GA-Adaptive Template Matching for Offline Shape Motion Tracking Based on Edge Detection: IAS Estimation from the SURVISHNO 2019 Challenge Video for Machine Diagnostics Purposes

Alessandro Paolo Daga,Luigi Garibaldi

doi:10.3390/a13020033

Abstract

The estimation of the Instantaneous Angular Speed (IAS) has in recent years attracted a growing interest in the diagnostics of rotating machines. Measurement of the IAS can be used as a source of information of the machine condition per se, or for performing angular resampling through Computed Order Tracking, a practice which is essential to highlight the machine spectral signature in case of non-stationary operational conditions. In these regards, the SURVISHNO 2019 international conference held at INSA Lyon on 8–10 July 2019 proposed a challenge about the estimation of the instantaneous non-stationary speed of a fan from a video taken by a smartphone, a pocket, low-cost device which can nowadays be found in everyone’s pocket. This work originated by the author to produce an offline motion-tracking of the fan (actually, of the head of its locking-screw) and obtaining then a reliable estimate of the IAS. The here proposed algorithm is an update of the established Template Matching (TM) technique (i.e., in the Signal Processing community, a two-dimensional matched filter), which is here integrated into a Genetic Algorithm (GA) search. Using a template reconstructed from a simplified parametric mathematical model of the features of interest (i.e., the known geometry of the edges of the screw head), the GA can be used to adapt the template to match the search image, leading to a hybridization of template-based and feature-based approaches which allows to overcome the well-known issues of the traditional TM related to scaling and rotations of the search image with respect to the template. Furthermore, it is able to resolve the position of the center of the screw head at a resolution that goes beyond the limit of the pixel grid. By repeating the analysis frame after frame and focusing on the angular position of the screw head over time, the proposed algorithm can be used as an effective offline video-tachometer able to estimate the IAS from the video, avoiding the need for expensive high-resolution encoders or tachometers.

Highlights

Rotating machinery are fundamental components of mechanical systems for most of the industrial applications, as mechanical power is commonly obtained in the form of torque at a rotating speed.Electrical motors, internal combustion engines and motors in general, convert some sort of source energy into mechanical energy which is transferred to the final user through a mechanical transmission which provides speed and torque conversion.Algorithms 2020, 13, 33; doi:10.3390/a13020033 www.mdpi.com/journal/algorithmsThe speed is a piece of essential system information, usually kept under control to accomplish a determined work
Template Matching (TM) technique, which is here integrated into a Genetic Algorithm (GA) search
Using a template reconstructed from a simplified parametric mathematical model of the features of interest, the GA can be used to adapt the template to match the search image, leading to a hybridization of template-based and feature-based approaches which allows to overcome the well-known issues of the traditional TM related to scaling and rotations of the search image with respect to the template

Summary

Introduction

Rotating machinery are fundamental components of mechanical systems for most of the industrial applications, as mechanical power is commonly obtained in the form of torque at a rotating speed.Electrical motors, internal combustion engines and motors in general, convert some sort of source energy into mechanical energy which is transferred to the final user through a mechanical transmission (e.g., a gearbox) which provides speed and torque conversion.Algorithms 2020, 13, 33; doi:10.3390/a13020033 www.mdpi.com/journal/algorithmsThe speed is a piece of essential system information, usually kept under control to accomplish a determined work. Rotating machinery are fundamental components of mechanical systems for most of the industrial applications, as mechanical power is commonly obtained in the form of torque at a rotating speed. Electrical motors, internal combustion engines and motors in general, convert some sort of source energy into mechanical energy which is transferred to the final user through a mechanical transmission (e.g., a gearbox) which provides speed and torque conversion. The appearance of damages in the system has repercussions on the instantaneous speed, which can be used as a source of information of the machine health condition per se. The information about the instantaneous speed is fundamental for machine diagnostics in other ways. In the field of Vibration Monitoring (i.e., a successful kind of condition monitoring based on vibration records) for example, it is very common to use measured or estimated information about the Instantaneous Angular Speed (IAS) to perform the so-called Order Tracking [1]

Methods

Results

Discussion

Conclusion