By Kent Lennartsson, Research Manager, Kvaser AB A Controller Area Network (CAN) is a message-based protocol that allows microcontrollers to communicate with devices without the need for a host computer, similar to today’s Internet of Things communication. The use of CAN began in the automotive industry and has since branched out into a multitude of sectors, including industrial automation. However, CAN in itself is not equipped to handle the control processes needed for this complex industry. Instead, a secondary, higher layer protocol was required to make adoption possible. In the early 1990s, Allen-Bradley (now a part of Rockwell International), developed DeviceNet, a higher layer protocol for control systems specifically aimed at automation. While not the only higher layer protocol in use at the time, Allen-Bradley’s swift introduction of the specification through the Open DeviceNet Vendor Association (ODVA) made it more widely available. It was this availability that allowed CAN to become a viable option for the purposes of industrial automation (today there are several, customizable options available. For a comparison of the most popular, click here).
Classic CAN in Industrial AutomationClassic CAN is used in nearly every industrial sector, including manufacturing and assembly lines, heavy equipment, such as cranes and forklifts, and even simple sequence control demands like mail sorters. The protocol has remained the industry standard for a myriad of reasons, but the primary advantage to this system has been its proven history of reliability. Industrial automation of today requires a multitude of control systems moving in precision. In an industry that relies on schedules and accurate production, speed and efficiency are a requirement. Because of this, errors must be limited and should be quickly detectable. In a CAN system, there is constant communication between devices. Messages deemed a high priority are given precedence over others, removing any issues of message collision. Additionally, error messages are given high priority, allowing for swift error detection and correction. This ensures small mistakes do not become larger, more costly ones. Despite CAN’s prevalence in industrial automation, new communication technologies loom.
The Introduction of Industrial EthernetToday, Ethernet is the global standard for network communication. Developed in the 1970s, this technology is similar to CAN in that it allows devices to communicate with each other without the need for a central processor. It was not until relatively recently that this technology began to be fitted for settings of industrial automation. Industrial Ethernet is simply Ethernet for industrial applications. It differs from the technology used in our homes and offices in that the messages communicated between devices use deterministic protocols, promoting the high likelihood of a desired outcome (e.g., the end product of an assembly line matches the initial design specifications). Some of the primary advantages of the system over traditional CAN are:
- Higher data transfer speeds (up to 100 MB/s) at higher network lengths
- Faster data transfers mean more data per second can be accessible from “the cloud”
- More individuals are familiar with Ethernet versus CAN
- More software support is available when used with Linux or Windows