Detroit-Automotive engineers may soon have a simple, cost-effective way to remove thick wiring bundles from seats and door modules. A new electrical architecture, known as the LIN (Local Interconnect Network) bus, offers a low-speed solution for simple on-off systems, such as door locks, window lifts, cruise control, sunroofs, power seats, power mirrors, and a host of other applications.
LIN buses are far slower than CAN buses, but
The new technology, announced at the Society of Automotive Engineers 2000 World Congress in March, is already being pushed as a standard by European automakers and international suppliers. Audi, BMW, DaimlerChrysler, Volkswagen, and Volvo have teamed with Motorola and Volcano Communications, a Swedish software firm, to support a LIN standard.
For design engineers, emergence of the LIN bus could mean simpler engineering, faster assembly, and lower cost. Most vehicles currently use discrete point-to-point wiring for on-off applications, partly because CAN (Controller Area Network) buses are regarded as too costly for such simple applications. Thick discrete wiring bundles, however, must be placed in wiring harnesses and then wedged inside door modules and under power seats, making assembly difficult.
Many members of the automotive community believe that LIN could change that. Although the 20-Kbit/sec LIN bus is far slower than the 250-Kbit/sec CAN bus, it would cost about a dollar less per node. "CAN nodes are quite expensive-more expensive than they need to be for simple applications," notes Hans-Christian von der Wense, senior software design engineer for Motorola's Transportation Systems Group in Munich, Germany. "The auto industry needs a bus that can complement CAN in low-speed and low-performance applications."
LIN's cost advantages reportedly stem from the simplicity of its hardware. Instead of the two signal wires used by conventional buses, LIN uses just one. It also eliminates onboard voltage regulators and control modules, offers simpler electrical interfaces and receivers, and uses less costly microcontrollers.
Consortium members say that implementation of the LIN bus will be simple. A single chip will be placed in stepper motors at nodes along the LIN bus. The chip will then attach to three wires that connect to the LIN bus. Power for the single-wire bus will come from the vehicle's 12V battery.
Automakers are hopeful that they will be able to standardize LIN and receive broad acceptance for it, thus simplifying their relationships with vendors. They say they have no plans to use LIN for automotive multimedia or critical safety systems, such as antilock brakes or powertrain modules.
The first application of LIN buses may come as soon as the 2002 model year. DaimlerChrysler plans to use it in a dashboard application. Audi also plans to go into mass production using a LIN bus for a vehicle's sun roof and rain sensors.