Recreating Existing Railway Horizontal Alignments Automatically Using Overall Swing Iteration

Abstract

The horizontal alignment of existing railway must be re-created and calibrated periodically to meet the requirements of safety, stability and comfort. Most existing re-creation methods perform local section optimization, in which the whole alignment is divided into several sections, depending on the number and positions of intersection points, and then each section is re-created successively. The final whole re-created horizontal alignment is generated by combining optimized re-created sections. In this process, the re-created result of one section must be adjusted in re-creating the next section. Thus, the optimized re-created result of the previous section cannot be preserved. To overcome this problem, some methods use the result of local section optimization as the initial value, and then further optimize the whole alignment. However, the final re-created alignment is affected easily by the local section optimization, so that the re-created alignment is not optimized. This paper proposes an overall swing iteration based on points-alignment consistency integrated with mesh adaptive direct search (MADS). At each iteration, the adverse effect of re-creating successive sections is avoided by preferentially fitting all shared tangents which link nearby sections and then fitting curved segments simultaneously. To optimize curved segments further, MADS is introduced to optimize the parameters and handle constraints. After each iteration, the attributes of measured points for the whole alignment are adjusted based on points-alignment consistency until they are consistent with the attributes of re-created geometric elements. Applications demonstrated that the proposed approach can re-create an optimized horizontal alignment while satisfying multiple constraints.