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`World`s fastest` servo system can be set up in under two hours

10 July, 2007

Yaskawa has unveiled a new generation of servo drives which, it claims, have the fastest response of any servo system on the market, as well as offering a positioning accuracy of 10nm. A new auto-tuning algorithm is said to allow perfect set-ups to be achieved in less than two hours, compared to eight hours or longer for some rival products.

The Sigma-V system, which was previewed at the Hannover Fair in April, is Yaskawa’s first all-new high-performance system to be launched in Europe since its Sigma-II family a decade ago. (The Sigma-III was not released in Europe, and there was no Sigma-IV because the Sigma-5 is so advanced that it has "skipped a generation".) The new servo system will be sold in Europe via Yaskawa’s joint venture with Omron.

Yaskawa hopes that the new servo family will help it to expand its share of the global motion market which, it reckons, currently stands at around 19%. According to Toshihiro Sawa, general manager of the company’s motion control division, Yaskawa is aiming to raise this share by 1% per year. "We think that Sigma-5 should be a big driving force towards this goal," he says.

Yaskawa Sigma-V servo

As well as servo amplifiers (shown above), the system includes new ranges of rotary, direct-drive and linear motors. The rotary motors, initially covering ratings from 0.1–15kW, have 30% fewer components, weigh 20% less, and are 30% shorter than previous models. They have new stator and winding designs, allowing smaller machines to be used in many applications, and cutting energy consumption by up to 30%.

Yaskawa has also developed a 20-bit incremental serial encoder for the new family which provides more than a million information points per revolution. There is also a new coupling to link the encoder to the motor that doubles its vibration resistance (to 5G) compared to previous versions. The encoder has a five-year battery life – claimed to be twice as long as its rivals.

Yaskawa has developed a dedicated servo chip for the Sigma-5 amplifiers, which have a 1.6kHz speed loop bandwidth – claimed to be the world’s fastest. Cogging torque and torque ripple have been halved compared to the previous generation, and the settling time is less than 4ms, compared to around 50ms for some rival systems.

The amplifiers have a built-in safe stop function (Cat 3, EN 954-1), avoiding the need for external contactors. Safe stop Cats 1 and 2, as well as safely limited speed, can be added using one of three option card slots.

As standard, the amplifiers provide support for analogue/pulse communications and for the 10Mb/s Mechatrolink II networking system. Support for other networks, including CANopen, Profibus DP, DeviceNet and the 100Mb/s Mechatrolink III, can be added using the second option card slot. Further communications options are planned for the Sigma-5, including Profinet, Ethernet I/P, Ethernet Powerlink, and CAN or Sercos over EtherCat.

"It will be able to talk to every machine controller or PLC on the market, predicts Michael Wiechert, Yaskawa’s general manager for motion and control in Europe.

The third option card slot will provide support for third-party encoders.

An advanced auto-tuning function helps to set up applications rapidly, and to tune seven interacting parameters simultaneously. For most applications, the system will not need any manual adjustment and can be set up by non-experts.

Wiechert reports that one of Yaskawa’s customers compared the time taken to set up a two-axis machine using the Sigma-5 and three rival products. Two of the other servo drives took two days to commission, the third took one day, while the Sigma-5 took just two hours.

The effects of a motor load can be simulated in the servo amplifier using a mathematical model that is part of the new control algorithm. This allows the complete motion control system to be tested before connecting the motor. "The electrical engineers don’t have to wait for the mechanical engineers to finish the machine," Wiechert points out.

Five different algorithms are incorporated to counter different forms of vibration at frequencies from 50Hz to 5kHz and above. This results in quieter, more reliable operation, with improved productivity, according to Yaskawa.

Other characteristics of the Sigma-5 include:
º an operating temperature range of 0-55°C without de-rating;
º  the ability to handle 350% torque overloads for 3–5s;
º  a processor that is three times faster than its predecessor;
º  an increase in surface cutting accuracy in machining applications to 1 micron, compared to 2 microns for the Sigma-III; and
º  a maximum amplifier width of 40mm, compared to 45mm for the previous generation.

The servo amplifiers are being produced in six 200V AC single-phase models from 50W-1.5kW, and ten 400V AC three-phase versions from 500W–15kW. There are plans to extend to the range up to 55kW.

Yaskawa Sigma-V servo motors

The matching range of rotary servo motors (above) includes 42 models in two inertia ratings, as well as flat-shaped models. The direct-drive motors span ratings from 3-200Nm in 17 sizes. There is also a choice of 31 sizes of linear motor, in three families: nine 200V AC ironless motors with force ratings from 40-1,080N; 15 iron-core models from 86-5,400N for 200/400V AC operation; and eight 400V AC models from 600-7,500N.

The new servo drives will have similar prices to their predecessors. Initially, they are being manufactured in Japan. Additional production will start at Yaskawa’s Scottish plant next year.

Yaskawa produced 700,000 servo drives last year and it claims to have an installed base of six million AC servo drives.




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