., “Emotion Recognition from Images Under Varying Illumination Conditions”, in Soft Computing Applications, Springer, 2016, pp. 913–921.[Abstract]

Facial expressions are one of the most powerful and immediate means for human beings to communicate their emotions. Recognizing human emotion has varied range of applications in humanoid robots, animation industry, psychology, forensic analysis, medical aid, automotive industry, etc. This work focuses on emotion recognition under various illumination conditions using images from CMU-MultiPIE database. The database is provided with five basic expressions like neutral, happiness, anger, disgust and surprise with varying pose and illuminations. The experiment has been conducted on images with varying illuminations initially without pre-processing and also by applying a proposed ratio-based pre-processing method followed by feature extraction and classification. Dual—Tree-Complex Wavelet Transform (DT-CWT) was applied for the formation of feature vectors along with K-Nearest Neighbour (KNN) as the classifier. The result shows that pre-processed images give better results than original images. It is thus concluded that varying illumination has effect on emotion recognition and the pre-processing algorithm demonstrates improvement in accuracy of recognition. Future work may include a broader perspective of using body language and speech data for emotion recognition. © Springer International Publishing Switzerland 2016.

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2014 Book Chapter I. Mamatha, Tripathi, S., Sudarshan, T. S. B., and Bhattar, N., “Systolic Array Implementation of DFT with Reduced Multipliers Using Triple Matrix Product”, in Advances in Signal Processing and Intelligent Recognition Systems, Springer, 2014, pp. 311–322.[Abstract]

A generic 2D systolic array for N point Discrete Fourier Transform using triple matrix product algorithm is proposed. The array can be used for a non power of two sized N point DFT where N=N1N2&nbsp;is a composite number. It uses an array of size N2×(N1+1) which requires(2N+4N2) multipliers. For a DFT of size 4N2&nbsp;(i.e multiple of four), an optimized design which requires 4N2number of multipliers is proposed. It is observed that the proposed optimized structure reduces the number of multipliers by 66.6% as compared to the generic array structure while maintaining the same time complexity. Two examples are illustrated, one with non power of two size DFT and another with a DFT of size 4N2. Both the generic and optimized structures use the triple matrix product representation of DFT. The two structures are synthesized using Xilinx ISE 11.1 using the target device as xc5vtx240t-2ff1759 Virtex-5 FPGA. The proposed structure produces unscrambled stream of DFT sequence at output avoiding a necessity of reordering buffer. The array can be used for matrix -matrix multiplication and to compute the diagonal elements of a triple-matrix multiplication.

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2014 Book Chapter P. Suja, Tripathi, S., and Deepthy, J., “Emotion Recognition from Facial Expressions Using Frequency Domain Techniques”, in Advances in Signal Processing and Intelligent Recognition Systems, Springer, 2014, pp. 299–310.[Abstract]

An emotion recognition system from facial expression is used for recognizing expressions from the facial images and classifying them into one of the six basic emotions. Feature extraction and classification are the two main steps in an emotion recognition system. In this paper, two approaches viz., cropped face and whole face methods for feature extraction are implemented separately on the images taken from Cohn-Kanade (CK) and JAFFE database. Transform techniques such as Dual – Tree Complex Wavelet Transform (DT-CWT) and Gabor Wavelet Transform are considered for the formation of feature vectors along with Neural Network (NN) and K-Nearest Neighbor (KNN) as the Classifiers. These methods are combined in different possible combinations with the two aforesaid approaches and the databases to explore their efficiency. The overall average accuracy is 93% and 80% for NN and KNN respectively. The results are compared with those existing in literature and prove to be more efficient. The results suggest that cropped face approach gives better results compared to whole face approach. DT-CWT outperforms Gabor wavelet technique for both classifiers.

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2014 Book Chapter R. Karthikeyan, Pasam, S., Sudheer, S., Teja, V., and Tripathi, S., “Fuzzy Fractional Order PID Based Parallel Cascade Control System”, in Recent Advances in Intelligent Informatics, Springer, 2014, pp. 293–302.[Abstract]

Parallel cascade controllers are used in process and control industries to improve the dynamic performance of a control system in the presence of disturbances. In the present work, fuzzy set point weighted Fractional Order Proportional Integral Derivative (FOPID) controller is designed for the primary loop of the parallel cascade control system. The secondary controller is designed using the internal model control (IMC) method. Also, a smith predictor based dead time compensator is designed to compensate large time delay in the process. Several case studies are considered to show the advantage of the proposed method when compared to other recently reported methods. The proposed method provides robust control performance which significantly improves the closed loop response with less settling time when compared to conventional PID controller based parallel cascade control system.

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2014 Book Chapter R. Karthikeyan, Chava, B., Koneru, K., Godavarthi, S. Sundar Var, Tripathi, S., and Murthy, K. V. V., “Enhanced MRAC Based Parallel Cascade Control Strategy for Unstable Process with Application to a Continuous Bioreactor”, in Recent Advances in Intelligent Informatics, Springer, 2014, pp. 283–291.[Abstract]

In this paper, Enhanced Model Reference Adaptive Control (E-MRAC) based Parallel Cascade Control strategy (PCC) is proposed for the control of unstable continuous bioreactor. This control system consists of secondary and primary loop. The secondary loop comprises of PID controller, which is designed based on the direct synthesis method. In order to achieve stable responses for unstable processes like continuous bioreactor, non linear control strategy in the primary loop would gain edge over linear control. Hence, the Enhanced MRAC (includes smith predictor) is introduced in the primary loop. The presence of Smith predictor has minimized the discrepancies due to dead times. This seems to be an added advantage over existing ones. From the simulation studies it is observed that Enhanced MRAC based PCC has shown better tracking performance when compared to the PID based PCC control strategy.

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2012 Book Chapter S. Kochuvila, Tripathi, S., and Sudarshan, T. S. B., “Control of a Compass Gait Biped Robot Based on Partial Feedback Linearization”, in Advances in Autonomous Robotics, Springer, 2012, pp. 117–127.[Abstract]

<p>This paper deals with the control of a passivity based walking biped robot on a level surface using partial feedback linearization technique. A stable reference trajectory is generated from the Lagrangian dynamics of the biped robot and it is shown that the under actuated robot can follow the stable limit cycle trajectory using a control law based on partial feedback linearization approach. A comparison of the above approach with the conventional feedback linearization technique in terms of the Mean Square Error (MSE) is also carried out. Simulation of the forward walking is done on a compass like model of the biped robot.</p>

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2006 Book Chapter S. Tripathi, Vikas, R., and Jain, R. C., “An efficient real time low bit rate video codec”, in Computer Vision–ACCV 2006, Springer, 2006, pp. 500–508.[Abstract]

The implementation of a codec for real time applications such as video-conferencing at low bit rates is discussed. The discrete cosine transform has been used for compression, both in two spatial axes as well as in the time axis of the video sequence. A new method of frame by frame processing is proposed which reduces the real time delay associated with processing and transmission of successive video frames, with minimal memory and processing overhead. This implementation is inherently simple and also provides improved performance compared to other popular codecs More »»
Publication Type: Conference Paper
Year of Conference Publication Type Title
2016 Conference Paper V. Chandran, I, M., and Tripathi, S., “NEDA based hybrid architecture for DCT-HWT”, in 2nd International Conference on VLSI System Architecture & Technology (VLSI-SATA 2016), Jan 10-12, 2016, ASE, Bangalore, 2016.
2016 Conference Paper M. I, Tripathi, S., and TSB, S., “Pipelined architecture for filter bank based 1-D DWT”, in 2016 3rd International Conference on Signal Processing and Integrated Networks (SPIN), 2016.[Abstract]

A Convolution based parallel and pipelined architecture using MAC Loop Based Filter (MLBF) is proposed in this work. The proposed modification to the MLBF structure produces one output sample for every clock cycle as compared to the MLBF structure which produces two outputs for every four clock cycles. This results in a speed up of 2× which is significant for processing real time signals of long length. Compared to the existing MLBF based 1-D DWT architecture, proposed design uses additional 8 multipliers and 8 adders. The proposed structure is independent of the input size and filter length and performs better than other architectures with same or less area utilization. Generality, scalability, high efficiency of hardware utilization are the other merits of the proposed structure. The architecture is synthesized on Virtex 6 xc6vcx240t-2ff784 FPGA board and can operate at a maximum frequency of 633.43 MHz. The frequency of operation is twice as that of the existing approach. More »»
2016 Conference Paper , P., S., and Tripathi, S., “Real-time emotion recognition from facial images using Raspberry Pi II”, in 2016 3rd International Conference on Signal Processing and Integrated Networks (SPIN), 2016.[Abstract]

In present day technology human-machine interaction is growing in demand and machine needs to understand human gestures and emotions. If a machine can identify human emotions, it can understand human behavior better, thus improving the task efficiency. Emotions can understand by text, vocal, verbal and facial expressions. Facial expressions play big role in judging emotions of a person. It is found that limited work is done in field of real time emotion recognition using facial images. In this paper, we propose a method for real time emotion recognition from facial image. In the proposed method we use three steps face detection using Haar cascade, features extraction using Active shape Model(ASM), (26 facial points extracted) and Adaboost classifier for classification of five emotions anger, disgust, happiness, neutral and surprise. The novelty of our proposed method lies in the implementation of emotion recognition at real time on Raspberry Pi II and an average accuracy of 94% is achieved at real time. The Raspberry Pi II when mounted on a mobile robot can recognize emotions dynamically in real time under social/service environments where emotion recognition plays a major role. More »»
2015 Conference Paper I. Mamatha, Raj, J. N., Tripathi, S., and T.S.B. Sudarshan, “Systolic architecture implementation of 1D DFT and 1D DCT”, in 2015 IEEE International Conference on Signal Processing, Informatics, Communication and Energy Systems, SPICES 2015, 2015.[Abstract]

Discrete Fourier Transform is widely used in signal processing for spectral analysis, filtering, image enhancement, OFDM etc. Cyclic convolution based approach is one of the techniques used for computing DFT. Using this approach an N point DFT can be computed using four pairs of [(M-1)/2]-point cyclic convolution where M is an odd number and N=4M. This work proposes an architecture for convolution based DFT and its FPGA implementation. Proposed architecture comprises of a pre-processing element, systolic array and a post processing stage. Processing element of systolic array uses a tag bit to decide on the type of operation (addition/subtraction) on the input signals. Proposed architecture is simulated for 28 point DFT using ModelSim 6.5 and synthesized using Xilinx ISE10.1 using Vertex 5 xc5vfx100t-3ff1738 FPGA as the target device and can operate at a maximum frequency of 224.9MHz. The performance analysis is carried out in terms of hardware utilization and computation time and compared with existing similar architectures. Further, as the convolution based DCT has two systolic arrays similar to that of DFT, a unified architecture is proposed for 1D DFT/1D DCT. © 2015 IEEE.

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2015 Conference Paper M. Sa Sinith, Tripathi, S., and Murthy, K. V. Vc, “Real-time swara recognition system in Indian Music using TMS320C6713”, in 2015 International Conference on Advances in Computing, Communications and Informatics, ICACCI 2015, 2015, pp. 1835-1838.[Abstract]

Swara is the basic component of Indian Music. Swara recognition is the starting point of music pattern classification in Indian classical music. The recognition of swara in real-time is often required for judging the quality of tone of a vocalist or an instrumentalist. In this age of reality shows of music, a stand alone electronic system for swara recognition is very relevant, where the system would precisely judge the contestant in terms of swara perfection. In this context a swara recognition system is designed and implemented on a Texas Instrumemts Digital Signal Processor TMS320C6713. In this system the fundamental frequency is tracked using FFT algorithm and also using a newly developed algorithm which works efficiently in Digital Signal Processors. The frequency so obtained is wrapped to a single octave. The fundamental frequency is then mapped to twelve distinct values corresponding to twelve semi-notes and displayed in the LED display of the DSP Processor. The efficiency of the system is tested in terms of memory usage and speed. © 2015 IEEE.

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2015 Conference Paper S. V. B. Bala Sai, Mamatha, I., Tripathi, S., and Sudarshan, T. S. B., “Modified MLBF based architecture for 1-D DWT”, in 2015 IEEE International Conference on Computational Intelligence and Computing Research (ICCIC), Madurai,India, 2015.[Abstract]

This work proposes an architecture for fast computation of 1-D Discrete Wavelet Transform (DWT). Existing MAC loop based filter (MLBF) is modified and a poly-phase structure for 1-D DWT is proposed. Proposed structure improves the throughput by 1.5x while using almost double the hardware as that of the existing structure. 1-D DWT using existing MLBF structure and proposed structure are simulated using ModelSim and synthesized using Xilinx ISE 14.2 on Virtex-6 XC6VCX240T-2FF784 target device. It is observed that the proposed architecture can be operated at a maximum frequency of 163.59MHz. The simulation results obtained from ModelSim is compared with MatLab R2010a output and found to be accurate. More »»
2015 Conference Paper S. P., D., K., and Tripathi, S., “Pose invariant method for emotion recognition from 3D images”, in 2015 Annual IEEE India Conference (INDICON), 2015.[Abstract]

Information about the emotional state of a person can be inferred from facial expressions. Emotion recognition has become an active research area in recent years in various fields such as Human Robot Interaction (HRI), medicine, intelligent vehicle, etc., The challenges in emotion recognition from images with pose variations, motivates researchers to explore further. In this paper, we have proposed a method based on geometric features, considering images of 7 yaw angles (-45°,-30°,-15°,0°,+15°,+30°,+45°) from BU3DFE database. Most of the work that has been reported considered only positive yaw angles. In this work, we have included both positive and negative yaw angles. In the proposed method, feature extraction is carried out by concatenating distance and angle vectors between the feature points, and classification is performed using neural network. The results obtained for images with pose variations are encouraging and comparable with literature where work has been performed on pitch and yaw angles. Using our proposed method non-frontal views achieve similar accuracy when compared to frontal view thus making it pose invariant. The proposed method may be implemented for pitch and yaw angles in future. More »»
2015 Conference Paper S. Lalitha, Chaitanya, K. K., Teja, G. V. N., Varma, K. V., and Tripathi, S., “Time-frequency and phase derived features for emotion classification”, in 2015 Annual IEEE India Conference (INDICON), 2015.[Abstract]

Emotion recognition and synthesis plays a crucial role in Human-computer interface. In this paper, we propose a multi style emotion recognition algorithm using time frequency (pH) and phase delay of a speech signal. Most of the work done so far on emotion recognition using spectral features mainly focuses on magnitude of the signal. Phase delay has been incorporated in this work yielding better results in detecting low arousal emotions. Here, we include phase components along with the time frequency feature to form the feature vector thus increasing the efficiency by about 12%. Berlin database has been used for training and testing yielding recognition of 80.95% for seven emotions. SVM classifier is used in this work. More »»
2013 Conference Paper I. Mamatha, J Raj, N., Tripathi, S., and Sudarshan, T. S. B., “Reduced Complexity Architecture for Convolution Based Discrete Cosine Transform”, in Electronic System Design (ISED), 2013 International Symposium on, 2013.[Abstract]

Discrete Cosine Transform is a popular transform used in signal/image processing applications. Reduction in complexity of hardware architecture for the computation of DCT using the convolution based algorithm is proposed. An N point DCT can be computed through 2 pair of [(M-1)/2] point cyclic convolutions where M is an odd number such that N=2M. The proposed architecture uses only a pair of systolic array where inputs are pipelined against the one in literature where 2 pairs of systolic arrays are used. One of the systolic arrays uses processing element with tag bit and the other one does not need a tag bit. The architecture uses 50% less number of processing elements with just an additional increase in computation time by one unit. The architecture is divided into three stages as preprocessor stage, compute stage where a systolic array computes the cyclic convolution and a post processing stage to process the output of the systolic array to get the actual DCT output. It is observed that the proposed architecture has a reduction of about 42%adders and 64% multipliers as compared to the one in literature. Further, the architecture is simulated in ModelSim 6.5 and synthesized using Xilinx ISE10.1using Vertex 5 FPGA as the target device. The simulation results are matched favourably with that of the output obtained by MATLAB R2010a with MSE of1.3861x10-4.

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2013 Conference Paper S. Tripathi, D.G. Kurup, .Navya, K., and Amrutha, N. U., “Time Series Analysis of Solar and Stellar Data using the S-Transform”, in ELSEVIER Proceedings of International Conferences on Advances in Signal Processing and Communication (SPC-2013), Lucknow, India, 2013.
2013 Conference Paper S. Tripathi, .N.Keerthana, D., and .Suja, P., “Emotion Recognition using DWT, KL Transform and Neural Network”, in International Conference on advances in Signal Processing and Communications (SPC2013), 2013.
2012 Conference Paper R. Karthikeyan, Yadav, R. Kumar, Tripathi, S., and Kumar, H. G., “Analyzing large dynamic set-point change tracking of MRAC by exploiting fuzzy logic based automatic gain tuning”, in Control and System Graduate Research Colloquium (ICSGRC), 2012 IEEE, 2012, pp. 76-81.[Abstract]

A Model reference adaptive control (MRAC) belongs to the class of adaptive servo system in which the desired performance is expressed with the help of a reference model. MRAC aims to create a closed loop controller with parameters that can change the response of the system to mimic a desired response. However, analysis unravels that there is a tolerance band for the set point change which defines the effectiveness of a particular adaptive gain (γ). Any changes in the set point which is beyond this band calls for a γ-readjustment. We propose a method which aims to overcome this pitfall in conventional MRAC by fusing fuzzy logic to dynamically vary γ. In essence, a fixed γ which fails to stabilize the system response in the advent of a large change in the average value of the set point shall be empowered with fuzzy logic to do the needful. Also, this concept never requires human interference for gain adjustment. A second order Linear Time Invariant system has been considered for all illustration. The results show considerable improvement in performance over the existing conventional MRAC system.

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2011 Conference Paper S. Ravishankar, Reddy, C. Nagadastag, Tripathi, S., and Murthy, K. V. V., “Image super resolution using sparse image and singular values as priors”, in Computer Analysis of Images and Patterns, 2011, vol. 6855 LNCS, pp. 380-388.[Abstract]

In this paper single image superresolution problem using sparse data representation is described. Image super-resolution is ill -posed inverse problem. Several methods have been proposed in the literature starting from simple interpolation techniques to learning based approach and under various regularization frame work. Recently many researchers have shown interest to super-resolve the image using sparse image representation. We slightly modified the procedure described by a similar work proposed recently. The modification suggested in the proposed approach is the method of dictionary training, feature extraction from the trained data base images and regularization. We have used singular values as prior for regularizing the ill-posed nature of the single image superresolution problem. Method of Optimal Directions algorithm (MOD) has been used in the proposed algorithm for obtaining high resolution and low resolution dictionaries from training image patches. Using the two dictionaries the given low resolution input image is super-resolved. The results of the proposed algorithm showed improvements in visual, PSNR, RMSE and SSIM metrics over other similar methods. More »»
2010 Conference Paper S. Tripathi, Mathur, R., and Arya, J., “Unified 3GPP and 3GPP2 turbo encoder FPGA implementation using run-time partial reconfiguration”, in Wireless Telecommunications Symposium (WTS), 2010, 2010.[Abstract]

One key objective of Software Defined radio is to implement multiple standards on common hardware. This can be achieved by partial reconfiguration of Field Programmable Gate Array (FPGA) in which some part of the FPGA remains active while other gets reconfigured. This paper proposes partially reconfigurable design of unified turbo encoder of two 3G standards-3GPP and 3GPP2 on FPGA Xilinx Virtex- IV. The design shows substantial improvement in hardware implementation of the interleavers over the previous designs. In order to achieve the best possible results with partial reconfiguration, maximum common functionality from both the turbo encoders has been identified and a unified architecture has been proposed. Novel ways have been devised to perform the computationally intensive operations of the 3GPP interleaver with minimal hardware requirement and least possible number of clock cycles. More »»
2009 Conference Paper S. Tripathi, R, S. Krishnan, and M, V., “Intelligent Multiple Watermarking Technique to Prevent Copy Attack”, in National Conference on Virtual & Intelligent Instrumentation (NCVII09), 2009.
2006 Conference Paper S. Tripathi, Jain, R. C., and Gayatri, V., “Novel DCT and DWT based watermarking techniques for digital images”, in Pattern Recognition, 2006. ICPR 2006. 18th International Conference on, 2006.[Abstract]

Two digital image watermarking techniques that have higher level of security compared to most of the existing algorithms have been proposed. The proposed digital watermarking scheme uses the properties of discrete cosine transform (DCT) and discrete wavelet transforms (DWT) to achieve almost zero visible distortion in the watermarked images. These techniques use a unique method for spreading, embedding and extracting the watermark. Embedding using a linear relation between the transform coefficients of the watermark and a security matrix has been proposed with satisfactory results. It has been shown that instead of adding the watermark to the source image, as is normally done, multiplying the watermark with the transformed source could be a preferred technique, as it would retain the original bit rate to a large extent. The watermarked images were tested subject to image cropping. More »»
Publication Type: Conference Proceedings
Year of Conference Publication Type Title
2016 Conference Proceedings S. Vekkot and Tripathi, S., “Significance of Glottal Closure Instants detection algorithms in Vocal Emotion Conversion”, 7th International Workshop on Soft Computing Applications (SOFA2016), 24-26 Aug, 2016, Arad, Romania, Proceedings published by Springer (Scopus-Indexed). 2016.
2007 Conference Proceedings S. Tripathi, R, S. Krishnan, and M, V., “Quantization Based Blind Watermarking Algorithm Using DWT”, International Conference on Image Processing, Computer Vision and Pattern Recognition. CSREA Press, Las Vegas, pp. 123-129, 2007.
2006 Conference Proceedings S. Tripathi, Mahaldar, S., V, A., and Jain, R. C., “Joint Source Channel Coding for Wireless Medium Using SPIHT- RS Codec”, IEEE International Symposium On Ad Hoc and Ubiquitous Computing. IEEE, Surathkal, pp. 175-178, 2006.[Abstract]

Joint source channel coding (JSCC) technique is used to design an image transmission system using Reed Solomon (RS) channel coder by providing a feedback mechanism. The proposed codec offers wide range of choices to the user to achieve compression and the desired data rate corresponding to an image quality. Performance of the set partitioning in hierarchical trees (SPIHT) and RS coder for different compression rates and BER probabilities is presented. The proposed scheme led to an imperceptible decrease in the PSNR values but a considerable decrease in the bpp values as compared to the corresponding figures obtained from the existing SPIHT-RCPC scheme. This technique is more suited to channels that are prone to burst errors like wireless channel. More »»
2006 Conference Proceedings S. Tripathi, Mahaldar, S., V, A., and Jain, R. C., “Efficient Transmission of Images Over Wireless Medium Using SPIHT- RS Codec”, IEEE International Symposium On Ad Hoc and Ubiquitous Computing. pp. 175-178, 2006.
2004 Conference Proceedings S. Tripathi and Vikas, R., “Real Time Video Compression using a Modified Algorithm For Mobile Applications”, National Symposium on GSM and CDMA Technologies for Mobiles. Jaipur, 2004.
2003 Conference Proceedings S. Tripathi, Jain, R. C., and Peres, G., “Low Bit Rate Image Coding Using Human Visual System Model”, International Conference on Advanced Computing and Communications. Coimbatore, pp. 142 – 150, 2003.
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