Within line of sight pointing and stabilisation of EO (Electro-optic) systems operating under motion disturbances it is desirable to measure the inertial orientation of different parts of the system, not just the line of sight - this would allow additional information to be added to the control loop. To implement this a framework to fuse the multiple inertial sensors of the EO system is considered, with an example implemented. The fusion of higher performance sensors located at the line of sight is implemented within the proposed framework, to improve the performance of the estimate at the location of the lower performance sensor. The fusion framework makes use of cascaded Multiplicative Extended Kalman Filter that estimate the multiplicative error of the quaternion orientation estimate.
Precision tracking applications using two-axis gimbal or antenna actuation systems suffer from a singularity when the
inner axis reaches +-90 degrees. This is known by various terms - the keyhole singularity, gimbal lock or the nadir
problem. Practically, sightline control is degraded and often lost in a neighborhood of this singularity. In this paper, two
nonlinear control algorithms are applied to sightline pointing and stabilization control in the neighborhood of the nadir;
the traditional cosecant correction and the nonlinear generalized minimum variance technique. Both controllers were
tested against a validated model of an Aeromech TigerEye turret.
For long-range imaging or low signal-to-noise ratio environments sightline jitter is a primary source of image
degradation. The conventional pointing & stabilization figure of merit is therefore the jitter RMS, with bearing friction
often the largest contributor overall. Recent work has shown that pixel smear during camera integration can be reduced if
adaptive friction compensation 'shapes' the jitter frequency content in addition to reducing the RMS value. This paper
extends this work by automating the tuning process for the sightline control parameters by using a genetic algorithm. The
GA fitness metric is the integral of the modulation transfer function due to any residual sightline jitter. It is shown that
this fitness function is significantly better than the current root-mean-square figure of merit typically employed in
stabilization loop design.
The survivability of helicopters under attack by ground troops using rocket propelled grenades has been amply illustrated
over the past decade. Given that an RPG is unguided and it is infeasible to cover helicopters in thick armour, existing
optical countermeasures are ineffective - the solution is to compute an evasive manoeuvre. In this paper, an
RPG/helicopter engagement model is presented. Manoeuvre profiles are defined in the missile approach warning sensor
camera image plane using a local maximum acceleration vector. Required control inputs are then computed using inverse
simulation techniques. Assessments of platform survivability to several engagement scenarios are presented.
KEYWORDS: Electro optical modeling, Systems modeling, Sensors, Computer simulations, RGB color model, Radar, Data modeling, Control systems, Databases, Remote sensing
Modeling and simulation fidelity varies considerably throughout the design process, from simple performance models
used for requirements capture through to radiometrically correct synthetic environments for hardware-in-the-loop final
acceptance testing. As complex systems engineering design is intrinsically iterative, having a framework to integrate
models of different fidelity is extremely useful. In this paper, a new hierarchical, agent-based simulation engine is
presented and then applied to the design of two airborne remote-sensing systems, forward mounted multi-mode radar and
an electro-optic countermeasures system.
This paper presents the results of a preliminary investigation of optimal threat evasion strategies for improving the
survivability of rotorcraft under attack by rocket propelled grenades (RPGs). The basis of this approach is the application
of inverse simulation techniques pioneered for simulation of aggressive helicopter manoeuvres to the RPG engagement
problem. In this research, improvements in survivability are achieved by computing effective evasive manoeuvres. The
first step in this process uses the missile approach warning system camera (MAWS) on the aircraft to provide angular
information of the threat. Estimates of the RPG trajectory and impact point are then estimated. For the current flight
state an appropriate evasion response is selected then realised via inverse simulation of the platform dynamics. Results
are presented for several representative engagements showing the efficacy of the approach.
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