Research On Force Feel Simulation Of Control Loading System On Flight Simulator

Flight simulator is an important equipment for training pilot. Control loadingsystem(CLS), as one of key subsystems on flight simulator(FS), mainly providecontrol force feel of control columns and pedals for training student pilots，so that itcan realistically reproduce the control force feel of controlling the real airplane.This thesis is upon the background of “985Project” Phase II to develop Keytechniques of flight simulator and test platform, which is developed by IEST. Thekey technical of force feel simulation for control loading system is investigated,including surplus force retraining, inner loop bandwidth expanding and out loopstability enhancing. Then, the corresponding control strategies are further studied.To study the key technical of force feel simulation, the control structure ofloading system is considered as to be consisted of inner loop and an outside loop.The inner loop is a force loop, which is an electro-hydraulic loading system. Theoutside loop is consisted of control mechanism, force function model and innerloop，which takes control force as input and takes control displacement as output, sothat it can be seen as a force-displacement impedance. Through analyzing the effectsof inner loop surplus force, inner loop bandwidth and control mechanism parameterson frequency characteristics and stability of that impedance, constrains of inner loopbandwidth and surplus force are proposed, as well as outside loop stability criterion.Aiming at inner loop surplus force restraining, a control strategy combinedfeed-forward velocity compensation(FVC) with feed-forward inverse modelobserver(FIMOB) is proposed which is for the limitation of FVC. Then, sufficientstable condition of FIMOB structure is derived and a method to design observertransfer function is proposed and its rationality is proved, which can further restrainthe surplus force compensated by feed-forward velocity. Then the stability of thewhole CLS based on that compound controller is analyzed, and a dampingcompensation strategy is proposed to enhance system stability.To achieve the quantizing design for Q(s) of FIMOB to realize the robustperformance closed to optimum, a indirect optimal method for Q(s) is proposed,which firstly transforms the FIMOB structure into a2-DOF control structure withboth feed-forward and feedback controllers containing Q(s). Meanwhile, theequitation for restring surplus force between the transformed2-DOF controlstructure and FIMOB is derived. Then H∞optimization algorithm is used to solvesuboptimum feedback controller in transformed2-DOF control structure, and theoptimized Q(s) can be further solved according to the obtained feedback controller.In the processes of optimized controller design, the inverse model of observer transfer function is taken as the nominal model，which is a biholomorphic transferfunction and not satisfying the condition of H∞optimization algorithm. A method ofnominal model amended is proposed for that problem. An optimizing algorithmbased on method of bisection for performance weighting function is proposed,which can improve the robust performance of optimized system as far as possible.Then it is analyzed the robust stability and the affecting factor of ability forrestraining surplus based on optimized Q(s).Aiming at expanding the bandwidth for inner loop in premise of enhancingstability of outside loop, a compound outside loop control strategy combined withfeed-forward inverse model (FIVM) control and μ control is proposed.Feed-forward inverse model control technical is firstly used for expanding innerloop bandwidth. Meanwhile, it can transform the inner loop as a form of straight–through moment with a model perturbation, so that it is avoided analyzed that howthe specific form of inner loop to effect the outside loop stability. After that, themodel uncertainty of outside loop is analyzed, then the outside loop is transformedinto a structure with multiple model perturbations, and the range of controlmechanism model perturbation is derived. Finally, μ controller is designed forenhancing outside loop robust stability.Ground on key technical of force feel simulation for control loading system, aseries of experiments are carried out on the hardware-in-the-loop-simulation CLSplatform based on RT-LAB rapid control prototyping (RCP), through which thereasonability of the analyzed conclusion and the efficiency of control strategies areproved. The controllers are designed according to specific force feel simulationobject. Then, the experiments are carried out from these aspects, the tracking abilityof inner loop, the efficiency of surplus force restraining, stability of outside loop andtime domain response characteristic of outside loop impedance. It is can be derivedthe conclusions that the designed inner loop compound controller can restrainsurplus force effectively, the proposed damping compensation strategy can enhanceoutside loop stability, and the designed compound outside loop controller canexpand inner loop bandwidth in premise of keeping outside loop stable so that thecharacteristic of outside loop impedance comes closer to the force feel characteristicof force feel simulation object.