• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 25
  • 3
  • 1
  • 1
  • Tagged with
  • 33
  • 33
  • 33
  • 19
  • 7
  • 6
  • 6
  • 6
  • 6
  • 6
  • 6
  • 6
  • 6
  • 5
  • 5
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Robust recursive path-following control for autonomous heavy-duty vehicles / Controle robusto recursivo para seguimento de caminho aplicado à veículo autônomo de carga

Filipe Marques Barbosa 04 December 2018 (has links)
Path following and lateral stability are crucial issues for autonomous vehicles. Moreover, these problems increase in complexity when handling heavy-duty vehicles due to their poor manoeuvrability, large sizes and mass variation. In addition, uncertainties on mass may have the potential to significantly decrease the performance of the system, even to the point of destabilising it. These parametric variations must be taken into account during the design of the controller. However, robust control techniques usually require offline adjustment of auxiliary tuning parameters, which is not practical and leads to sub-optimal operation. Hence, this work presents an approach to path-following and lateral control for autonomous heavy-duty vehicles subject to parametric uncertainties by using a robust recursive regulator. The main advantage of the proposed controller is that it does not depend on the offline adjustment of tuning parameters. Parametric uncertainties were assumed to be on the payload, and an H∞ controller was used for performance comparison in simulations. The performance of both controllers is evaluated in a double lane-change manoeuvre. Simulation results showed that the proposed method had better performance in terms of robustness, lateral stability, driving smoothness and safety, which demonstrates that it is a very promising control technique for practical applications. Ultimately, experiment tests in a rigid heavy-duty truck validate what was found in simulation results. / O seguimento de caminho e a estabilidade lateral são questões cruciais para veículos autônomos. Além disso, devido à baixa capacidade de manobra, tamanho e grande variação de massa, estes problemas se tornam mais complexos quando se trata de veículos pesados. Adicionalmente, as incertezas na massa têm o potencial de diminuir significativamente o desempenho do sistema, chegando ao ponto de desestabilizá-lo, assim, essas variações paramétricas devem ser consideradas durante o projeto do controlador. No entanto, as técnicas de controle robusto geralmente exigem o ajuste off-line de parâmetros auxiliares do controlador, o que não é prático e lava a uma operação sub-ótima. Assim, este trabalho apresenta uma abordagem de controle de seguimento de caminho e controle lateral para veículos pesados autônomos sujeitos a incertezas paramétricas usando um regulador robusto recursivo. A principal vantagem deste controlador é que ele não depende do ajuste off-line de parâmetros. Assumiu-se que as incertezas paramétricas estavam na carga do veículo, e um controlador H∞ foi usado para comparar o desempenho em simulação. O desempenho de ambos os controladores é avaliado em uma manobra de mudança de faixa. Os resultados de simulação mostraram que o método proposto apresentou melhor desempenho em termos de robustez, estabilidade lateral, suavidade na condução e segurança, o que o demonstra como uma técnica de controle bastante promissora para aplicações práticas. Por fim, testes experimentais em um caminhão rígido reforçam os resultados obtidos em simulação.
12

Robust recursive path-following control for autonomous heavy-duty vehicles / Controle robusto recursivo para seguimento de caminho aplicado à veículo autônomo de carga

Barbosa, Filipe Marques 04 December 2018 (has links)
Path following and lateral stability are crucial issues for autonomous vehicles. Moreover, these problems increase in complexity when handling heavy-duty vehicles due to their poor manoeuvrability, large sizes and mass variation. In addition, uncertainties on mass may have the potential to significantly decrease the performance of the system, even to the point of destabilising it. These parametric variations must be taken into account during the design of the controller. However, robust control techniques usually require offline adjustment of auxiliary tuning parameters, which is not practical and leads to sub-optimal operation. Hence, this work presents an approach to path-following and lateral control for autonomous heavy-duty vehicles subject to parametric uncertainties by using a robust recursive regulator. The main advantage of the proposed controller is that it does not depend on the offline adjustment of tuning parameters. Parametric uncertainties were assumed to be on the payload, and an H∞ controller was used for performance comparison in simulations. The performance of both controllers is evaluated in a double lane-change manoeuvre. Simulation results showed that the proposed method had better performance in terms of robustness, lateral stability, driving smoothness and safety, which demonstrates that it is a very promising control technique for practical applications. Ultimately, experiment tests in a rigid heavy-duty truck validate what was found in simulation results. / O seguimento de caminho e a estabilidade lateral são questões cruciais para veículos autônomos. Além disso, devido à baixa capacidade de manobra, tamanho e grande variação de massa, estes problemas se tornam mais complexos quando se trata de veículos pesados. Adicionalmente, as incertezas na massa têm o potencial de diminuir significativamente o desempenho do sistema, chegando ao ponto de desestabilizá-lo, assim, essas variações paramétricas devem ser consideradas durante o projeto do controlador. No entanto, as técnicas de controle robusto geralmente exigem o ajuste off-line de parâmetros auxiliares do controlador, o que não é prático e lava a uma operação sub-ótima. Assim, este trabalho apresenta uma abordagem de controle de seguimento de caminho e controle lateral para veículos pesados autônomos sujeitos a incertezas paramétricas usando um regulador robusto recursivo. A principal vantagem deste controlador é que ele não depende do ajuste off-line de parâmetros. Assumiu-se que as incertezas paramétricas estavam na carga do veículo, e um controlador H∞ foi usado para comparar o desempenho em simulação. O desempenho de ambos os controladores é avaliado em uma manobra de mudança de faixa. Os resultados de simulação mostraram que o método proposto apresentou melhor desempenho em termos de robustez, estabilidade lateral, suavidade na condução e segurança, o que o demonstra como uma técnica de controle bastante promissora para aplicações práticas. Por fim, testes experimentais em um caminhão rígido reforçam os resultados obtidos em simulação.
13

New concept for the ground connection in Scania’s trucks and buses

LLORENTE, ANDRÉS January 2014 (has links)
Regarding the ground electrical connection in trucks and buses, the requirements of earthing in heavy-duty vehicles were gathered and evaluated. The most important problems in the state-of-the-art grounding devices are corrosion, electrical resistance and uncertainty in the mounting process, altogether with depreciation over time. The goal is to come up with new concepts that can give a more reliable and better ground connection into the frame with faster, easier and safer manufacturing operations. Several methods for attaching different ground connectors to the steel frame are going to be investigated, including bolted connections, press devices, soldering, brazing and local plating spots. It will be shown that the welding operation gives the best electrical results, while lowering mounting costs, time and variability. Two welded connectors are then going to be proposed as the best alternatives and a parallel investigation with both of them is going to be carried out. These new concepts, filed for patent protection, are going to be labelled as “SRM Welded ground stud” and “SRM Welded grounding nut”. The first of them consists of a plated steel threaded stud (M8 or M10) with a ring shaped contact surface built in one of the ends, where the Ø12 mm weld is to be performed onto the uncoated frame. The second concept comprises a stainless steel M10 round nut welded over a punched hole. The optimization will also cover different alternatives for plating metals, contact aid compounds and masking caps for both devices. The risk of mechanical weakening of the frame because of the new welded concepts is going to be tested for the case of the SRM Welded ground stud. The results will show an increase in fatigue resistance of at least 20% compared to the current ground screw. Furthermore, the strength of the welded interface will show higher proof load than the stud itself. The welded nuts, tested with torque loading, will show a sufficient performance as well. The electrical tests present an expected decrease in ground resistance of 40% for the welded stud and an increase of 28% for the welded nuts, compared with the current ground screw. The conclusion of this Master Thesis states the recommendation of the implementation of a new grounding method through the SRM Welded ground stud. Although, some modifications in the transportation process of the frames might be needed because of the new protruding parts, pointing an estimated distance of 20mm from the frame surface. / När det gäller jordad elanslutning i lastbilar och bussar, har kraven på jordning i tunga fordon samlats och utvärderats. De största problemen i de mest avancerade jordade enheterna är korrosion, elektriskt motstånd och osäkerhet i monteringsprocessen, sammantaget med avskrivning över tiden. Målet är att utveckla nya koncept som kan ge en bättre och mer tillförlitlig jordanslutning i ramen med snabbare, enklare och säkrare tillverkning. Flera metoder för att fästa olika mark kontakter till stålramen kommer att undersökas, bland annat skruvförband, pressanordning, lödning, hårdlödning och lokala pläteringsfläckar. Det kommer att visa att svetsning ger den bästa elektriska resultatet, samtidigt som monteringskostnader, tid och variabilitet minskar. Två svetsade kontakter kommer sedan att föreslås som de bästa alternativen och en parallell undersökning med dem båda kommer att genomföras. Dessa nya koncept, för vilka patentskydd har ansökts, kommer att märkas som “SRM Svetsade marktapp” och “SRM Svetsade jordmutter”. Den första av dem består av en pläterad stålgängad tapp med en ringformad kontaktyta byggt i en av ändarna, där svetsen skall utföras på den obelagda ramen. Det andra konceptet består av en rostfri rund mutter svetsad över ett stansat hål. Optimeringen kommer även att omfatta olika alternativ för pläterade metaller, kontaktstöds föreningar och maskeringslock för de båda enheterna. Risken för mekanisk försvagning av ramen på grund av det nya svetsade konceptet kommer att testas med avseende på fallet med SRM Svetsad bottenreglar. Resultaten visar en ökad utmattningshållfasthet på minst 20% jämfört med den nuvarande jordskruven. Dessutom kommer styrkan av den svetsade gränsytan uppvisa en högre provbelastning än tappen själv. De svetsade muttrarna, testade med momentbelastning, kommer också uppvisa en tillräcklig prestanda. De elektriska testerna presenterade en förväntad minskning av markmotståndet på 40% för svetsade tappar och en ökning med 28% för svetsade muttrar, jämfört med den nuvarande jordskruven. Slutsatsen av detta examensarbete anger en rekommendation av genomförandet av en ny jordningsmetod genom en SRM Svetsad marktapp. Trots detta kan vissa ändringar behövas i transportprocessen av ramarna på grund av de nya utskjutande delarna, vilka pekar från ramens yta med ett uppskattat avstånd av 20 mm.
14

Particulate matter analysis from engine outlet in heavy-duty diesel vehicles : A study of soot reactivity, morphology and ash-to-soot ratio from the outlet of 6-cylinder and 8-cylinder diesel engines. / Particulate matter analysis from engine outlet in heavy-duty diesel vehicles : A study of soot reactivity, morphology and ash-to-soot ratio from the outlet of 6-cylinder and 8-cylinder diesel engines.

Vlasenko, Tayisiya January 2023 (has links)
De ökande luftföroreningarna i Europa är ett allvarligt miljöproblem, och vägtransporterna är en av de största orsakerna till detta. För att ta itu med detta problem och uppfylla nya utsläppskrav måste efterbehandlingssystemen för avgaser förbättras. Det är viktigt att förstå sammansättningen, egenskaperna och mängden partiklar (PM) som produceras av dieselmotorer för att kunna minska partikelutsläppen med dieselpartikelfiltret (DPF). Denna studie ger en djupgående analys av partikelutsläpp från tunga dieselmotorer, med fokus på att förstå källorna till partikelutsläpp, deras inverkan på partikelns struktur och reaktivitet. Olika filter för att samla in partiklarna användes och analyserades. Dessutom utvecklades och diskuterades en extraktionsmetod för att avlägsna partiklarna från filtren. Förhållandet mellan aska och sot samt kinetiska oxidationsparametrar har undersökts för flera prover från sex- och åttacylindriga motorer under olika driftscykler. Morfologiska egenskaper hos aska och sot undersöktes med SEM. Askfraktionen uppskattades ligga mellan 3 och 23 procent av den totala PM-sammansättningen. Askans elementära sammansättning undersöktes med hjälp av EDS och ICP. Viktförlustkurvor erhölls med TGA och de kinetiska parametrarna för sotoxidation beräknades med den icke-isotermiska metoden. Aktiveringsenergierna, som befanns ligga i intervallet 145-162 kJ/mol, visade att alla de testade sotproverna hade en liknande reaktivitet. Ytterligare studier behövs för att förbättra insamlings- och analysmetoderna för att uppnå tillförlitliga resultat. / The rise in air pollution in Europe is a pressing environmental health concern, and road transport is a major contributor. To address this issue and meet new emission standards, exhaust aftertreatment systems must be improved. Understanding the composition, properties, and amount of particulate matter (PM) produced by diesel engines is critical for reducing PM emissions with the diesel particulate filter (DPF). This research provides an in-depth analysis of PM emissions produced by heavy-duty diesel engines, with focus on understanding the sources of PM emissions, their impact on the structure and on the reactivity of the PM. Various filters to collect the particulate were employed and critically analysed. Furthermore, an extraction procedure to remove the PM from the filters was developed and discussed. Ash to soot ratio and kinetic oxidation parameters have been investigated for several samples deriving from 6-cylinder and 8-cylinder engines during different operational cycles. Morphological features of ash and soot were investigated with SEM. The ash fraction was estimated to lie between 3 and 23 percent in the total PM composition. Ash elemental composition was carried out through EDS and ICP. Weight loss curves were obtained with TGA and the soot oxidation kinetic parameters were calculated with the non-isothermal multiple-ramp rates method. The activation energies, which were found to be in the range of 145-162 kJ/mol, demonstrated that all of the soot samples tested had a similar reactivity. Further studies are needed to improve the collection and analysis methods in order to achieve reliable results.
15

Development of an Accelerated Test Method for Compressed Natural Gas Fuel System Robustness against Contamination

Aretorn, Elias January 2023 (has links)
A key factor for driving the shift towards sustainable transportation systems is alternative fuels, where compressed natural gas (CNG) is a beneficial alternative to the conventional fossil fuels with respect to greenhouse gas emissions. A fuel system is needed for heavy-duty natural gas vehicles, in order to transport the highly pressurized gas from the fuel tanks to the internal combustion engine. The fuel system can be contaminated from several different sources – carry-over compressor oil from refuelling stations, water already present in the gas, manufacturing residuals and road dust entering the fuel system via the receptacle valve. The contaminants can induce fuel system failure modes, leading to poor engine performance, increased emissions or gas pressures above component pressure ratings. The objective of this thesis was to develop an accelerated test method to evaluate CNG fuel system robustness against contamination, to be able to prevent CNG fuel system failures and to ensure a high-quality product. The experimental setup was developed to be installed on a truck in order to utilize already present surrounding systems. The setup enables performance testing of six out of nine components belonging to the fuel system, which can be tested individually or combined in an arbitrary way. The setup induces premature failure modes primarily through excessive contamination in a controlled manner. An experimental procedure has been developed as a complement. Validation of metrics through testing is needed before the test method can be considered finalized. / En nyckelfaktor för att driva omställning mot hållbara transportsystem är alternativa bränslen, varpå naturgas (CNG) är ett slagkraftigt alternativ till konventionella fossila bränslen med avseende på utsläpp av växthusgaser. För att kunna transportera den högt trycksatta gasen från bränsletankarna till förbränningsmotorn krävs ett bränslesystem för tunga naturgasfordon. Bränslesystemet kan kontamineras genom ett flertal olika källor – överförd kompressorolja från tankstationer, vatten som redan finns i gasen, tillverkningsrester och vägdamm eller grus som tar sig in i systemet genom bränslepåfyllningsventilen. Kontamineringen kan ge upphov till felmoder i bränslesystemet, vilket leder till låg motorpresentanda, ökade utsläpp eller övertryck i systemet. Syftet med examensarbetet var att utveckla en accelererad testmetod för att utvärdera CNG-bränslesystems robusthet mot kontaminering, för att kunna förebygga systemfel och säkerställa en högkvalitativ produkt. Den experimentella uppställningen utvecklades för att monteras på lastbil, för att på så vis nyttja de kringliggande befintliga systemen. Uppställningen möjliggör prestandaprovning av sex av nio komponenter som tillhör bränslesystemet, som kan testas individuellt eller kombineras på ett godtyckligt sätt. Uppställningen framkallar tidiga felmoder, huvudsakligen genom excessiv kontaminering på ett kontrollerat vis. En metodbeskrivning har utvecklats som ett komplement till den experimentella uppställningen. Validering av metrik genom testning är nödvändigt för att finna testmetoden färdigställd.
16

Energy Consumption of Thermal Conditioning System for Heavy-duty Electric Vehicles / Energiförbrukning av termiskt konditioneringssystem för tunga elfordon

He, Haohao January 2021 (has links)
The deployment of electric vehicles has speeded up during the past ten years. As heavy-duty trucks are a significant source of GHG emissions, electrification is an encouraging way to lead to sustainability beyond doubt. However, some constraints regarding electric vehicles have emerged. Range extension is a primary challenge of the development of electric vehicles, where thermal conditioning systems can have a considerable impact. Some researches have been done on electric passenger vehicles. However, studies regarding the energy consumption for the thermal conditioning system of heavy-duty electric vehicles are scarcely provided.This study therefore focuses on estimating the energy consumption for the auxiliary heating/cooling and studying the influence of the ambient temperature, vehicle velocity, payload, and driving cycles. A designed integrated thermal conditioning system model was constructed in GT-SUITE, with three subsystems to provide thermal comfort for the truck cabin, meet the operative temperature for battery packs and condition the power electronics and the electric machine. Calibrations were done and yielded acceptable relative errors less than 10%, regarding the cabin and battery heaters.The study shows that the thermal conditioning system consumes the most energy during extremely cold weather, reaching up to 10 kW when the ambient temperature is lower than -20℃. Moreover, the energy consumption during heating/cooling will increase if the vehicle velocity increases. However, it remains stable during mild weather. Payload has different impacts on the energy consumption for heating and cooling. As higher payload results in higher waste heat from the electric machine and batteries, it alleviates the heating while burdens the cooling. Four different driving cycles were simulated, and the result reveals that despite the cycle with the lowest average speed has the highest energy consumption/km, however has the lowest average power.
17

Optimal Speed and Powertrain Control of a Heavy-Duty Vehicle in Urban Driving

Held, Manne January 2017 (has links)
A major challenge in the transportation industry is how to reduce the emissions of greenhouse gases. One way of achieving this in vehicles is to drive more fuel-efficiently. One recently developed technique that has been successful in reducing the fuel consumption is the look-ahead cruise controller, which utilizes future conditions such as road topography. In this this thesis, similar methods are used in order to reduce the fuel consumption of heavy-duty vehicles driving in environments where the required and desired velocity vary. The main focus is on vehicles in urban driving, which must alter their velocity due to, for instance, changing legal speed restrictions and the presence of intersections. The driving missions of such vehicles are here formulated as optimal control problems. In order to restrict the vehicle to drive in a way that does not deviate too much from a normal way of driving, constraints on the velocity are imposed based on statistics from real truck operation. In a first approach, the vehicle model is based on forces and the cost function involves the consumed energy. This problem is solved both offline using Pontryagin's maximum principle and online using a model predictive controller with a quadratic program formulation. Simulations show that 7 % energy can be saved without increasing the trip time nor deviating from a normal way of driving. In a second approach, the vehicle model is extended to include an engine and a gearbox with the objective of minimizing the fuel consumption. A fuel map for the engine and a polynomial function for the gearbox losses are extracted from experimental data and used in the model. This problem is solved using dynamic programming taking into consideration gear changes, coasting with gear and coasting in neutral. Simulations show that by allowing the use of coasting in neutral gear, 13 % fuel can be saved without increasing the trip time or deviating from a normal way of driving. Finally, an implementation of a rule-based controller into an advanced vehicle model in highway driving is performed. The controller identifies sections of downhills where fuel can be saved by coasting in neutral gear. / En stor utmaning för transportsektorn är hur utsläppen av växthusgaser ska minskas. Detta kan åstadkommas i fordon genom att köra bränslesnålare. En nyligen utvecklad teknik som har varit framgångsrik i att minska bränsleförbrukningen är framförhållningsreglering, som använder framtida förhållanden så som vägtopografi. I denna avhandling används liknande metoder för att minska bränsleförbrukningen i tunga fordon som kör i miljöer där önskad och tvingad hastighet varierar. Fokus ligger framförallt på fordon i stadskörning, där hastigheten måste varieras beroende på bland annat hastighetsbegränsningar och korsningar. Denna typ av körning formuleras här som optimala reglerproblem. För att hindra fordonet från att avvika för mycket från ett normalt körbeteende sätts begränsningar på tillåten hastighet baserat på statistik från verklig körning. Problemet angrips först genom att använda en fordonsmodell baserad på krafter och en kriteriefunktion innehållande energiförbrukning. Problemet löses både offline med Pontryagin's maximum princip och online med modellprediktiv reglering baserad på kvadratisk programmering. Simuleringar visar att 7 % energi kan sparas utan att öka körtiden eller avvika från ett normalt körbeteende. Problemet angrips sedan genom att utöka fordonsmodellen till att också innehålla motor och växellåda med målet att minimera bränsleförbrukningen. Specifik bränsleförbrukning och en polynomisk approximation av förlusterna i växellådan är extraherade från experiment och används i simuleringarna. Problemet löses genom dynamisk programmering som tar hänsyn till växling, släpning och frirullning. Simuleringar visar att 13 % bränsle kan sparas utan att öka körtid eller avvika från normalt körbeteende genom att tillåta frirullning. Slutligen görs en implementering av en regelbaserad regulator på en avancerad fordonsmodell för ett fordon i motorvägskörning. Regulatorn identifierar sektioner med nedförsbackar där bränsle kan sparas genom frirulllning. / <p>QC 20171011</p>
18

A new heavy-duty vehicle visual classification and activity estimation method for regional mobile source emissions modeling

Yoon, Seungju 20 July 2005 (has links)
For Heavy-duty vehicles (HDVs), the distribution of vehicle miles traveled (VMT) by vehicle type is the most significant parameters for onroad mobile source emissions modeling used in the development of air quality management and regional transportation plans. There are two approaches for the development of the HDV VMT distribution; one approach uses HDV registration data and annual mileage accumulation rates, and another uses HDV VMT counts/observations collected with the FHWA truck classification. For the purpose of emissions modeling, the FHWA truck classes are converted to those used by the MOBILE6.2 emissions rate model by using either the EPA guidance or the National Research Council conversion factors. However, both these approaches have uncertainties in the development of onroad HDV VMT distributions that can lead to large unknowns in the modeled HDV emissions. This dissertation reports a new heavy-duty vehicle visual classification and activity estimation method that minimizes uncertainties in current HDV conversion methods and the vehicle registration based HDV VMT estimation guidance. The HDV visual classification scheme called the X-scheme, which classifies HDV/truck classes by vehicle physical characteristics (the number of axles, gross vehicle weight ratings, tractor-trailer configurations, etc.) converts FHWA truck classes into EPA HDV classes without losing the original resolution of HDV/truck activity and emission characteristics. The new HDV activity estimation method using publicly available HDV activity databases minimizes uncertainties in the vehicle registration based VMT estimation method suggested by EPA. The analysis of emissions impact with the new method indicates that emissions with the EPA HDV VMT estimation guidance are underestimated by 22.9% and 25.0% for oxides of nitrogen and fine particulate matter respectively within the 20-county Atlanta metropolitan area. Because the new heavy-duty vehicle visual classification and activity estimation method has the ability to provide accurate HDV activity and emissions estimates, this method has the potential to significantly influence policymaking processes in regional air quality management and transportation planning. In addition, the ability to estimate link-specific emissions benefits Federal and local agencies in the development of project (microscale), regional (mesoscale), and national (macroscale) level air quality management and transportation plans.
19

Design and Implementation of a Strategy for Path Tracking on Autonomous Heavy-Duty Vehicles

Törnroth, Oscar, Nyberg, Truls January 2018 (has links)
In this thesis, a combined feedforward and feedback controller for improved path tracking on autonomous heavy-duty vehicles is designed and implemented. The steering wheel is controlled in order to follow a reference curvature, computed by a higher-level MPC, responsible for minimizing the distance to a planned path. The steering dynamics, from steering wheel via wheel angles, to a measurable vehicle curvature, is modeled, and a conversion from desired curvature gain to input angle to the steering wheel is derived. Tests with an autonomous Scania R580 show that the desired curvature can be followed with satisfactory small error, both in a designed slalom path and on a more generic test track. By utilizing future curvature values computed by the MPC, a non-causal feedforward controller can reduce the delay from input to the steering wheel to a measured response in curvature, by almost two thirds, compared to the currently implemented solution. Compared to an open-loop control design, tests in simulation show that a feedback controller can reduce errors in curvature gain. However, with the identified steering dynamics and the improved conversion from steering wheel angle to curvature, no further improvement in the curvature gain was seen when implementing the feedback controller in the test vehicle. Care must also be taken not to introduce instability in the system when the feedback controller is implemented in series with a high-level MPC. / Den här rapporten beskriver design och implementering av en regulator med kombinerad framkoppling och återkoppling för förbättrad banföljning av autonoma tunga fordon. Fordonets ratt styrs för att följa en kurvaturreferens beräknad av en överordnad MPC, ansvarig för att minimera avståndet till en planerad bana. Dynamiken i styrningen, från ratten via hjulvinklarna till en mätbar kurvatur för fordonet, är modellerad. En översättning från önskad förstärkning av kurvatur till insignal för rattvinkeln är också framtagen. Tester utförda med en autonom Scania R580 visar att den önskade kurvaturen kan följas med tillfredsställande litet fel, både i en egendesignad slalombana och i en mer generisk testbana. Genom att utnyttja framtida referensvärden för kurvatur beräknade av MPC:n, kan en icke-kausal framkopplande regulator minska fördröjningen från insignal till ratten till en mätbar respons i fordonets kurvatur. Jämfört med den nuvarande lösningen minskas fördröjningen med nästan två tredjedelar. Jämfört med en öppen styrning visar tester i simulering att en återkoppling i regulatorn kan minska stationära fel i kurvatur. Med implementeringen av den identifierade styrdynamiken och den förbättrade översättningen från rattvinkel till kurvatur, syntes dock med återkoppling ingen ytterliggare förbättring i testfordonet. Implementering av den återkopplande regulatorn i serie med den överordnade MPC:n behöver också göras med omsorg för att inte introducera instabilitet i systemet.
20

Data driven estimation of cabin dynamics in heavy-duty vehicles

Markovic, Bratislav January 2019 (has links)
With increasing demand for autonomous systems and self-driving heavy-dutyvehicles there is an even more increasing demand for safety. In order to achievedesired safety level on the public roads, engineers have to tackle many technicalissues, like decision making, object detection and perception. In order to detect anobject or to have an understanding of its surroundings, autonomous heavy-dutyvehicles are equipped with different types of sensors. These sensors are placed ondifferent parts of the autonomous truck. The fact that some parts of the truckare highly dynamical introduces additional disturbances to the signals comingfrom onboard sensors. One of the most dynamic parts of every truck is its cabin.Moving cabin may induce additional disturbances into data coming from sensorsattached to it. This corrupted data may lead the autonomous trucks to make wrongdecisions. In the worst case, such decisions may be fatal.This thesis uses a data driven modeling approach for creating a mathematicaldescription of cabin movements based on data from onboard sensors. For thatpurpose, tools from system identification field are used. The resulting modelsare aimed to be used for implementation of real-time estimation algorithm forthe cabin dynamics, which in turn can be used for real-time compensation of thedisturbances. / Ee ökad efterfrågan efter autonoma fordon sätter ännu högre krav på säkerhet.Eftersom mäniskors säkerhet alltid prioriteras högst så måste ingenjörer runtom i världen att se till att framtida självkörande lastbilar inte bara är heltautonoma utan framför allt säkra. För att uppnå önskad säkerhetsnivå på deallmänna vägarna måste ingenjörerna ta itu med många tekniska problem, somexempelvis beslutsfattande, objektdetektering och perception. För att upptäckaett föremål eller att förstå sin omgivning är autonoma lastbilar numera utrustademed olika typer av sensorer. Dessa sensorer är monterade på olika delar av denautonoma lastbilen. Det faktum att vissa delar av en lastbil är mycket dynamiskaintroducerar ytterligare störningar i signler som kommer från de sensorer somfinns monterade på fordonet. En av de mest dynamiska delarna av varje lastbilär hytten. Hyttens rörelser kan orsaka ytterligare störningar i data som kommerfrån sensorer som är anslutna till den. Den felaktiga informationen kan ledatill att det autonoma fordonet fattar felaktiga beslut, som i värsta skulle kunnaorsaka dödsfall. Detta examensarbete använder sig av datadriven modelleringför att beskriva det matematiska förhållandet mellan hytt och chassi baserat pådata som kommer från de sensorer som finns monterade på fordonet. För attdetta ändamål skulle kunna uppnås används systemidentifieringsteknik. Bådegrey-box och black-box systemidentifieringsmetod användas och jämföras för attkunna erhålla ett resultat som visar vilken av de två teknikerna är bäst lämpad fördetta ändamål.

Page generated in 0.0694 seconds