Vision-based Dynamics Monitoring(VDM)for Diagnosing the Variations of Wind Turbine Tower Foundation Conditions

A slight uneven settlement of the foundation may cause the wind turbine to shake,tilt,or even collapse,so it is increasingly necessary to realize remote condition monitoring of the foundations.At present,the wind turbine foundation monitoring system is incomplete.The current monitoring research of the tower foundation is mainly of contact measurements,using acceleration sensors and static-level sensors for monitoring multiple reference points.Such monitoring methods will face some disadvantages,such as the complexity of monitoring deployment,the cost of manpower,and the load effect on the tower structure.To solve above issues,this paper aims to investigate wind turbine tower foundation variation dynamic monitoring based on machine vision.Machine vision monitoring is a kind of noncontact measurement,which helps to realize comprehensive diagnosis of early foundation uneven settlement and loose faults.The FEA model is firstly investigated as the theoretical foundation to investigate the dynamics of the tower foundation.Second,the Gaussian-based vibration detection is adopted by tracking the tower edge points.Finally,a tower structure with distributed foundation support is tested.The modal parameters obtained from the visual measurement are compared with those from the accelerometer,proving the vision method can effectively monitor the issues with tower foundation changes.

Numerical Analysis of the Interaction between Shallow （Square, Circular and Strip） Foundations and Subsoil

In this paper, the effects of the stiffness of circular, square and strip foundation structures and bonding effects were analyzed. Presented analysis was oriented on the influence of stiffness system ＂foundation--subsoil＂ and bonds （bi-directional bond and one-directional bond with and without friction）. The results of numerical calculations have proved that the relative stiffness of system ＂foundation--subsoil＂ affect considerably the value and the distribution of contact stresses （vertical normal and shear stresses） in the foundation gap and value of the displacements （settlement, deflection and relative deformations） of foundation. From the numerical point of view, this problem was solved by deformation variant of the FEM （finite element method）. The numerically obtained results were presented in the graphical and tabular forms. Obtained results were qualitative and quantitative compared with one another. From the calculation results it is obvious that relative stiffness of the system ＂foundation structure--subsoil＂ substantially affects distribution of contact stresses in the foundation subsoil and displacements （settlement, deflection and relative deformations, flexibility） of foundation. In the case of flexible foundations, the bond on the contact surfaces must be considered during the calculation. On the other hand, the effects of friction on the contact surface between the foundation and subsoil affect the distribution of contact stresses and deformations only to smaller extent.