Pavel Bhowmik

Realization of an Adaptive Memetic Algorithm Using Differential Evolution and Q-Learning: A Case Study in Multirobot Path Planning

Memetic algorithms (MAs) are population-based meta-heuristic search algorithms that combine the composite benefits of natural and cultural evolutions. An adaptive MA (AMA) incorporates an adaptive selection of memes (units of cultural transmission) from a meme pool to improve the cultural characteristics of the individual member of a population-based search algorithm. This paper presents a novel approach to design an AMA by utilizing the composite benefits of differential evolution (DE) for global search and Q-learning for local refinement. Four variants of DE, including the currently best self-adaptive DE algorithm, have been used here to study the relative performance of the proposed AMA with respect to runtime, cost function evaluation, and accuracy (offset in cost function from the theoretical optimum after termination of the algorithm). Computer simulations performed on a well-known set of 25 benchmark functions reveal that incorporation of Q-learning in one popular and one outstanding variants of DE makes the corresponding algorithm more efficient in both runtime and accuracy. The performance of the proposed AMA has been studied on a real-time multirobot path-planning problem. Experimental results obtained for both simulation and real frameworks indicate that the proposed algorithm-based path-planning scheme outperforms the real-coded genetic algorithm, particle swarm optimization, and DE, particularly its currently best version with respect two standard metrics defined in the literature.

A new differential evolution with improved mutation strategy

The paper employs Lagranges mean value theorem of differential Calculus to design a new strategy for the selection of parameter vectors in the Differential Evolution (DE) algorithm. Classical differential evolution selects parameter vectors randomly to obtain the donor vectors. These donor vectors thus cannot be directly used as trial solution to the optimization problem. The recombination step indeed is very useful to generate potential trial solutions. The proposed algorithm eliminates the recombination step as the trial solutions can be directly generated by the extended mutation step only. Performance analysis of the proposed algorithm with respect to standard benchmark functions reveals that both in expected convergence time and accuracy in solutions, the proposed algorithm outperforms classical DE/rand/1. Besides extension in mutation strategy, an adaptive selection strategy in the scaling factor F also improves the performance of the proposed algorithm. In addition, the proposed algorithm outperforms classical DE in noisy optimization problem. Further, the number of function evaluation with scaled up dimensions of the optimization problem adds insignificantly small complexity in comparison to that in classical differential evolution to meet up a prescribed level of accuracy in solution quality.

A support vector machine classifier of emotion from voice and facial expression data

The paper provides a novel approach to emotion recognition from facial expression and voice of subjects. The subjects are asked to manifest their emotional exposure in both facial expression and voice, while uttering a given sentence. Facial features including mouth-opening, eye-opening, eyebrow-constriction, and voice features including, first three formants: F1, F2, and F3, and respective powers at those formants, and pitch are extracted for 7 different emotional expressions of each subject. A linear Support Vector Machine classifier is used to classify the extracted feature vectors into different emotion classes. Sensitivity of the classifier to Gaussian noise is studied, and experimental results confirm that the recognition accuracy of emotion up to a level of 95% is maintained, even when the mean and standard deviation of noise are as high as 5% and 20% respectively over the individual features. A further analysis to identify the importance of individual features reveals that mouthopening and eye-opening are primary features, in absence of which classification accuracy falls off by a large margin of more than 22%.

DE-TDQL: An adaptive memetic algorithm

Memetic algorithms are population-based meta-heuristic search algorithms that combine the composite benefits of natural and cultural evolution. In this paper a synergism of the classical Differential Evolution algorithm and Q-learning is used to construct the memetic algorithm. Computer simulation with standard benchmark functions reveals that the proposed memetic algorithm outperforms three distinct Differential Evolution algorithms.

Uncertainty management in type-2 fuzzy face-space for emotion recognition

Manifestation of a given emotion on facial expression is not always unique, as the facial attributes in different instances of similar emotional experiences may vary widely. When a number of facial attributes are used to recognize the emotion of a subject, the variation of individual attributes together makes the problem more complicated. This variation is the main source of uncertainty in the emotion recognition problem, which has been addressed here in two steps using type-2 fuzzy sets. First a type-2 fuzzy face-space is constructed with the background knowledge of facial features of different subjects for different emotions. Second, the emotion of the unknown subject is determined based on the consensus of the measured facial features with the fuzzy face-space. The face-space comprises both primary and secondary membership distributions. The primary membership distributions here have been constructed based on the highest frequency of occurrence of the individual attributes. Naturally, the membership values of an attribute at all except the point of highest frequency of occurrence suffer from inaccuracy, which has been taken care of by secondary memberships. An algorithm for the evaluation of the secondary membership distribution from its type-2 primary counterpart has been proposed. The uncertainty management policy adopted using general type-2 fuzzy set has a classification accuracy of 96.67% in comparison to 88.67% obtained by interval type-2 counterpart only.

Emotion clustering from stimulated electroencephalographic signals using a Duffing oscillator

The paper proposes an alternative approach to emotion recognition from stimulated EEG signals using Duffing oscillator. Reported works on emotion clustering generally employ the principles of supervised learning. Unfortunately, because of noisy and limited feature set, the classification problem often suffers from high inaccuracy. This has been overcome in this paper by submitting the EEG signals directly to a Duffing oscillator and the phase portraits constructed from its time-response demonstrate structural similarity to similar emotion excitatory stimuli. The accuracy in clustering was experimentally validated even with injection of Gaussian noise over the EEG signal up to a signal-to-noise ratio of 25 dB. The results of clustering in presence of low signal-to-noise ratio confirm the robustness of the proposed scheme.

Correlation between stimulated emotion extracted from EEG and its manifestation on facial expression

Determining correlation between aroused emotion and its manifestation on facial expression, voice, gesture and posture have interesting applications in psychotherapy. A set of audiovisual stimulus, selected by a group of experts, is used to excite emotion of the subjects. EEG and facial expression of the subjects excited by the selected audio-visual stimulus are collected, and the nonlinear-correlation from EEG to facial expression, and vice-versa is obtained by employing feed-forward neural network trained with back-propagation algorithm. Experiments undertaken reveals that the trained network can reproduce the correlated EEG-facial expression trained instances with 100 % accuracy, and is also able to predict facial expression (EEG) from unknown EEG (facial expression) of the same subject with an accuracy of around 95.2%.

A Computational Intelligence Approach to Emotion Recognition from the Lip-Contour of a Subject

This chapter provides an alternative approach to emotion recognition from the outer lip-contour of the subjects. Subjects exhibit their emotions through their facial expressions, and the lip region is segmented from their facial images. A lip-contour model has been developed to represent the boundary of the lip, and the parameters of the model are adapted using differential evolution algorithm to match it with the boundary contour of the lip. A support vector machine (SVM) classifier is then employed to classify the emotion of the subject from the parameter set of the subjects’ lip-contour. The experiment was performed on 50 subjects in an age group from 18 to 25, and the average case accuracy in emotion classification is found to be 86 %.