Keeping lighting on the level

  • 12-Jul-2010 09:03 EDT
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When high-power LEDs for headlamps, such as those on Audi's new A8 sedan, become less expensive and gain acceptance, chips that angle to the side could be turned on, which could eliminate the need for mechanics that shape beams.

As brighter headlights have become more common, systems that keep them directed properly down the roadway have gained popularity and in some cases have been mandated by government regulation. The headlight-leveling systems that keep bright lamps from blinding oncoming drivers are rapidly evolving into adaptive systems that shift directions during turns.

The simplest leveling systems have a manually controlled switch with an array of resistors that drives motors, adjusting the beams as vehicle loads change. More complex systems link networked switches that use LIN (Local Interconnect Network) and CAN (Controller Area Network) connections to drive motors.

This approach makes it easier to alter the design. “This configuration enables simpler engineering tuning of the system during development,” said Nick Cappa, a Chrysler spokesman.

As with many vehicle functions, design teams are pushing to automate headlight leveling, spurred in no small part by legal requirements in Europe.

“Systems use a CAN-based Adaptive Front Lighting System (AFLS) module, which has front and rear suspension sensors and utilizes CAN data regarding vehicle yaw, speed, acceleration, and steering angle to determine the lamp position,” Cappa said. “The AFLS module is wired via LIN to intelligent headlamp motors.”

These adaptive systems are rapidly evolving to shift right to left as the driver turns, illuminating the area where the vehicle’s heading. Sharing data from steering sensors is a key aspect of adaptive lighting. As more inputs become available, developers are looking for ways to implement data and direct illumination where it provides the greatest benefit.

“With the growing presence of GPS and front vision cameras, headlamp swiveling will allow an increase in the degree of freedom to adapt the beam shape and orientation as a function of the driving conditions such as city, highway, straight, or curved roads,” said Dirk Leman, Product Line Manager for the Actuators Division of Melexis.

As they add inputs, developers are also trying to reduce component counts. That is being done by utilizing data gathered for other systems.

“Sensor fusion is implemented by utilizing data available from other electronic control units present on the CAN communication system—for example, for yaw, speed, acceleration, and steering angle,” Cappa said.

The techniques for changing the direction of light beams may also change. “Aiming can be done more elegantly by blocking some of the projected light beam by controlling a shutter mechanism,” Leman said.

He noted that, when high-power LEDs become less expensive and gain acceptance, chips that angle to the side could be turned on, which could eliminate the need for mechanics that shape beams.

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