659 research outputs found
A reduced Iwan model that includes pinning for bolted joint mechanics
No full textBolted joints are prevalent in most assembled structures; however, predictive models for their behavior do not exist. Calibrated models, such as the Iwan model, are able to predict the response of a jointed structure over a range of excitations once calibrated at a nominal load. The Iwan model, though, is not widely adopted due to the high computational expense of implementation. To address this, an analytical solution of the Iwan model is derived under the hypothesis that for an arbitrary load reversal, there is a new distribution of dry friction elements, which are now stuck, that approximately resemble a scaled version of the original distribution of dry friction elements. The dry friction elements internal to the Iwan model do not have a uniform set of parameters and are described by a distribution of parameters, i.e., which internal dry friction elements are stuck or slipping at a given load, that ultimately governs the behavior of the joint as it transitions from microslip to macroslip. This hypothesis allows the model to require no information from previous loading cycles. Additionally, the model is extended to include the pinning behavior inherent in a bolted joint. Modifications of the resulting framework are discussed to highlight how the constitutive model for friction can be changed (in the case of an Iwan–Stribeck formulation) or how the distribution of dry friction elements can be changed (as is the case for the Iwan plasticity model). The reduced Iwan plus pinning model is then applied to the Brake–Reuß beam in order to discuss methods to deduce model parameters from experimental data
Brake squeal: A fundamental study on bicycle brake squeal
No full textBrake squeal is a well know problem in the bicycle industry. Most of the time brake squeal occurs due to wear of the brake components and/or in certain environmental conditions (e.g. rain and dirt). Bicycle brake squeal is often solved by trial and error. Compared to automotive industry, there is not much research done on the fundamental cause of bicycle brake squeal. As a result, bicycle brands are not able to guarantee that their bicycles will not produce squeal noise over time. The goal of this graduation project is to get more insight into the fundamental cause of bicycle brake squeal and to find the crucial parameters that influence bicycle brake squeal.Mechanical Engineerin
On Affine Symbolic Regression Trees for the Solution of Functional Problems
No full textSymbolic regression has emerged from the more general method of Genetic Programming (GP) as a means of solving functional problems in physics and engineering, where a functional problem is interpreted here as a search problem in a function space. A good example of a functional problem in structural dynamics would be to find an exact solution of a nonlinear equation of motion. Symbolic regression is usually implemented in terms of a tree representation of the functions of interest; however, this is known to produce search spaces of high dimension and complexity. The aim of this chapter is to introduce a new representation—the affine symbolic regression tree. The search space size for the new representation is derived, and the results are compared to those for a standard regression tree. The results are illustrated by the search for an exact solution to several benchmark problems
Hydraulic brake-system for a bicycle
No full textThe invention relates to a hydraulic brake system for a bicycle which may or may not be provided with an auxiliary motor, comprising a brake disc and brake claws cooperating with the brake disc, as well as fluid-containing channels (4,6) that extend between an operating organ (1) and the brake claws, and which system further possesses a spring-loaded pistion (11) accommodated and moveable in a first chamber (13).Mechanical, Maritime and Materials Engineerin
An analytical elastic plastic contact model with strain hardening and frictional effects for normal and oblique impacts
No full textModel-Based Brake Control including Tyre Behaviour
No full textThe objective of the thesis is to develop a method for controlled braking of a vehicle. The brake pedal depression has been considered to be proportional to the intended deceleration. The brake controller is not aimed to replace a cruise control; it will have an anti-lock braking (ABS) function. The brake control is essentially designed to be a continuous control law with a continuous brake torque output suitable for using it on real world actuators. To develop the continuous control and taking into account the friction and elastic properties of the tyre, a quarter-car model with LuGre tyre has been derived. Considering only a quarter car keeps the model compact and by having 4 brake controllers each wheel can be controlled individually...Precision and Microsystems EngineeringMechanical, Maritime and Materials Engineerin
On the Detection and Quantification of Nonlinearity via Statistics of the Gradients of a Black-Box Model
No full textDetection and identification of nonlinearity is a task of high importance for
structural dynamics. Detecting nonlinearity in a structure, which has been
designed to operate in its linear region, might indicate the existence of
damage. Therefore, it is important, even for safety reasons, to detect when a
structure exhibits nonlinear behaviour. In the current work, a method to detect
nonlinearity is proposed, based on the distribution of the gradients of a
data-driven model, which is fitted on data acquired from the structure of
interest. The data-driven model herein is a neural network. The selection of
such a type of model was done in order to not allow the user to decide how
linear or nonlinear the model shall be, but to let the training algorithm of
the neural network shape the level of nonlinearity according to the training
data. The neural network is trained to predict the accelerations of the
structure for a time-instant using as inputs accelerations of previous
time-instants, i.e. one-step-ahead predictions. Afterwards, the gradients of
the output of the neural network with respect to its inputs are calculated.
Given that the structure is linear, the distribution of the aforementioned
gradients should be quite peaked, while in the case of a structure with
nonlinearities, the distribution of the gradients shall be more spread and,
potentially, multimodal. To test the above assumption, data from an
experimental structure are considered. The structure is tested under different
scenarios, some of which are linear and some nonlinear. The statistics of the
distributions of the gradients for the different scenarios can be used to
identify cases where nonlinearity is present. Moreover, via the proposed method
one is able to quantify the nonlinearity by observing higher values of standard
deviation of the distribution of the gradients for "more nonlinear" scenarios
Concept brake system of cycle-car
No full textTato diplomová práce se zabývá návrhem brzdové soustavy motorové tříkolky, konstrukčním řešením zvolené koncepce a homologováním. V úvodu se autor zaměřuje na charakteristiku mototříkolky z pohledu možných použitých a navrhovaných komponentů. Následná kapitola je zaměřena na výchozí parametry mototříkolky a její další návrhy a vyhodnocení různých řešení brzdových soustav. V další kapitole se autor zaměřuje na homologaci brzdové soustavy. Poslední kapitola už počítá s konstrukčním řešením zvolené brzdové soustavy.The diploma thesis deals with concept of brake system of cycle car, structural design and homologation. In introduction the author focuses on characteristics of the cycle car from the view of possibly used and suggested components. Another part of the thesis is focused on initial parameters of the cycle car and its other concepts and evaluation of different solutions of brake systems. Further, the author focuses on homologation of brake system. The last part of the thesis deals with constructive solution of chosen brake system.Katedra dopravních prostředků a diagnostikyDokončená práce s úspěšnou obhajobo
System Identification of the Brake Setup in the TU Delft Vehicle Test Lab
No full textTesting facilities such as the TU Delft Vehicle Test Lab (VTL) are needed to provide necessary experimental data to validate and to compare the performance of several ABS controllers like the Feed-Forward Braking controller. Before testing ABS controllers with the VTL measurement system, it needs to be improved first. Earlier measurements reported in [11] showed a lack of developed braking torque due to decreased bandwidth of the measurement setup. This problem could be within the hydraulic brake line of the VTL measurement setup. Pressure dynamics results of the original situation show a significant decrease when increasing the actuating frequency. Differences in pressure dynamics are examined by replacing the original brake hose with a stainless steel braided brake hose. Sinus wave excitation measurements show a relative small increase of the maximal reaching brake pressure with the design improvements situation. Random noise excitation measurements show increased bandwidth, compared to the frequency results reported in [4] and [11]. Improvements in brake pressure dynamics are realized by using a stainless steel braided brake hose in addition with relative low varying amplitudes.Precision and Microsystems EngineeringMechanical, Maritime and Materials Engineerin
Designing an Innovative Brake Control System
No full textCurrent trailers and caravans use overrun brakes, which cause overheated brakes in the mountains. A solution is to design an electric brake system in which the brakes are controlled electronically instead of mechanically. The report discusses the control models associated with braking, anti-sway detection and velocity sensor fusion. The RDW requires the force between the car and trailer to be regulated to zero within 0.6 seconds. The internal model based control method is used to design the controller. Test results show that the controller responds quick enough and is robust to disturbances. For the anti-sway detection, a calibration model is constructed that transforms the sensor data from the sensor’s reference frame to the trailer’s reference frame. Simulations with empirical data have verified the functionality of the calibration model. The angular yaw rate measured by a gyroscope can be used for anti-sway detection. A curve can be created that shows the relationship between the maximum allowed yaw rate and the velocity. In addition to that, an orientation model is constructed that can estimate the Euler angles and the gravity vector with a complementary filter. Consequently, the dynamic acceleration can be extracted obtained from the accelerometer. Several sensors are mounted to the E-Brake that can determine the velocity. A decentralised Kalman fusion filter is designed to estimate the velocity from the acceleration, velocity and GPS data.EE3L11 Bachelor graduation project Electrical EngineeringElectrical Engineerin
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