Dynamic calibration of an instrumented bike brake hood in measuring power absorbed by the hands

AbstractOne of the most significant factors in ride quality in cycling sports are the vibrations generated by road surface defects passing through the bicycle and transmitted to the cyclist's hands and buttocks. To study comfort, one metric that has been put forward is the measurement of the power absorbed at the cyclist's hands. Measuring absorbed power requires the use of the force and the velocity at the hands and provides an overall energy-based quantity. The aim of this study is to dynamically calibrate an instrumented brake hood transducer to measure the power absorbed at the cyclist's hands. Using a base excitation technique involving suspended masses, dynamic calibration of the brake hood was conducted in the 3-100 Hz frequency range, and the force transducer sensitivity and seismic mass were measured. An accelerometer attached to the brake hood enabled measurements of acceleration and calculation of velocity. A frequency-dependent phase mismatch between the force signal and the acceleration was obtained by measuring the accelerance at the hand-bike interface. A device called the Power Calibrator equipped with an impedance head was developed to assess the accuracy of the power measured by the instrumented brake hood. The results show that the instrumented brake hood can accurately measure the absorbed power at the cyclist's hands. Phase mismatch between the force and the velocity signals must be corrected to improve the accuracy of measurements. To implement the measurements, it is recommended that the calculations be done in the frequency domain

On the exposure of hands to vibration in road cycling: an assessment of the effect of gloves and handlebar tape

The objective of this work was to assess the effectiveness of cycling gloves and handlebar tape in reducing the vibration transmitted to the cyclist’s hands in the classic “hoods” position for shock-type excitation at the front wheel on a bicycle treadmill. Three pairs of conditions were tested on a single participant: (1) With gloves vs. no gloves, no bar tape; (2) With bar tape vs. no bar tape, no gloves; (3) With gloves and bar tape vs. no gloves and no bar tape. We have shown that a rider can expect a small but significant drop in the level of transmitted power and energy through the handlebars when wearing a standard pair of road cycling gloves. If bar tape is used however (both with and without gloves), there is a significantly larger drop in the level of transmitted power and energy through the handlebars

Méthode de création de forme optimale en élastostatique bidimensionnelle

Cette thèse propose une nouvelle méthode d'optimisation des structures: la méthode de création de forme optimale.Cette méthode concerne des structures en élastostatique bidimensionnelle. Contrairement à toutes les méthodes d'optimisation de forme proposées jusqu'à présent et pour lesquelles la forme initiale de la membrure est entièrement connue, cette méthode permet de générer une structure de forme optimale à partir d'une géométrie de structure partiellement connue initialement. Elle permet donc d'apporter le concept de génération de forme à l'optimisation de forme. La forme optimale est obtenue à l'aide d'une méthode basée sur le mouvement normal du contour de la structure.Cette méthode est une version modifiée par l'auteur d'une méthode proposée initialement par Umetani et Hirai. Ces modifications permettent d'en faire une méthode beaucoup plus versatile et applicable à des problèmes saturés ou non. II s'agit ici d'uniformiser la valeur de la contrainte équivalente de von Mises sur les parties modifiables du contour de la structure c'est-à-dire d'obtenir un design de type F.S.D. ("Fully Stressed Design"). Un tel design est utilisé comme critère d'optimalité. La valeur de la contrainte équivalente de von Mises sur le contour de la structure est évaluée à l'aide de la méthode des éléments de frontière évitant ainsi toute discrétisation de l'intérieur de la structure. La géométrie de la structure quant à elle est représentée par des courbes B-splines, ces dernières s'étant avérées tout à fait adaptées à la représentation de formes quelconques et complexes

Using an Alternative Forced-choice Method to Study Shock Perception at Cyclists’ Hands: The Effect of Tyre Pressure

AbstractIn road cycling, tyre pressure has an influence on both performance and comfort of the cyclist. In this paper, the relationship between tyre pressure and shock perception at the cyclist's hands was quantitatively analysed by measuring the Just Noticeable Difference in Level (JNDL) of tyre pressure. The JNDL was determined by using a three-alternative forced-choice (3-AFC) method. The measurement was carried out on seven healthy subjects exposed to shock-type excitation on a laboratory bicycle treadmill. The dispersion of the measured tyre pressure JNDL (69 to 241 kPa; mean 155 kPa; SD 73 kPa) shows a large variability in the hands’ perception of shock in the cyclists tested. This suggests that some cyclists have a better capacity than others to differentiate impact sensory inputs at the hands, making them more likely to discern subtle differences in bicycle response dynamics

On the effects of tube butting on the structural performance of steel bicycle frames

Previous studies have shown how finite element analysis (FEA) can be used to support designers and frame builders in the selection of butted tubes to tune the stiffness and strength behaviour of steel bicycles. The aim of this paper was therefore to analyse the effects of tube butting on the stiffness, stress distribution and energy absorption behaviour of bicycle frames using numerical simulations. Butted tubes were shown to provide a highly effective means to decrease mass whilst producing a disproportionately small change in stress compared with a straight gauge tubeset with a maximum material condition although there was no added benefit in terms of stiffness or strain energy. Conversely, decreasing the wall thickness produced an increase in stress at the tube ends that was disproportionate to the change in mass. This work can now be extended to analyse a fuller set of butted profiles for a range of tube types

Integrated Assessment of Swiss GHG Mitigation Policies After 2012: Coupling the Residential Sector

The residential sector presents a great potential for greenhouse gases (GHG) mitigation. We perform an integrated assessment of different mitigation policies for Switzerland focusing on the residential sector. We analyze the case of pure incentive taxes and technical regulations. For our analysis, we have coupled a general equilibrium model with a Swiss residential energy model. We find that a progressive GHG tax of more than 200 USD2000/tCO2eq is necessary to reach a target of 50% reduction of GHG emissions in 2050. Finally, we also find that efficiency-based technical regulations provide limited additional abatement incentive