Uncertainty In Design Process Research Articles

The cascade backstepping controller design for supercavitating vehicle based on RBFNN observer

Aiming at the model uncertainty in design process of longitudinal motion control system of supercavitating vehicle, a backstepping controller is designed by combining with Radial Basis Function neural network (RBFNN). Considering that the environment of the supercavitating vehicle is complex during its traversal, it is not possible to measure all states directly. The calculation of planing force with nonlinear characteristics is related to vertical velocity, therefore, the accuracy of vertical velocity has impact on the value of planing force directly. A state observer is designed to estimate vertical velocity. In this paper, based on the backstepping method, the uncertain part of matrix coefficient in cascade control model of supercavitating vehicle is approximated by RBFNN. The output of the observer approximates the state variables, then, a depth tracking control law of the vehicle is obtained according to the observed values and the weight of neural network is calculated by Lyapunov function. Finally, it is proved that the control law can ensure the uniform ultimate boundedness of the closed-loop system.

Experiences using EN 17037 in evaluation of daylighting of dwellings in Slovakia

The daylighting of indoor spaces depends particularly on the urban and architectural parameters of the building environment. The new standard EN 17037, Daylight in Buildings, has brought several changes and uncertainties in design process of daylighting for buildings. The submitted paper is focused on analysis of the philosophy of the new standard criteria in relation to the daylighting of dwellings along with the criteria that have been used in Central European countries for decades. EN 17037 does not distinguish between differences in the functional use of indoor spaces in terms of daylight provision. The new European standard requires at the half of subjectively determined reference plane to achieve the same value of illumination for half of daylight hours per year for any occupied room. The EN standard does not sufficiently respect the specifics of daylighting of dwellings.

Wind shear effect on aerodynamic performance and energy production of horizontal axis wind turbines with developing blade element momentum theory

Nowadays, the optimal use of energy is one of the most important things in energy engineering. Disadvantages of fossil fuels make renewable and cleaner energy sources more widely used. Wind energy is a type of clean energies that will help humanity transition to a sustainable future. The power of wind turbine depends on many parameters such as wind profile and blade geometry. In most studies, wind speed is generally considered to be constant and uniform along the rotor blades. But in fact the nature of wind has irregularities in space and time. Moreover, wind shear leads to non-uniformity in wind vertical profile. Having a good understanding of these kinds of spatial and transient irregularities and also their influence on wind turbine performance reduce uncertainty in design process. In the present study the blade has been designed by blade element momentum (BEM) theory and aerodynamic coefficients have been calculated along the blade length. The effects of wind shear have been studied on the designed blade. Power law has been used to model wind shear. By merging this function with BEM theory, its effect can be calculated along the blade length. Results show that wind shear has little impact on aerodynamic coefficients near the root region. Most of changes occur at 0.2 to 0.8 of the blade length. Furthermore, existence of shear in wind profile regarding the turbine designed for uniform inflow, reduces the kinetic energy flux, ability to extract the available potential and power generation.

Conceptual Remote Sensing Satellite Design Optimization under uncertainty

This paper focuses upon the development of an efficient method for the conceptual design optimization of Remote Sensing Satellites (RSS) under uncertainty. There are many acceptable optimal solutions for implementation of satellite subsystems in a space system mission. Every solution should be assessed based on the different criteria such as cost, mass, reliability and payload resolution. In the present paper satellite mass and imaging payload resolution were considered as system level objective functions to obtain the system optimal solution during the conceptual design phase. Furthermore, two Multidisciplinary Design Optimization (MDO) frameworks; Multidisciplinary Design Feasible (MDF) and distributed Collaborative Optimization (CO) were applied to the multi-objective design optimization problem under uncertainty. Also, various uncertainties involving environment, operation, geometry, subsystems, etc. were considered in the Reliability Based Multidisciplinary Design Optimization (RBMDO) frameworks. In the present study, MDF, CO, Reliability Based Multi-disciplinary Design Feasible (RB-MDF) and Reliability Based Collaborative Optimization (RB-CO) frameworks were evaluated and compared. The methodology was based on the utilization of Monte Carlo simulation method for accounting uncertainties in design process and applying genetic algorithms and sequential quadratic programming to system level and discipline level optimizers. Results obtained in this study, have shown that the introduced method provides an effective way of accounting uncertainty in a complex space system design such as the conceptual design optimization of a spacecraft.

Management of product design complexity due to epistemic uncertainty via energy flow modelling based on CPM

Abstract Integrated product design and development in today's highly competitive and economically challenging world is a complex process depending upon client requirements. One of the main factors contributing to the complexity of process is uncertainty due to lack of system knowledge, known as epistemic uncertainty. This paper proposes a systematic approach to reduce epistemic uncertainty in design process in early stages of design. The approach is based on “CTOC” and “CPM” to decompose the system behaviour and determine the relationships between function and structure of a system. An application of the approach is demonstrated through an industrial case study.