1. EHPV Technology
Auto-Calibration and Control Applied to Electro-Hydraulic Valves
by Patrick Opdenbosch
GOALS
Development of a general formulation for control of nonlinear systems with parametric uncertainty, time-varying characteristics, and input saturation
Improve the performance of electro-hydraulic valves via online auto-calibration and feedback control
Study of online learning dynamics along with fault diagnostics
PUMP PRESSURE CONTROL
Single EHPV
Feedback compensation via discrete PI controller with anti-windup
Feedforward compensation via inverse experimental steady state response
LEARNING CONTROL
The control input is composed of:
Feedback compensation via online identification of trajectory error parameters
Feedforward compensation via nominal inverse mapping
Feedforward correction via learned adjustment to inverse nominal mapping
Closed-loop Step Response
LEARNING INCOVA CONTROL
Learning on single EHPV on pressure control mode
Learning on 2 EHPV for piston motion control
Learning on 4 EHPV for piston motion control
ABSTRACT
Motion control of hydraulic pistons can be accomplished with independent metering using Electro-Hydraulic Poppet Valves. Currently, the valve opening is achieved by changing the valve’s conductance coefficient Kv (output) in an open loop manner via PWM current (input), computed from an inverse input-output map obtained through offline calibration. Without any online correction, the map cannot be adjusted to accurately reflect the behavior of the valve as it undergoes continuous operation. The intention is to develop a control methodology to have the valve learn its own inverse mapping at the same time that it’s performance is improved.
Controller Implementation (SIMULINK/XPC-Target)
Closed-loop Tracking Response
Steady State Data used for Feedforward Compensation
FIXED INCOVA CONTROL
Single EHPV for pump control + 4 EHPV for piston motion control
Pressure Feedback to INCOVA logic
Open loop valve opening control
No adaptation (fixed lookup tables) of inverse I/O valve mapping
Same inverse I/O mapping for all 4 EHPV in Wheatstone Bridge Arrangement
Single EHPV Flow Conductance Closed Loop Response
Single EHPV Trajectory Error Parameter Estimation
Piston’s Position Closed Loop Response
Piston’s Velocity Closed Loop Response
System Pressures
Input Currents to EHPV Solenoids
PUMP PRESSURE
MARGIN CONTROL
PROJECT TASKS
Development of hydraulic testbed employing the EHPV Wheatstone bridge arrangement
Design and test EHPV Pump pressure control scheme
Design and test INCOVA control scheme without online learning of the valves’ input/output (I/O) mapping
Design and test INCOVA control scheme with online learning of the valves’ input/output mapping
Design and test flow conductance observer
Conduct performance evaluation
Piston Speed Response
System Pressures Response
Input Solenoid Currents to EHPV’s
EHPV Wheatstone Bridge Arrangement for Motion Control
Piston’s Position Closed Loop Response
Piston’s Velocity Closed Loop Response
FLOW CONDUCTANCE OBSERVER
HYDRAULIC TESTBED
Workport Pressure Dynamics
Electronics
Wheatstone Bridge Assembly (EHPV)
Wheatstone Bridge Arrangement
Return
Supply
Piston Dynamics
Resulting System
OBSERVER:
FUTURE WORK
Experimental merging of flow conductance estimator and learning control
Incorporate fault diagnostics capabilities along with online I/O mapping learning
Valves for Pump Control
Needle Valve
HYDRAULIC CIRCUIT
Speed Command Knob
Hydraulic Piston
Bypass Hose
Position/Velocity Sensor
Simulation Results: Estimated KA vs Actual KA
HYDRAULIC COMPONENTS
Experimental Piston’s Friction Force
Friction Force Model Error Df
Collaborators:
James D. Huggins
Sponsors: HUSCO International and FPMC Center
Advisors:
Dr. Nader Sadegh, Dr. Wayne Book
website:
Spring 2006