Research On Model-Following Flight Control For Tandem Helicopters

Tandem helicopter is a typically multivariable, strong coupling and unstablenonlinear system. Without the action of the flight control system, it is impossible for thehelicopter to meet the performance requirements of the ADS-33E, namely the militaryrotorcraft handling qualities standards adopted widely at home and abroad. In this thesis,the tandem helicopter CH-47was taken as a controlled object, in accordance with therelative HOR level1preformance requirements of the ADS-33E. Model followingcontrol structure was adopted, in which two different eigenstructure assignmentapproaches, i.e. basic eigenstructure assignment and robust eigenstructure assignmentmethods, were used respectively to design helicopter flight controllers. Simulations andperformance calculation were performed to validate the designed helicopter flightcontrol systems.The main research work of the thesis is as follows:1The various performance indexes of the ADS-33E handling quality was analyzed,on the basis of which the design goals of the helicopter flight control system wereproposed.2The control principles and linear mathematical model of the sample helicopterwere discussed with the analysis of the open loop poles distribution and time responsecurves of the linear model.3In the structure of model following control, an ideal model was firstly designedbased on the physical properties of the helicopter itself and the ADS-33E performanceindexes. The basic eigenstructure assignment approach was then utilized to design thecontrol parameters for helicopter flight controller. The results of simulation andperformance calculation have shown that the designed model following control systemof the helicopter basically achieved the HQR level1requirments of ADS-33E, but thecoupling between different channels existed to a certain extent.4Under the circumstance of the same model following control structure and idealmodel as those of the basic eigenstructure assignment approach discussed above, a rousteigenstructure assignment was used to design the control parameters for helicopterflight controller. The results of simulation and performance calculation have shown thatthe designed model following control system of the helicopter not only possessed better decoupling performances, but also completely achieved the HQR level1requirments ofADS-33E. Compared with the basic eigenstructure assignment, the robusteigenstructure assignment can provide a better stability between the helicopter channelsand a more effectively suppress on the coupling phenomenon between the helicopterchannels.