Looking at the automotive industry today, we are facing a revolutionary change driven by autonomous driving and vehicle electrification efforts. Both of these lead to greater demand for more accurate, reliable and robust sensors; and position sensors play a central role here. While the industry is continuously called upon to design more and more sophisticated vehicles, there is always the challenge to keep costs affordable in a very competitive globalized market. Traditional position sensor technologies, including magnetic approaches, are well-established and have been sufficient for many standard applications. Why does the inductive technology represent a new era in position sensing?
To address this question, let’s take a quick look at the market changes and new needs. The electrification trend is a game-changer that further necessitates immunity to external stray fields in order to guarantee higher safety standards, even in the presence of strong magnetic fields generated, for example, by propulsion motors or high currents flowing through wires. The ISO11452-8 standard, which specifies tests for the electromagnetic immunity of electronic components for passenger cars and commercial vehicles, regardless of the propulsion system (e.g. spark-ignition engine, diesel engine, electric motor), pushes the industry to add the stray field specification when defining a component. Magnetic position sensors work with a DC magnetic field and are seriously vulnerable to external stray fields. Inductive sensor technology, however, generates an AC field in a specific frequency band that can guarantee much higher immunity levels. Today, OEMs specify up to 4000 A/m, which simply cannot be met by conventional magnetic position sensing technologies.
During a recent customer meeting this point came across to me very clearly. OEMs intend to move away from magnetic solutions, above all, for safety-critical applications.
An intrinsic aspect of magnetic technology is represented by the need of magnets to generate a strong field. The major compounds of these magnets are rare earth elements like neodymium. As with all earth elements, prices are volatile. Additionally, when looking at the total bill of materials, the magnet cost can represent up to 50% of the overall system cost, particularly for complex side-shaft or thru-shaft system setups. To address these problems, inductive position sensor technology works with just a thin piece of metal, which serves not only to reduce system costs and volatility, but also allows the solution to become extremely thin.
Inductive Position Sensor Motion Examples
In IDT’s inductive technology, the sensing element is a set of coils designed directly on the PCB. A major advantage to this approach is the ability to design the sensing element around the customer application without a loss of resolution or accuracy. This represents a huge advantage for rotary applications with small arc excursions (e.g. <30 degrees). For example, a 10-bit inductive sensor working on a 22.5° mechanical rotation is equivalent to a magnetic solution with a 14-bit resolution. Common design use cases include rotary position sensors (angular position sensor), linear position sensors, and small arc angle rotation position sensors.
Inductive position sensing technology is paving new roads in the automotive industry and IDT’s ZMID520x family of devices creates value by increasing robustness via stray field immunity, improving accuracy, and reducing overall system costs. For more details including app notes, design tools and evaluation kits, visit idt.com/position.