The influence of small rear-wheel steering angles on the stability of automotive vehicle-trailer systems when loaded with rear-ward mass bias

<p dir="ltr">Vehicle towed trailer accidents can cause significant accident damage, often due to poor user training and a reliance on a user knowledge of the centre of mass of the trailer and correct loading. The accidents affect surrounding road users and are exacerbated by wind, vehicle speed and road surface conditions. When the trailer centre of mass lies behind the wheel centreline, instability may occur with small driver inputs, causing exponential growth of the trailer yaw rate. Current automotive vehicle trends include wider and longer wheelbases, which can require rear-wheel steering to minimise the turning circle. As an adaptive safety feature for towing vehicles, this paper provides simulation results demonstrating that small rear-wheel steering inputs mitigate user loading error, generating a stable towing platform, with modifications only to the tow vehicle. Here, a three degree of freedom, two platform vehicle model is used to demonstrate the instability criteria for both a good and poor user loading case. A simple control gain to rear-wheel steering is used to augment the front wheel steering, causing the instability to become controllable under more extreme conditions than typically investigated. A Simulink model of a vehicle with a single axle trailer is generated with increasing forward speeds between 20 and 60 m/s where steering perturbation is applied with varying trailer centre of mass position. Critical stability is shown and the rear-wheel steering extends the stability criteria measured with both damping ratio and overall amplitude of hitch angle. A trailer centre of mass divided by the trailer length of −0.1 is unstable but is corrected with proportional rear-wheel steering. Even with a value of −0.14, the rate of growth of the instability is so reduced that a driver can take corrective action safely.</p>