Controller Area Network CAN Bus: Nervous System of the Vehicle

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Controller Area Network is considered one of the most important inventions in the automotive sector. No wonder, as the CAN bus, developed by Bosch in 1983, is the central nervous system of modern cars. It connects all electronic control units and enables them to exchange digital data via just two wires.

On January 29, 1886, Carl Benz registered his three-wheeled motor car with the Imperial Patent Office in Berlin, Germany. With the patent document DRP 37435, the official birth of the automobile was marked. The installed single-cylinder four-stroke engine delivered just under one horsepower, and the vehicle reached a top speed of about 16 km/h (approx. 10 mph).

The first automobile was, of course, still far removed from today's vehicles. With the introduction of the first electronic components, the vehicle increasingly gained functionality, comfort, and safety. An important milestone was the VW Type III in 1968, which, as the world's first series-production compact car, featured an electronic engine control unit—the Bosch D-Jetronic.

High Transmission Security is Ensured

The development of electronics in vehicles, simply put, progressed from the basic electric starter to networked control units that are essential for driver assistance systems and engine management. However, the rapidly increasing electronics caused a major problem. With more and more electrical and electronic functions in the vehicle, cable connections became overwhelming. Until then, every sensor, motor, and switch was wired individually to the control unit. The result: the wiring harness threatened to reach a length of 2 km (approx. 1.2 miles). A solution was needed, and it came from Bosch—specifically from Siegfried Dais and Uwe Kiencke along with their team. In 1983, they developed a data transmission system for digital signal exchange between electronic components—the Controller Area Network (CAN). In 1985, Dais and Kiencke were able to file the first patent for it. The initial tested systems demonstrated extremely high transmission security and availability, even in the face of electromagnetic interference pulses. All transmission protocols were developed in the form of a cost-effective microchip. It sounds simple, but it wasn’t, as Dais shared: “We had no specific expertise and had to figure out a lot on our own. For example, none of us had specialist knowledge in serial data transmission.”

First Commercial Use in the S-Class

Despite the initial difficulties, the team was able to quickly demonstrate successes compared to competitors, as Uwe Kiencke recalled: “We had by far the most advanced development, a very high data transmission rate, and were able to demonstrate an exceptionally low error rate.” By 1991, the time had come. Mercedes-Benz was convinced by the CAN bus and implemented the new data transmission system in the S-Class.

The CAN bus did not replace all cables, but it contributed to "reducing the cable clutter and linking the functions of various electronic controls," as stated by the automotive supplier. With the invention of the CAN bus, the two "Bosch-ians" laid the foundation for future developments. Whether it’s engine control, driver assistance systems, cockpit and infotainment systems, or lighting—all these functions rely on coordinated and simultaneous commands from several different control units. For this reason, Siegfried Dais and Uwe Kiencke were honored in 2008 with the Eduard Rhein Technology Award "for the invention, international standardization, and dissemination of the Controller Area Network communication system."

Networking and Automated Driving Push CAN to its Limits

CAN enables data rates of up to 1 Mbit/s and a data field of 8 bytes per message. Additionally, it ensures the transmission of prioritized messages with guaranteed delivery. However, with increasing vehicle networking and automated driving at Levels 3 to 5, the classic CAN bus system reaches its limits. Its maximum data rate is insufficient for the enormous data volumes generated by sensors such as cameras, radar, lidar, or ultrasound. Moreover, security also plays a significant role. The architecture of the CAN bus, developed in the 1980s, does not include integrated encryption or authentication but rather "relies" on the correctness and authorization of the information.

Therefore, modern vehicles rely on a more powerful and secure onboard network architecture. This is where Automotive Ethernet comes into play, for example. It can complement or replace the CAN bus with significantly higher bandwidths ranging from 100 Mbit/s to 10 Gbit/s. This is necessary to transmit video streams and complex algorithms in real time.

With CAN-FD and CAN XL, further developments of the classic CAN bus with higher data rates are also available. However, these are more commonly used for less data-intensive secondary functions. But either way: the invention of the Controller Area Network was undoubtedly a revolution in vehicle development.