Evgeny I. Veremey

Mathematical methods of plasma vertical stabilization in modern tokamaks

The paper presents the application of modern computational methods for tokamak plasma control system analysis. Several different approaches for feedback controller synthesis are described. General positions of the modern robust analysis theory are briefly formulated. The technique of robust features comparative analysis for feedback controllers is presented. The application of these computational methods is illustrated by the example of the MAST tokamak plasma vertical feedback control system.

Dynamical Correction of Positioning Control Laws

Abstract Modern dynamic positioning systems are widely used now to support marine operations of various types. Correspondent control laws include nonlinear asymptotic observers to restore deficient information about the unmeasured velocities of the vessel. Using obtained estimations, it is possible to stabilize closed loop system and to provide its desirable dynamical features. The complexity of this problem is determined by the presence of an extensive population of certain dynamical conditions, requirements and restrictions that essentially hampers the using of traditional synthesis methods. In this connection the mentioned problem can be decoupled into particular separated problems on the base of a special unified multipurpose structure of control law, which includes dynamical corrector to provide desirable features for the DP vessel motion under influence of external disturbances.

H∞-Approach to Wave Disturbance Filtering for Marine Autopilots

Abstract The subject of the paper is consideration of the analytical synthesis problem for the marine vehicles autopilots design. The complexity of this problem is determined by the presence of an extensive population of certain dynamical conditions, requirements and restrictions that essentially hampers the using of synthesis methods in framework of classical control theory. In this connection the mentioned problem can be decoupled into particular optimization problems on the base of a special unified multipurpose structure of control law. In particular, this structure includes dynamical filter to provide desirable features for the vehicle motion under sea wave actions. A specialized method of the filter design is proposed on the base of modern H ∞ -optimization theory.

Program for scientific and educational investigations on the base of small spherical tokamak Gutta

In Saint-Petersburg state University the modernization of spherical Gutta tokamak is carried out. The aim of the program is to build the research device to study plasma position, shape and current control problems in the tokamak, as well as to assist the scientific and educational programs on various plasma physics problems. Such feature of this device as a relatively small thickness of the vacuum vessel wall made as momentless shell allows changes in the magnetic field in plasma region, to measure the plasma parameters with a minimum delay using electromagnetic diagnostics and changes in toroidal field as necessary.

Analysis and Synthesis of Plasma Stabilization Systems in Tokamaks

Abstract The central problem to be investigated in this paper is plasma control in the toroidal magnetic chamber. It is well known that plasma as an object of control is a mobile non-stable dynamic system with extremely high values of physical parameters, temperature as high as millions centigrade, first of all. This fact rises very high the requirement for electromagnetic capture system control accuracy. The special attention is paid to the stabilization of the plasma to chamber walls gap in some fixed control points. Mathematical methods of stabilizing control design based on modem optimization theory are proposed.

The Experiments of the small Spherical Tokamak Gutta

GUTTA is a small spherical tokamak (R = 16cm, a = 8cm, Ip = 150kA) operating at the St. Petersburg State University since 2004 in the scope of the IAEA CRP “Joint Research using Small Tokamaks”. Main scientific activities on GUTTA include development of new and improvement of existing mathematical models of plasma control, relevant for application on large tokamaks and ITER and verification of them on GUTTA; studies on the ECRH/EBW assisted breakdown and non‐solenoid plasma formation in low aspect ratio tokamak; development of diagnostics; training and education of students.In this paper design properties of Gutta will be presented. Regimes of operation of the tokamak and plasma shape parameters are described and first results of the plasma formation and start‐up studied will be discussed.

Dynamic Positioning Based on Nonlinear MPC

Abstract This paper is devoted to nonlinear model predictive control (MPC) application for dynamic positioning (DP) problem. The MPC approach has prominent features among other nonlinear control schemes. They include the explicit way for using nonlinear models and taking into account constraints imposed on controlled and manipulated variables while provide optimal performance with respect to a given cost functional. Dynamic positioning is a nonlinear control process with three-dimensional input and output, constraints and external disturbances that allows to state that MPC strategy is a quite suitable approach to be used here. In this paper MPC based control algorithm for DP problem is proposed. This algorithm includes two stages: the nonlinear stage, where nonlinear predictive model is used, and the linear stage, which is switch on in the vicinity of desired position. The algorithm provides offset-free performance. The effectiveness of the MPC approach is demonstrated by the simulation study examples.

Robust features analysis for the MAST plasma vertical feedback control system

The paper covers some questions related with the problem of plasma stability in vertical direction in the MAST tokamak. General positions of the modern /spl mu/-analysis theory are briefly formulated. The technique of robust features comparative analysis for feedback controllers is presented. Along with PD controller designed earlier, the optimal LQG controllers are synthesized and used for comparison on their dynamical and robust features.

Modal Parametric Optimization of Control Laws with Special Structure

The paper is devoted to particular cases of optimization problems for dynamical systems with scalar control and external disturbance. The aim is to find optimal parameters of an output feedback controller having initially given structure. An admissible set of controllers is determined by the requirement to place the poles of linear closed-loop connection inside desirable regions on the complex left-half plane. Numerical algorithm is proposed to solve the posed problem using special multi-purposes structure of the controller. To show practical applicability and effectiveness of the proposed approach and the benefits of developed methods, the illustrative example of marine autopilot design is presented.

Transoceanic routes optimization using dynamic properties of ship and weather conditions

This paper is devoted to the problem of optimal weather routing for transoceanic ship voyages. The goal of optimization is to reduce travel time and fuel consumptions. The optimal route is searched on the admissible set, which comprises routes satisfying all of the imposed static and dynamic constraints. The static constraints are represented mostly by coastal lines and shallow waters. The dynamic constraints are time-varying alarm zones restricted for ship motion due to dangerous weather conditions. The proposed route optimization algorithm uses long-term weather forecast for a sailing region and a mathematical model of ship motion. The key feature of algorithm is the three-dimensional representation of the route, which allows transforming initial finite-dimensional optimization problem to the problem of path finding on special graph.