To neutralize the incoming ballistic missile targets, its information should be accurately known in the interceptor missile body frame. Under the perfect scenario of seeker and navigation sensor mounting on the missile airframe, the estimates of the target states are accurate in the missile body frame. But in reality there exists a misalignment between missile body frame and seeker mechanical axis, this leads to biased gimbal angle measurements from the seeker. Even though the bias in the gimbal angles are small, it causes a biased estimate of relative position and relative velocities. Using these biased state estimates erroneous guidance commands are generated which in turn deteriorates the mission performance. Present paper addresses this issue and proposes a methodology to estimate the bias in the gimbal angles by mounting two accelerometers on back plate of seeker antenna, which makes target state estimator insensitive to axis misalignment errors. Simulation on the Six-DOF platform with a realistic seeker model under extreme bias scenarios shows a tremendous improvement and makes the target state estimates unbiased leading to acceptable mission performance.
['Prem Kumar', 'P. G. Bhale', 'Abhijit Bhattacharyya', 'Radhakant Padhi']
Gimbal angle bias free state estimator for anti-ballistic missile using additional accelerometers