On-board computer (automobile)
The term on-board computer ( body computer module , BCM for short; also multi-function display, trip or trip computer , driver information system) is understood in motor vehicles as a display device with which various information can be queried. The information is usually presented in the instrument cluster , on a separate screen in the center console or on the dashboard .
Well-known manufacturers of on-board computers are, for example, Continental , Magneti Marelli , Bosch , Motorola , ACDelco and Telefunken .
Functions
The information that can be displayed on an on-board computer includes, for example:
- Average consumption
- Service intervals
- Oil level / temperature
- Tire pressure
- Battery control
- Strapping information
- Current consumption
- Average speed
- Current speed
- Remaining range with the existing tank filling
- Remaining fuel quantity / tank message
- Travel time
- Outside and inside temperature
- Date / time
- Diagnostic messages for errors and defects
In the meantime, information such as radio stations ( RDS ), time and date, hands-free telephone system, air conditioning functions, etc. can be called up and operated in the on-board computer. In the past, independent displays such as control elements (for example information on engine oil level, brake wear) or a service display are now often integrated into the on-board computer. In upscale equipment lines, the on-board computer display can also show navigation information ( global navigation satellite system ). Distance warning and similar functions are also available.
It is also common today that the on-board computer is no longer a pure display device, but also an input device, for example for setting the volume for the parking aid or for controlling the brightness of the interior lighting.
History and dissemination
The first on-board computers appeared at the end of the 1970s (especially in US cars) and only had a black and white LC display or fluorescent display for outputting the recorded information and calculated calculation results as well as a few microswitches for user input. It was not until the 1980s that the first European manufacturers (above all Renault and Citroën ) followed suit . Modern on-board computers can also be operated via touchscreen (for example Lexus GS and VW Golf VII ) or project various information onto the windshield via a head-up display (for example Chevrolet Corvette or Toyota Prius ). If a digital speedometer ("mouse cinema") is installed, its display elements are usually also used to display the on-board computer displays.
In the past (at least outside of the USA ), on-board computers were mostly only available as optional accessories. Since the 2000s, however, they have increasingly been part of the standard equipment of a vehicle in Europe.
On-board computer as the central node of the vehicle electrics
In older vehicles, the on-board computer was mostly limited to the functions of fuel consumption and the like. Its electronics were mostly located in the housing of the instrument cluster. It was only linked to a small extent with other control units such as the engine control or ABS. In contrast, vehicles from the year 2000/2003 onwards are increasingly linked to other vehicle systems.
This turns the on-board computer into the central control center for the vehicle. All other control units (ABS / ESP, airbag, engine control, etc.) are connected to it and permanently transmit their functional status and possible malfunctions to the actuators and sensors of the respective control unit via CAN bus . If, for example, the ABS control unit detects the fault "Front right wheel speed sensor defective", this fault is first passed on to the central computer and then shown to the driver on a display and by indicator lamps on the instrument cluster.
In a Fiat Stilo z. B. the on-board computer is also connected to other sub-nodes: door computer, node for the passenger area and rear section. In this vehicle, when the switch for the rear window heating is pressed, the signal from the button is first sent to the body computer, from where a relay for the rear window heating is switched and at the same time a signal is sent to the door computer in the driver's door, which activates the exterior mirror heating.
The entire lighting is also on the on-board computer. In the Fiat Stilo, for example, there are no longer any switches for the interior lighting, but only micro buttons that report a lighting request to the control unit and are also supplied with power from there. The lighting request can also be ignored if the ignition is not on (this only applies to the individually switchable reading lights in the rear area, which, however, are the entire interior lighting when viewed together).
The advantages of a central on-board computer include:
Pro Simple networking of different systems without having to run separate cables to the instrument cluster for each system. Pro Central linking of all data. Pro Better configurability by the driver. Seen on the Fiat Stilo, you can only open the driver's door via central locking or ignore all doors and the button on the tailgate. Pro Retrofitting accessories (cruise control, etc.) is easier when the vehicle is already pre-equipped and only the lever is missing and needs to be activated this function only in the instrument cluster / host. Working pro energy saving. Depending on what the computer is connected to, the lighting can be controlled down to the smallest detail. The glove compartment lighting, for example, is not on forever if the box is not closed properly, while in old vehicles a contact indicated whether the light is on and that burned until the battery was empty, the “body computer” decides “And automatically switches off the lamp (s) after a few minutes. Easier to locate per lamp failure. Since there is a separate line for most lamps, the central computer can also send a message to the display in the instrument cluster, which then shows whether a brake light is defective and, if so, on which side.
Disadvantage:
Contrary to this, disturbances in this computer can spread throughout the vehicle system. Cons A defective central computer can hinder troubleshooting and make it very expensive. Cons Even individual errors that are not relevant for driving safety can generate undesirable secondary errors. In the case of the Stilo, for example, a burned out lamp in the cigarette lighter can cause undesirable tension on the lighting cable for the ashtray. Against Much more cable required, therefore higher weight. In other words, if you want to monitor lamps depending on the side even when they are switched off, they must also be individually connected to the central computer. A parallel connection with the central computer is no longer possible, since the side of the failure must also be localized.
literature
- Cathrin Köhler: User concepts for car on-board computers: analysis and suggestions for optimization. Thesis. Hanover, 2002
- Gregor Nöcker: The paperless shipping company. LIT Verlag Berlin-Hamburg-Münster, 2002, ISBN 978-3-8258-5052-4 (About the use of the on-board computer in transport and logistics).