Description:
When driving in conditions with suboptimal lighting, the use of headlights is essential for safe travel. However, headlights pose a fundamental safety conflict as with increasing headlight intensity, visibility is improved, but this simultaneously increases the glaring effect on pedestrians and oncoming traffic, reducing overall safety. To address this issue, the UN has launched a regulation binding all original equipment manufacturers, or OEMs, of the concurring regions to implement automatic head light levelling systems that aim to keep the headlight alignment optimal. The regulation will apply to all new type approvals starting from September 2026 and all vehicles starting from September 2029. Since in most cases OEMs are offering a great variety of different automobiles, this regulation is putting high pressure to find a general cost-effective solution that works for every model and configuration. When switching from manual headlight alignment to automatic, the system needs to consider how load from passengers and luggage is tilting the vehicle and what is the vehicle pose in respect to the road angle. In static situations, this can be handled with a 3-axis accelerometer sensor in combination with an extended Kalman filter. When adjustment in dynamic situations is required, the complexity of algorithms between sensor data and actuators controlling the headlight alignment becomes significantly higher. The system needs to now take into account accelerations, breaking, driving in bends and vibration effects. To improve interpretation of these dynamic situations, a 3-axis gyroscope must be implemented to the system as well. Additionally, in dynamic situations, a fast response time is crucial and when considering the relatively small angles of adjustments needed, effects of lifetime degradation start to play are role in accuracy. This means that high reliability and performance of the measurement capability is needed for the whole system to retain its accuracy. Development in the MEMS field has enabled manufacturing of low cost, but extremely accurate, stable and reliable accelerometers and gyroscopes, which makes them a good candidate to address the aforementioned problems. This paper is reviewing an automatic headlight levelling solution utilizing a combined accelerometer and gyroscope sensor, which is based on capacitive silicon MEMS technology.