Active secondary suspension in trains has been studied for a number of years, showing promising improvements in ride comfort. However, due to relatively high implementation and maintenance costs, active technology is not being used in service operation to a large extent. The objective of this study is to develop an active lateral secondary suspension concept that offers good ride comfort improvements and enables centring of the carbody above the bogies when negotiating curves at unbalanced speed. Simultaneously, the active suspension concept should be a cost-effective solution for future series production. The thesis consists of an introductory part and three appended papers. The introductory part describes the concept of active secondary suspension together with different actuator types and control methods. Further, the present simulation model and applied comfort evaluation methods are presented. The introductory part also comprises a summary of the appended papers, an evaluation of track forces and suggestions for further work. Paper A presents the initial development of an active lateral secondary suspension concept based on sky-hook damping in order to improve vehicle dynamic performance, particularly on straight tracks. Furthermore, a Hold-Off-Device (HOD) function has been included in the suspension concept in order to centre the carbody above the bogies in curves and hence avoid bumpstop contact. Preparatory simulations as well as the subsequent on-track tests in the summer of 2007 showed that the active suspension provides improved passenger ride comfort and has significant potential to be a cost-effective solution for future implementation. In Paper B, measurement results from on-track tests performed in 2008 are presented. The active secondary suspension concept was slightly modified compared to the one presented in the first paper. One modification was the implementation of a gyroscope in order to enable detection of transition curves and to switch off the dynamic damping in these sections. Ride comfort in the actively suspended carbody was significantly improved compared to that in the passively suspended car. The satisfactory results led to implementation of the active suspension system in long-term tests in service operation in the beginning of 2009. In Paper C, a quarter-car model in MATLAB has been used to investigate a more advanced control algorithm: H∞ instead of sky-hook. H∞ control provides more flexibility in the design process due to the possibility to control several parameters. In particular, this is done by applying weight functions to selected signals in the system. When comparing the two control strategies through simulations, the results show that H∞ control generates similar carbody accelerations at the same control force as sky-hook; however, the relative displacement displacement is somewhat lower.

<p>Most of the heavy-duty machines, in particular construction vehicles, employ hydraulically actuated functions that are used to perform multiple tasks with elevated power requirements. Such high-power demand motivates the Original Equipment Manufacturers (OEMs) to minimize the costs associated with energy consumption through the design of such hydraulic systems. The human-machine interaction (human factors) and the efficiency of the hydraulic control system are considered key elements towards a successful design. The interaction between the operator and the machine considerably affects the performance of construction machines. In order to maintain high levels of productivity, the operators require comfort and effortless controllability of the multiple hydraulic functions. The comfort requirement can include limited shocks and oscillations while operating the machines (while driving and controlling the implement motion), cabin accessories (AC, radio, cameras, etc.) and accessibility to the instrumentation. Besides, the operators have to control multiple functions simultaneously in an efficient manner while maintaining high levels of productivity. Consequently, the operators require smooth controllability of such functions. Such demand can largely affect the efficiency of the expected hydraulic control system and can induce additional costs and complexity. The OEMs are therefore forced to find a balance between efficiency and operators’ requirements to be competitive on the market. As a result, the currently adopted hydraulic architectures rely on purely hydraulic components to ensure robustness and functionality of the hydraulic functions at the expenses of limited performance and high-power consumption. In this dissertation, electro-hydraulic components are employed to induce improvements of the commercially available solutions while still complying with the operators’ demands and energy efficiency. To this end, this work tackles the weaknesses of traditional hydraulic architectures and it proposes alternative solutions to overcome their limitations. Two full-size wheel loaders are used to study the behavior of the existing system and later to implement the proposed variations. First, the development of an innovative ride control feature to improve the operators’ comfort is presented. Experimental results show the proposed strategy having better comfort performances compared to the purely hydraulic solution. Besides, the electro-hydraulic alternative does not demand the costly additional components the commercial solution instead requires. Second, this work faces the concern for efficiency of the present hydraulic architecture. The most diffused hydraulic system for the studied category of construction machines, commonly known as Load Sensing (LS), is sized to work most efficiently for elevated power conditions. During this work, an electronically controlled hydraulic supply unit and a flow-sharing method are used to reduce the hydraulic power consumption in the regions where the traditional LS system is less efficient. With a simple and cost-effective modification, the presented control strategy can induce an efficiency improvement over a wide range of operating conditions. Third, this dissertation proposes an operator-assistance feature to potentially increase the overall productivity and reduce the operator’s stress. An online estimation algorithm was developed to predict the payload weight of the transported material inside the bucket and the pushing forces during a typical loading cycle. The calculated payload mass provides an estimate of the user’s productivity level and it is extremely advantageous when the loaded material should reach a certain target weight. The developed estimation algorithm can also support an optimized autonomous excavation process, which can progressively limit the operator-machine interaction.</p>

This thesis explores the puzzling subnational variation of policymaking for the online ride-hailing industry (ORS) in China. Chengdu and Jinan are two similar cities on many economic and political levels. They are both capital cities of their provinces, new first-tier cities in terms of their economic size and both have a large population. Yet, they adopted significantly different ORS policies. This thesis asks why two similar cities in China have diverging policy outcomes. Using a method of difference (MOD) strategy to compare these two similar cases with diverging outcomes, the thesis evaluates three potential explanations. They are as follows: (1) historical legacies and political communities, (2) the cadre evaluation system (CES), and (3) government-business relationships. Using a historical institutionalism theoretical framework with comparative capitalism and economic sociology roots, this thesis finds that a mixture of CES incentives and government business relationship patterns has had a determining impact on diverging outcomes in Jinan and Chengdu. There have been two phases of ORS policymaking in China until now. In phase 1, Chengdu had a laxer ORS policy than Jinan. A comparison of historical legacies and political communities tells us that Chengdu has been a more market-oriented city than Jinan. More importantly, Jinan’s government had a more intimate relationship with local taxi agencies, which proved to be the major cause of subnational differences. In phase 2, Chengdu’s ORS policy was found to be more stringent than Jinan’s. In this case, the significant variable leading to Chengdu’s tightened policy was the target-setting of the cadre evaluation system (CES). The CES specifically required Chengdu’s government to ban non-green vehicles from the ORS market while Jinan did not encounter the same requirement. Moreover, Jinan can exclude non-green vehicles from its environmental protection plan while Chengdu cannot. This thesis observes a structural distortion caused by the CES. Throughout the two phases of ORS policymaking, both governments play a consistently dominant role. However, the government-business relationship remains flexible. If the relationship is viewed as an institution, it is composed of informal procedures, conventions, and orders where actors accommodate each other. The largest privately-owned ORS enterprise, Didi, has declared that their preferences are taken into consideration by the government. Some questions remain as to how the government processes those preferences and how much importance it attaches to them, but this illustrates the mutual accommodation of the government and an enterprise within an informal institution. By some unwritten but conventional procedures, they coordinate with each other. This thesis furthers the study of the government-business relationship in China. It not only unearths the institutional factors of subnational variation for ORS policymaking, but also verifies the presence of institutional flexibility in China. This thesis is an important addition to the literature on government-business ties in China because it does beyond the study of rent-seeking to evaluate the multifaceted ways in which the Chinese government can build relationships with enterprises.

In the digital age, with the accelerating pace of e-commerce, online platforms such as Amazon, Yelp, TripAdvisor, Facebook, Netflix, Uber and others have gained in prominence. Furthermore, in the wake of the COVID-19 pandemic, even businesses which were heretofore primarily brick-and-mortar have had to shift to a strong online presence in order to adapt and survive; which, while beneficial to all stakeholders, has resulted in dire challenges for the producers/service providers, platform owners, as well as consumers. In my first essay, I investigate the challenges faced by mobility as a service (MaaS) platforms such as Uber and Lyft for managing their demand and the pool of available drivers. On one hand, driver compensation issues in MaaS platforms is a highly discussed topic. On the other hand, the MaaS platforms are expanding to encompass several external businesses in search of profitability. In this chapter, I focus primarily on driver compensation issues in MaaS platforms when the platforms engage in external businesses. I find that in the majority of instances, the driver compensation reduces when the platforms get involved in external businesses; however, there are a few cases, where it leads to an increment in driver compensation, thus benefiting them. The second essay is on the impact of online reviews from digital platforms such as Yelp and TripAdvisor on business performance. Using a data set from Yelp, first, I study the interaction of average rating and number of reviews on business performance; second, how competition affects the interaction effect of the average rating and number of reviews on the focal business' performance. I find that the impact of the interaction of average rating and number of reviews on business performance is different at various levels of average ratings, and the inclusion of competition negatively influences the interaction effect of the average rating and number of reviews on the performance of the focal restaurant. In my third essay, I analyze how the interaction of supplier encroachment and consumer showrooming impacts an omnichannel retailer and her upstream manufacturer, who encroaches the downstream retailer's market with an online direct sales channel. I identify different scenarios in a covered market where either the retailer, or the manufacturer, or both will be better off. Taken together, these three essays provide valuable managerial insights for real world business problems, which will empower researchers in academia and industry managers, and help them improve their businesses and maximize their operational performance. / Business Administration/Marketing

In last decade, there is a large increase in installed capacity of wind power. Asmore wind power is integrated into utility networks, related technologychallenges draw much attention. The doubly fed induction generator (DFIG) isthe mainstream choice for wind turbine generator (WTG) in current market andthe object of this thesis. It is very sensitive to voltage dips. The enhancement oflow voltage ride through (LVRT) is one of the most important issues for DFIG,and many works have already been done to provide solutions.In current works, the voltage dip waveforms that are applied in LVRTrelated works are largely different from waveforms in reality, because they failto consider the the effect of realistic wind farm configurations on waveforms ofvoltage dips and significant influences of additional characteristics of voltagedips. The true impact of the voltage dip needs to be assessed in performanceevaluation and development of LVRT methods. To support the development ofpractical LVRT capacity enhancement solutions, the application of voltage dipknowledge is definitely demanded.In this thesis, the characteristics of realistic waveform voltage dips in windfarm are analyized based on voltage dip knowldege from power quality field,measured voltage dip from industry and realistic wind farm configurations.Classical analysis theory is applied to explain the principles of the impact ofvoltage dip characteristics on dynamic behavior of DFIG. The impacts of manywidely neglected characteristics such as phase angle jump (PAJ), point on wave(POW) of initiation and recovery, voltage recovery process, transformerconfigurations, load effect are revealed and verified by simulations. The impactof many voltage dip characteristics on DFIG are studied for the first time. / De senaste tio åren har sett en stor ökning av installerad effekt av vindkraft.Mer vindkraft i elnäten har lett till större uppmärksamhet om dess tekniskautmaningar. Den dubbelmatad asynkrongenerator (DFIG) är idag denvanligaste förekommande typen i vindkraftverk. Den är mycket känslig förspänningssänkningar. Förbättring av tålighet för spänningssänkningar (LVRT)är en av de viktigaste frågorna för DFIG, och många studier har redan söktlösningar.I befintliga studier om LVRT har spänningssänkningarna skiljt sig väsentligtfrån verkliga vågformer, då de inte har tagit hänsyn till realistiskavindparkkonfigurationer och betydande påverkan av ytterligare egenskaper hosspänningssänkningar. För att stödja utvecklingen av praktiska LVRT lösningarbehövs mer kunskap om spänningssänkningar för att bedöma dess verkligainverkan.Detta examensarbete förbättrar LVRT analysen av DFIG genom att tillämpakunskap om spänningssänkningar från elkvalitetsområdet, tillsammans medrealistiska vindparkskonfigurationer. Inflytandet av ändringar i fasvinkel(PAJ), fasvinkeln vid sänkning och återhämtning (POW), spänningsåterhämtning, transformatorkonfigurationer, last och många andra egenskaperav spänningssänkningar ingår också. Inflytandet av många egenskaper avspänningssänkningar studeras här akademiskt för första gången. Denkaraktäristik av realistiska spänningssänkningar som inträffar vid generatornspoler, och de effekter dessa har, studeras och förklaras genom teoretisk analysoch intensiva simuleringar.

Ride-sourcing is a digital transportation service that has seen a considerable growth in the last half decade especially in the biggest cities around the world. More and more digital platforms for ride-sourcing has emerged since its inception. This study compares the two ride-sourcing applications available in Stockholm— Uber and Heetch, using a combined method of measuring desirability and usability to analyze which factors influence a user’s choice of app. The results showed Uber to have better desirability and usability, and 14 out of the 16 participants chose Uber as their preferred ride-sourcing app. / Samåkningstjänster är en digital transporttjänst som har haft en betydande tillväxt under det senaste halvdecenniet och allt fler digitala plattformar för samåkningstjänster har tillkommit sedan dess uppkomst, särskilt i de största städerna runt om i världen. Denna studie jämför två samåkningstjänster tillgängliga i Stockholm: Uber och Heetch, med en kombinerad metod genom att undersöka önskvärda aspekter och användbarhet för analys av användarnas val av applikation. Resultatet visade att Uber hade bättre önskvärda aspekter och användbarhet, och 14 av 16 deltagande valde Uber som sin föredragna applikation

To produce competitive vehicles, their comfort is one important issue to take into account during the development process. The aim of this Master Thesis is to develop an on-line comfort evaluation tool in order to improve research and education in the field of vehicle comfort at the division of Vehicle Dynamics at the Royal Institute of Technology. Based on ISO standards concerning comfort an on-line evaluation tool has been developed using DASYLab, which is a software that allows creation of acquisition, control, simulation and analysis tasks. The developed tool has been evaluated by performing measurements of a VOLVO V40 equipped with sensors. Different sorts of surfaces and driving conditions have been investigated, and from this investigation one can conclude that the comfort tool works properly.

The advent of on-demand transport modes such as ride-hailing and microtransit has challenged forecasters to develop new methods of forecasting the use and impacts of such modes. In particular, there is some professional disagreement about the relative role of activity-based transportation behavior models -- which have detailed understanding of the person making a trip and its purpose -- and multi-agent demand simulations which may have a better understanding of the availability and service characteristics of on-demand services. A particular question surrounds how the relative strengths of these two approaches might be successfully paired in practice. Using daily plans generated by the activity-based model ActivitySim as inputs to the BEAM multi-agent simulation, we construct nine different methodological combinations by allowing the choice to use a pooled ride-hail service in ActivitySim, in BEAM with different utility functions, or in both. Within each combination, we estimate ride-hailing ridership and level of service measures. The results suggest that mode choice model structure drastically affects ride-hailing ridership and level of service. In addition, we see that multi-agent simulation overstates the demand interest relative to an activity-based model, but there may be opportunities in future research to implement feedback loops to balance the ridership and level of service forecasts between the two models.

Carbody tilting is today a mature and inexpensive technology allowing higher speeds in curves and thus reduced travel time. The technology is accepted by most train operators, but a limited set of issues still holding back the full potential of tilting trains. The present study identifies and report on these issues in the first of two parts in this thesis. The second part is dedicated to analysis of some of the identified issues. The first part contains Chapters 2 to 5 and the second Chapters 6 to 12 where also the conclusions of the present study are given. Chapters 2 and 3 are related to the tilting train and the interaction between track and vehicle. Cross-wind stability is identified as critical for high-speed tilting trains. Limitation of the permissible speed in curves at high speed may be needed, reducing the benefit of tilting trains at very high speed. Track shift forces can also be safety critical for tilting vehicles at high speed. An improved track standard must be considered for high speed curving. Chapters 4 and 5 cover motion sickness knowledge, which may be important for the competitiveness of tilting trains. However, reduced risk of motion sickness may be contradictory to comfort in a traditional sense, one aspect can not be considered without also considering the other. One pure motion is not the likely cause to the motion sickness experienced in motion trains. A combination of motions is much more provocative and much more likely the cause. It is also likely that head rotations contribute as these may be performed at much higher motion amplitudes than performed by the train. Chapter 6 deals with services suitable for tilting trains. An analysis shows relations between cant deficiency, top speed, tractive performance and running times for a tilting train. About 9% running time may be gained on the Swedish line Stockholm – Gothenburg (457 km) if cant deficiency, top speed and tractive performance are improved compared with existing tilting trains. One interesting conclusion is that a non-tilting very high-speed train (280 km/h) will have longer running times than a tilting train with today’s maximum speed and tractive power. This statement is independent of top speed and tractive power of the non-tilting vehicle. Chapters 7 to 9 describe motion sickness tests made on-track within the EU-funded research project Fast And Comfortable Trains (FACT). An analysis is made showing correlation between vertical acceleration and motion sickness. However, vertical acceleration could not be pointed out as the cause to motion sickness as the correlation between vertical acceleration and several other motions are strong. Chapter 10 reports on design of track geometry. Guidelines for design of track cant are given optimising the counteracting requirements on comfort in non-tilting trains and risk of motion sickness in tilting trains. The guidelines are finally compared with the applied track cant on the Swedish line Stockholm – Gothenburg. Also transition curves and vertical track geometry are shortly discussed. Chapters 11 and 12 discusses the analysis, draws conclusions on the findings and gives proposals of further research within the present area. / QC 20101119

Det finns en uppsjö av böcker och filmer som förklarar ridecymbalteknik och hur olika ridecymbalmönster ska spelas. Däremot saknas beskrivningar på ridecymbalteknik kopplat till handrörelser istället för rytmisering. I den här uppsatsen har ridecymbaltekniker undersökts och hur dessa kan läras ut inom ramen för kategorin tutorials på Youtube. Först studerades 18 Youtube-klipp och därefter genomfördes en kategorisering av ridecymbalteknikerna utifrån ett tekniskt perspektiv. Därefter valdes fem stycken av dessa tutorials som sedan analyserades utifrån ett multimodalt perspektiv. Studien har resulterat i att jag har fått mer kunskaper om ridecymbaltekniker och hur multimodalitet kan användas i undervisning både digitalt som analogt och betonar hur tutorials på Youtube kan ses som ett komplement till den traditionella undervisningen. Studiens fördjupning har även gett upphov till utökade tekniska och multimodala mer detaljerade kunskaper som kan kopplas till tidigare studier om exempelvis timing och multimodala aspekter som handlar om lektionsupplägg och lärarpersonligheter. / There exists a vast variety of books and movies that explain ride cymbal technique and how different patterns are supposed to be played. On the other hand there is a lack of descriptions of ride cymbal technique connected to hand movements instead of rhythmisation. In this thesis I have been investigating ride cymbal techniques and how to teach the subject. Firstly I chose to study 18 Youtube clips and subsequently five out of these which were then analysed from a multimodal perspective. The study has given me more knowledge about ride cymbal techniques and how to apply multimodality both digitally and analogically. It also shows how Youtube tutorials can complement traditional teaching approaches. The elaboration of the study has given rise to expanded more detailed knowledge related to earlier studies about for example timing and multimodal aspects regarding lesson set-up and teacher personalities.