Hayrani Oz

Optimization for efficient structure-control systems

The efficiency of a structure-control system is a nondimensional parameter which indicates the fraction of the total control power expended usefully in controlling a finite-dimensional system. The balance of control power is wasted on the truncated dynamics serving no useful purpose towards the control objectives. Recently, it has been demonstrated that the concept of efficiency can be used to address a number of control issues encountered in the control of dynamic systems such as the spillover effects, selection of a good input configuration and obtaining reduced order control models. Reference (1) introduced the concept and presented analyses of several Linear Quadratic Regulator designs on the basis of their efficiencies. Encouraged by the results of Ref. (1), Ref. (2) introduces an efficiency modal analysis of a structure-control system which gives an internal characterization of the controller design and establishes the link between the control design and the initial disturbances to affect efficient structure-control system designs. The efficiency modal analysis leads to identification of principal controller directions (or controller modes) distinct from the structural natural modes. Thus ultimately, many issues of the structure-control system revolve around the idea of insuring compatibility of the structural modes and the controller modes with each other, the better the match the higher the efficiency. A key feature in controlling a reduced order model of a high dimensional (or infinity-dimensional distributed parameter system) structural dynamic system must be to achieve high efficiency of the control system while satisfying the control objectives and/or constraints. Formally, this can be achieved by designing the control system and structural parameters simultaneously within an optimization framework. The subject of this paper is to present such a design procedure.

Evolutionary Energy Method (EEM): An Aerothermoservoelectroelastic Application

Abstract Evolution means a process of change in a particular direction, evolutionary being the adjectival form of the word. This chapter is based on a novel theoretical foundation introduced by the author as the Evolutionary Energy Method (EEM) finding its root in the natural law of energy conservation, specifically the First Law of Thermodynamics. To this end, the Law ofEvolutionary Energy (LEE) is introduced as the encompassing foundational evolutionary equation, where the evolutionary operator Ð is a directional change operation via parameter alterations on the energy-quantities satisfying the energy-conservation law along the actual dynamic path, and acts on the total evolving energy, which is defined as the time integral of the total actual energy interactions in a dynamic system. The EEM is an algebraic (direct) energy method; that is, it uses and needs no knowledge of differential equations of the system for response and/or control studies of dynamic systems. Introduction of the concept of Assumed-Time Modes (ATM) for the generalized response variables and generalized control inputs of a dynamic system in conjunction with the Law of Evolutionary Energy culminates in elimination of time from the system dynamics completely, yielding the Algebraic Evolutionary Energy description of the system dynamics for response and control studies. As an application of the EEM, an aerothermoservoelectroelastic system is described completely algebraically and illustrated for studying the feasibility of structural skin temperature control in Mach 10 hypersonic flight by using optimal distributed control actuation. The structural temperature and the structural deformation are controlled simultaneously by using only temperature-feedback optimal control laws via elastothermoelectric actuation.

Aeroservoelastic design with distributed actuation for high-performance aircraft

A new aeroelastic modal formulation in terms of real modal matrices and modal-state variables is introduced. Real biorthonormality relationships for aeroelastic modes are given with respect to structural matrices. The solution for distributed-parameter-control of an aeroelastic system is developed by modal synthesis from modal-state-space control inputs. In particular, the globally power optimal Independent Modal-Space Control technique is used for maneuver (set-point) control of an aeroelastic system by a modal-performance-output synthesis approach. Control power functionals for an aeroelastic system are defined by any actuation profile and control design. The known solution for the synthesized distributed-parameter closed-loop aeroelastic system is optimally approximated via a gain distribution error minimization technique integrating the transient and power performance characteristics of the system for implementation by distributed, spatially-discrete actuation profiles. For the same purpose, a Galerkin approximation is also given. The method is illustrated for a lifting surface simulating a wing to twist the wing tip to a prescribed angle of attack by using different distributed actuation profiles. Various warped wing shapes can be affected by the approach by synthesizing through different selections of aeroelastic modes for control design resulting in different control power requirements.

Wing shaping for optimum roll performance using independent modal-space control technique

A technique for deforming a flexible wing to achieve a specified roll rate within a specified time at different Mach Numbers is examined. Rather than using an aileron system for roll, antisymmetric elastic twist and camber is determined to achieve the required rolling moment for a specified roll rate. The elastic twist and camber is achieved by providing a system of actuating elements distributed within the internal substructure of the wing to provide control forces. The modal approach is used to develop the dynamic equilibrium equations which culminates in the steady roll maneuver of a wing subjected to aerodynamic loads and the actuating forces. The distribution of actuating forces to achieve the specified steady flexible roll rate within a specified time was determined by using Independent Modal-Space Control (IMSC) design approach. Here, a full-scale realistic wing is considered for the assessment of the strain energy required to produce the antisymmetric twist and camber deformation to achieve the specified roll performance.

Roll maneuvering of flexible aircraft with distributed-parameter actuation via modal synthesis

The focus is on obtaining and identifying optimal distributed- parameter-control equivalent actuation profiles for desired roll maneuvers by a modal synthesis approach. The solution for distributed-parameter-control of an aeroelastic system is developed by synthesis of modal-state-space controllers designed via the globally power optimal Independent Modal- Space Control (IMSC) technique. The desired maneuver (set- point) control performance is achieved by a modal-performance- output synthesis (MPOS) approach. The MPOS approach requires that each independent modal controller be allocated a desired portion of the total desired output performance. In view of this, a modal performance-output allocation optimization problem is also defined, which minimizes a hybrid measure of control power and elastic strain energy of the structure during aeroelastic control. Insight to distributed-parameter- control equivalent actuation solutions are sought by considering the aeroservoelastic interactions among vehicle motion, aerodynamics, structural flexibility and control actuators from the perspective of work-energy, control power, and control loading requirements. The modal synthesis approach is illustrated for a flight vehicle wing design to achieve a 90 deg/sec roll-rate in a Mach 2 flight condition at altitude (20000 ft) via distributed-parameter equivalent actuation. The preliminary results indicate that such a roll-rate maneuver can be accomplished via distributed-parameter actuation with feasible levels of control power, work-energy, and control loadings through eliciting favorable aeroservoelastic interactions.