How to build a car's intelligent neural network?

In the process of intelligent car, in addition to the upgrade of the vehicle CPU, display and sensors, there is an indispensable component: the bus system. Before the car decoding, I introduced the bus design inside the Model S when introducing the Tesla chassis.

In this article, let's understand what the bus is. And why is it so important for car intelligence? Simply put, if the human brain wants to issue instructions and needs the nervous system to transmit information, the car also has its own "neural network."

ECU is everywhere

The most common "neural network" is called CAN Bus, and Bus means bus. The CAN bus is currently the most common and most popular type of automotive internal communication protocol, which was first developed by the Bosch Group. At present, in addition to some very low-end models, most production cars use CAN as the communication standard communication protocol.

CAN itself is not a so-called "neural network". It is just the language of conversation between nodes within the network, just like the conversation between two remote computers via HTTP or FTP. In a modern car, there are roughly 100~300 or even more ECUs, namely the Electric Control Unit, as the "neural node".

Whether a car can operate normally depends on whether the ECUs are harmoniously coordinated. The number of ECUs also represents the degree of digitalization of the car. Nowadays, more and more mechanical parts are being replaced by electronically controlled parts. Typical examples are steering assist: hydraulic boost, electro-hydraulic boost, electronic boost, and wire-steering. The ECU has been applied to the core functions of the car.

These hundreds of ECUs form a local area network inside the car. Different from the external network, the information transmission feature of the local area network is that a data packet sent by an ECU will be received by all nodes, but only the node that undertakes the data packet task will execute the command.

For example, a brake light. When the ECU of the brake pedal is monitored and the pedal stroke is monitored to be changed, the ECU that monitors the taillight is notified. At this point, the ECU controls the taillights and energizes them. This simple operation, in fact, has at least 2 ECUs behind it.

In addition, due to the modular design of the car, the ECU is also divided into different modules. For example, the engine has a separate ECU system called ECM (Engine Control Module). This module consists of several ECUs that control different functions of the engine, such as throttle opening and closing, fuel injection dose, and turbine intervention timing.

CAN is responsible for setting up the LAN

For all of these ECUs to work together, a data transfer protocol is required as a "transfer". The CAN protocol is one of them, and its full name is called Controllers Area Network. The agreement was born in 1983 and is the exclusive patent of Bosch, the world's largest auto parts group.

The significance of the CAN protocol is that it has greatly promoted the electronic and digital process of automobiles. With the CAN protocol, hundreds of ECUs inside the car can set up a LAN without a host (ie, a car CPU). In 1986, SAE (Automotive Engineers Association) officially published the CAN protocol standard.

In fact, the CAN bus is a successful example of the effective cooperation between the automotive industry and the computer industry: in the second year after the CAN standard was announced, in 1987, Intel and Philips developed the world's first CAN bus-compatible chip (ie ECU). The BMW 8 Series, released in 1988, is the world's first production model with a CAN bus.

The popularity of the CAN protocol has greatly magnified the car, and its significance is not only reflected in the improvement of the electronic degree of the car, but also brought about revolutionary changes in the troubleshooting of the vehicle. You know, a modern car is running normally and requires far more code than a Boeing 747.

The OBD interface is the most direct beneficiary. This inspection interface, mandated by the US government in 1996, can make a more accurate assessment of the vehicle's operating conditions by collecting various data of the CAN bus. Even after the reverse crack, the hacker can remotely control the vehicle through the CAN bus.

However, CAN is not the only vehicle communication protocol. In order to make up for the shortcomings of the CAN protocol in some respects, the automotive industry has also developed many other protocols, such as the LIN protocol. Compared to CAN, LIN has smaller bandwidth and less data to carry, but at the same time it costs less. It is suitable for some simple ECUs, such as window lifts.

As technology advances, the amount of data inside the car has skyrocketed. In particular, the popularity of large screens and the involvement of streaming media technology have made the CAN bus incapable of working at some point. As a result, more advanced communication protocols have emerged, such as MOST, FlexRay, Ethernet, and so on.

These protocol standards have greater bandwidth and greater stability. Among them, MOST is a high-speed multimedia transmission interface, which is specially designed for the transmission of some high-rate audio and video inside the car. FlexRay is also a high speed protocol, but not limited to multimedia transmission. In the self-driving Audi A7, the on-board CPU (called the zFAS) module in the trunk relies on the FlexRay protocol to read the data captured by the front camera.

As for Ethernet, this is not dedicated to automotive technology, but a standard protocol for computer LANs. Compared with the above various protocols, Ethernet transmission speed is the fastest. According to bandwidth division, Ethernet can be divided into standard Ethernet (10Mbit/s), Fast Ethernet (100Mbit/s), and 10G (10Gbit/s) Ethernet. Note that unlike hypertext transfer protocols such as HTTP, Ethernet is the standard for the physical layer.

At present, the most developed bus protocol is the Tesla Model S, which uses CAN, LIN, and Ethernet standards to handle different levels of data. Note that although Tesla has two onboard CPUs (Nvidia Tegra processors), its bus is still a LAN architecture.

In addition to these bus protocols, the LAN standards used by the automotive industry include various types such as Byteflight, D2B, DC-Bus, IEBus, SPI, and VAN. These agreements were developed by different agencies and broke the monopoly of the Bosch CAN agreement. It has been applied to some of its models by some car brands, but it is not as popular as the CAN protocol.

In fact, the CAN protocol is not only applied to the interior of the car, but some external scenarios also require the support of the CAN protocol. The most typical is the OBD interface. Through this interface, the inspector can read the vehicle's engine operating conditions, engine oil, mileage and other information.

GM, Volvo, Tesla and other models support remote control. The principle is that the commands sent by the mobile phone first arrive at the server and are then forwarded to the vehicle communication module. After receiving the command, the in-vehicle communication module transmits the command to each ECU through the CAN bus.

In the field of electric vehicles, the charging interface actually needs the support of the CAN bus. Whether it is the European standard or the American standard interface, one of them is the CAN protocol communication interface. The role of this item is to tell the charging pile battery how much electricity is currently available. This data will be read from the monitoring ECU of the battery pack.

With the improvement of automobile intelligence, the CAN bus will be more exposed to the external network, so car information security has become a new topic. For example, Tesla was successfully cracked by car owners and hackers more than once. In addition, privacy issues have escalated, and when the vehicle is connected to the Internet of Things, your every move is monitored. This requires that not only the car network server to improve the security level, but also the CAN bus should do the encryption, authentication, anti-counterfeiting and other work from the basic level.

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