Determining Position and Orientation of a 3-Wheel Robot on a Pipe Using an Accelerometer

Abstract

Accurate positioning of robots on pipes is a challenge in automated industrial inspection. It is typically achieved using expensive and cumbersome external measurement equipment. This paper presents an Inverse Model method for determining the orientation angle $(\alpha $ ) and circumferential position angle $(\omega $ ) of a 3 point of contact robot on a pipe where measurements are taken from a 3-axis accelerometer sensor. The advantage of this system is that it provides absolute positional measurements using only a robot mounted sensor. Two methods are presented which follow an analytical approximation to correct the estimated values. First, a correction factor found though a parametric study between the robot geometry and a given pipe radius, followed by an optimization solution which calculates the desired angles based on the system configuration, robot geometry and the output of a 3-axis accelerometer. The method is experimentally validated using photogrammetry measurements from a Vicon T160 positioning system to record the position of a three point of contact test rig in relation to a test pipe in a global reference frame. An accelerometer is attached to the 3 point of contact test rig which is placed at different orientation $(\alpha $ ) and circumferential position $(\omega $ ) angles. This work uses a new method of processing data from an accelerometer sensor to obtain the $\alpha $ and $\omega $ angles. The experimental results show a maximum error of 3.40° in $\alpha $ and 4.17° in $\omega $ , where the $\omega $ circumferential positional error corresponds to ±18mm for the test pipe radius of 253mm.