<p>Road conditions affect fuel efficiency and vehicle fatigue when driving heavy trucks. Information about traveled road conditions enable optimization of chassis configuration when driving, and logging of vehicle stress. Previous work on this topic focus mainly on tuning of active suspension parameters in the car industry. One conceivable application for heavy trucks is implementation of active chassis level control based on road conditions, with possible improvements in driving economy as result. Another is logging of usage conditions which helps explain vehicle faults caused by abnormal wear. This work examines the possibilities to use already on vehicle sensors for road roughness estimation. It also investigates what requirements existing signals must fulfill to ensure reliable estimates. Two methods for road roughness estimation are proposed using rear axle level sensor and a simple linear suspension system model.</p>

Chinese heavy truck industry has witnessed an unprecedentedprosper since 2009, and it has been attracting an increasing number of westernheavy truck companies to conduct business activities. However, differentindustry environment has brought different situation including the government’spolicies and consumers’ buying habits for local companies and foreign competitors.Thus, this study aims to analyze the impact of industry factors in Chinese heavy truck industry by examining a collection of the methodology. Porter diamond model is widely applied to investigate industry’s competitive advantages, butit should be noted that in this research the model is adapted into a new version in light of the necessity of emphasizing Chinese government in businessactivities. Main findings of this study are as follows: (1) research andanalysis factors of impact Chinese heavy truck industry and highlight government’s influence as a significant impact factor through a series ofpolicies; (2) it might be of considerable benefit if foreign heavy truckcorporation can observe the political transformation or policies while setting themarketing strategy in China.

Road conditions affect fuel efficiency and vehicle fatigue when driving heavy trucks. Information about traveled road conditions enable optimization of chassis configuration when driving, and logging of vehicle stress. Previous work on this topic focus mainly on tuning of active suspension parameters in the car industry. One conceivable application for heavy trucks is implementation of active chassis level control based on road conditions, with possible improvements in driving economy as result. Another is logging of usage conditions which helps explain vehicle faults caused by abnormal wear. This work examines the possibilities to use already on vehicle sensors for road roughness estimation. It also investigates what requirements existing signals must fulfill to ensure reliable estimates. Two methods for road roughness estimation are proposed using rear axle level sensor and a simple linear suspension system model.

This study includes an experimental evaluation of a prototype trailing-arm suspension for heavy trucks. The primary goal of this new suspension is to match or improve the kinematics and dynamic performance of an existing "Z-bar" suspension. Significant reductions in cost, weight, and number of parts are the main reasons for this redesign. A permanent facility is constructed to support the testing of different heavy truck suspensions. For actuation of the vehicle suspension, hydraulic actuators are used in the kinematics tests in a quasi-dynamic manner. For the dynamic tests, the vehicle is excited using two hydrodynamic actuators. A collection of forces, displacements, velocities, and accelerations are measured during the tests using transducers that were installed on the suspension and test vehicle. The test measurements are analyzed in both time and frequency domains and then the results of the two suspensions were compared to establish the dynamic merits of the prototype suspension. The kinematics tests include vertical stiffness, roll stiffness, and roll steer measurements for each suspension. The results from the kinematics tests show that the trailing-arm suspension exhibits kinematics traits that are quite similar to the "Z-bar" suspension, within the context of the tests conducted in the study. The dynamic testing consists of three input signals commonly used for such tests, namely: a chirp signal input, a step signal input, and a range of pure tone inputs. The test results show that the resonant frequencies of the two primary suspensions differ by an amount that is most likely too small to affect ride dynamics. The two suspensions, however, exhibit significantly different damping characteristics. The new suspension has much less frictional damping than the existing suspension. This is expected to provide better ride characteristics, assuming that the primary dampers (shock absorbers) are properly tuned for the vehicle that the new suspension was designed for. / Master of Science

Semi-active dampers utilizing various working principles have been developed for a variety of vehicles. These semi-active dampers have been designed to resolve the ride and handling compromise associated with conventional passive dampers, and increase vehicle stability. This thesis briefly reviews existing semi-active damper designs, including but not limited to MR dampers, before presenting two new prototype semi-active hydraulic dampers. Both prototype dampers are designed to provide a large force range while maintaining easily controllable valve characteristics. The first of these dampers served primarily as a proof of concept and a means of understanding the dynamics of a disc valve housed inside the main piston. The valve design is presented, along with other information concerning the fabrication of the Initial Prototype damper. Test results are presented and analyzed, and a second iteration of the valve is designed. The Final Prototype damper is a scaled up version of the initial design, with refinements made in piston geometry, internal disc profile, and dynamic seals. This large force range damper is tested and results are compared with existing MR dampers. The Final Prototype damper provides a significantly larger force range when compared with typical MR dampers. Finally, to conclude this research, the vehicle dynamics implications of the Final Prototype damper are discussed and recommendations for further study are made. / Master of Science

This research provides a thorough flow characterization study to compare the functionality of two types of load-leveling valves that are commonly used for air suspension systems of commercial trucks. The first valve features a simple disk/slot design and is relatively compact for installation. The second type is larger and has a sophisticated, chambered design, which allows for considerably quicker fill and exhaust response times in the transient region. A new approach is introduced to estimate the transient mass flow rate of a load-leveling valve under different suspension pressures, without requiring a mass flow meter. An extensive series of dynamic tests are conducted to characterize and compare the two load-leveling valves. A generic heavy-truck pneumatic suspension, consisting of load-leveling valves, airspring, air tank, and air-hose fittings, is configured for testing. The test setup is used to evaluate the transient performance of each type of load-leveling valve in a typical truck suspension. The flow behavior of the system is validated by the force/pressure responses of the air spring due to various displacement excitations. The experimental results describe the detailed flow behavior of both valves. The flow characterization results can be incorporated as one of the most critical parameters for future model development of pneumatic systems. The tests indicate that the leveling valve with chambered design has a far faster transient flow response than the disk valve, although it is more complicated in its mechanical design and therefore costs more. To take advantage of the design simplicity of the disk valve, while also enabling it to have a faster transient response (compared with the chambered design), it is re-designed with larger flow openings and other elements to match the performance of the chambered valve for transient flow. A comparison of the experimental results and simulations validates that the re-designed rotary disk valve performs nearly the same as the chambered valve, but is simpler and costs less. The study's results are directly applicable to improving the transient dynamics of heavy truck air suspensions by providing a better understanding of how load-leveling valves can be used not only to provide ride-height control, but also to influence the roll and pitch dynamics of heavy trucks. / Master of Science

The efficiency of the transport sector is under close examination due to multiple different reasons. Among them are the environmental aspects of emission reduction along with the need to maintain a tight time schedule. Heavy trucks have a significant negative impact on the environment and are sensitive to external factors. Planning green routes is a way to minimize the emissions from heavy trucks by reducing the fuel consumption without sacrificing travel time. This thesis will investigate suspected parameters relevance to the fuel consumption of heavy trucks and their effect on the fuel consumption on heavy trucks. To achieve this, two independent literature searches were conducted, the first to find the relevance and the second to understand the effect. Then a comparison was made with the NVDB to see if the suspected parameters were represented by the attributes in the database. The result of the first literature search varied and the speed and congestion parameter showed the strongest relevance to the fuel consumption of the heavy truck. The second literature search found past research that stated that the fuel consumption of heavy trucks were affected by the parameters, gradient, speed, road curvature, road roughness, congestion, road elements and weather. The result of the investigation of attributes in the NVDB is displayed with respect to green routing. The relevance measure in the first literature search was assumed to be higher if the number of relevant articles were high. The results of the second literature search were discussed with respect to green routing. This was followed by suggesting eventual improvements in the NVDB and improvements in the method used in this thesis. Furthermore, the parameters usage and implementation in GIS were discussed. It was concluded that all parameters found in the second literature search except weather were appropriate for green routing. Other parameters could also have an effect on the fuel consumption of heavy trucks but further research is necessary to investigate this.

For internal combustion engines used in heavy-duty vehicles, increased engine efficiency and consequently reduced CO2 emissions can be obtained if the engine speed can be kept within an optimal speed range. This requires swift and frequent gear shifts where the dry friction clutch is utilized. Enhanced dry clutch simulation models and a better understanding of the involved phenomena can assist the development towards swifter gear shifts and help reduce CO2 emissions. The work presented in this thesis focuses on the modelling of dry clutch systems for heavy-duty applications and their effect on the torsional response of the driveline during transient events such as clutch engagement and disengagement. During these events it is primarily the first vibration mode of the driveline that is active and consequently it is possible to greatly reduce theof degrees of freedom (DOFs) of the powertrain model and still capture the relevant dynamics of the powertrain. The reduced set of differential equationsdescribe the torsional motion of the powertrain and the equations of motion are solved numerically in the time-domain. From a mathematical point ofview, the equations of motion turn "stiff" when the clutch is locked. This issue is resolved by utilizing numerical solution techniques suitable for stiff differential equations. In the simulations it was observed that no engine torque fluctuations were transferred through the slipping clutch. Consequently the response of the driveline is purely modal during sliding. If the gradient of the coefficient of friction is negative the modal response is possibly unstable with exponentially growing vibration amplitudes as an effect. Moreover, the way in which the clamp load evolves during clutch engagement is found to severely effect the excitation of transient vibrations during clutch synchronization. It can be shown that reducing the gradient of the evolving clamp load at the onset of sliding will reduce the amplitude of the friction induced vibrations. Reducing the torsional vibration amplitudes will help avoid the jerky motion of the vehicle during launch and increase comfort for driver and passengers. / Reduced transmission vibrations - reduced energy consumption and environmental impacts together with an increased competitiveness. Swedish Energy Agency (project No. 42100-1)

This research investigates a novel arrangement to pneumatic suspensions that are commonly used in heavy trucks, toward providing a dynamically balanced system that resists body roll and provides added roll stability to the vehicle. The new suspension, referred to as "balanced suspension," is implemented by retrofitting a conventional pneumatic suspension with two leveling valves and a symmetric plumbing arrangement to provide a balanced airflow and air pressure in the airsprings. This new design contributes to a balanced force distribution among the axles, which enables the suspension to maintain the body in a leveled position both statically and dynamically. This is in contrast to conventional heavy truck pneumatic suspensions that are mainly adjusted quasi-statically to level the body in response to load variations. The main objectives of the research are to discover and analyze the effects of various pneumatic components on the suspension dynamic response and numerically study the benefits of the pneumatically balanced suspension system. A pneumatic suspension model is established to capture the details of airsprings, leveling valves, check valves, pipes, and air tank based on the laws of fluid mechanics and thermodynamics. Experiments are designed and conducted to help determine and verify the modeling parameters and components. Co-simulation technique is applied to establish a multi-domain model that couples highly non-linear fluid dynamics of the pneumatic suspension with complex multi-body dynamics of an articulated vehicle. The model is used to extensively study effects of pneumatic balanced control of the suspensions on the tractor and trailer combination dynamics. The simulations indicate that the dual leveling valve arrangement of the balanced suspension provides better adjustments to the body roll by charging the airsprings on the jounce side, while purging air from the rebound side. Such an adjustment allows maintaining a larger difference in suspension force from side to side, which resists the vehicle sway and levels the truck body during cornering. Additionally, the balanced suspension better equalizes the front and rear drive axle air pressures, for a better dynamic load sharing and pitch control. It is evident from the simulation results that the balanced suspension increases roll stiffness without affecting vertical stiffness, and thereby it can serve as an anti-roll bar that results in a more stable body roll during steering maneuvers. Moreover, the Failure Mode and Effects Analysis (FMEA) study suggests that when one side of the balanced suspension fails, the other side acts to compensate for the failure. On the other hand, if the trailer is also equipped with dual leveling valves, such an arrangement will bring an additional stabilizing effect to the vehicle in case of the tractor suspension failure. The overall research results presented show that significant improvements on vehicle roll dynamics and suspension dynamic responsiveness can be achieved from the balanced suspension system. / PHD

<p>In an automated manual transmission it is desired to have zero torque in the transmission when disengaging a gear. This minimizes the oscillations in the driveline which increases the comfort and makes the speed synchronization easier. The automated manual transmission system in a Scania truck, called Opticruise, uses engine torque control to achieve zero torque in the transmission.In this thesis different control strategies for engine torque control are proposed in order to minimize the oscillations in the driveline and increase the comfort during a gear shift. A model of the driveline is developed in order to evaluate the control strategies. The main focus was to develop controllers that are easy to implement and that are robust enough to be used in different driveline configurations. This means that model dependent control strategies are not considered.A control strategy with a combination of a feedback from the speed difference between the output shaft speed and the wheel speed, and a feedforward with a linear ramp, showed very good performance in both simulations and tests in trucks. The amplitude of the oscillations in the output shaft speed after neutralengagement are halved compared to the results from the existing method in Scania trucks. The new concept is also more robust against initial conditions and time delay estimations.</p>