Model recognition and validation for an off-road vehicle electrohydraulic steering controller

Automated steering control is essential for an autonomous off-road vehicle. Many off-road vehicles use an electrohydraulic (E/H) actuator to implement the steering control. This paper reports the design and validation of an electrohydraulic steering controller through a combination of system identification, model simulation, and field tests. A kinematic model of the steering linkage geometry provided the gain between the hydraulic actuator and the front wheels. The system model was used to close the steering control loop based on the feedback signal from the hydraulic steering actuator rather than from the front wheels. Test results were used to identify the non-linear and dynamic characteristics of the original electrohydraulic steering system. The system identification model was used to develop a preliminary controller, which was simulated under Matlab before beginning full-scale vehicle testing. The simulation and vehicle test results indicated that the steering controller developed was capable of efficiently handling the non-linearity and dynamic asymmetry of the electrohydraulic steering system.