|M.Sc Student||Zhurbal Alexander|
|Subject||Effect of Estimation on the Performance of an Integrated|
Missile Guidance and Control System
|Department||Department of Aerospace Engineering||Supervisors||Professor Yoseph Ben-Asher|
|Professor Moshe Idan|
|Full Thesis text|
Until recently, the traditional approach in air-to-air missile design was to design the guidance loop and control loop (autopilots) separately. This is considered to be correct, since the guidance loop variables are changing much slower than those of the control loop during the most of the scenario, i.e. the kinematics of the interception itself is much slower than the dynamics of the missile. In other words, the time constants of the guidance loop are much bigger than those of the control loop. This leads to spectral separation of the frequencies, which enables to design both loops independently.
The accuracy demands are requesting the intense maneuvering during the last phase of the intercept (end - game), causing rapid changes in its geometry, especially when the scenario is against highly maneuverable target. Thus the assumption of the spectral separation mentioned above is no longer correct, due to shortening time constants of the interception geometry. Therefore the examination, whether the integrated guidance - control design approach will help us to achieve better accuracy of the intercept, is justified.
Recently a number of papers appeared, discussing the integrated guidance - control approach. All of them show, that by implementing the integrated design much better interception performance, i.e. smaller miss distances, can be achieved. In some of these works the research was conducted with new control method - Sliding Mode Control (SMC), which distinct in its robustness, making it very useful in non - linear systems with modeling errors. However, in those research works one of the crucial parameters of the integrated guidance - control law - the target maneuver - was assumed to be known. In reality, this is not a situation - the target acceleration amplitude and period time are usually unknown to the interceptor and must be estimated.
In our work we combined the target maneuver estimator in the integrated guidance - control system. The chosen estimator is of the Sliding Mode Observer / Differentiator (SMOD) type.
The intercept performance and overall system efficiency was examined by several batches of Monte - Carlo runs, which included the scenarios with guidance data corrupted by radar measurements noises. The results show that the integrated guidance - control approach has a clear advantage over the separated one, in addition to the results of the previous works. The robustness of the integrated approach to the estimation errors and measurements noises is much stronger than that of the separate guidance loop and control loop design.