With the improvement of sensor resolution, extended targets (ETs), characterised by multiple measurements, have become a hotspot in the field of target tracking. The trajectory probability hypothesis density (TPHD) filter, which inherently provides trajectory estimates, stands out as an effective tracking filter. By integrating the interacting multiple model (IMM) approach, we introduce an IMM-ET-TPHD filter for tracking maneuvering ETs in this paper. Firstly, we extend the concept of the IMM to trajectory sets and derive the IMM-ETTPHD recursion. Then, we develop a Gaussian mixture (GM) implementation of the IMM-ET-TPHD recursion. Finally, the proposed IMM-ET-TPHD algorithm is validated in a challenging maneuvering ET tracking scenario, demonstrating its superior performance.

The Bayesian inference has a two-step recursion structure, i.e., prediction and updating, which can be viewed as a dynamic reasoning process. Based on this elegant structure, various multi-target tracking (MTT) algorithms have been invented and successfully applied in many areas. On the other hand, Bayesian inference MTT algorithms are model-based methods that rely on models’ accuracy and first-order Markov assumption. In recent years, the MTT algorithms based on deep learning have received much attention due to their model-free property and the ability to learn from data, although they have issues such as over-fitting, generalization, etc. In this work, we propose a Transformer-based multi-target tracker whose architecture mimics the Bayesian inference, referred to as the Bayesian inference-based Transformer (BAIT) for MTT. To deal with the model mismatch issues, BAIT uses neural networks instead of the pre-assumed motion and observation models while retaining the excellent architecture of Bayesian inference. BAIT can recursively complete accurate predictions and updates via Transformer by refining the estimation of target states in a Bayesian inference-like manner. Thus, BAIT can be viewed as a combination of model-based and data-based methods. The simulation results show that, because of combining the advantages of Bayesian architecture with intelligent data association structure, BAIT is competitive in simple scenarios and achieves superior performance when the data association task becomes complicated.

Deep learning (DL) approaches, which do not rely on models and can learn complex relationships within data, garner increasing attention in the model-free multi-target tracking (MTT) domain. However, the study of applying the DL method to multi-sensor fusion-based MTT is relatively less. In this paper, we propose a Transformer-based distributed multi-sensor MTT approach, which adopts a hybrid fusion structure with both feature-level and decision-level fusion. First, for each local sensor, the high-dimensional feature information is extracted from the measurements based on a Transformer-based tracking module, which enables continuous tracking of multiple targets and provides the predicted target states and corresponding uncertainties. Then, the outputs of local sensors are fused using the covariance interception (CI) fusion rule. Finally, to further improve the fusion performance, the decision-level information is fed into a fusion decoder with the feature-level information to obtain the predicted target state and uncertainties after deep fusion. In this way, we realize a deep utilization of different sensors’ information and achieve a feature-level decision-level hybrid multi-sensor fusion, namely, Transformer-based multi-sensor hybrid fusion (TMSHF). Simulation results show that the proposed fusion method outperforms the CI algorithm in various tracking scenarios.