Autonomous Infrared (IR) Thermography based inspection of glass reinforced plastic (GRP) wind turbine blades (WTBs)

In this paper, the development of an autonomous, novel and lightweight multi-axis scanning system, deploying insitu Infra Red Thermography (IRT) based Non Destructive Testing (NDT), on glass reinforced plastic (GRP) wind turbine blades (WTBs), is presented. The scanner incorporates an intrinsic multi-degree-of-freedom (DOF) end-effector able to comply and achieve successful adjustment on the complex contours of a WTB, automatically aligning at the same time, the IRT equipment in proper position for inspection. The scanning system has been developed to mimic the dexterity and Non-Destructive inspection operations performed by an expert human operator. For this reason the passive adjustment of the end-effector module has been achieved via the utilisation of a half Stewart platform. Simultaneous motion of a mechanically decoupled IRT equipment carrier is realised, that exhibits two degrees of freedom, enabling accurate self positioning, laterally to the target inspection area of the WTB and automatic retraction to home position upon system withdrawal from the inspection site. The overall philosophy inherent in the system's design and development is the maximisation of the blade area coverage in a single run, at a known sensitivity, with the utilisation of the minimum number of system degrees of freedom (DOFs) and the maximum repeatability as well as positional accuracy possible. The entire system, scanning modules and end-effector, are uniquely adapted to operate in remote locations, i.e. the 100m blades utilised in offshore wind farms, as well as in the factory environment when used in a quality assurance capacity.