A wide variety of media can be used in learning, including distance learning, such as print, lectures, conference sections, tutors, pictures, video, sound, and computers. Any one instance of distance learning will make choices among these media, perhaps using several.

Multimedia in Learning

A dynamical model is presented as a framework for muscle activation, fatigue, and recovery. By describing the effects of muscle fatigue and recovery in terms of two phenomenological parameters (F, R), we develop a set of dynamical equations to describe the behavior of muscles as a group of motor units activated by voluntary effort. This model provides a macroscopic view for understanding biophysical mechanisms of voluntary drive, fatigue effect, and recovery in stimulating, limiting, and modulating the force output from muscles. The model is investigated under the condition in which brain effort is assumed to be constant. Experimental validation of the model is performed by fitting force data measured from healthy human subjects during a 3-min sustained maximal voluntary handgrip contraction. The experimental results confirm a theoretical inference from the model regarding the possibility of maximal muscle force production, and suggest that only 97% of the true maximal force can be reached under maximal voluntary effort, assuming that all motor units can be recruited voluntarily. The effects of different motor unit types, time-dependent brain effort, sources of artifacts, and other factors that could affect the model are discussed. The applications of the model are also discussed.

a Dynamical Model of Muscle Activation, Fatigue and Recovery

This paper presents investigations into the development of an assistive device for elderly mobility. An exoskeleton is designed as an assistive device, to enhance the lower extremity and provide supporting torque to augment the torque of hip and knee during the walking cycle. A humanoid and actuated exoskeleton frame are designed in solid works and then imported to Visual Nastran 4D virtual environment. Fuzzy PID Control algorithm uses to control the actuated exoskeleton. Simulated walking tasks are performed with a humanoid wearing the exoskeleton. It is assumed that the humanoid representing an elderly person, is able to provide 60% of the whole torque required to complete the gait cycle, and the assistive device providing 40% of the overall torque.

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Fuzzy PID control of lower limb exoskeleton for elderly mobility

Despite being a good method against uncertainties, the high complexity of the operations in type-2 fuzzy system makes it slow. So, it should be reduced to use type-2, especially in real-time problems. In this study, a method based on image digitization has been proposed for type-reduction and defuzzification steps, which are forming the actual computational complexity in type-2 fuzzy systems. Instead of solutions using iterative and complex methods, the problem is converted into image processing problem by digitizing the fired outputs. The deduction methods such as the center of gravity are computed easily on digitized images. Example scenarios show that the work done is superior to KM algorithm in terms of both precision and computational complexity. In addition, different simulations were conducted to demonstrate the superiority of the study over real problems, and the study was tested for a complex human model motion control problem.

Image Processing-Based Center Calculation Method for General and Interval Type-2 Fuzzy Systems

Firefly Algorithm (FA) is a powerful swarm intelligence algorithm inspired by the flash phenomenon of the fireflies. However, it has weaknesses on optimizing high-dimensional problems. This paper presents an improved FA named Adaptive Firefly Algorithm (AFA). In the new algorithm, three strategies are proposed to improve its adaptability and overcome its weaknesses. The algorithm is tested on a set of benchmark functions with different dimensions. Canonical FA and two other well-known heuristic algorithms are also employed for comparison. Experiment and statistical results show that the AFA algorithm offers significant better performance than original FA algorithm. Especially on high-dimensional problems, it is superior to all other compared algorithms.

An Improved Firefly Algorithm with Adaptive Strategies

Design and control of exoskeleton for elderly mobility

Firefly algorithm (FA) is a swarm intelligence based algorithm for global optimization and has widely been used in solving problems in many areas. The FA is good at exploring the search space and locating the global optimum, but it always gets trapped at local optimum especially in case of high dimensional problems. In order to overcome such drawbacks of FA, this paper proposes a modified variant of FA, referred to as spread enhancement strategy for firefly algorithm (SE-FA), by devising a nonlinear adaptive spread mechanism for the control parameters of the algorithm. The performance of the proposed algorithm is compared with the original FA and one variant of FA on six benchmark functions. Experimental and statistical results of the approach show better solutions in terms of reliability and convergence speed than the original FA especially in the case of high-dimensional problems. The algorithms are further tested with control of dynamic systems. The systems considered comprise assistive exoskeletons mechanism for upper and lower extremities. The performance results are evaluated in comparison to the original firefly and invasive weed algorithms. It is demonstrated that the proposed approaches are superior over the individual algorithms in terms of efficiency, convergence speed and quality of the optimal solution achieved.

/pdf/spread-enhancement-for-firefly-algorithm-with-application-to-3f1azyno29.pdf

Spread enhancement for firefly algorithm with application to control mechanism of exoskeleton system

One of the most common issues to human is fatigue. A technology known as exoskeleton has been identified as one of the solutions to address this issue. However, there are two issues that need to be solved. One of them is the control approach. Hence, the main aim of this work, is to investigate the control design for upper-limb exoskeleton. An extended based fuzzy control is proposed to observe the effectiveness of the exoskeleton in dealing with human with different strength. Three conditions of human strength were applied. PID was used for a comparison purpose. It is shown that with the proposed control approach, the exoskeleton can assist human to achieve the desired trajectory accurately with a minimal amount of torque required .

/pdf/control-design-of-a-de-weighting-upper-limb-exoskeleton-2tiy2dsa9d.pdf

Control design of a de-weighting upper-limb exoskeleton: extended-based fuzzy

One of the most common problems in humans is a muscle fatigue. Exoskeletons are known as one of the solution to deal with human muscle fatigue. However, several issues related to the development of exoskeletons for such a case have been identified. One of these is the control mechanism. Thus, the objective of this paper is to investigate development of a control strategy for the upper-limb exoskeleton. In this paper, a new control mechanism for an upper-limb exoskeleton is proposed. A fuzzy-based PD controller and PID are used in the proposed control mechanism, and a comparative assessment of the performance of both controllers is made. The results show that the control mechanism with fuzzy-based PD controller performs better than the PID controller in terms of trajectory tracking accuracy and control torque analysis.

/pdf/control-design-of-a-de-weighting-upper-limb-exoskeleton-3glli07udu.pdf

Control Design of a De-Weighting Upper Limb Exoskeleton

Mesh simplification has become an interesting research area over the past few decades. Some researchers have introduced various new methods while others have made some modifications or improvements to the existing method. However, the modified model tended to lose some of its original shape. Hence, to solve these arising problems, a new mesh simplification algorithm is introduced in this paper. Mesh simplification can be divided into two groups; mesh decimation and mesh refinement. However, in this work, mesh decimation is chosen and a rational equation is used as a cost to select elements as a candidate to be removed. The proposed algorithm also used triangular mesh as the element. The proposed algorithm was tested onto three types of data: the parametric equations, 3D data from standard database and 3D data from 3D scanner. The results clearly demonstrated that the proposed algorithm can preserve the important features of the parametric equations and 3D human shape while the boundary of the models is protected from being removed. In addition, the proposed algorithm also succeeded in simplifying the models without distorting the whole shape of the models even if the sliver triangle test is not applied on it.

Siti Khadijah Ali

Papers

Design and control of exoskeleton for elderly mobility

Spread enhancement for firefly algorithm with application to control mechanism of exoskeleton system

Control design of a de-weighting upper-limb exoskeleton: extended-based fuzzy

Control Design of a De-Weighting Upper Limb Exoskeleton

Rational Equation for Simplifying Complex Surfaces