Feedforward model-inverse position control of three-stage servo-valve using zero magnitude error tracking control

Abstract

Three-stage servo-valves are popularly used in hydraulic systems that require large flow rate and high pressure. For a proper control of flow direction and flow rate fed into a hydraulic actuator, securing a proper position control bandwidth is a critical task for the servo-valve. In this paper, a set of popular control methods are systematically studied and a control method is selected. It is proven that the feedforward model-inverse control is the most effective method in terms of the control bandwidth. In the present work, the feedforward closed-loop architecture is adopted and the closed-loop system is estimated in a linear discrete-time transfer function by recursive least squares method. On recognizing a nonminimum phase zero problem, this work implements the zero magnitude error tracking control, an approximate model-inverse technique, in order to overcome the problem. As a result, the effectiveness of the proposed feedforward model-inverse position control strategy is verified.

Comparative Study of Performance-Oriented Feedforward Compensation Strategies for Precision Mechatronic Motion Systems

“…Traditional model-based feedforward controllers are generally in the form of polynomial functions [18] or rational functions [19], which can be utilized to approximate plant inversions. To deal with nonminimum phase zeros caused by time delay and zero-order hold sampling in real-time control systems, several famous model-based feedforward controller structures have also been proposed, such as zero-phase-error tracking control (ZPETC) [20], [21], zero-magnitude-error tracking control (ZMETC) [22], [23], and nonminimumphase-zero-ignore tracking control (NMPZITC) [24], [25]. However, all these model-based feedforward controllers are impossible to be the perfect plant inversion due to the existence of modeling error and parameter uncertainty.…”