No abstract

The paper describes a novel algorithm for solving the synthesis problem of a multi-link wheel-guiding mechanism with a known topology and dimension. The synthesis objectives contain the elastokinematical specifications, described by a set of spatial displacements that the wheel carrier should undergo from a design position under specified loads corresponding to typical car manoeuvres. Radial spring rates of cylindrical elastomeric bushings, embodied in the suspension rods, are considered as design variables. Relations between the design variables and the objectives are established using the first-order kinematics and screw calculus, under assumptions about small displacements and linear force-deflection characteristics of the flexible elements. The problem is solved by using a constrained linear least-squares algorithm. Depending whether the input data is provided by a designer or acquired during suitable experiments, the algorithm can be used for synthesis or estimation of the stiffness parameters. Numerical examples are solved for two five-rod suspensions, with the same topology but different configuration and dimension, installed at rear-driven axles of actual cars. Static spring rates of the five rod-bushings are determined, for which both suspensions satisfy the formulated ride/handling criteria in the best way. Fundamental characteristics and limitations of the suspensions are described.

The paper presents an innovative method for a lap time minimisation by using genetic algorithms for a multi objective optimisation of a race driver-vehicle model. The decision variables consist of 16 parameters responsible for actions of a professional driver (e.g. time traces for brake, accelerator and steering wheel) on a race track part with RH corner. Purpose-built, high fidelity, multibody vehicle model (called 'miMa') is described by 30 generalised coordinates and 440 parameters, crucial in motorsport. Focus is put on modelling of the tyre tread thermodynamics and its influence on race vehicle dynamics. Numerical example considers a Rear Wheel Drive BMW E36 prepared for track day events. In order to improve the section lap time (by 5%) and corner exit velocity (by 4%) a few different driving strategies are found depending on thermal conditions of semi-slick tyres. The process of the race driver adaptation to initially cold or hot tyres is explained. ARTICLE HISTORY

The paper presents optimization of 5-rod (5-link) suspension mechanism used in passenger cars for independent guiding of the wheels. Selected stiffness coefficients defined for five elastomeric bushings installed in joints of the suspension rods are considered as design variables. Two models with lumped parameters (i.e. elastokinematic and dynamic) of wheel-suspension-car body system are formulated to describe relationships between the design variables and the performance indexes including car active safety and ride comfort, respectively. The multi-criteria goal function is minimized using a deterministic algorithm. The suspension with optimized bushings rates fulfils desired elastokinematic criteria together with a defined dynamic criterion, describing the so-called rolling comfort. An event of car passing over short road bump is considered as dynamic conditions. The numerical example deals with an actual middle-class passenger car with 5-rod suspension at the front driven axle. Estimation of the models parameters and their verification were carried out on the basis of indoor and outdoor experiments. The proposed optimization procedure can be used to improve the suspension design or development cycle.

No abstract