Research On Synchronization Of Double Cylinder Lifting Hydraulic System Of Tower Crane

In recent years,with the rapid development of the economy of our country,high-rise and super high-rise buildings continue to emerge.As important construction machinery of high-rise building,tower crane is gradually developing towards large-scale and its lift method changes from single cylinder to double cylinders.The synchronization has an important impact on the safety of construction.The nonsynchronous phenomenon and manual correction problem for the double cylinders of the tower crane were analyzed in this thesis.Firstly,the working principle of the lift loop was analyzed,then,the simulation model of the double cylinder lift loop was established by using AMESim.The reason for double cylinder nonsynchronous lifting and the differenty in manual correction was investigated by fault tree and simulation method,and the accuracy of the simulation model was also verified.Secondly,the internal causes of non synchronization lifting including loop principle and divider/combine were analyzed,and the results showed that the transient accumulation error leaded to the initial error of the loop.Then the external factor,for example imblance load,was discussed,and the curves of the displacements for double cylinders were given.Based on the above analysis,considering the cost,two ways were put forward to improve the performance of the double cylinder.(1)On the basis of the original loop,the divider/combiner and the throttle valve were rematched,and the manual discharge loop was introduced.The displacements of the double cylinder were compensated simultaneously through the discharge of oil;(2)The feedback control principle was introduced to improve the open-loop control scheme in which only the divider/combiner was used to maintain the movement of double cylinder synchronously,and the automatic correction function was achieved.Finally,the simulation analysis for the two proposed schemes were carried out.The results showed that the scheme 1 could correct the displacement difference of 30mm in 3 seconds,and the scheme 2 could complete the correction at the beginning of the fall and the synchronization accuracy could also be set in a certain range according to the needs.The research results show that the imblance load and the flow divider/combiner have important influence on double cylinder synchronous precision and some design defects exists in the original double cylinder lift loop which causes the difficulty in manual correction.Both the two proposed design schemes can achieve the speed adjustment and error correction.The work in this thesis provides a certain theoretical basis for designing the hydraulic system of the self-lifting tower crane and some references for designing the loop of double cylinders of other construction machinery.