PROFINET Fast Start Up (FSU) feature allows IO Device to go instantly into a ‘power on’ state in response to signals from an IO Controller. Such functionality is a high priority for industrial robots with Automatic Tool Change (ATC) since it can increase the flexibility of production lines and reduce the number of robots per cell.
In car body production, the total cycle time for a single robot cell can be as low as 45 seconds (including the delay for tool change). Many Industrial Ethernets suffer from slow start up, typically in the range of seconds compared with 100 ms range for fieldbuses, and this can be too slow for many production needs. By optimizing the PROFINET protocol and how data is utilized by end devices it is possible to reduce start up times dramatically.
PROFINET FSU defines the time between ‘power on’ and receipt of the first cyclic input data to be less than 500 ms. The protocol optimizations needed to achieve this are standardized in the PROFINET specification as follows:
- Use of fixed transmission parameters (only for copper wires), instead of automatic detection, which reduces start up by up to three seconds.
- The network address is not passed to the IO device on every cycle, but only at first start up. Parameters are stored in the IO device memory and re-used. This may save several seconds.
- IO Devices announce their readiness to establish communication instead of waiting for the IO Controller to search. It is possible to save up to one second this way.
From the OEM/end-user point of view, a number of other optimizations are possible. For example, start up can also be reduced through the use of suitable hardware. Wireless may also help, either by keeping communication up all the time or by establishing communication in advance of ‘power on’.