Study on Dynamic Monitoring of Wire Rope Tension and Load of Multi-rope Friction Hoist
Author:Lei Gao Yang
Supervisor:xu gui yun
The lifting load can be expressed by the sum of each wire rope tension in the research of multi-rope friction hoist.When the wire rope tension difference,the lifting load,or the maximum load difference is excessive,the creep,slip and break of wire rope will be caused which seriously affects the safe operation of the lifting system.The tension measurement methods based on wire rope tension hydraulic balancing device mainly include oil pressure sensor method and tension-compression conversion method.For the oil pressure sensor method,the measured tension is not accurate because of the tubing characteristics and the non-linear friction between the piston and the hydraulic cylinder wall.For the tension-compression conversion method,the tension signals measured by ordinary pressure sensor fluctuate greatly due to wire rope vibration and load impact.Therefore,the effective tension signals can not be measured and the actual lifting load can not be characterized by ordinary pressure sensor.In order to achieve accurate measurement,this paper carries out in-depth research from the following four aspects:(1)The dynamic model of longitudinal vibration of the wire rope is established.The longitudinal vibration of the wire rope not only has a great influence on the dynamic characteristics of the hydraulic balancing device,but also affects the tension measurement by the tension-compression conversion method.In this paper,the transverse vibration and torsion of wire rope are neglected,and the dynamic tension model is established and solved by the Hamilton principle and central difference discrete method.Then,the dynamic tension curve of the wire rope is obtained by simulation with the actual parameters in the field.The whole lifting system is modeled and simulated by AMESim software.Then,the dynamic characteristics of hydraulic balancing device which include pressure,flow rate and piston rod displacement are analyzed with the changing load.In order to realize the accurate measurement of wire rope tension by oil pressure sensor,the formulas of along-way pressure,local pressure,and the friction model are adopted to compensate the wire rope tension.In addition,the scheme and platform of dynamic monitoring of wire rope tension are designed and built,respectively.The source information sensing system is constructed,which includes the construction of hardware and software sensing system.Then,the real-time dynamic monitoring of wire rope tension and load is realized.(2)A particle damping sensor with vibration reduction and filtering function is developed.The structure of the particle damping sensor is designed according to the characteristics of the wire rope tension hydraulic balancing device,and the spoke elastomer structure is adopted.The simplified force models between particles,between particles and cylindrical wall are established to study the force and work based on Hertz contact theory.The normal,tangential and rolling visco-elastic contact models between particles based on discrete element method are analyzed,which is useful to understand the main factors affecting the particle damping effect and the energy dissipation principle of particle system.(3)The optimization of the elastomer structure and particle parameters of the particle damping sensor are studied.The static and modal analysis of the spoke elastomer are researched by ANSYS to obtain the axial sensitivity and natural frequency.Then,the optimum structural parameters of the elastomer are obtained by orthogonal test and limit difference method.Meanwhile,the simulation software EDEM based on discrete element method is used to simulate the damping effect parameters which include the normal force,tangential force and kinetic energy between particles by changing the material,diameter of particles,the mixing mode of particles with different materials and diameters.Then,the optimal material and diameter of particles are determined to achieve the best particle damping effect,and the accurate measurement of tension by tension-compression conversion method is realized.(4)According to the optimum elastomer structural and particle parameters,the particle damping sensor is designed and manufactured,and the linear calibration is carried out.The field test results of ordinary pressure sensor and particle damping sensor are compared and analyzed to verify that the particle damping sensor has better effect of vibration reduction and filtering.In order to reduce the interference of noise generated by external environment during the process of signal transmission and achieve more accurate measurement,the arithmetic average filtering method is used to realize the real-time digital signal filtering.Meanwhile,as to study the hoist fault diagnosis based on wire rope tension signal,a digital filtering algorithm based on wavelet frame threshold is adopted to process the tension signals.In addition,when the piston rod of hydraulic balancing device extends or shrinks to the limit,the influence on wire rope tension measurement is deeply analyzed.In this paper,the dynamic and accurate monitoring of wire rope tension andload of friction hoist is realized,which provides a basis for fault warning based on wire rope tension,and effectively guarantees the safe operation of the hoist.The dissertation has 94 figures,8 tables,160 references.