Iskanje po katalogu digitalne knjižnice

Ključne besede: asinhronski motorji, pretvorniški mostič, merilno vezje, merjenje faznih napetosti, fazne napetosti, dvojni preklopni integrator, induction machine, inverter bridge, speed sensrless control, measuring circuit, dual switched integrator
Objavljeno: 26.07.2007; Ogledov: 1513; Prenosov: 0

Opis: The main characteristic of an electrohydraulic pump control system is the presence of an electrical signal path. It requires at least one sensor for the controlled value (in this case pressure), delivering feedback to be compared with the electrical or numerical reference in the controller. The additonal expense penalty for the sensor and the valve is offset by the advantage of flexibility in the structure and parameters of the controller in comparison to hydraulic - mechanical concepts. Thus, the transfer response can be adapted to demands, even in the operational state. Sophisticated control structures can be implemented easily in the form of computer or microcontroller programs. The layout of electrohydraulic pressure control discussed in this study includes the presented loading unit. The variable pump is designed to act together with a proportional valve having two metering edges. It is less expensive compared to the design with a synchronizing cylinder and four metering edges. However, only inferior static and dynamic performance can be expected. Hydraulic energy is supplied to the control valve directly from the output port of the pump - with the advantage of simple assembly, as there are no additional components required - but with the drawback that there is influence on the control loop`s properties at every change in the disturbance value or reference. The aim of the study presented in this paper is a more efficient and simple concept compared to other known methods for pressure control of the above mentioned pump including the dynamics of the distribution network, and also the characteristics of the hydraulic load with special focus on improvements in steady state and dynamic behaviour.
Ključne besede: automatic control engineering, electrohydraulic systems, pressure control, self-adjusting proportional controller
Objavljeno: 31.05.2012; Ogledov: 1060; Prenosov: 51
Povezava na celotno besedilo

Opis: An adaptive control system is built which controlling the cutting force and maintaining constant roughness of the surface being milled by digital adaptation of cutting parameters. The paper discusses the use of combining the methods of neural networks, fuzzy logic and PSO evolutionary strategy (Particle Swarm Optimization) in modeling and adaptively controlling the process of end milling. An overall approach of hybrid modeling of cutting process (ANfis-system), used for working out the CNC milling simulator has been prepared. The basic control design is based on the control scheme (UNKS) consisting of two neural identificators of the process dynamics and primary regulator. Experiments have confirmed efficiency of the adaptive control system, which is reflected in improved surface quality and decreased tool wear.
Ključne besede: end milling, adaptive force control, artificial intelligence, optimisation, adaptive control systems
Objavljeno: 31.05.2012; Ogledov: 896; Prenosov: 19
Povezava na celotno besedilo

Opis: Conventional methods, e.g. destructive and non-destructive testing methods, are expensive and time-consuming; therefore, possibilities of online and automated quality control of a welding process during welding as such are investigated. The paper deals with the possibilities of application of fuzzy logic to the analysis of weld quality, particularly assessment of the weld surface condition by means of measurable electric signals emitted during welding. A simple fuzzy inference system was realised which could relatively efficiently assess the weld quality on the basis of time variations of the welding voltage and short-circuit time in a certain time window.
Ključne besede: fuzzy systems, fuzzy logic, gas metal arc welding, GMAW, quality monitoring, statistical analysis, quality control, weld quality
Objavljeno: 31.05.2012; Ogledov: 989; Prenosov: 62
Povezava na celotno besedilo

Opis: Accurate position tracking control of a linear belt-driven servomechanism can cause vibrations in the drive response due to compliance and elasticity introduced by force transmission through the belt. This paper proposes a new control algorithm that has been designed by Sliding Mode Control theory. Though it has been proved to assure robust and vibration-free operation, position error peaks still appear at velocity reversals due to nonlinear friction phenomenon. Thus, the control scheme has been extended by asymptotic disturbance observer. The experiments presented in the paper show improved position tracking error response while maintaining vibration suppression.
Ključne besede: motion control, disturbance observer, sliding mode control, timing-belt drive, vibration suppression
Objavljeno: 31.05.2012; Ogledov: 1137; Prenosov: 61
Povezava na celotno besedilo