Abstract:
A method of controlling a restraint device in a vehicle. The method comprises sensing an acceleration of the vehicle, analyzing the acceleration with at least two independent thresholds, and activating the restraint device when the analyzed acceleration exceeds the at least two independent thresholds.

Description:
BACKGROUND  
       [0001]     Embodiments of the invention relate to vehicle control systems, and more particularly to a vehicle control system to deploy an occupant restraint device.  
         [0002]     Restraint devices such as airbags and seatbelts are, in general, actuated during crashes or possible crashes to protect vehicle occupants from injury. The accuracy and timeliness of deployment and actuation are factors in the effectiveness of restraint devices.  
         [0003]     Some restraint devices are controlled using algorithms that process accelerations measured in various locations of a motor vehicle. The measured accelerations are analyzed using various functions such as integration (to yield velocity), a sum of squares of the measured accelerations, slopes of the measured accelerations, and the like. The outputs of the functions are compared to thresholds that may be constant, depending on factors such as time or physical properties like relative velocity. If the thresholds are crossed, restraint devices are deployed.  
       SUMMARY  
       [0004]     A variety of vehicle conditions may be considered when controlling vehicle restraint devices. A “crash” condition (or “deployment crash” condition) exists when a vehicle has experienced an impact or collision above a certain threshold. In a “crash” condition the vehicle experiences forces that warrant the activation of a restraint device. Another type of condition is an “abuse” condition. An “abuse” condition may exist for a variety of reasons. For example, jarring of the vehicle as the vehicle travels over rough roads may cause an abuse condition to exist. Generally, the existence of an abuse condition does not warrant the activation of a restraint device. Yet another type of condition is sometimes referred to as a “no-deployment-crash” condition. In such a condition, the vehicle may have experienced an impact or collision, but the magnitude of the impact or collision is not sufficient to warrant the deployment of an occupant restraint device.  
         [0005]     The inventors have discovered that one deficiency of known technologies is that crash conditions and abuse conditions are often treated the same way. For example, some algorithms tune thresholds used in them such that neither no-deployment-crashes nor abuse conditions will cross any of the thresholds. (In a no-deployment-crash, the restraint device should not been deployed.) As a result, abuse conditions can adversely impact deployment time during crashes. That is, both abuse and crash conditions are compared to the same thresholds. In such a case, the restraint devices may be deployed when the vehicle is simply experiencing abuse conditions. Or, the restraint devices may be disabled even when the vehicle is experiencing a crash condition because of the inaccuracy of the combined thresholds.  
         [0006]     In one embodiment, the invention provides a method of controlling a restraint device in a vehicle. The method includes determining a vehicle condition that has a value, and retrieving an abuse condition threshold and a deployment condition threshold based on the value of the determined condition. The method then includes generating a restraint device activation signal when the value of the determined condition is below the abuse condition threshold and above the deployment condition threshold.  
         [0007]     Another embodiment of the invention provides a method of controlling a restraint device in a vehicle. The method includes sensing an acceleration of the vehicle, determining a vehicle signal based on the acceleration, and retrieving an abuse condition threshold and a deployment condition threshold based on the acceleration and the vehicle signal. The method also includes comparing a value of the vehicle signal with the abuse condition threshold and the deployment condition threshold, and generating an activation signal based on the comparison.  
         [0008]     Another embodiment provides a method of controlling a restraint device that includes sensing an acceleration of a vehicle, analyzing the acceleration with at least two independent thresholds, and activating the restraint device when the analyzed acceleration exceeds the at least two independent thresholds.  
         [0009]     Yet another embodiment provides an apparatus for controlling a restraint device in a vehicle. The apparatus includes a sensor configured to sense a vehicle condition having values that are indicative of vehicle accelerations. The apparatus also includes a comparator that compares the value with at least two independent thresholds to produce a comparator output, and a signal generator coupled to the comparator. The signal generator generates a deployment signal when the comparator output exceeds the at least two independent thresholds.  
         [0010]     Still another embodiment provides a vehicle. The vehicle includes a restraint device, a sensor to sense a plurality of values indicative of vehicle accelerations, and a processing unit to compare the values indicative of vehicle accelerations with an abuse condition threshold and an independent deployment condition threshold. The processing unit generates a deployment signal when the value is below the abuse condition threshold and above the deployment condition threshold. The vehicle also includes a restraint device that can be deployed upon receiving the deployment signal.  
         [0011]     Other features and advantages of embodiments will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     In the drawings:  
         [0013]      FIG. 1  shows a schematic plan view of a vehicle;  
         [0014]      FIG. 2  shows a block diagram of a control system in the vehicle in  FIG. 1 ;  
         [0015]      FIG. 3A  is a graph of an abuse condition threshold;  
         [0016]      FIG. 3B  a graph of a deployment condition threshold; and  
         [0017]      FIG. 4  is a flow chart of processing carried out in embodiments of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0018]     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” “coupled,” and “mounted” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. In addition, the terms “connected” and “coupled” and variations thereof are not restricted to physical or mechanical connections or couplings.  
         [0019]      FIG. 1  shows a schematic plan view of an exemplary vehicle  100 . The vehicle  100  has four wheels  104 A,  104 B,  104 C and  104 D. The wheels  104 A,  104 B,  104 C and  104 D are connected to two axles  108 A and  108 B, as shown. The four wheels are monitored by a plurality of wheel speed sensors  112 A,  112 B,  112 C and  112 D. The wheel speed sensors  112 A,  112 B,  112 C, and  112 D are coupled to an electronic processing unit (“ECU”)  116 . The vehicle  100  also includes other sensors such as a front bumper sensor  120 , a back bumper sensor  124 , a plurality of side impact sensors  128 , and accelerometers or acceleration sensors  130 A and  130 B. The wheel speed sensors  112 A,  112 B,  112 C and  112 D, the front bumper sensor  120 , the back bumper sensor  124 , the plurality of side impact sensors  128 , and the sensors  130 A and  130 B are shown as individual sensors generically. These sensors  112 A,  112 B,  112 C,  112 D,  120 ,  124 ,  128 ,  130 A, and  130 B can also include multiple sensors in a plurality of sensor arrays that may be coupled to the ECU  116 . Other types of sensors such as thermal sensors can also be used in the vehicle  100 .  
         [0020]     The vehicle  100  also includes a plurality of restraint devices such as front airbags  132  and side airbags  136 . Although  FIG. 1  shows only airbag restraint devices, other types of restraint devices such as seatbelt tensioners, and head and torso airbags can also be used in the vehicle  100 .  
         [0021]     In one embodiment, a control system  200  ( FIG. 2 ) is used to separate non-deployment crash conditions from deployment crash conditions. The control system  200  receives its input from a sensor array  204  that includes the wheel speed sensors  112 A,  112 B,  112 C, and  112 D, the front bumper sensor  120 , the back bumper sensor  124 , the side impact sensors  128 , and the sensors  130 A and  130 B.  FIG. 2  also shows the ECU  116  in block diagram format. Once the outputs from the sensor array  204  have been processed by the ECU  116 , a restraint device  208  can be deployed.  
         [0022]     In one embodiment, each of the sensors  130 A and  130 B detects and monitors a specific condition of the vehicle  100 . For example, the sensors  130 A and  130 B are used to sense a condition of the vehicle that is indicative of an amount of acceleration experienced by the vehicle  100 . In some embodiments, the sensors  130 A and  130 B sense motion of the vehicle  100 . Sensed motions are then transduced and converted into signals that are indicative of acceleration of the vehicle  100 . If the sensors  130 A and  130 B are equipped with any calibration circuitry or microprocessor therein, the motions can be calibrated internally in the sensors  130 A and  130 B. Otherwise, the signals can be converted into calibrated signals by other external processes in a manner known in the art. Furthermore, other sensors such as the front bumper sensor  120 , the back bumper sensor  124 , the side-impact sensors  128  can be used to detect or sense events such as crashes and collisions. Values of the signals output by the sensors  112 A,  112 B,  112 C,  112 D,  120 ,  124 ,  128 ,  130 A,  130 B, or by the sensor array  204  are referred to as sensed values, or values hereinafter.  
         [0023]     The ECU  116  includes a processor  212  that receives the values from the sensor array  204 . The processor  212  then processes the values according to a program stored in a memory  216 . Although the memory  216  is shown as being external to the processor  212 , the memory  216  can also be internal to the processor  212 . Furthermore, the processor  212  can be a general-purpose micro-controller, a general-purpose microprocessor, a dedicated microprocessor or controller, a signal processor, an application-specific-integrated circuit (“ASIC”), or the like. In some embodiments, the control system  200  and its functions described are implemented in a combination of firmware, software, hardware, and the like. To be more specific, as illustrated in  FIG. 2 , the processor  212  communicates with other modules (discussed below). The modules are illustrated as if they were implemented in hardware. However, the functionality of these modules could be implemented in software, and that software could, for example, be stored in the memory  216  and executed by the processor  212 .  
         [0024]     The exemplary ECU  116  includes an analyzer  220  that converts, filters or transforms the values generated by the sensor array  204  from one form to another depending on the application at hand. For example, when the values generated by the sensor array  204  are indicative of an acceleration of the vehicle  100 , the analyzer  220  converts the acceleration value to values such as transformed acceleration. For another example, the analyzer  220  can filter the accelerations into filtered accelerations that may be indicative of a relative velocity of the vehicle  100 . For yet another example, the analyzer  220  can transform the accelerations into a value that is indicative of energy dissipated in the vehicle  100  during the crash. Other transformed values include relative distance displacement, quantized acceleration, absolute-valued acceleration, filtered acceleration, and the like. In some embodiments, the relative velocity of the vehicle is typically determined or obtained by integrating the acceleration detected. Although the analyzer  220  is shown being external to the processor  212 , the analyzer  220  can also be internal as a software or hardware module of the processor  212 .  
         [0025]     Once the values from the sensor array  204  have been analyzed in the analyzer  220 , either one or both of the analyzed values and the unanalyzed values are used to retrieve thresholds stored in the memory  216 . For example, when the unanalyzed values and the analyzed values represent acceleration and velocity respectively, the acceleration and velocity are then used to retrieve a no-abuse condition threshold (or an abuse condition threshold that is similar in nature), and a deployment threshold, detailed hereinafter.  
         [0026]     Referring back to  FIG. 2 , the ECU  116  also includes a comparator  224  that compares the unanalyzed value with a no-abuse threshold  312  ( FIG. 3A ) retrieved from the memory  216  based on the analyzed value with a deployment condition threshold  362  ( FIG. 3B ) retrieved from the memory  216  also based on the analyzed value, as discussed earlier. The outputs of these comparisons are fed to a signal generator  228 . The outputs of the comparisons are further compared. When the unanalyzed value corresponding to the analyzed value is above the no-abuse threshold  312  and above the deployment condition threshold  362 , the signal generator  228  generates a deployment signal to activate the restraint device  208 . Otherwise, when the unanalyzed value corresponding to the analyzed value is either below the no-abuse threshold  312  or below the deployment condition threshold  362 , the signal generator  228  generates a disabling signal that disables the restraint device  208 .  
         [0027]     In some embodiments, the signal generator  228  will only generate an activating signal or deployment signal when the unanalyzed value is above both retrieved thresholds, and will not generate any disabling signal otherwise. In this way, other deployment techniques can also be used to activate the restraint devices. For example, in yet some other embodiments, the signal generator  228  can also generate the activating signal or deployment signal based on a combination of signals generated by other deployment algorithms and the outputs of the comparator  224 . That is, signals from additional deployment techniques are combined and processed in the signal generator  228  to arrive at a final deployment decision.  
         [0028]     In general, the no-abuse condition threshold separates an abuse condition that does not require a restraint device deployment from a no-abuse condition that may require the deployment of a restraint device.  FIG. 3A  shows a no-abuse condition threshold plot  300 . The analyzed values such as the relative velocities are measured along an x-axis  304  and the unanalyzed values such as the accelerations are measured along a y-axis  308 . No-abuse threshold curve  312  generally separates an abuse condition curve  316  from a no-abuse crash condition  320 . The abuse condition curve  316  typically has high oscillatory acceleration peaks. Therefore, the magnitude of the relative velocity is relatively low. The no-abuse crash condition curve  320  typically has no or minimal oscillatory acceleration which results in a relative velocity even for small collision speeds. The no-abuse crash condition  320  therefore crosses the decreasing no-abuse threshold curve  312  while the abuse condition curve  316  does not. If the no-abuse threshold curve is crossed, a no-abuse flag is set. The no-abuse flag is represented by a no-abuse step function  324  in  FIG. 3A . During vehicle operation, an acceleration (or deceleration) is detected. A relative velocity is thereafter obtained from the detected acceleration, in a manner that is detailed hereinafter. If the detected acceleration corresponding to the relative velocity is above the no-abuse threshold curve  312 , the no-abuse condition is recognized, and the no-abuse flag is set. In general, the no-abuse threshold curve  312  is dynamically determined or measured from the analyzed values sensed over different times, the analyzed values generated from the unanalyzed values, and the like. For example, a first analyzed value can be obtained from determining a plurality of unanalyzed values over a first period of time, while a second analyzed value can be obtained from the unanalyzed values over a second period of time. In this way, the analyzed values determined from the two unanalyzed values can be different, thereby yielding different thresholds.  
         [0029]     Similarly,  FIG. 3B  shows a deployment condition threshold plot  350 . The analyzed values such as the relative velocities are measured along a second x-axis  354 , and the unanalyzed values such as the accelerations are measured along a second y-axis  358 . An increasing deployment threshold curve  362  separates a non-deployment crash curve  366  from a deployment crash curve  370 . If a crash occurs, a crash acceleration (or deceleration) is detected. A relative velocity is obtained from the detected acceleration, detailed hereinafter. If the detected acceleration corresponding to the relative velocity is above the deployment threshold curve  362 , a deployment condition is recognized, and a deployment flag is set. The deployment flag is represented by a deployment step function  374  in  FIG. 3B . Furthermore, since the two thresholds  312  and  362  are independent on each other, even when the abuse condition curve  316  crosses the deployment threshold curve, the deployment flag  374  is not set, because the abuse conditions will be correctly identified by the no-abuse threshold plot  300  as an abuse condition. Similar to the no-abuse threshold curve  312 , the deployment threshold curve  362  is dynamically determined or measured from the unanalyzed values sensed over different times, the analyzed values generated from the unanalyzed values, and the like.  
         [0030]     Various unanalyzed values and analyzed values can be used in establishing the thresholds  312  and  362 . For example, the relative velocity as determined by integrating the detected acceleration can be plotted against the detected acceleration as the control value with the thresholds then based on the filtered acceleration. Similarly, the filtered acceleration can be plotted against the relative velocity as a control value, with the thresholds based on the relative velocity, as illustrated in  FIG. 3A  and  FIG. 3B . As another example, the relative velocity or the filtered acceleration can be plotted against a crash time (measured from the beginning of the crash to the end of the crash) as a control value with the thresholds based on the crash time. Other examples for the unanalyzed and analyzed values include the relative displacement as determined by double integration of the measured acceleration. The displacement can also be plotted against the filtered acceleration or the relative velocity as control values.  
         [0031]     It is also possible to use different unanalyzed and analyzed values in the no-abuse condition threshold  312  and the deployment condition threshold  362 . An example can be a filtered acceleration, in which the acceleration is filtered with different filter frequencies for use in the no-abuse condition threshold  312  and the deployment condition threshold  362 . Features or values specifically suitable and/or tuned to separate abuse conditions from crash conditions regardless of their severity may also be employed in the no-abuse condition threshold  312 . Similarly, different unanalyzed and analyzed values suitable to identify the severity of crashes and to separate non-deployment crashes from deployment crashes regardless of the abuse conditions can also be used to establish the deployment condition threshold  362 .  
         [0032]      FIG. 4  includes a flow chart  400  that further illustrates processes that occur in some embodiments including process that maybe carried out by software, firmware, or hardware. As noted, the sensors sense accelerations and other parameters. This is shown at block  404 . Analyzed values such as the relative velocity are determined from the unanalyzed values at block  408  using transformations such as integration in the case of velocity, double integration in the case of relative displacement, frequency filtering in the case of filtered acceleration, absolute valuing in the case of a power related value, and the like. The analyzed value is then used as a control value to retrieve the no-abuse threshold  312  at block  412 , and the deployment threshold  362 , as shown at block  416 . The thresholds  312  and  362  are stored in the memory  204  as look-up-tables  420  and  424  respectively, in some embodiments. Once these thresholds  312  and  362  have been retrieved, the unanalyzed value is compared with the thresholds  312  and  362 , as shown at blocks  428  and  432 , respectively, and simultaneously depending on the applications at hand. When the unanalyzed value is above both thresholds  312  and  362 , a deployment signal is generated as shown at block  436 , which in turn activates the restraint device  208 . However, if the unanalyzed value is below either one of the thresholds  312  and  362 , the restraint device is disabled, and the block  404  is repeated.  
         [0033]     Various features of the invention are set forth in the following claims.