Jun 21, 2023

Position sensing powers smart manufacturing ...

The concept of smart manufacturing has been around for some time. Essentially, its aim is to make processes more efficient and adaptable to changing market needs. This is all achieved while maintaining high production quality, worker safety and equipment uptime. Position sensing play a key role in achieving this.

By making a manufacturing plant or process smarter, customer expectations are also met with greater swiftness. This could include the creation of more tailored, bespoke products to fit specific needs, which would otherwise be inefficient or unprofitable to manufacture. In highly competitive sectors, having a smarter, more agile mindset could be the make-or-break difference between staying ahead or falling behind the curve. But when it comes to executing smart methodologies at the production level, what technologies are available?

Position sensing is a crucial element of many smarter manufacturing processes, particularly with enabling factory automation. Tasks like pick-and-place or product assembly require the equipment to very accurately know its position in order to move precisely — information that can be obtained using position sensors. Depending on the type, these sensors may determine an object’s position either directly by finding its absolute location, or indirectly by measuring its relative displacement.

One common example is the inductive position sensor. Relying on principles of electromagnetic induction, these position sensors allow for non-contact detection of metallic objects. Conductive targets cause disturbances in the magnetic field, which are detected by the sensing element. Because only metallic objects will affect the magnetic field, inductive position sensing can’t be used to detect non-metals like plastic. But the upside of this is that the sensor is less likely to be affected by dust or dirt build-up because these won’t affect the magnetic field. This makes them ideal for operation within dirtier industrial environments.

Another type is the optical position encoder. These typically consist of an LED and photodetector, with either an optical disc or scale depending on whether the encoder is measuring linear or rotary displacement. Optical encoders can perform to high resolutions, making them ideal for applications where high precision matters, such as a CNC machine.

When photons of light are captured by the photodetector, a weak electrical signal is generated. This must be amplified using a signal-conditioning circuit before being digitised with an analogue-to-digital converter (ADC). It can then be received by a CPU or microcontroller, which is able to calculate object position based on the signal. The processing unit is capable of recognising events such as reference marks being passed and can immediately take remedial action within a closed-loop system.

It’s vital that these processes of sensing, conditioning, and digitising are up to scratch. Sensor failure or inaccuracies could lead to the incorrect manufacture of products, leading to a drop in productivity and wasted materials and time.

When an encoder is first developed, it may be comprised of off-the-shelf discrete components or integrated circuits (ICs). And for low production volumes, this may be an adequate solution. But for a sensor system that outstrips its competition, it’s preferable to opt for an Application Specific IC, or ASIC.

An ASIC is simply an IC that has been designed and manufactured with its exact application in mind. This bespoke approach to IC design results in a chip fully optimised for its role, often with reduced power consumption and smaller chip size as additional benefits to its improved performance.

Choosing ASIC design also offers IP protection to reassure sensor manufacturers that their IP will not be made available to the competition, keeping them one step ahead. The nature of custom IC development and design also makes it much harder to reverse engineer than a standard IC, offering another level of defence.

Manufacturers are increasingly looking for methods to maximise efficiency of the shop floor. And in critical applications, even the tiniest fraction of a millimetre could mean the difference between success and failure. By utilising ASIC-based technologies, it’s possible to optimise sensor systems right from chip level for a superior performance, no matter the process.

Richard Mount is Director of Sales at ASIC design and supply company Swindon Silicon Systems.

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