Operation and Features of Smart Keys
– Smart key allows driver to unlock, lock, and start vehicle without using key fob
– Vehicle is automatically unlocked when button or sensor on door handle or trunk release is pressed
– Mechanical backup key blade is provided with the vehicle
– Vehicle can be started without inserting key in ignition by pressing starter button or twisting ignition switch
– Vehicle is locked by pressing button on door handle, touching capacitive area on door handle, or walking away from vehicle
– SmartKeys developed by Siemens in mid-1990s and introduced by Mercedes-Benz in 1997
– Plastic key with electronics replaces traditional metal key
– SmartKey fob incorporates remote control buttons from keyless entry
– SmartKey is placed in ignition slot for verification by starter computer
– Mercedes-Benz integrates Keyless Go as an option, allowing driver to open doors, trunk, and start car without removing SmartKey from pocket
– Display Key is a smart key developed by BMW with LCD color touchscreen
– Performs standard functions of locking, unlocking, and keyless start
– User can perform additional features from BMW app, including commanding car to self park
– Key is rechargeable and lasts about 3 weeks
– Can be charged via micro USB port or wirelessly on center console
– Keyless Go is Mercedes term for technology that allows driver to lock and unlock vehicle without using SmartKey buttons
– Driver can start and stop engine without inserting SmartKey
– Transponder within SmartKey identifies driver
– Safety feature prevents locking SmartKey with Keyless Go inside vehicle
– System uses LF transmitting antennas inside and outside vehicle to communicate with key and unlock vehicle
Insurance Standards and Theft Rates
– UK motor insurance research expert Thatcham introduced standard for keyless entry in 2005
– Device must be inoperable at a distance of more than 10cm from the vehicle
– Certain BMW and Mercedes keys failed security test, allowing cars to be driven away while owners were refueling
– Auto theft rates decreased 7% between 2009 and 2010, credited to smart keys
– National Insurance Crime Bureau recognizes smart keys for decrease in theft rates
Internal LF Field Dead Spots
– Dead spots are a result of the maximum overshoot requirement from above.
– Power delivered to the internal LF antennas must be tuned for optimal performance.
– Dead spots are usually near the extremities of the vehicle, such as the rear parcel shelf.
Battery Backup and Special Cases
– Depleted smart key battery requires a backup method for opening and starting the vehicle.
– Emergency key blade is hidden in the smart key for mechanical opening.
– Inductive coupling allows emergency starting by placing or holding the key near a special area on the cockpit.
– Slots can go wrong and lock the key in, unable to be removed.
– Fob battery below a certain threshold can’t be compensated by the slot.
– Keyless Entry / Go system should handle cases like forgetting the smart key in the rear trunk.
– The system should detect and handle multiple smart keys present inside the car.
– Smart key getting lost during the drive should be accounted for.
– Limp-Home mode should be activated when the smart key battery is low.
History and Outlook
– The first Keyless Entry / Go ECU was introduced in the MB S-Class car series in 1998/99.
– The system is based on Siemens VDO’s PASE technology operating in the ISM band.
– Mercedes-Benz was the first to introduce Keyless Entry / Go in 1998.
– Keyless Entry / Go systems have potential for optimization.
– Reduction of LF antennas in low-cost compact cars may result in a loss of detection quality.
– Electric field antennas can be used instead of magnetic field antennas to reduce costs.
– Microwave frequencies (radar) can be used instead of LF and RF combination for more comfort.
– Biometric authentication could identify the user instead of the SmartKey transponder.Sources: https://en.wikipedia.org/wiki/Smart_key
