Adaptive method for activating a vehicle function and associated adaptive activation device

An adaptive method for activating a vehicle function using a portable device worn or carried by a user and communicating in ultra-wideband with the vehicle, the function being activated on the basis of a location of the portable device with respect to the vehicle and of authentication of the portable device, the portable device being located using the strength of a signal received by the portable device and using the time-of-flight of a signal exchanged between the portable device and the vehicle and by applying a predictive model trained beforehand using pairs of predetermined received signal strength values and predetermined time-of-flight values from a plurality of reference portable devices, the method comprising:

• a) a bijective function linking the predetermined received signal strength values and predetermined time-of-flight values used for training the model is established beforehand,
• b) for a plurality of signals received from a new portable device, if said received signals are direct signals, then:
• i) a new bijective function is established, using each new pair of values for time-of-flight and received signal strength,
• ii) a received signal strength difference representing the difference between the two bijective functions, for the same time-of-flight, is calculated,
• iii) said difference is applied to the received signal strength values of the pairs of predetermined values used for training the model,
• iv) the location of the new portable device is determined using the new pairs of received signal strength and time-of-flight values and by applying the predictive model thus modified, and
• v) the vehicle function is activated according to the location thus determined.