Trajectory Optimization Procedures for Rotorcraft Vehicles, Their Software Implementation, and Applicability to Models of Increasing Complexity

Abstract

This paper describes numerical procedures for the solution of trajectory optimization problems in rotorcraft flight mechanics. Specifically, procedures are considered that can be easily interfaced with black box flight simulators, with minimal assumptions on such third-party software components, and that can cater to a wide range of vehicle models of increasing complexity. First, the direct approach to the solution of maneuver optimal control problems is identified as the method of choice for this class of problems. Next, the direct transcription and the direct multiple shooting approaches are formulated, their characteristics are discussed, and their respective optimal application areas are identified. Finally, the functionality and architecture of a general-purpose code implementing both methods is described. The capabilities of the proposed procedures are demonstrated with the help of practical examples of industrial relevance, regarding both helicopters and tiltrotors

Identification Of A Nonlinear Grey-Box Helicopter UAV Model

“…69 This issue however does not exist with SCP methods, 71 which is one of the reasons why SCP methods have actively being investigated. 69 In addition, SCP methods are known to be very effective and robust, 70 and SCP techniques have been applied to solve nonlinear optimal control problems, such as in space and launch/reentry applications, 61,62,[72][73][74][75][76] in aircraft applications, 61,[77][78][79][80] in helicopter applications, [81][82][83] in UAV applications, [84][85][86] and glider applications. 87 Since SCP methods have been intensively researched in the last decade, we present next a general overview of this concept.…”

Propeller control for takeoff of a heavily loaded coaxial compound helicopter

“…Hence, they are normalised and scaled to near unity to improve computational efficiency and rate of convergence, detailed can be found in Refs (25,30). A biodynamic model [31] considering pilot response delay is integrated into the dynamic model. After passing through the pilot biodynamic model, the pilot intentions are translated into actual control displacements in the cockpit, presented as…”

Global Solution of Optimization Problems in Rotorcraft Flight Mechanics

“…( 2d)or (3d). Three discretization techniques are available in STOP-namely, the direct transcription and multiple shooting methods (Bottasso et al 2010b) and the recently developed hybrid single-multiple shooting (Bottasso et al 2012). Bottasso et al (2009a) proposes a classification of optimal areas of applicability of these methods and, for each one of them, derives the specific form of the vector of design variables.…”

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formulation of operational procedures for rotorcraft vehicles. STOP has the ability to treat under a common framework both trajectory optimization problems (Bottasso et al 2010b(Bottasso et al , 2012, also referred to in the following as maneuver optimal control problems (MOCPs), and parameter estimation problems (PEPs) (Bottasso et al 2010a). In fact, it can be shown that both can be formulated as two-point boundary value constrained optimization problems defined over a temporal domain of known or unknown duration; moreover, both can be discretized in time using the same techniques, thereby obtaining a constrained nonlinear programming (NLP) problem that is formally identical in the two cases (Bottasso et al 2009a).Some of the features of STOP have already been discussed in a series of previous publications by the authors (Bottasso et al 2009a(Bottasso et al , 2010a.

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