A comparison of control allocation methods for the F-15 ACTIVE research aircraft utilizing real-time piloted simulations

Abstract

A comparison of two control allocation methods is performed utilizing the F-15 ACTIVE research vehicle. The control allocator currently implemented on the aircraft is replaced in the simulation with a control allocator that accounts for both control effector positions and rates. Validation of the performance of this Moment Rate Allocation scheme through real-time piloted simulations is desired for an aircraft with a high fidelity control law and a larger control effector suite.A more computationally efficient search algorithm that alleviates the timing concerns associated with the early work in Direct Allocation is presented. This new search algorithm, deemed the Bisecting, Edge-Search Algorithm, utilizes concepts derived from pure geometry to efficiently determine the intersection of a line with a convex faceted surface.Control restoring methods, designed to drive control effectors towards a "desired" configuration with the control power that remains after the satisfaction of the desired moments, are discussed. Minimum-sideforce restoring is presented. In addition, the concept of variable step size restoring algorithms is introduced and shown to yield the best tradeoff between restoring convergence speed and control chatter reduction.Representative maneuvers are flown to evaluate the control allocator's ability to perform during realistic tasks. An investigation is performed into the capability of the control allocators to reconfigure the control effectors in the event of an identified control failure. More specifically, once the control allocator has been forced to reconfigure the controls, an investigation is undertaken into possible performance degradation to determine whether or not the aircraft will still demonstrate acceptable flying qualities.A direct comparison of the performance of each of the two control allocators in a reduced global position limits configuration is investigated. Due to the highly redundant control effector suite of the F-15 ACTIVE, the aircraft, utilizing Moment Rate Allocation, still exhibits satisfactory performance in this configuration. The ability of Moment Rate Allocation to utilize the full moment generating capabilities of a suite of controls is demonstrated. AcknowledgmentsI would like to extend my most sincere gratitude to my parents for their support and encouragement over the years. They have inspired me to make the most of myself and to live each day to the fullest. It is because of their guidance and direction that I find myself continously striving towards the top with aspirations of overcoming any obstacle along the way. To my brothers Steve and Jon between whom I have been fortunate enough to have grown up. With Steve's endless effort to lead the way, blazing new trails and setting benchmarks at each step, and with Jon's relentless desire to never stay in the shadow of Steve and I, it has thus far been an exhausting yet rewarding quest through academia and life.I must thank my advisor Dr. Wayne Durham for his persistence and patience with me.He took me under his win...

Comparison of Two Methods Used to Deal with Saturation of Multiple, Redundant Aircraft Control Effectors

“…This method is a computationally efficient method that produces nearoptimal solutions to the linear three-objective control problem. Further work by Durham and Scalera [7] explores this algorithm and compares the performance to an existing F-15 ACTIVE (Advanced Control Technology for Integrated VEhicles) allocator using real-time pilot-in-the-loop simulations. The research done by Durham and Scalera focused on the restoring aspects of allocation as well as control reconfiguration in the event of a surface failure.…”

“…Work by Durham [6] introduces this computationally efficient control allocation method called Bisecting Edge Searching Algorithm (BESA). Scalera [7] shows that the computational complexity of this method increases linearly with m whereas the brute force method of facet searching was on the order of m 2 . The theory of the algorithm is not the point of this paper, and is only briefly described here.…”

“…If the desired objective does not lie on the boundary of the AMS, meaning that the objective is inside the AMS, the solution is scaled back appropriately. The description to this direct allocation solution can be found in Scalera [7].…”

“…The theory of the algorithm is not the point of this paper, and is only briefly described here. The reader is referred to Durham and Scalera [6,7] for the theory behind the algorithm and a comparison of the performance with other allocators.…”

“…This method of control allocation takes the control effectiveness matrix B, the set of admissible controls, and some desired objective m d , and determines the intersection of m d with the AMS by checking each facet. After finding the correct facet the controls that generate the point on the facet are calculated [7].…”