Search results for "Application"
showing 10 items of 5559 documents
RMS Based Health Indicators for Remaining Useful Lifetime Estimation of Bearings
2022
Estimating the remaining useful life (RUL) of bearings from healthy to faulty is important for predictive maintenance. The bearing fault severity can be estimated based on the energy or root mean square (RMS) of vibration signals, and a stopping criterion can be set based on a threshold given by an ISO standard. However, the vibration RMS is often not monotonically increasing with damage, which renders a challenge for predicting the RUL. This study proposes a novel method for splitting the vibration signal into multiple frequency bands before RMS calculations to generate multiple health indicators. Monotonic health indicators are identified using the Spearman coefficient, and the RUL is aft…
Experimental System Identification and Black Box Modeling of Hydraulic Directional Control Valve
2015
Directional control valves play a large role in most hydraulic systems. When modeling the hydraulic systems, it is important that both the steady state and dynamic characteristics of the valves are modeled correctly to reproduce the dynamic characteristics of the entire system. In this paper, a proportional valve (Brevini HPV 41) is investigated to identify its dynamic and steady state characteristics. The steady state characteristics are identified by experimental flow curves. The dynamics are determined through frequency response analysis and identified using several transfer functions. The paper also presents a simulation model of the valve describing both steady state and dynamic charac…
Analysis of Offshore Knuckle Boom Crane - Part Two: Motion Control
2013
In this paper design of electro-hydraulic motion control systems for offshore knuckle boom cranes is discussed. The influence of the control valve bandwidth along with the ramp time for the control signal are investigated both analytically with simplified system models and numerically with an experimentally verified crane model. The results of both types of investigations are related to general design rules for selection of control valves and ramp times and the relevance of these design rules is discussed. Generally, they are useful but may be too conservative for offshore knuckle boom cranes. However, as demonstrated in the paper, the only proper way to determine this is to evaluate the mo…
Robust fault tolerant tracking controller design for a VTOL aircraft
2013
This paper deals with the fault tolerant control (FTC) design for a Vertical Takeoff and Landing (VTOL) aircraft subject to external disturbances and actuator faults. The aim is to synthesize a fault tolerant controller ensuring trajectory tracking for the nonlinear uncertain system represented by a Takagi-Sugeno (T-S) model. In order to design the FTC law, a proportional integral observer (PIO) is adopted which estimate both of the faults and the faulty system states. Based on the Lyapunov theory and ℓ2 optimization, the trajectory tracking performance and the stability of the closed loop system are analyzed. Sufficient conditions are obtained in terms of linear matrix inequalities (LMI). …
Robust fault-tolerant H∞ control of active suspension systems with finite-frequency constraint
2015
Abstract In this paper, the robust fault-tolerant (FT) H ∞ control problem of active suspension systems with finite-frequency constraint is investigated. A full-car model is employed in the controller design such that the heave, pitch and roll motions can be simultaneously controlled. Both the actuator faults and external disturbances are considered in the controller synthesis. As the human body is more sensitive to the vertical vibration in 4–8 Hz, robust H ∞ control with this finite-frequency constraint is designed. Other performances such as suspension deflection and actuator saturation are also considered. As some of the states such as the sprung mass pitch and roll angles are hard to m…
Using CFD to derive reduced order models for heat transfer in particle curtains
2015
3–D Eulerian–Eulerian CFD is used to simulate convective heat transfer in free falling particle curtains. Total heat loss for curtaining particles is compared to heat loss for isolated single particles. Spherical silica particles with density of 2,634 kg/m³ at 400 K (200 µm, 400 µm and 600 µm) flow at approximately 0.041 kg/s to 0.2 kg/s through a narrow slot in a rectangular box (0.45 m × 0.9 m × 0.225 m) filled with ambient air. The slot sizes through which the particles enter the rectangular box were 10 to 80 mm wide. Modifying the slot size at 0.041 kg/s for 400 µm particles can lead to 13% increases in rates of convective heat transfer per unit mass. A reduced order model was developed…
Modelling of EM glass convection
2008
PurposeTo develop the mathematical model, which allows predicting the temperature and flow distribution of an opaque glass melt with the temperature‐dependent properties in case it is generated by electromagnetic and thermal convection. Analysis has been done for geometry of the model crucible with the immersed rod electrodes. Numerical analysis is used as a tool for finding out the parameters of the system, which allow getting desiderated homogeneity of temperature field by EM action.Design/methodology/approachANSYS CFX software is implemented for coupling of EM, thermal and HD processes in the modelled system. Usability of non‐inductive approximation is shown using a full harmonic analysi…
Constrained control of a nonlinear two point boundary value problem, I
1994
In this paper we consider an optimal control problem for a nonlinear second order ordinary differential equation with integral constraints. A necessary optimality condition in form of the Pontryagin minimum principle is derived. The proof is based on McShane-variations of the optimal control, a thorough study of their behaviour in dependence of some denning parameters, a generalized Green formula for second order ordinary differential equations with measurable coefficients and certain tools of convex analysis.
Convex Duality in Stochastic Optimization and Mathematical Finance
2011
This paper proposes a general duality framework for the problem of minimizing a convex integral functional over a space of stochastic processes adapted to a given filtration. The framework unifies many well-known duality frameworks from operations research and mathematical finance. The unification allows the extension of some useful techniques from these two fields to a much wider class of problems. In particular, combining certain finite-dimensional techniques from convex analysis with measure theoretic techniques from mathematical finance, we are able to close the duality gap in some situations where traditional topological arguments fail.
Enclosure method for the p-Laplace equation
2014
We study the enclosure method for the p-Calder\'on problem, which is a nonlinear generalization of the inverse conductivity problem due to Calder\'on that involves the p-Laplace equation. The method allows one to reconstruct the convex hull of an inclusion in the nonlinear model by using exponentially growing solutions introduced by Wolff. We justify this method for the penetrable obstacle case, where the inclusion is modelled as a jump in the conductivity. The result is based on a monotonicity inequality and the properties of the Wolff solutions.