Pedal power

A 3D sensor converts a car’s accelerator movement into an electrical signal, making the whole system
more accurate, cheaper and lighter than conventional systems.


German researchers have developed a sensor that instantly translates the movement of a car’s accelerator pedal into an electrical signal, allowing quicker, more accurate response.


Developed by engineers at the Fraunhofer Institute for Integrated Circuits (IIS) the 3D sensor, which is embedded in a silicon chip, is placed directly behind the pedal and measures the magnetic field in all three spatial directions.


Existing technology is more complicated. When an accelerator pedal is depressed, a disc moves. Several magnetic-field sensors close to the disc register the speed and convert it into an electrical signal which controls the engine and brake. This process takes time and the entire system is costly.


The new sensor allows instant conversion, making it quicker and more accurate.


Dr Hans-Peter Hohe, lead engineer at IIS said: ‘What is really new is that it is a more direct measurement of the angle. You don’t need a lot of mechanics to transfer the angle transition into a linear movement and then into a rotational movement again, and then to measure that movement with a sensor. All of these parts are no longer needed which will make the whole system more accurate, cheaper and lighter.’


The sensor measures on the basis of the Hall effect. When a conductor carries current across a magnetic field electrons are deflected to the side. This force is balanced by voltage, which can then be measured.


Hohe said that a significant advantage is that the sensor is produced using conventional, inexpensive CMOS techniques, so it can be made cheaply in large numbers and requires no special processing. ‘It is also cheaper to fabricate because it has fewer mechanical components,’ he added.


The sensor is also able to monitor itself. A small coil surrounding it is switched on periodically and the sensor measures the additional magnetic field. If the sensor is defective, no extra signal is received by the vehicle’s control system and the driver is informed of the fault.


Currently the sensor is at the prototype stage, but the IIS said it is in talks with BMW and its suppliers to produce the pedal.


The technology can also lend itself to other applications said Hohe. ‘It can be used for anything where you need to measure magnetic field accurately in three dimensions. This sensor is capable of measuring the complete magnetic field to an accuracy of 0.1 degree, so it could be used in any sensitive moving machine components,’ he said.


Further tests are planned on accelerator, brake and clutch pedals.