Combined emergency braking and turning of articulated heavy vehicles

Abstract

'Slip control' braking has been shown to reduce the emergency stopping distance of an experimental heavy goods vehicle by up to 19%, compared to conventional electronic/anti-lock braking systems (EBS). However, little regard has been given to the impact of slip control braking on the vehicle's directional dynamics. This paper uses validated computer models to show that slip control could severely degrade directional performance during emergency braking. A modified slip control strategy, 'attenuated slip demand' (ASD) control, is proposed in order to rectify this. Results from simulations of vehicle performance are presented for combined braking and cornering manoeuvres with EBS and slip control braking with and without ASD control. The ASD controller enables slip control braking to provide directional performance comparable with conventional EBS while maintaining a substantial stopping distance advantage. The controller is easily tuned to work across a wide range of different operating conditions.

Sideslip estimation for articulated heavy vehicles at the limits of adhesion

“…The FUKF outperformed the linear KF, producing sideslip estimate that was qualitatively similar to the RT3022 measurement, though still with significant quantitative error. Previous work [6] had revealed that when operating with lateral tyre slip only, the Fancher model could simulate the test vehicle's tyre forces on wet basalt tile surfaces with reasonable accuracy. However, significant mismatch between the model and test vehicle was found to occur under combined slip conditions.…”

“…Brief descriptions of the test vehicle and experiments are provided later. Refer to [6] for further detail. Figure 9 shows a photograph of the test vehicle and a schematic of the relevant instrumentation installed.…”

“…Figure 3 illustrates the simulation set-up in Simulink. A previously validated nonlinear model of a tractor-semitrailer [6,8] was used to simulate the plant. This 16 DoF yaw-roll model is two-track, includes lateral and longitudinal load transfers and uses the nonlinear Fancher truck tyre model.…”

“…It has been shown to achieve stopping distance reductions of up to 19% compared to a conventional HGV anti-lock braking system, however in doing so it almost entirely saturates the tyres and leaves very little capacity for lateral forces to be generated. [6][7][8] The tractor unit was fitted with an Oxford Technical Solutions RT3022 inertial navigation system. The six-axis inertial sensor and processing unit of the RT3022 was mounted as close as possible to the CoG location of the tractor (determined by weighing the axles when the tractor was decoupled from the trailer).…”

“…[6][7][8] Sideslip cannot be measured directly using standard inexpensive sensors, therefore it must be estimated based on other available sensor information.…”