Technology news: January 2002
32-axis network `overcomes multi-axis limitations`
The US motion control specialist Aerotech has developed what it describes as "the world`s first 32-axis motion, vision and I/O network". The system, called Automation 3200, includes a high-performance motion engine, digital drives, software-based PLCs, MMI software, and a vision control module.
Aerotech claims that the system addresses a major shortcoming of today`s multi-axis controllers - as axes are added, their performance deteriorates as either the servo update time or the program execution time increase. By using a distributed control architecture, the new system is said to maintain its performance, irrespective of the number of axes being controlled.
The system avoids the processing bottleneck associated with single-processor architectures. Trajectories are generated on a PC which sends incremental commands via the high-speed FireWire data transmission system to a device known as an "Intelligent Network Drive" (or Ndrive). This handles positioning and current loop closures.
All external signals, including encoder inputs and I/O are fed directly to the drive, allowing just one cable to be used between the PC and the drive. The drives are based on an 80MHz DSP (digital signal processor) and offer digital current and servo loops, with loop closures of up to 20kHz. The drives can handle encoder data at 32MHz and can link to third-party networked I/O systems via an Ethernet port.
Aerotech claims that its system can maintain a consistent 8kHz update rate across as many as 32 axes. It says that FireWire`s 3.2Gb/s data rate over optical fibres is 30-100 times faster than rival motion networks. And unlike DeviceNet or CAN, it is deterministic.
The Nmotion SMC motion engine, which builds on Aerotech`s earlier Unidex 500 and 600 products, offers facililties such as electronically geared motion, cam profiling, cutter compensation and look-ahead.
The new motion control system, which is due in the first quarter of this year, will be followed later in the year by a lower-cost, cut-down version, and by another model based on the Windows CE operating system. Higher-speed versions of FireWire could boost the number of synchronised axes to 128, says Aerotech`s UK managing director, Simon Smith.