Abstract:
A method for detecting when a vehicle drives in a curve for which the wheel speed sensors of the non-driven wheels are sufficient and supplies a correct statement even in case of interferences or different circumferential distances. Also, an output signal can be recovered which corresponds to the values of the available transverse acceleration.

Description:
This application is a continuation of application Ser. No. 07/466,370, filed May 9, 1990, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to a method for generating different signals depending on whether a vehicle drives in a curve or on a straightaway and a method for determining the transverse acceleration while driving in curve. 
     From navigation systems it is known to determine the approximate driving direction of the vehicle from the difference Δv of the sensor signals from the non-driven wheels of a vehicle. 
     In anti brake lock control systems or anti slip control systems, it is also known to use steering angle sensors and/or transverse accelerometer and supply the output signals thereof as parameters to the control. The use of only the difference ΔV is not sufficient in this case since interferences can adversely affect these differences and since different circumferential distances (wheel diameters) can also lead to incorrect statements. 
     According to the invention, the difference Δv between the speeds of the left and right non-driven wheels is filtered so that the filtered difference Δv F  follows those changes having an increase greater than ± a with a delay, where a is about 0.2 g. 
     Δv F  and the mean valve v M  of the speed signals serve to form correction signals K i  according to the relation: ##EQU1## where Δv g  is a function which is stored and dependent upon the vehicle speed, and K 2  is formed only when |Δv F  |&gt;Δv G . A mean value K i  is formed from the successively determined correction signals K i , and a corrected difference Δv k  is formed from Δv F  according to 
     
         Δv.sub.K =Δv.sub.F -K.sub.i v.sub.M 
    
     wherein the correction K 1  is used when K 1  is formed once during a ride. A signal which indicates driving in a curve is generated if Δv K  exceeds a small speed value. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is block diagram of a preferred embodiment; 
     FIG. 2 illustrates a variation of the diagram of FIG. 1; 
     FIG. 3 is a plot of the differential speed signal Δv G  which is necessary to calculate the low speed correction signal, versus speed; 
     FIG. 4 is a plot of the corrected differential signal Δv K  for different transverse accelerations, versus speed. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In FIG. 1 the sensors associated with the non-driven wheels bear the reference numerals 1 and 2 and the filters downstream thereof are referenced as 3 and 4. These filters are configured such that the output signals V LF  and V RF  of these filters can follow the wheel speed signals V L  and V R  of the sensors 1 and 2 only up to a maximum slope C of ±1.38 g, for example. A block 5 forms the difference ΔV of the filtered signals. A block 6 forms the average value of the filtered signals ##EQU2## A block 7 serves to filter the differential signal ΔV. 
     The filtering is configured such that the output signal ΔV F  of the filter 7 can follow the input signals ΔV only up to a maximum slope of for example ±0.18 g. This measurement is based on the knowledge that faster changes of interferences cannot be caused by normal speed changes. 
     A correction signal K 1  is formed in the blocks 8 and 9. For this purpose, the signals ΔV F  and V M  are supplied to block 8. Moreover, the threshold value stage 9 activates this block 8 only if the speed V M  (=vehicle speed) exceeds 100 km/h, for example. From the K 1  -values which are determined in successive, short periods of time, a block 10 forms the mean value K 1  which is then stored. At the twenty-first measurement, for example, the K 1  -value reads: ##EQU3## It is also possible to interrupt the mean value formation after a certain number of values and use only the last determined mean value while driving. 
     The blocks 11-13 are used to determine the correction values K 2 . For this purpose, the signals ΔV F  and V M  are supplied to the subtracting block, the dividing block, and the comparing block 12. 
     The expression ##EQU4## is formed when the threshold value stage 11 activates the block 12 at V M  ≦100 Km/h and when ΔV F  &gt;ΔV G . The value ΔV G  which is necessary for the formation of K 2  and the comparison is stored as a curve in memory 13. In FIG. 3, this curve ΔV G  is represented as a function of the speed V M . The area with the hatching, which the curve defines, represents the plausibility area. The curve itself represents the plansibility boundary speed in dependency upon the vehicle speed. Different circumferential distances (wheel diameters) or a rotation of the vehicle around the vertical axis can cause the value of (±ΔV F ) to exceed this limit. With an increasing speed, the plausibility check which is carried out in the invention gains effectiveness. Therefore, the correction value K 1  recovered above 100 km/h and when recovered even once, is preferred. A selector circuit 15 represented as a switch selects the value K 1  for the remainder of the ride if this value was recovered once while driving. This is indicated by line 15a. From the K 2  -values an averaged value K 2  is also recovered in a block 14. 
     In an overlaying block 16, the so recovered correction value K 1  or K 2 , combined with V M , is overlayed on ΔV F  to form the corrected differential speed signal ΔV K  which is positive or negative depending on the curve direction. A downstream comparator 17 releases a signal when ΔV K  exceeds a small speed value of, for example, 2 km/h (curve determination) and changes the signal when, for example, the value falls below 1.5 km/h (straightaway determination). 
     If an element 18 where the curves corresponding to FIG. 4 are stored, where these curves represent the functions ΔV K  of speed for different transverse accelerations a q , is placed downstream of the overlaying element 16 of FIG. 2, it is possible to determine at this point the corresponding transverse acceleration a q  when inputting ΔV K  and the speed V M . The value can be output at terminal 19.