Effect of multiplicity of stellar encounters and the diffusion coefficients in the uniform stellar medium: no classical divergence ?

Agekyan lambda-factor that accounts for the effect of multiple distant encounters with large impact factors is used for the first time to compute the diffusion coefficients in the velocity space of a stellar system. It is shown that in this case the cumulative effect - the total contribution of distant encounters to the change in the velocity of the test star - is finite, and the logarithmic divergence inherent to the classical description disappears, as also was earlier noted by Kandrup (1981). At the same time, the formulas for the diffusion coefficients, as before, contain the logarithm of the ratio of two independent scale factors that fully characterize the state of the stellar system: the average interparticle distance and the impact parameter of a close encounter. However, the physical meaning of this factor is no longer associated with the classical logarithmic divergence.Comment: 12 pages, 4 figures; Submitted to MNRA

Sliding mode control of quantum systems

This paper proposes a new robust control method for quantum systems with uncertainties involving sliding mode control (SMC). Sliding mode control is a widely used approach in classical control theory and industrial applications. We show that SMC is also a useful method for robust control of quantum systems. In this paper, we define two specific classes of sliding modes (i.e., eigenstates and state subspaces) and propose two novel methods combining unitary control and periodic projective measurements for the design of quantum sliding mode control systems. Two examples including a two-level system and a three-level system are presented to demonstrate the proposed SMC method. One of main features of the proposed method is that the designed control laws can guarantee desired control performance in the presence of uncertainties in the system Hamiltonian. This sliding mode control approach provides a useful control theoretic tool for robust quantum information processing with uncertainties.Comment: 18 pages, 4 figure

Организация жизненного цикла радиоэлектронных средств с учетом системы диагностики

Показано, що при організації життєвого циклу радіоелектронного засобу доцільно розглядати його як підсистему, яка входить до складу інтегрованої системи поруч з підсистемою, що виконує функції діагностуванняIt is shown, that at organization of life cycle of the radioelectronic device it is expedient to consider it as a subsystem, which is included into structure of the integrated system along-side with a subsystem carrying out function of diagnosticsПоказано, что при организации жизненного цикла радиоэлектронного устройства целесообразно рассматривать его как подсистему, которая входит в состав интегрированной системы наряду с подсистемой, выполняющей функции диагностик

Improving the vibration suppression capabilities of a magneto-rheological damper using hybrid active and semi-active control

This paper presents a new hybrid active & semi-active control method for vibration suppression in flexible structures. The method uses a combination of a semi-active device and an active control actuator situated elsewhere in the structure to suppress vibrations. The key novelty is to use the hybrid controller to enable the magneto-rheological damper to achieve a performance as close to a fully active device as possible. This is achieved by ensuring that the active actuator can assist the magneto-rheological damper in the regions where energy is required. In addition, the hybrid active & semi-active controller is designed to minimize the switching of the semi-active controller. The control framework used is the immersion and invariance control technique in combination with sliding mode control. A two degree-of-freedom system with lightly damped resonances is used as an example system. Both numerical and experimental results are generated for this system, and then compared as part of a validation study. The experimental system uses hardware-in-the-loop to simulate the effect of both the degrees-of-freedom. The results show that the concept is viable both numerically and experimentally, and improved vibration suppression results can be obtained for the magneto-rheological damper that approach the performance of an active device

On the Experimental Analysis of Integral Sliding Modes for Yaw Rate and Sideslip Control of an Electric Vehicle with Multiple Motors

With the advent of electric vehicles with multiple motors, the steady-state and transient cornering responses can be designed and implemented through the continuous torque control of the individual wheels, i.e., torque-vectoring or direct yaw moment control. The literature includes several papers on sliding mode control theory for torque-vectoring, but the experimental investigation is so far limited. More importantly, to the knowledge of the authors, the experimental comparison of direct yaw moment control based on sliding modes and typical controllers used for stability control in production vehicles is missing. This paper aims to reduce this gap by presenting and analyzing an integral sliding mode controller for concurrent yaw rate and sideslip control. A new driving mode, the Enhanced Sport mode, is proposed, inducing sustained high values of sideslip angle, which can be limited to a specified threshold. The system is experimentally assessed on a four-wheel-drive electric vehicle. The performance of the integral sliding mode controller is compared with that of a linear quadratic regulator during step steer tests. The results show that the integral sliding mode controller significantly enhances the tracking performance and yaw damping compared to the more conventional linear quadratic regulator based on an augmented singletrack vehicle model formulation. © 2018, The Korean Society of Automotive Engineers and Springer-Verlag GmbH Germany, part of Springer Natur

Theory of differential inclusions and its application in mechanics

The following chapter deals with systems of differential equations with discontinuous right-hand sides. The key question is how to define the solutions of such systems. The most adequate approach is to treat discontinuous systems as systems with multivalued right-hand sides (differential inclusions). In this work three well-known definitions of solution of discontinuous system are considered. We will demonstrate the difference between these definitions and their application to different mechanical problems. Mathematical models of drilling systems with discontinuous friction torque characteristics are considered. Here, opposite to classical Coulomb symmetric friction law, the friction torque characteristic is asymmetrical. Problem of sudden load change is studied. Analytical methods of investigation of systems with such asymmetrical friction based on the use of Lyapunov functions are demonstrated. The Watt governor and Chua system are considered to show different aspects of computer modeling of discontinuous systems

Діагностування радіоелектронної апаратури в інструментальному середовищі LabVIEW

The features of use of software LabVIEW are considered during the decision of tasks of the control and diagnostics of radioelectronic apparatus. The opportunity of the parallel decision of these tasks within the framework of development of a uniform complex is shown.Рассмотрены особенности использования программного продукта LabVIEW в процессе решения задач контроля и диагностики радиоэлектронных средств. Показана возможность решения этих задач в рамках разработки единого комплекса.Розглянуті особливості використання програмного продукту LabVIEW в процесі вирішення задач контролю та діагностування радіоелектронних засобів. Показана можливість паралельного вирішення цих задач в рамках розробки єдиного комплексу

Influence of Carboxylic Acids on Filterability and Quality Level of Synthetic Low Alkaline Calcium Sulfonate (Detergent-Dispersant Motor Oil Additive)

The study examined the conditions of synthetic low alkaline calcium sulfonate (SLCS) synthesis, which is added to motor oils as a detergent-dispersant additive. In particular, the effect of the introduction of carboxylic acids at the stage of SLCS synthesis on such characteristics of the additive as the observable filterability, volume filtration rate, volume fraction of sediment and kinematic viscosity was studied. For the obtained additive samples the average sizes of particles dispersed in the volume were measured using the dynamic light scattering method (DLS) and the basic physicochemical parameters were determined