Electro-Hydraulically controlled Steerable Rear axle for commercial vehicles

This paper presents the hydraulically actuated and electronically controlled rear axle steering system developed indigenously for defence vehicle. Some defence applications required vehicles with long wheel base and deck length for the system to assemble on the chassis. For these vehicles, the steering system requirement mainly the turning circle diameter requirements are very stringent. To meet these requirement, vehicle steering system is divided in two parts- front steering (Traditional) and rear steering. This rear steering is controlled by electronic controller based on the inputs from front wheel angles from front angle transducers and vehicle speed from vehicle CAN system. With these inputs the electronic controller regulates the flow in hydraulic valve block received from primary tandem pump to steering cylinders for required stroke length to turn the rear wheels. Further, there are angle transducers on the rear axles which sends feedback signal to electronic controller, that the required wheel angle position has been achieved. This rear steerable axles also helps to improve manoeuvrability of this 6 axle vehicle (2 Front axle & 4 Rear axle) of all wheel drive 12X12 configuration. This paper will discuss in detail about the electronic and hydraulic circuit schematic, mathematical model for required force calculations, component designing, it's packaging and it's digital and physical validation.