Deployment of ultrasonic through-transmission inspection using twin cooperative industrial robots

Riise, Jonathan and Pierce, S. Gareth and Nicholson, P. Ian and Cooper, Ian and Wright, Ben; (2016) Deployment of ultrasonic through-transmission inspection using twin cooperative industrial robots. In: 55th Annual British Conference of Non-Destructive Testing. British Institute of Non-Destructive Testing, Nottingham, pp. 1-13. (In Press)

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The uptake of composite materials in the aerospace sector has led to a number of automated inspections systems based on industrial robots to be developed, including the IntACom project at TWI Technology Centre Wales. These new materials present challenges not only due to their intrinsic material properties but also due to the higher complexity of their surface geometries. Robotic inspections are designed using Off-Line Programing (OLP) software to describe a path on a computer-aided design (CAD) model of the object to be inspected using the pulse-echo ultrasonic method. By synchronising the movements of two robots, a second robot can be used to follow the path of the first, allowing for ultrasonic through-transmission inspections. Investigations carried out at TWI Technology Centre Wales have identified key challenges encountered in alignment and synchronisation when carrying out through-transmission inspections of various components. Reasons behind these challenges include inherent latency in the communication between the two robots and tool misalignment. Another challenge typically encountered arises from the relative pose between probes remaining fixed which makes it difficult to inspect geometries with varying thicknesses. The current paper discusses the above mentioned challenges and presents on-going work at TWI to tackle these issues. The effects of misalignment on the received ultrasonic signal are discussed and experimentally verified. The robot velocity and acceleration profiles are also taken into account for geometries with high curvature and their effects on through-transmission inspections are discussed. Finally an inspection of a component with varying thickness is presented and the results are compared for different robot cooperation methods.