Optimal Control Concepts for the Characterization and Design of Highway Vehicle-Trailer Systems

Abstract

Recent years have seen enormous increases in the use of vehicle-trailer systems for commercial transport as well as personal/recreational use. Indeed, entire new industries and concepts have developed, along with questions pertaining to safety, legislation, etc. and the design of such systems. One problem in evaluating the design and operating-range performance of such systems is the identification of one or a few pertinent criteria for comparison and suitable characterizations of the relative stability and performance of these systems. In this paper, design concepts are developed from optimal control theory to provide such criteria and are then applied to one of the more innovative and potentially competitive concepts in commercial trucking: the multiple-trailer highway vehicle train. The definition of relevant models is given and criteria are then developed. Their applicability is demonstrated by the posing of optimal unloading schedules to improve dynamic performance, the sensitivity of such designs to changes in system parameters, and the design synthesis of couplers between the system components. The comparison of these systems with equivalent (in terms of load capacity) single-trailer systems is also indicated. The problem of discrete compartmented trailers is also addressed; this case can be viewed as a multi-stage dynamic programming problem. Obviously, the modeling is safer, less costly and time consuming than present prototype developmental procedures. The criteria developed are extremely general and appear to provide a basis for developing a systematic approach to the design of such systems for safety and dynamical behavior as well as for capacity. As it turns out, alternate and unexpected schedules and different designs can yield substantially improved behavior—and the results are not intuitively obvious.