Attività

A system for automatic headlight leveling control in BMW headlight level sensor which are offset in the longitudinal direction for measuring the vehicle body pitch angle in the form of a level difference. An electronic control unit determines a desired value for the headlight adjustment as a function of the first derivative of the directly measured or further processed level difference. In one embodiment of the invention, electronic control unit determines a static level difference and a dynamic level difference, and the desired value is determined as a function of the first derivative or the second derivative of the dynamic level difference.

Wiggensbach, Nov. 25, 2021. Future level 5 autonomous vehicles will need a significantly greater number of sensors. Many of the sensors which will be required are still in development. On the other hand, many level 2 and 3 functions are already in vehicles today, such as in comfort and driver assistance features. As a result, level sensors have been installed on car chassis for many years to ensure safety and for driving dynamics. They supply the necessary information for headlight beam and chassis control systems. These level sensors are installed in vehicles with all types of propulsion systems, from passenger cars with classic combustion engines to hybrid and electric cars. With an annual production volume of several million units, Swoboda is one of the world’s leading suppliers of this type of sensor.

Level sensor evaluation for comfort and safety functions
Modern vehicles have a number of new features which assist the driver in making driving safer and more pleasant. Some increase comfort and others improve safety. Two functions which fall into the category of adaptive driver assistance systems are chassis control and headlight beam adjustment. Both functions are controlled based on information from the chassis.

Dynamic chassis control improves both safety and vehicle comfort. The driver selects their preferred “driving feel”, such as sporty for a more energetic drive or comfort for longer journeys. The control unit dynamically adjusts the chassis. Level sensors installed on the chassis in the control arm provide the control unit with the information it needs for its control algorithms to make the adjustment.

Modern LED vehicle headlights have a much longer range than conventional halogen systems and the risk of blinding other road users is increased. For this reason, EU regulations require that vehicles with headlights more powerful than 2000 lumens are equipped with dynamic headlight beam adjustment.

If a vehicle is loaded in the rear, the rear of the vehicle sinks and the headlights point slightly upwards. If the vehicle is loaded to such an extent that this effect causes other road users to be blinded, the headlights must be adjusted downwards. This is a rather static alteration and it is made using relatively simple headlight adjustment mechanisms. However, this mechanical adjustment has only a limited effect while driving. In a moving vehicle, the height of the headlights is also altered by dynamic effects such as uneven ground. Therefore, in order to dynamically adjust the range and height of the front headlights to suit the road conditions, level sensors continually measure the vehicle’s level and their information is sent to control units in a similar way to the chassis control.

Functional principle
A level sensor, also known as a rotation angle sensor, is designed to detect the change in angle of a car’s control arm. Control arms are connecting elements installed on individual wheel mounts perpendicular to the direction of travel. They guide the wheel carrier in an approximately vertical direction and transmit the shear forces between wheel and body, stabilizing the wheel alignment. The movement of the control arm is transmitted to the sensor via a coupling linkage. The design of the sensor which monitors this movement is divided into two entirely separate parts: a mechanical part and an electronic part. The mechanics translate a change in the angle of the sensor’s drive axle into a rotational movement of a diametrically magnetized magnet in the sensor.

The sensor’s electronics work contactlessly using 2D Hall elements arranged below a rotating magnetic field. The rotating magnetic field produces an electrical voltage in the live Hall semiconductors which is perpendicular to the magnetic field and the flow of current. The Hall elements are arranged geometrically so that the magnetic field rotating above them generates a sine and a cosine signal. The electronics are fully potted to protect against moisture. In their output stage, they use mathematical offsetting, processing and filtering to generate the electrical control signals which are converted into an analog, PWM, 12-bit, 150 to 2000 Hz or PSI5 output signal equivalent to the input.

The X-axis of the TF always represents the position and the Y-axis always represents the signal. This transfer function can differ depending on the customer, control unit and chassis. The transfer function is transmitted both to the front headlight beam adjuster control unit and the chassis control unit, where it is analyzed as described and used for dynamic adjustment of the respective function.

Beyond use in a vehicle, the angle sensors can also have other applications such as measuring the angle of robot arm axle bearing points, in double wishbone axles, for determining wheel travel over a linkage, for HID control and for active suspension adjustment.

Vehicle-specific sensor development and production

Level sensors are installed in many vehicle types with different chassis. This means the control arms with the sensors are not standard products; they are different for every vehicle. They also have to function in the vehicle for several years in all types of extreme ambient conditions. This demands specific environmental qualifications, robustness and technical maturity. The sensor is compact and mounted appropriately for the conditions. The mechanical and electronic parts are completely separate from one another. To protect against moisture, the electronics are appropriately sealed at the mounting point so that it remains moisture-tight over the long term. The magnet itself has an additional coating to protect against the elements.