Automatic ultrasonic robotic array

A novel, autonomous reconfigurable ultrasonic phased array inspection robot for non-destructive evaluation (NDE) is presented. The robotic system significantly will reduce manual labor over current inspection regimes, as well as enabling inspection of inaccessible/hazardous areas such as those found in the nuclear and petrochemical industries. It will offer three quantitative benefits: improved inspection accuracy, improved safety and reduced inspection costs. The current major innovation is in embedding ultrasonic phased array technology into a small form-factor robotic vehicle, overcoming issues in ultrasonic coupling, miniaturized electronics and robot positioning. This paper presents an overview of the robot specification and system architecture along with details of a specific inspection scenario where the robot is required to inspect a saddle weld found in reheat bifurcation. This weld is formed from the intersection of two 60 mm thick steel pipes with diameters 500 and 300 mm. The robot will be capable of tracking the weld from either pipe, projecting an ultrasonic beam normal to the direction of travel. The design of a 2 MHz, 16 element embedded phased array controller is presented. A timing model of the controller details the throughput required to enable the robot to perform ultrasonic inspection while tracking the weld at 20 mm/s. The paper also considers robot positional estimation. The nature of the inspection prohibits the use of external positioning systems so the system is limited to on-board sensors, namely wheels encoders, a six axis inertial sensor and a surface feature tracking camera. The results section focuses on the characterization of inspection performance, driven in part by the ultrasonic phased array controller and robot positional estimation. A-Scans are presented to show the SNR of each array channel which was approximately 24 dB when measuring the back wall echo. It is shown that ultrasonic scan rate is limited by 802.11g wireless transmission from the robot to the host computer.