Identification and Control of Nonlinear Hydraulic System

Nonlinearities in a hydraulic system, such as deadband, saturation, friction, hysteresis etc., are usually not known exactly. If they are not properly compensated for, the performance of the system will suffer. This paper discusses the identification and control of this type of nonlinear hydraulic systems. The emphasis is on the deadband. A method is proposed in this paper to estimate its characteristics, and a piecewise-linear preload element can be used to compensate for the deadband in the design of the controller. This combination results in the closed-loop behaviour of a system with a deadband being the same as that of its linear portion.