Study On Semi-active Fuzzy Control For Two-stage Vibration Isolation System Of Power Unit

As the power source of the diesel coach set,the vibration of power unit directly affects the ride comfort,structural reliability and safety of the vehicle.With the promotion of high power of the power unit system and light weight of the vehicle,it has become an inevitable requirement to improve the vibration isolation efficiency.There is a limited vibration isolation efficiency for the traditional passive vibration isolation system,and it is difficult to meet the vibration isolation requirements of the power unit under multiple operating conditions.As for the active control system,it will be complex structure,high cost and high energy consumption.However,the semi-active control system has simple structure,low cost,low power consumption,high failure safety,and the vibration damping effect is closed to the active control.In this paper,a magnetorheological damper is used as a semi-active control actuator.Then aiming at the broadband vibration characteristics of power unit,a hybrid fuzzy control strategy considering system stability and vibration isolation efficiency is proposed,and a semi-active control simulation system is established.The results show that the appropriate control force can be determined by the control strategy according to the vibration condition of the power unit,and the vibration isolation performance of the system can be improved effectively.In this paper,firstly,the dynamic model of the two-layer vibration isolation system of the power unit with control force is established.The evaluation index of the vibration isolation performance commonly used in the system is summarized.The design method of the fuzzy controller is introduced,and the optimization target and control strategy are determined.Secondly,the genetical neural network is optimized,and the forward and reverse nonparametric models of the magnetorheological damper are established respectively according to the test data,and then the models are tested.Thirdly,according to the modal calculation results of the multi-rigid system,the power unit is simplified in the direction of overturning moment,and the simulated model of the simplified system with 2 degrees of freedom is established.A hybrid fuzzy control is designed for the dual objectives of small vibration intensity in low frequency and small force transmission rate(dynamic reaction force)in high frequency.Based on the above research,a semi-active control simulation system is established,and the effectiveness of the controller is verified under the sweep excitation.Then,a semi-active control simulation system including multi-rigid model with 18 DOF is established by combining ADAMS and Simulink.And the control effect under the power balance and unbalanced conditions is verificated.Considering the influence of structural vibration,a rigid-flexible coupling semi-active control system with flexible intermediate frame is established,and the influence law of the direction and position of the damping control force on the vibration control effect is studied furtherly.Finally,for the non-optimal problem of the scale factor and quantization factor,the genetic algorithm is used to optimize,and the optimization effect of the fuzzy controller is verified under the common working conditions of each gear.The results show that the method of fitness linear transformation,adaptive crossover and mutation probability can effectively improve the convergence speed of genetic neural network,and the model has higher precision and can more accurately reflect the dynamic characteristics of the magnetorheological damper.The simulated results of the semi-active control system show that the sky-hook fuzzy controller can significantly improve the low-frequency stability of the system,but it will reduce the high-frequency vibration isolation efficiency.The ground-hook fuzzy controller has limited effect on low-frequency stability,but has a better performance in high-frequency vibration isolation.The hybrid fuzzy controller combines the advantages of the both,and has good vibration isolation control effect in the full frequency range including power balance and unbalanced conditions.It is found that the control effect on rigid vibration and structural vibration is not only related to the mode shape,but also affected by the position and direction of the damping control force.The genetic algorithm can solve the non-optimal problem of fuzzy controller parameters and improve the vibration isolation efficiency of the semi-active control system.The research results of this paper can provide reference for furtherly improving the system vibration isolation performance and improving the vibration isolation technology of the diesel coach set.At the same time,there are reference value and guiding significance for the whole machine vibration control and system structure vibration control of the power unit.