What are Adaptive Headlights?

Adaptive headlights use a combination of technologies to control the direction, distance, brightness, and beam pattern of headlights to provide better illumination at night while minimizing the glare for drivers of other vehicles. 

The two common types of adaptive headlight systems are called adaptive driving beam (ADB) systems and adaptive front lighting systems (AFS). Adaptive headlights use cameras, radar, lidar, and light sensors, along with weather, speed, and steering information, to actively respond to changing situations. 

Most adaptive headlight system functions can be classified under one of the following three headlight technologies: 

• Automatic high beams: turning high beams on when there are no cars in front of the vehicle and switching back to low beams when other vehicles are detected
• Curve-adaptive headlights: an AFS system that adjusts one or both headlamp beams into a turn so the driver can see better into the turn
• Adaptive driving beam headlights (ADB): adjusts the brightness of different parts of the driving beam to provide more light in unoccupied and less in occupied areas

Most new vehicles include adaptive high beams or systems where the headlights pivot when cornering. Adaptive driving beam headlights that use beam patterning are available in Europe. The newly adopted National Highway and Traffic Safety Administration (NHTSA) standards in the U.S. have started a race amongst automotive manufacturers and suppliers who sell into the U.S. market to develop products that meet the new standards. The FMVSS 108 standard, in particular, defines the use of simulation for ADB virtual certification. 

A wealth of data shows that vehicle-vehicle and vehicle-pedestrian accidents are more prevalent at night. A staggering 76% of fatal crashes involving pedestrians occur at night. Between 12-15% of all traffic accidents cite headlight glare of oncoming vehicles as a contributing factor. Newer systems that allow drivers to see more of the road and further down the road are having a positive effect, reducing pedestrian-vehicle crashes by as much as 23%. 

These numbers have led automotive manufacturers, including Tesla, Audi, BMW, Ford, Honda, Mercedes-Benz, Porsche, and Toyota, to explore new adaptive lighting technologies. At this time, the technology is not mandated. Still, the auto industry sees various forms of adaptive headlamps as a way to provide consumers with additional safety features and differentiate their new vehicles in a highly competitive market.

Headlights no longer consist of a single low beam and a single high beam bulb in a reflector, with manual switches to turn one or both on or off. Headlights are now advanced systems with software, complex assemblies, and vehicle network interfaces. 

To provide automated high beams, cornering, and patterning, every manufacturer has their own configuration and system name, but most components can be grouped into the following categories. 

Sensors

A variety of sensors gather information, including turning, vehicle speed, lighting conditions, weather, driving conditions, road width, and the location of other vehicles. Newer model-year vehicles are now also using GPS location and map data to provide information proactively to the system. Sensors can be as complex as optical or thermal/infrared cameras and radar, lidar, or sonar ranging devices already on vehicles to support other safety systems. These devices provide the size, location, and velocity of objects, especially oncoming cars. Simpler sensors provide the position of the steering wheel, ambient lighting conditions, and weather information. Accurate performance of ADB systems is dependent on establishing a precise feedback loop between the sensors and the ECU to help execute the necessary action.

Software and Electronics

The information from the sensors is delivered to the adaptive headlight control hardware so the control software driving the system can adapt to the current situation. The electronics can be integrated into the headlight assembly, a separate control unit, or the vehicle control computer. Along with control responsibility, the software and electronics also provide power to the headlamp assembly with the proper voltage, pulse width modulation (PWM), and quality. 

Headlamp Assembly

The bulk of an adaptive headlight system consists of the headlamp assembly itself. The control system tells the assembly how the headlights pivot, the brightness of each light source, and the bright and dark zones for adaptive driving beams. Most importantly, the headlamp assembly contains the optical light path. Engineers use extensive simulation and prototyping to optimize the optical characteristics of the assembly.

Here is a description of each subcomponent in the headlamp assembly: 

Housing

The headlamp assembly is packaged inside a housing module that is sealed from the environment, integrated into the front of the vehicle, and possible to replace as a unit. 

Lenses and Reflectors

The beam shape and quality from each light source are shaped by optical lenses built into the front of the housing assembly or by reflectors behind the light source. Some reflectors are adaptive and can be adjusted or tilted as instructed by the adaptive system. 

Actuators

Many adaptive headlight systems change the headlight beam using stepper motors or actuators to move components in the light path or to swivel the pointing direction of the entire assembly. Actuators in headlamp assemblies need to be robust enough to survive vehicle shock and vibration, extreme weather conditions, and potentially daily usage over long periods of time. 

Light Source

The light source is the heart of any adaptive headlight system. They can consist of one or more halogen bulbs, xenon projector lamps, LED lamps, an LED matrix, or lasers in some new cars. The light choice determines the cost, light color, and intensity. Each light source type has advantages and disadvantages, but the control and brightness of LED bulbs or matrix assemblies make them the currently preferred light source. 

Beam Patterning

A variety of technologies are used to modify the intensity of light in a beam. Light is either selectively created or masked to produce the desired pattern. Here are a few of the most common approaches: 

• Masking: The simplest approach is to use a piece of tinted material that is actuated to block the top part of the beam to remove the high beam when oncoming traffic is detected, shade a specific vehicle, or block light from shining on the side of the road. Stationary LCD filters can also be placed in the light path between the source and lenses to mask the beam selectively. 
• Micromirrors: These patterning systems work like digital light processing (DLP) projectors, in which a rearward-facing light source projects light onto a micromirror assembly that then reflects light with the desired brightness pattern forward through the lens. This approach can not only provide selective shading, but it can also be used to project messages onto the pavement in front of the vehicle. 
• LED matrix: The most common approach for beam patterning, often called adaptive LED headlights, uses an array of small bright LED lights arranged in a matrix. Each LED becomes a pixel that can be brightened or dimmed as needed. 

Thermal Management System

Creating bright light, regardless of the light source, creates significant heat. However, newer light sources like LEDs create less infrared energy than those generated by older systems, which could previously use that energy to melt snow and ice off the lenses. Therefore, an important part of a robust adaptive headlight system is the thermal management solution that keeps the light sources, power system, and electronics cool while also moving waste heat to the lens assembly. 

Engineers designing adaptive headlight systems, from simple high-beam assistants to the latest AFS, need to address several significant challenges:

1. Vehicle shock and vibration
2. Packaging
3. Response time
4. Glare 
5. Light location and pattern 
6. Thermal management
7. Thermal cycling
8. System integration
9. Safety standards
10. Performance optimization
11. Cost reduction
12. System validation/night drive testing

Most vehicle manufacturers have learned to integrate simulation-driven product development into their design process to overcome these challenges and optimize their ever-evolving adaptive headlight systems. Simulation is most commonly used on adaptive front light systems in the following ways:

Component Optics Design and Optimization

Simulation models the light source, lenses, active and passive reflectors in the headlamp assembly. Many headlight experts use Ansys Zemax OpticStudio software to optimize each component and the optical assembly. The parametric nature of the tool, intuitive user interface, and fast solve times make it easy to look at the wide variety of optical situations an adaptive system will see. 

Virtual Optical Performance Visualization

Once the component optics are done, engineers can place the resulting beam into a systems-level modeling tool like Ansys Speos software to visualize what the vehicle's driver sees as they travel down the road. Every possible driving condition can be simulated to see how the system performs well before a prototype is constructed. Going one step further, real-time simulation tools like Ansys AVxcelerate Headlamp software can take the full system for a virtual night drive and test the behavior of the whole system in any driving scenario. One of the most expensive and time-consuming steps in developing an ADB system is nighttime testing. Simulating for drive testing and validation can greatly reduce both. 

Electro-mechanical Design and Optimization

The components and assemblies, including connectors, actuators, headlight components, electronic modules, and power systems, all see electrical and mechanical loads that can be surveyed and designed for early in the design process with tools like:

• Ansys Mechanical software for mechanical components and assemblies
• Ansys Sherlock software for electronic assemblies
• Ansys Maxwell software for motors and actuators

Thermal management can be simulated with Mechanical software, Ansys Icepak software, or the Ansys Fluent solution. 

Control Software Verification and Validation

Since control software is an important part of any adaptive automotive system, a tool like the Ansys SCADE Suite environment can be used to model and develop the headlight control software. In combination with simulation tools like AVxcelerate Headlamp software, the control software behavior can be verified and tested in any situation, and regulatory requirements can be evaluated virtually.

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