Patent ID: 12246677

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG.1shows a motor vehicle V, provided with a device D for detecting a predetermined movement of a user's body part, intended to trigger the opening of an opening element, specifically, in this example, the trunk of the vehicle V. Said device is included, preferably but in a non-limiting manner, in the rear bumper of the vehicle V. More particularly, said device comprises a Doppler radar, that is to say an antenna A, means for transmitting and receiving radar waves via the antenna A and means for processing the reflected radar waves in order to detect the predetermined movement.

The predetermined movement may consist of a “kick” or back and forth movement of a user's lower leg.

The processing of the radar waves reflected by the presence of the user's body makes it possible to determine whether said user has performed the predetermined movement and therefore whether they wish to open their vehicle's trunk. If the predetermined movement is detected, then the opening of the trunk is triggered; this is known to those skilled in the art and will not be further detailed here.

FIG.2shows the detection device D, which comprises an antenna A connected to transmission and reception means10, themselves connected to a control unit20. The control unit20and the transmission/reception means10are supplied with voltage Vcc, either directly or indirectly via the voltage from the battery of the vehicle V. Switching means S1allow the transmission/reception means10to be supplied with power.

According to the invention, as illustrated inFIG.3, the detection device D further comprises a directional coupler101connected to the antenna A; two demodulators connected to an output of the directional coupler, a first demodulator102suitable for delivering as output a first signal I representing the phase variations of the waves reflected and received by the antenna A, and a second demodulator103suitable for delivering as output a second signal Q representing the shifted phase variations of the waves reflected and received by the antenna A. For this, a phase shifter104is connected to the second demodulator103. The directional coupler101allows the transmission/reception means10to operate in transmission and in reception. It also makes it possible to separate the transmission signal from the reception signal, that is to say the transmitted radar wave from the received radar wave. An output of the first demodulator102and an output of the phase shifter104are connected to an input of the directional coupler101, and to an oscillator105, generating the transmission signal intended for the antenna A.

The first signal I and the second signal Q are then delivered to the control unit20which analyzes said signals. The control unit20also comprises: means M1for comparing between a predetermined threshold S and an absolute value of the maximum between the first signal I′ and the second signal Q′, means M2for exiting the standby mode and for triggering the detection mode depending on the above comparison; and means M3for opening the opening element if the predetermined movement is detected during the detection mode P1.

The comparison means M1, the means M2for exiting the standby mode and triggering the detection mode, and the means M3for opening the opening element are software means, integrated, for example, into a printed circuit of the control unit20.

The control unit20and the transmission/reception means10are suitable for switching between two modes: a detection mode P1having a high frequency of radar wave transmission, for example, a radar wave of about ten microseconds is sent every millisecond, and a standby mode P2, during which the frequency of radar wave transmission is reduced with respect to the detection mode, for example a radar wave of ten microseconds is sent every hundred milliseconds. The standby and detection modes have predetermined durations and/or settings. Once the wave has been sent, if a user is in proximity, the wave is reflected by the user's body and received by the antenna A and the transmission/reception means10. The reflected wave is then analyzed by the control unit20.

The invention proposes that when the detection device D is in standby mode, the reflected radar wave is phase-demodulated by the first demodulator102in order to produce as output the first signal I, but is also phase-shift-demodulated by the second demodulator103and the phase shifter104in order to produce the second signal Q. The first signal I and the second signal Q are then sent to the control unit20for processing according to the invention, as will be described later.

The phase shift is preferably, but in an entirely non-limiting manner, a shift by an angle with a value of 90° (or π/2) between the first signal I and the second signal Q. However, any other shift by an angle with a value of between 0° and 180° may be envisaged.

The method for opening the opening elements of the vehicle according to the invention is illustrated inFIG.5and will now be described.

In a preliminary step E0, the detection device is in a standby mode P2, which is characterized by sending radar waves at a low or reduced transmission frequency with respect to the transmission frequency used in the detection mode. Radar waves are therefore transmitted by the device to the rear of the vehicle V.

If a user is located at the rear of the vehicle and in the region of radar wave propagation, then, during step E1, a reflected wave is received by the device via the antenna A, and the transmission/reception means10, otherwise, if no reflected wave is received, then the method returns to the preceding step, and remains in the standby mode P2.

When radar waves are reflected (step E1), then the method according to the invention proposes a first, phase demodulation (step E2) of said reflected waves thus received in order to generate a first signal I representative of the phase of the waves. The first signal I is shown as a function of time on the graph illustrated inFIG.4. The first signal I is a sinusoidal signal.

The method according to the invention proposes performing a second, phase-shift demodulation of said reflected waves thus received (step E3) in order to generate a second signal Q representative of a shifted phase of the waves; more precisely, the second signal is an image of the first signal shifted in time t. Preferably, but in a completely non-limiting manner, the phase shift is a shift by an angle with a value of 90°. The second signal Q is shown as a function of time t on the graph illustrated inFIG.4; the second signal is therefore also a sinusoidal signal.

The invention then proposes, in step E4, comparing a maximum value of the absolute values of the first signal I and of the second signal Q with a predetermined threshold S. Specifically, the two signals are centered on zero. By taking their absolute value, the first signal I and the second signal Q then have only positive values.FIG.4illustrates with dashed lines the first signal I′ and the second signal Q′ in terms of absolute value for the values of the first signal I and of the second signal Q which are originally negative.

The method according to the invention then proposes comparing, at each time t, the maximum value of the signals in terms of absolute value I′, Q′ with a threshold S. If the maximum of the absolute values of the first signal I or of the second signal Q exceeds the predetermined threshold S (step E4), then the detection device comes out of the standby mode and goes into the detection mode P1, during step E5, with a higher transmission frequency, in order to detect the predetermined movement of a user's body part quickly and in time.

If the predetermined movement was detected during the detection mode (step E6), the trunk is then opened, otherwise, if no predetermined movement was detected during the detection mode P1, for example for a predetermined duration, then the method returns to step E0, and the detection device returns to standby mode P2.

The invention therefore makes it possible, during the standby mode, to quickly detect the presence of a user at the rear of the vehicle in order to engage the detection mode and to detect the predetermined movement in time in order to open the trunk.