Simon Baev

Unity Power Factor Control in Three-Phase AC/DC Boost Converter Using Sliding Modes

A problem of power factor correction for a class of three-phase boost ac/dc power converters is addressed in this paper. A full-bridge hardware topology is studied and used to address the basics of the efficient power conversion with high values of power factor. The sliding mode control drives the output voltage to the desired dc level in the presence of external disturbances and internal parameter uncertainties while providing a value of power factor that is close to unity (greater than 97%). Sliding-mode observers are employed to estimate variation in load and phase resistances-subject of real-time adjustment in the control law. Multirate numerical simulation illustrates the efficiency of the proposed methodology and proves its ability to be implemented in digital form.

HOSM Observer for a Class of Non-Minimum Phase Causal Nonlinear MIMO Systems

A higher order sliding mode observer is proposed for asymptotic identification of the full state vector and the vector of unknown inputs for MIMO nonlinear causal systems with unstable internal dynamics. The problem is addressed via consistent application of exact higher order sliding mode differentiators in conjunction with the method of stable system center. A numerical example illustrates the performance of the proposed algorithm.

Output feedback tracking in causal nonminimum-phase nonlinear systems using HOSM techniques

Asymptotic output feedback tracking in a class of causal nonminimum phase uncertain nonlinear systems is addressed via sliding mode techniques. Local asymptotic stability of the output tracking error dynamics along with boundedness of the internal state are proven. Unstable internal states are estimated via proposed multistage observer. Integral sliding mode control is proposed for robust stabilization of the tracking errors and direct estimation/compensation of the unknown inputs, which is treated as an external disturbance. A numerical example illustrates the efficiency of the developed output feedback tracking approach.

Sliding mode parameter identification of systems with measurement noise

Identification problem in a nonlinear system with constant coefficients is addressed via traditional and high-order sliding mode parameter observer based on the least-squares continuous-time technique. Measurement noise effects on the parameter estimation algorithm are analyzed. The effectiveness of the proposed method is verified via the parameter estimation in a second-order system with noisy measurement.

HOSM observer for a class of non-minimum phase causal nonlinear MIMO systems

Abstract A higher order sliding mode observer is proposed for asymptotic identification of the full state vector and the vector of unknown inputs for MIMO nonlinear causal systems with unstable internal dynamics. The problem is addressed via consistent application of exact higher order sliding mode (HOSM) differentiators in conjunction with the method of stable system center (SSC). A numerical example illustrates the performance of the proposed algorithm.

Active Compensation of Low Frequency Flexible Modes of Crew Launch Vehicle Using Sliding Mode Observers

The problem of controlling the motion of crew launch vehicle (CLV) in the presence of significant bending is considered. The idea of estimating with later compensation of bending modes is proposed. The sliding mode observers are designed for estimating the first and the second bending modes. Traditional PID controller for CLV attitude control is augmented by the sliding mode based bending mode observer. Also, the observer is used to clean up the corrupted measurement data. Pitch plane attitude control of the CLV ”Ares I” is considered. The corresponding mathematical model, the file named CLV_State_Space_9_3_06.doc is provided by NASA for the case study. The numerical simulation demonstrates a high ecacy of the traditional PID controller augmented by the sliding mode based bending mode observer. The attitude control of the ”Ares I” with the bending mode eects achieved a tracking performance that is very close to the one of the rigid body CLV.

Flexible Modes Control Using Sliding Mode Observers: Application to Ares I

The launch vehicle dynamics affected by bending and sloshing modes are considered. Attitude measurement data that are corrupted by flexible modes could yield instability of the vehicle dynamics. Flexible body and sloshing modes are reconstructed by sliding mode observers. The resultant estimates are used to remove the undesirable dynamics from the measurements, and the direct effects of sloshing and bending modes on the launch vehicle are compensated by means of a controller that is designed without taking the bending and sloshing modes into account. A linearized mathematical model of Ares I launch vehicle was derived based on FRACTAL, a linear model developed by NASA/MSFC. The compensated vehicle dynamics with a simple PID controller were studied for the launch vehicle model that included two bending modes, two slosh modes and actuator dynamics. A simulation study demonstrated stable and accurate performance of the flight control system with the augmented simple PID controller without the use of traditional linear bending filters.

Output Tracking and Observation in Nonminimum Phase Systems via Classical and Higher Order Sliding Modes

The problem of causal output tracking and observation in non-minimum phase nonlinear systems is studied. The extended method of Stable System Center (ESSC) is used in two-fold manner: i) to generate reference profile for unstable internal states; ii) to estimate states of unstable internal dynamics. Two applications of the proposed technique are considered for illustration purposes: output voltage tracking in a nonminimum phase DC/DC electric power converter and output tracking in SISO systems with time-delayed output feedback. A variety of traditional and higher-order sliding mode (HOSM) control and observation methods is employed in the majority of algorithms. Most of the theoretical results are covered by numerical simulations.

Reconfiguration of a mobile communication network via Higher-Order Sliding Mode control

The mobile communication network studied here consists of a group of agents which move in response to external commands to perform a data-gathering task. As these agents move, connectivity of their communication network may be disrupted, preventing data transmission. Higher-Order Sliding Mode (HOSM) observers are used to reconstruct the external commands, from which future positions of the agents, as well as possible sites of connectivity disruption, are predicted on a certain time window. Controlled agents are introduced that are driven along trajectories to these sites by means of HOSM controllers, which cancel out effects of unknown bounded external disturbances; collisions with other agents along these trajectories are avoided. An intact communication network is thus constantly reconfigured by the movement of controlled agents. A case study demonstrates the proposed algorithm.

Express Decision – Mobile Application for Quick Decisions: An Overview of Implementations

Express Decision (ED), a mobile software application, was developed in order to offer decision-making support in situations of uncertainty. The current work presents a description of the Preference Evaluation Process (PEP), which was created based on Systemic-Structural Activity Theory with the goal of conducting thorough analysis of self-regulation processes that determine the selection of the most preferable alternative, a process in which ED plays a key role. PEP, along with ED, helps to divide a problem into sub-problems, determine the preference for solving each of them, and, as a result, determine the preference of the best alternative for execution. PEP, when splitting problems into sub-problems, implements a divide-and-concur algorithm, in which ED serves as a template (frame) for determining the terminal (ad hoc) level of sub-problems under consideration. The current work demonstrates the implementation of PEP with ED with the use of a real-life example based on solving the problem of selecting the best type of car insurance policy. For this particular problem, decision- and goal-motivation trees are constructed.