Mechanical Stiffness Modeling And Dynamics Simulation Of Servo Electric Cylinder System

Servo electric cylinder,as a kind of linear actuators,enjoys more advantages in terms of transmission efficiency,environmental adaptability,structural complexity and positioning accuracy when compared with hydraulic cylinders and air cylinders.At present,servo electric cylinders have been widely used in ports,automated factories,aerospace,robotics and scientific research installations.With the large-scale application of servo electric cylinders in many industries,requirements for positioning accuracy and dynamic characteristics get higher and higher.For the semi-closed-loop servo electric cylinder,its mechanical stiffness of the transmission system has a great influence on the positioning accuracy.Although domestic scholars have done a lot of researches on servo electric cylinders,they mainly focus on structural design,optimization of core components and construction of test benches.Few studies have been conducted on the mechanical stiffness of servo electric cylinder drive systems.In this paper,on the basis of “10t servo electric cylinder” jointly developed by a company,research has been carried out as follows:(1)The basic composition and working principle of the servo electric cylinder have been briefly introduced.The equivalent axial stiffness model of the ball screw pair,the equivalent axial stiffness model of the synchronous belt,the axial stiffness model of the bearing set and the axis of the push rod have been analyzed respectively.According to the transfer path of motion and force,all links of the servo electric cylinder drive system are equivalent to a list of series-wound spring masses.Then,based on the Hooke' s law,the mechanical stiffness model of the servo electric cylinder drive systems has been obtained.(2)Based on the servo electric cylinder stiffness model,the influence caused by each link of the semi-closed-loop servo electric cylinder drive system on its positioning accuracy has been analyzed with less influential links neglected and more influential ones optimized.Research shows that the positioning accuracy and mechanical stiffness can be remarkably improved by imposing the pre-tightening force.Meanwhile,increasing the structural size of the servo electric cylinder within a certain range can significantly improve the positioning accuracy and mechanical rigidity of the servo electric cylinder.However,the larger the increase of the structural size is,the smaller the lifting effect gets.(3)The mathematical model of servo electric cylinders has been set up,mainly including the permanent magnet synchronous servo motor and the mechanical model that involves the dynamic stiffness of the transmission system.Through MATLAB/Simulink,steady-state errors in the context of different load and working stroke have been obtained by simulation.Increasing the mechanical stiffness the transmission system can reduce the overshoot of the system and improve the stability.But the response time of the system is less effected by the change of stiffness.