Design And Dynamic Characteristics Analysis Of 6-DOF High Frequency Vibration Platform Of Heavy Load

As the resolution of space remote sensing camera improved greatly, a higher specification has been put to the 6-DOF vibration simulation equipment, and the solution to high-frequency vibration turns to be the bottleneck of improving the vibration simulation’s capacity. This paper designs a 6-DOF high frequency vibration simulation equipment, which employs free-flex pivot and aereostrtic bearing unloading mechanism, to meet the simulation requirement of space remote sensing camera. It is also presented that the study of unloading mechanism’s adaptive capacity to parallel mechanism and the impact on parallel mechanism’s dynamic characteristics duing to the employment of unloading mechanism.Complying with the design criteria of high bearing capacity, high precision and high vibration frequency, free-flex pivot and aereostrtic bearing unloading mechanism are applied to parallel mechanism. Take the natural frequency of 6-DOF parallel mechanism as the objective function to explore the relationship between configuration parameters and the natural frequency of parallel mechanism. By means of multi-boby dynamics simulation obtained the kinematic and dynamic characteristics of 6-DOF parallel mechanism, and a radial stiffness test is carried out to study the circumferentially distribution pattern of free-flex pivot’s radial stiffness.On the basis of 6-DOF parallel mechanism design as well as synthetically consideration of 6-DOF parallel mechanism’s kinematic and dynamic characteristics, the design of aerostatic bearing unloading mechanism is completed. The general expression of Navier-Stokes equation in Cylindrical coordinate system and Cartesian coordinate system is derived, and the influence of aerostatic bearing configuration parameters variation on the static characteristic is analyzed. Finally, through the propertiy test of frictionless cylinder in the unloading mechanism to explore the variation pattern of bearing efficiency and friction.The statics property of unloading mechanism is achieved, as finite element model of unloading mechanism is established. The results show that, unloading mechanism has a good adaptability to 6-DOF parallel mechanism in statics and the cross shaft of huke joint is the relatively weak link. The kinetic equation of unload mechanism is derived and the modal analysis is conducted, while the result turns out that the radial aerostatic bearing is the relatively weak link in the high frequency vibration environment. Static and dynamic analysis show that the weak link of unloading mechanism is different as the work conditions and the location of 6-DOF parallel mechanism is changed. In order to demonstrate the reliability of the design, the fatigue and the harmonic analysis is carried out. The static and dynamic characteristics of parallel mechanism without unloading mechanism is compared with the integrated 6-DOF vibration simulation equipment, to obtain the influence of adding unloading mechanism on static and dynamic characteristics of 6-DOF parallel mechanism.