There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

An overview of the self-organizing map algorithm, on which the papers in this issue are based, is presented in this article.

The Self-Organizing Map

With construction of new large-scale water storage projects on the wane in the U.S. and other developed countries, attention must focus on improving the operational effectiveness and efficiency of existing reservoir systems for maximizing the beneficial uses of these projects. Optimal coordination of the many facets of reservoir systems requires the assistance of computer modeling tools to provide information for rational management and operational decisions. The purpose of this review is to assess the state-of-the-art in optimization of reservoir system management and operations and consider future directions for additional research and application. Optimization methods designed to prevail over the high-dimensional, dynamic, nonlinear, and stochastic characteristics of reservoir systems are scrutinized, as well as extensions into multiobjective optimization. Application of heuristic programming methods using evolutionary and genetic algorithms are described, along with application of neural networks and fuzzy rule-based systems for inferring reservoir system operating rules.

Optimal Operation of Multireservoir Systems: State-of-the-Art Review

This paper forms the second part of the series on application of artificial neural networks (ANNs) in hydrology. The role of ANNs in various branches of hydrology has been examined here. It is foun...

Artificial Neural Networks in Hydrology. II: Hydrologic Applications

For those who have lost the ability to move their hand, going through repetitious motions with the assistance of a therapist is the main method of recovery. We have been developed a robotic assistive device to rehabilitate the hand motions in place of the traditional therapy. The developed assistive device (RAD-HR) is comprised of four degrees of freedom enabling basic movements, hand function, and assists in supporting the hand during rehabilitation. We used a nonlinear computed torque control technique to control the RAD-HR. The accuracy of the controller was evaluated in simulations (MATLAB/Simulink environment). To see the robustness of the controller external disturbance as modelling uncertainty (±10% of joint torques) were added in each joints. Keywords—Biorobotics, rehabilitation, nonlinear control, robotic assistive device, exoskeleton.

Modeling and control of a 4dof robotic assistive device for hand rehabilitation

This paper proposes a new approach to optimize the path of a mobile traveling through environments containing both static and dynamic obstacles. It aims to accurately represent the known environment in order to give the mobile robot all the required information needed to move through the plan without striking any obstacles. When the workspace modeling is too complex, the algorithm will more likely need too much time to treat the modeling data (data used to model the environment in the program) and consequently slow the execution of the robot's tasks. The particularity of the method is in the representation of the static environment in a judicious way facilitating the path planning and reducing the processing time. Moreover, when an unexpected obstacle blocks the robot trajectory, the method uses the robot sensors to detect the obstacle, finds a best way to circumvent it and then resumes its path toward the desired destination. Experimental results showed the effectiveness of the proposed approach.

Trajectory optimization in both static and dynamic environments

This paper proposes a novel sliding mode control approach applied on an active suspension system. This approach is based on a design of an Exponential Reaching Law which allows chattering reduction on control input, while keeping high tracking performance. The exponential term of the reaching law allows the sliding function to dynamically adapt to the system's variations.

ERL sliding mode control of an electrohydraulic active suspension

In this research, we propose a novel sliding mode controller (SMC) to control the nonlinear systems. The proposed control approach includes a modification of the reaching law that overcomes the major limitations of the SMC. The proposed reaching law, unlike the existing ones, provide high trajectory tracking performance by effectively reducing the undesirable chattering problem and faster converging the system trajectories to zero. Thus the proposed reaching law allows benefiting from its advantages (faster convergence, reduced chattering, and high trajectory tracking), as well as overcome the limitations of both conventional sliding mode control (SMC) and the exponential reaching law (ERL). To evaluate the performance of the proposed controller and validate our propositions in real-time, experiments have been carried out with a wearable upper extremity exoskeleton robot named ETS-MARSE. Further, the experimental results were compared to the results with the conventional SMC and ERL to demonstrate the better performance of the proposed controller.

Novel Adaptive Reaching Law for Sliding Mode Control of an Upper Limb Exoskeleton Robot

In this paper we present a convergence analysis of an iterative method to obtain the inverse model in the virtual joint space of a class of flexible manipulators. Virtual joints are defined so as to be related kinematically to the workspace. Thus, when the desired trajectory can be transformed from the workspace to the virtual joint space, the inverse model in the virtual joint space can be used to obtain a trajectory tip-tracking controller. Because the robot model in the virtual joint space is a non-minimum phase system, its inverse is unstable. The inverse method is then based on a causal-anticausal integration approach used in an iterative manner. The convergence analysis of this inverse algorithm is based on the contraction-mapping theorem and provides a very simple way to expand the desired trajectory to ensure its convergence. Finally, the inverse algorithm and its convergence analysis are validated by simulating a controller, based on the inverse model, that drives a two-link manipulator made up o...

Maarouf Saad

Papers

Modeling and control of a 4dof robotic assistive device for hand rehabilitation

Trajectory optimization in both static and dynamic environments

ERL sliding mode control of an electrohydraulic active suspension

Novel Adaptive Reaching Law for Sliding Mode Control of an Upper Limb Exoskeleton Robot

Convergence analysis of an inverse flexible manipulator model algorithm