Variable wheelbase reference for vehicle with active front and rear-wheel steering

Jonathan Loyola, Donald Margolis

Rear-wheel steering has seen new popularity in recent years. Many explanations of rear-wheel steering systems use the concept of a ‘virtual wheel base’ to explain in-phase or out-of-phase steering. This paper introduces a novel reference model that realises this metaphor. A reference model is created where its wheelbase can be changed arbitrarily, making the resulting system intuitive and simpler to design and tune. This augments the properties of the reference model whose signals are used for a feedback control system. The real vehicle tracks these signals using active front and rear-wheel steering. This system can be implemented in a vehicle using steer-by-wire or an autonomous vehicle for control. A MIMO controller is derived and results show that the system operates as intended. Finally, a control law is proposed to change the virtual wheelbase using the road curvature. It is shown that it has advantages over conventional rear-wheel steering control.

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