Interesting applications from the automotive industry
Electrification in vehicles has been increasing steadily for many years. This has also resulted in a rise in demand for sensors. These are used in comfort areas, such as for adjusting the seat position, as well in safety-critical functions, such as steering and braking.
When anti-lock braking systems (ABS) were introduced, sensors were used that served only to recognize locking of the wheels. Today, however, high-resolution wheel-speed sensors are used, which supply the electronic stability program (ESP) with data so that the vehicle can be specifically stabilized in critical driving situations through braking of the individual wheels.
Last but not least, the new market of eMobility is introducing more fields of application for sensors. Here, precise and highly dynamic current measurement is required during while driving and at charging stations.
As quantity and quality play a big role in the automotive industry, the sensors must be optimally aligned to the application. Over the past few years, Sensitec has delivered over 100 million sensors to the automotive industry – the result of optimized processes and the highest standards of quality!
The following application examples give you an insight into where our MagnetoResistive sensors are used in the automotive industry.
Wheel speed measurement (ABS) Wheel speed measurement for ABS and ESP
ABS – a small revolution in the past century: The integration of an assistance system in the vehicle, which supports drivers during full braking to the extent that the wheels no longer lock, allowing them to continue steering. The famous “Elk test” brings another function at a later stage of the development story, a function which – based on the same sensor information – allows vehicle stabilization via targeted braking of individual wheels: the ESP.
In order to make such functions a reality, the control unit requires exact data on the speed of individual wheels. The sensors that fulfill this measurement task are situated directly on the wheel hub in the immediate vicinity of the brakes, in barely protected, extremely harsh and dirty surroundings. The challenges are thus derived primarily from the environmental conditions. In addition, a reliable and durable system is require that correctly records and transmits the wheel speed.
- Customized AMR field sensor: This is packed in a compact and durable housing, along with a special signal processing unit (ASIC), by an automotive supplier.
- The sensor signals are processed directly in the ASIC and transmitted to the vehicle's control unit.
- The sensor system is mounted near the brakes and is exposed to temperatures of over 170°C for short periods of time.
- The sensor principle allows large tolerances in the working distance. This enables a very durable system design and no time-consuming adjustment during assembly.
- Non-contacting, wear-free operating principle with large working distance
- Withstands extreme environmental conditions
- High reliability proven by well over 100 million delivered units
- Automotive qualification
Torque measurement (steering) Torque detection at the steering column
“Servo” steering has been a standard feature for some time, even in the small car segment. Nowadays, steering assistance is a sophisticated complete system, which essentially functions with support from the electric motor. In the interaction between sensors, the motor and a controller, it is possible to adjust the steering assistance individually so that, for example, the assistance is reduced at high speeds. In addition to the providing steering angle information, sensors detecting the torque, which is applied to the steering shaft. With this information, the electric motor can optimally provide the required power assistance.
- Customized dual-chip AMR FreePitch sensor: This is packed in an encased sensor system, along with an equally redundantly constructed signal processing unit (ASIC), by an automotive supplier.
- The torque is determined via a differential angle measurement, i.e. the sensors measure at a shaft with a defined rigidity. The angle, and hence the torque, can be determined via the distortion between the sensors and measurement scale.
- The sensor signals of both sensors are processed redundantly and transmitted to the control unit.
- Non-contacting and wear-free operating principle
- High signal quality and high precision
- Dual chip solution for safety concept with redundancy
- High reliability and automotive qualification
Current measurement in the drive unit Wheel hub motor for future eMobility
The aim of this funding/research project was to set a milestone in the field of commercial vehicle eMobility. The shifting focus from hybrid vehicles with additional electric motor to purely electrically driven vehicles also gives rise to new drive concepts: Compact electric motors can be used locally for each wheel.
In this project, the complete drive, together with the power electronics, was integrated into the wheel hub of a commercial vehicle. To ensure the required high power density in the compact wheel hub, extremely compact yet powerful components are essential. As a result, the highly dynamic current sensor CFS1000 is used, which can be integrated directly together with the power electronics.
- Current sensor based on the AMR effect with closed-loop principle (compensation principle) for direct mounting on a PCB (SMD part).
- Electronics and drive are integrated into the wheel hub. High power density and high demands regarding thermal loads. Shocks and vibrations can also be easily managed by the compact and durable sensor.
- To achieve the best performance, the sensor is calibrated and/or synchronized with the overall system.
- Extremely compact despite high power
- Suitable for SMD assembly, even for high quantities
- Very high control quality based on the closed loop principle
- Automotive qualification
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