****

TEXT OF THE DESCRIPTION

Field of the invention

The present invention relates to motor-vehicles with headlight units provided with a system for regulating the emission direction. In particular, the invention relates to motor-vehicles of the type wherein each headlight unit includes an electric actuator for regulating the inclination of the light beam emitted by the headlight unit, and an electronic control unit associated with the headlight unit and configured to receive a command signal and to activate the aforesaid electric actuator so as to adjust the emission direction of the headlight unit according to said command signal.

Prior art

Systems for automatic adjustment of the emission direction of the headlight units of a motor-vehicle have been proposed and used for some time. Examples of such systems are, for example, described in US 7599779 B2, US 10001361 B2, WO 2018/065692 A1, EP 3527453 A1, WO 2019/180331 A1, DE 10 2015 208795 B4, EP 2708417 B1, US 10471884 B2, EP 3 3527453 B1, EP 3689680 A1, WO 2018/091529 A1, DE 2020 19100544 U1, EP 3106346 A1, US 10676016 B2, EP 2963385 A1

The solutions according to the prior art are all relatively complex and expensive. Instead, the need is felt for a solution that is functional and reliable, but - at the same time - simple and economical. This need has become a priority due to the fact that the introduction of regulations is currently envisaged, which make the presence of automatic adjustment systems of the type indicated above mandatory on-board the motorvehicle. In this situation, it has become imperative to provide an automatic adjustment system not only in high class cars, but also in smaller category motor-vehicles, to be produced in large series, with the need, therefore, to contain production costs as much as possible and to simplify the assembly operations. The Applicant has proposed a solution to the aforesaid problem in the European patent application EP 21210029.1 dated 23.11 .2021 , not yet published at the filing date of the present application. However, there is a need for further improvement in this field.

Object of the invention

An object of the present invention therefore constitutes that of producing a motor-vehicle equipped with an adjustment system of the type indicated above which is considerably simpler and more economical than known systems, and which is nonetheless functional and reliable.

A further object of the invention is to provide a system for automatic adjustment of the emission direction of a motor-vehicle headlight unit that is light and not bulky.

A further object of the invention is to provide a system of the type indicated above, which involves the use of a reduced number of components.

Summary of the invention

With a view to achieving one or more of the aforesaid objects, the motor-vehicle according to the invention relates to a motor-vehicle of the type indicated at the beginning of the present description, further comprising:

- a main electronic control unit of the motor-vehicle, and

- a system of one or more motor-vehicle airbags, including an electronic airbag control unit said motor-vehicle being characterized in that:

- the main control unit of the motor-vehicle is configured for:

- calculating the value of a variation (DeltaPitch) in the pitch angle of the motor-vehicle, defined as the variation of the inclination of the longitudinal axis of the motor-vehicle with respect to the road, during the operation of the vehicle, only when the vehicle speed falls below a threshold value (SpeedLim), which is not higher than 0.1 km/h, and exclusively on the basis of the value of the longitudinal acceleration (Long) of the vehicle, and

- generating said command signal for the control unit of the headlight unit on the basis of said calculated value of the variation (DeltaPitch) in the pitch angle of the motor-vehicle with respect to the road,

- wherein the main control unit of the motor-vehicle is configured to obtain some information on said longitudinal acceleration value (Long) of the motor-vehicle from the airbag control unit, and also wherein:

- the main control unit is configured to perform said calculation of the value of the variation (DeltaPitch) of the vehicle pitch angle with respect to the road each time the vehicle speed falls below said threshold value (SpeedLim), through the following operations: a) calculating and storing, each time the vehicle speed falls below the threshold value (SpeedLim), the value of the motor-vehicle pitch angle with respect to a horizontal plane (PitchAngle) on the basis of the following equation: where:

(PitchAngle deg is the pitch angle expressed in degrees, with respect to a horizontal plane,

Longp is a filtered value of the longitudinal acceleration of the motor-vehicle obtained from the airbag control unit of the motor-vehicle, and “g” is the acceleration due to gravity, b) calculating the variation of the motor-vehicle pitch angle with respect to the road (DeltaPitch) on the basis of the following equation:

DeltaPitch = PitchAngle - OffsetCal - OffsetDyn where:

PitchAngle is the calculated value of the pitch angle of the vehicle with respect to a horizontal plane (PitchAngle),

OffsetCal is a calibration value indicative of the pitch angle value with respect to a horizontal plane (PitchAngle) in an initial calibration condition of the motor-vehicle, and

OffsetDyn is an offset value indicative of the slope of the road, which is calculated each time the vehicle speed falls below the threshold value (SpeedLim) as the difference between the current PitchAngle value and a last previously calculated and stored value of the PitchAngle.

As can be seen, in the motor-vehicle according to the invention, the emission direction of a headlight unit is controlled on the basis of a calculation in the variation of the pitch angle of the motor-vehicle with respect to the road. The calculation is performed only in stationary or nearly stationary conditions, when the vehicle speed drops below a threshold value not exceeding 0.1 km/h, so that the calculation itself can be performed solely on the basis of the value of the longitudinal acceleration (Long) of the motor-vehicle. Furthermore, the information on the value of the longitudinal acceleration (Long) of the motor-vehicle is supplied by the airbag control unit.

Thanks to the aforesaid characteristics, in the motor-vehicle according to the invention, the control of the emission direction of the headlight unit may be obtained without the need to provide a control unit dedicated to this function on the motor-vehicle, and without providing dedicated sensors for detecting the longitudinal acceleration of the motorvehicle and the slope angle of the road. The information on the longitudinal acceleration is obtained via the airbag control unit, which the vehicle is in any case equipped with. The information on the slope of the road is obtained as the difference between the calculated values of the pitch angle with respect to the horizontal plane (PitchAngle) in two stationary or nearly stationary conditions of the motor-vehicle at the beginning and at the end of a journey, respectively.

Preferably, the main control unit is configured to calculate the variation in the pitch angle of the motor-vehicle with respect to the road after a predetermined delay with respect to when the speed of the vehicle drops below the threshold value, to allow the pitching oscillations of the motor-vehicle to stop.

Preferably, the main control unit is configured to obtain said filtered value (Long _F ) of the longitudinal acceleration of the motor-vehicle with an iterative calculation based on the following equation: Long _F [N ■ T] = a ■ Long _F [(N — 1) ■ T] + (1 — a) ■ Long [N ■ T] where a is a filtering parameter, in the range of 0.75-1.00,

N is the iteration number and T is the sampling time of the longitudinal acceleration value (Long) detected by the airbag control unit.

Still according to a preferred characteristic, the main control unit is configured to generate a command signal, which contains a percentage value indicative of the adjustment position of the light beam, said percentage value being determined on the basis of a table that assigns different percentage values to different ranges of the value of the variation in the pitch angle of the motor-vehicle with respect to the road (DeltaPitch), each percentage value corresponding to a respective range of values of the variation of the motor-vehicle pitch angle with respect to the road (DeltaPitch).

Again with reference to the preferred embodiment, the main control unit is configured to implement a state machine strategy, comprising:

- a START-UP state, which is activated at the motor-vehicle key-on,

- an IDLE state, which is activated when the vehicle speed exceeds the aforesaid threshold value (SpeedLim), wherein the main control unit maintains the last adjusted position of the headlight unit (2),

- an EXE state, which is activated when the vehicle speed falls below said threshold value (SpeedLim), wherein the main control unit generates the aforesaid command signal (S) on the basis of the calculation of the pitch angle variation of the motor-vehicle with respect to the road (DeltaPitch), and stores the resulting adjustment position (POSIast) of the headlight unit and the last calculated value of the pitch angle of the motor-vehicle with respect to a horizontal plane (PitchLast), and

- a FAULT state, which is activated when a fault condition is present, wherein the main control unit adjusts the position of the headlight unit to the value corresponding to the greater downward inclination of the emission direction, chosen between a default safety value (POSfault) and the value corresponding to the last adjustment position (POSIast) of the headlight unit, and stores this chosen value as the last adjusted position. The invention also relates to the control method implemented in the motor-vehicle according to the invention.

Detailed description of a preferred embodiment

Further characteristics and advantages of the invention will become apparent from the description that follows with reference to the attached drawings, provided purely by way of non-limiting example, wherein:

- Figure 1 is a schematic side view of a motor-vehicle equipped with the system according to the invention,

- Figure 2 is a block diagram of the system according to the invention, and

- Figure 3 is a block diagram of the state machine strategy implemented by the system according to the invention.

In the drawings, numeral 1 indicates - in its entirety - a motorvehicle of any type comprising two front headlight units (only one of which is shown schematically) with which the adjustment system according to the invention is associated. Figure 1 shows a reference system X, Y, Z, wherein the X axis coincides with the longitudinal axis of the motor-vehicle, the Y axis is a horizontal axis orthogonal to the X axis, and the Z axis is the axis orthogonal to the plane of the road 6.

Each headlight unit is equipped with an adjustment device of any known type, which allows the angle [3 formed by the axis of the emitted light beam to be adjusted. For this reason, the construction details of this device are neither described nor illustrated, both because, taken by themselves, they do not fall within the scope of the present invention, and for the object of simplifying the drawings.

For the purposes of the present description, it should simply be noted that the adjustment device of which the headlight unit 2 comprises an electric actuator 3 (typically an electric motor) intended to control the adjustment of the emission direction of the light beam and an electronic control unit 4 (which can be integrated in the actuator 3), forming part of the headlight unit 2, intended to operate the electric motor 3 according to a command signal sent to it by the adjustment system with which the motorvehicle is provided. The electronic control unit 4 forming part of the headlight unit 2 is also illustrated in Figure 2. This figure shows - as a whole - the adjustment system 5, with which the motor-vehicle 1 is provided, intended to send a command signal S to the control unit 4 of the headlight unit 2, on which the adjustment of the beam emitted by the headlight unit depends.

In the system according to the invention, the signal S is generated by the main electronic control unit E of the motor-vehicle.

As will appear in detail below, the main control unit E of the motorvehicle generates the command signal S following a calculation of the variation in the pitch angle of the motor-vehicle with respect to the road 6. The calculation is performed only in static or nearly-static conditions, when the vehicle speed falls below a threshold value not exceeding 0.5 km/h. Consequently, the calculation may be performed solely on the basis of the value of the longitudinal acceleration (Long) of the motor-vehicle 1 (i.e. the acceleration in the X direction).

In the motor-vehicle according to the invention, the main control unit E receives information on the value (“Long”) of the longitudinal acceleration from the electronic control unit E1 arranged on the motorvehicle for controlling the airbags mounted on-board the motor-vehicle.

The airbag system of the motor-vehicle is neither described nor illustrated here, since it can be of any known type including an electronic control unit E1 that has the information relating to the longitudinal acceleration of the motor-vehicle.

In the preferred embodiment of the invention, the electronic control unit E is configured to obtain a filtered value (Long _F ) of the longitudinal acceleration of the motor-vehicle with an iterative calculation based on the following equation:

Long _F [N ■ T] = a ■ Long _F [(N — 1) ■ T] + (1 — a) ■ Long [N ■ T] where a is a filtering parameter, in the range of 0.75-1.00,

N is the iteration number and T is the sampling time of the longitudinal acceleration value (Long) detected by the airbag control unit.

As indicated, the main control unit E is configured to perform the calculation of the variation in the pitch angle (“Pitch" in Figure 1 , i.e. the rotation angle around the transversal axis Y) with respect to the road 6, during motor-vehicle operation, only when the vehicle speed falls below a threshold value (“ SpeedLim").

In accordance with the conventional art, the main control unit E of the motor-vehicle uses the information on the speed of the vehicle in any known way, typically on the basis of a signal from a sensor of any known type associated with the motor-vehicle.

Every time the main control unit E detects that the vehicle speed has dropped below the threshold value SpeedLim, it starts calculating the variation value (DeltaPitch) of the pitch angle of the motor-vehicle with respect to the road.

This calculation is performed in two steps, which will be described in detail below. In a first step, the pitch angle value of the motor-vehicle is calculated with respect to a horizontal plane (PitchAngle). In a second step, the variation in the pitch angle of the motor-vehicle with respect to the road (DeltaPitch) is calculated by subtracting from the calculated PitchAngle value a calibration offset (indicative of the PitchAngle value in an initial calibration condition of the vehicle) and a dynamic offset (OffsetDyn), indicative of the slope of the road, calculated in the way which will also be illustrated hereafter.

In the aforesaid first step of the calculation, the main control unit E calculates the value of the pitch angle of the motor-vehicle with respect to a horizontal plane (PitchAngle) on the basis of the following equation: where:

(PitchAngle)de<3 is the pitch angle expressed in degrees, with respect to a horizontal plane,

Longp is a filtered value of the longitudinal acceleration of the motor-vehicle obtained from the airbag control unit (E1 ) of the motorvehicle, and “g” is the acceleration due to gravity,

In the aforesaid second step of the calculation, the main control unit E calculates the variation in the pitch angle of the motor-vehicle with respect to the road (DeltaPitch) on the basis of the following equation:

DeltaPitch = PitchAngle - OffsetCal - OffsetDyn where:

PitchAngle is the calculated value of the pitch angle of the motorvehicle with respect to a horizontal plane (PitchAngle),

OffsetCal is a calibration value indicative of the pitch angle value with respect to a horizontal plane (PitchAngle) in an initial calibration condition of the motor-vehicle, and

OffsetDyn is an offset value indicative of the slope of the road, which is calculated each time the vehicle speed falls below the threshold value (SpeedLim) as the difference between the current PitchAngle value and a last previously calculated and stored value of the PitchAngle.

The calibration value OffsetCal is:

OffsetCal = PitchAngleCalibration where PitchAngleCalibration is the PitchAngle value, which is calculated in a system calibration step when the system is first installed in the motorvehicle, and each time maintenance has been performed on the main control unit E and/or on the headlight.

In an example, the calibration process is performed under the following conditions:

- the vehicle is parked on a flat surface,

- the light beam of the headlight is adjusted mechanically according to current legislation,

- care is taken to avoid any vibration of the system during the calibration process,

- the pitch angle value is determined (PitchAngleCalibration), and this angle is used as an offset.

The algorithm that performs the calibration process is as follows:

- a time equal to Delay _W ait is expected, in order not to take into account unreliable longitudinal acceleration values due to the transient on the CAN network immediately after key-on,

- for a time equal to Delay _S hort, the longitudinal acceleration value obtained from the control unit E1 is read and the filtering strategy is applied,

- the pitch angle is calculated with the above equation,

- the calculated value is assumed as “OffsetCaf’

- the “ OffsetCal" value is stored in the non-volatile memory of the control unit E.

As indicated above, the value OffsetDyn is an offset value indicative of the slope of the road, which is calculated each time the vehicle speed falls below the threshold value (SpeedLim), as the difference between the current PitchAngle value and a last previously calculated and stored value of the PitchAngle. In other words, every time the vehicle returns to a stationary or nearly stationary condition (speed below the threshold value) after traveling at a speed higher than the threshold value, the PitchAngle with respect to the horizontal plane is calculated, and the slope of the road (OffsetDyn) is increased by a value equal to the difference between the new calculated PitchAngle value (with respect to the horizontal plane) and the last previously stored PitchAngle value. This approach is justified as it is assumed that during the journey there has been no variation in the load condition of the vehicle.

In practice, the OffsetDyn value is set equal to zero every time a calibration procedure is performed, after which every time the vehicle speed drops below the SpeedLim threshold value, the OffsetDyn value is updated by applying the following equation:

OffsetDyn = OffsetDyn + DeltaPitchcheck where DeltaPitchcheck is a value calculated by using the following equation

DeltaPitchcheck = PitchAngle - Pitchlast where PitchAngle is the value of the pitch angle with respect to the horizontal plane calculated in the new condition of the vehicle, while Pitchlast is the last previously stored value of the PitchAngle.

To avoid excessive deterioration of the calculated OffsetDyn value, this value is reset to zero when both of the following conditions occur: A1 ) \PitchAngle - OffsetCal\ < THRi

A2) OffsetDyn > THRi or OffsetDyn <THR ₂ where

THRi and THR2 are predetermined threshold values, which are determined empirically.

Preferably, the main control unit is configured to calculate the variation in the pitch angle of the motor-vehicle with respect to the road (DeltaPitch) after a predetermined delay with respect to when the speed of the vehicle drops below the threshold value, to allow the pitching oscillations of the motor-vehicle to stop.

The calculated angular pitch angle variation (DeltaPitch) is converted into a percentage value representing the adjustment position of the headlight unit.

Preferably, in the system according to the invention, the main control unit is configured to generate a command signal S, which contains a percentage value indicative of the adjustment position of the light beam of the headlight unit, said percentage value being determined on the basis of a table that assigns different percentage values to different ranges of the angular difference DeltaPitch, each percentage value corresponding to the respective range of DeltaPitch values.

For example, a conversion table like this can be used:

If the calculated DeltaPitch is very close to the threshold value between two lines of the conversion table, the adjustment of the headlight unit may be unstable, as disturbing oscillations of the longitudinal acceleration value may lead to small oscillations of the DeltaPitch. To overcome this drawback, intermediate bands (“grey zones”) are preferably provided between every two lines of the conversion table indicated above. When found in one of these zones, the adjustment of the headlight unit is inhibited, until the calculated DeltaPitch value is outside the grey zone.

The main control unit E is configured to implement a state machine strategy comprising:

- a START-UP state, which is activated at the motor-vehicle key-on,

- an IDLE state, which is activated when the vehicle speed exceeds aforesaid threshold value (SpeedLim), wherein the main control unit maintains the last adjusted position of the headlight unit 2,

- an EXE state, which is activated when the vehicle speed falls below said threshold value (SpeedLim), wherein the main control unit (E) generates the aforesaid command signal (S) on the basis of the calculation of the pitch angle variation of the motor-vehicle with respect to the road (DeltaPitch), and stores the resulting adjustment position (POSIast) of the headlight unit 2 and the last calculated value of the pitch angle of the motor-vehicle with respect to a horizontal plane (PitchLast), and

- a FAULT state, which is activated when a fault condition is present, wherein the main control unit adjusts the position of the headlight unit 2 to the value corresponding to the greater downward inclination of the emission direction, chosen between a default safety value (POSfault) and a value corresponding to the last adjustment position (POSIast) of the headlight unit, and stores this chosen value as the last adjusted position.

A block diagram of the state machine is shown in Figure 3.

With reference to this figure, during the START-UP state, the system performs the following operations:

- in the first cycle of START-UP operations after KEY-ON, a predetermined Delaywait time is waited for, ignoring all CAN data, after which, for a time equal to Delayshort, filtering is detected and applied to the variable longitudinal acceleration communicated by the airbag control unit E1 ,

- once after each Key-on, the calculated PitchAngle value is compared with the stored PitchLast value. If the module of the difference is greater than a threshold PitchTHR, the OffsetDyn value, indicative of the slope of the road, is updated accordingly. This checks that the gradient of the road has not changed when the car is off (this can happen if the car is towed).

- the cycle of calculations is applied that have been described above to calculate the DeltaPitch with respect to the road,

- the conversion from DeltaPitch to adjustment percentage is applied using the conversion table,

- a DelayWait time is waited before proceeding further, after which the adjustment position of the headlight unit 2 thus obtained is stored as the last calculated position (POSIast), and the last calculated PitchAngle value with respect to the horizontal plane is stored as Pitchlast,

- by means of the main control unit E, a command signal S is sent to the headlight control unit 4, to adjust the emission direction of the headlight in the POSIast position.

During the IDLE state, i.e. when the motor-vehicle moves at a speed higher than the SpeedLim threshold value, the headlight unit 2 is left in the adjustment position POSIast.

During the EXE state, the system performs the following operations:

- in the first cycle of operations in EXE mode, a predetermined DelayLong time is waited, after which for a time equal to DelayShort, filtering is detected and applied to the longitudinal acceleration variable communicated by the airbag control unit E1 ,

- once in the first cycle of operations in the EXE state, the calculated value of PitchAngle is compared with the stored PitchLast value. If the modulus of the difference is greater than a threshold, the OffsetDyn value is updated accordingly, to take into account variations in the load on the vehicle that occurred, for example, when the system was in a FAULT state, - the cycle of calculations is applied that have been described above to calculate the DeltaPitch with respect to the road,

- the conversion from DeltaPitch to adjustment percentage is applied using the conversion table,

- a DelayWait time is waited before proceeding further, after which the adjustment position of the headlight unit 2 resulting from the conversion is stored as the last calculated position (POSIast) and the last calculated PitchAngle value with respect to the horizontal plane is stored as Pitchlast,

- by means of the main control unit E, a command signal S is sent to the headlight control unit 4, to adjust the emission direction of the headlight in the position POSIast.

- finally, the OffsetDyn value is reset to zero if the double condition (A1 , A2) - defined above - occurs.

During the FAULT state, wherein the system enters in the event of any failure, the system itself performs the following operations:

- the minimum adjustment position is determined (i.e. corresponding to an emission direction of the headlight unit 2 more inclined downwards) between a predetermined value POSfault and the last previously stored adjustment position POSIast,

- this minimum adjustment position is stored as POSIast, and

- by means of the main control unit E, a command signal S is sent to the headlight control unit 4, to adjust the emission direction of the headlight in the POSIast position thus stored.

In the system according to the invention, the conditions for a state change are controlled in real time and the state change has priority over any further operation. If the need for a state change occurs, and operations running in the current state are still in progress, those operations are aborted.

In one example, typical values for the parameters discussed above are as follows: a: 0.99 speed threshold value (SpeedLim): 0.1 km/h

DelayLong: 2 sec

DelayShort: 1 sec’ DelayWait: 1 sec’

THR1 . 0.2 degrees

THR2: 1.6 degrees

Delta: 0.04 degrees

With reference again to Figure 3, in this example, when the engine is started, the system is in the START-UP state. When the vehicle speed exceeds the threshold value (for example 0.1 km/h), the system switches to the IDLE state. From the IDLE state, the system switches to the EXE state when the speed drops below the threshold value and returns to the IDLE state when the speed exceeds the threshold value. In the START-UP state, as well as in the IDLE state and in the EXE state, if a failure occurs, the system switches to the FAULT state. When the fault is no longer present, the system returns from the FAULT state to the IDLE state.

As is evident from the preceding description, the system according to the invention makes it possible to obtain an automatic adjustment of the headlight unit with extremely simple means, exploiting the on-board systems of the vehicle, without requiring a dedicated controller or dedicated sensors.

Of course, without prejudice to the principle of the invention, the embodiments and construction details may widely vary with respect to those described and illustrated purely by way of example, without thereby departing from the scope of the present invention, as defined in the attached claims.