Research On Vibration Control Of Crane Slewing Mechanism Based On Magnetorheological Technology

In view of the slewing mechanism of crane,during emergency starting or braking,because of the huge moment of inertia in the upper rotary structure,a severe vibration impact on the gear mesh,easy to cause the slewing gear damage failure problems.Proposed a method of controlling the impact load based on magnetorheological technology,that is,by changing the stiffness and damping characteristics of the slewing mechanism combined with semi-active control strategy to realize the impact load peak and start braking time optimization.According to the structure characteristics of the crane slewing mechanism and the materials properties of magnetorheological elastomers,detailed structural design and magnetic circuit simulation of magnetorheological coupling are carried out in this paper,and the relationship between the coupling torsional stiffness coefficient,damping coefficient and the control current is also derived theoretically.Establishing the system dynamics model which contains backlash,the gear meshing stiffness,external excitation,nonlinear torsional stiffness coefficient and damping coefficient,and deriving of the model key parameters,then the complete differential equation of vibration is obtained.By using MATLAB to solve the numerical simulation of system dynamics model,the dynamic response of the system is obtained.Through the data processing to assess the safety of rotary gear,to study the coupling torque transmission capacity and damping energy dissipation characteristics,to predict different current and different velocity and different backlash's effect on the movement characteristics of the system,as well as the inhibitory effect on the impact peak.Combining the dynamic characteristics of magnetorheological coupling,the paper designs dual mode control and the PID control strategy applied to the slewing mechanism,which can make the coupling current in accordance with the dynamic responses of the system adjust adaptively.Also,the paper predicts and compares the control effect of two kinds of control strategy.Then,through the analysis of the impulse,a preliminary analysis on the control mechanism of the coupling by impulse analysis is made.The results show that in the process of starting or braking,there is a severe vibration shock in the slewing mechanism,and the vibration impact load will exceed the allowable bending stress of gear.In this paper,the magnetorheological elastomers coupling can meet the working demand of equipments having large torque and heavy load,like the crane slewing mechanism,and has strong torque transfer capacity.Its damping energy dissipation is very small,and does not affect the transmission efficiency of the crane slewing mechanism,also can achieve rapid starting and braking.It can effectively restrain the peak of the vibration response of the system to the impact load,and with the decrease of the input current of the coupling,the peak value will be gradually reduced,but it also has the problem of prolonging the start-stop time.Through the strategy of semi-active control adjusting the size of the input current,we can further balance the energy distribution of impact load,especially the PID control,and make the impact peak and start-stop time doubly optimize.Then the working conditions of the rotary gear are improved,and the safety and operation of comfort of crane slewing mechanism are improved too.