Study On Active Precision Vibration Isolation System Based On Parallel Of Positive And Negative Stiffness Springs

Active precision vibration isolation system is one of the most necessary guarantee for the generation of nano-precision in ultra-precision machining, manufacturing and measuring equipment. It aims at eliminating the adverse effects of micro-vibration by preventing the transmission of external vibration. With the improvement of accuracy of ultra-precision equipment, the requirement for vibration isolation system is more and more stringent, and further improvement of the isolation performance becomes very hard.In order to fulfill the urgent requirements of state key scientific research and engineering projects, the novel vibration isolation units and effectively active control strategy are the main two aspects studied in this dissertation. The characteristics analyzing, modeling and optimization of the key units, design of active control and realization of prototype are studied to further enhance the performance of the vibration isolation system for the increasingly stringent performance requirements.The key factors affecting the performance of the vibration isolation system are elaborated clearly, and the novel concept by combing the positive spring with negative element in parallel is proposed. Magnetic spring with negative stiffness based on magnetic attraction is modeled by using magnetic charge model. Optimization of magnetic size is carried out to decrease the nonlinearity of the stiffness characteristics. The principle of magnetic spring with negative based on magnetic repulsion is proposed in this dissertation, and a single degree of freedom vibration isolation device is built to verify the correctness and effectiveness of this principle.In order to study the control strategy of the vibration isolation system, the model of system is built.By the analysis of vibration source and the characteristics of the passive vibration isolation system, the control strategy is considered and determined. For the purpose of solving the contradiction between high and low frequency vibration isolation performance, a modal decoupled control scheme using skyhook damping for the six-degree-of-freedom vibration isolation system is presented. According to the requirements for the precision positioning and high performance of the vibration isolation system, the hardware and software system of active controller are designed and implemented. In order to validate the studies of this dissertation, the testing system is established. Test results demonstrate that transmissibility of base vibration at frequencies upon2Hz is less than10%, and less than1%at frequencies upon10Hz. The active vibration isolation system is applied in vibration isolation frame of lithography, and the final performance tests in time domain and frequency domain are carried out. The positioning accuracy of±4μm is achieved in vertical, and transmissibility at natural frequency is less than1. From all the test results, the novel vibration isolation units and active control method studied in this dissertation is validated.