Time is critical

Written by: Tom Shelley | Published:

Delegates at Eureka’s ‘Automation for the Future’ Design Day heard how a huge animatronic figure was created in eight weeks – and how a full electric drive system could be sized in three minutes



Time is money: if there’s one message that came out of Eureka’s ‘Automation for the Future’ Design Day, this was it. Among the presentations hammering this message home were: the creation of an animatronic figure in eight weeks; how distributed control and absolute encoders can save time and money; and special software that can speed the process of sizing an electric drive system.
The day started with Jamie Campbell – of special effects company Artem – describing how the company created an 8m-high animatronic figure in just eight weeks.
“The tough deadline informed most, if not all, of our decisions,” he told delegates.
The figure, a replica of an American football player, was dubbed ‘Big JT’. It had to be ready in time for a series of publicity dates across Southeast England. There could be no slipping of the deadline.
After each performance – in which Big JT walked, waved his arms, moved his head and winked at the audience – the figure had to be dismantled and transferred to the next destination.
For Artem, everything revolved around the short lead time: in one instance, it wanted to use a certain set of linear actuators from SKF – but these could not be delivered in time. Instead, Artem chose a smaller type, but ‘doubled them up’ in the design in order to deliver the necessary motion.
Within the time constraints, the key automation challenges were the feet and the head. The head was controlled by a six-axis motion base, with six linear actuators. Each has a linear feedback pot – so effectively becomes a servo. Motion bases are common in animatronics, but are complex and difficult to design. Artem’s answer was to re-use a motion base from a previous project.
“This alone saved us a week,” said Campbell.
Big JT’s realistic walking motion was recreated by driving the feet along a linear guide rail using linear actuators. At the same time, the whole figure was moved forward by a JCB. The speed of the feet had to be controlled carefully if Big JT was to avoid ‘moonwalking’ – so a set of encoders in the JCB helped to determine the speed of the walk cycle.

Motion expertise
Later presentations were more practical in nature: Gary Cork, of Control Techniques, explained some of the advantages of distributed control – in which intelligence is located in the drive rather than centrally on a PLC (see box).
“Centralised control ruled years ago because intelligence within drives was not there,” he said.
Now, many applications can benefit from this distributed arrangement. He cited the example of Northumbria Water, which has overcome ‘ragging’ – the fouling of sewage pump impellers – by fitting two 160kW drives. Each drive controls a pump, and can carry out a series of cleaning cycles automatically – meaning there is far less manual intervention.
Hybrid systems – combining the benefits of both centralised and distributed intelligence – are also possible, but more likely to cost more for smaller systems.
Similarly, Ludwig Schmidt of Heidenhain explained how absolute encoders – which need no reference point and can instantly tell where they are – may begin to find wider use within automation. The devices are usually used within critical applications – such as on automotive production lines – which must instantly know where they are in the event of a power failure.
But the company says that the price of absolute encoders is now so close to that of incremental encoders that they can be justified in more general applications.
“Using an incremental encoder, you may need to move all the way along the line and back again to find a reference mark,” said Schmidt. “Lots of moving means lots of time – and energy.”
John Morse, senior researcher at IMS, also touched on time saving in his presentation on the growing importance on industrial Ethernet – a range of communications architectures that allow automation devices to talk to one another. The whole idea behind industrial Ethernet was to create a system that was deterministic – setting a maximum time that it would take information to be sent – so a key advantage of the system is the ability to speed up automation.
There are many variations or ‘flavours’, and several – such as EtherCAT – are optimised for high-speed communications.
Despite the growing popularity of industrial Ethernet – with many automation devices now being ‘Ethernet enabled’ – there is still a fair degree of confusion over the individual Ethernet ‘flavours’ and how precisely they are used.
“In a recent survey, we found that the biggest barrier to Ethernet adoption was the lack of trained people,” said Morse.
Nigel Dawson of Festo looked into the past, and to the future – with a rundown of the way that automation within handling has changed.
“The problem with manufacturing today is the increased need for flexibility,” he said. “We need to supply equipment to take account of that.”
In some cases, this quest for speed has led to a full-circle return to semi-automated – and sometimes manual – assembly.
“Many of our customers are now assembling their products manually,” he said. “Because of shorter product lifetimes, they cannot invest in facilities to make products that may only last for six months.”

Hands-on advice
Workshops form the heart of Eureka’s Design Days – and this year’s workshop leaders did not disappoint. They took delegates through their paces in encoders, drives and system design.
Festo’s Nigel Dawson showed design engineers how they could size up an electric drive system in just three minutes – with help from the company’s Positioning Drives software.
An initial screen asks for a few basic system parameters, including the load on the drive, stroke length, repetition accuracy – and whether the system is horizontal or vertical (angles motion is also possible). This then calculates a combination of Festo components that will provide a solution.
No ‘correction factors’ are necessary, but Dawson suggested overestimating the load – as systems are often overloaded in practice.
A full version of the software – which is free – can be downloaded from Festo’s website. Visit the Design Days website (www.designdays.co.uk) for details of the link.
Control Techniques also ran a software-based workshop – in this case, encouraging delegates to program a motion exercise using its Digitax indexer. A simple interface allowed a motor to be moved in quite complex fashion – using a flowchart-style.
The project involved a homing step, and two move absolute steps – sandwiched between a series of delays. The whole process took around 20 minutes and was done by clicking on a series of icons and typing in specific delay periods.
Other operations – such as creating new program flows, setting outputs while a block is running, or setting limit switches – could also be achieved in a straightforward way.
Heidenhain concentrated on the potential applications of absolute encoders: Stuart Jenkins highlighted the importance of getting an instant, exact fix on position.
“Imagine a robot is welding the seams of a car,” he said. “If it had to do a referencing return it would rip the roof off.”
Many other applications are more practial in their use of absolute encoders: for radiotherapy, the patient is positioned very accurately on a bed – while the radiation equipment must also be precisely targeted.
“You don’t want to be rotating the machinery every morning,” says Jenkins.
Other potential absolute applications include: machine tools; a winch for stage scenery (which needs accuracy to 1mm); and a digital printing press.


Pros and cons of distributed control

Pros
* Low cost
* Opportunity for faster response times
* No machine controller
* System is scalable

Cons
* Needs high level programming and commissioning tools
* High system communication bandwidth may be needed
* Usually multi-processing, but not multi-tasking


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