While it is most widely associated with the automobile industry, Controller Area Network (CAN) technology has broad applications across very different sectors, from industrial automation and robotics to clean tech and medical equipment.
In fact, some of the first users of CAN were not from the automotive industry, but from the textile machine manufacturing sector (Lindauer Dornier GmbH). The “CAN in Automation” international users and manufacturers group has been around for more than 25 years and helped to create the CANopen application layer to support industrial machine communication. CANopen has extremely varied applications in the industrial automation/control market—ranging from injection molding equipment and cigarette machines to cranes, forklifts and letter-sorting machines.
An Introduction to CAN
At its most basic, CAN is a communication protocol that allows different parts of a system to communicate without the need for a central computer. In a car, for example, the CAN protocol maximizes the performance of the vehicle by facilitating the real-time exchange of information between the electronic control units (ECUs) that control various systems within the vehicle, such as the engine, fuel injection and anti-lock brake systems.
In industrial automation, CAN is ideal for any assembly situation or simple sequence control. The CAN protocol can be responsible for transferring information between parts of a robotic arm when performing manufacturing duties, adjusting machinery performance to accommodate changing line speeds, or any number of more complex automated manufacturing and production processes.
Benefits of CAN
CAN is widely considered one of the most reliable methods for transmitting real-time data. The CAN protocol determines the priority for each message being sent, allowing for an easy, uninterrupted flow of communication, even when multiple messages are being sent simultaneously. CAN is also highly efficient at detecting and diagnosing errors.
This is especially important in a sector like industrial automation, where the effectiveness of whole supply chains can depend on the efficacy of an automated system. On-time delivery and product quality can suffer immensely from even small errors.
However, CAN isn’t without its faults. One of its principal constraints is a limited bit rate (the speed at which data can be transferred) in relation to the length of the network (the distance over which that information is relayed). Through a cable length of 40 meters, classical CAN maxes out at 1 megabit per second.
Industrial Ethernet to the Rescue?
To meet the needs of higher bandwidth applications in industrial automation, such as multi-axis motion control, industrial Ethernet has emerged as a favorite solution.
Ethernet was developed in the 1970s and has become the global standard for network communication. Industrial Ethernet is, quite simply, Ethernet for industrial applications. However, it differs slightly from its traditional counterpart in that it uses specialized deterministic protocols to guarantee a high probability of a desired outcome (for example, performing a single, highly specific automated task).
Ethernet provides speeds of up to 100 megabits per second for data transfer, but these advantages come with some concerns.
First, despite the high-speed data transfer, industrial Ethernet can be surprisingly inefficient. With a minimum frame size of 80 bytes with 46 bytes of data, a large amount of overhead remains when transferring 0 to 8 bytes of data (the frame size used in classical CAN), which can lead to less efficient transfers. Ethernet also requires an IP address, which makes it a less secure method of transferring data, opening it up to cyberattacks. Lastly, due to the extensive use of CAN in the auto industry and in industrial automation, the price tag of switching to Ethernet controllers comes with additional costs of retrofitting the physical systems as well as the higher layer protocols that control the systems.
How CAN FD Is Changing the Conversation
The latest iteration of CAN is CAN FD (CAN with flexible data rate), which improves upon the limited bit rate of classical CAN by offering 8 megabits of data transfer per second, even with cable lengths greater than 40 meters. CAN FD also transmits data blocks of up to 64 bytes in a single message, so real-time data transfer is nearly instantaneous. The method by which CAN FD improves over classical CAN is right there in the name: by eschewing standard bit times and alternating between long and short bit times during message transmissions. And, if you are considering an Industrial Ethernet upgrade, consider this: CAN FD controllers are compatible with existing CAN systems, so industrial automation upgrades are not only simple, but cost-effective too.
CAN and Ethernet Working Together
But CAN and Industrial Ethernet are not necessarily at odds. The two protocols can be adjusted to work together, offering users the benefits of both systems. CAN-to-Ethernet gateways allow the two protocols to communicate, keeping CAN at the heart of the communication but leaning on Ethernet where beneficial. As an example, cranes at container ports have utilized Ethercan—a lightweight CAN-to-Ethernet gateway—to connect to terminal operating systems. The crane operators are able to view important real-time, CAN-collected data such as the tire pressure, load weight and fuel levels of the crane; but supervisors also receive the data, via Ethernet, allowing them to take action remotely if any issues are detected.
The Future of CAN
Even as complexity continues to increase with connected cars and more advanced robotics, CAN is likely to continue its widespread application as a go-to reliable communications protocol in industrial automation and the automotive industry. While industrial Ethernet offers higher speeds, it is less secure and less consistent than CAN. Though, with the improved bandwidth of CAN FD and simpler, more efficient CAN-to-Ethernet gateways, the most compelling answer may be to adapt the advantages of both protocols to achieve a complex and complementary solution that allows both systems to focus on their key strengths.
Jesse Paliotto is Director of Marketing at Kvaser.
