本論文ではロードノイズに関するタイヤ振動特性を予測する上で必要となるタイヤモデルの構築と接地・転動時のタイヤ振動特性の変化要因について解明することを目的にしている.薄肉円筒シェル理論に基づきタイヤばね付きリングモデルを構築し,Rayleigh法を用いてタイヤの固有振動数の式を導出した.また,径方向モードに着目し,非接地・転動時,接地・非転動時,接地・転動時におけるタイヤ振動特性の理論解析を行い,その特性を明らかにした. / 博士(工学) / Doctor of Philosophy in Engineering / 同志社大学 / Doshisha University

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A large portion of the world’s total emissions is caused by the transport sector where rolling resistance is one of the contributing factors. The inner tyre temperature is a factor that greatly influences the rolling resistance. The effect of temperature and rolling resistance is often examined in standardised tests carried out in a lab environment. In this work, field tests were carried to find out typical operating temperatures in real driving scenarios. The field tests were carried out on one set of A-class tyres and one set of B-class tyres at different speeds: city-, small country road-, large country road- and motorway driving. Tests were performed in varying ambient temperatures and weather conditions. The results show that the rear inner tyre temperature varies between 11 to 36C in the spring around Linköping in Sweden. A brush model was also developed to see how accurately the rolling resistance could be predicted. With springs, dampers, and Coulomb friction elements the behaviour of rubber was captured. The final model contains five model parameters that were estimated by parameter fitting to measurement data, using optimisation. Measurements were carried out at a test rig that measures the forces acting on the tyre. The measurements were performed for both the A-class and B-class tyre at two different temperatures corresponding to the findings from the field tests. The results show that the developed model has a promising correlation with the measurements for all loads and speeds that were tested.

This work deals with a fork bending oscillation phenomenon observed during hard braking on bicycles. The observed oscillation is described with experimental data and an attempt is made to understand the underlying root cause. Therefore, a multibody model consisting of the front wheel and the fork is employed to simulate a braking maneuver. The self-oscillation is replicated in simulation and implications on the brake process are derived from it. Fork and tire oscillations on bicycles are rarely described in scientific literature. An oscillation due to tire resonance on high-speed motorcycles was described by Cossalter [1]. However, the mentioned speed dependence is not found in the present case under investigation. Klug et al. [2] were the first to report an oscillation of the fork inclination angle during braking. They noticed oscillations in the front wheel speed signals measured with a speed encoder mounted on the fork. Measurements of accelerometers and gyroscopes placed on the fork near the hub showed these oscillations on the forks inclination angular rate and vertical acceleration as well. This makes the phenomenon relevant for suspension and braking control. They also described the distorting effect of fork bending on the wheel speed signal and the wheel slip calculation derived from it. This work tries to identify a root cause of the fork bending oscillation and investigates its influence on the stopping performance.

A proof-of-concept indirect tire-pressure monitoring system is developed using neural net- works to identify the tire pressure of a vehicle tire. A quarter-car model was developed with Matlab and Simulink to generate simulated accelerometer output data. Simulation data are used to train and evaluate a recurrent neural network with long short-term memory blocks (RNN-LSTM) and a convolutional neural network (CNN) developed in Python with Tensorflow. Bayesian Optimization via SigOpt was used to optimize training and model parameters. The predictive accuracy and training speed of the two models with various parameters are compared. Finally, future work and improvements are discussed.

The presence of nitrates and phosphorus in ground water is a worldwide problem. A septic tank with drainfield that is conventionally designed does not typically remove nitrogen in the form of nitrates. The main risks are in "Blue baby" syndrome and suspected carcinogenic effect of nitrates on humans and the nutrient enrichment of receiving waters. In some areas nitrate and phosphorus removal are essentially required. Thus the information in this report concentrates on using media in the drainfield for the removal of nitrogen and phosphorus. Extensive work has been conducted in the past few decades in order to find suitable media for denitrification with high selectivity towards nitrogen. Column experiments were conducted at the University of Central Florida to simulate the actual septic tank drainfield using mixes of fine sand. In one of the columns Sawdust and Tire Crumb were added to the Sand (STS) and in the other column Paper and Tire Crumb were added to the Sand (STP). Tire crumb was added as a carbon source required for better denitrification and for sorption. The columns were dosed daily using regular septic tank effluent and it was a continuous batch system. Samples were taken after a hydraulic retention time (HRT) of 24 hours and comparisons were made of the effluent with the influent to show percentage removal of nitrogen (nitrates, ammonia and total nitrogen), phosphorus (ortho-phosphorus and total phosphorus) and BOD. STS and STP columns showed more than 90% removal for all parameters (nitrates, ammonia, total nitrogen, ortho-phosphorus, total phosphorus, BOD). The results indicate that the investigated media blend (Black and GoldTM Nugget Mix) has the potential for successful application in full scale operations. It is recommended that Black and GoldTM Nugget Mix be used to achieve the required removal of the nutrients.

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Tire tread health is essential for safe operation of a passenger vehicle. Worn out tires significantly increases the risk of traffic accidents and hydroplaning. This thesis investigates the possibility to detect tire tread wear by estimating the effective rolling radius of a tire. The effective rolling radius of a tire is affected by several different factors. As to not confuse change in external factors with actual tire tread wear, there is therefore a need to compensate the effective rolling radius to nominal conditions, to make sure that the change in compensated rolling radius is only due to the tire tread wear. This raises the questions: how can the effective rolling radius be estimated? Can it be compensated with respect to external factors? The behavior of the tire changes between different tire models. This is because different models uses different materials, patterns, internal structure etc. This raises an additional question. Can a compensation model with the same parameter values be used in all vehicles of the same type no matter the tires of the vehicle, or is there a need for an adaptive compensation model that adapts the parameters to the current tire? This thesis investigates how the estimation of the tires effective rolling radius can be improved by estimating the velocity using sensor fusion between GPS- and IMU-signals. This was done using an Extended Kalman Filter. Furthermore, this thesis proposes different ways of compensating a tires effective rolling radius with respect to external factors and compares these methods with each other to obtain the most efficient compensation method. After finding an appropriate compensation method, further investigations regarding the need of adaptivity between tires was performed to find out if the compensation factors can be used on the same vehicle model with different tire sets. Ultimately, the investigations showed that the estimation of the effective rolling radius of a tire using sensor fusion was not fruitful due to limitations set by the IMU. If the vehicle had been equipped with a 6-axis IMU instead of a 3-axis IMU, this method might be feasible. The method that directly calculates the effective rolling radius from GPS-velocity and wheel speed gave a more accurate rolling radius signal. The compensation of the effective rolling radius can be achieved with respect to velocity, tire pressure and tire temperature. The most advantageous compensation method proposed in this thesis was a polynomial compensation model. Lastly, when investigating the need of adaptive compensation factors it was found that these compensation factors needs to be adaptive between tire sets.