Search

Subject of Study. The paper discusses the concept of inkjet systems application, also known as pneumonics, for automatic hydrostatic gas bearing control. Inkjet systems have the advantages over traditional control systems in those problems where the speed of traditional mechanical, electrical or hydraulic servomotors is not enough. Control of the shaft position in gas bearing with forced gas supply into the gap between the shaft and the bearing is typical for this class of problems. In this case, control means the pressure changing or flow rate of gas supplied to the gap by at least one of three axes at a frequency higher than the nominal speed of the shaft. Thus, high speed of response is required from the system. The objective of this work is to design a discrete jet element, testing of its geometry and switching characteristics. Main Results. The discrete inkjet element for oil-free non-contact transmission working on the refrigerant was designed. Relay transition process was modeled in the inkjet element with the use of numerical methods. The switching time has reached 0.2-0.3 ms; this is one order less than the requirements of aircraft control systems, which typically operate at a frequency of about 200 Hz. It is shown that periodic oscillations with high frequency occur when the control signal is injected with insufficient level of pressure. Therefore, a separate design task is to determine the minimum pressure allowable in the control channel.

In this study, a small size, low power, simple and high contrast ratio (CR) structure was designed and simulated to use in photonic crystal‐based all‐optical logic gates. This structure can be used for both all‐optical logic NOT and XOR gates. The suggested structure is composed of three waveguides and a nano‐resonator. The nano‐resonator was designed by removing two dielectric rods. For use as an optical NOT logic gate, one of the input ports enters the control signal. In this case, the CR between logic levels '0' and '1' is 20.53 dB, which is higher than that of the provided gates based on structures published recently. The CR for the XOR gate is 19.95 dB. The response time to the input signal of the designed gate is 0.466 ps. The simplicity of the structure, small size, and high CR are the advantages of this structure compared to previously provided logic gates. The results have proven a superior prospect for the proposed structure to use in all optical integrated circuits. [ABSTRACT FROM AUTHOR]

Hepatitis C blood born virus is a major cause of liver disease that more than three per cent of people in the world is dealing with, and the spread of hepatitis C virus (HCV) infection in different populations is one of the most important issues in epidemiology. In the present study, a new intelligent controller is developed and tested to control the hepatitis C infection in the population which the authors refer to as an optimal adaptive neuro‐fuzzy controller. To design the controller, some data is required for training the employed adaptive neuro‐fuzzy inference system (ANFIS) which is selected by the genetic algorithm. Using this algorithm, the best control signal for each state condition is chosen in order to minimise an objective function. Then, the prepared data is utilised to build and train the Takagi–Sugeno fuzzy structure of the ANFIS and this structure is used as the controller. Simulation results show that there is a significant decrease in the number of acute‐infected individuals by employing the proposed control method in comparison with the case of no intervention. Moreover, the authors proposed method improves the value of the objective function by 19% compared with the ordinary optimal control methods used previously for HCV epidemic. [ABSTRACT FROM AUTHOR]

This paper provides theoretical preliminary results and develops a first methodology, that allows one to efficiently estimate the maximum time constant of a dynamic matrix of an uncertain system with rational multi‐affine structure with respect to parameters, and a second one to find a majorant system of a multi‐input multi‐output (MIMO) system with rational multi‐affine structure with respect to parameters. The developed methodologies are used to estimate the evolution of an uncertain linear time‐invariant (LTI) system with additional bounded nonlinearities and/or additional bounded input signals. Moreover, the above results are also used to design a robust controller for an uncertain MIMO system with unmeasurable states and subject to a rate‐bounded disturbance in order to track a rate‐bounded reference signal. The obtained theoretical results are illustrated by three examples. The first two examples deal with the analysis of a LTI system with bounded disturbances and measurement noise, and additional bounded and not bounded nonlinearities, respectively; in the second example a new control law with saturation is also designed. In the last example, a robust controller for an uncertain electro‐mechanical system with unmeasurable state is designed to track a rate‐bounded reference signal in the presence of a disturbance with bounded derivative. [ABSTRACT FROM AUTHOR]

Robust backstepping control of non‐linear systems with derivation orders (commensurate or non‐commensurate) lying at interval (0, 2) is proposed in this study. The stability and robustness properties are proved using a linearisation procedure in contrast to the classic recursive Lyapunov approach to backstepping. Vector, adaptive and robustness extensions are then developed to solve general tracking and stabilisation control problems. The adaptive extension is proved with a non‐Lyapunov approach based on inequalities on non‐negative fractional integrals. The mixed‐order nature enables to control integer order systems using fractional operators. Through simulations, it is shown that the performance of the controllers depends on their derivation orders. In particular, for transient behaviour and the root mean square value of the control signal, the fractional controllers proposed exhibit improved responses as compared with the integer ones. [ABSTRACT FROM AUTHOR]

dc/dc Power converters are increasingly used in vehicular power systems with their control systems re‐designed to overcome the challenges associated with the wide voltage and load variations and the non‐linear behaviour of constant power loads (CPLs). Within this context, this study investigates the implementation of a non‐linear time‐delay control (TDC) system in dc/dc power converters. This non‐linear controller compares the system response with the response of a reference model, and then generates a control signal which forces the system to follow the reference model. The TDC system is designed to tightly regulate the output voltage of a conventional dc/dc boost converter under input voltage and load variations. Furthermore, the stability of the TD controller following to the CPL variations is studied. To verify the effectiveness of TD controller, its performance is compared with an integral‐double‐lead controller using MATLAB software. [ABSTRACT FROM AUTHOR]

In this study, a novel event‐based model‐free adaptive control (MFAC) algorithm for discrete‐time non‐linear systems is presented. Different from the traditional MFAC scheme which calculates the control signal at fixed sampling instants, an event‐based sampling scheme is given to calculate the new control signal only when the input/output (I/O) data sufficiently changes. The event‐triggered MFAC can obviously reduce the computational load and network communication. The closed‐loop system is proven to be ultimately bounded by using the Lyapunov technique. Finally, the simulation examples indicate the effectiveness and applicability of the proposed event‐trigger model‐free adaptive control algorithm. [ABSTRACT FROM AUTHOR]

Research of power supplies for megahertz (MHz) class applications such as a semiconductor manufacturing apparatus, induction heater and wireless transfer is carried out. A liner amplifier is generally used for MHz class applications. The loss of the power devices on a liner amplifier is theoretically high. To reduce the loss, the class E and Φ2 inverters are proposed, and some of the resonant gate drive circuits (GDC) are utilised at those of the gate port. However, the control signal of the GDC becomes complicated due to the additional switches. Moreover, the switches in the GDC perform the hard‐switching, and the drive loss can thus be increased. In this study, a multi‐resonant gate drive circuit is proposed, and its design method is introduced. It can generate the trapezoidal wave gate‐to‐source voltage with the simple control signal, and zero voltage switching operation is achieved at the switches of the gate drive circuit. First, its operation is experimentally verified. Secondly, the drive loss is also compared with that of the conventional circuit. Furthermore, its operation with the class E inverter with a cascode GaN high‐electron‐mobility transistor (HEMT) is confirmed at the switching frequency 13.56 MHz. [ABSTRACT FROM AUTHOR]

A method for optimisation of proportional–integral–derivative controller parameters and measurement filter time constant is presented. The method differs from the traditional approach in that the controller and filter parameters are simultaneously optimised, as opposed to standard, sequential, design. Control performance is maximised through minimisation of the integrated absolute error caused by a unit step load disturbance. Robustness is achieved through H∞ constraints on sensitivity and complementary sensitivity. At the same time, noise attenuation is enforced by limiting either the H2 or H∞ norm of the transfer function from measurement noise to control signal. The use of exact gradients makes the synthesis method faster and more numerically robust than previously proposed alternatives. [ABSTRACT FROM AUTHOR]