The purpose of the designed H ∞ controller is to drive effectively the hydraulic system and to make it follow the desired trajectory, which is commanded by a joystick, steering wheel or geographic based data. To design the controller we used the experimentally identified SIMO linear mathematical model. The identification procedure is based on random excitation signals and prediction error methods for regressive discrete-time equations. The input of the mathematical model is the voltage applied to the spool driver EH module (PVE) and the outputs of the model are the spool position of the proportional valve in the steering unit, flow rate and the cylinder piston position. These output variables carry important information about the state of the system and can be used to increase performance in respect to the case, when using only the cylinder piston position or pressure signals. We have already experimented with various control strategies for the identified mathematical model. Experimental studies are performed on a laboratory test rig for electrohydraulic steering systems based on the 32-bit microcontroller and taking into account the technical specifications of mobile machine manufacturers and standards. In addition to the requirements of the safety standards, new advantages are achieved in terms of precise tracking control and providing a variable steering ratio between the steering wheel and the steering cylinder supported by the designed H ∞ controller.

No abstract

No abstract

AbstractThe article presents a developed embedded system for control of electrohydraulic power steering based on multivariable uncertain plant model and advanced control techniques. The plant model is obtained by identification procedure via “black box” system identification and takes into account the deviations of the parameters that characterize the way that the control signal acts on the state of the model. Three types of controller are designed: Linear-Quadratic Gaussian (LQG) controller, H∞ controller and μ-controller. The main result is a performed comparative analysis of time and frequency domain properties of control systems. The results show the better performance of systems based on µ-controllers. Also the robust stability and robust performance are investigated. All three systems achieved robust stability which guarantees their workability, but only the system with µ-controller has robust performance against prescribed uncertainties. The control algorithms are implemented in specialized 32-bit microcontroller. A number of real world experiments have been executed, which confirm the quality of the electrohydraulic power steering control system.

No abstract