Trajectory Generation From Paths for Autonomous Ground Vehicles

Path-to-trajectory conversion problem for car-like autonomous ground vehicles has been studied in various ways. It is challenging to generate a trajectory which is dynamically feasible for the vehicle and comfortable for the passengers. An important practical concern of low computational costs makes the problem even more difficult. In this work, a path-to-trajectory converter is developed using a novel receding-horizon type suboptimal algorithm. By transforming the dynamic constraints to a longitudinal velocity limit function in the velocity-acceleration phase plane, a time-sub-optimal trajectory satisfying the dynamic constraints and the initial boundary condition is generated by computing the maximum constant acceleration in the down-range horizon. The portion of the trajectory approaching the end of the path is generated in reverse time. As illustrated by some simulation results and validation on a full-scale Kia Soul EV, the proposed path-to-trajectory conversion algorithm is able to account for dynamic constraints of the vehicle and guarantees passenger comfort.

Comparison between analytical, numerical, and experimental results of grouping effects in droplet streams

Grouping of droplets was studied in monodisperse droplet streams. This very controllable system allows to studybasic effects. In experiments droplet streams with monodisperse droplets were generated, however, with initially two different inter droplet spacing. A larger inter droplet spacing is followed by a little bit smaller one, which is followed by a larger one and so on. Due to this initial boundary condition groups of two droplets form, which approach each other and finally coagulate. It was found, that the velocity of the droplet approach is linearly dependent on the spacing between the droplets. This process was simulated by direct numerical simulation using the in-house code FS3D. The results of the simulations show the ame linear behaviour. For larger computational domains thenumerical results approach the experimental results.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4685

Shape Optimization of Metal Welded Bellows Seal Based on the Turing Reaction-Diffusion Model Coupled with FEM

In this paper, the Turing reaction-diffusion model coupled with Finite Element Method (FEM) is implemented first by considering the biomechanical model iBone (Imitation Bone). Then the shape optimization of Metal Welded Bellows Seal (MWBS) is conducted based on the biomechanical bone forming process by considering the osteoclasts and osteoblasts process. The MWBS mass and shape is changed by changing the initial boundary condition, then some reasonable results are obtained by keeping the required forming value, and the new S type wave of metal welded bellow of mechanical seal are obtained. Finally, the strength evaluations are conducted for new optimized S type model and original V and S type models by using the FEM software.

Comparison of the Structures of a Perturbed and Unperturbed Boundary Layer of the Same Reynolds Number

The comparison of the structures of the boundary layer with and without suction of the same momentum thickness Reynolds number Rθ have been made in a turbulent boundary subjected to concentrated suction, applied through a short porous wall strip. The results indicate that, relative to σ = 0, the mean velocity collapses reasonably well but there are some discrepancies in the Reynolds stresses distributions. These discrepancies are also noted in the distributions of the anisotropy invariant tensor, skewness and flatness factors. The result would suggest that the differences are a result of the difference in the initial boundary condition, which influences the flow structures to a significant streamwise location.

Linear parabolic equations with venttsel initial boundary conditions

The Schauder estimates for solutions of linear second order parabolic equations with Venttsel initial boundary conditions are proved, and existence and uniqueness of classical solutions under such an initial boundary condition are established. An application to an engineering problem is also given.

Magnetic field intensification and formation of field-aligned current in a non-uniform magnetic field

A study is made of the induction of a direct field-aligned current due to Alfvén waves excited through an initial–boundary condition for an incompressible fluid with high conductivity in a non-uniform magnetic field. A simple but exact case is considered in which the direction of inhomogeneity of the magnetic field is perpendicular to that of the shear fluid motion at the boundary, and the fluid moves across the magnetic field. The boundary does not satisfy the frozen-flux condition, but has a large Lundquist number. The conductivity of the fluid held between the two boundaries is high, and the frozen-flux condition is approximately satisfied there. A preflare stage of the sun is investigated, and a reasonable magnetic field intensity and d.c. field-aligned current in the magnetic arcade are obtained for a given horizontal shear motion that is antisymmetric at both boundaries of the arcade foot points, taking account of the observed horizontal fluid motion.