<p>The wheel loader is a type of engineering vehicle used primarily to move crude material over shorter distances. As the vehicle is designed without wheel suspension, wheel loader drivers are exposed to high levels of whole body vibration which influences ride comfort negatively. The work presented in this thesis has the aim to investigate the potential in adding an axle suspension to a wheel loader in order to reduce vibrations and increase handling quality. While suspended axles have great potential for improving ride comfort and performance, they will also necessarily affect the vehicle dynamic behaviour which is different in many aspects from that of passenger cars or other road vehicles: the wheel loader has a large pitch inertia compared to its mass, the axle loads vary considerably with loading condition, and the vehicle uses an articulated frame steering system rather than wheel steering. These issues must all be considered in the design process for a wheel loader suspension.</p><p>The effects of suspended axles on ride vibrations are analysed by simulating a multibody wheel loader model with and without axle suspension. Results from the simulations show that longitudinal and vertical acceleration levels are greatly reduced with axle suspension, but that the decrease in lateral acceleration is smaller. By reducing the roll stiffness lateral accelerations can be further reduced, although this may not be feasible because of requirements on handling stability. The pitching oscillation of the vehicle has also been studied as this is known to have a large influence on ride comfort. An analytical model is used to study the effect of front and rear suspension characteristics on the pitching response of the wheel loader, showing that a stiffer rear suspension is favourable for reducing pitching but also that a similar effect is attainable with a stiffer front suspension. Results are compared to multibody simulations which show the same trend as analytical predictions. By including a linearised representation of a hydropneumatic suspension in the models, it is also shown that favourable dynamic behaviour can be maintained when the vehicle is loaded by utilising the fact that suspension stiffness is increasing with axle load.</p><p>Articulated vehicles may exhibit lateral oscillations known as "snaking" when driven at high speed. The effect of suspended axles on these oscillations are analysed using a multibody simulation model of a wheel loader with an equivalent roll stiffness suspension model. It is found that the roll motion of the sprung mass has a slightly destabilising effect on the snaking oscillations. This effect is more pronounced if the body roll frequency is close to the frequency of the snaking motion, although this loss in stability can be compensated for by increasing the equivalent stiffness or damping of the steering system.</p><p>Together with existing vehicle dynamic theory and design rules, the studies reported in this work provide an insight into the specific issues related to suspension design for wheel loaders.</p>

The wheel loader is a type of engineering vehicle used primarily to move crude material over shorter distances. As the vehicle is designed without wheel suspension, wheel loader drivers are exposed to high levels of whole body vibration which influences ride comfort negatively. The work presented in this thesis has the aim to investigate the potential in adding an axle suspension to a wheel loader in order to reduce vibrations and increase handling quality. While suspended axles have great potential for improving ride comfort and performance, they will also necessarily affect the vehicle dynamic behaviour which is different in many aspects from that of passenger cars or other road vehicles: the wheel loader has a large pitch inertia compared to its mass, the axle loads vary considerably with loading condition, and the vehicle uses an articulated frame steering system rather than wheel steering. These issues must all be considered in the design process for a wheel loader suspension. The effects of suspended axles on ride vibrations are analysed by simulating a multibody wheel loader model with and without axle suspension. Results from the simulations show that longitudinal and vertical acceleration levels are greatly reduced with axle suspension, but that the decrease in lateral acceleration is smaller. By reducing the roll stiffness lateral accelerations can be further reduced, although this may not be feasible because of requirements on handling stability. The pitching oscillation of the vehicle has also been studied as this is known to have a large influence on ride comfort. An analytical model is used to study the effect of front and rear suspension characteristics on the pitching response of the wheel loader, showing that a stiffer rear suspension is favourable for reducing pitching but also that a similar effect is attainable with a stiffer front suspension. Results are compared to multibody simulations which show the same trend as analytical predictions. By including a linearised representation of a hydropneumatic suspension in the models, it is also shown that favourable dynamic behaviour can be maintained when the vehicle is loaded by utilising the fact that suspension stiffness is increasing with axle load. Articulated vehicles may exhibit lateral oscillations known as "snaking" when driven at high speed. The effect of suspended axles on these oscillations are analysed using a multibody simulation model of a wheel loader with an equivalent roll stiffness suspension model. It is found that the roll motion of the sprung mass has a slightly destabilising effect on the snaking oscillations. This effect is more pronounced if the body roll frequency is close to the frequency of the snaking motion, although this loss in stability can be compensated for by increasing the equivalent stiffness or damping of the steering system. Together with existing vehicle dynamic theory and design rules, the studies reported in this work provide an insight into the specific issues related to suspension design for wheel loaders. / QC 20101119

Förbränning av fossila bränslen är den största orsaken till ökade växthusgasutsläpp i atmosfären som i sin tur ligger till grund för klimatförändringarna. Europeiska Unionen uttrycker klimatförändringarna som ett existentiellt hot och har som mål att Europa ska bli en klimatneutral kontinent till år 2050. Arbetsmaskiner, som vanligtvis drivs på diesel, är ett energikrävande fordonsslag vid användning som år 2016 stod för 6 % av Sveriges totala växthusgasutsläpp. Vätgas kan vara ett alternativt drivmedel till diesel eller andra fossila drivmedel för att minska de utsläpp som arbetsmaskiner ger upphov till. Syftet med studien är att uppmärksamma arbetsmaskiners roll i en omställning till vätgasdrift samt sprida kunskap om vad en omställning skulle innebära för dagens användare av arbetsmaskiner. Detta görs genom att belysa möjlig etablering i nutid av fem utvalda vätgasdrivna arbetsmaskiner samt gestalta dem i ett framtida vätgassamhälle. De arbetsmaskiner som inkluderas i studien är hjullastare, pistmaskin, sopmaskin, traktor och motviktstruck. Metoden består av en förenklad litteraturöversyn i kombination med personlig kommunikation samt en anpassning av verktyget Technology Readiness Level (TRL) i syfte att bedöma den tekniska mognaden. Resultatet visar att det i dagsläget finns etableringsmöjligheter i olika former för samtliga arbetsmaskiner i regionen baserat på TRL. Vätgasdrivna motviktstruckar och sopmaskiner är båda tillräckligt mogna tekniker för att etableras direkt på marknaden genom inköp. Vätgasdrivna hjullastare, traktorer och pistmaskiner är fortfarande under utveckling och kan därför etableras i regionen genom forskning och ytterligare utveckling eller först efter produktlansering på marknaden. De utvalda vätgasdrivna arbetsmaskinerna kan verka i ett framtida vätgassamhälle på liknande vis som motsvarande fossildrivna arbetsmaskiner gör idag med fördelar som mindre miljöpåverkan, vibrationer och buller som i sin tur medför mindre underhållsbehov med tillhörande kostnader. Resultatet visar att det finns möjligheter redan idag att påskynda en förändring, inte bara i Gävleborg utan i hela Sverige. De utvalda arbetsmaskinerna är verksamma inom branscher som motsvarar stora delar av det svenska näringslivet, en omställning till vätgasdrift kan därför ha en stor betydelse för en nationell reducering av växthusgasutsläpp. Det finns stor potential, särskilt för aktörer inom industrin, att upprätta egen vätgasproduktion och därmed bli självförsörjande på vätgas som drivmedel till arbetsmaskiner. Detta kan bli en av de radikala förändringar som enligt EU behövs för att uppnå målet om att åstadkomma klimatneutralitet år 2050. / Burning of fossil fuels is the biggest cause of increased greenhouse gas (GHG) emissions into the atmosphere, which in turn leads to climate change. The European Union expresses climate change as an existential threat and aims to make Europe a climate-neutral continent by 2050. Non-road machinery vehicles (NMV), which are usually powered by diesel, are an energy-intensive type of vehicle during usage that in 2016 accounted for 6% of Sweden's total GHG emissions. Hydrogen can be an alternative fuel to diesel or other fossil fuels in order to reduce the emissions that originate from NMVs. The aim of this study is to draw attention to the role of NMVs in a conversion to hydrogen operation and to spread knowledge about what a conversion would mean for today's users of work machines. This is done by highlighting possible establishment in the present of five selected hydrogen powered NMVs and illustrate them in a future hydrogen society. The NMVs included in the study are wheel loaders, snow groomers, street sweepers, tractors and counterbalanced forklifts. The method consists of a simplified literature review in combination with personal communication and an adaptation of the tool Technology Readiness Level (TRL) in order to assess technical maturity. The results show that there are establishment opportunities in the present in various forms for all NMVs in Gävleborg based on TRL. Hydrogen powered counterbalanced forklifts and street sweepers are both sufficiently mature technologies to be established directly in the market through purchasing. Hydrogen powered wheel loaders, tractors and snow groomers are still under development and can therefore be established in the region through research and further development or after product launch. The selected hydrogen powered NMVs can operate in a future hydrogen society similarly to fossil-fueled NMVs but with benefits such as less environmental impact, vibrations and noise which in turn entails less maintenance needs with associated costs. There are opportunities already today to accelerate a change, not only in Gävleborg but throughout Sweden. The selected NMVs are active in industries that correspond to large parts of the Swedish business community, a transition to hydrogen operation can therefore be of great importance for a national reduction of GHG emissions. There is great potential, especially for players in the industry, to establish their own hydrogen production and thereby become self-sufficient in hydrogen intended for NMVs. This could be one of the radical changes that, according to the EU, are needed to achieve the goal of accomplishing climate-neutrality by 2050.