Servo technology is moving to a new paradigm

Servo technology is moving to a new paradigm

Published On: 4 July 2014
Servo technology is moving to a new paradigm

A long-standing engineers’ dream is to be able to assemble sophisticated, high-function, multi-axis servo systems from a kit of parts with no more difficulty than clicking Lego® bricks together. Gerard Bush of INMOCO in Daventry says reality hasn’t quite caught up with fantasy, but it is moving in the right direction.

If you look at a schematic of a servo system it uses small rectangles to depict motors, amplifiers and controllers. These are connected in a logical way by neat lines and arrows. It all looks incredibly simple and it is tempting to think that all a servo engineer has to do is unpack the various components and, using cables, plug them together in the same pattern as in the diagram.

Unfortunately, the reality is, of course, a little different.

In truth, a skilled precision motion control engineer can get a servo system ‘wired up’ fairly quickly, but then there is a period of tuning, checking and commissioning. (Plus, there may have been considerable effort put into writing the motion control programming before this.) If an engineer who is not familiar with servos tries the same thing, it will probably take at least 10 times as long to get the system up and running.

So, most OEMs and machine builders who develop servo-driven equipment such as packaging machines and pick and place stations, either employ their own motion engineers or tap into their servo supplier’s expertise.

Put simply, you need a specialist to set up a servo system. However, if you take a historical perspective you will see that the specialist now needs far less time to commission a system than was required say 20 years ago. Servos have become easier to set up and tune. They have also become more compact, more robust, more reliable and cheaper.

This is the reality of technology development; each year the manufacturers make a small improvement or two and over time these mount up, so when you compare similar products even 10 years apart, the technology gap appears to be vast.

One of the major steps forward in improving the user friendliness of servos has been integrating the various components, motor, amplifier and feedback encoder, into one single unit, such as that seen on the Pegasus range from INMOCO. While such integrated equipment has been available for some years, it is only relatively recently that users have really warmed to the concept. However, there is now a momentum for change to integrated systems and the industry may be on the cusp of a sea change in attitudes.

Pegasus combines a servo motor, digital drive and magnetic encoder to provide an integrated servo module. This configuration ensures reliable performance, accurate motion and efficient power management, the features that build a foundation for trouble-free operation in any demanding industrial application.

The Pegasus series’ products support various EtherCAT communication standards, such as FoE for firmware updates, EoE for multi-axis configuration and CoE for standard drive control connectivity via IEC 61158 Type 12, IEC61800 CiA 402 drive profile for easy systems’ building.

As integrated servo units, Pegasus does not need separate power and feedback cables and using simple EtherCAT wiring for communication makes for cost-effective equipment with fewer components and reduced installation time. The system architecture is reduced to a central controller with single cables connecting to autonomous axes, each with its own local power supply.

The Pegasus’ range consists of five sizes of motor: 40mm frame (50W/82W) and 60mm frame (100W / 200W / 300W). Each has its own amplifier or drive, a 4096ppr magnetic encoder and EtherCAT communication capabilities. Additional functions include a four-step notch filter, response control with real-time FFT, phase short dynamic braking and fixed node addresses.

Pegasus and other integrated servo systems can be used anywhere that traditional discrete part servos are deployed – that is in liquid dispensing systems, glue laying, profile cutting, 3D mapping and machining, etc. The advantages for a typical application can be quantified, as:

• 50 Percent smaller than traditional system using separate servo drive and motor

• Reduced control cabinet space requirement by up to 70 percent

• Potential reduction in cabling needs by more than 80 percent

• The ability to add drives as required without changing the control cabinet

A solution such as Pegasus is still probably best set-up and commissioned by an expert, but there are several advantages to note. First, the time spent designing and commissioning a system is reduced considerably. Secondly, reconfiguring and extending systems is easier, and quicker. Thirdly, non-expert engineers can manage to configure more complex systems than previously.

The time has not yet come when servos are off-the-shelf commodity components that can be assembled into systems by almost anyone. The truth is that such a time may never come – some servo applications will be very straightforward and the necessary equipment sufficiently simple and low cost that a confident OEM will be able to cope, but, it is in the nature of technological development that as the equipment gets easier to use, so the applications become more demanding and therefore the expert will always be needed.

Furthermore, buyers should always remember the hidden value of expert guidance – they will solve the problems you didn’t know you had and suggest further enhancements and developments, thereby helping you steadily improve your goods and services.


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