Patent ID: 6799104
Filing Date: 2004-09-28
Classification: B62D

Abstract:
A system for controlling a vehicle steer-by-wire system applying a robust control for independent tracking of road wheel angles, the system comprising:a steering wheel control sub-system to apply a steering wheel angle command for generating road wheel reference angles and for producing steering feel for a vehicle driver; a road wheel control subsystem including a multivariable road wheel controlled plant under effects of uncertainties and disturbances and a multivariable road wheel controller for controlling actual road wheel angles to track robustly to road wheel reference angles within a servo control system structure having road wheel angular position feedback and road wheel angular rate feedback loops, the nominal multivariable road wheel controlled plant being modeled as [Î¸rlÎ¸rr]=[Gll&af;(s)Glr&af;(s)&it;â€ƒ&it;Grl&af;(s)Grr&af;(s)]&it;â€ƒ[ulur],wherein &thgr;rf is indicative of the left road wheel angle, &thgr;rr is indicative of the right road wheel angle, ul is indicative of the left road wheel control variable, ur is indicative of the right road wheel control variable, Glf(s) is indicative of a first plant transfer function between &thgr;rf and ul. Glf(s) is indicative of a second plant transfer function between &thgr;rr and ul, Grf(s) is indicative of a third plant transfer function between &thgr;rf and ur, and Grr(s) is indicative of a fourth plant transfer function between &thgr;rr and ur; wherein the uncertainty of the road wheel controlled plant is given as G(s)=G0(s)(I+&Dgr;G(s)) where G0(s) is a nominal multivariable controlled plant model, &Dgr;G(s) represents a bound function of the uncertainty, and l is an identity matrix, and wherein the disturbance is represented as external disturbance torque to the left and right road wheels; the multivariable road wheel controller being implemented as [ulur]=[Cll&af;(s)Clr&af;(s)&it;â€ƒ&it;Crl&af;(s)Crr&af;(s)]&it;â€ƒ[eler],wherein ul is indicative of the left road wheel control variable, ur is indicative of the right road wheel control variable, &thgr;l is indicative of the left road wheel angle error, &thgr;r is indicative of the right road wheel angle error, Clf(s) is indicative of a first controller transfer function between ul and el, Clr(s) is indicative of a second controller transfer function between ur and el, Crf(s) is indicative of a third controller transfer function between ul and err, and Crr(s) is indicative of a fourth controller transfer function between ur and er, a robust control implemented within the multivariable road wheel controller to overcome affects of uncertainties and disturbances from the steer-by-wire system, vehicle, and external environment, wherein the robust multivariable road wheel controller receives left and right road wheel reference angles being based on the steering wheel angle command from the steering wheel control sub-system and left and right road wheel angles from the multivariable road wheel controlled plant and calculates the left and right road wheel angle errors based on the left and right road wheel angles and left and right road wheel reference angles, wherein the robust multivariable road wheel controller generates the left and right road wheel torque control variables from the multivariable road wheel controller with robust servo control performances based on the left and right road wheel angle errors, and wherein the road wheel servo control system applies road wheel angles and angular rates as feedback signals for implementing tracking of left and right road wheel angles with left and right road wheel reference angles and applies torque control variables of the robust multivariable road wheel controller to the multivariable controlled plant to control tracking robustly of the actual left and right wheel angles with the left and right road wheel reference angles, respectively.