Sogol Kharrazi

Study of heavy truck accidents with focus on manoeuvres causing loss of control

An analysis of heavy truck accidents based on the Large Truck Crash Causation Study database with respect to loss of control is presented. Heavy truck accidents were analysed with regard to the accident type, loss of control type, critical manoeuvre, vehicle combination type and different road characteristics. Three critical manoeuvres were identified as the most common manoeuvres causing loss of control. Based on the accident analysis results, relevant existing test manoeuvres were adapted for trucks and compared to determine a suitable test for evaluation of yaw stability of heavy trucks on a dry and level road. The comparison was conducted on a 5DOF tractor-trailer model in Matlab-Simulink.

Proposal for using Sine With Dwell on low friction for the evaluation of yaw stability for heavy vehicle combinations

This paper proposes how the test case Sine With Dwell could be modified for the evaluation of yaw stability of heavy vehicles. The test case was originally proposed by the National Highway Traffic Safety Administration (NHTSA) for evaluation of Electronic Stability Programs (ESP) performance during an oversteer situation on high friction. The modified test case presented here accounts for the heavy vehicle dynamics through three main modifications of the original test case. Firstly, to avoid rollover, the test case is performed on low friction. Secondly, to avoid excess understeer behaviour, the steering input frequency is lowered compared to the original test. Thirdly, to account for response times, the responsiveness and stability criteria are modified. These modifications are derived from hardware in the loop simulations and field tests for different tractor/truck and trailer combinations. By using the modified responsiveness and stability criteria it was shown that the tested ESP system could be objectively evaluated. A clear improvement on vehicle stability was seen in the results when ESP was used.

Implementation of active steering on longer combination vehicles for enhanced lateral performance

A steering-based controller for improving lateral performance of longer combination vehicles (LCVs) is proposed. The controller steers the axles of the towed units to regulate the time span between the driver steering and generation of tyre lateral forces at the towed units and consequently reduces the yaw rate rearward amplification (RWA) and offtracking. The open-loop effectiveness of the controller is evaluated with simulations and its closed loop or driver in the loop effectiveness is verified on a test track with a truck–dolly–semitrailer test vehicle in a series of single- and double-lane change manoeuvres. The developed controller reduces the yaw rate RWA and offtracking considerably without diminishing the manoeuvrability. Furthermore, as a byproduct, it decreases the lateral acceleration RWA moderately. The obtained safety improvements by the proposed controller can promote the use of LCVs in traffic which will result in the reduction of congestion problem as well as environmental and economic benefits.

A generic controller for improving lateral performance of heavy vehicle combinations

A generic controller for improving the lateral performance of heavy vehicle combinations by steering the axles of the towed units is proposed. The lateral performance of nine heavy vehicle combinations, including conventional combinations and existing and prospective longer combinations, are studied with and without the controller. The performance of the passive vehicles clearly indicates a need for improvements, which can be achieved by the proposed controller. The results obtained for controller verification in the frequency and time domains demonstrate that the controller reduces the yaw rate rearward amplification and off-tracking of all studied vehicles significantly, and diminishes trailer swings without reducing manoeuvrability. Furthermore, as a by-product, it moderately reduces the lateral acceleration rearward amplification. The improvements obtained by the proposed controller can promote the use of longer combination vehicles in traffic, which will result in a reduction of congestion, as well as substantial environmental and economic benefits.

Predictive yaw and lateral control in long heavy vehicles combinations

We consider the problem of controlling the yaw and lateral dynamics in heavy vehicles, consisting of combinations of a truck and multiple towed units. In such heavy vehicle configurations, undesired yaw rate and lateral acceleration amplifications, causing tail swings and lateral instabilities of the towed units, can be observed at high speed. In this paper, we present a predictive control approach to reduce the Rearward Amplification (RWA) of the yaw rate at the rearmost unit in a truck-dolly-semitrailer combination, while bounding the lateral acceleration in order to prevent the roll-over of the rearmost unit. Simulation results with a nonlinear high fidelity vehicle model are presented in a single lane change maneuver, showing that the proposed approach is able to efficiently reduce the yaw rate RWA and limit the lateral accelerations, compared to the uncontrolled vehicle.

The effectiveness of rear axle steering on the yaw stability and responsiveness of a heavy truck

Rear axle steering (RAS) at low speed is available in heavy trucks to improve their manoeuverability and reduce tyre wear; by extending the functionality of the existing RAS to high speed turning and split-mu braking, considerable safety benefits and enhancement in driver comfort can be gained. In this study, a RAS System was developed and simulated in Matlab–Simulink which showed encouraging results. Furthermore, the developed system was implemented on a Volvo Truck and tested in a series of split-mu braking and ISO double lane change manoeuvers. The obtained results conform to the expectations.

Lateral stability control of a long heavy vehicle combination by active steering of the towed units

A complete vehicle combination controller for enhancing the lateral stability of long heavy vehicle combinations by active steering of the towed units is presented. As a case study, the controller is developed for a truck-dolly-semitrailer combination and is evaluated in a sine with dwell maneuver, using a nonlinear model of this combination. The simulation results show a significant decrease in yaw rate rearward amplification and offtracking of the controlled vehicle.

Robustness Analysis of a Steering-Based Control Strategy for Improved Lateral Performance of a Truck-Dolly-Semitrailer

A control strategy for lateral performance improvement of a truck-dolly-semitrailer combination by active steering of the towed units is presented. The effectiveness and robustness of the controller are verified by extensive analysis of the controller performance in various driving conditions at high speeds and presence of uncertainties in vehicle parameters, such as tyre cornering stiffness and moment of inertia. It is shown that the controller reduces the yaw rate rearward amplification, offtracking and side slip angle significantly. It is also demonstrated that brake interventions by other controlling systems such as electronic stability control do not deteriorate the controller performance.

Improving lateral performance of longer combination vehicles — An approach based on eigenstructure assignment

Feasibility of eigenstructure assignment for controlling lateral performance of longer combination vehicles is investigated. As a sample case, a controller is designed for a truck-dolly-semitrailer combination based on partial eigenstructure assignment and frequency response analysis. The results of simulations with a nonlinear vehicle model show significant improvement in lateral performance of the vehicle with the designed controller.