Transfer alignment is the process of initializing the navigation sensors of tactical guided munitions launched from a platform. Through this method the misalignment between aligning and aligned body is estimated, which facilitates navigation of aligning system during its post-ejection course of flight. Measurements provided by navigation sensors of aligning system are noisy compared to those of the launch platform. Thus, excitation of the platform in the form of some deliberate manoeuvre is important in order to discriminate the signal from noise in the available measurement so that the misalignment can be effectively estimated. With advancement of technology, the prerequisites of accurate alignment have changed and with it the algorithms have also undergone continuous transformations. Extensive work has been done on this topic over the years. Here a detailed review of the evolution of transfer alignment problem has been presented. Emphasis is on statistical and algorithmic aspects of the problem rather than time line of work already done. This review provides a general guideline for new entrants to this field and should help practitioners with information regarding trends of research on this topic.

Transfer alignment problem: Algorithms and design issues

Rapid transfer alignment in the presence of time correlated measurement and system noise

This paper considers the problem of tracking and intercepting a potentially moving ground-based RF source with an autonomous guided munition that has a passive bearings-only sensor located on its nose. It is assumed that the munition has lost GPS signal lock and that it relies only on its noisy inertial measurement unit (IMU) for guidance and navigation. Bearings-only target motion analysis (TMA) algorithms are used to obtain a position and velocity estimate for the RF source using the position, velocity and attitude estimates of the munition as well as the azimuth and elevation measurements obtained from the bearings-only RF sensor. Six degree-of-freedom (6-DOF) and three degree-of-freedom (3-DOF) munition models are used to evaluate the tracking and intercept/seeker performance of a hybrid coordinate (HC) extended Kalman filter (EKF), a particle filter (PF), a multiple hypothesis (MH) HC-EKF, and a pseudo-linear least squares (PLLS) filter

Tracking and interception of ground-based RF sources using autonomous guided munitions with passive bearings-only sensors and tracking algorithms

The paper describes the analysis and simulation res ults of a new guidance, navigation and control concept for guided bombs. The presented control system is simple and inexpensive. It is based on a set of one time used impulse engines and inertial navigation system which is set up before the drop by GPS. The engines are mounted around the bomb. There are not movable devices on the bomb’s board. The correcting impulses from the rocket engines are perpendicular to main symmetry axis of the bomb and influence directly the centre of gravity of the guided munitions. In t he paper, the whole control system of the bomb is described. Numerical analysis presents a few cases of bombs’ controlled flights.

Gasodynamic Control System for INS Guided Bomb

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Guidance impulse algorithms for air bomb control

The Joint Direct Attack Munition (JDAM) provides a low-cost accuracy enhancement to existing MK-83, MK-84, and BLU-109 weapons. Low-cost has been achieved through the use of commercial standards and high-volume production techniques. Accuracy improvements are achieved with a GPS-aided Inertial Navigation System (INS), an adaptive optimal guidance algorithm, an autopilot featuring a robust servo structure, and a tail actuator subsystem. Flight testing has demonstrated an impact uncertainty considerably less than the 13 meter Circular Error Probable (CEP) requirement in CPS-aided missions. This paper focuses on the JDAM navigator and Kalman filter algorithms that support both GPS-aided and unaided missions. The GPS-aided navigator consists of a tightly-coupled GPS/INS integration that supports both conventional and relative GPS operation. During GPS-aided operation, the JDAM Kalman filter is configured to estimate the basic kinematics states, calibrate critical inertial sensors, estimate GPS receiver clock errors, and estimate line-of-sight biases between the weapon and each NAVSTAR satellite tracked during the mission. JDAM also includes an unaided navigation mode that is used if GPS is denied. Unaided navigation relies on a transfer alignment algorithm to align the weapon's navigator to the carrier aircraft's navigator and to calibrate critical inertial sensors before release. Transfer alignment enhancements include senescence error estimation and an adaptive Kalman filter tuning algorithm that modifies filter process noise based on the weapon's vibration environment.

H.A. Klotz

Papers

GPS-aided navigation and unaided navigation on the joint direct attack munition