An evasive manoeuvre assist function for over-reactive drivers

Abstract: Previous studies have shown that many drivers are unable to provide the right amount of steering torque when facing an imminent collision with an upcoming obstacle. In some cases, drivers under-react i.e., they provide too low steering inputs and thus collide with the obstacle in front; in other cases, drivers might apply a higher steering input than necessary, potentially resulting in the vehicle leaving the road or losing stability. The EMA function is an active safety feature which has the sole objective of providing steering torque interference when performing such a manoeuvre. The motivation for the thesis work is to overcome some limitations of the existing MA function which does not incorporate the ability to differentiate driver reactions. In this thesis, an Evasive Manoeuvre Assist (EMA) function is designed to adapt to both types of the drivers, by an optimised steering torque overlay. The existing current EMA function is always amplifying the driver steering inputs using a feed-forward controller. The focus of this thesis work is to identify and dene a proper steering sequence reference model for closed-loop feedback control design. A simple single-point preview model is designed first to calculate the reference steering angle. A few test scenarios are set-up using the IPG CarMakerTMsimulation tool. The reference model is then tuned with respect to the amplitude and frequency by batch simulations to obtain the optimal steering prole. A feedback controller is then designed using this reference model. The controller is implemented in a real-time environment, using a Volvo rapid-prototype test vehicle. Preliminary variation tests have shown that the developed controller can enhance both an over-reacting and under-reacting driver's performance during an evasive manoeuvre, by applying assistance/resistance EPAS torque timely. The designed EMA function is shown to accommodate different driver reactions and provide intuitive torque interference. As opposed to the earlier notion that the EMA function only assists the driver with an additional steering wheel torque, it was shown that the optimal steering torque overlay might be in the form of assistance or resistance.