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The dynamic stability of long combination vehicles (LCVs) is an important part of vehicle safety. An LCV, its driver and the road constitute a unique closed-loop dynamic system. Assessing the dynamic stability is difficult due to the complex interactions of driver-tractor-trailers-road. Rearward amplification (RA) is an effective performance measure of the dynamic stability; various methods are applied for evaluating the RA. However, the measures from different methods may differ significantly. What are the root causes for the disparity of evaluation results? This paper tackles the problem by investigating the typical methods for evaluating the measure of two LCVs, i.e. an A-train double and a B-train double. To this end, simulations of the LCVs are conducted using TruckSim software. The study discloses the main causes for the disparity of the measures from different methods, and recommends the effective approaches to the assessment of the RA. [ABSTRACT FROM AUTHOR]

The Society of Automotive Engineers issued a test procedure, SAE-J2179, to determine the rearward amplification (RA) of multi-trailer articulated heavy vehicles (MTAHVs). Built upon the procedure, the International Organization for Standardization released the test manoeuvres, ISO-14791, for evaluating directional performance of MTAHVs. For the RA measures, ISO-14791 recommends two single lane-change manoeuvres: (1) an open-loop procedure with a single sine-wave steering input; and (2) a closed-loop manoeuvre with a single sine-wave lateral acceleration input. For an articulated vehicle with active trailer steering (ATS), the RA measure in lateral acceleration under the open-loop manoeuvre was not in good agreement with that under the closed-loop manoeuvre. This observation motivates the research on the applicability of the two manoeuvres for the RA measures of MTAHVs with ATS. It is reported that transient response under the open-loop manoeuvre often leads to asymmetric curve of tractor lateral acceleration [Winkler CB, Fancher PS, Bareket Z, Bogard S, Johnson G, Karamihas S, Mink C. Heavy vehicle size and weight – test procedures for minimum safety performance standards. Final technical report, NHTSA, US DOT, contract DTNH22-87-D-17174, University of Michigan Transportation Research Institute, Report No. UMTRI-92-13; 1992]. To explore the effect of the transient response, a multiple cycle sine-wave steering input (MCSSI) manoeuvre is proposed. Simulation demonstrates that the steady-state RA measures of an MTAHV with and without ATS under the MCSSI manoeuvre are in excellent agreement with those under the closed-loop manoeuvre. It is indicated that between the two manoeuvres by ISO-14791, the closed-loop manoeuvre is more applicable for determining the RA measures of MTAHVs with ATS. [ABSTRACT FROM PUBLISHER]

This paper presents the design for an active trailer-steering system of multi-trailer articulated heavy vehicles using driver-software-in-the-loop real-time simulations. A linear yaw-plane multi-trailer articulated heavy-vehicle model is generated to derive an optimal active trailer-steering controller. Then, the controller is reconstructed in LabVIEW and integrated with a vehicle model for a tractor– double-trailer combination developed in TruckSim. The driver-software-in-the-loop real-time simulations are conducted on a vehicle simulator. The driver-software-in-the-loop real-time simulations indicate that the active trailer-steering controller can effectively improve the low-speed manoeuvrability and high-speed stability of the multi-trailer articulated heavy vehicle when testing using a low-speed 360° roundabout path-following manoeuvre and a high-speed single-lane-change manoeuvre respectively. The investigation based on the driver-software-in-the-loop real-time simulations paves the way to future development of electronic control units for the active trailer-steering system using driver-hardware-in-the-loop real-time simulations. [ABSTRACT FROM AUTHOR]

This paper presents a closed-loop dynamic simulation-based design method for articulated heavy vehicles (AHVs) with active trailer steering (ATS) systems. AHVs have poor manoeuvrability at low speeds and exhibit low lateral stability at high speeds. From the design point of view, there exists a trade-off relationship between AHVs’ manoeuvrability and stability. For example, fewer articulation points and longer wheelbases will improve high-speed lateral stability, but they will degrade low-speed manoeuvrability. To tackle this conflicting design problem, a systematic method is proposed for the design of AHVs with ATS systems. In order to evaluate vehicle performance measures under a well-defined testing manoeuvre, a driver model is introduced and it ‘drivers’ the vehicle model to follow a prescribed route at a given speed. Considering the interactions between the mechanical trailer and the ATS system, the proposed design method simultaneously optimises the active design variables of the controllers and passive design variables of the trailer in a single design loop (SDL). Through the design optimisation of an ATS system for an AHV with a truck and a drawbar trailer combination, this SDL method is compared against a published two design loop method. The benchmark investigation shows that the former can determine better trade-off design solutions than those derived by the latter. This SDL method provides an effective approach to automatically implement the design synthesis of AHVs with ATS systems. [ABSTRACT FROM PUBLISHER]

This paper presents a method for quantifying drivers' driving skills using closed-loop dynamic simulations of articulated heavy vehicles (AHVs). Due to AHVs' multi-unit configurations, large sizes, and high centers of gravity (CGs), these large vehicles exhibit poor directional performance. AHVs require wide roads and large radii of path curvature for evasive maneuvers; these large vehicles frequently display unstable motion modes, including trailer sway, jackknifing, and rollover. The directional performance of AHVs is frequently evaluated in terms of maneuverability and lateral stability. There exists a trade-off between the performance measures of maneuverability and lateral stability. An AHV, its driver and the road constitute a unique closed-loop dynamic system. The unique dynamic characteristics of AHVs impose significant challenges for safe operations of these vehicles. However, little attention has been paid to the interactions of driver-AHV. This paper tackles the problem of quantifying drivers' driving skills considering the interactions of driver-AHV under simulated single lane-change (SLC) maneuvers. Based on two driver characteristic parameters, namely preview time (PT) and transport delay (TD), we propose two performance measures, i.e., path-following score (PFS) and combined stability score (CSS), as the indicators for assessing the driving skills of AHV drivers under the simulated maneuvers. The driver-AHV closed-loop dynamic simulation is implemented using the built-in driver model and virtual vehicles developed in TruckSim. The numerical simulation results for rearward amplification (RA) measures are validated using driver-in-the-loop (DIL) real-time simulation. The simulation identifies AHV drivers' driving skills in terms of lateral stability, path-following, as well as balanced path-following and stability regions considering PT and TD properties. [ABSTRACT FROM AUTHOR]