Embedded Inertial Sensor-Based Road to Vehicle Pitch Estimation for Automatic Headlamp Leveling

The irradiation angle of the headlights is regulated by the United Nations Economic Commission for Europe (UNECE) for safe driving by preventing glare from oncoming drivers. Automatic headlamp leveling is a system that automatically controls the angle of the headlamp horizontally to meet safety regulations. To control the irradiation angle, the automatic headlamp leveling system must estimate the road-to-headlamp pitch angle. This paper proposes an accurate and robust road-to-headlamp pitch angle estimation system using a low-cost MEMS (Micro Electro Mechanical Systems) IMU (Inertial Measurement Unit) sensor. The proposed system sequentially estimates the headlamp pitch angle, the road slope angle, and the road-to-headlamp pitch angle. First, headlamp pitch angle is estimated using the gravity from IMU. Second, the road slope angle is estimated based on vehicle prior knowledge that the vehicle is moving in the direction of the road. Finally, road-to-headlamp pitch angle is estimated by subtracting road slope angle from headlamp pitch angle. However, the measurement data of a MEMS IMU sensor contains various types of noise, such as bias and white noise. For that reason, reducing the effects of MEMS IMU noise is highly important when estimating the road-to-headlamp pitch angle. Therefore, the proposed system focuses on minimizing the effects of the low-cost MEMS IMU noise. In addition, the proposed method is verified by simulations and experiments. The simulation analyzes the effect of the MEMS IMU sensor noise on the estimation accuracy and precision. Finally, the proposed algorithm shows more robust and accurate performance compared with other methods on the test and common road verifications.