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The design and application of rotary encoders

Alex Ellin (Renishaw plc, Wotton‐under‐Edge, UK)
Gregor Dolsak (RLS Merlina Technika d.o.o., Ljubljana, Slovenia)

Sensor Review

ISSN: 0260-2288

Article publication date: 28 March 2008

Abstract

Purpose

The purpose of this paper is to highlight the increasing use of rotary or angle encoders and examine two distinct types of non‐contact encoders that employ novel technologies to meet the demands of very different applications.

Design/methodology/approach

Firstly, examines the design characteristics of optical angle encoders which are used for precision applications such as rotary format computer‐to‐plate pre‐press machines, machine tool A, B and C axes, and surface mount machines. Then considers magnetic encoder design, including the latest OnAxis™ technology for lower cost applications which require less precision, but are often more physically demanding.

Findings

Different rotary motion applications demand different combinations of performance and features to optimise their function – some require accuracy, others repeatability, high‐resolution or low‐cyclic error for velocity loop control, plus cost can also be a key consideration.

Practical implications

There is an increasing need to control rotary motion. An appreciation of the design principles of optical angle and rotary magnetic encoders is necessary to ensure that the correct choice of encoder is made for each application. For an angle encoder system, trade‐offs should be made to determine a realistic specification, and whilst many factors can limit achievable accuracy, techniques are available for reducing any shortfall. For applications where cost constraints and lower accuracy specifications demand a magnetic encoder, robust OnAxis™ sensor technology is gaining acceptance amongst designers, and whilst many of the basic design principles of optical encoders still apply, other specific technical aspects, such as much lower resolution and accuracy must be understood before using these devices. Hidden design costs should also be understood such as installation timings and the environmental suitability of magnets.

Originality/value

Will aid designers of rotary motion systems to make a well‐informed selection of encoder type, based on the detailed needs of their applications, including accuracy and cost budgets.

Keywords

Citation

Ellin, A. and Dolsak, G. (2008), "The design and application of rotary encoders", Sensor Review, Vol. 28 No. 2, pp. 150-158. https://doi.org/10.1108/02602280810856723

Publisher

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Emerald Group Publishing Limited

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