Development and Validation of an Automated Steering Control System for Bus Revenue Service

This paper presents the development and validation of an automated steering system that has been successfully implemented on a 18.3-m articulated bus for revenue service in Eugene, OR, USA. The automated steering system provides both lane keeping and S-curve precision docking on a 4-km-long narrow and curving urban segment with six stations and mixed traffic lanes while the operator controls the speed. The objective of deployment with an extended period of revenue service (carrying passengers) elevated the system safety and performance requirements. To meet these requirements, the controller needs to address accuracy, robustness, comfort, and fault tolerant capabilities, while the safety design needs to address functional safety of the automated system. The baseline high-gain controller designed for the automated bus adopts the steering mechanism of human drivers with optimized parameters. The fault tolerant control incorporates a family of Kalman filters to sustain the automation for a few seconds after part of the sensing system fails. The safety design followed the functional safety procedure and employed the combination of redundancy, multilayer fault detection, and comprehensive fault management. The resultant system achieved all performance requirements and the revenue service started in June 2013 and ended in May 2015.