Huaishu Li, Lizhong Song and Yanhui Lai
In order to improve performance robustness of control systems, the discrete variable structure control (VSC) design for uncertain systems and its application to a ship autopilot…
Abstract
Purpose
In order to improve performance robustness of control systems, the discrete variable structure control (VSC) design for uncertain systems and its application to a ship autopilot are to be discussed in this paper.
Design/methodology/approach
Discrete‐time variable structure control (DVSC) becomes worth investigating and various DVSC methods have been suggested by many papers. The approach that used the reaching law for controller design can describe how the switching function decreases toward zero and easier to obtain the control law, but this conventional method has some defects not to be ignored. First, due to the influence of the conventional discrete reaching law itself, the system trajectory oscillates in a neighborhood of the origin rather than converges to the origin. Second, this method requires that the uncertainty bound is known as a premise to assure robustness, so creates an over‐conservative controller and enlarges chattering.
Findings
It can be shown that the estimation error dynamics can be decoupled from sliding surface dynamics using the proposed scheme. Robust stability of the closed‐loop system can be ensured in the presence of uncertainties with bounded changing rate. No chattering occurs.
Practical implications
To supply useful references to controller design.
Originality/value
A new approach in the design of discrete VSC based on the reaching law approach is presented, a new discrete reaching law, which is stable at the origin, is proposed, and an algorithm for uncertainty estimation is developed in this paper. The proposed algorithm is applied to the control of a ship autopilot servo system. Simulation results show that the controller designed here can track a desired course well and exhibits very good performance robustness.
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Yanhui Lai, Xiaofeng Zhang and Lizhong Song
The purpose of this paper is to overcome the shortcoming that discrete variable structure control (VSC) system trajectory oscillates in a neighborhood of the origin.
Abstract
Purpose
The purpose of this paper is to overcome the shortcoming that discrete variable structure control (VSC) system trajectory oscillates in a neighborhood of the origin.
Design/methodology/approach
Among all the proposed reaching laws, W. Gao's theory is most perfect. It makes great progress in revealing the motion mechanism of discrete‐time VSC systems. However, it has an obvious defect, i.e. the system trajectory oscillates in a neighborhood of the origin rather than converges to the origin. So, a new reaching law named variable rate reaching law to which the stability at the origin can be expected is proposed. The special feature of this new reaching law is that it is directly proportional to the norm of the state vector and can result in a sector‐shaped switching region. On the basis of analyzing the characteristic of the variable rate and the conventional reaching laws, a new combined control algorithm that discards the shortcomings of the two reaching laws and carries on their merits is formed, so satisfactory control performance can be achieved.
Findings
A new combined reaching law control algorithm, which uses the exponential rate reaching law in the reaching mode and in the front phase of the sliding mode, and uses the variable rate reaching law in the back phase of the sliding mode and in the steady‐state mode, is formed.
Practical implications
The paper is a very useful reference for control system designers.
Originality/value
The new control strategy is applied to the controller design for a brushless DC servomotor and good control performance is obtained.
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Tingli Liu, Ying Jiang and Lizhong Hao
Although short selling has been legalized in China for nearly 10 years, due to the existence of short-sale constraints, its impact on corporate governance of listed companies…
Abstract
Purpose
Although short selling has been legalized in China for nearly 10 years, due to the existence of short-sale constraints, its impact on corporate governance of listed companies remains unclear. This paper aims to examine the impact of short-sale refinancing on earnings quality after the short-selling constraints have been released. The authors further explore whether this impact is subject to the nature of property rights and shareholding structures.
Design/methodology/approach
This study is based on a sample of A-share firms in China for the period 2014–2016. The authors use earnings response coefficients (ERC) as a proxy for earnings quality. To empirically examine this issue, a matching sample is generated by using propensity score matching method (PSM) to reduce sample selection bias.
Findings
This study provides evidence that deregulation of short selling has positive external effect on corporate governance. The results indicate that the potential short-selling opportunities can effectively suppress earnings manipulation and improve earnings quality. However, the impact of short selling on earnings quality varies for companies with different nature of property rights and shareholding structure.
Originality/value
To the best of the authors’ knowledge, this is the first study to investigate the relationship between short selling and earnings quality in the unique setting of short-sale refinancing. This study provides new evidence on the impact of short selling at the micro level and calls for further deregulation of short selling. In addition, this study contributes to existing studies on short-sale refinancing by examining an emerging market.
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Yanqiu Chen, Xiaodong Zhou, Taolin Zhang, Zhijian Fu, Yuqi Hu and Lizhong Yang
– The purpose of this paper is to study the behavior of smoke flow in building fires and optimize the design of smoke control systems.
Abstract
Purpose
The purpose of this paper is to study the behavior of smoke flow in building fires and optimize the design of smoke control systems.
Design/methodology/approach
A total of 435 3-D fire simulations were conducted through NIST fire dynamics simulator to analyze thermal behavior of combined buoyancy-induced and pressure-driven smoke flow in complex vertical shafts, under consideration of influence of heat release rate (HRR) and locations of heat sources. This influence was evaluated through neutral pressure plane (NPP), which is a critical plane depicting the flow velocity distributions. Hot smoke flows out of shafts beyond the NPP and cold air flows into shafts below the NPP.
Findings
Numerical simulation results show that HRR of heat source has little influence on NPP, while location of heat source can make a significant difference to NPP, particularly in cases of multi-heat source. Identifying the location of NPP helps to develop a more effective way to control the smoke with less energy consumption. Through putting an emphasis on smoke exhausting beyond the NPP and air supplying below the NPP, the smoke control systems can make the best use of energy.
Research limitations/implications
Because of the chosen research approach, the research results may need to be tested by further experiments.
Practical implications
The paper includes implications for the optimization of smoke control systems design in buildings.
Originality/value
This paper fulfills an identified need to research the behavior of hot smoke in building fires and optimize the design of smoke control systems.
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After Ma Yingjeou's re‐election in 2012, Mainland China and Taiwan will continue cooperation in economic fields. The purpose of this paper is to undertake research on a bilateral…
Abstract
Purpose
After Ma Yingjeou's re‐election in 2012, Mainland China and Taiwan will continue cooperation in economic fields. The purpose of this paper is to undertake research on a bilateral investment agreement (BIA) between Mainland China and Taiwan.
Design/methodology/approach
The paper uses statistics to demonstrate the growing cross‐strait investment and incompetent contemporary investment protection mechanisms in Mainland China and Taiwan. The paper also compares laws in Mainland China and Taiwan and the investment protection agreements concluded by Mainland and Taiwan with other countries, respectively.
Findings
Based on the similarities of current laws and the investment protection agreements concluded by Mainland China and Taiwan with other countries, respectively, Mainland China and Taiwan can possibility agree upon major provisions of a BIA. Solutions are provided to both macro and micro challenges against a successful BIA.
Research limitations/implications
It is hard to predict whether the BIA will promote political integration between Mainland China and Taiwan in the near future.
Practical implications
A BIA can boost investors' confidence.
Social implications
This paper may serve as a humble reference for both the Mainland China and Taiwan government when negotiating the BIA.
Originality/value
Cross‐strait investment is an important and prosperous field in practice, but has not been fully explored in literature thus far. This Article aims to fill this gap.
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Mohammad Farhan Shaikh and Nallasivam K
In this study, a finite element model of a box-girder bridge along with the railway sub-track system is developed to predict the static behavior due to different combinations of…
Abstract
Purpose
In this study, a finite element model of a box-girder bridge along with the railway sub-track system is developed to predict the static behavior due to different combinations of the Indian railway system and free vibration responses resulting in different natural frequencies and their corresponding mode shapes.
Design/methodology/approach
The modeling and evaluation of the bridge and sub-track system were performed using non-closed form finite element method (FEM)-based ANSYS software.
Findings
From the analysis, the worst possible cases of deformation and stress due to different static load combinations were determined in the static analysis, while different natural frequencies were determined in the free vibrational analysis that can be used for further analysis because of the dynamic effect of the train vehicle.
Research limitations/implications
The scope of the current investigation is confined to the structure's static and free vibration analysis. However, this study will help the designers obtain relevant information for further analysis of the dynamic behavior of the bridge model.
Originality/value
In static analysis, the maximum deformation of the bridge deck was found to be 10.70E-03m due to load combination 5, whereas the maximum natural frequency for free vibration analysis is found to be 4.7626 Hz.