Abstract:
A safety logic for vehicle rollover detection systems comprising a main rollover detection logic and at least one protection device for the occupant or occupants of the vehicle, including a vehicle lateral acceleration sensor ( 11 ), which generates an output signal indicating a near rollover event, when a lateral acceleration of a vehicle exceeds the first predefined threshold value ( 15 ) or, when a lateral acceleration of vehicle exceeds the second predefined threshold value ( 16 ) that is lower than the first predefined threshold value ( 15 ) and simultaneously at least one additional safety logic activation signal is present ( 1, 1′, 1″, 1′″ ).

Description:
TECHNICAL FIELD 
   The present invention relates to a safety logic for vehicle rollover detection systems comprising a main rollover detection logic and at least one protection device for the occupant or occupants of the vehicle. The present invention relates also to a method of determining dangerous situations that with high probability may lead to a rollover of a vehicle. 
   BACKGROUND OF THE INVENTION 
   The purpose of the rollover detection system is activation of protection devices such as seat belts pretensioners, pop-up roll bars or air bags, especially air bags protecting occupants&#39; heads during rollover accident. 
   In many systems for detecting dangerous situations, in particular in rollover detection systems there are two paths of signal processing: a main path being the main logic and an independent arming path, being a separate safety logic. An essential purpose of safety logic is to decrease the probability of inadvertent deployment in an event of failure or error in main rollover detection logic, wherein an activation signal of the main logic is summed with an activation signal of the safety logic by means of AND function at the last stage of processing, directly before an activation of protection devices. 
   Examples of logics of this kind are disclosed in U.S. Pat. Nos. 6,535,800, 6,600,414 or WIPO publication WO 03/010034. Publication WO 03/010034 discloses a rollover determination system comprising a first roll rate sensor, a lateral acceleration sensor and a main controller that determines, whether there is a possibility of rollover of the vehicle on the basis of the roll rate and lateral acceleration of the vehicle. The system comprises also a safety logic for confirming a rollover accident, whose output is summed with an output signal of a main rollover detection logic by means of AND gate. 
   SUMMARY OF THE INVENTION 
   The aim of the present invention is to provide a safety logic for vehicle rollover detection systems, which would generate an activation signal during a vehicle rollover or near rollover event. Such a logic should also feature a resistance for mechanical vibrations, simple construction, low manufacturing costs and could be used as an additional safety solution for rollover detection systems without their considerable modifications. 
   The aim of the present invention is also to provide a simple method for detecting dangerous situations that may end up with a rollover of a vehicle. 
   According to the present invention there is provided a safety logic for vehicle rollover detection systems comprising a main rollover detection logic and at least one protection device for the occupant or occupants of the vehicle, which according to the invention is connected with the vehicle lateral acceleration sensor and generates the output signal indicating a near rollover event, when a lateral acceleration of a vehicle exceeds the first predefined threshold value or, when a lateral acceleration of vehicle exceeds the second predefined threshold value that is lower than the first predefined threshold value and simultaneously at least one additional safety logic activation signal is present. 
   An activation of the safety logic may be used, for example, to active repeatable protection devices, that activate in potentially dangerous situation and return to its steady state, shall it pass, such as e.g. mechanical resetable seatbelts pretensioners. 
   It is especially advantageous if the additional safety logic activation signal, according to the present invention, is a signal delivered by the main logic. 
   Thanks to application of main logic signals in operation of the safety logic, additional sensors are not required. Even during failure of the main logic, the safety logic shall be substantially inactive during normal driving conditions not threatening a rollover (for example driving straight, gentle driving with low speed). An additional activation signal may occur in the main logic, at an intermediate stage of signal processing, as a result of main logic algorithm activity, or may be also generated by the main logic solely for the needs of the safety logic, using a simple logic. 
   Therefore it is advantageous if the additional signal of activation of the safety logic is generated by the main logic, when a roll rate of vehicle exceeds the predefined threshold value. 
   In this case, it is also advantageous if beside of exceeding the predefined threshold value by a roll rate of vehicle, to generate additional activation signal, exceeding linear velocity of vehicle above the predefined threshold value is required. 
   An additional activation signal of the safety logic may also be generated by the main logic, only if a roll angle of vehicle exceeds a predefined threshold value 
   Moreover, it is advantageous if the safety logic, according to the present invention, has a lateral acceleration sensor, which signal is not used by the main logic. 
   The safety logic according to the present invention, may also preferably contain a vehicle roll rate sensor, and an additional activation signal of the safety logic shall occur when a signal of the vehicle roll rate sensor exceeds the predefined threshold value. 
   Obviously in this solution there may occur two additional activation signals: the first from vehicle roll rate sensor of the safety logic, and the second from the main logic. 
   The safety logic according to the present invention is relatively simple construction, therefore features a high probability of activation during dangerous situations, that not necessarily need to end up with a vehicle rollover. Therefore to activate protection devices a main logic and the safety logic activation is necessary. 
   Owing to this an appropriate protection device e.g. air-bags shall be deployed only when both logics are activated. 
   It is advantageous if at least one activation signal is sustained for a predetermined period. 
   It is also advantageous if at least one sensor input value is pre-processed. 
   A pre-processing preferably involves at least signal scaling, removing a sensor drift and/or filtering a signal. 
   In particular, according to the present invention there is provided a safety logic for vehicle rollover detection systems comprising a main rollover detection logic and at least one protection devices for the occupant or occupants of the vehicle, where the main logic activation signal is summed with the safety logic activation signal by means of an AND gate at the last stage of pre-processing, directly before activation of protection devices, where, at least one additional activation signal, generated by the main logic at an intermediate stage of pre-processing path, is necessary to activate the safety logic. 
   According to the present invention there is also provided a method of determining vehicle near rollover situations, characterized in that, it comprises a measuring of lateral acceleration of a vehicle and generating an output activation signal that determines near rollover situation, if a lateral acceleration of vehicle exceeds the first predefined threshold value or, a lateral acceleration of vehicle exceeds second predefined threshold value that is lower than the first predefined threshold value and at least one additional activation signal is present. 
   The method according to the present invention may preferably include measuring a roll rate of vehicle, and an additional activation signal occurs, when a roll rate of vehicle exceeds the predefined threshold value. 
   The method according to the present invention may also preferably include measuring a linear velocity of vehicle, and an additional activation signal occurs, when a linear speed of vehicle exceeds the predefined threshold value. 
   The method according to the present invention may also include measuring a roll angle of vehicle, and an additional activation signal shall occur, when a roll angle of vehicle exceeds the predefined threshold value, wherein a roll angle may be calculated on the basis of vehicle roll rate. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The safety logic according to the present invention is presented below by way of examples of preferred embodiments with reference to figures of the drawing in which: 
       FIG. 1  is a block and circuit diagram of an embodiment of a rollover detection system comprising the logic according to the present invention 
       FIG. 2  is a block and circuit diagram of another embodiment of a rollover detection system, 
       FIG. 3  is a block and circuit diagram of further embodiment of a rollover detection system, 
       FIG. 4  is a block and circuit diagram of a yet another embodiment of a rollover detection system, and 
       FIG. 5  is a block and circuit diagram of an implementation of a rollover detection system. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   As shown on the diagram in  FIG. 1 , in the rollover detection system there are two logics: the safety logic  1  and the main logic  2 . 
   The main logic  2  collects signals from the block of sensors  21 , whose element is, among others, a vehicle lateral low acceleration sensor (YLG)  11 , fixed in vehicle in such a way that its working axis is perpendicular to the longitudinal and vertical axis of vehicle. This sensor may be, for example, sensor of the type ADXL 202 made by Analog Devices, Inc., USA. Sensor of this type is capable of detection of accelerations in the range from 0 g to about ±2 g. 
   The input signals of the main logic  2  are subsequently processed by serially connected processing blocks  22 ,  23 ,  24  and, in accordance with the working algorithm of the main logic, in the case of rollover of vehicle the activation signal occurs at the input of the AND gate  3 . 
   A signal of the sensor  11  is the first input signal of the safety logic  1  and is processed by pre-processing module  12 , where signal scaling, removing a sensor drift and broad-band filtering takes place to remove a noise of the sensor before digital sampling. Pre-processing modules discussed below realize functions similar to that of the module  12 . 
   An absolute value of the output signal of the module  12  is subsequently compared in comparators  13  and  14  with predefined threshold values  15  (“threshold_YLG_ 1 ”) and  16  (“threshold_YLG_ 2 ”). The right choice of these and others parameters depends on a lot of factors, like for example a wheel track, a mass, a position of centre of gravity, or a moment of inertia of vehicle. 
   At the outputs of the comparators  13  and  14  the TRUE signal of activation occurs, if a filtered signal of the sensor  11  exceeds the predefined threshold values  15  or  16 . Next these signals are sustained for a predetermined periods “latching_YLG_ 1 ” and “latching_YLG_ 2 ” in the modules  17  and  18 . 
   The lateral acceleration of vehicle within the range from 1.0 to 1.8 g, that is value exceeding the first threshold value “threshold_YLG_ 1 ”, unlikely occurs during normal driving conditions. It may occur during aggressive driving or side collision, thus an activation of the comparator  13  leads to direct activation of the safety logic  1 . In this case an activation signal is sent by OR gate  21 , sustained in module  22  for 0.2 s (“latching_OUT”) and becomes the first input of an AND gate  3 , the activation of which (TRUE signal) leads to an activation of the protection devices. 
   Since a lateral acceleration of vehicle ranging from 0.1 to about 0.8 g, that is value exceeding the second threshold value “threshold_YLG_ 2 ”, may occur during normal driving conditions, for example during driving a sharp turns, aggressive driving, or considerable bank of vehicle, an additional activation signal is necessary to activate the safety logic  1 . 
   In system shown in  FIG. 1 , an additional activation signal is delivered from the main logic. At intermediate stage of processing of main logic  2  signals, after processing block  23 , an activation signal is delivered also at the input of the AND gate  19 , the second input of which is the activation signal of comparator  14  which is sustained by module  18  for a predetermined period “latching_YLG_ 2 ”. An activation signal of the gate  19  is sustained for a predetermined period “latching_YLG_ 2 _OUT” in module  20  and it is the second input of the OR gate  21 . 
   Consequently, to active occupant protection devices the following condition is required: 
   a) an activation of the main logic  2  and a lateral acceleration value exceeding “threshold_YLG_ 1 ”  15  or 
   b) an activation of the main logic  2  and a lateral acceleration value exceeding “threshold_YLG_ 2 ”  16  (lower than “threshold_YLG_ 1 ”), simultaneously with indirect activation of the main logic  2 . 
   An indirect activation of the main logic depends on the working algorithm of the main logic  2  and in particular it may mean in particular exceeding a roll rate or a roll angle of the vehicle, or a linear speed of the vehicle above predefined threshold value, wherein roll angle of vehicle may be calculated by the main logic on the basis of a roll rate of vehicle by means of integration of roll rate. 
   In other embodiments of the safety logics presented below, the reference numerals of the elements performing the same functions correspond to those in  FIG. 1 . 
   The input of the safety logic  1 ′, shown in  FIG. 2  is separated from the input of the main logic  2 . The safety logic  1 ′ has an independent vehicle lateral low acceleration sensor  11 ′ and an independent vehicle roll rate sensor (ARS)  25 . The signal of the sensor  25  is processed in the module  26  and compared in the comparator  27  with a predefined threshold value (“threshold_ARS”)  28 , on the output of which an activation signal will appear, if the threshold value  28  is exceeded. The activation signal of the comparator  27  is sustained in the module  29  for 0.1 s (“latching_ARS”) and it is the second input of the gate  19 ′. 
   As it is shown in the embodiment, an additional activation signal is generated by the safety logic  1 ′ and an indirect coupling of both logics is not present. 
   The Table 1 below shows preferred ranges of values of parameters of calibration of the safety logic according to the present invention and their example values for the logic  1 ′ shown in  FIG. 2 . 
   
     
       
             
             
             
             
           
             
             
             
             
             
           
         
             
                 
               TABLE 1 
             
             
                 
                 
             
             
                 
               Calibration parameter 
               Preferred range 
               Example value 
             
             
                 
                 
             
           
           
             
                 
             
           
        
         
             
                 
               threshold_YLG_1 
               from 1.0 to 1.8 [g] 
               1.3 
               g 
             
             
                 
               threshold_YLG_2 
               from 0.1 to 0.8 [g] 
               0.3 
               g 
             
             
                 
               threshold_ARS 
               from 15 to 40 [°/s] 
               30 
               °/s 
             
             
                 
               latching_YLG_1 
               from 0.1 to 0.5 [s] 
               0.1 
               s 
             
             
                 
               latching_YLG_2 
               from 0.1 to 0.5 [s] 
               0.25 
               s 
             
             
                 
               latching_ARS 
               from 0.1 to 0.5 [s] 
               0.1 
               s 
             
             
                 
               latching_YLG_2_OUT 
               from 0.1 to 0.5 [s] 
               0.2 
               s 
             
             
                 
               latching_OUT 
               from 0.1 to 0.5 [s] 
               0.2 
               s 
             
             
                 
                 
             
           
        
       
     
   
     FIG. 3  shows another embodiment of the safety logic  1 ″ according to the present invention in the rollover detection system. This logic differs from the logic in  FIG. 1  by the presence of the sensor  11 ′ and the type of condition of indirect activation of the main logic, which in this case occurs, when a roll rate (ARS) as well as a linear velocity (VX) of vehicle exceed threshold values predefined in the main system. 
     FIG. 4  presents yet another embodiment of the safety logic  1 ′″. Unlike the logic in  FIG. 2 , there is one more additional activation signal generated by the main logic  2 , which is also a signal of exceeding roll rate, but obtained on the basis of indications from vehicle roll rate sensor of the main logic. A doubling the sensors allows to achieve higher reliability of operation—while exceeding the threshold value “threshold_YLG_ 2 ”, it is necessary to confirm dangerous situation by two independent vehicle roll rate sensors. 
   It is obvious that embodiments of safety logic presented above may be implemented as electronic circuits provided with suitable comparing, filtering, or summing elements, as well as a software by the suitable algorithm of individual electronic control unit (ECU). 
   It is preferably to separate the main logic from the safety logic through using two independent ECUs, what provides considerable independence of the system. Main logic and the additional safety logic may also be implemented separately in two individual microcontrollers (preferably of different types), that are placed in one ECU unit. 
   An example of such implementation is presented in  FIG. 5 , where two microcontrollers are employed within one ECU unit  31 : the microcontroller of the main unit  2  and the microcontroller of the safety unit  1 . Both units are connected to the I/O block  30 , through which they receive appropriate sensor signals. The output of the main logic  2  is coupled with the input of the AND gate  3  that is built in block  30 . The second input of the gate  3  is coupled with the output of the safety logic  1 . Activation of both logics is required to activate suitable protection device, e.g. an airbag. 
   The safety logic according to the present invention is a very simple, economical and elastic solution, owing to many calibration parameters. It is activated substantially in situations, when the probability of vehicle rollover is significant. During normal driving conditions, for example driving on roughness roads, turns, driving in a straight line or driving uphill, it remains inactive.