Adaptive Backstepping Controller Design for Stochastic Jump Systems

In this technical note, we improve the results in a paper by Shi et al., in which problems of stochastic stability and sliding mode control for a class of linear continuous-time systems with stochastic jumps were considered. However, the system considered is switching stochastically between different subsystems, the dynamics of the jump system can not stay on each sliding surface of subsystems forever, therefore, it is difficult to determine whether the closed-loop system is stochastically stable. In this technical note, the backstepping techniques are adopted to overcome the problem in a paper by Shi et al.. The resulting closed-loop system is bounded in probability. It has been shown that the adaptive control problem for the Markovian jump systems is solvable if a set of coupled linear matrix inequalities (LMIs) have solutions. A numerical example is given to show the potential of the proposed techniques

Control of power electronic interfaces in distributed generation.

Renewable energy has gained popularity as an alternative resource for electric power generation. As such, Distributed Generation (DG) is expected to open new horizons to electric power generation. Most renewable energy sources cannot be connected to the load directly. Integration of the renewable energy sources with the load has brought new challenges in terms of the system’s stability, voltage regulation and power quality issues. For example, the output power, voltage and frequency of an example wind turbine depend on the wind speed, which fluctuate over time and cannot be forecasted accurately. At the same time, the nonlinearity of residential electrical load is steadily increasing with the growing use of devices with rectifiers at their front end. This nonlinearity of the load deviates both current and voltage waveforms in the distribution feeder from their sinusoidal shape, hence increasing the Total Harmonics Distortions (THD) and polluting the grid. Advances in Power Electronic Interfaces (PEI) have increased the viability of DG systems and enhanced controllability and power transfer capability. Power electronic converter as an interface between energy sources and the grid/load has a higher degree of controllability compared to electrical machine used as the generator. This controllability can be used to not only overcome the aforementioned shortfalls of integration of renewable energy with the grid/load but also to reduce THD and improve the power quality. As a consequence, design of a sophisticated controller that can take advantage of this controllability provided by PEIs to facilitate the integration of DG with the load and generate high quality power has become of great interest. In this study a set of nonlinear controllers and observers are proposed for the control of PEIs with different DG technologies. Lyapunov stability analysis, simulation and experimental results are used to validate the effectiveness of the proposed control solution in terms of tracking objective and meeting the THD requirements of IEEE 519 and EN 50160 standards for US and European power systems, respectively

Backstepping control of three-phase three-level four-leg shunt active power filter

In this paper, backstepping control for three-level four-leg shunt active power filter (SAPF) system is proposed. The adopted filtering topology requires both a three-dimensional space vector modulation (3DSVM) for controlling the three-level four-leg inverter as well as DC voltage and filter currents control. The regulation of the DC voltage and filter currents is accomplished by backstepping controllers. The voltage-balancing control of two split DC capacitors of the three-level four-leg SAPF is achieved using three-level three-dimensional space vector modulation equipped by a balancing strategy based on the effective use of the redundant switching states of the inverter voltage vectors. The simulation results show the effectiveness of the proposed filtering system in terms of the compensation of the harmonics and the zero sequence current and the operation at unity power factor.Keywords: shunt active power filter; three-dimensional space vector modulation; multilevel four-leg inverter; backstepping control; synchronous reference frame theory

Combined voltage oriented control and direct power control based on backstepping control for four-leg PWM rectifier under unbalanced conditions

The present paper proposes a combined voltage-oriented control and direct power control (VOC-DPC) method associated with the backstepping control technique for a three-phase four-wire grid-connected four-leg rectifier in the synchronous rotating frame without using phase locked loop (PLL) and Parks transformation under balanced and unbalanced load and grid conditions. This control method is proposed in order to remove the drawbacks of the conventional VOC based on the PLL technique .The proposed control method is able to enhance the control performance and dynamic responses of the system when considering slow dynamics and instability issues of the PLL in several cases and can decrease the computational burden due to the absence of PLL and Park transformation. In addition, the performance of the proposed VOC-DPC method is enhanced by using backstepping control (BSC) based on Lyabonov theory for both the input currents and DC-bus voltage loops. As a consequence, constant DC-bus voltage, unit power factor, sinusoidal input currents, and neutral current minimization can be accurately carried out under both DC-bus voltage and load variations. Furthermore, robustness against filter inductance variations can also be achieved. The effectiveness, superiority, and performance of the proposed control method for a four-leg rectifier based on BSC in the dq0-frame are validated by several processor-in-the-loop (PIL) co-simulation tests sing the STM32F407 discovery development board

Instrumentation and control of a target fixed-wing drone for launch and capture

This work was developed within the scope of the CAPTURE project, in which a collaborative network was intended to be built in which a quadcopter drone would help a fixed-wing drone perform landing and takeoff maneuvers. The study of small fixed-wing unmanned aerial vehicles (UAVs) were presented, as well as their attitude control, instrumentation, and trajectory tracking. One of the goals of this dissertation was to model a real vehicle, specifically the Easy Glider 4. All the work was developed based on this vehicle, for which it was necessary to use the XFLR software to obtain its aerodynamic response and thus obtain a more accurate model and, consequently, its control. The main challenges of this dissertation were related to obtaining the full dynamic model (with the aerodynamic coefficients included), the control techniques that would be used to deal with their nonlinearities, and their integration with a path following algorithm. Two types of attitude controllers were developed: a linear controller based on PI and a nonlinear controller based on the backstepping technique. An external loop was then added to make the UAV follow a specific path. Two different techniques were implemented: a path following algorithm that would make the vehicle follow a vector field around the intended trajectory and an adaptive algorithm capable of dealing with uncertainties in the environment, such as wind with unknown direction and intensity.Este trabalho é desenvolvido no âmbito do projecto CAPTURE , em que se pretende construir uma rede colaborativa em que um drone quadricóptero ajude um drone de asa fixa a realizar manobras de aterragem e descolagem. Será apresentado o estudo e modelação de pequenos veículos não tripulados de asa fixa (UAV), bem como o seu controlo de atitude, instrumentação e seguimento de trajetória. Um dos objectivos desta dissertação é a modelação de um veículo real, mais especificamente o Easy glider 4. Todo o trabalho será desenvolvido com base neste veículo, para isso, é necessário utilizar o software XFLR para obter sua resposta aerodinâmica e assim obter uma modelação mais precisa e, consequentemente, o seu controlo. Devido à complexidade da dinâmica do UAV, os principais desafios desta dissertação estão relacionados com a obtenção do modelo dinâmico, às técnicas de controlo que serão utilizadas para lidar com suas não linearidades e a sua integração com um algoritmo de path following. Serão desenvolvidos dois tipos de controladores de atitude: Um controlador linear baseado no PID e um controlador não linear baseado na técnica de backstepping. Um loop externo é então adicionado para que o UAV siga um determinado caminho. Serão implementadas duas ténicas diferentes: Um algoritmo de path following que fará o veículo seguir um campo vectorial em volta da trajetória pretendida e um algoritmo adaptativo capaz de lidar com incertezas do meio ambiente, tais como vento com direção e amplitude desconhecidas

Safety-Aware Longitudinal and Lateral Control of Autonomous Vehicles

Safety is undoubtedly the most critical design requirement regarding autonomous vehicle controllers. This research considers an autonomous vehicle to keep a desired distance from the leader vehicle, as well as stay centered within the lane. To achieve this, the lateral control problem and the combined longitudinal and lateral control problem were studied. Adaptive control laws were proposed with the aid of the backstepping technique and the barrier function technique. Simulation was done to verify the effectiveness of the proposed control laws

Globally Intelligent Adaptive Finite-/Fixed- Time Tracking Control for Strict-Feedback Nonlinear Systems via Composite Learning Approaches

This article focuses on the globally composite adaptive law-based intelligent finite-/fixed- time (FnT/FxT) tracking control issue for a family of uncertain strict-feedback nonlinear systems. First, intelligent approximators with new composite updating laws are developed to model uncertain nonlinear terms, which encompass prediction errors to enhance intelligent approximators' learning behaviors and fewer online learning parameters to diminish computational burden. Then, a novel smooth switching function coupled with robust controllers is designed to pull system states back when the transients are out of the approximators' active domain. After that, a modified FnT/FxT backstepping technique is constructed to render output to follow the reference trajectory, and an adaptive law is employed to alleviate the impact of external disturbances. It is theoretically confirmed that the proposed control strategies ensure globally FnT/FxT boundedness of all the closed-loop variables. Finally, the validity of theoretical results is testified via a simulation case.Comment: 6 pages,12 figure

Robust Adaptive Depth Control of Hybrid Underwater Glider in Vertical Plane

Hybrid underwater glider (HUG) is an advanced autonomous underwater vehicle with propellers capable of sustainable operations for many months. Under the underwater disturbances and parameter uncertainties, it is difficult that the HUG coordinates with the desired depth in a robust manner. In this study, a robust adaptive control algorithm for the HUG is proposed. In the descend and ascend periods, the pitch control is designed using backstepping technique and direct adaptive control. When the vehicle approaches the target depth, the surge speed control using adaptive control combined with the pitch control is used to keep the vehicle at the desired depth with a constant cruising speed in the presence of the disturbances. The stability of the proposed controller is verified by using the Lyapunov theorem. Finally, the computer simulation using the numerical method is conducted to show the effectiveness of the proposed controller for a hybrid underwater glider system