Optimization of Front Axle Suspension System of Articulated Dump Truck

Manufacturers of construction machinery are challenged to accommodate legal requirements on the vibration exposure associated with their products. For such machines a crucial performance parameter is the whole body vibration level that the operator is subjected to.

This paper presents results from ongoing research collaboration between Hydrema Produktion A/S, Aalborg University and the University of Agder on comfort improvement. The main goal of the research project is to improve ride comfort of articulated construction machinery by use of multibody simulation models.

In this paper the application that has been subjected to comfort improvement is a two axle articulated dump truck. The comfort has been in terms of whole body vibration exposure and the overall improvement has been made possible by adding front axle suspension. However, a hydraulic stabilizing system between the tractor and trailer of the machine and the varying load distribution when turning the steering wheel has revealed a non-trivial task of sizing the new suspension system in an optimal way.

Hydraulic accumulators and valves are used as suspension elements. The topology of the suspension frame is given together with a work cycle used to evaluate the whole body vibrations.

By use of a multibody simulation model of the dump truck the whole body vibration exposure has been computed using the predefined work cycle as model input. The design parameters comprise the components of the hydraulic subsystem of the suspension, i.e., the size of the hydraulic accumulators and the initial gas pressure as well as the size of the damping orifices. The design criteria has been the comfort as evaluated from the typical work cycle with a number of side constraints such as availability of components, available space, collision avoidance and design rules given by the supplier of accumulators.

A non-gradient optimization routine has been applied to determine the optimal design, i.e., the design with the best possible ride comfort in terms of whole body vibrations that does not violate any of the constraints. Some variables have been treated as discrete such as the accumulator volume. In general, the results have been encouraging and may be used directly as guidelines in both current and future design.