Modelling of Elastic Gearboxes Using a Generalized Gear Contact Model

The object of this paper is to present an universal model that describes the gear contact between two gears in a planar environment. The model includes elastic effects between the gear wheels. Using this model it is possible to create arbitrary spur gear connections as well as all kinds of epicyclic gearing configurations by supplying the proper external constraints. The presented model is implementated in the Modelica language and Dymola is used for the simulations

Effects of Event-Free Noise Signals on Continuous-Time Simulation Performance

Generating stochastic input signals such as noise in physical systems is traditionally implemented using discrete random number generators based on discrete time-events. Within the Modelica community, random number generators free of time-events have recently been proposed in order to increase the performance of system simulations. However, the impact of such signals on commonly used solvers, such as DASSL or Radau IIA, is still under discussion. In order to provide better understanding for modeling practitioners, we examine the influence of event-free noise models on simulation performance. To this end, we conduct practical simulation experiments with systems of three sizes, two solvers, and different parameters. Results indicate that step-size control can handle event-free noise generators well and that they outperform sampled generators. The findings can be related to other time-dependent system inputs

De aangezichtsschedel bij kinderen van 7 tot 11 jaar:Een longitudinaal röntgencefalometrisch onderzoek

Het doel van dit proefschrift is een bijdrage te leveren tot de kennis omtrent de aangezichtsschedel van het kind op bepaalde leeftijden en een inzicht te verschaffen in de veranderingen, die hieraan tijdens een bepaalde leeftijdsperiode - in casu van 7 tot 11 jaar - plaatsvinden. ... Zie: Samenvattin

Linear EMA HM Using Oil Detection

Current health monitoring descriptions often base on assumptions on how a degraded component behaves. Bearing and gear frequencies quite often play a role in this classic health monitoring. Even with a perfect monitoring, a positive result can only be given as soon as damage has occurred. The presented method detects the availability of oil in the actuator and can therefore predict upcoming damages that are caused by a lack of oil

Implementation of a Modelica library for simulation of electromechanical actuators for aircraft and helicopters

The goal of the A2015 library presented in this paper is to develop a Modelica based, tool-independent standard for electromechanical actuators (EMA). This will contribute to the establishment of a “common language” throughout the development of EMAs for aircraft and helicopters and through the supply chain. All stages of the design and validation process (conceptual design, specification, development and validation) are covered. The modeling approach addresses specific aspects of the EMA design process not covered by existing tools. The library scope, engineering need and implementation are described. Modeling of selected EMA components is discussed in more detail. An application example of the library is given (linear actuator, A320 aileron

General fault triggering architecture to trigger model faults in Modelica using a standardized blockset

The implementation of faults in Modelica is currently not standardized, which leads to many non-compatible implementations. To support the standardization of fault implementations, a new standard for fault implementation and triggering is proposed. The proposed standard can handle parameter faults as well as variable faults during a time simulation to cover all common fault possibilities. Using instance modifiers as well as an inner-outer broadcasting method, the faults can be triggered in a central block. Furthermore, care was taken so that the simulation of the models in a fault-free condition can be guaranteed. A library using the proposed standard was developed. In this library, the fault implementation as well as the triggering of these faults was modeled with the end user in mind. An example implementation is presented which shows the capabilities of the library

Modeling of geared positioning systems: An object-oriented gear contact model with validation

In aerospace positioning actuators, gear efficiencies of 85% as well as breakout forces as high as 50% of the stall load of the actuator are observed at very low temperature conditions. Due to the low efficiency and high loading, stiction in these actuators is common which can lead to limit cycles or problems with controlling the actuators. To be able to correctly predict and assess these effects using simulations, a complete actuator, including motor, inverter, load and controller is needed. This article presents an object based, numerically efficient gear contact in a planar environment with user-defined friction- and stiffness laws. The emphasis of the modeling is not a fully detailed contact model, but the description of a gear contact model which can be used for system simulations like complete aircraft electro-mechanical actuators including control surfaces. The presented model is suitable for complex gearing configurations (e.g. compound planetary gears). This is enabled by breaking down the transmission into the basic gear contacts. By adding masses and constraints from an existing component library, a complete transmission can be modeled. The generated model can be used for standalone simulations or can be used in multi-domain simulations like actuator modeling, in order to analyze the complete actuator model including parts such as drives, controllers and mechanical systems. The presented models have been validated using a gear test rig for a single stage spur gear

Advanced sensor fault detection and isolation for electro-mechanical flight actuators

Moving towards the more electric aircraft to be able to replace mechanic, hydraulic and pneumatic components of an aircraft, the aircraft industry calls for new technologies able to support this trend. One of these technologies is the development of advanced electro-mechanical actuators for aircraft control surfaces. Step by step hydraulic actuators are replaced by their electro-mechanical alternatives featuring weight and cost savings. As hydraulic actuators are used for decades by the aircraft industry, they are augmented with advanced signal and model based fault detection and diagnosis systems able to monitor the actuator and initiate adaptations in case of failures. For electro-mechanical actuators such advanced monitoring systems are still in the initial stages. In this paper, fault detection and isolation filters are designed by applying advanced residual filter synthesis algorithms to be able to monitor the sensor of electro-mechanical actuators. This paves the way for possible adaptations in electro-mechanical actuator systems in case of failures

Modelling of Torque-Vectoring Drives for Electric Vehicles: a Case Study

This paper shows the implementation of a gear model with losses, nonlinear elasticity and forcing errors in the Modelica language utilizing concept of replaceable functions. A case study about a torque-vectoring drive in a simplified vehicle model is carried out. Using the proposed gear model, the total vehicle model is analyzed in several detail stages reaching from rigid-perfect to a model using a nonlinear loss and nonlinear tooth stiffness