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As an original contributor to the development of SERCOS, Bosch Rexroth still emphasizes that particular communications network — for motion control and I/O: “IndraDrive Mi has the drive and its intelligence integrated directly on the motor, allowing additional Sercos III and peripheral devices to be connected directly to the IndraDrive Mi,” explains Alzayyat.

For example, for one module requiring Sercos III fieldline I/O for a specific application, decentralized Sercos III I/O can be directly connected, thanks to a combination of hardware, firmware, and communication protocol available.

“This reduces the use of DIN-rails in the cabinet because the Sercos III fieldline I/O is mounted on the machine module and not in the cabinet,” says Alzayyat.

That said, traditional cabinets are increasingly modular in their own right, to dramatically simplify setup and reduce cost. DIN rails take the lead here: Electrical installations for industrial control were quite complicated before the widespread adoption of this standard. Now, the elegantly simple standardization on DIN rail geometry allows for organizing compatible terminal blocks, power supplies, motor starters, relays, circuit breakers, I/O, and contactors inside control cabinets into tidy rows — by simply snapping into the rails.

Established by the Deutsche Institute von Normen (DIN), this German Institute of Standards ensures dimensional uniformity so that the rails accept the mounting of all the compatible electrical products mentioned. The most common DIN rail is 35 mm in length (TS35 or DIN 46277-2) and 7.5 to 15 mm thick. Designers can choose products standardized to DIN rail dimensions from any number of manufacturers — to save time and space, while centralizing electrical contacts. In fact, dc and ac power supplies, terminal blocks, Ethernet switches, and discrete power relays abound for DIN setups.

A Multi-Ethernet interface allows Bosch Rexroth IndraDrive Mis to drive various components.

According to Christian Kastinger, key account manager at B&R Industrial Automation Corp., Roswell, Ga., truly modular assemblies (such as the B&R setup shown on this page) require four things: Fine granularity of automation components and cabinetless designs — and in communication, one bus for everything, plus versatile topologies.

“Until recent years, the limiting factor in modular motion-system design was often the structure of the electrical system — with power distribution, control, and drive technology in a centrally located control cabinet,” adds Markus Sandhöfner of B&R. Why? “Electrical and electronic equipment and its connections for all possible option combinations vary, so the control cabinet and cabling could only be completed after the entire machine was assembled. In contrast, modularization of mechanical connections for future expansions is (for the most part) implemented rather easily.”

Now, however, electrical and electronic equipment design is increasingly flexible. A basic requirement for this type of modular structure is the ability to connect all types of different control and automation hardware anywhere via the system bus. Here, “B&R relies on the Ethernet-based Powerlink fieldbus,” reports Sandhöfner. “It allows all combinations of bus, ring, or star topologies to be implemented, which makes it easier to move system components away from the centralized control cabinet. The control cabinets are then always identically equipped and can be small while meeting the needs of the main machine.”

Powerlink also allows easy pathways to other fieldbuses — to simplify connection to purchased modules that use their own fieldbus interface.

Hardware modularity abounds here, too: “Even the spectrum of electric motor functions is represented,” concludes Sandhöfner, “from frequency inverter controlled three-phase asynchronous drives and synchronous drives for servo, torque or linear motors to highly precise stepper motor control with integrated feedback.”

Make contact

• Modular DCAM stations - deprag.com
• Jesse Hayes, Schunk automation product manager - (919) 767-1975
• MECHATROLINK Members Association - mechatrolink.org
• Drives with multi-Ethernet interface - boschrexroth-us.com
• DIN rails - altechcorp.com