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Integrated Drive Safety
More safety-related software functions in drives create flexibility
Al Presher, Contributing Editor -- Design News, July 14, 2008
What are the most exciting developments in safety for motion control and automation?
Safety integrated into individual products and new functionality available in standard drive products is an exciting development for machine builders and end users. By encapsulating these functions, what we are really doing is enabling safer machines that can be more easily tailored to individual applications. Machines are safer for operators, more customizable to maintenance tasks without defeating safety circuits and helps protect the machine, as well as increase productivity.
Safety-integrated functions available previously, like a safe off or E-stop functions, have been extended to new types of stop. Safe stop 1 and safe stop 2 functions can stop the motor in a monitored time or perform a safe operating stop where we hold the motor at zero speed, although it can't produce any rotational speed, but hold full torque and position. Other capabilities include safe limited speed and safe speed monitor to provide highly effective application protection for personnel and machinery.
What are the key technology trends in this area?
A key trend is that OEMs are making their machines more modular. Safety functions integrated into the modular pieces of the system, or drives, means they can function independently. Users can create safety zones to stop portions of the machine without stopping the entire machine, to improve uptime and productivity. Machines also react faster with safety functions in the drive itself.
Another trend is the economics of eliminating relays and wiring by utilizing safety-approved integrated software functions. New standards such as NFPA 79 and the harmonized European safety standards are making it an approach that can create an economical machine using the latest safety technologies.
What challenges are engineers encountering when implementing this technology?
A big challenge for engineering personnel is the process of moving from wired relays to a more customizable, sophisticated approach. The key to getting past the learning curve is coming up with graphics-based software setup. From there, it's customizing the more sophisticated software capabilities for their specific machine and meeting specific machinery safety directives.
Many OEMs want to have the same exact machine, hardware and software, to ship anywhere in the world. By moving to the harmonized standards or machinery directives for safety, we are moving closer to that goal. The European community is leading the way and the EU directives have been at the forefront of setting safety standards.
What does the future hold for safety in motion control and automation?
An important future development is safety-related functions over a communications fieldbus or industrial Ethernet. The big advantage is reduction in wiring and one network for the complete application. The PROFISAFE profile that we use for PROFIBUS and PROFINET has a safety telegram built into the fieldbus or, more commonly, Ethernet network.
This is also opening up possibilities of safety functions over wireless and innovative machine design at the user level. It creates a capability, for example, to utilize mobile panels with an integrated E-stop function on the panel. As the panel moves to different parts of the machine, operators can stop the entire machine but the HMI itself can operate differently depending on its location within the machine. For large assembly manufacturers in the automotive industry, wireless safety and control has appeal. I think that within a year we will see safety-integrated solutions over wireless technologies in the marketplace.
| Author Information |
| Craig Nelson is the drives product manager for Siemens Energy & Automation. |
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