Terminal Sliding Mode Controllers for Hydraulic Turbine Governing System with Bifurcated Penstocks under Input Saturation

Terminal sliding mode controller method is introduced to enhance the regulation performance of the hydraulic turbine governing system(HTGS).For the purpose of describing the characteristics of controlled system and deducing the control rule,a nonlinear mathematic model of hydraulic turbine governing system with bifurcated penstocks(HTGSBF)under control input saturation is established,and the input/output state linearization feedback approach is used to obtain the relationship between turbine speed and controller output.To address the control input saturation problem,an adaptive assistant system is designed to compensate for controller truncation.Numerical simulations have been conducted under fixed point stabilization and periodic orbit tracking conditions to compare the dynamic performances of proposed terminal sliding mode controllers and conventional sliding mode controller.The results indicate that the proposed terminal sliding mode controllers not only have a faster response and accurate tracking results,but also own a stronger robustness to the system parameter variations.Moreover,the comparisons between the proposed terminal sliding mode controllers and current most often used proportional-integral-differential(PID)controller,as well its variant NPID controller,are discussed at the end of this paper,where the superiority of the terminal sliding mode controllers also have been verified.

The“Great Flood”of 1926:environmental change and post-disaster management in British Malaya

This paper is an historical case study of a major flood that occurred in British Malaya in 1926.It focuses on two key points.First,that the magnitude and subsequent impacts of the flood were exacerbated by contemporary industrial,agricultural,and hydraulic practices.Second,that this event pushed the British colonial government toward improving their land and river management strategies over the following decades.This article draws on recent research arguing the importance of an historical approach to disaster,as it enables greater insight into a disaster’s causes and long-term political,social,and environmental ramifications.Focussing on December 1926-a month of especially severe flooding likely linked to La Niña-this article will explore how those inundations became disastrous because of man-made changes enacted on the local environment.It will consider the sequential effect of the inundations,from their immediate to medium-term impact on the environment,to subsequent government-led flood mitigation schemes.By viewing the mid-1920s floods as a catalyst for change,with the benefit of hindsight,it is also possible to assess how far these changes were positive or negative.