Control Strategy Research Of The Loading System Of Air Rudder Load Simulator

As one of the key components of the aircraft,the air rudder is used to control the flight attitude and adjust the flight trajectory of the aircraft.The performance of air rudder directly affects the control precision and stability of the aircraft.In order to guarantee high performance of air rudders,it is necessary to run tests on the ground.The air rudder load simulator provides a reliable experimental guaranteeand technical support for air rudder's ground tests.With the rapid development of China's aerospace and national defense industry,a higher requirement for the rudder load simulator has been set.The research of air rudder load simulator which can precisely reproduce the force load during the flight is imperative.Firstly,this paper reviews the development of load simulator and its control technology,which helps establish the research objectives.In order to realize the load requirements of the air rudder load simulator,the measurement and control system is designed.Then based on the geometric knowledge,the mechanics theory and the fluid theory,the mathematical models of the mechanical system,the loading system,the servo valve and the system under the interference of extra force have been established.Through the oretical analysis of the system's mathematical model,the mechanism of extra force generation has been discussed,based on which the simulations are carried out.Since the loading process of the air rudder load simulator is repetitive and nonlinear,an iterative learning control strategy based on time-varying pilot factor is proposed(Time varying pilot factor-iterative learning control,TPF-ILC for short).In this paper,the convergence of TPF-ILC control strategy is mathematically proved and sufficient conditions are derived under both cases with or without extra force.Thereafter,the critical issue(the initial state problem)of iterative learning is explored.The convergence of the system error and the initial state of every single period have been mathematically proved by using continuous and repetitive characteristics of the system,even if the initial states of every single iterative learning period are not strictly same.The proposed TPF-ILC strategy makes breakthrough over the convention iterative learning theory,which is usually assumed that the initial states of every single period are strictly same.This breakthrough means that the TPF-ILC control strategy has a wider range of applications.Finally,the robustness of the new control strategy is analyzed and the relationship between system error and disturbance is also given,which provides a theoretical support for the issue of extra force's suppression and elimination.The practical application of TPF-ILC control strategy rises up a new issue,that the convergence of system's error is affected by the phase delay of the system.To solve this issue,some measures are made to improve the effect of TPF-ILC.A phase delay factor is introduced into the iterative learning algorithm and real-time phase delay is used to correct system control signal.And a new multi-scale line fitting method is proposed to measure the phase delay of the system.The convergence of the improved TPF-ILC control strategy is also mathematically proved and sufficient conditions are derived.To solve the phase delay problem of traditional digital filter,an on line-EMD(OL-EMD)filtering algorithm is proposed.Then OL-EMD is combined with TPF-ILC strategy and simulations of the torque loading,the loading characters under the influence of friction and the extra force's suppression are carried out.The simulation results illustrate the correctness of the theoretical analysis and the effectiveness of the new control strategy.In order to fully verify this control strategy and the suppression effect of extra force,six groups of different experiments are implemented.The six groups of experiments are sine wave signal loading experiment,triangle wave signal loading experiment,multi frequency compound signal loading experiment with or without extra force.The six groups of experimental results show that the improved TPF-ILC control strategy can reduce extra force by 95%,which proves the effectiveness and practicability of the improved TPF-ILC control strategy.