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In this paper, an extended state observer based fractional‐order sliding mode control strategy is studied for vehicle steer‐by‐wire systems (SBWSs). The parameter perturbation and external interference are considered in the dynamic model of SBWSs. A fractional‐order sliding mode control scheme is designed to solve the tracking problem and improve the control performance. An extended state observer is further used to estimate the lumped disturbance, and then the estimated value is considered as a feedforward compensation to reduce the chattering phenomenon. Finally, comparison simulation results show that the excellent steering tracking and strong robustness performance have been achieved by the proposed control strategy for SBWSs. A fractional‐order sliding mode control with extended state observer strategy is studied to control a vehicle steer‐by‐wire system. It investigates the dynamic equation of motion of steer‐by‐wire system with lumped disturbance. An extended state observer is used to estimate the lumped disturbance and provide with a compensation.

This study introduces stator currents‐based model reference adaptive system (MRAS) estimators that employ variable structured control (VSC) in the adaptation mechanism to enable the online estimation of stator resistance and permanent magnet (PM) flux in interior permanent magnet synchronous motors (IPMSMs). These MRAS estimators estimate stator resistance and PM flux by analysing the error between the stator currents measured as the reference model and the stator currents generated by the adaptive model. The performance of the proposed estimators is assessed through simulation studies. Furthermore, the proposed approach is compared to a conventional MRAS employing a fixed‐gain proportional‐integral (PI) controller. Simulation results and error analyses indicate that the VSC‐based MRAS algorithms outperform traditional PI‐based MRAS in terms of accuracy and reliability. Additionally, the proposed method eliminates the reliance on a fixed‐gain PI controller, a common component in conventional MRAS systems.

In this paper, a robust nonlinear approach for control of liquid levels in a quadruple tank system (QTS) is developed based on the design of an integrator backstepping super-twisting controller, which implements a multivariable sliding surface, where the error trajectories converge to the origin at any operating point of the system. Since the backstepping algorithm is dependent on the derivatives of the state variables, and it is sensitive to measurement noise, integral transformations of the backstepping virtual controls are performed via the modulating functions technique, rendering the algorithm derivative-free and immune to noise. The simulations based on the dynamics of the QTS located at the Advanced Control Systems Laboratory of the Pontificia Universidad Católica del Perú (PUCP) showed a good performance of the designed controller and therefore the robustness of the proposed approach.

This study presents the design of a current control loop and the selection of switching logic for pulse-width modulation (PWM) of three-phase switching converters. This approach is based on a deliberate introduction of the predictive sliding mode motion within a control system. It shows that the selection of the PWM pattern is a direct result of sliding mode existence within the current control closed-loop system. The design specifications are robustness to load electrical parameters, fast dynamic response, reduced switching frequency and simple hardware implementation. To meet previous specifications, a sliding mode controller has been developed, designed as a finite state machine, and implemented within a field programmable gate array device. The switching strategy implemented within the state transition diagram provides for a minimum number of switch state changes by the three-phase converter that is confirmed through simulation and experimental results.

This study investigates the finite-time attitude-tracking problem for rigid spacecraft. A novel non-singular terminal sliding-mode control (NTSMC) law is designed to provide finite-time convergence and fast, high control precision even though inertia uncertainties and external disturbances affect the spacecraft systems under actuator failures and saturations. The proposed NTSMC scheme is chattering suppression and singularity-free. Simulation results are presented to demonstrate the efficiency of the proposed method.

This paper proposes a two-level control strategy based on a super-twisting sliding-mode algorithm (STA) to optimally allocate power imbalances in shipboard microgrids (SMGs) while achieving frequency regulation. The strategy employs an STA observer to estimate the unknown power load demand imbalances in finite time. This estimate is then passed to an online high-level optimal control framework to periodically determine the optimal sequence of power reference values for each energy storage device (ESS), minimising the operational cost of the SMG. The online optimised power reference values are interpolated and passed to the low-level STA control strategy to control the output power of each ESS. The efficacy of the proposed methods is demonstrated through numerical simulations conducted on a prototypical model of an SMG equipped with two ESSs, namely batteries and fuel cells with associated hydrogen storage.

This study investigates the finite-time cooperative-tracking problem for a class of networked Euler–Lagrange systems with a leader–follower structure, where the leader has an active dynamics and only a subset of the followers have access to the leader system. A novel framework for the design of finite-time cooperative-tracking controller is proposed by using sliding-mode control theory and graph theory. First, a finite-time sliding-mode tracking protocol is proposed for the networked Lagrange systems in the presence of bounded model uncertainties and external disturbances. Under the condition that the bounds of the model uncertainties and external disturbances are unknown, adaptive finite-time cooperative-tracking protocol is then presented. The finite convergence time is also estimated. Finally, we analyse the tracking performance of the networked uncertain Lagrange systems under the action of a continuous control protocol, which guarantees that the tracking errors converge to an arbitrarily small bound around zero in finite time. Simulation examples are presented to show the effectiveness of the obtained theoretical results.

In this study, a new model-based fault detection and isolation (FDI) strategy is proposed for field-oriented control (FOC) induction motor (IM) drives. Actuator faults are addressed, and specifically, single open-circuit faults are considered in this study. The residual signals are synthesised by taking the resulting closed-loop dynamics when a FOC strategy is applied, that is, the residuals are referenced to the synchronous reference frame (dqe-coordinates), which are generated by using a bank of variable structure observers to obtain a robust FDI scheme. Thus, subsystems sensitive to a specific fault, but decoupled from other faults are obtained in a natural way, where only two stator currents and the mechanical position are required for fault isolation purposes. Residual evaluation is carried out in the stator reference frame (dq-coordinates) for the IM model, where the residual direction (angle) is employed to isolate a fault in each one of the six power switches in a voltage source inverter. In addition, the observer FDI scheme can be combined with a fault re-configuration strategy in order to improve the reliability of the motor drive. Experimental results are illustrated for a three-phase 3/4 HP IM drive at different reference frequencies and load torques with single open-circuit faults that verify the ideas presented in this work.

The present study proposes two schemes for simultaneously estimating actuator and sensor faults for a class of uncertain non-linear systems. In the first scheme, two sliding mode observers (SMOs) are designed to estimate actuator and sensor faults, respectively, under the assumption that the matching condition holds. In the second scheme, the assumption of matching condition is relaxed and an adaptive observer has been designed to estimate the sensor fault instead of using an SMO. The effects of the system uncertainties on the estimation errors of states and faults are reduced by integrating a prescribed ℋ∞ disturbance attenuation level into the proposed schemes. The sufficient condition for the existence of the proposed observers with ℋ∞ tracking performance is derived and expressed as a linear matrix inequality optimisation problem such that the ℒ2 gain between the estimation errors and system uncertainties is minimised. Finally, a simulation study is presented to illustrate the effectiveness of the proposed schemes.

The article presents a new approach to the analysis of the stability of automatic systems with discrete links. In almost all modern automatic control systems (ACS), there are links that break signals in time. These are power controlled switches—transistors or thyristors operating in a pulsed mode and digital links in regulators. Time discretization significantly affects the stability of processes in the automatic control system. The theoretical analysis of such systems is rather complicated and requires a significant change in engineering approaches to analysis. With the improvement of digital controllers and a significant increase in their performance, this problem has practically been forgotten. However, its mathematical “content” has not changed since the 1980s when discreteness began to play a major role in hindering the transition to digital automatic control systems. In this paper, we propose a new approach that consists of interpreting the sampling operation by a link with the proposed frequency characteristic, which determines the suppression of input high-frequency signals. This link greatly simplifies engineering calculations and demonstrates the new capabilities of sampling systems. These possibilities include the rational distribution of digitalization resources—the number of bits and the sampling interval between the regulator channels, depending on the frequency range of the efficiency of these channels. We verify and confirm our theoretical statements through simulations and show how this approach makes it possible to formulate new principles of construction of seemingly well-known controllers—PID (Proportional Integral Differential) controllers and variable structure systems (VSS).