Abstract:
A wiper control system is provided which comprises a rain droplet detector, a multiplexer, a count register, and a wiper control unit. The rain droplet detector has a plurality of switches that are configured to be electrically connected by rain droplets, and each switch outputs one of two different signals according to an electrical connection thereof. The multiplexer receives signals from each of the plurality of the switches, and it is configured to repeatedly perform a process of selecting one of the received signals and outputting the selected signal. The count register is connected to the multiplexer to receive the signal output from the multiplexer, and it counts a number of the signals corresponding to the electrical connection of the switches of the rain droplet detector and outputs a counted value. The wiper control unit controls a speed of a wiper based on the counted value.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of priority of Korean Application No. 10-2003-0061535, filed on Sep. 3, 2003, the disclosure of which is incorporated herein by reference in its entirety.  
       FIELD OF THE INVENTION  
       [0002]     The present invention relates to a windshield wiper control system for a vehicle and a control method thereof. In particular the present invention relates to a windshield wiper control system that assigns a wiper speed to one of a number of levels, based on a count of a number of water droplets.  
       BACKGROUND OF THE INVENTION  
       [0003]     A conventional automatic wiper control system uses a rain sensor that is attached to a windshield, which detects rain using a refractive index of light. A wiper controller controls a wiper speed according to an amount of rain using signals of the rain sensor.  
         [0004]     Such conventional wiper control system cannot optimally operate the wiper according to the amount of rain. In particular, a wiper speed may become too high so that it hinders a driver&#39;s vision.  
         [0005]     The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention, and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person skilled in the art.  
       SUMMARY OF THE INVENTION  
       [0006]     Embodiments of the present invention provide a wiper control system and a wiper control method for a vehicle, capable of optimally controlling a wiper speed according to an amount of rain.  
         [0007]     In a preferred embodiment of the present invention, the wiper control system comprises a rain droplet detector, a multiplexer, a count register, and a wiper control unit. The rain droplet detector has a plurality of switches that are configured to be electrically connected by rain droplets, and each switch outputs one of two different signals according to an electrical connection thereof. The multiplexer receives signals from each of the plurality of the switches, and it is configured to repeatedly perform a process of selecting one of the received signals and outputting the selected signal. The count register is connected to the multiplexer to receive the signal output from the multiplexer, and it counts a number of the signals corresponding to the electrical connection of the switches of the rain droplet detector and outputs a counted value. The wiper control unit is connected to the count register to receive the counted value, and it controls a speed of a wiper based on the counted value.  
         [0008]     Preferably, the wiper control system further comprises a clock signal provider providing a clock signal to the multiplexer, and the multiplexer selects one of the signals input from the rain droplet detector based on the received clock signal.  
         [0009]     It is preferable that the multiplexer is configured to sequentially output the signals input from the plurality of the switches responding to the received clock signal.  
         [0010]     Preferably, the wiper control system further comprises a wiper position sensor detecting a position of the wiper and outputting a corresponding wiper position signal, and the clock signal provider receives the wiper position signal and is configured to output the clock signal when the wiper rotates by a predetermined angle. Furthermore, preferably, the predetermined angle is 45 degrees.  
         [0011]     It is preferable that the wiper control unit determines a rain droplet amount level based on the received counted value, determines a wiper speed level based on the determined rain droplet amount level, and controls the wiper to operate at the determined speed level.  
         [0012]     It is further preferable that the wiper control unit determines the rain droplet amount level using the counted values that are acquired during 3 strokes of the wiper.  
         [0013]     Preferably, the wiper control system further comprises a vehicle speed sensor detecting a vehicle speed and outputting a corresponding vehicle speed signal, and the wiper control unit receives the vehicle speed signal and controls the speed of the wiper based on the vehicle speed signal.  
         [0014]     It is preferable that the wiper control unit stops a control of the speed of the wiper when the vehicle speed is higher than a predetermined speed.  
         [0015]     It is also preferable that the wiper control unit is programmed to perform a control logic comprising: determining an initial wiper speed level among a plurality of wiper speed levels corresponding to different wiper speeds; determining a current rain droplet amount level among a plurality of rain droplet amount levels based on the received counted value; and controlling the speed of the wiper based on the initial wiper speed level and the determined rain droplet amount level.  
         [0016]     In an embodiment of the present invention, the wiper control method comprises: determining an initial wiper speed level among nine predetermined wiper speed levels that include nine sequential levels from a wiper speed level 1 to a wiper speed level 9, each of the predetermined wiper speed levels corresponding to a different wiper speed; detecting an amount of rain droplets and determining a corresponding rain droplet amount level among seventeen predetermined rain droplet amount levels that include seventeen sequential levels from a rain droplet amount level 0 to a rain droplet amount level 16, each of the predetermined rain droplet amount levels corresponding to a different rain droplet amount; and controlling a wiper speed based on the rain droplet amount level and the initial wiper speed level.  
         [0017]     It is preferable that in a method of controlling a wiper according to the present invention, the wiper speed level is regulated based on the rain droplet amount level and the initial wiper speed level, and the wiper is controlled to operate for a predetermined number of times in response to the regulated wiper speed level.  
         [0018]     Preferably, in a method of controlling a wiper according to the present invention, the wiper is controlled to not operate if it is determined that the amount of the rain droplets corresponds to the rain droplet amount level 0, which is indicative of no rain droplets.  
         [0019]     Preferably, in a method of controlling a wiper according to the present invention, in the case that the amount of the rain droplets corresponds to a rain droplet amount level 1, the wiper speed level is maintained if the initial wiper speed level is the wiper speed level 1, the wiper speed level is lowered by one level if the initial wiper speed level is the wiper speed level 2, and the wiper speed level is lowered by two levels if the initial wiper speed level is between a wiper speed level 3 and a wiper speed level 9.  
         [0020]     It is preferable that in a method of controlling a wiper according to the present invention, in the case that the amount of the rain droplets corresponds to between a rain droplet amount level 2 and a rain droplet amount level 4, the wiper speed level is maintained if the initial wiper speed level is the wiper speed level 1, and the wiper speed level is lowered by one level if the initial wiper speed level is between a wiper speed level 3 and a wiper speed level 9.  
         [0021]     Preferably, in a method of controlling a wiper according to the present invention, in the case that the amount of the rain droplets corresponds to between a rain droplet amount level 5 and a rain droplet amount level 12, the wiper speed is maintained at the initial wiper speed level.  
         [0022]     Preferably, in a method of controlling a wiper according to the present invention, in the case that the amount of the rain droplets corresponds to between a rain droplet amount level 13 and a rain droplet amount level 15, the wiper speed level is increased by one level if the initial wiper speed level is between a wiper speed level 1 and a wiper speed level 8, and the wiper speed level is maintained at the initial wiper speed level if the initial wiper speed level is a wiper speed level 9.  
         [0023]     Preferably, in a method of controlling a wiper according to the present invention, in the case that the amount of the rain droplets corresponds to a rain droplet amount level 16, the wiper speed is increased by two levels if the initial wiper speed level is between a wiper speed level 1 and a wiper speed level 7, the wiper speed is increased by one level if the initial wiper speed level is a wiper speed level 8, and the wiper speed is maintained at the initial wiper speed level if the initial wiper speed level is a wiper speed level 9. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention, and, together with the description, serve to explain the principles of the invention, where:  
         [0025]      FIG. 1  is a block diagram of a wiper control system according to an embodiment of the present invention; and  
         [0026]      FIGS. 2   a  and  2   b  show a flowchart of a wiper control method according to a preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]     Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.  
         [0028]     As shown in  FIG. 1 , a wiper control system according to a preferred embodiment of the present invention includes a rain droplet detector  10  that detects an amount of rain droplets and outputs a corresponding signal.  
         [0029]     In the embodiment of  FIG. 1 , the rain droplet detector  10  includes a plurality of switches that are mounted on a wiper  90 . Each switch includes an input pin and an output pin. In a preferred embodiment, the number of switches is 16, but the number of the switches is not restricted to this.  
         [0030]     The input pin and the output pin are configured to be electrically connected to each other when a rain droplet exists therebetween. If the input and output pins are electrically connected, the corresponding switch outputs a high signal, but otherwise the corresponding switch outputs a low signal. Accordingly, a number of the high signals output from the rain droplet detector  10  varies according to an amount of rain droplets that connect input and output pins.  
         [0031]     A multiplexer  20  is connected to the rain droplet detector  10 . The multiplexer  20  can be a normal multiplexer. That is, the multiplexer  20  routes one of the input values input from input terminals to an output terminal.  
         [0032]     Preferably, the multiplexer  20  has a plurality of input terminals whose number is equal to the number of switches of the rain droplet detector  10 , and one output terminal. In a preferred embodiment, the multiplexer  20  has sixteen input terminals, and each of the input terminals is respectively connected to each switch of the rain droplet detector  10 .  
         [0033]     Therefore, in a preferred embodiment, the multiplexer  20  selects one signal of sixteen signals input from the rain droplet detector  10 , and outputs the selected signal through the output terminal. Thus, in this embodiment of the present invention, the multiplexer  20  is a 16:1 multiplexer.  
         [0034]     In a preferred embodiment, the selection of the input signal in the multiplexer  20  is performed based on a clock signal input from a clock signal provider  50 , which is preferably connected to the multiplexer  20  through four terminals. In this embodiment, the clock signal provider  50  provides the multiplexer  20  with a 4-bit clock signal. As an example, the clock signal provider  50  can produce the clock signal using four lower-level bits of an electronic control unit (ECU) of a vehicle. That is, the multiplexer  20  selects one signal from the sixteen input signals based on the 4-bit clock signal.  
         [0035]     Subsequently, the multiplexer  20  sequentially outputs the input signals according to the clock signal input from the clock signal provider  50 .  
         [0036]     The clock signal provider  50  receives a synchronization signal from a wiper position sensor  60  that detects a position of a wiper  90 , and outputs the clock signal to the multiplexer  20  in response to receiving the synchronization signal. That is, the timing of outputting of the clock signal is determined based on the synchronization signal input from the wiper position sensor  60 .  
         [0037]     In a preferred embodiment, the wiper position sensor  60  outputs the synchronization signal to the clock signal provider  50  when the wiper  90  rotates by a predetermined angle (e.g., 45 degrees).  
         [0038]     When the wiper  90  is in a vertical state or in a horizontal (initial) state, many rain droplets that had previously been wiped by the wiper  90  may exist around the rain droplet detector  10 . In such positions, the rain droplet detector  10  may inaccurately detect an amount of rain droplets. Therefore, it is preferable that an amount of rain droplets is detected when the wiper  90  rotates by 45 degrees.  
         [0039]     A count register  30  is connected to the multiplexer  20  to receive the signal output from the multiplexer  20 . The counter register  30  sequentially receives the signal from the multiplexer  20 , and counts a number of the high signals. An amount of rain droplets is proportional to the number of the high signals.  
         [0040]     Eventually, the count register  30  counts a number of the switches of the rain droplet detector  10  that are electrically connected (i.e., turned on). Then, the count register  30  outputs the counted number to a wiper control unit. In a preferred embodiment, the wiper control unit is wiper fuzzy controller  70 .  
         [0041]     The wiper fuzzy controller  70  controls a speed of the wiper  90  based on the counted number input from the count register  30 . In a preferred embodiment, the wiper fuzzy controller  70  determines a rain droplet amount level based on a mean value of count values calculated while the wiper  90  undergoes three strokes, and controls the wiper speed based on the determined rain droplet amount level.  
         [0042]     The wiper fuzzy controller  70  preferably includes a processor, a memory, and other necessary hardware and software components, as would be understood by persons of ordinary skill in the art, to permit the control unit to communicate with sensors and to execute the control function as described herein.  
         [0043]     Furthermore, the wiper fuzzy controller  70  also receives a vehicle speed signal indicative of a speed of the vehicle, and controls the speed of the wiper  90  based on the received vehicle speed signal. If the vehicle speed is higher than a predetermined speed (e.g., 100 km/h), the wiper fuzzy controller  70  stops a control of the wiper speed, because a change of the wiper speed while the vehicle runs at a high speed may hinder a driver&#39;s vision.  
         [0044]     The wiper fuzzy controller  70  determines a rain droplet amount level I based on the count value input from the count register  30 , and determines a wiper speed level C based on the determined rain droplet amount level.  
         [0045]     Because, in a preferred embodiment, the count value input from the count register  30  may be one of seventeen values from 0 to 16, the rain droplet amount level I is set to vary from a level 0 to a level 16 (seventeen levels). If I is 0, there is no rain, and if I is 16, it indicates a maximum amount of rain droplets on the seventeen value scale.  
         [0046]     For example, in another preferred embodiment, the wiper speed level C can be set to vary from a level 1 to a level 9.  
         [0047]     If the wiper speed is determined, the wiper fuzzy controller  70  controls the wiper  90  to operate a predetermined number of times at the determined speed level. The predetermined number of times can preferably be determined to be proportional to the speed level. For example, the predetermined number of times can be set according to the following table.  
                                                                             wiper speed   slower                     faster            level   1   2   3   4   5   6   7   8   9               operating   4   5   6   6   7   8   8   9   10       times                  
 
         [0048]     It is to be understood that the present invention is not to be limited to the number of, or relationship between, preferred speed and rain droplet levels described herein.  
         [0049]     Referring to  FIGS. 2A and 2B , a wiper control method according to a preferred embodiment of the present invention will be explained hereinafter. In the drawings, a character I indicates a level of an amount of rain droplets, and a character C indicates a level of a wiper speed.  
         [0050]     At first (“Start” in  FIG. 2A ), the wiper fuzzy controller  70  determines an initial wiper speed level C among the nine predetermined wiper speed levels.  
         [0051]     In step S 201 , the wiper fuzzy controller  70  determines whether the wiper  90  has been operating in another control mode.  
         [0052]     If the determination in step S 201  is affirmative, the wiper fuzzy controller  70  determines a current wiper speed level as the initial wiper speed level C (step S 202 ).  
         [0053]     On the other hand, if the determination in step S 201  is negative, the wiper fuzzy controller  70  sets the wiper speed level C as 5, that is, the wiper fuzzy controller  70  determines the initial wiper speed level C as an intermediate value on the scale of speed values (step S 203 ).  
         [0054]     Then, in step S 204 , the wiper fuzzy controller  70  receives the count value from the count register  30 , and determines a corresponding rain droplet amount level I among the seventeen rain droplet amount levels.  
         [0055]     The wiper fuzzy controller  70  determines whether a value of I is equal to 0 in step S 205 , and if so, the wiper fuzzy controller  70  stops the operation of the wiper  90  in step S 206 .  
         [0056]     If the determination in step S 205  is negative, it is determined whether the value of I is equal to 1 in step S 207 .  
         [0057]     If the determination in step S 207  is affirmative, it is determined whether a value of C is equal to 1 in step S 208 .  
         [0058]     If the determination is step S 208  is affirmative, the wiper speed level is maintained at the initial wiper speed level 1 (step S 209 ).  
         [0059]     On the other hand, if the determination in step S 208  is negative, it is determined whether the value of C is equal to 2 in step S 210 .  
         [0060]     If the determination in step S 210  is affirmative, the wiper speed level is lowered by one level. That is, the wiper speed level is lowered from the level 2 (C=2) to the level 1.  
         [0061]     If the determination in step S 210  is negative, it is determined whether the value of C is between 3 and 9 in step S 212 .  
         [0062]     If the determination in step S 212  is affirmative, the wiper speed level is lowered by two levels in step S 213 .  
         [0063]     After performing steps S 209 , S 211 , and S 213 , the wiper fuzzy controller  70  controls the wiper  90  to operate at the determined speed level for the specific times as shown in the table hereinabove (step S 214 ).  
         [0064]     If the determination in step S 212  is negative, the wiper fuzzy controller  70  causes an error message to be output in step S 215 .  
         [0065]     The control procedure returns to step S 204  after performing steps S 214  and S 215 .  
         [0066]     Meanwhile, if it is determined that the value of I is not 1 in step S 207 , it is determined whether the value of I is between 2 and 4 (S 216 ).  
         [0067]     If the determination in S 216  is affirmative, it is then determined whether the value of C is equal to 1 (S 217 ).  
         [0068]     If the determination in S 217  is affirmative, the wiper speed level is maintained at a current speed level, e.g., at the level 1 (S 218 ).  
         [0069]     If the determination in S 217  is negative, it is determined whether the value of C is between 2 and 9 (S 219 ).  
         [0070]     If the determination in S 219  is affirmative, the wiper speed level is lowered by one level (S 220 ).  
         [0071]     After performing steps S 218  and S 220 , the wiper fuzzy controller  70  controls the wiper  90  to operate at the determined speed level for the specific times as shown in the table 2 (step S 221 ).  
         [0072]     If the determination in step S 219  is negative, the wiper fuzzy controller  70  causes an error message to be output (S 222 ).  
         [0073]     The control procedure returns to step S 204  after performing steps S 221  and S 222 .  
         [0074]     Meanwhile, if the determination in step S 216  is negative, it is determined whether the value of I is between 5 and 12 in step S 223 .  
         [0075]     If the determination is step S 223  is affirmative, the wiper speed level is maintained at the initial speed level (S 224 ). Then, the control procedure returns to step S 204 .  
         [0076]     If the determination in step S 223  is negative, it is determined whether the value of I is between 13 and 15 in step S 225  (referring to  FIG. 2B , carrying over from  FIG. 2A , from (B)).  
         [0077]     If the determination in step S 225  is affirmative, it is determined whether the value of C is between 1 and 8 in step S 226 .  
         [0078]     If the determination in step S 226  is affirmative, the wiper speed level is increased by one level in step S 227 .  
         [0079]     On the other hand, if the determination in step S 226  is negative, it is determined whether the value of C is 9 in step S 228 .  
         [0080]     If the determination in step S 228  is affirmative, the wiper speed level is maintained at the initial speed (level 9) (S 229 ).  
         [0081]     After performing steps S 227  and S 229 , the wiper fuzzy controller  70  causes the wiper  90  to operate at the determined speed level for the specific times as shown in the table hereinabove (step S 230 ).  
         [0082]     If the determination in step S 228  is negative, the wiper fuzzy controller  70  causes an error message to be output in step S 231 .  
         [0083]     The control procedure returns to step S 204 , after performing steps S 230  or S 231 .  
         [0084]     If the determination in step S 225  is negative, it is determined whether the value of I is equal to 16 in step S 232 .  
         [0085]     If the determination in step S 232  is negative, the control procedure returns to step S 204 , (in  FIG. 2A , via continuation marker (A)).  
         [0086]     If the determination in step S 232  is affirmative, it is determined whether the value of C is between 1 and 7 in step S 233 .  
         [0087]     If the determination in step S 233  is affirmative, the wiper speed level is increased by two levels (S 234 ).  
         [0088]     If the determination in step S 233  is negative, it is determined whether the value of C is equal to 8 in step S 235 .  
         [0089]     If the determination in step S 235  is affirmative, the wiper speed level is increased by one level in step S 236 .  
         [0090]     If the determination in step S 235  is negative, it is determined whether the value of C is equal to 9 in step S 237 .  
         [0091]     If the determination in step S 237  is affirmative, the wiper speed level is maintained at the initial wiper speed (level 9) (S 238 ).  
         [0092]     After performing steps S 234 , S 236 , and S 238 , the wiper fuzzy controller  70  causes the wiper  90  to operate at the determined speed level for the specific times as shown in the table 2 (step S 239 ).  
         [0093]     Meanwhile, if the determination in step S 237  is negative, the wiper fuzzy controller  70  causes an error message to be output in step S 240 .  
         [0094]     The control procedure returns to step S 204 , after performing steps S 239  or S 240 , (refer to  FIG. 2A , through continuation marker (C)).  
         [0095]     Preferably, the wiper fuzzy controller  70  determines an amount of rain droplets, by a mean value of six detected values for the three strokes of the wiper  90 .  
         [0096]     According to the various embodiments of the present invention, the wiper speed can be automatically changed according to the amount of rain droplets, thereby increasing a driver&#39;s convenience level.  
         [0097]     Furthermore, when the vehicle speed is higher than the predetermined speed, the operation of the wiper speed control is stopped, thereby increasing safety.  
         [0098]     Although preferred embodiments of the present invention have been described in detail hereinabove, it should be clearly understood that many variations and/or modifications of the basic inventive concepts herein taught which may appear to those skilled in the present art will still fall within the spirit and scope of the present invention, as defined in the appended claims.