| The permanent magnet eddy current is the main mode of eddy current braking because of its simple structure,stability,reliability and pro-environment.This paper completes the overall design of permanent magnet eddy current anti-falling device for satisfying the brake requirements.According to the structural features of construction hoist and the crane,the permanent magnet eddy current brake technology has been applied in its safety and anti-falling field.Firstly,the analytical calculation of the annular and the rotary permanent magnet eddy-current brake were finished for the braking force and braking moment.According to the performance parameters and braking requirements of the construction hoist and the crane,this paper proposed a method to control the permanent magnet eddy anti-fall braking with the changing of air gap.The anti-falling braking scheme of construction hoists and crane hoisting mechanisms has been designed in this paper subsequently.Secondly,the dynamic model of the hoist cage falling was established.The selection criteria of permanent magnet eddy-current anti-fall braking parameters were determined combined the dynamic model with the finite element simulation in software Comsol.According to the standard,this paper analyzed the influence of changing in the air gap,load,and other factors on the braking force during the crash of the model.Simulation results show that the designed non-contact permanent magnet eddy current anti-fall device can achieve braking effect when the hoist cage is dropped in the overloaded state.In addition,the device can meet the falling braking requirements of different cages by adjusting the air gap between the magnet group and the conductor tube.Thirdly,the dynamic model of the loaded-falling was established in the crane lifting mechanism.The selection criteria of permanent magnet eddy-current anti-fall braking parameters were determined combined the dynamic model with the finite element simulation in software Ansoft.According to the standard,this paper analyzed the influence of changing in the air gap,load,and other factors on the braking moment during the falling of the model.The simulation results show that the designed device can achieve the desired braking effect when the load falls at the rated speed and overload.Further more,the device can realize the arbitrarily adjustable braking moment by controlling the air gap between the permanent magnet array and the conductor disc.Finally,based on the design of a non-contact permanent magnet eddy current anti falling device for construction hoist,the experimental platform for the annular magnet assembly without initial velocity drop was established and the experiment has been finished.The experiment verified the accuracy and feasibility of the non-contact type permanent-magnet eddy current anti-dropping device,and the relative error between experiment results and the finite element simulation results is within 6.67%. |
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