Abstract:
The lighting and/or signaling system according to the invention comprises at least one lighting and/or signaling device which is able to emit at least one light beam and is equipped with at least one actuator for adjusting an angle of the light beam, and at least one actuator control device for controlling the actuator. According to the invention, the actuator control device transmits an active setpoint information item to the actuator only when a current value of the setpoint information item differs substantially from a previous value of the setpoint information item. The improved actuator control incorporated in the system according to the invention helps to achieve greater reliability and a longer service life.

Description:
FIELD OF INVENTION 
       [0001]    The invention relates in general to the field of lighting/signaling systems for vehicles, in particular motor vehicles. More particularly, the invention relates to a lighting and/or signaling system for a vehicle, comprising at least one lighting and/or signaling device which is able to emit a light beam and is equipped with at least one actuator for adjusting an angle of the light beam, and at least one actuator control device. 
       BACKGROUND OF THE INVENTION 
       [0002]    The invention finds application in particular, but not exclusively, in lighting and/or signaling systems which include actuators provided for adjusting the tilt angle of the headlamps as a function of attitude variations of the vehicle. 
         [0003]    Actuators  1 D and  1 G of the type mentioned above are shown schematically in  FIG. 1A  which shows a first type of actuator control device according to the known prior art of the inventive entity. The device shown in  FIG. 1A  is designed for manual correction of the tilt angle of the headlamps, by means of a potentiometer which is accessible to the driver of the vehicle. 
         [0004]    The actuators  1 D and  1 G respectively equip the right and left headlamps of the motor vehicle. 
         [0005]    As shown in  FIG. 1A , the actuator  1 D,  1 G comprises a DC motor  10 , a motion conversion mechanism  11  and a motor control circuit  12 . 
         [0006]    The motion conversion mechanism  11  is for example of the wheel/worm or wheel/rack type. The rotation of the motor  10  gives rise to a linear movement of a control rod  110  which is mechanically coupled to the headlamp, so as to adjust the tilt angle of the latter. 
         [0007]    In this type of device, the position of the rod is determined by the value of a DC setpoint voltage Vc which is applied to an input of the motor control circuit  12 . The setpoint voltage Vc is processed by the motor control circuit  12  so as to shape a drive signal adapted to the motor. 
         [0008]    The control voltage Vc is obtained by means of an adjustment potentiometer  2  which is supplied by a DC voltage Vcode. In a conventional manner, the DC voltage Vcode is present when the lighting control stalk switch is positioned at “low beam” or “full beam” by the driver of the vehicle. The voltage Vcode is also used as a supply voltage for the actuators  1 D and  1 G. 
         [0009]    In this first type of actuator control device according to the prior art, the setpoint voltage Vc is applied to the actuators  1 D,  1 G for the entire duration that the headlamps are set to “low beam” or “full beam”, and its value is taken into account throughout this duration for controlling the actuators  1 D,  1 G. This means that fluctuations in the setpoint voltage Vc, due for example to parasitic electrical or electromagnetic signals, are continuously passed to the actuators  1 D,  1 G and give rise to undesirable displacements thereof. 
         [0010]    These undesirable displacements of the actuators have negative repercussions on the service life thereof and may lead to tilt angle settings which do not comply with the regulations. 
         [0011]    A second type of actuator control device according to the known prior art of the inventive entity is shown in  FIG. 1B . The device shown is designed for automatic correction of the tilt angle of the headlamps. 
         [0012]    In this second type of device, the actuators  1 D and  1 G are no longer controlled by a DC setpoint voltage but rather by a pulse control signal Vc pwm  of the pulse width modulation type. The control signal Vc pwm  is processed by a motor control circuit  12 ′ which is able to shape a drive signal adapted to the motor. As in the device of  FIG. 1A , the actuators  1 D and  1 G are supplied by the DC voltage Vcode. 
         [0013]    In the device of  FIG. 1B , the control signal Vc pwm  is produced by a correction control circuit  3  on the basis of front  4 AV and rear  4 AR attitude sensors which are coupled for example to the axles of the vehicle. The correction control circuit  3  is supplied by the DC voltage Vcode. 
         [0014]    On account of the pulse width modulation of the control signal Vc pwm , this second type of device provides better resistance to electrical and electromagnetic parasites compared to the device of  FIG. 1A . However, such a technical solution still does not make it possible to satisfy the increased requirements in terms of reliability and service life which apply to headlamps in the motor vehicle sector. 
       SUMMARY OF THE INVENTION 
       [0015]    The present invention aims to overcome the aforementioned disadvantages of the prior art by providing a lighting and/or signaling system for a vehicle which incorporates improved actuator control designed for greater reliability and an increased service life. 
         [0016]    The lighting and/or signaling system for a vehicle, in particular a motor vehicle, according to the invention comprises at least one lighting and/or signaling device which is able to emit at least one light beam and is equipped with at least one actuator for adjusting an angle of the light beam, and at least one actuator control device for controlling the actuator. According to the invention, the actuator control device comprises control means which are able to transmit an active setpoint information item to the actuator only when a current value of the setpoint information item differs substantially from a previous value of the setpoint information item. 
         [0017]    According to another particular feature of the invention, the actuator control device also comprises switching means which are able to interrupt an electrical power supply to the actuator when no active setpoint information item is transmitted to the actuator by the control means. 
         [0018]    Preferably, the switching means comprise a controllable switch. According to one particular embodiment, this controllable switch makes use of a transistor of the MOS type. According to another particular embodiment, this controllable switch makes use of a switch circuit of the SmartMOS type. 
         [0019]    According to yet another particular feature, the control means comprise memory means for storing the previous value of the setpoint information item, and comparison means for comparing the current and previous values of the setpoint information item and ordering the transmission of the active setpoint information item to the actuator when a difference is detected between the current and previous values. Preferably, the comparison means are able to order the transmission of the active setpoint information item to the actuator when the detected difference is above a predetermined threshold. 
         [0020]    According to one particular embodiment, the actuator control device is embodied at least partially by means of operational amplifiers. 
         [0021]    According to another particular embodiment, the actuator control device is integrated at least partially in a controller of the system. Preferably, the actuator control device is implemented in the controller at least partially by means of program instructions. 
         [0022]    According to one particular embodiment of the invention, the actuator comprises a DC motor. 
         [0023]    Other aspects and advantages of the present invention will emerge more clearly from reading the following description of particular embodiments, this description being given by way of non-limiting example and with reference to the appended drawings, in which: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]      FIG. 1A  shows a first type of actuator control according to the prior art; 
           [0025]      FIG. 1B  shows a second type of actuator control according to the prior art; 
           [0026]      FIG. 2  schematically shows the actuator control means included in a lighting and/or signaling system according to the invention; and 
           [0027]      FIG. 3  is an algorithm showing the mode of operation of the actuator control means of  FIG. 2 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0028]    The invention will now be described essentially within the context of one particular embodiment of a system according to the invention in which actuators which are coupled to the headlamps are provided for adjusting the tilt angle of said headlamps. 
         [0029]    As shown in  FIG. 2 , the actuator control device according to the invention, which is denoted as a whole by reference  5 , is connected to the actuators  1 D and  1 G of the headlamps (not shown) and receives at the input a setpoint information item CD. 
         [0030]    As will emerge more clearly below, the setpoint information item CD supplied to the actuator control device according to the invention may be in different forms, for example in the form of a DC voltage with a level which is representative of the setpoint information item CD, a pulse width modulated (PWM) signal, a digital data item or the like. 
         [0031]    In this embodiment, the actuators  1 D and  1 G are analogous to those described above with reference to  FIGS. 1A and 1B , and thus will not be described again in detail here. 
         [0032]    However, it will be noted that the invention applies both to actuators with direct control of the motor and to actuators with slaved control of the motor. 
         [0033]    Moreover, the actuators  1 D and  1 G each comprise a motor control circuit  12 ″ suitable for connection to the actuator control device  5  according to the invention. 
         [0034]    The circuit  12 ″ comprises means for receiving an actuator control transmission signal SCa provided by the device  5  and for supplying power to the motor  10  so as to obtain the tilt angle corresponding to the adjustment information item contained in the signal SCa. 
         [0035]    The circuit  12 ″ will not be described in any further detail here since its design is within the competence of the person skilled in the art enlightened by the teaching contained in the present application. 
         [0036]    Advantageously, the device  5  according to the invention can be implemented essentially in software form in a controller  6  of the vehicle. In such a case, the controller  6  will comprise in particular a central processing unit CPU, read-only and random-access memories ROM and RAM, respectively, interfaces and various circuits and means for signal processing. 
         [0037]    The actuator control device according to the invention may also be embodied in an essentially analogue form, for example by means of operational amplifiers, and this will be at a reduced cost. 
         [0038]    As will emerge more clearly below, some circuits, means and interfaces of the controller  6  may be dedicated more particularly to the device  5  according to the invention and will comprise for example, as shown in  FIG. 2 , a pulse with modulator (PWM)  53  and a power switch  54 . Of course, other types of circuit could be provided, such as for example a DC level generator when the actuator control transmission signal SCa is an analogue signal whose level forms the relevant information item for controlling the actuators. 
         [0039]    In the embodiment of  FIG. 2 , the device  5  according to the invention comprises registers  50  and  51 , a comparator  52 , the PWM modulator  53  and the power switch  54 . Of course, the functions of the elements  50 ,  51  and  52  may advantageously be implemented in the controller  6  by means of the RAM memory and program instructions which can be recognized by the central processing unit CPU so as in particular to execute read/write and comparison operations. 
         [0040]    Still in this embodiment, the controller  6  is connected to a CAN or LIN bus of the vehicle, via which the device  5  according to the invention receives the setpoint information item CD which is intended for controlling the actuators  1 D and  1 G. In order not to unnecessarily overload  FIG. 2 , it is considered here that the various means necessary in the controller for managing communications with the CAN or LIN bus are included in the module denoted INTERFACES. 
         [0041]    As a variant, the setpoint information item CD may not be received directly by the controller  6  as mentioned above but may rather be calculated by the latter from measurement information items which are transmitted via the CAN or LIN bus by vehicle attitude sensors. 
         [0042]    According to another variant, the setpoint information item CD or the measurement information items from the attitude sensors may be supplied to the controller  6  in the form of DC voltages which are then digitalized by analogue/digital conversion means included in the microcontroller  6 . 
         [0043]    The mode of operation of the device  5  according to the invention will now be described with reference to the algorithm of  FIG. 3 . 
         [0044]    The algorithm of  FIG. 3  comprises steps E 1  to E 7 . 
         [0045]    In the device  5  according to the invention, the registers  50  and  51  shown in  FIG. 2  are provided for storing values CD n  and CD n-1  of the setpoint information item CD, CD n  being the current value of CD at a time n and CD n-1  being the value of CD at a previous time n−1. 
         [0046]    Activation of the device  5  according to the invention starts with the execution of step E 1  during which the values CD n  and CD n-1  contained in the registers  50  and  51  are initialized to inactive values. In order to prevent needless displacements of the actuators, and also for safety reasons, an actuator control information item CDa and a supply voltage Vm are preferably also initialized to inactive values. 
         [0047]    Steps E 2  to E 7  are carried out in each algorithm processing loop so as to determine, from the setpoint information item CD, the actuator control information item CDa to be transmitted to the actuators  1 D and  1 G. 
         [0048]    In step E 2 , the current value CD n  of the setpoint information item CD is read and stored in the register  50 . 
         [0049]    In step E 3 , the comparator  52  carries out a comparison between the current CD n  and previous CD n-1  values of the setpoint information item CD. The values CD n  and CD n-1  are read into the registers  50  and  51 , respectively. 
         [0050]    If the values CD n  and CD n-1  are found to be different in step E 3 , the comparator  52  delivers in step E 4  an actuator control information item CDa having the value CD n . The information item CDa=CD n  is then transmitted to the actuators  1 D and  1 G by means of the actuator control transmission signal SCa, so as to bring about a displacement of the control rod  110  into a position corresponding to the value CD n . 
         [0051]    According to the invention, the signal SCa may be in various forms. In the preferred embodiment of  FIG. 2 , the signal SCa is pulse width modulated with the actuator control information item CD n  by the PWM modulator  53 . 
         [0052]    If the values CD n  and CD n-1  are found to be equal in step E 3 , the comparator  52  delivers in step E 5  an actuator control information item CDa having an inactive value, for example “0”. The information item CDa=0 is then transmitted to the actuators  1 D and  1 G in the same way as that described above in respect of CDa=CD n . The information item CDa=0 does not give rise to any rotation of the motors  10 , and the control rods  110  thus remain in their position. 
         [0053]    It should be noted here that the determination of the difference/equality carried out by the comparator  53  takes into account a given margin, and that the terms “different” and “equal” applied above to the values CD n  and CD n-1  should not be interpreted in a strict sense. In other words, according to one particular embodiment of the invention, the current value CD n  is found to be different from the previous value CD n-1  if the difference in absolute terms exceeds a certain threshold. Otherwise, the values CD n  and CD n-1  are found to be equal. 
         [0054]    Still with reference to  FIGS. 2 and 3 , step E 6  which is carried out after step E 4  or E 5  corresponds to storage of the current value CD n  in the register  51 . The value CD n  stored in the register  51  thus becomes the value CD n-1  taken into account in the following loop. Preferably this storage step E 6  is carried out after a certain time-out period, so as to take account of the time taken for the actuators to reach the setpoint position. 
         [0055]    Step E 7  terminates execution of the algorithm and deactivates the device  5  according to the invention, for example when a lighting stop command is detected by the controller  6 . 
         [0056]    According to the invention, it is also possible to supply power to the actuators  1 D and  1 G only when the signal SCa carries an actuator control information item CDa with an active value, that is to say a value other than “0” in this example, which is able to give rise to a rotation of the motors  10 . This functionality of the invention is implemented in the device  5  by means of the power switch  54 . 
         [0057]    In the embodiment of  FIGS. 2 and 3 , the power switch  54  consists for example of a transistor of the MOS type which is integrated in the controller  6 . The switch  54  comprises a first terminal which is connected to a supply voltage Vapc and a second terminal which is connected to a wire of the electrical power supply of the vehicle so as to supply the actuators  1 D and  1 G with a supply voltage Vm. 
         [0058]    The opening/closing of the switch  54  is controlled by the comparator  52 . 
         [0059]    When step E 4  of the algorithm of  FIG. 3  is carried out, the switch  54  is made to close and the supply voltage Vm=Vapc is supplied to the actuators  1 D and  1 G. The actuator control information item CDa transmitted to the actuators  1 D and  1 G is then active and the power supplied to said actuators permits the rotation of the motors  10 . 
         [0060]    When step E 5  is carried out, the actuator control information item CDa transmitted to the actuators  1 D and  1 G is inactive, CDa=0, thus preventing any undesirable displacement of the actuators  1 D and  1 G. 
         [0061]    Moreover, in step E 5 , as shown in  FIG. 3 , the switch  54  can be made to open and the supply voltage Vm=0 V is then supplied to the actuators  1 D and  1 G. This is because, when the actuators  1 D and  1 G are provided with an inactive information item CDa, maintaining the voltage Vm may be unnecessary in some embodiments. In such a case, the setting of the voltage Vm to 0 V provides an additional guarantee that the actuators  1 D and  1 G will not be displaced and may help to limit current consumption. 
         [0062]    In this embodiment which incorporates the switch  54 , the supply voltage Vapc may be the “after contact” voltage of the vehicle, that is to say a voltage which is present in the electrical power supply of the vehicle following actuation of the contact key by the driver. This is because the switch  54 , by keeping the application of the voltage Vapc to the actuators to the strict minimum, makes it possible to better satisfy the requirements in terms of service life of the actuators without it being necessary to use the voltage Vcode of the vehicle. Besides the substantial improvement in terms of service life, the incorporation of the switch  54  may also have an impact on reducing the number of connecting wires which are necessary for the lighting device of the vehicle. 
         [0063]    In another particular embodiment of the invention, the switch  54  may be in the form of a switch circuit of the SmartMOS type which is capable of performing intelligent functions such as, for example, detecting a fault in the electrical power supply wire or measuring the electrical current consumed. The SmartMOS switch circuit thus supplies the lighting and/or signaling system of the vehicle with information items which said system can advantageously use to perform its tasks. 
         [0064]    Of course, the present invention is not restricted to the details regarding the modes of embodiment described here by way of example, but rather extends to the modifications made by those skilled in the art without departing from the scope of the invention. 
         [0065]    Thus, for example, the actuator control device could in some applications be associated at the output with means for interfacing with a connection of the LIN type, so as to transmit the actuator control information item CDa to the actuator via this LIN connection. 
         [0066]    Moreover, the person skilled in the art can use the present invention to control actuators other than those dedicated to adjusting the tilt angle of headlamps, for example, in some applications, those used in the “Dynamic Bending Light” (DBL) function.