Research On Multi-frequency Vibration Control Of Semi-active Vibration Isolation Platform With Time Delay

With the development of science and technology,precision instruments in aerospace,precision machining,precision measurement and other fields have higher and higher requirements for environmental vibration,so micro-vibration control has also received more and more attention.Traditional passive vibration isolators cannot meet the demand for vibration isolation under complex excitation.The semi-active vibration isolator based on magnetorheological elastomer(MRE)is a magnetically controlled intelligent vibration isolation device with the characteristics of low power consumption and good stability.Only a small current is required to generate the magnetic field to make the stiffness or damping of the vibration isolation structure change significantly.So,MRE becomes a research hotspot in the field of vibration control.In vibration engineering,multi-frequency vibration is a common form of vibration.Due to its complex frequency components,it is difficult for conventional control methods to achieve ideal control effects.In addition,the influence of time-delay in control system cannot be ignored.It may deteriorate the control performance or even cause the system to be unstable.The time-delay is another difficulty in vibration control system.Therefore,this thesis has carried out the following researches on the multi-frequency vibration and time-delay in the MRE semi-active vibration isolation platform:①A single-degree-of-freedom dynamic model of the precision platform magnetorheological elastomer vibration isolation system is established,and the system parameters are obtained from the frequency sweeping experiments.Besides,the semi-active control conditions and the design of semi-active fuzzy controllers are studied,and a fuzzy controller optimization method based on genetic algorithm is proposed.Then a simulation and experiment was carried out,and the results showed that the optimized fuzzy controller has a better attenuation effect.②The time-delay of the MRE vibration isolation system is analyzed and the time-delay of this control system is estimated.The MRE vibration isolator response time test system was set up to test the response time of the vibration isolator under different displacement and step voltage.The response time of MRE isolator has become the focus of research.It is found that the eddy current effect in the MRE vibration isolator is the key factor affecting the response time of the magnetic field.The method of slotting MRE isolator is proposed to reduces the eddy current effect.Simulation and experiment results show that the response time of the magnetic field in MRE isolator is effectively reduced with proposed method.③A fuzzy control with constant time-delay compensation is designed for the MRE vibration isolation system under sinusoidal excitation.The constant time-delay compensation value with the excitation frequency in the range of 34Hz-51 Hz is determined based on experimental results and proposed time delay compensation theory.Experiments are carried out under single-frequency excitation and three-frequency excitation conditions.The experimental results show that the fuzzy controller with constant time delay compensator can suppress both single-frequency excitation and multi-frequency excitation of 34Hz-51 Hz,and the control energy consumption is also lower than that of conventional fuzzy control.Under single-frequency excitation,the vibration attenuation rate is up to 54%,and the power is reduced by up to 35%.④The conventional fuzzy controller is difficult to achieve satisfactory control effect under the excitation of multi-frequency,so the simulation is established to design the frequency division fuzzy controller.Each frequency components of the multi-frequency vibration are separated through filters and controlled separately.Finally,based on The weights optimized by the genetic algorithm synthesize the control signals.The simulation results show that the proposed frequency division fuzzy control algorithm can effectively suppress the vibration of each frequency component.Then the MRE vibration isolation platform vibration control experimental system was built.Time-delay compensation was added to the frequency-divided fuzzy controller.The experimental results show that the acceleration of the vibration isolation platform was attenuated 31% at most,the proposed algorithm can achieve better attenuation effect with less energy consumption.