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Seamlessly integrated in POWERLINK-based safety networks, SafeMC rounds off the safety system as a complete solution without complicated wiring.

Seamlessly integrated in POWERLINK-based safety networks, SafeMC rounds off the safety system as a complete solution without complicated wiring.

Providing employees optimum protection against injury or death and maximizing machine capacity seem to be conflicting goals. The safe servo drives from B&R’s ACOPOSmulti series can be seamlessly integrated in POWERLINK-based networks via openSAFETY and used to monitor the motor in real-time. This allows B&R to reduce reaction times to errors by a factor of 10, and the resulting maximum impact energy by a factor of 100, compared to traditional safety circuits. Improved machine dynamics with increased safety is no longer a contradiction.

When it comes to protecting the lives and well-being of their employees, companies must make no compromise. That compromises are made nonetheless can be attributed to three factors: The workers themselves are confronted with a choice between operating machines more safely and operating them more efficiently. There is an even broader conflict of interest for a company’s management. A company must not only protect its qualified workforce and capital investments, but ensure that both are able to provide maximum productivity. Furthermore, there’s no such thing as a perfect technical solution or a moving machine part that can be stopped instantaneously.

Even traditional safety circuits with cut-off relays are subject to response times inherent in the system, comparable to the moment of shock a driver experiences before slamming on the brakes. The error detection and response time, for example when the safe maximum speed is exceeded in setup mode, is generally around 80 ms. If the error was caused by an incorrect set value from the control system, this delay would be sufficient for the drive to accelerate to its maximum speed before the usual torque cut-off and any additionally activated short-circuit breaking procedure is initialized. This effects the amount of force with which an obstacle would be hit, and of course expands the total stopping distance. The permissible maximum speed must therefore be set accordingly in order to maintain the necessary level of safety.

100 times more safety

By integrating safety technology right in its servo drives and servo motors, B&R has redefined how stopping distances and impact energy are calculated. The relay-free SafeMC safety circuit, which is installed in all ACOPOSmulti drive units, automatically monitors every reaction of the motor to the instructions from the servo drive. This is done using safe, fully digital, high-precision, high-resolution encoders that are mounted to the motor shaft on all B&R synchronous servo motors and are certified according to EN ISO 13849. The electronics are integrated directly in the drive to avoid additional response times. This has enabled B&R to shorten the error response time to 7 ms. In the event >>
of error, the motor now has less than a tenth of the time to accelerate and to gain hazardous momentum.

Because the kinetic energy and corresponding response distance increase with the square of the speed, these two critical characteristics are reduced to less than 1/100 compared conventional solutions. “This not only improves workplace safety, it also increases productivity on the machine,” states Dipl.-Ing. Alois Holzleitner, Business Manager for Motion products at B&R. “Depending on the priority, the reduction of these characteristics and the resulting shorter braking distances makes it possible to reduce the safety distances, thereby allowing for smaller machine dimensions and/or increased permissible speed limits during operation with Safe Limited Speed.”

Seamless integration in existing systems

The safety logic included in the ACOPOSmulti servo drives is identical to the proven Safe I/O components from the X20 series. “This gives users the peace of mind that comes with using electronic components that have proven themselves thousands of times in the field,” says Dipl.-Ing. Alois Holzleitner. “Plus, the resulting synergy has a direct effect on the costs and uniformity during system development.”

ACOPOSmulti with SafeMC can be seamlessly integrated in the existing system with the SafeLOGIC safety controller and the X20 Safe I/O. For developers, the ACOPOSmulti with SafeMC units are addressed no differently than the X20 I/O channels. Of course they are also managed within the same development environment: SafeDESIGNER in B&R’s Automation Studio. Autonomous configuration of the SafeMC components and the embedded parameter chip allow quicker and easier configuration during maintenance. Logging and password protection make it possible to track maintenance actions.

A major advantage of B&R’s “Integrated Safety Technology” is the elimination of redundant cabling and external monitoring modules for the safety technology. Data is transferred with virtual wiring via the machine bus system in an intrinsically safe protocol called openSAFETY, which enables easy data communication with the control system while reliably excluding feedback. B&R automation solutions do this using POWERLINK. As the name suggests, openSAFETY is not tied to a specific manufacturer and can be used on any fieldbus system, preferably in Industrial Ethernet networks. This makes it easy to integrate the safe drives regardless of the controller being used.

A further advantage of virtual wiring over the network is the possibility of designing modular machine concepts. Without the complicated wiring of E-stop chains, it is simple to connect ready-made machine parts, including safe drives. This allows a single safeLOGIC safety controller to access up to 80 safe drives from our ACOPOSmulti series, which ranges up to 120 kW.

Certified intelligence

In February 2010, B&R received certification from TÜV Rheinland for the safety-oriented drive system and its intelligent safety functions, which B&R calls Smart Safe Reaction and which helps ensure optimum usage of safety equipment. This was followed by the certification of the functions STO (Safe Torque Off), SBC (Safe Brake Control) and SS1 (Safe Stop 1) up to Cat. 4/PL.e in accordance with EN ISO 13849-1 and up to SIL 3 in accordance with EN 62061/IEC 61508. Certification up to Cat. 3 PL.d and SIL3 is sufficient for the remaining functions SOS (Safe Operating Stop), SS2 (Safe Stop 2), SLS (Safety Limited Speed), SMS (Safe Maximum Speed), SDI (Safe Direction) and SLI (Safety Limited Increments).

A clear benefit of the system intelligence in ACOPOSmulti SafeMC is the universal availability of diagnostics provided by the integrated trace and oscilloscope functions. Together with the control and status functions, these can be used to display the monitored safety limits and speeds. Thanks to simple data transmission to the process control system provided by the bus connection, the diagnostics can also be integrated in the machine’s visualization and control systems. This provides machine operators and supervisors with in-depth, easy-to-understand information about the cause and type of safety violations as well as the system’s response, and enables them to respond immediately.

“SafeMC with ACOPOSmulti and B&R synchronous servo motors are based on the open network-based safety standard openSAFETY. This combination is the logical complement to the portfolio of integrated safety components for machine and systems manufacturing, which has proven itself in the field and has been certified for quite some time,” says Alois Holzleitner. “This makes B&R one of the first manufacturers to provide a fully network-integrated safety system including intelligent drive safety functions. Such a system increases machine efficiency and productivity, while at the same time improving workplace safety.”