Electro-hydraulic actuators (EHAs) have been widely used in modern industries. However, sensor faults and actuator faults in EHA systems can arise due to aging during operation, making the system unstable and unsafe. To solve these issues, fault-tolerant control (FTC) techniques for EHA systems have been studied intensively. In this paper, an FTC is proposed and developed for the mini motion package (MMP) EHA system. First, a mathematical model of the MMP system is formulated and improved to provide position tracking control using a well-known proportional-integral-derivative (PID) controller. Second, an unknown input observer (UIO) reconstruction is performed to estimate the states, disturbances, and sensor faults so that an asymptotically stable control error can be obtained by a linear matrix inequality (LMI) optimization algorithm through Lyapunov’s stability condition. Third, the FTC designed for the nonlinear discrete-time system is formed from fault compensation based on a residual logic signal to implement the fault compensation process and ensure stability and tracking performance with respect to minimizing impacts of disturbances and sensor faults. Here, residual is defined by the difference between state response and state estimation. Finally, numerical simulations and experiments of the MMP system are presented to illustrate the efficiency of the proposed FTC technique.

Background: Treatment inertia, non-adherence and non-persistence to medical treatment contribute to poor blood pressure (BP) control worldwide. Fixed dose combination (FDC) antihypertensive medicines simplify prescribing patterns and improve adherence. The aim of this study was to identify factors associated with prescribing FDC antihypertensive medicines and to understand if these factors differ among doctors worldwide. Methods: A cross-sectional survey was conducted online from June 2023 to January 2024 to recruit doctors. We collaborated with an international network of researchers and clinicians identified through institutional connections. A passive snowballing recruitment strategy was employed, where network members forwarded the survey link to their clinical colleagues. The survey instrument, developed through a literature review, interviews with academic and clinical researchers, and pilot testing, assessed participants perspectives on prescribing FDC antihypertensive medicines for hypertension. Participants rated their level of agreement (5-point Likert scale) with statements representing six barriers and four facilitators to FDC use. Findings: Data from 191 surveys were available for analysis. 25% (n = 47) of participants worked in high-income countries, 38% (n = 73) in upper-middle income, 25% (n = 48) in lower-middle income, 6% (n = 10) in low-income countries. Forty percent (n = 70) of participants were between 36–45 years of age; two thirds were male. Cost was reported as a barrier to prescribing FDC antihypertensive medicines [51% (n = 87) agreeing or strongly agreeing], followed by doctors’ confidence in BP measured in clinic [40%, (n = 70)], access [37%, (n = 67)], appointment duration [35%, (n = 61)], concerns about side-effects [(21%, n = 37)], and non-adherence [12%, (n = 21)]. Facilitators to FDC antihypertensive polypills prescribing were clinician facing, such as access to educational supports [79%, (n = 143)], more BP measurement data [67%, (n = 120)], a clinical nudge in health records [61%, (n = 109)] and patient-facing including improved patient health literacy [49%, (n = 88)]. The levels of agreement and strong agreement across all barriers and facilitators were similar for participants working in higher or lower income countries. Across all countries, participants rated FDC antihypertensive medications highly valuable for managing patients with non-adherence, (82% reported high or very high value), for patients with high pill burden (80%). Interpretation: Cost and access were the most common barriers to prescribing FDCs across high- and low-income countries. While greater educational support for clinicians was perceived as the leading potential facilitator of FDC use, this seems unlikely to be effective without addressing access.

With the rapid development of computer science and information and communication technology (ICT), increasingly intelligent, and complex systems have been applied to industries as well as human life. Fault-tolerant control (FTC) has, therefore, become one of the most important topics attracting attention from both engineers and researchers to maintain system performances when faults occur. The ultimate goal of this study was to develop a sensor fault-tolerant control (SFTC) to enhance the robust position tracking control of a class of electro-hydraulic actuators called mini motion packages (MMPs), which are widely used for applications requiring large force-displacement ratios. First, a mathematical model of the MMP system is presented, which is then applied in the position control process of the MMP system. Here, a well-known proportional, integrated and derivative (PID) control algorithm is employed to ensure the positional response to the reference position. Second, an unknown input observer (UIO) is designed to estimate the state vector and sensor faults using a linear matrix inequality (LMI) optimization algorithm. Then an SFTC is used to deal with sensor faults of the MMP system. The SFTC is formed of the fault detection and the fault compensation with the goal of determining the location, time of occurrence, and magnitude of the faults in the fault signal compensation process. Finally, numerical simulations were run to demonstrate the superior performance of the proposed approach compared to traditional tracking control.

In recent years, electro-hydraulic systems have been widely used in many industries and have attracted research attention because of their outstanding characteristics such as power, accuracy, efficiency, and ease of maintenance. However, such systems face serious problems caused simultaneously by disturbances, internal leakage fault, sensor fault, and dynamic uncertain equation components, which make the system unstable and unsafe. Therefore, in this paper, we focus on the estimation of system fault and uncertainties with the aid of advanced fault compensation techniques. First, we design a sliding mode observer using the Lyapunov algorithm to estimate actuator faults that produce not only internal leakage fault but also disturbances or unknown input uncertainties. These faults occur under the effect of payload variations and unknown friction nonlinearities. Second, Lyapunov analysis-based unknown input observer model is designed to estimate sensor faults arising from sensor noises and faults. Third, to minimize the estimated faults, a combination of actuator and sensor compensation fault is proposed, in which the compensation process is performed due to the difference between the output signal and its estimation. Finally, the numerical simulations are performed to demonstrate the effectiveness of the proposed method obtained under various faulty scenarios. The simulation results show that the efficiency of the proposed solution is better than the traditional PID controller and the sensor fault compensation method, despite the influence of noises.

Recent innovations in Light-emitting diode (LED) technology and Internet of Things applications have promoted the development of visible light communication and localization applications. LED-based indoor positioning application has been a potential topic attracting the attention of many researchers because this positioning technique provides high accuracy, low cost, simple operation, and medium complexity. This paper focuses on analyzing the positioning quality with different LED layout structures. Furthermore, we consider the influence of noise in these models through the ensemble learning algorithm. We also combine the ensemble learning method with the trilateration algorithm in the proposed solution. The numerical simulation results show that the proposed solution respectively achieved a positioning accuracy of 0.023, 0.011, and 0.009 m when we considered the negative effect of all noises in 3 distinct layouts: 3 LEDs, 4LEDs, and 5 LEDs.

Hydraulic-electric systems are widely utilized in various applications. However, over time, these systems may encounter random faults such as loose cables, ambient environmental noise, or sensor aging, leading to inaccurate sensor readings. These faults may result in system instability or compromise safety. In this paper, we propose a fault compensation control system to mitigate the effects of sensor faults and ensure system safety. Specifically, we utilize the pressure sensor within the system to implement the control process and evaluate performance based on the piston position. First, we develop a mathematical model to identify optimal parameters for the fault estimation model based on the Lyapunov stability principle. Next, we design an unknown input observer that estimates the state vector and detects pressure sensor faults using a linear matrix inequality optimization algorithm. The estimated pressure faults are incorporated into the fault compensation control system to counteract their effects via a fault residual coefficient. The discrepancy between the feedback state and the estimated state determines this coefficient. We assess the piston position’s performance through pressure control to evaluate the proposed model’s effectiveness. Finally, the system simulation results are analyzed to validate the efficiency of the proposed model. When a pressure sensor fault occurs, the proposed approach effectively minimizes position control errors, enhancing overall system stability. When a pressure sensor fault occurs, the proposed model compensates for the fault to mitigate the impact of pressure problem, thereby enhancing the position control quality of the EHA system. The fault compensation method ensures over 90% system performance, with its effectiveness becoming more evident under pressure sensor faults.