Control Allocation Scheme for Aircraft with Redundant Control Effectors

Abstract

Modern aircrafts may exploit more complex control effectors (surfaces), some of which are designed as redundant effectors. Redundant control effectors can give alternatives to provide required control moment in different situation/condition. This redundancy means that different combination of control effectors action can be generated for resulting a particular maneuvers or corrections. Hence, the redundancy may provide some degree of flexibility in controlling the attitude and maneuver of the aircraft.

In this paper a control allocation scheme using weighting matrix is explored and evaluated. The weighting matrix can be viewed as a control signal distributor which may assign the responsibility of generating particular control moment to different control effectors, hence some preferred effectors can be assigned. Further, the weighting matrix implemented here can be computed and adapted to condition of the effectors, in terms of their current ability to track the control signal. In case of one of the control effectors is degrading, then the control task for that particular effector will be assigned to other effectors, within their performance limits, to push the system in producing the required actions (maneuvers). Using this scheme, a way of anticipating effectors faults, by redistributing the control signals to different effectors, can be achieved.

The scheme is developed and simulated on an aircraft model with canard configuration which may provide redundant effectors in longitudinal channel. The developed scheme is simulated for providing particulars attitude control actions in longitudinal channel under different conditions. In this case, the scheme shows its ability to generate the required moment to track the control command using different combination of control effectors. Further some effectors faults are also simulated to evaluate the
redistributing behavior of the scheme. It can be seen that when one of the effectors is degraded/faulted, the weighting matrix is adapting and automatically redistributing the control command to other effectors, hence the desired response can still be maintained. The scheme is also improved so that it can handle actuator lag by introducing an augmented matrix and linear transformation from control input into virtual control input.