Nonlinear Analysis And Control Of EMA With Ball Screw Drive

Electromechanical actuator (EMA) is an important sub-system in the control ofmissile. It is steerred by the signal stemming from autopilot, and changes the flightattitude of missile, thus it directly affects the capability of missile. Influenced bymanufacturing technology, assembly precision, EMA contains many nonlinearfactors, such as clearance and friction. Meanwhile, with the design of EMA tends tohigh bandwidth and lightweight design, the elastic deformation of EMA componentshave a serious effect on the performance of EMA. For these reasons, it is urgent tocarry out the research on influence of clearance, friction and elastic deformation ondynamic characteristics of EMA, and adopt efficient methods to lessen, inhibite orremove the adverse factors. This paper focuses on an EMA with ball screw drive.Firstly the theoretical analysis and simulation on nonlinear factors were presented.Then, control theory of EMA was studied based on above analysis. At last,experiments were performed. This paper is organized as follows.(1)Firstly, according to the system indicators of EMA, load matching,component selecting of EMA were implemented. Secondly, structural dynamicmodel of EMA were established based on the Lagrange’s equations of the secondkind. Finally, modal analysis and harmonic analysis of EMA were simulated byANSYS software, which obtained natural frequency and mode shape of EMA. As aresult, the structure meeting the requirements of system indicators was designed. (2)Considering the influences of clearance, friction and elastic deformation onEMA, a simple model for EMA in the framework of multibody systems formulationwas presented by cartesian coordinates. Then, numerical simulation of nonlinearEMA was performed using ADAMS soft. The simulation results show that nonlinearfactors can significantly affect the dynamic response of EMA.(3)Because electromechanical actuator (EMA) is a nonlinear, time-varyingservo system, the method of improved Active Disturbance Rejection Controller(ADRC) was proposed to improve the tracking performance of EMA. The newcontroller was established by removing nonlinear tracking-differentiator, andemploying linear state error feedback, linear extended state observer and Falfunction filter system. Simultaneously, the stability of the controller was proved andselection principle of the controller parameters were presented based on ModernControl Theory. In order to further improve controller performances, improvedADRC parameters were optimized by NSGA-II algorithm. United simulationincluding the model of nonlinear EMA and improved ADRC was established byADAMS and MATLAB/Simulink respectively. The feasibility of this controller wasdemonstrated through simulation under different input conditions. It is exactly toprove conclusively that the system static and dynamic performance is improved byoptimized controller.(4)For the purpose of designing nonlinear controller based on the observer,nonlinear PID controller based on disturbance observer and PID_LQR Controllerbased on reduced-order observer were designed respectively in the paper. Throughsimulation, the validity of these methods was testified. Simulation results show thatboth improved controllers have good following performance and robustness.(5)Semi-physical simulation system platform was builded. The performance ofPI controller, ADRC, improved ADRC were compared on EMA. Experimentalresults of improved ADRC indicate that rise time, overshoot and the steady statemean square deviation of EMA are8~17ms,0~8.25%,0.0094~0.0129respectivelywhen±1°~±18°angle are tracked. When the tracked angle is15sin(5πt), the phase error is0.06543rad, and there is no position flat crest and velocity dead space,whichhave the advantage over PI controller and traditional ADRC. It can be concludedthat the improved ADRC has a fast response, slight overshoot and high accuracy instability, as well as strong anti-disturbance and robustness. Thus, dynamicperformance and steady precision of the system are both improved.The paper taked into account nonlinear factors in EMA, and presented rigidflexible, nonlinearity, electromechanical coupled research technique on EMA bycomprehensive analysis. In a word, the research comes up with a new study concepton EMA and has a certain reference value to the further study of EMA with ballscrew drive in the future work.