Anti-lock braking system based on FlexRay protocol
The anti-lock braking system is nowadays a part of almost every vehicle. This system increases safety of the people sitting in the vehicle at the moment of stopping on a slippery or unstable road surface. The point is to assure a good controllability of the vehicle even if the wheels are in slip. In order to work properly, the anti-lock braking system needs to have actual information about the rotation of every single wheel. And the up-to-dateness and certainty of an accurate information is the primary criterion of an appropriate performance. Currently, the information about the frequency of wheel rotation is being transmitted via the current loop. This solution needs a lot of wiring, which means increased purchase costs. This paper describes a method, where the information from the rotation sensors of the wheels are transmitted into the control unit through the FlexRay bus. Additional wireless acceleration sensors located on the wheel are used to improve the ABS performance.
The Influence of In-Plane Tyre Dynamics on ABS Braking of a Quarter Vehicle Model
For efficient analysis it is important to choose the proper model that fits the problem that needs to be solved. This paper discusses three pragmatic simulation models for longitudinal behaviour of a passenger car tyre (Steady State, Transient and Rigid Ring) that may be used in e.g. an ABS simulation. The characteristics of the simulation models are evaluated using some simple simulations. Simulations with a quarter vehicle model that includes load transfer effects are carried out to determine the deviation in results between the mentioned tyre models for an ABS application. The results show that the Steady State model may only be used below 10 Hz and that the Transient model is valid up to about 30 Hz. The results from the ABS simulation with the Rigid Ring model are most reliable and are clearly different from the Steady State and Transient model, which indicates that ABS simulations should be carried out with the Rigid Ring model. Additionally it is demonstrated that for tyre behaviour on uneven roads the influence of the tyre belt cannot be neglected.
Damage initiation and propagation in composite shells subjected to impact
Abstract The paper investigates the impact-induced damage initiation and propagation for laminated composite shells under low-velocity impact. A three-dimensional eight-node non-conforming element is described to analyze interlaminar stress distribution, and progressive failure. The damage analysis is performed by using Tsai–Wu quadratic failure criterion, Tsai’s damage modes and an additional delamination formula at all Gaussian points. The damage modes considered are matrix cracking, fiber breakage and delamination. The progressive failure is expressed by reducing stiffness of the material at all failed Gaussian points. Special attention is centered on curved laminates. Impact energy threshold for the onset of damage and transient damage size are predicted for composite shells. The analyses of the flat and curved laminates are compared for discussing their different damage mechanism. In addition, the influence of the stacking sequence, the thickness and the radius of curvature on damage behavior of composite shells are studied.