Search results for " Computer vision"
showing 10 items of 352 documents
Finite-time stability and stabilisation for a class of nonlinear systems with time-varying delay
2014
This paper is concerned with the problems of finite-time stability FTS and finite-time stabilisation for a class of nonlinear systems with time-varying delay, which can be represented by Takagi–Sugeno fuzzy system. Some new delay-dependent FTS conditions are provided and applied to the design problem of finite-time fuzzy controllers. First, based on an integral inequality and a fuzzy Lyapunov–Krasovskii functional, a delay-dependent FTS criterion is proposed for open-loop fuzzy system by introducing some free fuzzy weighting matrices, which are less conservative than other existing ones. Then, the parallel distributed compensation controller is designed to ensure FTS of the time-delay fuzzy…
Power losses in power-split CVTs: A fast black-box approximate method
2018
Abstract This paper addresses the mechanical losses of planetary transmissions, with particular attention to power-split CVTs in their hybrid electric versions. It provides unified layout-independent analytical relationships, which can be used for both analysis, design and control purposes, and a simplified approach; the latter overcomes the necessity to segment the operating range of the power-split CVT in order to keep its loss model physically consistent. An example of application to a real hybrid electric PS-CVT is performed to show the simplicity, accuracy and generality of the proposed method.
A macroscale FEM-based approach for selective laser sintering of thermoplastics
2017
A numerical approach to model the selective laser sintering (SLS) of polypropylene is proposed. A 3D thermal model was developed and thus enables the prediction of the temperature fields and the extension of the sintered area in the powder bed taking into account the phase change during multiple laser passes. Powderâliquid, liquidâsolid and solidâliquid phase changes were modelled during the SLS and the subsequent cooling processes. Then, a 3D thermomechanically coupled model was set up based on the temperature results of the thermal model in order to predict the distortion of the produced parts after cooling down. Different pre-heating temperatures were considered, highlighting their…
A numerical model for Wire integrity prediction in Friction Stir Extrusion of magnesium alloys
2017
Abstract A numerical model for the prediction of the wire quality produced by the novel direct machining chip recycling technique known as Friction Stir Extrusion (FSE) is presented. Wire microstructure and wire integrity have been predicted by embedding in the code the equations enabling the calculation of the Zener-Hollomon parameter as well as the W parameter of the Pivnik-Plata solid bonding criterion. The proposed model, developed for the AZ31 magnesium alloy using the commercial simulation package DEFORM, is 3D Lagrangian, thermo-mechanically coupled with visco-plastic material behavior. The model was first validated against experimental temperature measurements and then used to predi…
In-process control strategies for friction stir welding of AZ31 sheets with non-uniform thickness
2017
Two different in-process control strategies were developed and compared with the aim to produce AZ31 magnesium alloy joints by friction stir welding on sheet blanks with a non-uniform thickness. To this purpose, sheets with dip or hump zones were welded by either changing the rotational speed or the tool plunging in order to keep constant the value of the vertical force occurring during the welding stage of the process. The influence of the main process parameters on the tool force, the micro- and macromechanical properties, and the joints microstructures in the dip and hump zones were analyzed. The results showed that using the rotational speed change-based approach, the hump zones are sub…
Vibration control strategy for large-scale structures with incomplete multi-actuator system and neighbouring state information
2016
The synthesis of optimal controllers for vibrational protection of large-scale structures with multiple actuation devices and partial state information is a challenging problem. In this study, the authors present a design strategy that allows computing this kind of controllers by using standard linear matrix inequality optimisation tools. To illustrate the main elements of the new approach, a five-story structure equipped with two interstory actuation devices and subjected to a seismic disturbance is considered. For this control setup, three different controllers are designed: an ideal state-feedback H 8 controller with full access to the complete state information and two static output-fee…
An insight into the electrical energy demand of friction stir welding processes: the role of process parameters, material and machine tool architectu…
2018
The manufacturing sector accounts for a high share of global electrical energy consumption and CO 2 emissions, and therefore, the environmental impact of production processes is being more and more investigated. An analysis of power and energy consumption in friction stir welding processes can contribute to the characterization of the process from a new point of view and also provide useful information about the environmental impact of the process. An in-depth analysis of electrical energy demand of friction stir welding is here proposed. Different machine tool architectures, including an industrial dedicated machine, have been used to weld aluminum and steel sheets under different process …
New delay-dependent stability of Markovian jump neutral stochastic systems with general unknown transition rates
2015
This paper investigates the delay-dependent stability problem for neutral Markovian jump systems with generally unknown transition rates GUTRs. In this neutral GUTR model, each transition rate is completely unknown or only its estimate value is known. Based on the study of expectations of the stochastic cross-terms containing the integral, a new stability criterion is derived in terms of linear matrix inequalities. In the mathematical derivation process, bounding stochastic cross-terms, model transformation and free-weighting matrix are not employed for less conservatism. Finally, an example is provided to demonstrate the effectiveness of the proposed results.
Dissipativity-Based Small-Gain Theorems for Stochastic Network Systems
2016
In this paper, some small-gain theorems are proposed for stochastic network systems which describe large-scale systems with interconnections, uncertainties and random disturbances. By the aid of conditional dissipativity and showing times of stochastic interval, small-gain conditions proposed for the deterministic case are extended to the stochastic case. When some design parameters are tunable in practice, we invaginate a simpler method to verify small-gain condition by selecting one subsystem as a monitor. Compared with the existing results, the existence-and-uniqueness of solution and ultimate uniform boundedness of input are removed from requirements of input-to-state stability and smal…
Potential Health Benefits of Olive Oil and Plant Polyphenols
2018
Beneficial effects of natural plant polyphenols on the human body have been evaluated in a number of scientific research projects. Bioactive polyphenols are natural compounds of various chemical structures. Their sources are mostly fruits, vegetables, nuts and seeds, roots, bark, leaves of different plants, herbs, whole grain products, processed foods (dark chocolate), as well as tea, coffee, and red wine. Polyphenols are believed to reduce morbidity and/or slow down the development of cardiovascular and neurodegenerative diseases as well as cancer. Biological activity of polyphenols is strongly related to their antioxidant properties. They tend to reduce the pool of reactive oxygen species…