158 research outputs found
Transfer Alignment Technique for Shipboard Missile Strapdown Inertial Navigation System using an Adaptive Kalman Filter
Missile Guidance system needs accurate estimates from Inertial Navigation System (INS) for guiding
the vehicle towards the target. In this paper a target point, specified before launch, in a battlefield scenario
is considered for a landmark using missile Strap Down Inertial Navigation System (SDINS) aided by Master
INS (MINS) placed on a moving platform. Azimuth information of the missile is one of the most critical
navigation states for estimation on the moving platform before launching the missile for precise impact.
An Adaptive Kalman Filter (AKF) based on the error state model is formulated. The 7-state AKF with 4-measurement forms the core, where the filter gain of the innovation sequence (measurements) is
evaluated. This approach of adaptively computing the gain is tested in a laboratory, on a van and in a ship
trial, culminating in a successful guided missile launch. Mean and the covariance of the measurement
residuals were used in a unique way to compute adaptive gain after the accumulation of initial samples.
A Master INS (with advanced Gyros) whose accuracy is much higher than the accuracy of the missile’s
SDINS is used for velocity matching algorithm before the launch with execution of an S-maneuver for generation
of accelerations towards observing the states more appropriately. Estimated error states were used in a feedback mode to get near the true orientation of the Missile’s slave INS. Error quaternions are used for this purpose in the feedback and the gains were selected using offline matrix Riccati equation solution in a discrete domain as used in the modern control system. The results were very encouraging with less than 5 arc minutes of error in azimuth
Information Aided Navigation: A Review
The performance of inertial navigation systems is largely dependent on the
stable flow of external measurements and information to guarantee continuous
filter updates and bind the inertial solution drift. Platforms in different
operational environments may be prevented at some point from receiving external
measurements, thus exposing their navigation solution to drift. Over the years,
a wide variety of works have been proposed to overcome this shortcoming, by
exploiting knowledge of the system current conditions and turning it into an
applicable source of information to update the navigation filter. This paper
aims to provide an extensive survey of information aided navigation, broadly
classified into direct, indirect, and model aiding. Each approach is described
by the notable works that implemented its concept, use cases, relevant state
updates, and their corresponding measurement models. By matching the
appropriate constraint to a given scenario, one will be able to improve the
navigation solution accuracy, compensate for the lost information, and uncover
certain internal states, that would otherwise remain unobservable.Comment: 8 figures, 3 table
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