A new variable-structure (VS) Augmented Interacting Multiple Model (AIMM) technique is developed in the paper. Fixed-structure (FS) and VS AIMM algorithms using augmented constant velocity and augmented coordinated turn (ACT) models, are proposed. The ACT model includes the difference between the unknown current turn rate and its value assumed in the IMM models. Due to the estimated turn rate, significant self-adjusting abilities are provided to the designed AIMM algorithms, which give very good overall accuracy and consistency. Both AIMM algorithms are compared to a particular VS adaptive grid IMM algorithm. It is shown that the VS IMM algorithms possess better mobility, while the FS AIMM algorithm possesses better consistency. The VS AIMM algorithm provides the best estimation of the turn rate.