Abstract
Abstract
Based on the successful introduction of the active sensors and magnetic encoder for wheel speed detection in the mid nineties, which has lead to a world standard for wheel speed sensing, SNR and TEVES have developed a new cost effective, contactless sensor for steering angle detection. This information is needed by different systems in cars, as for example the ESP (Electronic Stability Program). As TEVES is a major player in the ESP-market and SNR is the inventor of the ASB® (Active Sensor Bearing), both companies joined their forces in order to bring to market this new steering angle sensor. The basic idea was to improve the reliability of the sensor itself by reducing the complexity of the sensor electronics and using the existing intelligence in the car, as for example the ECU of the ESP system. Furthermore a lot of information about the behaviour of the car is already available in the car network, this can be used to get the redundancy for the sensor signals. Today there are three different classes of position sensors:
Class 1: Incremental sensor, providing direction and angle speed information
Class 2: Absolute position over ± 180°
Class 3: Absolute position over ± 720° or more
ASB® Steering Technology
In today’s ESP systems a class 3 sensor is typically used. This sensor is a stand alone solution, which can work without any information from outside. The ASB® Steering concept can provide class 3 performance by combining the sensor signals with other signals available in the ESP-ECU. The sensor delivers two incremental signals, 90° phase shifted for direction, relative angle position and angle speed to the ECU. The third output of the sensor delivers an index signal corresponding to a binary word, which is magnetized on the second track of the magnetic encoder. Out of these three sensor signals a class II sensor is built. By taking information from differential wheel speed, which is available in the ESP-ECU, the required absolute multi-turn angle information is calculated and put on the CAN for other car systems requiring this information. For redundancy purposes the ASB® Steering software module compares the angle value with information from the sensor cluster of the Continental Teves ESP system. This sensor concept can be used anywhere on the steering column, as the applied magnetic technology works also in harsh environment, like in wheel speed sensor, where high temperatures and salt, water and mud attack the magnetic encoder and the sensor.