Research On Adaptive Inverse Control Of A Small Scale Unmanned Quad-rotor Helicopter

As the demand for the unmanned helicopter increases both in military and civil field, the relatedresearch is intensified in many companies, institutes and universities. During the last decades, theresearchers in the U.S., Japan, Israel and some European countries obtained some key techniques about theunmanned helicopters and are outstanding in this field. On the one hand, compared to those countries,China had just stepped into this field and there exists a clear gap. On the other hand, its confidentiality laysa technique barrier on communication with the leading institutes in those countries. Therefore, there ishighly demand for self-developing a high quality flight control system for unmanned helicopter andperform some related works.In this paper, the dynamic model of the small scale unmanned quad-rotor helicopter is set up. Theadaptive inverse control （AIC） method is integrated into the control system for the first time and theattitude stabilization control is accomplished. In order to eliminate the steady-state error, the typical AICcontroller is improved according to the characteristics of our helicopter. The results of simulations andexperiments indicate that the improved controller can effectively suppress the interference and eliminatethe steady-state error. The main works for this paper are described as follows:（1） Modeling of the small scale unmanned quad-rotor helicopterThe dynamic model of the small scale unmanned quad-rotor helicopter is the essential part of controllerdesign. Therefore, based on the structure and characteristic of the small scale unmanned quad-rotorhelicopter and the fundamental dynamics of the rotor, the force analysis and controlling method are detaileddiscussed in this paper. In particular, a set of comprehensive dynamic equations are obtained and analyzedby the blade element theory and Newton-Euler theory; the dynamic model of the motor actuator is derived;and the similarity, difference and the scope of application of the small scale unmanned quad-rotorhelicopter and its conventional counterparts are assessed in terms of mechanism, controlling method,mechanical structure and modeling. The proposed dynamic model provides a theory for controller designand further application for conventional helicopter control.（2） Research on AIC theory and its stability at the controlling of small scale unmanned quad-rotorhelicopterIn comparison with the characteristics of adaptive control, the key theory and three critical components of AIC are proposed. Three AIC related algorithms, the least mean square （LMS） algorithm, the modifiednew LMS （MNLMS） algorithm and the recursive least square （RLS） algorithm are evaluated and theirproperties, such as convergence and stability at the controlling of small scale unmanned quad-rotorhelicopter, are proved through theoretical analysis and simulations respectively. Moreover, the discussionof the application of AIC into small scale unmanned quad-rotor helicopter proposed a theory on designingof controller and performance analysis.（3） Design ofAIC controller and analysis of its robustnessA channel AIC controller, which designed according to the characteristics of the small scale unmannedquad-rotor helicopter, provides an iterative-based way to accomplish the translation, rotation and channeldistribution. The robustness of the aforementioned three algorithms are compared through simulation underthe ideal condition, noisy control signal, ambient crosswind and comprehensive interference （all theinterference exist）, respectively. Due to the simulation results, the MNLMS algorithm is preferred forindoor control while the RLS algorithm is prior for outdoor case.（4） Design of hardware/software of flight control systemBoth hardware and software for flight control system of the small scale unmanned quad-rotor helicopterare discussed in terms of avionics and the ground station, respectively. The hardware part includes thedesign of the airframe, key sensors and onboard control circuits. Meanwhile the composition andrealization of the ground station and wireless network are also given. In addition, the correspondingsoftware is also developed.（5） Flight experimentIn order to validate the feasibility of the AIC method, several flight experiments are designed forvarying cases–hovering and figure of eight flying experiment are designed based on the MNLMSalgorithm for indoor case while for the outdoor case, the experiment of hovering, line patrolling andpassing through a narrow door, which takes advantage of the RLS algorithm, are applied. The proposeddynamic model of the helicopter is also proved to be correct through these experiments.The work proposed in this paper lays a solid foundation for realization of the small scale unmannedquad-rotor helicopter control technique and related researches. Meanwhile, it provides a new way whichcan also be applied to control of conventional unmanned helicopters.