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Ethernet, High-Speed Bandwidth Lead Evolution of Motion Networks
Ethernet solutions offer precise synchronization, multi-purpose networks
Al Presher, Contributing Editor -- Design News, April 8, 2007
Distributed operations using Ethernet, safety functionality and more sophisticated solutions that leverage the bandwidth of high-speed motion networks are the leading trends in the evolution of automation/motion networks.
Since the introduction of SERCOS 20 years ago, networking has been an important factor in motion control. But now, with major players such as SERCOS III and Profinet IRT (isochronous real-time) moving toward broader adoption, there have never been more options or more potent solutions available.
Migration to Ethernet Automation Networks
“Motion networking is not that new, what is new is the migration from motion-specific network technologies to real-time networks designed for all manner of machine control purposes including motion,” says David Greensmith, product manager of Ethernet Motion Products for Baldor. “While these networks were conceived for motion purposes, they were not always ideal for fieldbus purposes, distributed control and I/O devices.”
Greensmith says the sheer bandwidth of Ethernet has merged the functionality of the fieldbus and motion bus into one complete system, and brought with it a far more complete communications system. Functionality such as firmware updates, configuration and diagnostics can also be done using the same network. He says this creates “total network visibility” and the ability to configure, operate and maintain devices and systems from a single communication access point.
Jeff Faris, a program manager for Rockwell Automation, agrees and says, “motion networks do not stand alone.” Customer applications are evolving to include technologies beyond motion where the machinery, especially in the printing and packaging industries, is becoming more modular and needs to be scalable to respond to consumer needs.
Faris says functions such as safety, sensing, vision and information tracking are also an important part of these automation systems, but increasingly it's a customer expectation that the machines will use a single network. “They start from an automation network perspective, but the common denominator is Ethernet,” he says.
More Powerful Networking Features
A key element in the evolution of the networks is more sophisticated control functionality on the networks themselves.
IEEE-1588, which has been referred to as a transparent clock, is a key technology that has recently been included in the specification for Ethernet IP. This capability allows time to be accurately synchronized throughout different distributed devices on high-speed networks. Faris says the breakthrough for use of this technology was defining the mechanism and demonstrating the capability the clock could be synchronized to a very tight level through many different nodes on a network.
Dr. Joseph A. Profeta III, director of product management for Aerotech Inc., says there is clear movement toward decentralized architectures and distributed intelligence that make it possible to implement more sophisticated solutions. “Many companies are moving to architectures where the intelligence in the system is being pushed out toward the end points,” he says. “What that requires is a faster network and more intelligence at the nodes.”
Profeta says motion coordination can be done at the centralized level, with the network providing a method for effectively communicating with intelligent drives. For I/O, devices are also more intelligent and communicate status information over the network.
“We are putting more effort into software than ever before,” he says. “Low-cost FPGA and DSP technology allows us to write software that provides greater flexibility, intelligence and more configuration options.”
Safety as the Next Frontier
A variety of suppliers mentioned safety functionality as an important addition to motion networks.
“We see a strong trend toward adding safety functionality to the networks solutions that are currently being implemented,” says Helmut Kirnstoetter of B&R Automation. “In the last two or three years, the development of decentralized architectures has been driving the development of these products. Moving to safety is the next solution step for digital motion networks.”
| Motion Networking Products Round-Up |
An important part of the “evolution of motion networks” is product innovations that demonstrate the growth and direction of automation and motion control networking. Below is a sampling of current products and technologies that offer a snapshot of the trends toward more sophisticated motion networking solutions. REAL-TIME DISTRIBUTED COMMUNICATIONS VIA ETHERNET B&R Automation offers bus-capable servo drives for machine manufacturing in the power range from 400W to 64 kW with its ACOPOS family of drives. Using Ethernet Powerlink, up to 240 axes can be operated on one line using the same network. When controlling axes use multiplex operation, 400-µs transfer speeds can be achieved. Decentralized operation is a key element for the ACOPOS drives because the motion controller is built into the drives, and the drives are communicating information to each other over the network. Ethernet Powerlink provides a broadcast network where every node is allowed to receive information it is configured to receive. Information including current position is exchanged across the network between the drives every 200 or 400 mic µsec. ACOPOS servo drives support the operation of all standard motor types such as synchronous motors, asynchronous motors with or without a feedback system, linear motors or direct drives. SYNQNET INPUT MODULE OFFERS FAST POSITION CAPTURE Danaher Motion's new High Speed Input Module enables 32 high-speed digital inputs to utilize the fast position capture functionality of the company's ZMP 3 U controller. The module offers hardware input latch speed with latency of less than 350 nsec, and up to 16 simultaneous high-speed capture inputs using from a direct connection to a 10 MHz FPGA. Adding high-speed inputs for time-based position to capture the SynqNet network provides a way to report what happens in one spot to any other location on the network. It also fits well with important SynqNet features such as phase lock control, and the ability to achieve clock synchronization at the FPGA level to achieve tightly coordinated motion. The target for the input module is high-speed registration applications, and it provides a way to use and communicate multiple position captures for on-the-fly adjustments. DRIVES FEATURE VARIETY OF FIELDBUS INTERFACES Digital servo drives from Beckhoff Automation have integrated the power electronics into compact sizes. The small dimensions, integrated EMC filters and plug-in connectors allow simple and cost-effective installation into control cabinets. An internal 32-bit microprocessor provides high-quality control and sampling times down to 62 µs. The variable fieldbus connection permits easy integration into EtherCAT, as well as a variety of other control environments including PROFIBUS, SERCOS, CANopen, DeviceNet and Ethernet. EtherCAT solutions offer high performance by implementing data exchanges in hardware and minimizing system jitter through use of distributed clocks. ASIC or FPGA slave hardware eliminates the need to buffer Ethernet packets at each node for reading and writing of data. Instead, each EtherCAT slave reads and writes its data as the frame is passing through the slave node, which adds only a few nanoseconds of delay to the telegram. According to the company, reading and writing on-the-fly make it possible to control 100 servo axes in 100 µs, or 1,000 digital I/O in 30 µs. MODULAR DRIVES SUPPORT SERVO AND VECTOR MODES The S120 ac Drive from Siemens expands the Sinamics S120 system into a modular system for both single-axis and multi-axis applications, and supports servo and vector modes. The unique drive design separates power and intelligence, increasing the combinations of power sections and controllers for better flexibility and scalability. Built-in Easy Positioning functionality is designed for positioning tasks such as those found in automatic assembly machines and material handling systems. On-board safety-integrated technology, including “safe off” and “safe brake,” helps to protect operators as well as machinery from injury or damage. Communication interfaces supported include PROFIBUS and PROFINET, and provide networking solutions for remote access, high-speed communications and integration into existing networks and automation systems. The drives are available in single phase 230V in the power range 0.25 to 1 hp, and three-phase 460V in the power range 0.5 to 400 hp. The power modules are available in compact block construction (0.25 to 125 hp) or as chassis units (150 to 400 hp). NEW I/O MODULES FOR INTELLIGENT SERVO MODULES A key aspect of Elau's Intelligent Servo Module technology is its networking strategy. Quick-connect cables run between shared power supply and distribution modules, and quick-connect cables link distribution modules and drop in a line or tree topology (instead of a daisy-chained ring) to the servo modules, which use SERCOS as the motion bus. Power and I/O signals are in the same cable, and there is no need for encoder feedback cables because the drives are integrated with the motors. SERCOS communications run over copper, as they will in SERCOS III, which eliminates fiber optic cabling, complex terminations, optical receivers and transmitters. Most recently, ELAU has developed an I/O module as an option for its iSH servo modules that replaces distributed I/O blocks as well as separate device bus cabling. The I/O option module replaces separate distributed I/O modules and device bus, using the motion bus to link up to a maximum of eight sensors or actuators per module using popular M12 plug connectors. All eight connections can be defined as inputs or outputs. ETHERNET POWERLINK AC DRIVES Ethernet-compatible 3-phase MotiFlex ac drives from Baldor combine single-phase drives with a machine controller and software development environment. The addition of three phase drives means users can build Ethernet systems with the optimum choice of motor technology for each axis, from small to large loads. Rotary and linear versions of brushless servo and ac vector motors are all software selectable, and the company says there will also be support for dc servos. For machine builders trying to move to all-electronic architectures, this approach can provide software-centric, highly reconfigurable systems. A single machine controller can manage different system components such as I/O, absolute encoders, Ethernet PowerLink DS402 positioning drives, steppers and up to 16 interpolated axes. Applications are implemented using the Ethernet Powerlink protocol to seamlessly link with standard Ethernet networks. Free ActiveX tools, provided as part of Baldor's development environment, provide tools for developers to create Windows-based PC applications that can communicate with the real-time motion hardware via Ethernet, such as a man-machine interface or remote monitoring software. DISTRIBUTED ETHERNET MOTION NETWORKING The Ensemble from Aerotech Inc. is a multi-axis controller for moderate-to high-performance applications using high-speed communication through 10/100 Base T Ethernet or USB interfaces. Using the high-speed Ethernet network running over CAT6 cable using standard RJ45 jacks, the system implements an architecture where a centralized controller calculates the trajectories and uses the network to communicate to intelligent drives. The drives close the position, velocity and current loops and commutate the motor, and are synchronized on the bus at a 1 msec level. The Ensemble can control brushless, brush or stepper motors or stages in any combination. A simple parameter interface also allows easy integration to third-party motors and stages. The controller encoder interface includes TTL quadrature input or analog encoder input. Multiple Ensemble controllers can be controlled from a single Windows PC through Ethernet or USB, allowing many more than 10 axes of motion to be operated from one host PC. EXPANDED RANGE FOR KINETIX 2000 SERVO DRIVES Kinetix 2000 servo drives from Rockwell Automation are scalable for handling a wide range of applications ranging from 300 W to 3 kW. Additional power ranges provide OEMs and end users with more complete selection of motion control solutions, and are targeting small packaging applications. One simple power rail serves as a mounting and connecting system, making design and installation fast and easy while minimizing wiring and maintenance costs. A SERCOS Interface provides a single, digital fiber-optic link and easy integration with the Allen-Bradley Logix controller platforms for multi-axis applications. An optional Line Interface Module can be used to eliminate up to 100 wire terminations. Smaller drive modules and other space-saving features result in smaller electrical enclosures. A simple modular design lowers wiring costs by reducing the total number of connections, and Kinetix servo motors use Smart Motor Technology to provide automatic identification of correct motor-to-drive connectivity, which reduces commissioning time. SCALABLE PLATFORM ENHANCES CONNECTIVITY Bosch Rexroth's IndraLogic PLC platform offers both DeviceNet and EtherNet IP connectivity, which allow users to choose their dominant field bus with minimal engineering changes. Uniform DeviceNet connectivity is available as a scanner in the Rexroth motion and PLC controllers, the company's panel-mount Inline I/O and IP67 Fieldline I/O systems and IndraDrive servo and spindle drive platforms. Ethernet I/P adapter functionality with unsolicited explicit messaging is available via the local Ethernet port of the CNC and PLC controller, in addition to Profibus DP as its standard fieldbus platform. IndraLogic PLC systems offer a flexible control platform and the ability to design centralized or distributed automation solutions using IEC 61131-3 software and open interfaces. Systems include PC-based PLC system, controller-based PLC system or drive-based motion logic system. The new support for both DeviceNet and Ethernet IP increases the flexibility of connectivity of systems to meet a wide range of specific application needs. AMKASYN COMPACT CONTROLLERS New AMKASYN controllers from AMK Drives provide a single controller and networking solution for real-time visualization and control needs. These compact controllers include a PLC and integrate visualization into the development environment of the PLC using the CoDeSys programming interface, which allows for fast access to all PLC status and program variables. Real-time communication with the drives and I/O in the system are implemented using either the ACC bus (based on CANopen) or real-time Ethernet. The real-time bus system provides synchronous operation of axes, and allows for integrated communication and diagnostics across all levels up to the drive. Robust terminals provide IP65 protection against splash water and dust. Controllers are available in different design configurations including a variety of sizes, resolution and control using a touchscreen or keypad. |
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Ethernet, High-Speed Bandwidth Lead Evolution of Motion Networks
Ethernet solutions offer precise synchronization, multi-purpose networks
