Forty years ago, simple optical sensors were as big as milk bottles; now we can get much better performance out of a device the size of your little fingernail.  Then, intelligent machines were seen as science fiction villains; now in-built Sensor Intelligence is the ‘good guy’ that enables high-speed, flexible, traceable and safe automation.

Real-time control

From simple presence, proximity and distance devices to the in-built intelligence of Optical Character Verification and Recognition systems, and 3D machine vision, the ability to communicate digitally has enabled real-time control. 

Sensors are becoming much easier to programme, install, commission and ‘teach’, meaning complex sensing operations in automated production, processing and packaging environments can be supervised without expert programming knowledge. 

As well as the sensors to generate the data, the parallel development of the computing hardware, software and Ethernets provide the infrastructure, while common protocols and open source communications have delivered high-speed data highways.  

Adding IO-Link interface to standard sensors has revolutionised two-way communications in factory control systems and the ASIC chip has delivered powerful processing power in miniature.  So, with the ability to pack more technology into ever-more miniature devices comes a new opportunity to build even more advanced automation capability into the sensors themselves.

Making sensors smart

Product innovators at SICK AG’s Waldkirch headquarters in Germany make sensors ‘Smart’ by moving intelligent functions from the PLC to the sensors themselves. They believe they are providing a glimpse of the factory of the future.

A range of advanced function blocks have been built into sensors of all types to provide a powerful new set of tools for the engineer. With these functions, logical loops are moved away from the PLC to the sensor.  Real time events can be locally processed, without waiting for the raw data to be uploaded to the central PLC program, processed and information extracted before action.

With this reduction in computing load at the PLC, management of fast processes is speeded up and data processing capability limitations reduced, so enhancing process speeds with higher productivity and efficiency. 

Smart examples

Embedding a high-speed counting function into a Smart Sensor enables high-performance monitoring and measurement of machine speeds, leading to accurate detection and counting. So, for example, an optical sensor can detect and count products on a production line and transfer the results to the control system.

A Smart Sensor can use Time-Based Position Measurement to calculate product length, or distance between objects on a high speed conveyor, to ensure they are the right size or in precisely the right position, for example for picking or dimensions measurements of packages. 

With the ability to Suppress False Signals (debouncing) from an anomalous triggering event in difficult environments such as sawdust and spray or with product protrusions, Smart Sensors can make real time decisions which reduce central computing load and network signal delays and errors. Product Profile Recognition and timing functions can also be combined to provide Product Verification capability to ensure products are of the right shape or in the correct position for tasks such as picking, sorting or have right packaging. 

Even Time Tracking can be incorporated due to the accuracy of in-sensor time evaluation which assigns a time value that can accurately locate a product further along the product line despite signal delays in network communication with the central processor. Also Precise Real Time Location provides rapid, localised distance sensing to measure product lengths and spacing. 

To benefit from smart sensing an IO-Link compatible with a wide range of fieldbus protocols is essential and this enhanced capability is being built in by sensor manufacturers, with major PLC manufacturers also adding more functionality, as are a number of third-party suppliers.