Patent ID: 6757601
Filing Date: 2004-06-29
Classification: B62D

Abstract:
A method of controlling a vehicle steer-by-wire system having a road wheel reference angle generator, the method comprising:providing a steering wheel control sub-system to generate road wheel reference angles and to produce steering feel for a vehicle driver; providing a road wheel control sub-system including a multivariable road wheel controlled plant and a multivariable road wheel controller for controlling actual road wheel angles to track to road wheel reference angles; modeling the nominal multivariable road wheel controlled plant as [Î¸r&it;â€ƒ&it;lÎ¸rr]=[Gll&af;(s)Glr&af;(s)&it;â€ƒ&it;Grl&af;(s)Grr&af;(s)]&it;â€ƒ[ulur].wherein &thgr;rl 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 torque control variable, ur is indicative of the right road wheel torque control variable, Glr(s) is indicative of a first plant transfer function between &thgr;rl and ul, Glr(s) is indicative of a second plant transfer function between &thgr;rr and ul, Grl(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;implementing the multivariable road wheel controller 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 torque control variable, ur is indicative of the right road wheel torque control variable, el is indicative of the left road wheel angle error, er is indicative of the right road wheel angle error, Crr(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;applying road wheel angles and angular rates as feedback signals to construct a servo control system including the multivariable controlled plant and the multivariable road wheel controller to implement the left and right road wheel angles tracking for left and right road wheel reference angles; generating left and right road wheel reference angles from the steering wheel angle with a road wheel reference angle generator using variable left and right steering ratios and calibration processes for the steering wheel angle, wherein the road wheel reference angle generator has one steering wheel angle input and left and right road wheel reference angle outputs, the generator having first and second stages to produce left and right road wheel reference angle outputs; receiving left and right road wheel reference angles from the road wheel reference angle generator being based on the steering wheel angle command from the steering wheel control sub-system; receiving the left and right road wheel angles from the multivariable road wheel controlled plant; calculating 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; generating the left and right road wheel torque control variables from the multivariable road wheel controller with servo control performances based on the left and right road wheel angle errors; and applying torque control variables of the multivariable road wheel controller to the multivariable controlled plant to control tracking of the actual left and right wheel angles with the left and right road wheel reference angles, respectively.