On-line estimation of local road gradient for improved steady state suspension deflection control

The paper outlines a systematic method for controlling suspension deflectio n offset and drift, that can arise when an actively sprung vehicle encounte rs a constant gradient or a long wavelength road surface undulation. A brie f review of the problem is given and it is shown that the inherent filterin g effects of a standard Kalman observer does not sufficiently address the i ssue. An expanded Kalman filter is introduced to estimate the underlying ve rtical road velocity, and this is applied within a linear state feedback co ntroller. Its effect on suspension performance is shown to be advantageous when compared with simpler state feedback and integral control techniques.