Mobile robot positioning using accelerometers for pipe inspection

Abstract

In NDE, robotic inspection systems are becoming common practice in the industry to mitigate impact on health and safety as well as the efficiency of determining the health of a structure. One of the issues with robotics is to establish a precise position for an inspection measurement. For NDE this is a challenge for both defect mapping and defect monitoring. Methods for obtaining position and orientation of a robot on a pipe involve external sensors and systems, such as GPS, or relying on a known start point and encoders. External sensors are expensive, take extra time to calibrate and requires set up, while encoders have error which accumulate with time. Advances in Micro-Electrical-Mechanical Systems (MEMS) have made localizing sensors smaller and feasible to implement into mobile robotics. One cost-effective device is an Inertial Measurement Unit (IMU) which can measure acceleration with 3 degrees of freedom. One NDE area which can benefit from robotics is pipe inspection. An algorithm has been developed which calculates the clock face angle (ω) and orientation angle (α) using only the gravity vector. This approach offers a quick method of obtaining accurate position and orientation information using an internal sensor, which has applications not only for robotics, but also for manual scanners.