Grey Relation between Positive and Inverse Starting Friction Torque of Slewing Bearing for Wind Turbine

The rotation direction of slewing bearings in operation changes constantly to regulate the yew and blade system of a wind turbine for responding to a changeable wind field. Thus, positive (in a clockwise direction) and inverse (in an anticlockwise direction) staring friction torques must be taken into account to assess the services performance of slewing bearings. Based on the grey system theory, the grey relation between positive and inverse staring friction torques of a stewing bearing under different loads is studied to reveal the inherence attribute of staring friction torques. The experimental investigation on two types of stewing bearings shows that the grey relation between positive and inverse starting friction torques of slewing bearings is close and the two have the same attribute along with the above 83% grey confidence level, laying the foundation for evaluation of the staring friction torque of stewing bearings for wind turbines.