A mechatronic two-axle rail vehicle with only one suspension step is introduced in the Shift2Rail project Pivot2. This vehicle design reduces the vehicle weight in comparison to standard bogie vehicles. However, having only one suspension step drastically decreases passenger comfort. Thus, hydraulic actuators are introduced instead of passive dampers and active modal sky-hook control is applied. Due to the strong interaction between the running gear frame and the carbody, a blended modal solution is applied where a percentage of the acceleration of the frame is used in the feedback loop in addition to the acceleration of the carbody. To assess the performance of the controllers, simulations are carried out with the vehicle running at constant speeds from 10 km/h to 120 km/h on tangent track with high level of track irregularities. First, multiplicative dimensional reduction method (M-DRM) sensitivity analysis is applied to determine the importance of the control variables and subsequently a genetic algorithm (GA) optimization is performed to identify the control gains for each speed. The blended control proposed here can improve passenger comfort with respect to a standard modal control while maintaining similar energy and force usage.

Increased equivalent conicity of wheels because of hollow wear during long-term operation influences the ride comfort performance of Chinese high-speed trains. To investigate the evolution of wheel wear, a high-speed train operating on the Beijing-Shanghai Railway line at maximum operational speed of 350 km/h is monitored over a time of 1.5 years. An MBS based wear calculation software tool of KTH using stochastic simulation inputs has been used for wear prediction, where the vehicle suspension parameters and global structural modes of car-body and bogie frame have been identified using roller rig measurements and dynamic track measurements as well to validate the simulation models. The calculated wear is then validated against measurements by calibrating the wear rate coefficients. The influence of initial conicity on the lateral wear distribution is analyzed. Wheel profiles with lower initial conicities result in significantly less wear but more vibrations which possibly worsen the ride comfort. Increasing the roll-stiffness shows to be an effective way to damp the low frequency vibrations for the low conicity wheel while resulting in low wear. The suspension parameters and initial conicity which give the most stable equivalent conicity evolution and best ride comfort are selected for field tests.

In the Shift2Rail project Pivot2 an innovative two-axle single suspension step metro vehicle is proposed. The single suspension step requires active suspensions to improve passenger ride comfort both in vertical and lateral direction. Two control approaches are developed, modal and blended control. Despite the good achievements with regard to comfort improvement, the robustness and performance of the developed controllers in relation to wheel degradation due to wear is unknown. Two different track types and three rail inclinations are used to generate worn wheel profiles with the KTH wear method creating a 75 wheel-rail combination set. For each combination, the comfort is evaluated with the vehicle travelling at constant speed from 50 km/h to 120 km/h with 5 km/h interval, producing a set of 1125 ride comfort evaluation points. Results show that both controllers are robust and that good ride comfort of the innovative vehicle can be maintained according to the EN12299 standard also in case of wheel degradation due to wear. Blended control produces enhanced performance with respect to its modal counterpart in vertical direction.

The mechatronic vehicle developed within the Shift2Rail projects Run2Rail, Pivot, NEXTGEAR, and Pivot2 is evaluated with respect to wheel wear. The KTH wear model is used to determine the coefficients of Archard’s wear map to reproduce measured worn wheel profiles of the present vehicle running on Metro Madrid line 10. The same wear model is then used to evaluate the performance of the mechatronic vehicle controlled with two variants of a feedforward controller. The first one uses on-board measurements, while the second one is optimised using firefly optimisation algorithms assuming knowledge of the travelled track. The control strategy based on on-board measurements shows improvements above 60% in terms of lost wheel volume due to wear, compared to the standard bogie vehicle. The optimised controller reaches improvements above 70%. Good coherence is found between improvements predicted with the wear number and the ones achieved in terms of lost wheel volume.

Energy and maintenance costs constitute a large part of the recurring cost for railway operation. The vehicle weight impacts both energy consumption and the need for tamping of the track, while curving performance impacts the curving resistance and the wear on wheels and rails. In the project RUN2Rail and further in NextGear, both parts of the EU-funded initiative Shift2Rail, a single axle running gear with composite frame and active wheelset guidance was proposed for metro vehicles. The present study is comparing a reference vehicle from Metro Madrid with the proposed vehicle in terms of energy consumption and maintenance cost for simulated service on Metro Madrid Line 10 with curvature, gradients, stops and speed profiles considered. The calculated yearly saving for each vehicle become about 50 k€/(year*trainset), split on 20% on energy and 40% on each of wheel and track maintenance.

Within the Shift2Rail research program the goals for a sustainable growth of the railway sector are set. Among these are substantial reduction of Life Cycle Costs, improved reliability and energy efficiency, the reductionof noise emissions, and the achievement of full interoperability of the rolling stock. Therefore, a new generation of running gear is envisioned.

An innovative two-axle vehicle that can reduce weight, initial investmentand maintenance cost, and emissions is proposed for a metro line system. The vehicle proposed will have only one suspension step. To further reducethe weight and incorporate the otherwise missing anti-roll bar, a compositematerial connection frame is introduced. The two-axle configuration suffers from poor ride comfort, due to the lack of a second suspension step acting as filter, and from poor steering capability, due to the long distance between wheelsets. Active suspensions are therefore introduced to improve both ride comfort and steering capability.

This Ph.D. thesis showcases the key activities undertaken during the developmentof the innovative vehicle, building a simulation framework where the vehicle can be virtually tested. Several modelling environments are used such as: SIMPACK for vehicle dynamics, Abaqus for finite elements modelling, Simscape for hydraulic physics simulations, and Simulink for control logic development. During the Ph.D. time two elements of the mechatronic vehicle have been designed and manufactured, i.e. the carbon fiber connection frame and the steering active suspension. The two components models have been experimentally validated and introduced into the simulation environment. A ride comfort and a wheelset steering control strategy have been designed to overcome the limitations introduced by the two-axle configuration. The proposed solutions aim at being applicable in the whole operational scenario of the innovative vehicle.

The present work emphasises the possibility of introducing innovative mechatronic solutions as an alternative to standard bogie solutions aiming at reducing costs and emissions, blurring the boundaries between academic view and possible industrial applications.

Inom forskningsprogrammet Shift2Rail sattes målen för en hållbar tillväxt av järnvägssektorn. Dessa mål innefattar en avsevärd minskning av livscykelkostnader, en ökad tillförlitlighet och energieffektivitet, minskning av bullerutsläpp och full driftskompatibilitet för den rullande materielen. För att uppnå målen föreslås här en ny generation av löpverk.

Ett innovativt tvåaxligt fordon som kan minska vikten, den initiala investerings- och underhållskostnaden samt utsläppen föreslås därför här för ett tunnelbanesystem. Det föreslagna fordonet kommer bara att ha ett fjädringssteg. För att ytterligare minska vikten och inkludera den annars saknade krängningshämmaren, introduceras en sammankopplande ram av kompositmaterial. Den tvåaxliga konfigurationen lider av dålig åkkomfort, eftersom det saknas ett andra fjädringssteg som fungerar som filter. På grund av det långa hjulaxelavståndet lider konfigurationen även av dålig styrförmåga. För att förbättra både åkkomfort och styrförmåga introduceras därför aktiva fjädringar.

Denna doktorsavhandling beskriver de viktigaste aktiviteterna som genomfördes under utvecklingen av det innovativa fordonet, uppbyggnaden av ett simuleringsramverk där fordonet kan testas virtuellt. Flera modelleringsmiljöer används, såsom SIMPACK för fordonsdynamik, Abaqus för modellering i finita element, Simscape för hydrauliska simuleringar och Simulink för utveckling av styrlogiken. Under doktorsarbetets gång har två delar av det mekatroniska fordonet designats och tillverkats, det är kolfiberkopplingsramen och den aktiva fjädringen i styrningen. Modellerna för dessa två komponenter har experimentellt validerats och introducerats i simuleringsmiljön. Kontrollstrategier för åkkomfort och styrningen av hjulaxlarna har utformats för att övervinna de begränsningar som den tvåaxliga konfigurationen innebär. De föreslagna lösningarna syftar till att vara tillämpliga i hela driftscenariot för det innovativa fordonet.

Detta arbete betonar möjligheten att introducera innovativa mekatroniska lösningar som ett alternativ till vanliga boggilösningar som syftar till att minska kostnader och utsläpp, och sudda ut gränserna mellan den akademiska synen och möjliga industriella tillämpningar.

A mechatronic rail vehicle with reduced tare weight, two axles and only one level of suspension is proposed with the objective of reducing investment and maintenance costs. A wheelset to carbody connection frame in composite material will be used both as structural and as suspension element. Active control is introduced to steer the wheelsets and improve the curving performance. A feedforward control approach for active curve steering based on non-compensated lateral acceleration and curvature is proposed to overcome stability issues of a feedback approach. The feedforward approach is synthesised starting from the best achievable results of selected feedback approaches in terms of wheel energy dissipation and required actuation force. A set of 357 running cases (embracing 7 curves, 17 speeds per curve and 3 conicities) is used to design the controller. The controller is shown to perform well for conicity and track geometry variations and under the presence of track irregularities.

Intelligent fault identification of rail vehicles from onboard measurements is of utmost importance to reduce the operating and maintenance cost of high-speed vehicles. Early identification of vehicle faults responsible for an unsafe situation, such as the instable running of highspeed vehicles, is very important to ensure the safety of operating rail vehicles. However, this task is challenging because of the nonlinear dynamics associated with multiple subsystems of the rail vehicle. The task becomes more challenging with only accelerations recorded in the carbody where, nevertheless, sensor maintenance is significantly lower compared to axlebox accelerometers. This paper proposes a Temporal Convolution Network (TCN)-based intelligent fault detection algorithm to detect rail vehicle faults. In this investigation, the classifiers are trained and tested with the results of numerical simulations of a high-speed vehicle (200 km/h). The TCN based fault classification algorithm identifies the rail vehicle faults with 98.7% accuracy. The proposed method contributes towards digitalization of rail vehicle maintenance through condition-based and predictive maintenance.

Within the Shift2Rail project RUN2Rail, an innovative Metro vehicle with single axle running gear is proposed. In NEXTGEAR, also a Shift2Rail project, the work is continued to achieve a higher technical readiness level. For a 2-axle vehicle with a wheelset distance of 8 m the contradiction between stability and curving performance is imminent, and an active wheelset guidance is considered necessary for networks with many small curve radii. For networks with larger curve radii a passive solution might be enough. A nonlinear axle guidance stiffness that has the potential to improve the curving performance is studied here. The running gear frame is modelled in Abaqus® and structural frame modes are implemented in SIMPACK® together with the other suspension elements. To select the properties of the nonlinear spring, simulations are performed to check stability at demanding conditions at 160 km/h on tangent track as well in a curve with 1000 m radius. These two cases give the high and low guidance stiffness of the nonlinear spring. The results show that a nonlinear wheelset guidance can reduce the wear compared to a linear guidance and be an alternative to active wheelset steering for networks with low numbers of narrow curves.

The Shift2Rail project Pivot2 introduces an innovative metro vehicle with two single axle running gears with only one suspension step to reduce the vehicle's weight. A U-shaped connection frame is designed in Carbon Fibre Reinforced Polymer to further reduce weight and incorporate the anti-roll bar. Due to the poor ride comfort of the vehicle with standard passive dampers, all six dampers are replaced by hydraulic actuators. Modal control is applied and optimized with genetic algorithms. Despite the good improvements obtained, the weighted vertical acceleration remains above the acceptance level. Two modifications of modal control are studied, i.e., modal control with additional sensor, and blended control. Based on the frequency response of the results, it is proposed a low-pass filtered blended controller to neglect frame accelerations high frequency content. This last improves vertical comfort at the expenses of a more complex control system in comparison to modal control.