Page 17 - RHP IT

MACHINE BUILDING

For machine design

SAFETY CONTROL

WITH THE DEVELOPMENT OF SAFETY OVER ETHERCAT IN PLCS AND DRIVE CONTROLLERS, POWERFUL NEW
TOOLS ARE AVAILABLE FOR MACHINE BUILDERS TO PUT TO USE IN THEIR NEXT MACHINE DESIGN PROJECT,
WHICH CAN HELP PROVIDE THEIR MACHINES WITH A VALUABLE TECHNOLOGICAL EDGE, SAY MARK
CHECKLEY AND MIKE KEEFE OF KEB AUTOMATION.

he safe operation of machines often requires safety selectable functions according to
functions to limit speeds, directions of rotation or the requirements. A number of Safe
Taxis positions. With traditional safety solutions, Motion functions offer advanced
dangerous operating states are detected and avoided using functionality and handling, which
external safety modules. However, this only serves to carry a safety certification up to
increase the complexity of the machine’s safety concept. In SIL3.
contrast, drive controllers with integrated safety functions For example, a robotic
and safety PLCs including certified function blocks can be controller may utilise ‘Safe
used today. Acceleration Range’ to monitor the
Modern communication systems not only realise the acceleration rates of the robotic
deterministic transfer of control data, they also enable the arms. Detecting an abnormal
transfer of safety-critical control data through the same acceleration can provide a faster
medium. EtherCAT utilises the Safety over EtherCAT FSoE error response than waiting to
(FailSafe over EtherCAT) protocol for this purpose. The reach a limit switch or torque limit.
benefits of using FSoE in machine design projects are Another example is a machine or process that may Example of traditional safety wiring vs. networked FSoE wiring).
numerous, but here are five key benefits to consider: require a motor shaft to spin in only one direction. Spinning
the motor in an unintended direction could cause The actual configuration of the KEB Safety Drives is
1. Reduced and simplified wiring: One simple yet key catastrophic damage to the machine such as damaging a carried out using the certified Safety Editor, within
benefit of FSoE is the reduction of the discrete safety screw or special bearings. A design engineer might utilise COMBIVIS Studio 6. This is where the safety functionality
wiring. It is no longer necessary to wire all the discrete the ‘Safe Direction’ function to ensure that the motor only and limits can be configured. These safety-related settings
safety I/Os back to the safety PLC. The advantages of rotates in the intended direction. can be saved and downloaded to other drives via
reduced wiring become most evident in applications that COMBIVIS or via the controller. Current parameters and the
have longer cable runs or where many safety devices are 3. Detailed state machine: Each FSoE slave device is built error history can be used for system diagnosis. The export
required. on a state machine backbone. On start up, the state function makes it easy to create the required
FSoE enables the evaluation of discrete safety inputs machine must be incremented through sequentially before documentation.
and even safe encoder signals (position) in the case of it is possible to transmit the process data. In combination
KEB’s COMBIVERT S6 or F6 drive controllers. This with the log in KEB’s Combivis Studio 6 programming 5. Safety function blocks: With the number of safety
information can then be communicated from the drives to environment, tracking EtherCAT and FSoE statuses or functions available in the KEB S6 and F6 drive controllers
the safety PLC over the SIL3 certified FSoE protocol. Both troubleshooting errors is much simpler. that can be transmitted via the process data of FSoE, it
the safety information and regular machine data can be For example, if an FSoE configuration is used that is could be overwhelming to start the programming of the
transferred via a standard Ethernet cable, which means the dependent on encoder data such as ‘Safe Limited Speed’ safety PLC. However, KEB’s Combivis Studio 6 provides
wiring and terminations are quick and easy with little (SLS), but no encoder has been configured within the drive pre-certified safety function blocks according to the
chance of wiring mistakes. safety setup, a bus configuration error will display on the PLCopen Safety standard. These pre-prepared function
With this simple connection all safety functionality on log. The state machine utilised by FSoE and the detailed blocks minimise the programming time of the safety PLC to
the FSoE and standard EtherCAT drive control can be log functionality within Combivis Studio 6 can be a allow for easy startup while also enabling more complex
achieved. This allows for more complex machine safety powerful tool in the commissioning of new machines or programs if needed. In addition, Combivis Studio 6 clearly
design without worrying about the cost and time involved troubleshooting existing machines with functional safety. identifies safe and unsafe variables, making it clear which
with wiring. Resulting in the time spent on wiring and variables can and cannot be used with safety function
testing I/Os can be saved or put to better use with more 4. Configurable process data: Utilising FSoE and the blocks. Utilising these tools allows for almost limitless
comprehensive machine commissioning. wizards built into Combivis Studio 6 allow for the simple options when programming the safety functionality within
and easy setup of dozens of different configurations of FSoE and the safety PLC.
2. Flexibility of safety functions: With FSoE, there is also process data. On the simple side, configurations with six In conclusion, with the increasing desire and
more flexibility in the selected Safe Motion functions FSoE frame elements can be used to control the safety requirement of functional safety in new machine designs,
available in KEB EtherCAT drive controllers. It is no longer functionality and to read back the statuses. On the more FSoE can be a powerful tool for machine builders. Utilising
just about implementing the dual-channel STO (Safe complex side, configurations with 15 FSoE frame elements KEB’s range of FSoE devices (drive controllers and safety
Torque Off). The sixth generation of KEB Automation drives can be used to support additional safety functionality. This PLCs) can save time and money in all stages of the
offers scalable safety functions directly in the drive allows for more flexibility when setting up the FSoE and machine lifecycle, from initial design through to
controller. The device variants are Compact, Application allows the user to select as many or as few safety functions commissioning and servicing.
and Pro for the COMBIVERT F6 and S6, enabling as needed. MORE INFORMATION: www.keb.co.uk

June 2021 • INDUSTRIAL TECHNOLOGY 17