Research On Magnetorheological Braking Technology Of Downward Belt Conveyor

In the braking system of belt conveyor,the traditional friction braking or hydraulic braking will cause a series of problems,such as heat fade,braking squeal,brake shore wear.More importantly,the brake torque can't be continuously regulated.As a new type of linear control actuator,magnetorheological fluid brake can make up for these shortcomings.The MR brake has the advantage of low energy consumption,short braking time,small wear of components,adjustable braking torque,convenient integration of new control technology,etc.And these advantages are very consistent with the braking requirements of the belt conveyor.For this problem,a novel MR brake with double coils placed on side housing was designed and applied to the brake system of the small down belt conveyor.In order to achieve the purpose of increasing the braking torque and realizing the lightweight design,it was proposed on the improvement of the conventional hybrid MR brake.First of all,the braking mechanism of MR brake was simulated from the microscopic point of view,and the dynamic simulation model of magnetic particles in MR fluid was established.And then the effects of the volume fraction of MR fluid and the magnetic field on the microstructure of the chain were studied.And,the shear process of magnetic particles under magnetic field was simulated.Secondly,taking a small belt conveyor as an example,the braking torque was calculated.According to the required braking torque,a novel MR brake with double coils placed on side housing was designed.And,the torque model and design method of magnetic circuit of the novel MRB were proposed based on Herscher-Bulkley model.In order to achieve the purpose of increasing the braking torque and realizing the lightweight design,a combined optimization design method based on the finite element analysis(FEA)and multi-objective genetic algorithm(MOGA)was proposed.Then,a solution of optimization problem of the magnetic circuit structure parameters was extracted through the Pareto optimization based on the optimizing method of combination weighting of multi-attribute decision making.Finally,a new apparent viscosity definition of MR fluid is obtained by the modifying the Bingham model,which was employed to connect the communication of magnetic field,fluid dynamics,and temperature field.Then,the kinematics equations of the MR brake were established to evaluate the rotation law of the brake disk and the total brake time.And then,multi-physics modeling was established with sequencetial coupling method,which were based on the Maxwell equations,Naiver-Stokes equations and conjugate heat transfer equations.The steady state temperature distribution of MR brake under non braking condition of down belt conveyor was obtained.And then,the magnetic field distribution,the flow field distribution and the transient temperature distribution of the MR brake under braking condition of down belt conveyor were also obtained.The results show that the designed MR brake with double coils placed on side housing can meet the needs of small belt conveyor.The results can be reference for the structure design,magnetic circuit design and optimization analysis of the MR brake.It also provides a new choice for the braking mode for the belt conveyor.