Abstract:
A first Kalman filter (52) estimates true measures of yaw rate (ω) and vehicle speed (U) from associated noisy measures thereof generated by respective sensors (16, 18) in a host vehicle (12), and a second Kalman filter (54) estimates therefrom parameters (C 0 , C 1 ) of a clothoid model of road curvature. Measures of range ( r ), range rate (S) and azimuth angle (ŋ) from a target state estimation subsystem (44), e.g. a radar system (14), are processed by an extended Kalman filter (56) to provide an unconstrained estimate of the state of a target vehicle (36). Associated road constrained target state estimates are generated for one or more roadway lanes (38, 40), and are compared- either individually or in combination- with the unconstrained estimate. If a constrained target state estimate corresponds to the unconstrained estimate, then the state of the target vehicle is generated by fusing the unconstrained and constrained estimates; and otherwise is given by the unconstrained estimate alone.
Abstract:
A processor (26) using a first Kalman filter (52, 52.1) estimates a host vehicle state from speed (U) and yaw rate, the latter of which may be from a yaw rate sensor (16) if speed (U) is greater than a threshold, and, if less, from a steer angle sensor and speed (U). Road curvature parameters (C0, C1) are estimated from a curve fit of a host vehicle trajectory or from a second Kalman filter (54, 54.1) for which a state variable may be responsive to a plurality of host state variables (72, 74). Kalman filters (52, 52.1, 54, 54.1) may incorporate adaptive sliding windows. Curvature of a most likely road type is estimated with an interacting multiple model (IMM) algorithm (2400) using models of different road types. A road curvature fusion subsystem (96) provides for fusing road curvature estimates from a plurality of curvature estimators (42.1, 42.2, 42.N) using either host vehicle state, a map database (88) responsive to vehicle location (86), or measurements of a target vehicle (36) with a radar system (14).