Research On Extraneous Torque Suppression And Control Strategy Of Electric Load Test Systems For Actuator

The electric load test system(ELTS)is mainly used to detect the technical performance of aerospace vehicles such as aircraft,rockets and unmanned aerial vehicles,which can transform the physical experiment originally performed in the real environment into a simulation experiment in the laboratory.With the increasing control requirements for core weapons such as highly maneuverable and highly accurate missiles,drones and other small high-precision aircraft,the loading performance of ELTS needs to be further improved.Because of the inherent property of the electro-hydraulic load system,such as the servo valve dead zone,pressure fluctuation,extraneous torque,it is difficult to guarantee the load performance in small torque loading conditions.Therefore,it is difficult for the electro-hydraulic load simulator to realize the accurate torque loading of the small aircraft,such as small missiles and small aircraft actuator.In order to study the problem of extraneous torque suppression and high-precision torque loading of ELTS,a prototype was set up using a PMSM.Basised on the prototype,the problem of extraneous torque suppression and high-precision loading of electric loading system is studied so as to improve the performance of electric loading system in small torque loading conditions below 30N?m,and provide theoretical basis and experimental basis for the development of high-performance electric loading system.The following research work was carried out:Firstly,in order to study the loading performance of ELTS in small torque loading conditions,a prototype of ELTS was set up,and then considering the applicability of the control algorithm,the mathematical model was established.For the purpose of achieving parameters of the mathematical model,an improved recursive least squares method was designed.Based on the obtained mathematical model,the basic control performance of the prototype was studied.The loading performance of the prototype was simulated under the control of PID+feedforward controller,which verified that the traditional PID controller could not guarantee the loading performance.In order to obtain higher control performance,considering the nonlinearity of the prototype and the uncertainty of parameters,a fuzzy adaptive robust controller(FARC)is designed and the torque loading simulation research is carried out to verify the effectiveness of the designed controller.It is also show that the controller performance of FRAC is better than the PID+feedforward controller,meanwhile the design of higher performance controller can further improve the torque loading performance of the prototype.For the purpose of designing higher performance controller,the characteristics and composition of the extraneous torque of the prototype are studied.The experimental results show that the extraneous torque of the prototype is not only related to the speed and acceleration of the actuator,but also the Coulomb friction is an important part of the extraneous torque in the case of small torque loading conditions.In order to improve the stability of the controller,a continuous friction model is introduced to replace the traditional segmented friction model.Based on this,a friction model estimation method based on improveed CSA is proposed and then the parameters of the model are obtained.In order to optimize the structure of the controller and improve the stability without affecting the control performance,the obtained equivalent friction model is simplified.According to the mathematical model of the prototype and considering the unmeasured variables and strong external disturbances of the prototype,a state observer based on the T-S fuzzy model including the motion disturbance of the actuator and nonlinearity is designed.At the same time,based on the state observer,considering the obtained continuous friction model,a robust H∞ output feedback control method based on T-S fuzzy model is designed to suppress extraneous torque.Based on the general Lyapunov control theory,the consistent asymptotic stability of the controller is proved.Experiments and simulations are performed to demonstrate the effectiveness of the method for extraneous torque suppression.The model parameters of the actual control system always change with some external factors such as time,temperature,and components aging and wearing.In addition,the saturation of the actuator output presented in the output feedback controller can also affect the stability of the controller.Aiming at the problems of the uncertain parameters,actuator output saturation,disturbances caused by the motion of the actuator and Coulomb friction,which seriously affect the torque loading performance of the prototype,a robust H∞ output feedback controller based on neural network and linear differential inclusion(LDI)is designed.The combination of neural network and LDI achieves off-line linearization of Coulomb friction,improves controller stability and simplifies controller structure.The stability of the controlled system under the condition of parameter uncertainty and actuator output saturation is ensured by the principle of H∞.The disturbance caused by the actuator motion is regarded as the external disturbance of the robust controller.Based on the general Lyapunov control theory,the consistent asymptotic stability of the controller is proved.The simulation and experiment prove that the controller can effectively improve the torque loading performance of the prototype.