Qinjie Yang, Guozhe Shen, Chao Liu, Zheng Wang, Kai Zheng and Rencheng Zheng
Steer-by-wire (SBW) system mainly relies on sensors, controllers and motors to replace the traditionally mechanical transmission mechanism to realize steering functions. However…
Abstract
Purpose
Steer-by-wire (SBW) system mainly relies on sensors, controllers and motors to replace the traditionally mechanical transmission mechanism to realize steering functions. However, the sensors in the SBW system are particularly vulnerable to external influences, which can cause systemic faults, leading to poor steering performance and even system instability. Therefore, this paper aims to adopt a fault-tolerant control method to solve the safety problem of the SBW system caused by sensors failure.
Design/methodology/approach
This paper proposes an active fault-tolerant control framework to deal with sensors failure in the SBW system by hierarchically introducing fault observer, fault estimator, fault reconstructor. Firstly, the fault observer is used to obtain the observation output of the SBW system and then obtain the residual between the observation output and the SBW system output. And then judge whether the SBW system fails according to the residual. Secondly, dependent on the residual obtained by the fault observer, a fault estimator is designed using bounded real lemma and regional pole configuration to estimate the amplitude and time-varying characteristics of the faulty sensor. Eventually, a fault reconstructor is designed based on the estimation value of sensors fault obtained by the fault estimator and SBW system output to tolerate the faulty sensor.
Findings
The numerical analysis shows that the fault observer can be rapidly activated to detect the fault while the sensors fault occurs. Moreover, the estimation accuracy of the fault estimator can reach to 98%, and the fault reconstructor can make the faulty SBW system to retain the steering characteristics, comparing to those of the fault-free SBW system. In addition, it was verified for the feasibility and effectiveness of the proposed control framework.
Research limitations/implications
As the SBW fault diagnosis and fault-tolerant control in this paper only carry out numerical simulation research on sensors faults in matrix and laboratory/Simulink, the subsequent hardware in the loop test is needed for further verification.
Originality/value
Aiming at the SBW system with parameter perturbation and sensors failure, this paper proposes an active fault-tolerant control framework, which integrates fault observer, fault estimator and fault reconstructor so that the steering performance of SBW system with sensors faults is basically consistent with that of the fault-free SBW system.
Details
Keywords
Zhiqiang Liu, Saidatunur Fauzi Saidin and Mohammad Noor Hisham Osman
The purpose of this paper is to investigate the effect of internal control (IC) on earnings quality from the perspective of the capital market. Specifically, it examines the…
Abstract
Purpose
The purpose of this paper is to investigate the effect of internal control (IC) on earnings quality from the perspective of the capital market. Specifically, it examines the effect of IC on earnings response coefficients.
Design/methodology/approach
This study uses the moderated regression analysis on a sample of 1,310 Chinese listed firms on the Shanghai Stock Exchange (SSE) from 2020 to 2022. It employed an earnings response coefficient model by Holthausen and Verrecchia (1988) and used the IC score produced by the index created by the Shenzhen Dibo Enterprise Risk Management Technology, i.e. DIB IC, and risk management database.
Findings
The study finds that the capital market placed lower earnings reliability on companies with high IC. This suggests that investors perceived negatively on the IC score of China listed companies, possibly due to their negative perception on the reason for implementation of high IC by those companies. A high IC score may raise suspicion amongst investors that the company has internal issues.
Research limitations/implications
This study adds to the limited studies on less regulated internal governance mechanisms from the perspective of the capital market. The contradictory result suggests the need for more studies before deriving a solid conclusion.
Originality/value
This study focusses on the under research area of IC rather than the common board of directors and from the perspective of Chinese economies, limited studies of developed countries.