Design of Adaptive Steering Headlight System Optimized by Single Chip Integrated Circuit

The electronic control of the xenon headlights by stepper motors is aimed at directing the headlight beam to minimize the intensity of the oncoming vehicle while illuminating the curved road. However, the location of the vehicle motor driver chip has a significant impact on the efficiency of the system.

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High-intensity discharge lamps (xenon lamps) Vehicle headlights are increasingly becoming the technology of choice for vehicle manufacturers worldwide. In order to maximize the use of high-quality lighting provided by xenon lamps, and to reduce the risk of excessive xenon light caused by improper orientation, the importance of adaptive steering headlight systems (AFS) is increasing.

These systems are capable of slightly adjusting the beam of the headlights in the vertical direction to compensate for variations in the vehicle's inclination relative to the road surface. At the same time, they are also able to rotate the headlights accordingly, depending on the change in vehicle steering. Such a beam provides the best and safest road lighting ahead, significantly improving the visibility of the road when the driver turns.

Automatic leveling - weakening glare

The working principle of the headlight automatic leveling system is to ensure that the light and the road surface are horizontal when the vehicle is tilted (see the figure below). When the vehicle is at a standstill, it may be tilted for some reason, such as having a passenger boarding a car, loading luggage, or even refueling the fuel tank. Similarly, when the vehicle is in a traveling state, the vehicle may be tilted due to braking or acceleration. In both cases, the headlights of the car must remain level with the road. The headlight automatic leveling system adjusts the angle of each headlight based on a series of sensor data, especially the suspension compression data from the front and rear axles.

Improve safety by rotating the headlights

The vehicle's data network includes real-time sensor data on steering angle and wheel speed. Based on this information, the adaptive headlight system with headlights adapts the light distribution to the steering angle of the vehicle, so that oncoming turns and forks—especially the driver's gaze point—can be optimal. Lighting (see picture below). This significant enhancement of light can reduce the driver's tension and fatigue, and increase the visibility of obstacles; these obstacles are even fixed by the headlights. Many studies have shown that rotating the beam headlights increases the illumination of the driver's gaze point by 300% when the vehicle turns.

Stepper motor control

The rotation of the headlights of each vehicle is achieved by using a stepper motor, in which one stepper motor controls the rotation in the vertical direction and the other is used to control the rotation in the horizontal direction (see the figure below). The motor reacts based on data from many sensor feedbacks around the vehicle. The communication of information is achieved through the vehicle's data network system. The LIN bus is a practical choice for headlamp control, while the CAN bus collects sensor data and distributes it to the entire vehicle. Stepper motors are an excellent choice for headlamp adjustment applications because they are low cost, rugged, and offer a large torque.

As for the placement of the driver integrated circuit chip for controlling the stepping motor, there are two options available. The first type is called direct drive. In this method, the driver chip is mounted in the main microcontroller printed circuit board (see the image at the top of the figure below). The board is located far from the headlight components and associated stepper motors and may be located in a central electronic control unit (ECU) attached to a vehicle bulkhead (insulation wall) or in the passenger compartment of the vehicle. "Comfortable" environment. The main disadvantage of this method is the excessive line and high intensity electromagnetic compatibility radiation required.

The second method is mechatronics. In this method, the driver chip is mounted with the motor (see the bottom of the figure above). Thanks to the highly integrated single-chip products, such as the AMIS-30621 and AIMS-30623 stepper motor controller ICs manufactured by AMI Semiconductor, the electromechanical integration method of the adaptive steering headlight system capable of directly mounting the chip in the motor Become more feasible. This approach is very beneficial because the interface between the central microcontroller and the mechatronics module requires only a low electromagnetic compatibility bus. The mechatronics method adopts a modular design, and the maintenance of the headlight assembly is convenient, so the benefits are remarkable.

Split hardware and software

The application of stepper motor drivers requires the design of both hardware and software. This can become very complicated, especially if multiple axes need to be controlled at the same time in an adaptive headlight system. Prior to the advent of stepper motor controller ICs, the past approach was to invest in microcontrollers and develop proprietary software, or use conversion chips (see image below, left and center pictures). The main problem with software-based solutions is that development costs are high and there are inherent difficulties in verifying the correct operation of multiple axes under any conditions.

The so-called conversion IC provides an interface between the microcontroller and the driver chip. The overall solution adds some extra hardware, but it also leads to more difficult to manage complexity and more software requirements (see the figure below, Right picture). The disadvantage of using a conversion chip is that it complicates the design of the printed circuit board while losing some of the modular advantages.

Single chip method

The integrated stepper motor controller reduces the complexity of requiring multiple axis adaptive headlight systems compared to other methods and provides a direct solution for vehicle manufacturers to support modularity and Integrated vehicle design.

AMI Semiconductor offers four mixed-signal devices that combine bus connections, positioning, electronic control, and motor drivers in a single package with a footprint of 7mm by 7mm. These devices are small in size and high in performance, and they ensure the modular design of motion control software and robust motor operation while directly mounted inside the stepper motor.

The above two models (AMIS-30621 and AMIS-30623) are characterized by a LIN bus interface. This approach saves wiring costs and has better electromagnetic compatibility than systems that place the drive at the remote end, an advantage that is key to solving problems in difficult automotive applications. The other two improvements (AMIS-30622 and AMIS-30624) have an I2C serial interface that can be used as a peripheral device on a single printed circuit board adjacent to the microcontroller.

Sensorless stop detection

Most automatic headlamp systems are capable of initial position adjustment when the lights are turned on. This mechanical mode basically adjusts the lights to the lowest possible point within a specified time. There is a problem with this program that noise is generated and wear is increased due to the stepping motor striking the stop point. Another solution is to use sensorless stop detection, which features AMIS-30623 and AMIS-30624 components. These components operate quietly and have low wear, but are also able to accurately align positions and use semi-closed loops close to the electromechanical stop point without the need for an external sensor.

Summary of this article

The use of a single-chip stepper motor controller integrated circuit enables the design of an adaptive headlight system to be greatly simplified and provides superior technical performance under conditions that are often difficult to operate. The integrated design greatly enhances the overall reliability of the headlights and means that only a few capacitors are required for external circuit components. Similarly, the time to market, the design, and the cost of the entire system will be positively affected.

Mechatronics and modular methods are supported by single-chip stepper motor controller ICs. These two methods are manufactured for a wide range of vehicles in the case of rapidly growing vehicle electronic systems that make electronic system structures too complex and expensive. Businesses are highly respected.