engleski

Analysis and Optimization of Low Floor Vehicle Steering System Configuration

The paper describes the development of multifunctional low floor vehicle (GVW 6000 kg) steering system, for the front steering axel with an independent suspension with a McPherson strut and a bottom transverse link. The axel capacity is 3600 kg. During development the priority was to fit the steering system in the available space, while achieving better ground clearance at the same time. Furthermore, in order for the vehicle to have better manoeuvring ability in narrow streets, it was the maximal steer angle of the inner wheel had to reach 50°. From the aspect of production efficiency, already manufactured components available on the market were to be used as much as possible. In those conditions the aim was to develop a steering system with rotating levers and if possible totally straight rods, driven by a standard hydraulic steering gear. For these demands possible steering system configurations were selected and analyzed, and the most suitable one was chosen. Further development of the chosen steering system includes the elaboration of its kinematics. In case of the steering system combined with the independent suspension, vertical motion of the wheel affects the position of the steering system rods. It is important that the steering rods follow steer angle, in order to avoid possible unwanted steer angle changes due to the upward and downward deflections of the wheel. The positions of vehicle suspension joints on the transverse vertical plain through the front axel defines the positions of steering system joints on the same plain. The positions of steering system joints on the transverse vertical plain of the front axel were determined by implementing the virtual centres procedure. Although the position of the joints on the horizontal plain is generally defined by the design of the vehicle's front axel and the steering system itself, their optimal positions are determined by implementing the flexible polyhedron method. Optimization is carried out using the criteria of minimal differences between the actual steer angle curve and the Ackermann's curve. That determines the positions of joints of the steering system, in accordance with the given geometrical limits. Diagrams are used to show differences between the actual steer angle curve and the Ackermann's curve, before and after the optimization process.

steering system; Ackermann’s curve; optimization; virtual centres procedure; flexible polyhedron method

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