Steering Control of the Off-Highway Vehicles

Steering is integral system of any vehicle to achieve direction control. With driver’s inputs, as steering wheel is turned, the steering mechanism is operated to turn the road wheels to route the vehicle on desired path. This Paper studies the different steering architectures and the learning is applied to improve the off-highway vehicles’ steering control. Off-Highway vehicles have traditionally been using Hydrostatic Power Steering (HPS) mechanism with no feedback controls. This mechanism consists of inherent limitations to vehicle efficiency, reliability and control preciseness. In this paper, HPS is modeled using 1D simulation tools from the system parameters and derived equations. The results are plotted and discussed to acknowledge the merits and demerits of existing system which helped in proposing the alternate steering solution. Different steering architectures are evaluated and trade-off study performed to choose the Electro-Hydraulic Power Steering (EHPS) architecture. The mathematical equations behind the Electro-Hydraulic steering system are derived and couple of control strategies (like PID controller and state-feedback controller) are applied to minimize the error between commanded and actual road wheel angle. Non-linear system is simulated using different software and PID controller gains are tuned to achieve desired response. Linearized state space system is modeled to obtain the state-feedback control to operate electro-hydraulic steering valve. In the end, event triggered control is discussed to operate the steering system at desired threshold for potential energy saving.