Open AccessEvaluation of three optical‐encoder‐based speed estimation methods for motion control.
Author(s) -
VazquezGutierrez Yeny,
O'Sullivan Dara L.,
Kavanagh Richard C.
Publication year - 2019
Publication title -
the journal of engineering
Language(s) - English
Resource type - Journals
ISSN - 2051-3305
DOI - 10.1049/joe.2018.8058
Subject(s) - tachometer , encoder , computer science , rotary encoder , oversampling , digital signal processing , computer hardware , bandwidth (computing) , telecommunications , detector , operating system
Three speed estimation methodologies: pulse count, elapsed time, and constant sample‐time digital tachometer (CSDT) methods, used with optical incremental encoders, are implemented and compared in a closed‐loop system setup using a specialised Analog Devices CM403f DSP. Dedicated hardware for quadrature encoders on the DSP facilitates the implementation of advanced speed estimation methods, such as the CSDT, by minimising the delay resulting from software intervention. The error of each methodology is evaluated theoretically and experimentally. The CSDT has limited error over all its speed range. The error of the elapsed time method increases as the speed increases. On the contrary, the relative error of the pulse count method (which is often substantial) decreases with increased speed. Several filtering techniques can be used to reduce the error of the elapsed time method; here an oversampling technique is implemented with that aim.