Research On Flight Control Strategies For Electric Unmanned Helicopter With Variable Rotor Speed

Unmanned helicopters are widely used in military and civilian fields because of its unique flight characteristics.With the development of helicopter technology,on one hand good flight qualities are required,on the other hand,specific demands for the endurance,range,flight altitude and maximum forward speed are put forward.Taking variable rotor speed technology into consideration is an effective way to decrease the required power of helicopter,which however increases the complexity and uncertainty of the flight control system at the same time.Therefore,a more reliable flight control system is required.This paper presents a method of measuring rotor speed using soft sensor,a strategy to optimize rotor speed and an adaptive flight control method.First of all,the nonlinear dynamic model of prototype helicopter is established.The relationship of trim results at different rotor speeds is studied,which proves the effectiveness of using variable rotor speed to decrease the required power.The influence to the stability of variable rotor speed is analyzed according to the linearized model.Secondly,the research of rotor speed measurement is carried out.A soft sensor is developed for the rotational speed measurement of an electric propeller.According to the bench test,the soft sensor proves a high accuracy.In addition,a two-loop rotational speed control system is developed using soft sensor to realize the accurate control of rotational speed.Thirdly,an optimization method based on simulated annealing algorithm is introduced to minimize the required power of helicopter.An adaptive attitude tracking control method which combines model reference adaptive control method with model following control method is proposed.On this basis,the altitude,velocity and position control laws are presented,which realize stable flight control of helicopter with variable rotor speed.Finally,a dual core flight controller consist of DSP and STM32 is designed,based on which flight control tests of fixed rotor speed and variable rotor speed are carried out.Results show the stable control of helicopter with variable rotor speed and the decrease of required power using variable rotor speed in different flight conditions.