The Body Control Module – Pulling the Automotive Strings

Electronics in vehicles are taking on more and more functions. Today, basic functions such as vehicle lighting, activating the windshield wipers, and immobilizers are an indispensable part of every car's standard features, accompanied by comfort functions such as remote control keys and automatic climate control. But innovations such as automatic start/stop and tire pressure monitoring aided by sensors are to be increasingly found in series production models. Together, all of these functions belong to a vehicle's body electronics. The comfort and additional safety offered by these functions are now almost as important to a car as the engine under the hood. And what do they all have in common? Body control modules pulling the strings in the background.

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1.The microcontroller is the data processing center of the body control module.

2.At the high-current output for example the rear window defroster is connected.

3.The driver chips control the vehicle exterior lighting.

4.The relais are controlling for example the windshield wiper or the central door locking.

5.With the 24-pin signal interfaces (signal-socket) switches, sensors or the vehicle data bus is connected with the body control module.



Processors and Actuators: Powering the Central Body Control Module



As the brain acts as the control center of living organisms, so a body control module controls part of the vehicle electronics, explains Andreas Wolf, Head of the Continental Body & Security Business Unit. As in a PC or laptop, at the heart of a control module lies a processor together with an associated working memory. Interfaces connect the body control module with sensors, actuators, and other control modules in the vehicle. If, for example, a driver opens their vehicle with the remote control key, the control module receives an encrypted signal from the radio receiver built into the car. An algorithm processes this information in the processor and passes it on to the actuators. The digital signal triggers the mechanical action and the vehicle's doors are unlocked. But this capability alone does not make the control module absolutely essential. Even without the aid of a control module, the doors could be unlocked with the remote control key as a single, locally restricted function via conventional relays. The decisive argument in favor of a body control module is its ability to unite multiple functions in one place. By doing this, it offers one simple but key advantage: Fewer cables. Were everything to be operated via traditional relays, the variety of electronic functions in modern vehicles would render it completely impossible to accommodate the complexity and weight of the cables in a passenger car.



Monitoring Energy Flows



The possibility of integrating different functions presents a further advantage. A body control module can manage energy flow, thus ensuring that too many functions do not consume large amounts of energy at the same time, overloading the electrics. The principle behind it is simple: The most important function at any one time always receives an optimal supply of energy, taking priority over other functions. This capability will play a major role in electric vehicles for another reason. In the future, one of the tasks of a body control module will be to employ clever energy management to maximize the distance a car can travel before the battery needs to be recharged.



Data Buses: Communication Networks in Vehicle Electronics



The integration of functions in body control modules already stretches beyond body electronics. This becomes obvious when considering the start/stop function, which automatically turns off the engine when the car stops and starts it up again when the driver accelerates. With the aid of a battery sensor, the relevant body control module monitors the performance of the vehicle battery and determines whether the start/stop function is activated. The body control module must also be connected with further sensors and other control modules such as the engine controller. The decision as to whether the automatic start/stop system can be used is then based on the battery charge level, the temperature of the engine or the interior, and which other electronic functions currently require energy and with what priority. This communication is made possible by the interfaces to the control modules, which are attached to the vehicle buses. The term bus refers to the cable network that facilitates communication between different electronic components. This allows control modules in a vehicle to exchange information and transforms the vehicle electronics into a coordinated overall system.



Ethernet: Fast and Flexible Data Transfer



Developments in vehicle electronics are clearly tending toward the integration of many individual functions in a central body control module. Our task is to push this integration ever further, explains Wolf. This means that control modules used in top-range and luxury vehicles employ a consistently larger and more complex range of functions, communicate with the overall vehicle electronics system to an ever greater extent, and exchange a constantly increasing amount of data. As a consequence, the requirements for communication buses grow as well. Current vehicle buses such as CAN, FlexRay, LIN, and MOST are quickly being pushed to their limits. In the future, we will be making increasing use of high-performance Ethernet to improve data exchange in vehicle electronics. With the communication bus known from computer networks, we achieve a data transfer volume of 100 Mbit/s between each node in a network while simultaneously using lighter and more flexible cables, continues Wolf.



Expertise for Efficient Electronics



When it comes to vehicles in the lower price segments, the development of body electronics is subject to other challenges. Particularly in emerging industrial nations, the automotive industry is dominated not just by the need to offer inexpensive products, but by two other factors as well: Extremely rapid product development cycles and a variety of manufacturers who produce in small batches. It must therefore be easy to adapt the central control modules to the various vehicle types and equipment variants. To keep costs low, Continental's central control modules have been based on a modular platform architecture for some years now. In this way, Continental's standard version of the central body control modules (Basic Function Controller) ensures that important basic functions can be used in different vehicle types with no significant adjustment required. Should the customer be in need of more powerful hardware, two Basic Function Controllers can be hooked up to a local network. Alternatively, the customer can opt for the Advanced Function Controller with a much wider array of functions and performance offerings.



With this extensive product and technology portfolio, Continental covers all the requirements of modern vehicle architectures.