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In this study, the enhancement of road friendliness of Heavy Goods Vehicle is investigated using two methods to control the resonant forces: (i) Determination of optimal asymmetric force velocity characteristics of the suspension dampers to control the wheel forces corresponding to the resonant modes; (ii) Optimal design of an axle vibration absorber to control the wheel forces corresponding to the unsprung mass resonance mode. An analogy between the dynamic wheel loads and ride quality performance characteristics of heavy vehicles is established through analysis of an in-plane vehicle model. A weighted optimization function comprising the dynamic load coefficient (DLC) and the overall rms vertical acceleration at the driver's location is formulated to determine the design parameters of the damper and absorber for a range of vehicle speeds. The results show that implementation of tuned axle absorbers can lead to reduction in the DLC ranging from 11.5 to 21%.

A covariance analysis technique is proposed to derive the optimal suspension parameters of an articulated freight vehicle. A performance criteria comprising vehicle ride response, suspension deflections and tire deflections related to dynamic wheel loads, is formulated for the 9 degrees-of-freedom (DOF) in-plane model of the vehicle. The range of suspension parameters to achieve four different design requirements is identified and a parametric study is performed to make initial parameter selection using the covariance analysis. The optimal suspension parameters are then identified from the results of the study. The study concludes that the proposed technique can yield the optimal solution in a convenient and highly efficient manner.

This paper discusses the design of an electrohydraulic force loading system. This system is able to produce any desired arbitrary forces. As an example, the loading system is designed to load force to a hydraulic position servo. It is shown that if the loading system is designed by using a combination of a servo valve with critical center and a hydraulic cylinder to realize a force feedback close-loop system, the position system may generate a large additional force to frustrate this loading system to work properly. By using a bypass adjustable throttle valve across the two flow lines of the loading cylinder, it is verified by theoretic analysis and simulation that the additional force generated by position system can be greatly reduced. Because an asymmetric cylinder is used as the loading actuator, modelling of its characteristics is also carried out.