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 / Over the last decade or so, air suspension has been widely equipped on heavy truck for a better ride and height control. The conventional air suspension employs one leveling valve to adjust airspring pressure in order to maintain ride height for various loads, which, however, hardly provides roll stability control when a truck undergoes a turn, accelerating, or breaking. A new air suspension system, referred to as balanced suspension, is proposed by implementing two leveling valves and a symmetric plumbing arrangement. The suspension pneumatics are designed to provide balanced air flow and pressure in the airsprings such that they are able to better respond to truck body motion in real time. The main objective of this research is to provide a simulation evaluation of the effect of maintaining the balanced airflow in heavy truck air suspensions on vehicle roll stability. The analysis is performed based on a complex model including fluid dynamics of the pneumatic suspension and multi-body dynamics of the heavy truck. Experiments are conducted to determine some parameters necessary for the modeling and to provide verification for the pneumatic suspension model. The simulation results show that, as a truck performs a cornering, the proposed balanced suspension can supply air to the compressed suspension while purging air from the extended suspension. These adjustments result in balanced suspension force to improve the dynamic responsiveness of the suspension to steering, causing less body roll, in comparison with the conventional air suspension. Additionally, the Failure Mode and Effects Analysis (FMEA) study indicates that one-side component failure of the balanced suspension does not completely disable the system, the unaffected side works to keep the system functioning until the failure is corrected. Overall research results suggest that the truck roll dynamics and suspension dynamic responsiveness are improved for the balanced suspension. Moreover, this study contributes to a simulation platform that can serve as an effective virtual design and simulation tool for analyzing, improving, and engineering the pneumatic suspension system.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/95168 |
| Date | 03 May 2017 |
| Creators | Chen, Yang |
| Contributors | Mechanical Engineering, Ahmadian, Mehdi, Southward, Steve C., Taheri, Saied, Jazizadeh, Farrokh, Dancey, Clinton L. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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