| The control accuracy of the rotor speed of the unmanned helicopter has a direct impact on its flight stability and safety,and the stability of the rotor speed depends on the stability of the engine speed,so the constant speed control strategy is a research focus in the design of the unmanned helicopter engine controller.This paper focuses on the constant speed control of an unmanned helicopter engine which needs to be stable at 6500 r/min.The constant speed control of unmanned helicopter engines is important.To address this issue,a bivariate coordinated sliding mode constant speed controller is proposed.In this study,bivariate refers to throttle opening and ignition advance angle.Notably,throttle opening and ignition advance angle,as two important variables for adjusting engine torque,have different characteristics.Throttle opening has a wide adjustment range but a slow responsiveness,which makes it susceptible to overshoot by the effects of time delay.By contrast,ignition advance angle has a narrow adjustment range but a fast responsiveness.If the advantages of these two variables are combined,then the constant speed control effect could be further enhanced.For this purpose,firstly,the engine engine and load of the unmanned helicopter was mathematically modeled.Then the engine bench test,the helicopter mooring test and flight test were designed and completed,and the parameter identification of the mathematical model was completed based on the test data.On the basis of the model and sliding mode control,a bivariate coordinated control strategy was designed.The strategy includes a master logic,spark advance priority adjustment based on sliding mode,and spark advance angle regression logic.Finally,the genetic algorithm was written in MATLAB,and the key parameters of the controller were optimized by using genetic algorithm.Finally,the effect of the control strategy was verified by simulation and experiment.The simulation results showed that,when the load changes abruptly,the bivariate coordinated sliding mode controller reduces the speed overshoot by 61%compared with the traditional PID controller.Furthermore,on the basis of sliding mode control,the bivariate coordinated controller reduces the speed overshoot by21.4% compared with the bivariate separated controller.Moreover,when the load and intake disturbance is simulated,the proposed controller has better anti-interference capability than the two other controllers.And good speed control effect was also obtained when simulating real flight conditions.Finally,the results of the helicopter mooring experiment showed that the speed overshoot of the bivariate coordinated sliding mode controller is 24% smaller than that of the bivariate separated sliding mode controller and 62% smaller than that of the traditional PID controller.The results of multiple experiments showed that the speed fluctuation range is within6500±70 r/min using the bivariate coordinated sliding mode controller,and the ratio of overshoot to target speed is within 2%,which proves that the bivariate coordinated controller satisfies the flight stability requirements for unmanned helicopters. |
