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It is well known that activities in running water or wind and waves expose the Autonomous Surface Vessels (ASVs) to considerable challenges. Under these conditions, it is essential to develop a robust control system that can meet the requirements and ensure the safe and accurate execution of missions. In this context, this paper presents a new topology for controller design based on a combination of the Successive Loop Closure (SLC) method and optimal control. This topology enables the design of robust autopilots based on the Proportional-Integral-Derivative (PID) controller. The controllers are tuned from the solution of the optimal control problem, which aims to minimize the effects of model uncertainties. To verify the effectiveness of the proposed controller, a numerical case study of a natural ASV with 3 Degree of Freedom (DoF) is investigated. The results show that the methodology enabled the tuning of a PID controller capable of dealing with different parametric uncertainties, demonstrating robustness and applicability for different prototype scenarios.

In this paper, afull-car prototype of the recently proposed mechatronic suspension, Series Active Variable Geometry Suspension (SAVGS), is developed for on-road driving experimental proof of concept, aiming to be adopted by suspension OEMs (original equipment manufacturers) as an alternative solution to fully active suspensions. Particularly, mechanical modifications are performed to both corners of the front double-wishbone suspensionof a production car, with active single-links attached to the upper-ends of the spring-damper units, while both corners of the rear suspension remain inthe original (passive) configurations.The mechanical modifications involve innovatively designed parts to enable the desired suspension performance improvements, while maintaining ride harshness at conventional levels.Areal-time embedded system is further developed to primarily implement:1) power supply, data acquisition and measurementsof the vehicle dynamics related variables, and 2) robust control application for the ride comfort and road holding enhancement, which is based on a derived linearized model of the full-car dynamics and a newly synthesizedH-infinity control scheme. Results obtained from on-road driving experiments are inessential agreement with numerical simulation results also produced. Overall, the full-car prototypeof SAVGS demonstrates promising suspension performance,with anaverage 3 dB attenuation (or equivalently 30% reduction) of the chassis vertical acceleration at aroundthe human-sensitive frequencies (2-5Hz),as compared to the original vehicle with the passive suspension system. More importantly, the prototype also indicatesthe practicality of the solution, as the SAVGS retrofit to a real car is achieved by simple mechanical modifications, compact actuator packaging, smallmass increment(21.5kg increase with respect to the original vehicle), limited power usage (an average value of 134W in DC batteries with a Class D random road) and acceptable economic cost.

Academic studies on the Automatic Voltage Regulator (AVR) have focused on a linear mathematical model which lacks protective features. A more accurate model of the AVR system includes protective features as described in IEEE standards. The AVR models without protective features, namely limiters, result in less accurate control performance since the outputs of real controllers are always bounded. In the present study, the controller outputs are limited between -0.9pu and 1.0pu, and the upper bound of exciter output is limited by 3.1pu with the direction of IEEE standards. The effect of limiters on the controller performance is investigated. Two controllers with a novel sliding surface function are proposed based on a mathematical model of the AVR and its approximate reduced-order model. The proposed controllers having only two parameters are optimized with improved particle swarm optimization (PSO) algorithm. After optimization, the robustness of the controllers is compared with the results of various operating conditions identical to the previous studies. Although controller inputs and exciter outputs are limited, the maximum overshoot is measured as less than 0.1% at no-load conditions. Nominal time constants of the AVR constituents are perturbed from -50% to 50%, and ±10% load disturbance is applied to the output. The robustness of the controllers against parameter uncertainties is measured with an average overshoot at the output. Another superiority among the reported results in the literature is obtained from the proposed controllers, where the minimum average overshoot rates are obtained. In addition, when ±10% load is applied to the output of the AVR, the proposed controllers generate accurate control inputs to reject the load disturbance successfully. Furthermore, the proposed controllers keep the output within the ±5% band if there is a monotonic change at the output. All the results show that the proposed controllers with the improved PSO have drawn the best performance from the perspective of time-domain specifications in comparison with the recently reported controllers.

Purpose This study aims to develop a quadrotor with a robust control system against weight variations. A Proportional-Integral-Derivative (PID) controller based on Particle Swarm Optimization and Differential Evaluation to tune the parameters of PID has been implemented with real-time simulations of the quadrotor. Design/methodology/approach The optimization algorithms are combined with the PID control mechanism of the quadrotor to increase the performance of the trajectory tracking for a quadrotor. The dynamical model of the quadrotor is derived by using Newton-Euler equations. Findings In this study, the most efficient control parameters of the quadrotor are selected using evolutionary optimization algorithms in real-time simulations. The control parameters of PID directly affect the controller’s performance that position error and stability improved by tuning the parameters. Therefore, the optimization algorithms can be used to improve the trajectory tracking performance of the quadrotor. Practical implications The online optimization result showed that evolutionary algorithms improve the performance of the trajectory tracking of the quadrotor. Originality/value This study states the design of an optimized controller compared with manually tuned controller methods. Fitness functions are defined as a custom fitness function (overshoot, rise-time, settling-time and steady-state error), mean-square-error, root-mean-square-error and sum-square-error. In addition, all the simulations are performed based on a realistic simulation environment. Furthermore, the optimization process of the parameters is implemented in real-time that the proposed controller searches better parameters with real-time simulations and finds the optimal parameter online.

This work investigates the tracking control problem for underactuated mechanical systems. To this end, we develop an extension of the dynamic tube Model Predictive Control (MPC) approach by combining an MPC design, an ancillary energy shaping controller constructed with the Interconnection and Damping Assignment Passivity-Based Control methodology, and an analytical expression of the dynamic tube. In addition, we extend the proposed approach by including the adaptive compensation of a class of unknown disturbances. The stability analysis is presented by employing a Lyapunov approach. The effectiveness of the proposed controller is demonstrated with simulations on two underactuated systems: a two-mass-spring-damper system with uncertain damping and either linear or nonlinear spring; an inertia-wheel-pendulum with unmodeled disturbances.

This dissertation focuses on developing tools to study the robust forward invariance of sets for systems with unknown disturbances and hybrid dynamics. In particular, the notions of robust forward invariance properties are proposed for hybrid dynamical systems modeled by differential and difference inclusions with state-depending conditions enabling flows and jumps. A set is said to enjoy robust forward invariance for a system when its solutions start within the set always stay in the set regardless of disturbances. These proposed notions allow for a diverse type of solutions (with and without disturbances), including solutions that have persistent flow and jumps, that are Zeno, and that stop to exist after finite amount of (hybrid) time. Moreover, sufficient conditions for sets to enjoy such properties are presented. The proposed conditions involve the system data and the set to be rendered robust forward invariant.Furthermore, such conditions are exploited to derive conditions guaranteeing that sublevel sets of Lyapunov-like functions are robust forward invariant and, in turn, inspired a constructive way to design invariance-based control algorithms for a class of hybrid systems with control inputs and disturbances. More precisely, when a hybrid system have a Lyapunov-like function V satisfying a set of specific conditions, existence of feedback laws that render sublevel sets of V robustly forward invariant for the closed-loop hybrid systems are presented. In addition, two selection theorems are proposed to design invariance-based controllers for the class of hybrid systems considered.Applications and academic examples are given to illustrate the results. In particular, the presented forward invariance analysis and design tools are applied to the design and validate of hybrid controllers for power conversion systems, specifically, a single-phase DC/AC inverter and a DC/DC boost converter. Moreover, results are applied to the estimation of weakly forward invariant sets, which is an invariance property of interest when employing invariance principles to study convergence properties of solutions. Finally, the developed algorithms are tested on the control of a constrained bouncing ball system.

Nonlinear effects and external disturbances can severely impact the control of an autonomous race car at the handling limits. State-of-the-art approaches do not take these uncertainties explicitly ...

Servo sistemler, hassas konum kontrolü gerektiren birçok endüstriyel uygulamada yoğun olarak kullanılmaktadır. Ancak bu uygulamaların çoğunda karşılaşılan parametre belirsizlikleri, eşleşen ve eşleşmeyen bozucu etkenler, kontrolcü performansını olumsuz yönde etkilemektedir. Dolayısıyla endüstriyel kontrol uygulamalarında gürbüzlükte en az hassasiyet kadar önem taşımaktadır. Bu çalışmada, parametre belirsizlikleri ve bozucu girişe sahip bir döner servo sistemin hassas pozisyon kontrolü için Genişletilmiş Durum Gözlemcisine dayalı Kayan Kipli Kontrolcü (GDGKKK) tasarımı sunulmuştur. Önerilen kontrolcünün performansı, beş farklı belirsizlik ve bozucu giriş senaryosu için benzetim çalışmaları yapılarak test edilmiş ve etkinliğinin değerlendirilebilmesi için klasik Kayan Kipli Kontrol (SMC) ve Oransal Türevsel (PD) kontrol ile kıyaslanmıştır. MATLAB/Simulink yazılımında benzetim çalışmalarında Quanser SRV02 döner servo ünitesine ait matematiksel model kullanılmıştır. Benzetim sonuçları, PD kontrolün yük değişimlerine ve bozucu girişlere karşı oldukça duyarlı olduğunu, klasik SMC kontrolün ise yük değişimleri ve eşleşen bozuculara karşı dayanıklı olmakla birlikte eşleşmeyen bozuculara karşı duyarlı olduğunu göstermiştir. Diğer yandan sonuçlar, önerilen GDGKKK kontrolcünün hem yük değişimlerine hem de eşleşen ve eşleşmeyen bozuculara karşı son derece başarılı bir bozucu reddetme performansı sunduğunu açıkça göstermiştir., Servo systems are used extensively in many industrial applications that require precise position control. However, parameter uncertainties, matched and unmatched disturbances encountered in most of these applications adversely affect the controller performance. Therefore, in industrial control applications, robustness is at least as important as precision. In this study, an Extended State Observer-based Sliding Mode Controller (GDGKKK) design is presented for precise position control of a rotary servo system having parameter uncertainties and disturbance input. The performance of the proposed controller has been tested by performing simulation studies for five different uncertainty and disturbance input scenarios and compared with the traditional Sliding Mode Control (SMC) and Proportional Derivative (PD) control to evaluate its effectiveness. The mathematical model of the Quanser SRV02 rotary servo unit was used in the simulation studies in MATLAB/Simulink software. The simulation results show that the PD control is very sensitive to load changes and disturbances and while the traditional SMC control is insensitive to load changes and matched disturbances, it is sensitive to mismatched disturbances. On the other hand, the results clearly showed that the proposed GDGKKK controller offers extremely successful disturbance rejection performance against both load changes and matched and unmatched disturbances.

Microgrids consisting of photovoltaic (PV) power plants and wind farms have been widely accepted in power systems for reliability enhancement and power loss reduction. Microgrids are capable of providing voltage and frequency support, improving power quality, and achieving proper power-sharing. To achieve such goals and deal with the nonlinear behavior in such systems, appropriate robust control strategies are required to be adopted. This article presents a comprehensive review of robust control methods for microgrids, including AC, DC, and hybrid microgrids, with different topologies and different types of interconnection to conventional power systems based on recently published research studies. The main control objectives, along with proposed control methods, are comparatively discussed for different types of microgrids. Furthermore, several research gaps in this area related to the scalability, robustness assessment, and evaluation approach are discussed. Recommendations are made that can potentially open new research lines to enhance the effectiveness of robust controllers for AC, DC, and hybrid microgrids.

Heavy-duty vehicle platooning has received much attention as a method to reduce fuel consumption by keeping inter-vehicle distance short. When a platoon follows a fuel-optimal velocity profile calc...

This paper develops a novel robust control strategy for DC-DC buck converter subjected to varying load and parameter uncertainty. The proposal exploits the robustness of the sliding mode control (SMC) incorporated with proportional-proportional-integral-observer (PPIO) to assure tight reference voltage tracking under a wide range of load change scenarios. Within this framework, an integral sliding mode surface based SMC (ISMC) is designed to guarantee closed-loop robustness against the matched and mismatched disturbance components of the load uncertainty. Subsequently, a novel control structure comprises ISMC and PPIO is presented to overcome the design constraints and to mitigate the undesired transient response accompany the response of the closed-loop system based ISMC. Stability analysis has clearly demonstrated using linear matrix inequality (LMI) and Lyapunov approach. To illustrate the effectiveness of the proposal, a comparison between the closed-loop system responses of SMC, ISMC, and the combined ISMC and PPIO are presented in the simulation results. Keywords: Sliding mode control, Proportional-proportional-integral-observer (PPIO), DC-DC converter, Mismatched uncertainty, Robust control

© 2018 Elsevier Ltd An extension of the well-known delayed resonator concept is proposed with the objective to enhance its robustness in vibration suppression under guaranteeing stability of the overall set up. The novel resonator feedback is based on an acceleration measurements passing through a delay of polynomial distribution. The feedback design is formulated as an optimization problem over the parameter set formed by the polynomial coefficients and the gain of the delay free part. The first objective is to minimize the sensitivity of the resonator performance with respect to variations of the excitation frequency, i.e. to widen its frequency stop-band centered at the nominal excitation frequency. The second, equally significant objective is to guarantee that this does not lead to instability of the overall mechanical system coupled with the absorber and to ensure sufficient stability margin. The arising non-convex and non-smooth optimization problem is widely discussed and a penalty method is developed, where the unconstrained problem in every iteration step is solved using available software tools for optimization and spectral design of time delay systems. The proposed design technique is validated by simulations for two case study examples. ispartof: Journal of Sound and Vibration vol:443 pages:576-590 status: published