We consider the problem of tracking mu ltiple maneuvering targets in the presence of clutter u sing switch ing multiple target motion mo d els. A n ovel sub optimal fixed-lag

smo othing algorithm is develop ed by applying the b asic interacting multiple mo d el (IMM) approach and joint probabilistic d ata asso ciation (JPDA) technique to a state augmented system. But unlike the standard single scan JPDA

approach, we exploit a multiscan JPDA (Mscan-JPDA) approach to solve the d ata asso ciation problem. The algorithm is illustrated via a simulation example.