CIP Motion has punched a hole in an urban myth of industrial automation. The myth: Standard Ethernet cannot be used for motion control and so something needs to be developed that is based on Ethernet; adding time slice algorithms to the firmware or hardware of devices, or simply building a proprietary network with CAT5 cables and a gateway to standard Ethernet.
This is important because even today users are starting to run up against limitations in their current implementations. They want co-ordinated motion control with more than 32 axes on a single network. They want to synchronize axes connected to different controllers. They want a common programming and configuration environment for variable frequency and servo drives. They want discrete inputs and outputs integrated with rotary machines. They want video cameras mounted inside the machine. There are a number of semi-proprietary technologies that address each of these issues but EtherNet/IP with CIP Motion is the first to address them all using entirely standard Ethernet with IP.
In order to deliver these user benefits, ODVA have and continue to enhance the CIP (Common Industrial Protocol) and EtherNet/IP specifications to address these critical motion control requirements:
- Controller to drive interfaces
- Precision time synchronization between devices (or CIP Sync)
- Distributed registration across the entire machine
- Distributed Programmable Limit Switch and Camming functionality placed anywhere in the process and driven by any axis in the system
- Motion control accomplished through multiple drive types suitable for the application, including servo drives, Voltz/Hertz drives, and Vector drives
- Master encoder reference information placed directly on the Ethernet network for coordination of multiple axes from any given, existing axis
In order to deliver the benefits of Ethernet and IP, there are also demands from outside of the ‘motion centric’ world:
- Standard infrastructure components must be usable;
- Layers 1 and 2 of the Ethernet implementation of the ISO-OSI 7 layer model may not be changed;
- Layers 3 and 4 of ISO/OSI 7 layer model must be utilized for all communications using IETF specified TCP/IP technology.
- Existing standards should be used, not act as a basis for further development; and
- The solution must be applicable on standard off-the shelf chips.
There are also requirements from the application developer community:
- The network must be able to support 100 axes with a 1ms update rate;
- Position loops must be closable at a time base of less than 125 uS;
- Any axis can be either a variable frequency or servo drive with full networked configuration;
- It must be possible to synchronize discrete signals with a motion axis; and
- I/O, video and voice traffic must be carried on the same Ethernet as motion traffic.
The unique capability of EtherNet/IP to meet all of these requirements in a standard, open, and seamless manner does not eliminate motion control as a unique discipline in industrial automation. Instead, it sets free engineers to develop more innovative and highly integrated solutions, increasing the level of user benefits delivered by control systems and machines. The network becomes simply a part of the solution, not a part of the problem.