A novel coupling strategy for automated vehicle’s longitudinal dynamic stability

Abstract

The autonomous vehicle has been developed widely, and attracted much attention of global automotive industry. Wherein, longitudinal dynamics control is one of the most crucial issues of autonomous vehicles. The throttle-by-wire (TBW) control could implement the acceleration command through adjusting the throttle opening, thus control the driving torque of the fuel autonomous vehicle. However, an automated vehicle controlled by traditional TBW in low-friction road conditions could reach large slip ratio region, which could adversely cause the loss of vehicle longitudinal dynamic stability. To tackle the mentioned issues, this paper proposes an adaptive sliding-mode control (SMC) algorithm to optimize tire slip speed of the automated vehicle. When the intervention conditions of active acceleration are satisfied, the TBW can take over the throttle opening control instead of the driver. Firstly, the SMC can calculate an intervention of the effective torque input based on tire torque balance dynamics. Moreover, a traction control system (TCS) and TBW coupling strategy based on the logic threshold method is put forward to response the optimum slip speed curve. Thus, during the vehicle starting process, a three-layer control strategy consisting of TBW, torque control, and pressure control of TCS is involved. Finally, real-car snow and ice road tests are carried out, and experimental results demonstrate great performance of the proposed strategy in complicated low-friction road.