Controller design for string stable heterogeneous vehicle strings

The spacing errors of a string stable, homogeneous vehicle string attenuate uniformly down the vehicle chain. This result is useful for implementing vehicle formation control because it provides a guideline for the proper intervehicle spacing. In the heterogeneous case, the differing dynamics of the vehicles means the spacing errors do not attenuate or amplify uniformly down the vehicle chain, regardless of whether the formation is string stable or not. Results from heterogeneous string stability analysis are presented and used to construct a controller design procedure that gives string stability and robustness to external disturbances for heterogeneous vehicle strings. The proper intervehicle spacing needed for nominal safety is determined. The resulting controller is simulated to demonstrate its effectiveness. It is shown that string stability can be achieved for heterogeneous vehicle strings of arbitrary length and arbitrary vehicle type ordering.