Quantized control settings based tuning of a heaving wave energy converter in irregular seas

The increasing awareness of environmental issues attracts more attention on environmentally friendly energy sources. This leads to increasing research on effective use of renewable energy sources. Among them, wave energy offers a high potential. The wave energy converter systems used for transforming the wave energy into electrical energy have been a main research topic for decades. However, only a few of these systems has been successfully implemented. There seems to be some technical problems one of which is on their control applications. It has been reported that by means of appropriate control implementation, the performance of the wave energy converter system could be improved considerably. In literature, many different control techniques are reported. They appear to be weak due to implementation related restrictions. The present study proposes a novel control technique that is far more practical based on quantization of control settings. Various quantization levels and their effect on system power capture performance are studied. The technique assumes use of realistic off-the-shelf components with realistic features. The proposed method utilizes time-series-analysis technique with online parameter estimation feature. This new method does not require any knowledge of previous or future states of any of the system or sea state parameters, but only the currently available and measurable ones. The approach of the new control technique sets it apart from most of the previously reported ones. Therefore, the proposed technique is not only very much practical but also very much useful in improvement of the system power performance relative to passive techniques. © 2016 Taylor & Francis Group, LLC

An enhanced control technique for the elimination of residual vibrations in flexible-joint manipulators

One method used to reduce or eliminate residual vibrations is to modify the input signal by using previously determined system parameters. In order to eliminate the residual vibration completely, these system parameters must be very accurately determined. In real systems, achieving such accuracy may not always be possible. To address this problem and to provide a solution, a new residual vibration elimination method is introduced in this study, which has proven to be useful especially in cases of uncertain parameters of estimated or predicted systems. It is shown that the technique is capable of handling high levels of uncertainty and is able to successfully eliminate or reduce residual vibrations in flexible systems. In this approach, the desired position of the system is primarily divided into two equal parts, and the generated input signal is used to eliminate vibration. This study presents theoretical and experimental results of the techniques applied to a flexible mechanical system; a comparative study of robustness performance is also provided. Simulation and experimental results show that the oscillations are considerably decreased with a high degree of robustness in the presence of uncertainty regarding system parameters. © 2014 Journal of Mechanical Engineering. All rights reserved