Abstract:
A headlight control system provides a several automated operational features. A problem with such systems in the past is the possibility of inadvertent operation of the vehicle without headlights under low light or other adverse conditions. Automated control is achieved through use of a finite state machine which defaults from a plurality of transient conditions to a running state which provides operational outputs to the low beam bulbs of the headlights.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field: 
         [0002]    The present invention relates generally to control of headlights on commercial motor vehicles and more particularly to a control system implemented in a finite state machine which affords control flexibility while avoiding unanticipated responses. 
         [0003]    2. Description of the Problem: 
         [0004]    Headlights serve several functions on a motor vehicle including: providing forward lighting for visibility under conditions of limited ambient light; increasing the visibility of the vehicle to other drivers (running light functionality); and affording a means of signaling to other drivers. Local laws governing headlight operation may differ as to time of day the lights are to be on. In addition, some locales require headlights to be illuminated if the windshield wipers have been turned on due to rain. In other locations it may be required that headlights be turned off at a weigh-station. Signaling to indicate an attempt to pass, or to indicate to a passing vehicle that a sufficient interval has opened to allow the passing vehicle to return to a lane may involve turning lights on, or off, depending upon the state of the lights prior to the signal. 
         [0005]    Headlights were formerly directly connected to switches installed in the vehicle passenger compartment or cab. Contemporary control schemes for vehicle electrical systems have favored substituting programmable controllers and controller area networks (“CAN”) for direct wiring between switches and loads. CAN systems and controllers afford a high degree of flexibility in application, the potential of a richer feature set and a commensurate opportunity for greater automation than direct wired systems. Mechanically CAN systems are much simpler than the traditional wiring harnesses and, possibly more importantly, the basic wiring does not change with the additions of features. However, providing against unanticipated operation stemming from programming omissions or changes in such systems takes on particular importance. Headlights are an example of a system where avoiding unintended operations is important in view of the need for headlights for safe vehicle operation under low ambient light conditions. 
         [0006]    Finite state machine descriptions of desired system behavior have recently found favor as a method of programming a system to provide greater assurance of fault-free behavior. It would be desirable to provide a control system for headlights which makes headlight operation for the desired function as simple as possible, which minimizes the chance of accidental illegal operation, which automates functions but automatically ensures headlight operation when legally required or on account of low ambient light conditions. 
       SUMMARY OF THE INVENTION 
       [0007]    According to the invention there is provided a headlight control system achieving a high degree of automation while preventing unintended operation of the vehicle without headlights under low light or rainy conditions. The headlight control system is implemented through conventional contemporary control systems in response to onboard sensors and switches which generate physical inputs to the control system. A finite state machine is implemented on a programmable controller of the control system, which sets a state in response to the inputs and potentially to the previous state. Each new state, as is conventional, determines values for the control outputs to the headlights. Implementation of control through a finite state machine accommodates at least a first automated operational feature. Among the states provided is a low or normal illumination state which sets outputs for operation of the low, but not the high beams of the headlights. Transient conditions are defined from all other possible states to the normal illumination state to avoid any unanticipated extinguishment of the headlights during vehicle operation. Generally, transients to the normal illumination state are based on the negation of a condition which previously obtained. They include any change in the inputs other than the specific combination required to move to a state other than the normal illumination state. 
         [0008]    Additional effects, features and advantages will be apparent in the written description that follows. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
           [0010]      FIG. 1  is a perspective view of a commercial tractor for the over the road trucks equipped with a headlight system with which the present invention is advantageously employed. 
           [0011]      FIG. 2  is a combined high-level block diagram and circuit for headlight operational control in accordance with the invention. 
           [0012]      FIG. 3  is a state transition graph illustrating non-emergency operation of the head light system. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]    Referring to the drawings and in particular referring to  FIG. 1  a tractor  105  is illustrated. Tractor  105  is conventionally configured as a cab  101  on frame  102  design, carried on wheels  104 . A door  103  provides access to cab  101 . A hood  109  forms the front portion of the cab. The headlights  110 ,  111 ,  112 ,  113  are mounted at the front of the hood  109 . Headlights  110 ,  111 ,  112 ,  113  may be operated to provide normal (low beam) and enhanced (low and high beam) forward illumination to allow low ambient light operation of the tractor  105 . Operation of the headlights  110 ,  111 ,  112 ,  113  may be temporarily engaged or interrupted as a way of signaling to other drivers. Such signaling conventionally includes flashing the headlights  110 ,  111 ,  112 ,  113  on from an off state to indicate an intention on the part of the operator of tractor  105  to pass, or flashing high beam headlights  112 ,  113  on when the tractor&#39;s low beam headlights  110 ,  111  alone are on, also to indicate an intention to pass. The headlights  112 ,  113  may be turned off from the enhanced forward illumination state to indicate passing as well. Any operational state of the headlights  110 ,  111 ,  112 ,  113  may be interrupted (i.e. all forced off), as is sometimes done to indicate to a passing vehicle that a sufficient interval has opened in front of the truck  105  to allow a change of lane into the lane occupied by tractor  105 . Although not described here, the tail marker lights may be operated in conjunction with the headlights. 
         [0014]      FIG. 2  illustrates communication links, hard wire connections to switches, and indicates signals applied to an electrical system controller (ESC)  30  for implementing control over headlights  110 ,  111 ,  112  and  113 . Headlights  110 ,  111 ,  112  and  113  are operated in response to inputs generated from several manual switches and, optionally, automatic sensors. The manual switches are not necessarily primarily for headlight control. ESC  30  is a category of body computer which may be programmed to implement most of the control scheme of the present invention. ESC  30  is linked to an electrical gauge control (EGC)  58  which controls most of the vehicles gauges, warning lights and which accepts many control inputs from most dashboard switches. The link between ESC  30  and EGC  58  is controller area network (CAN) bus  31  which conforms to the SAE J1939 protocol and which carries industry standard messages and allows for user defined messages. CAN&#39;s are data networks characterized in part by a messaging regime which does not specify destinations for the messages. Rather, messages are identified by source and type, and each controller connected to the bus receives the message and responds thereto based on its own programming. Thus a message originating with ESC  30  may be acted upon simultaneously by EGC  58 , a transmission controller (not shown), an engine controller (not shown), etc. Here however, only EGC  58  and ESC  30  are shown from among the controllers which may be connected to CAN bus  31 . 
         [0015]    While most dashboard switches are connected to the EGC  58 , most of the switches of direct interest to headlight control are connected by discrete wires directly to the ESC  30 . This architecture is not necessary to the invention, and may not be duplicated in other manufacturers&#39; vehicles, or even in future vehicles of the assignee of this patent. Among the switches connected directly to the ESC  30  is a four-position key switch  32 . The key switch  32  is engaged using the vehicle key and includes an off position, an accessory position, a run position and a cranking position. Two signal leads are connected from key switch  32  to the ESC  30  allowing application of signals H and I to the ESC. Because each signal line has an on/off state each of the four possible states of the key switch  32  may be indicated as an input to ESC  30 . 
         [0016]    The direct application of so many signal inputs to the ESC  30  stems from the disposition of these switches in the turn signal stalk  38 . The turn signal stalk  38  includes a momentary switch set  36 , which provides two inputs A and B to the ESC  30  and a set  34  of windshield wiper switches, which provides signals C, D and E to the ESC  30 . Momentary switch set  36  includes two switches, a flash to pass switch  44  and a headlight state transition switch  42 . Closure of these switches affects the states of signals A and B, respectively. The windshield wiper switches  34  are indirectly related to headlight operation. Some vehicles may be equipped for automatic headlight operation when the windshield wipers are in operation including intermittent operation, but excluding wiper operation initiated in response to the use of window washing fluid. Accordingly, selected combinations of signals C, D and E may invoke headlight operation. The windshield wiper switch set  34  and the momentary switch set  36  provide a logic high signal at a zero volt return (ZVR) level provided by the ESC  30  as signal “F”. 
         [0017]    A set of steering wheel-mounted interrupt switches  40  is connected to provide input “J” to the ESC  30 . The interrupt switches  40  are a ladder network of three switches which include a headlight interrupt switch and a marker light interrupt switch. 
         [0018]    The EGC  58  is connected to receive various inputs related to headlight operation. Among these inputs are a headlight enable switch  64  and an automatic headlight operation enable switch  66 . Engaging the automatic headlight operation enable switch allows the ESC  30  to respond to ambient light conditions as detected by an ambient light sensor  62 . The headlight switch  64  mimics a conventional, hard-wired headlight on/off switch. An IGN grid switch  60  simply indicates if the ignition is on or off (signal G) directly to the EGC  58 . The EGC  58  provides messages over CAN bus  31  indicating values for all of these inputs which may be acted upon by the ESC  30 . EGC also illuminates a high beam indicator  68  in response to a message received over CAN bus  31  from the ESC  30 . Positioning of the controls on the dash, on the steering wheel and on the turn signal stalk  38  place all of the controls within easy reach of a driver. 
         [0019]    The EGC  58  passes signals to ESC  30 , both over CAN bus  31  and over a hard wired, dedicated connection as indicated by signal “K”. The “K” signal is a headlight enable signal and duplicates a headlight enable message provided over the CAN bus  31 . It is necessary that at least the low beam headlights  110 ,  111  work even if operation of the ESC  30  or EGC  58  has become degraded or the CAN bus  31  has failed. Although not all of the uses of the discrete headlight enable signal K are shown, its presence on a line duplicating a message on bus  31  is illustrative of some the redundancy built into the system. However, the present application is concerned primarily with normal operation of the ESC  30 , not hardware redundancies built into the system to deal with failure of the ESC or EGC  58 . 
         [0020]    The ESC  30  incorporates internal power FET switches for applying power to each of the headlight bulbs  110 ,  111 ,  112 ,  113 . Low beam bulbs  110 ,  111  are grouped as low beam bulbs  50  and the high beam set  52  is similarly organized from high beam bulbs  112 ,  113 . The individual control output signals are labeled L, M, N and O. 
         [0021]    In terms of broad design parameters, the headlights  110 ,  111 ,  112 ,  113  are operated with all lights off, or with the low beams  50  on and the high beams  52  off, or with both the low and high beams on. Such of headlights  110 ,  111 ,  112 ,  113  as are on must be able to turn off in unison. ESC  30  may be programmed for lights on with wipers (“LOWW”). LOWW provides for the low beam headlights  110 ,  111  automatically turning on when the wipers are engaged (other than for washing). The low beams  50  remain on until the wipers are turned off and the headlights are manually turned off, which may occur either by operation of the headlight enable switch  64  or the key switch  32  moving to off. The wiper switches  34  are representative of a system secondary to the lights&#39; operation which may be related to the lights by programming of the ESC  30 . 
         [0022]    The EGC  58  has a multiple position switch (the headlight enable switch  64 ) providing an ON and an OFF input. Automatic headlight enable  66  is push button switch with the instruction becoming executive upon release of the button. Enable  66  includes an indicator light which is on when automatic headlight operation is enabled. A low light condition is defined as less than 1000 lux (plus or minus 15%) measured by an upward pointed light sensor  62  (SAE J2087). To enter a low light condition the upward pointing sensor  62  must measure less than 1000 lux for one continuous minute. Before indication of a low light condition is cancelled, the sensor must measure greater than 1000 lux for five continuous minutes. An indication of a low light condition is the default status, and accordingly, if no result is obtainable, the EGC  58  indicates that a low light condition is present. 
         [0023]    The EGC  58  provides an operating voltage on the headlight enable signal line “K” when the headlight enable switch  64  is on or all three of the following conditions obtain: automatic headlights  66  are active; the key as indicated by the ignition grid  60  is ON; and a low light condition exists (indicated by sensor  68 ). The EGC  58  transmits a “request for headlights” message when the headlight enable switch  64  is in the ON position. The EGC  58  concurrently transmits a request for “automatic headlights” over CAN bus  31  when: automatic headlights are active; the ignition grid in ON; and a low light condition exists. 
         [0024]    Before turning to the state transition graph for the finite state machine (FSM)  80 , the virtual inputs to the state machine, which are generated by the external conditions already described, are defined. A flash to pass request occurs when the ESC  30  measures a transition to logic low (ZVR) on the flash to pass switch  44  (signal “A”) and the key is in the RUN position (signals H, I). There is no longer a flash to pass request when the ESC  30  no longer measures logic low for the “A” signal. A headlight state transition request happens when the ESC  30  measures a transition to logic low from the headlight state transition switch  42 . A headlight request happens when any one (or more) of the following conditions obtains: (1) the ESC  30  measures operating voltage on the headlight enable input “K” from the EGC  58 ; (2) the EGC  58  transmits a message over the CAN bus  31  indicating a headlight request; or ( 3 ) the EGC  58  transmits a message over the CAN bus  31  indicating an automatic headlight request. A headlight Interrupt request occurs when the ESC  30  measures the voltage level which results from closure of the headlight interrupt switch in the ladder interrupt switch network  42 . This result obtains only if the (marker) interrupt switch is not concurrently closed. In other words, if the headlight and marker interrupt switches are closed during the same clock cycle no interrupt is recognized. A headlight interrupt request no longer occurs when the output of the interrupt switch  42  is no longer at the recognized logic level. The windshield wipers are on when the combination of windshield wiper switches  34  is in any state other than off and wash. The off state of the windshield wipers does not include the non-movement state of the intermittent setting of the wipers. It is assumed that the wipers require the ignition switch  32  to be in the RUN state before becoming operational. 
         [0025]    Referring now to  FIG. 3 , a state transition graph for FSM  80  is described. The outputs from all of the states are headlight control signals (i.e. L, M, N and O). For non-emergency vehicles outputs L and M (the high beams) are always the same as each other. Outputs N and O are always the same as each other (the low beams). Applications to emergency vehicles may use alternating illumination of headlights for signaling (for example on a tow truck). The preferred embodiment described here is for a conventional commercial tractor, and, while the invention could be extended to other types of vehicles, the preferred embodiment does not include such extensions of the control system. 
         [0026]    The preferred embodiment of the state machine  80  defines nine states. Since the headlights are either all off, in operation with just the low beams on, or all on, it is obvious that some states generate duplicate outputs. This is because some state definitions include a reference to the previous state, that is, the state machine has memory. Some state definitions here, ST 4 , ST 5 , ST 6 , ST 7 , ST 8  and ST 9 , are termed temporary states and include a reference or indication of what the immediately prior state of the system was. Put more concretely, these states correspond typically to conditional changes in output, such as flash to pass signaling. The remaining states may be termed the base states, that is they correspond to normal operational use of the lights, that is off, low beams and high beams. The base states are ST 1 , ST 2  and ST 3 . The state ST 1  is an idle state. In the idle state all of the headlight control signals are low (i.e. the headlights are off). ST 2  is termed the low illumination state which is employed for providing conventional low light visibility. In ST 2  the outputs to the low beams are high and the high beam outputs are set to low. ST 3  is termed the enhanced illumination state which is employed for increased visibility under low light conditions. In colloquial terms, the high beams are on. In ST 3  both the low and high beam control signals are high. The definition of a base state does not require a reference to any preceding state. 
         [0027]    The temporary states correspond to interruptions of normal operation. The state machine always defines a return path from a temporary state to a prior base state. In the preferred embodiment all temporary states have a base state as the immediately preceding state. ST 4  is the flash to pass from the lights off/idle state ST 1 . Both the low and high beam outputs are high. The state ST 5  is the flash to pass from the low illumination state ST 2 . The outputs dictated by this state are for both the low and high beams to be high. The ST 6  state is the flash to pass from the enhanced illumination state ST 3 . In the ST 6  state only the low beam signal is high. The ST 7  state is the interrupt state from the idle state ST 1 . In ST 7  the headlight outputs are both low. It might be added here that the reason for having such a state is related to the possible existence of the automatic headlight feature. Consider a truck at a weigh station where it is required that headlights be off when the vehicle is on or in the vicinity of the scales. Should the windshield wipers be engaged or low light conditions occur during waiting the driver would temporarily extinguish the lights to conform to the station&#39;s requirements. In the ST 7  state such engagement is temporarily suspended. The ST 8  state is a headlight interrupt from the low illumination state ST 2 . The ST 9  state is the headlight interrupt from the high illumination state ST 3 . In the ST 8  and ST 9  states the outputs to both the high and low beams are low. It may be observed that the states termed “temporary states” can only be reached from one of states ST 1 , ST 2  or ST 3 . Transitions out of the temporary states are either back to the origin state or to the ST 2  state. 
         [0028]    Transitions between states occur upon certain inputs, as defined above, occurring. The simplest transition relates moving from an off to the basic level of illumination used for enhancing visibility under low light conditions, that is, the outputs associated with state ST 2 . Transition TA from ST 1  to ST 2  occurs when there is no flash to pass input and one of the following occurs: (1) there is a headlight request input; (2) lights on with wipers is enabled and the wipers are on. 
         [0029]    Stringent conditions are required to avoid having a driver accidently turn the headlights off since conditions may have changed since the lights were turned on. For example, the headlights may have turned on automatically due to the windshield wipers having been turned on. Later, low light conditions may be satisfied, but the driver may turn the wipers off. The system should keep the headlights on despite the wipers being turned off. Stated more generally, additional operator inputs are required to turn headlights off after disappearance of a condition which gives rise to their automatic activation. Here the term automatic comprehends activation of the lights upon activation of an auxiliary system. This is pertinent when dealing with states relating to use of the headlights for illumination, or which are subsidiary to states where the headlights are used for illumination. States ST 2  and ST 3  reflect use of lights for illumination. Accordingly, transitions from those states to idle are logically complex. The transition T B  from ST 2  to ST 1  and similarly the transition T E  from ST 3  to ST 1  are logically complex events as expressed in the following logical formula:
       there is no headlight state transition request input   AND there is no flash to pass request input   AND ((there is no headlight request   AND lights on with wipers is disabled)   OR (lights on with wipers is enabled
           AND the windshield wipers are not on   AND there is no headlight request   AND (the key switch  60  is in the OFF position
               OR the windshield wipers are not on before there is not a headlight request))).   
               
               
 
         [0039]    The next input to be considered is that of a headlight state transition request, which occurs in response to a logic low transition of signal “B”. Basically, the event dealt with here is moving between the use and the cancellation of use of headlight high beams for illumination, but not signalling. The corresponding transitions are transitions T D  and T C , that is, back and forth between states ST 2  and ST 3 . It is also possible for a driver request a transition between high beams and low beams and just low beams while also using the flash to pass feature. Accordingly, the states which reflect invocation of the flash to pass feature from a state where the headlights are in use must be considered, i.e. states ST 5  (flash to pass from the low illumination state) and ST 6  (flash to pass from the enhanced illumination state). The corresponding transitions are T K  and T V  which provide for transitions from ST 5  to ST 3  and from ST 6  to ST 2 , respectively. Transitions T C , T D , T K  and T N  occur in response to a headlight state transition request provided only that the current state allows such. 
         [0040]    A flash to pass request is honored from the idle state ST 1 . Transition T F  from ST 1  to ST 4  occurs when there is low logic transition from the flash to pass switch  44  (signal “A”). The state transitions back to ST 1  (transition T G ) upon release of the flash to pass request and no manual or automatic headlight request has been received during the period (clock cycles) the flash to pass was requested. A return to the idle state ST 1  is not permitted from a flash to pass output state if it was entered from either the low illumination state ST 2  or the enhanced illumination state ST 3 . Logically a transition occurs when:
       there is not a flash to pass request   AND (there is not a headlight request   AND (lights on with wipers is not enabled
           OR (lights on with wipers is enabled
               AND the wipers are not on))).   
               
               
 
         [0046]    When there is an initial headlight request, a transition to low beam headlights  110  on is the default state. In other words, the headlights cannot start in the high beam state. Transitions out of the flash to pass from the idle state ST 4  are allowed to return to the idle state or to low illumination state ST 2 . ST 2  is the destination state in response to any headlight request after release of the flash to pass switch. The transition T H  thus follows when:
       there is not a flash to pass request   AND (there is a headlight request   OR (lights on with wipers is enabled
           AND the wipers on on)).   
               
 
         [0051]    Flash to pass requests from one of the headlight operational states ST 2  or ST 3 , initiated using the flash to pass switch  44 , are honored as long as no concurrent headlight transition request occurs. Transitions from one of the illumination states to the corresponding flash to pass states (transitions T I  and T L  to states ST 5  or ST 6 ) thus occur when:
       there is a flash to pass request   AND there is not a headlight state transition request.       
 
         [0054]    Flash to pass states default back to the illumination state that they were entered from upon release of the flash to pass switch  44 . Transitions T J  and T M  occur from states ST 5  and ST 6  when:
       there is not a flash to pass request   AND there is not a headlight transition request.       
 
         [0057]    As already described, logically, the system allows the headlight operation to be “interrupted” even when the headlights are not in use. The practical effect of this is to suppress automatic operation of the headlights in locations where the headlights are not desired for as long as the interrupt is maintained. Hence a transition T O  is provided from the idle state ST 1  to an interrupt from idle state ST 7 . The conditions for transition T O  are:
       there is a headlight interrupt request   AND there is not a flash to pass request   AND (there is not a headlight request   AND (lights on with wipers is not enabled
           OR (lights on with wipers is enabled
               AND the wipers are not on))).   
               
               
 
         [0064]    The transition T P  from the interrupt from idle state ST 7  back to the idle state ST 1  occurs with release of the interrupt request absent any intervening headlight request. The conditions for transition T P  are:
       the headlight interrupt request has been discontinued   AND there is not a headlight request   AND (lights on with wipers is not enabled
           OR (lights on with wipers is enabled
               AND the wipers are not on))).   
               
               
 
         [0070]    As described above, headlight interrupts suppress headlight operation from any of states ST 1 , ST 2  and ST 3 . Operation can be returned by one of the interrupt states ST 7 , ST 8  or ST 9  to a preceding state, or to the low illumination state ST 2 . Thus transition T Q  from ST 7  to ST 2  accounts for an intervening headlight request occurring during the interrupt from idle state ST 7 . The logic of the transition is:
       (There is a headlight request   OR (lights on with wipers is enabled
           AND the wipers are on)).   
               
 
         [0074]    The system allows normal headlight operation to be “interrupted” from either the low illumination state ST 2  or the enhanced illumination state ST 3 . Transitions T R  and T T  provide for transitions from states ST 2  and ST 3  to states ST 8  and ST 9 , respectively. The transition conditions are:
       there is a headlight interrupt request   AND there is not a flash to pass request   AND there is not a headlight state transition request   AND (there is a headlight request
           OR (lights on with wipers is enabled
               AND the wipers are on)).   
               
               
 
         [0081]    The transition T S  from the interrupt from low illumination state ST 8  back to the low illumination state ST 2  occurs with release of the interrupt request or there is a new, intervening headlight request. The conditions for transition T S  are:
       the headlight interrupt request has been discontinued   OR there is a new headlight request   OR (lights on with wipers is enabled   AND the wipers are on and it is a new request).       
 
         [0086]    The transition T U  from the interrupt from the enhanced illumination state ST 9  back to the enhanced illumination state ST 3  occurs with release of the interrupt request but only absent a new, intervening headlight request. The conditions for transition T U  are:
       the headlight interrupt request has been discontinued   AND there is not a new headlight request   AND (lights on with wipers is not enabled   OR (lights on with wipers is enabled
           AND the wipers are not on in response to a new request)).   
               
 
         [0092]    The transition T V  from the interrupt from enhanced illumination state ST 9  to the low illumination state ST 2  occurs when there is a new, intervening headlight request, maintaining the operational doctrine that all new requests for headlights default to the low illumination state. A release of the interrupt condition is not required. The conditions for transition T V  are:
       there is a new headlight request   OR (lights on with wipers is enabled   AND the wipers are on and it is a new request).       
 
         [0096]    Although outside the scope of this discussion, which deals with normal operation of a headlight control system through a finite state machine, ESC  30  is hardware modified to provide low beam power outputs upon failure of the processing portions of ESC  30  in response to a logically high K signal (which provides an operational voltage level). Under these circumstances all other headlight functionality is lost however. 
         [0097]    The invention provides for simplified headlight control consistent with a degree of automation and with preventing unintended operation of the vehicle, even briefly, without headlights under low light or rainy conditions. For purposes of the claims automatic headlight responses are considered those associated with low light sensors or operation of the wind shield wiper controls. 
         [0098]    While the invention is shown in only one of its forms, it is not thus limited but is susceptible to various changes and modifications without departing from the spirit and scope of the invention.