Dynamic Modeling And Experimental Research On Active Vibration Isolation Platform With Flexible Connection

High resolution is an important direction for our country’s satellite development.An important technical problem that must be overcome in this process is the control of satellite micro-vibration.At present,using parallel platforms to achieve micro-vibration vibration isolation attracts widespread attention from domestic and abroad scholars.Among many parallel vibration isolation platforms,the Stewart platform is the most typical and widely used because of the best vibration isolation effect.Therefore,the design and improvement research of the active control system based on the Stewart parallel platform is of great significance for solving practical vibration isolation problems in engineering.In this paper,the target of the research is the Stewart parallel platform structure.Based on the research of the rigid platform,a suitable flexible hinge is designed to replace the original rigid hinge for eliminating the influence of friction and gap.The flexible Stewart platform is systematically studied from various aspects.The specific research content includes:(1)Simulation and Experimental Study on Rigid Stewart Platform.Firstly,the rigid platform ADAMS virtual prototype model is established,and the natural frequencies are compared and verified through experiments.Secondly,the common control algorithms PID,LQR and H∞ are used to carry out the dynamic co-simulation analysis respectively.The simulation results are compared and displayed.Afterwards,the advantages and disadvantages of these three control algorithms for the rigid Stewart platform system are studied.Finally,a physical prototype is built based on the geometric model and the experimental study is conducted on the vibration isolation performance.Similarly,the control effects of the three control algorithms in the experiment are compared and analyzed.(2)Design of flexible hinges and improvement of electromagnetic actuators.Firstly,the characteristics,types and materials of the flexible hinge are briefly analyzed and explained respectively.The appropriate flexible hinge configuration and material are selected according to the actual situation of this paper.After that,the designed flexible hinge is further analyzed to ensure that it is suitable for the vibration control of the Stewart parallel platform.On the other hand,the electromagnetic actuator used in the rigid Stewart platform are improved.The defects of the old actuator and the advantages of the improved actuator are analyzed.Finally,the vibration performance of the improved actuator is analyzed and verified by the experiment and compared with the old actuator.(3)The establishment and verification of the flexible Stewart platform model.Based on the systematic research of the rigid Stewart platform,the dynamic equations of the flexible Stewart platform are derived by Kane equation combined with the virtual power principle.Firstly,the model and the introduced coordinate system are described.Then the velocity and acceleration of each part of the Stewart platform structure are obtained by kinematic analysis.Finally,the balance equation is listed by the virtual power principle.By considering that the vibration amplitude is small and the characteristics of the micro-gravity space environment,the simplified form of the dynamic equation of the flexible Stewart platform is obtained,and the correctness of the equation is verified by simulation.(4)Experimental research on the flexible Stewart platform.To verify whether the actual flexible Stewart platform can achieve the desired vibration isolation effect,the experimental study is conducted on the constructed physical prototype.Firstly,the accuracy of the theoretical model is confirmed by verifying the consistency of the natural frequency.Secondly,the acceleration response of the payload is measured in the case of vertical and horizontal sweeping and fixed-frequency sinusoidal excitation from the base platform.The attenuation amplitude of the acceleration response is used to verify the feasibility and effectiveness of the flexible Stewart platform vibration isolation system proposed in this paper.Finally,for simulating the space satellite payload realistically,the vibration isolation performance experiments with the flexible payload are studied.