Synthesis of a fuzzy-logic based navigation controller for “Raptor” small-size helicopter
Control and navigation systems
Kazan National Research Technical University named after A.N. Tupolev, KNRTU-KAI, 10, Karl Marks str., Kazan, 420111, Russia
The paper considersthe problem of synthesis ofa fuzzy-logic based control law for the Raptorsmall-size unmanned helicopter, which operates in thepresence of parametric and external disturbances, with incomplete measurement of the state vector. At that the angle error and its rate of change are available for measurement.
The fuzzy-logic basednavigation controller is developed by using the Mamdani approach. It is built separately for outerand inner control loopcircuits. One of the specific features of the fuzzy-logic based controller consists in the fact that it can be used to control a complex object, the precise mathematical description of which is absent.In addition to that the fuzzy-logic based controller is able to preserve the quality of control in the presence of parametric and external disturbances.
The main difficulty in designing a fuzzy controller consists in determining its tuning.The tuning of fuzzy-logic basedcontroller is performed according to the results of the functioning of the auxiliaryfixed-logic basedcontrollers in orderto simplify the control law synthesis. Such fixed-logic based controllerscan be implemented sufficiently easily, but they do not provide the required quality of control.Thetuning of the fuzzy-logic based controller for the inner loop of angularstabilization is performed based onthe results of functioning of the auxiliary controller, which is built according to the backstepping method with the usageof the Lyapunov function. The tuning of the fuzzy-logic based controller for theouter loop of spatial motion is performed according to the results of functioning of thepreviously developed controller with observers.The outer control loop generates the command for the inner loop in the form of the desired pitch and roll angles.The inner loop generates the command for the deflection ofthe helicopter control sticks. Each channel uses two input signals: the command error and its rate of change.At thateach input and one output use seven membership functions ofGaussian type, whichare connected byforty-nine rules.
The control algorithm efficiency is confirmed throughsimulation according to the requirements of the ADS-33Estandard, which is a recognized criterionof evaluation of handling qualitiesof military helicopters. The pirouette maneuver was used for helicopter flight simulation.The developed control algorithm was also tested on the laboratory helicopter test rig with two degrees of freedom.The experiment has confirmed the efficiency of the fuzzy-logic based controller in the presence of external and parametric disturbances.
Keywords:fuzzy logic, small-size helicopter, control law synthesis
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