Permutation entropy based real-time chatter detection using audio signal in turning process

Machine tool chatter is an unfavorable phenomenon during metal cutting, which results in heavy vibration of cutting tool. With increase in depth of cut, the cutting regime changes from chatter-free cutting to one with chatter. In this paper, we propose the use of permutation entropy (PE), a conceptually simple and computationally fast measurement to detect the onset of chatter from the time series using sound signal recorded with a unidirectional microphone. PE can efficiently distinguish the regular and complex nature of any signal and extract information about the dynamics of the process by indicating sudden change in its value. Under situations where the data sets are huge and there is no time for preprocessing and fine-tuning, PE can effectively detect dynamical changes of the system. This makes PE an ideal choice for online detection of chatter, which is not possible with other conventional nonlinear methods. In the present study, the variation of PE under two cutting conditions is analyzed. Abrupt variation in the value of PE with increase in depth of cut indicates the onset of chatter vibrations. The results are verified using frequency spectra of the signals and the nonlinear measure, normalized coarse-grained information rate (NCIR).

Recurrence Quantification Analysis of System Signals for Detecting Tool and Chatter in Turning

In this thesis, the applications of the recurrence quantification analysis in metal cutting operation in a lathe, with specific objective to detect tool wear and chatter, are presented.This study is based on the discovery that process dynamics in a lathe is low dimensional chaotic. It implies that the machine dynamics is controllable using principles of chaos theory. This understanding is to revolutionize the feature extraction methodologies used in condition monitoring systems as conventional linear methods or models are incapable of capturing the critical and strange behaviors associated with the metal cutting process.As sensor based approaches provide an automated and cost effective way to monitor and control, an efficient feature extraction methodology based on nonlinear time series analysis is much more demanding. The task here is more complex when the information has to be deduced solely from sensor signals since traditional methods do not address the issue of how to treat noise present in real-world processes and its non-stationarity. In an effort to get over these two issues to the maximum possible, this thesis adopts the recurrence quantification analysis methodology in the study since this feature extraction technique is found to be robust against noise and stationarity in the signals.The work consists of two different sets of experiments in a lathe; set-I and set-2. The experiment, set-I, study the influence of tool wear on the RQA variables whereas the set-2 is carried out to identify the sensitive RQA variables to machine tool chatter followed by its validation in actual cutting. To obtain the bounds of the spectrum of the significant RQA variable values, in set-i, a fresh tool and a worn tool are used for cutting. The first part of the set-2 experiments uses a stepped shaft in order to create chatter at a known location. And the second part uses a conical section having a uniform taper along the axis for creating chatter to onset at some distance from the smaller end by gradually increasing the depth of cut while keeping the spindle speed and feed rate constant.The study concludes by revealing the dependence of certain RQA variables; percent determinism, percent recurrence and entropy, to tool wear and chatter unambiguously. The performances of the results establish this methodology to be viable for detection of tool wear and chatter in metal cutting operation in a lathe. The key reason is that the dynamics of the system under study have been nonlinear and the recurrence quantification analysis can characterize them adequately.This work establishes that principles and practice of machining can be considerably benefited and advanced from using nonlinear dynamics and chaos theory.

Creating Questions Using Turning Point

This 7-minute video describes the range of question types and shows you how to create and test them.

Using Turning Point to create zapper questions that assess confidence levels in the answers given

This 5-minute video describes how you can assess how confident your students were with their answer choices so you can adapt your teaching appropriately.

Using the Turning Point Showbar during zapper quizzes

This 7-minute video describes how Turning Point's Showbar can be used to manage questions during a presentation and includes useful techniques such as peer instruction and data slicing.

Using Turning Point to Analyse Data from a Zapper Session

This short video shows how you can save the date at the end of a Turning Point quiz, then view that data as an Excel spreadsheet.

Using the Turning Point Participant Monitor During Zapper Quizzes

This 4-minute video describes how to use the Turning Point Participant Monitor to review the performance of the whole group and individual students during a lecture.

Turning Point zapper test of moment by moment voting

This short 3 min video shows how Camtasia Studio can be used to record the audio of a lecture alongside the moment-by-moment votes recorded using Turning Point.

Turning Point (zappers) quick guide (Windows 7)

This single page PowerPoint can be printed out and provides brief instructions on how to use zappers ina Windows 7 teaching space.

Using Participant Lists with Turning Point Zappers

This 11-minute video shows you how to create a participant list that will enable you to record the scores of individual students as they answer a series of questions in a Tuning Point presentation. It shows you how those students can register their handsets in-class, so that you can distribute the handsets quickly at the start of the session.

Fixing Issues with Turning Point (Zapper) Presentations

This video offers advice about problems that might be encountered when running a presentation that was developed in Turning Point 4.0 on a computer with version 4.2 installed. NOTE: With the upgrade to version 4.3, Turning Point now automatically fixes these issues when you load an older presentation. Hurrah!

Using a PresenterCard with Turning Point zappers

This 2-minute video shows you how to pair a PresenterCard so you can remotely control your presentation.

How to use Turning Point in a Common Learning Space

This is a quick guide based on screenshots which shows you how get started with Turning Point 5 and Office 2013 in Common Learning Spaces.

Quick printed guide to zappers (Turning Point 5)

One side of A4 which provides step-by-step instructions to help you use Tunring Point 5 in Common Learning Spaces. Includes advice about dealing with technical glitches.

Turning Point ResponseWare student guide

The brief guide tells you how to use your smart phone, tablet or laptop to vote in a Turning Point quiz. (Updated for October 2014)