Research On Planetary Roller Screw Electromechanical Actuator Design And Its Characteristics

Electromechanical actuator(EMA)is the actuator involved in the control of flight position of aircraft.With the development of the aircraft into high speed and high maneuverability,accuracy,response speed,power density are required for EMA at a higher level.Because of the advantages of high rigidity,high power density and high carrying capacity of the planetary roller screw(PRSM),this paper adopts the PRSM as the linear drive element of the EMA,and designs and study the characteristics of the planetary roller screw electromechanical actuator system,which provides theoretical basis and technical support for developing the EMA with high precision,high response and high power density and has a great value for scientific research and practice.In this paper,the objective function is established with the optimal transmission angle,and the parameters of the transmission mechanism of the EMA are designed using the optimization and comprehensive method.The instantaneous transmission ratio of the EMA is analyzed at any position within the output range of the rudder shaft.The stress state of the EMA transmission mechanism under dynamic load conditions is analyzed.The instantaneous swing force and the swinging torque of the EMA transmission mechanism are calculated.The dynamic model of the PRSM is established using the Lagrangian method,and the relationship between relative slip velocity and thread parameter at thread contact point is analyzed.The elastic deformation caused by the transmission mechanism of the EMA is an important factor affecting the position accuracy of the EMA system.In this paper,the EMA transmission mechanism is divided into "rotation-straight line" part and "straight line-rotation" part,whose elastic dynamic models are established respectively.The stiffness curve of the transmission mechanism of the EMA is obtained by solving the elastic dynamic equation.The relationship between the angular displacement and the angular displacement of the transmission mechanism is analyzed.The dynamic characteristics of the EMA directly affect the reliability and safety of the aircraft.In this paper,the modal analysis and harmonic response analysis of both the EMA transmission mechanism and the PRSM were performed using ANSYS simulation software.Considering that the machining error,assembly error and other factors lead to the gap of the EMA transmission mechanism,the dynamic tracking of the EMA is carried out using ADAMS,and the position tracking performance of the EMA under different clearance is analyzed.Pneumatic torque changes make the internal parameters of the EMA change temporarily when aircraft is at high speed and at different altitude.In order to realize the effective adaptation of the controller to the time-varying parameters of the EMA,a control method associating model reference adaptive control strategy with PID control strategy is studied,thus improving the position tracking performance of EMA system.The simulation platform is built by MATLAB/Simulink,and the control performance of the controller is analyzed.Finally,the planetary roller screw EMA is built,and the effectiveness of the control algorithm is validated by the tracking experiment of sine position command with different amplitude and frequency.