An adaptive finite element method for computing emergency manoeuvres of ground vehicles in complex driving scenarios

In emergency cases a vehicle has to avoid colliding with one or more obstacles, stay within road boundaries, satisfy acceleration and jerk limits, fulfil stability requirements and respect vehicle system dynamics limitations. The real time solution of such a problem is difficult and as a result various approaches, which usually relax the problem, have been proposed until now. In this study, a new method for computing emergency paths for complex driving scenarios is presented. The method which is based on the finite element concept formulates the dynamic optimisation problem as a linear algebraic one. An empirical formula adapts the size of the finite elements to optimise the dynamics of the emergency path. The proposed approach is evaluated in Matlab and Carsim simulation environments for different driving scenarios. The results show that with the proposed approach complex emergency manoeuvres are planned with improved performance compared to other known methods

KDamping: A Stiffness Based Vibration Absorption Concept

© 2016, © The Author(s) 2016. The KDamper is a novel passive vibration isolation and damping concept, based essentially on the optimal combination of appropriate stiffness elements, which include a negative stiffness element. The KDamper concept does not require any reduction in the overall structural stiffness, thus overcoming the corresponding inherent disadvantage of the “Quazi Zero Stiffness” (QZS) isolators, which require a drastic reduction of the structure load bearing capacity. Compared to the traditional Tuned Mass damper (TMD), the KDamper can achieve better isolation characteristics, without the need of additional heavy masses, as in the case of the T Tuned Mass damper. Contrary to the TMD and its variants, the KDamper substitutes the necessary high inertial forces of the added mass by the stiffness force of the negative stiffness element. Among others, this can provide comparative advantages in the very low frequency range. The paper proceeds to a systematic analytical approach for the optimal design and selection of the parameters of the KDamper, following exactly the classical approach used for the design of the Tuned Mass damper. It is thus theoretically proven that the KDamper can inherently offer far better isolation and damping properties than the Tuned Mass damper. Moreover, since the isolation and damping properties of the KDamper essentially result from the stiffness elements of the system, further technological advantages can emerge, in terms of weight, complexity and reliability. A simple vertical vibration isolation example is provided, implemented by a set of optimally combined conventional linear springs. The system is designed so that the system presents an adequate static load bearing capacity, whereas the Transfer Function of the system is below unity in the entire frequency range. Further insight is provided to the physical behavior of the system, indicating a proper phase difference between the positive and the negative stiffness elastic forces. This fact ensures that an adequate level of elastic forces exists throughout the entire frequency range, able to counteract the inertial and the external excitation forces, whereas the damping forces and the inertia forces of the additional mass remain minimal in the entire frequency range, including the natural frequencies. It should be mentioned that the approach presented does not simply refer to discrete vibration absorption device, but it consists a general vibration absorption concept, applicable also for the design of advanced materials or complex structures. Such a concept thus presents the potential for numerous implementations in a large variety of technological applications, whereas further potential may emerge in a multi-physics environment.status: publishe