Fault Tolerant Autonomous Lateral Control for Heavy Vehicles

This report summarizes the research results of TO4233, "Fault Tolerant Autonomous Lateral Control for Heavy Vehicles". This project represents a continuing effort of PATH's research on Automated Highway Systems (AHS) and more specifically in the area of heavy vehicles. Research on the lateral control of heavy vehicles for AHS has been going on at PATH since 1993. MOU129, "Steering and Braking Control of Heavy Duty Vehicles" was the first project and it was followed by MOU242, "Lateral Control of Commercial Heavy Duty Vehicle". Both projects were concerned mostly with the theoretical portion of the problem, i.e. model development, analysis of the dynamic model from the lateral control point of view, and the lateral controller designs. The first experimental results were shown in MOU289 (MOU313), "Lateral Control of Heavy Duty Vehicles for Automated Highway Systems", where the theoretical model was validated and calibrated to the dynamic behavior of an actual tractor-semitrailer vehicle, which was obtained and instrumented. In addition, preliminary closed-loop experiments were performed. A more comprehensive study on a large variety of control strategies was presented in MOU385 and TO4201, "Robust Lateral Control of Heavy Duty Vehicles". More specifically, three types of nonlinear and adaptive controllers for lateral control of heavy vehicles were analyzed theoretically and compared experimentally. All the research efforts mentioned above have been extremely valuable for the development of automated highway vehicles; however they assume the existence of a fully operational magnet-magnetometer scheme. To be more specific, all the results are based on the assumption that each heavy vehicle is equipped with two banks of magnetic sensors, one mounted on the front bumper and the other mounted on the rear bumper of the trailer. The road is also implanted with equally spaced magnets whose magnetic field is used to measure the vehicle's lateral deviation from the road centerline ("lane-keeping control"). Up to now, no heavy-vehicle-related report has discussed the case of vehicle lateral performance under the existence of faults. This problem is very important, since safety and reliability are the primary requirements for the success of AHS. This report addresses the problem of fault tolerant control of heavy vehicles by proposing a secondary system that implements "autonomous vehicle following" instead of "lanekeeping".