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Advanced Engineering 2021

NEC Birmingham(B40 1NT)

03/11/2021 - 04/11/2021

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Getting more from drive technology

Getting more from drive technology

More and more machine builders are finding that the features and functions built into modern variable speed drives, servos, linear motor controllers and delta robot drives are giving them opportunities to redefine machine performance and add even greater value to their designs. Robert Brooks of Omron explains how.

Drive technology has long been at the heart of virtually every machine design, with inverters driving the motors that quite literally turn the wheels of industry. Increasingly, machine builders are finding the simplicity and ease of integration of modern servo drives is raising the bar on machine sophistication, while linear motor drives are enabling whole new levels of performance to be realised. But how much more could machine builders be getting from drive technology, and what are the specification decisions that will elevate a particular machine design from good to great?

When we consider variable speed drives, it's tempting to think that we know all there is to know about the technology. Of course there are ongoing improvements in inverter control algorithms, leading to improved motor performance, but increasingly the innovative additional functions being incorporated even into base model products can make a huge difference to a machine design. Consider safety, for example. Functions such as Safe Torque Off (STO), defined under EN 60204-1, have become an established feature of inverter and servo drives, enabling machine builders to implement 'drive integrated safety' strategies which simplify control panel installation complexity. Other functions, including Safe Stop 1 and Safe Limited Speed are gradually finding their way into more drives, enabling machine builders to significantly reduce the complexity of machinery safety circuits when compared to traditional systems. Reduced complexity equates to reduced cost, time and effort - all of which impact on the bottom line.

We can look at the impact of diagnostics information as well. This is a crucial consideration for machine builders who are not only trying to add competitive advantage by providing end users with designs which enable them to maximise uptime and availability, but who are also looking build additional services into their wider machine offering.

The diagnostics capabilities built into modern drives products can help. Where once those capabilities were limited to simply flagging up a fault, today a drive can pro-actively send detailed fault reports via the machine controller to the operator, maintenance engineer or even machine builder, and ensure any faults can be rectified - easily and, increasingly, remotely. Drives can also help with predictive maintenance, by monitoring parameters such as the torque on a given axis or the current draw of a motor in real time. As actual values begin to drift from the nominal, the development of an impending fault can be flagged up to the maintenance team, who can take pre-emptive action or schedule a repair at a convenient time.

Condition based monitoring

Some drives can also monitor the condition of their own internal systems to provide an estimate of remaining service life. This again is of great help for machine builders looking to build cost-effective maintenance contracts into their service offerings. Drives vendors continually strive to produce more and more reliable products, for example a drive that has a design lifetime of ten years service life. This in turn provides a good deal of confidence to the machine builder that service costs will be kept low.

A lot of the potential benefits to be gained from the remote monitoring and remote maintenance capability available from drives depends on network connectivity, and choice of network is another key consideration in drive specification. Fieldbus capability provides a means for a controller to access relevant drive information, but it also has a vital impact on ease of integration, reducing the cost of cabling, improving reliability and increasing machine up-time. Deciding whether to adopt a Fieldbus such as DeviceNet, Profibus or Modbus, or a dedicated motion network such as Powerlink, Sercos or EtherCAT is no trivial task, and should be carefully considered as early as possible in the machine design stage.

Machine Builders must consider what specific functions and capabilities they need, how they want the drives to integrate with the rest of the machine, and the requirements from the end-user to integrate with other machines and the wider enterprise system. On the subject of networking, machine builders can also look at the merits of centralised or decentralised control strategies in any given application. If the machine is highly modular, that might for example steer you towards a decentralised approach. Taking the decentralised argument a step forward, many drives are now available with really quite high levels of on-board control intelligence, offering powerful processing and enough additional I/O that often a separate PLC can be eliminated from the equation. This saves cost, saves panel space, and opens up new opportunities for distributed modularity.

What about modern servo drives? Many past reports have highlighted how servos not only significantly boost machine performance, but can also reduce cost and complexity. Replacing mechanical systems with servo control based solutions has been proven many times to reduce the number of physical machine parts, to ensure the machine is more flexible in terms of multiple product changeovers, and to deliver a machine that is easier to maintain.

Servo technology can today be regarded as plug and play - simple to integrate and program. Increasingly today, the same can be said of linear servo technology, where a single drive such as the Accurax G5 from Omron can handle rotary servo, linear servo, delta robots and even third party motors in a single platform. True linear motors are increasingly being considered with respect to being able to deliver real performance benefits on modern machines, bringing a combination of accuracy and speeds that are beyond the capabilities of traditional mechanical systems.

For machine builders looking to realise the emerging benefits of modern drive technology, choice of vendor is another key consideration. Do you opt for a drives-only specialist, or a vendor who can provide a single source of all control technologies? Taking into account scalability and modularity of different machine building projects, will your chosen vendor be able to supply a single platform of drives in all the powers you require? Will that drives platform meet other anticipated future needs? Given the cost of control panel real estate, even the size of drives from different vendors is a consideration.

So there is much more to drive specification than meets the eye, but for machine builders who are looking to innovate and add value, there are significant benefits to be gained.
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