1. Advanced Control Techniques for Electro-Hydraulic Flow Control Valve EHPV ® Technology by Patrick Opdenbosch Abstract This project at the early stage explores the dynamic modeling of an Electro-Hydraulic Poppet valve (EHPV®) and a control scheme for its input-output calibration. The dynamic nonlinear mathematical model of the EHPV is based on the interaction among its mechanical, hydraulic, and electromagnetic subsystems. The mechanical subsystem is modeled as a combination of mass-spring-damper systems with the capability of model switch depending on the mode of the valve. This subsystem is coupled to the electromagnetic subsystem by means of magnetic forces acting on the valve’s pilot pin. In addition, the hydraulic subsystem, represented by orifice type models with internal pressurization chambers, is also coupled to the mechanical subsystem via pressures acting on the faces of the mechanical components. Two of the most important features of the valve include a bi-directional flow capability and a pressure compensation mechanism for consistent input at flow initiation. In regards to the valve input- output map calibration, an on-line control scheme for the valve to learn how much current it needs to meet a required flow under a given pressure differential (self-calibration) is explored. The self-calibration of the valve is started by obtaining a nominal current-flow map from a given EHPV. This nominal map is obtained experimentally with the aid of least square approximation and piecewise functions, and it is implemented in a look-up table. A controller adapts this look-up table on-line via the minimization of the error between the desired flow and the actual flow through the valve by means of the gradient descent method using the model estimation of the valve restriction coefficient. Consequently, the parameters of the look-up table are adjusted and the valve learns to self-calibrate. Sponsors: HUSCO International and FPMC Center Email: gte608g@prism.gatech.edugte608g@prism.gatech.edu website: http://www.imdl.gatech.edu/opdenboschhttp://www.imdl.gatech.edu/opdenboschSpring 2004 Advisors: Dr. Nader Sadegh, Dr. Wayne Book Nonlinear Model Model Principle Valve Cross-sectional View ElectromagneticMechanicalHydraulic EHPV Subsystems Model Validation Testbed Employed for Model Validation and Hydraulic Circuit Schematic Time and Frequency Response Hardware-In-The-Loop Feedback Tracking Control Scheme Anti-Windup PI Controller Open-loop SIMULINK Model Closed-loop Response Duty Cycle Hydraulic Circuit Implementation and Hardware-In-The-Loop Simulator Actuator Displacement Control Using EHPV ® Wheatstone Bridge Configuration 4 EHPV‘s can be used to control the displacement of a passive actuator. The controller receives a desire performance criterion (not shown) along with pressure data from the upstream and downstream portions of each valve and in turn sends PWM signals to the EHPV’s. A hierarchical controller for this task is under development. Collaborators J.D. Huggins, Amir Shenouda, and Scott Driscoll On-Line Auto-Calibration The auto-calibration of the valve has the objective of having a robust input-output map which is used to control flow through the valve. Schematic for EHPV Auto-Calibration The input-output map can initially be approximated by: Let the cost function be The input-output map is corrected in the adaptive look-up table by the minimization of the cost function