Compact Ultrasonic Sensors Can Succeed Where Vision Can’t

Sound as a sensing modality is used in the natural world in some well-known examples, perhaps the best known of which is bats. But it seems to be catching on in factories as well, and for some good reasons.

While photoelectric sensors have their uses and their strong points, they also have situations where they are less than ideal.

Uneven and shiny objects are tough to “see” for such sensors, which may not detect their surfaces – for example in the case of blister packaging. An automated stamping machine using a photoelectric sensor may struggle to properly sense the reflective metal surface of a panel.

There are also items with transparent or certain colour finishes that can cause troubles. The same goes when heavy soiling of a surface is involved and it’s hard to properly see past the muck.

Ultrasonic sensors use very high-frequency soundwaves to determine the position of an object, like the range-finding method a bat deploys in a cave. (This is called echolocation, and is also used by some who have lost their sight.)

This non-contact sensing method – in the case of an industrial sensor – emits sound waves and determines how long the out-and-back journey for the waves take to return. This is known as time-of-flight measurement.

Position sensors from ifm efector’s compact ultrasonic sensor range also leverage this technique (and its benefits) for object detection.

Available in M18 cube and M18 sizes, these have long ranges of up to 1.2 metres and 2.2 metres respectively and are both compact and possessing small blind zones. A vibrating sound transducer also decreases the potential interference from dirt deposits.

Potential applications are numerous for ultrasonic sensors. Objects with a high sheen, such as plastic bowls and PET bottles, are no trouble to sense. Levels of liquids and powders can be determined, as can the diameter of a roll of material being used (for re-stocking purposes).

The use of ultrasonic sensors is predicted to increase sharply in the coming years.

For example, technology intelligence firm Technavio released research earlier this year predicting sharp growth in the global market for these. The research tipped compound annual growth of more than 14 per cent a year to 2020. Drivers for this include automated factories (led by the USA) and the automobile sector, where ultrasonics are being integrated into multimodal sensing systems for self-driving cars, as well as in their parking assistance systems.

Sometimes vision isn’t the best option. For such situations – whether in smart factories or caves or a pavement – it’s necessary to hear what nobody else sees.

To find out more about IFM Efector and its products, visit their page on the Ferret website.