(19) United States
(12) Patent Application Publication (io) Pub. No.: US 2004/0015933 Al
Campos et al. (43) Pub. Date: Jan. 22,2004
(54) BACKLASH COMPENSATION WITH
FILTERED PREDICTION IN DISCRETE
TIME NONLINEAR SYSTEMS BY DYNAMIC
INVERSION USING NEURAL NETWORKS
(75) Inventors: Javier Campos, Arlington, TX (US);
Frank L. Lewis, Arlington, TX (US)
FULBRIGHT & JAWORSKI L.L.P.
A REGISTERED LIMITED LIABILITY
600 CONGRESS AVENUE, SUITE 2400
AUSTIN, TX 78701 (US)
(73) Assignee: Board of Regents, The University of Texas System
(21) Appl. No.: 09/969,549
(22) Filed: Oct. 2, 2001
Related U.S. Application Data
(60) Provisional application No. 60/237,580, filed on Oct. 3, 2000.
(51) Int. CI.7 G06F 9/45
(52) U.S. CI 717/160; 714/25
Methods and apparatuses for backlash compensation. A dynamics inversion compensation scheme is designed for control of nonlinear discrete-time systems with input backlash. The techniques of this disclosure extend the dynamic inversion technique to discrete-time systems by using a filtered prediction, and shows how to use a neural network (NN) for inverting the backlash nonlinearity in the feedforward path. The techniques provide a general procedure for using NN to determine the dynamics preinverse of an invertible discrete time dynamical system. A discrete-time tuning algorithm is given for the NN weights so that the backlash compensation scheme guarantees bounded tracking and backlash errors, and also bounded parameter estimates. A rigorous proof of stability and performance is given and a simulation example verifies performance. Unlike standard discrete-time adaptive control techniques, no certainty equivalence (CE) or linear-in-the-parameters (LIP) assumptions are needed.