Estimation of adhesion conditions between wheels and rails for the development of advanced braking control system

An ideal braking system not only ensures safety and ride comfort but also attracts significant cost-benefits through optimum on-time operation and reduction in wheel-rail damage processes. For such a braking system, the adhesion condition information between the wheel and rail at contact interfaces during rail vehicle operation is essential. The adhesion estimation for the braking system is a complex task because it is influenced by operational factors such as non-linear wheel and rail geometry, rail vehicle speed, track irregularities, axle load distributions, etc., plus environmental factors such as third body layer characteristics, presence of friction modifiers, and rail-wheel temperatures. The research objective of this thesis is to estimate the adhesion condition between wheel and rail and implement the obtained adhesion condition information for the improvement of braking performance of a heavy haul wagon. The research methodologies used for the realisation of the defined objective are based on specially designed algorithm development, numerical modelling, and scaled laboratory experiment techniques. A novel real-time multipoint wheel-rail contact model was constructed using a modular approach and validated with the contact point function of Gensys multibody software. Then, a simplified fast-processing adhesion estimation algorithm was developed including the contact model that provides anticipated results in both rolling and braking conditions. The simplified algorithm was further improved by designing a novel observer which analyses the adhesion in real-time. Then a real-time scaled bogie test rig model was developed for the validation of the developed adhesion estimation algorithm with the purpose of its integration in an advanced braking control system. For the transition from the algorithm development and numerical scaled bogie test rig modelling to the physical implementation, the numerical findings need to be compared with a set of experimental results. Therefore, an experimental scaled bogie test rig was re-designed based on an existing heavy haul wagon design and equipped with a newly designed braking system for the conceptual validation of the system. For robust and reliable estimation of the adhesion condition, the acoustic signal emanating from wheel-rail interaction was considered in this project as an additional input parameter. Finally, the noise analysis method and a wheel-rail adhesion observer were integrated into a novel mechatronic brake control system for accurate and reliable estimation of adhesion conditions. The performance analysis of the mechatronic brake system shows that the proposed system can achieve a shorter stopping distance in comparison with both a conventional controller and with no controller. It also indicates that the developed mechatronic brake system can maintain the operational condition even under a degraded adhesion condition. This research work contributes knowledge to the process of adhesion estimation between wheel and rail contact in a real-time mode that is currently unavailable and has therefore not been implemented in existing rollingstock brake control system designs. This study confirms the capability for enhancement of the productivity, efficiencies, and safety of trains that will ultimately be a contribution toward sustainable transportation.