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FEATURE MOTION CONTROL
developing a new breed of encoders
The industrial sector is about to experience a step change in
what can be achieved with regard to the resolutions that magnetic encoders will support. Through designing graphene-based sensors into their designs, encoder manufacturers will gain advantages
that will not only be of value to them, but can also be passed on to the OEMs they serve, as Paragraf explains
F
rom machine tools and avionics, to power generation and industrial drive systems, sub-micron levels of precision are now being called for. As such, the performance expectations from encoders are dramatically increasing.
This, however, means that the shortfalls of conventional encoder set-ups are becoming more apparent, and a different approach must be taken to allow positioning and linear/rotational movement to be accurately tracked. Analyst firm Research & Markets estimates that the worldwide
encoder market will go from an annual revenue of $2.3 billion in 2021 to $3.7 billion by 2026. To keep ahead of their rivals, encoder manufacturers
must find ways to differentiate their products and gain a competitive edge – either through raising performance benchmarks or reducing the total cost of ownership (TCO) associated with their solutions. Top of any encoder manufacturer’s wish list will be the ability to increase
the resolution of their devices, as the feature sizes that tools need to deal with get smaller and positioning of equipment need to support tighter incremental changes. Such increases in resolution must be attained without the overall bill of materials (BoM) costs being pushed upwards. Likewise, these resolution improvements cannot add to the size of the encoder solution, as this will cause major problems when it comes to integration. Furthermore, engineering effort must also be kept to a minimum.
encoder mechanisms The majority of encoders will either rely on optical or magnetic arrangements. While optical encoders are commonly used, they are not that robust, so are not generally suitable for deployment in challenging industrial environments as the encoder disks can be damaged through shocks or vibrations. As they rely on line of sight technology, any contaminants that cover the encoder disks will have a detrimental effect on their operation. Magnetic encoders are heavier duty solutions, which are better
aligned with industrial applications. Although these offer a longer term operational lifespan and avoid issues like the presence of contaminants impacting on their ability to function, the resolutions they can achieve are significantly lower. This makes them impractical in the high accuracy systems that equipment OEMs are now looking to design. OEMs therefore want a new kind of solution that combines the high
resolution capabilities of an optical encoder with the assured robustness of a magnetic one. Until now, these attributes have basically been exclusive of one another. But, innovations with regard to magnetic sensors are about to disrupt the encoder industry.
graphene-based magnetic sensors By incorporating graphene sensor elements into magnetic sensors, rather than conventional silicon ones, it is possible to deliver a number of benefits to enhance encoder performance. These are due to the properties that graphene possesses, namely: • Graphene is an incredibly strong material (200x stronger than steel). This means that it is highly suited to industrial deployment, exhibiting exceptional resilience to shocks, vibrations, etc.
• It is highly sensitive. So even slight changes in a magnetic field can be registered.
• As graphene consists of a single layer of carbon atoms which has a thickness of just 0.34nm, it is two-dimensional (2D). Consequently, graphene sensor elements are not subject to the ‘Planar Hall Effect’, like conventional magnetic sensors will be (where interference from stray magnetic fields will lessen their accuracy). Though all this sounds promising, the issue has been how to
successfully fabricate high-grade graphene so that high volume markets can be supplied – as the processes being used were only applicable for
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