Patent Application
20090085340
This application claims foreign priority benefits under 35 U.S.C. § 119(a)-(d) to EP 07117762.0 filed Oct. 2, 2007, which is hereby incorporated by reference in its entirety.
1. Field of the Invention
The invention relates to a method and a system for limiting the load of a vehicle safety belt in case of an emergency. The method and system comprises means for detecting and predicting the severity of a crash in order to adapt the belt force to the crash conditions.
2. Background Art
The use of belt force load limiters, i.e. a device which limits the restraining force of a safety seat belt in case of a crash or sudden brake, in vehicles has become more and more common today. The purpose of these belt force load limiters is to avoid or reduce injuries to a person seated and belted in a vehicle seat due to an unnecessary hard restraining force from the belt. Until today, there have been suggested several methods and devices for achieving a reduction in the load applied to a body by a safety belt in a crash situation.
EP 734 922 discusses and describes how a belt force limiter is adjusted with respect to the person belted in the seat, e.g. weight and size of the occupant. However, this limiter will only be a limiter for small persons and not for larger persons since the belt limiter works essentially as an adapter for persons belted in the seat according to their weights and does not take into consideration the circumstances of the crash situation.
DE 196 04 483 describes a method which takes into account data from the actual crash situation and intends to adapt the force from the belt to be optimized with respect to the forces from the belt working on the seated person and the permissible extension of the belt.
U.S. Pat. No. 6,513,616 describes an arrangement similar to DE 196 04 483 and which also takes into account circumstances such as the crash violence and adapts the belt force limiting system to be dependent on and cooperating with other safety systems such as an air bag. When the air bag is triggered and has been inflated, the force limiter will start to work and the restraint from the belt is thus reduced.
Even though these systems provide improvements in vehicle safety and disclose different manners of limiting the safety belt force working on an occupant of a seat, there is still a need to improve these systems in order to more efficiently limit the force in an appropriate way. Hence, there is a need for an improved method and system for control of a belt limiting force in a vehicle in order to improve the safety of the occupants.
Disclosed embodiments of the present invention provide a method for controlling an Adaptive Belt Load Limiter (ABLL) for a vehicle safety belt in a vehicle. The embodiments provide early detection of a crash situation and a reliable estimation of the crash scenario such that the ABLL at an early stage is provided with the right control signal. Hence, the disclosed embodiments provide a control system which, by the use of an advanced Closing Velocity Sensor (CVS) system, is able to detect an upcoming crash situation.
Depending on the sensor signals from the CVS, the severity of a crash scenario is estimated by a Restraints Control Module (RCM) which further prepares a control signal or control sequence based on the crash severity estimation. The control signal is sent to an Adaptive Belt Load Limiter (ABLL) and the control signal may reach the ABLL at an early stage, most preferably before an impact or before the impact is sensed by sensors indicating the actual status of the vehicle.
In some cases a control signal may not be sent at an early stage since the desired control is to keep the ABLL at the default level and no control signal is needed. Furthermore, there are cases, i.e. crash scenarios, when there is a desire to use other relevant sensor data (such as accelerometers or other sensors indicating the actual status of the vehicle) which may be used to verify the crash severity estimated by the CSV. However, the CSV sensor data is very useful also in these cases since it provides additional data which make it possible to select a more appropriate control strategy for the ABLL.
The above stated problems are solved by the use of a control method for a belt force limiter which comprises the step of:
The prediction of an impact or accident by a CVS as described above is particularly suitable for controlling the belt load limiter since it is important to be able to accurately determine the appropriate load level before a crash has occurred, as this permits the belt to begin to function at the same instant the crash situation starts, in contrast to an air bag cushion which is intended to be working at a later stage in the accident. Furthermore, the ability to classify the accident by the use of area specific CVS makes it possible to better predict the estimated impact force or the severity of the crash since there is a great difference in an front offset or angled collision compared to a full frontal impact collision. This information may thus be used to adapt the seat belt restraining force. By classifying different types of crashes and adapting the belt force load accordingly, it may be possible to avoid injuries to a belted occupant that may be caused by unnecessary large belt restraining forces.
According to one specific embodiment of the invention, the one or several CVS covers three different spatial areas and are able to distinguish the sensed signals from each area corresponding to a middle front area, a left front area and a right front area. An example of a suitable sensor arrangement is for example disclosed in US 2007/0032952.
According to another embodiment of the invention, which may be used alone or together with the foregoing embodiment, the RCM is provided with ports for data input signals corresponding to vehicle speed and/or acceleration such that a crash severity estimation may be performed based on the sensor signals from the different areas covered by the Closing Velocity Sensor(s) along with the vehicle speed and/or vehicle acceleration.
According to another embodiment of the invention, which may be used alone or together with any of the foregoing embodiments, the RCM is uses a Look Up Table (LUT). The LUT comprises a crash type classification scheme, such that different crash types are classified based on the sensor signals from the Closing Velocity Sensor(s) corresponding to the detection of an object in the different areas and a control signal is generated by the RCM by using said LUT. If for example the CVS is configured to indicate an object in three different regions (front left, front center and front right) the LUT may include different classification such as centerpole crash (only the front center area indicates an object), offset/angled right crash (only the front right area indicates an object), offset/angled left crash (only the front left area indicates an object) and full frontal crash (all three areas or at least two of the areas are indicated). Of course it would also be possible to differentiate the different conditions representing the full frontal crash into further divided classification depending on if an object is detected in 2 or 3 areas or to combine the offset/angled right and left as the same class of crash. Still further, it may also be possible to differentiate the control signal for the left respectively right seat belt load limiters when there is an offset/angled crash situation such that different control signals are sent to the respective left and right side belt load limiters since the impact force is different on the different sides. Hence, depending on the numbers of different areas sensed the CVS, a number of different crash classifications may be done and appropriate control signals for the different types of crashes may be tried out by crash tests and/or simulations such that the RCM is tuned to best control the ABLL. To be noted, the control signal which is obtained from the LUT may either be such that it may be directly sent to the ABLL or may be further processed by the RCM before it is sent to the ABLL.
In another embodiment which may be used together with the foregoing embodiment, the RCM is provided with or connected to several sets of LUTs whereof the appropriate LUT to be used is selected by using at least one of a set of parameter including vehicle speed, vehicle acceleration, closing velocity of an approaching object or weight of the belted occupant. Hence, there are different LUTs, which are selected depending on desired parameters concerning the vehicle and the environment, such that when the relevant conditions of the crash scenario is known or estimated, the right LUT is selected from which a relevant parameter is retrieved to either be further processed by the RCM for creating a control command for the ABLL or used directly as a control signal to the ABLL.
According to still another embodiment of the invention, which may be used together with any of the previous embodiments described, the control signal from the RCM to the ABLL is a signal which directs a desired length of the safety belt pay out at a standard load level before the force limiter is activated. One way of deciding the belt pay out length is to measure the number of revolutions the roll has made. The control signal may also indicate a certain time period to lapse before the belt force limiter is activated but in general it is considered to be more accurate to control the length of the belt which has been paid out. This control system is in particular designed for a seat belt construction with an ABLL which irreversibly changes the belt force limiting action from a standard state (i.e. where no extra belt force limitation is added) to a second state where a predefined belt force limitation is added, i.e. in the cases where it is only possible to switch between two different belt restrain forces. However, the strategy of controlling the belt pay out length as the relevant parameter for switching between different restraint force levels would work for a load limiter able to switch between several load limitation levels as well as for a load limiter which may both rise and lower the belt restrain forces.
The invention further relates to a belt force limiting system for performing the method described above, said system comprising one or several Closing Velocity Sensor(s) (CVS) for detecting objects in front of the vehicle. The term “in front of the vehicle” means that the objects need not to be directly ahead of the vehicle but may also be ahead of the vehicle and offset to either side. The system further comprises a Restraints Control Module (RCM) receiving sensor input data from the CVS. The RCM uses the sensor input data in order to generate an output control signal. The control signal also be dependent on other parameters than the CVS signals. The system further comprises an Adaptive Belt Load Limiter (ABLL) connected to the RCM. The ABLL is adapted to receive the output control signal from the RCM and effectuate the belt load limiting action. The one or several Closing Velocity Sensor(s) is capable of sensing the presence of an object in at least two different spatial areas, e.g. in the middle part in front of the vehicle or angled at the right or left side in front of the vehicle. The CVS signals from the different areas or zones are kept separate such that area specific signals are generated and the RCM is adapted to generate a control signal to the ABLL which is dependent on the sensed condition in the at least two spatial areas. Hence, the system shall enable the differentiating of signals originating from different areas and take into consideration from which area a signal is originating when generating the control signal.
According to one embodiment of the belt force limiting system, the one or several Closing Velocity Sensor(s) covers three different spatial areas and is able to distinguish the sensed signals from each area corresponding to a middle front area, a left front area and a right front area. It is of course possible to use further sensors or modify the existing sensors in order to specify further, more narrow areas or to cover a larger total zone.
According to another embodiment of the belt force limiting system, which may be used together with the earlier embodiment or alone, the system also comprises speed and/or acceleration sensors which are connected to the Restraints Control Module. The input signals from these sensors, in addition to the signals from the CVS, may also be used for generating the control signal for the Adaptive Belt Load Limiter (ABLL).
According to another embodiment of the belt force limiting system, which may be used together with any of the earlier embodiments or alone, the RCM uses one or several Look Up Tables (LUT). The LUTs comprises a crash type classification scheme, such that different crash types are classified based on the sensor signals from the CVS corresponding to the detection of an object in the different areas covered by the CVS. Optionally, different LUTs are used depending on at least one of the following parameters: vehicle speed, vehicle acceleration, closing velocity of an approaching object, and weight of the belted occupant.
According to another embodiment of the belt force limiting system, which may be used together with any of the earlier embodiments or alone, the RCM is adapted to generate a control signal to the ABLL which controls the length of safety belt pay out at a desired level before the force limiter is activated.
In
The CVS 102 is connected to the RCM 103 such that sensor signals from the CVS 102 may be transmitted to the RCM 103 through a connection 105. The connection may either be a wire connected to an output port on the CVS 102 and an input port on the RCM 103 or a wireless connection having a sender connected to the CVS 102 and a receiver connected to the RCM 103. It may of course also be possible to have a two way connection or a second connection such that signals may be sent from the RCM 103 to the CVS 102, e.g. control signals in order to set desired parameters for the CVS such as sample interval and/or to control the shape, size and overlapping of different areas.
The RCM 103 is further connected to the ABLL 104 by a connection 106 such that control signals generated by the RCM 103 may be transmitted to the ABLL 104. The connection may either be a wire connected to an output port on the RCM 103 and an input port on the ABLL 104 or a wireless connection having a sender connected to the RCM 103 and a receiver connected to the ABLL 104. It may of course also be possible to have a two way connection or a second connection such that signals may be sent from the ABLL 104 to the RCM 103, e.g. signals sensing a relevant parameter of the ABLL such like the numbers of revolutions (or more exact, the turning angle) of a belt roll corresponding to the belt pay out length, in order to use the relevant information from the ABLL to influence the control signal.
In this figure, the CVS 102, the RCM 103 and the ABLL 104 are represented as separate units or boxes. It will be apparent to a person skilled in the art that, for example, the CVS 102 and the RCM 103 may be located in the same housing or the RCM and the ABLL 104 may be located in a single housing. Furthermore, the RCM 103 need not to be a separate unit but may be a part of a vehicle safety system including numbers of other control functions.
The system 101 may further have a number of additional features added to the basic features in this drawing representing an embodiment of the invention. It may for example be added further input parameters, such as vehicle speed, acceleration data from accelerometers, weight of an occupant of a seat, etc., these parameters representing data input which may be relevant for controlling the load of a belt in the vehicle. This may for example be achieved by connecting the RCM to a Local Area Network (LAN) or a Controller Area Network (CAN). There may also be a number of different control algorithms used depending on these input parameters which may be used in addition to the CVS. It is also advisable to use some kind of control function for the sensor signals from the CVS such that the signals represent a certain confidence level.
In
The values contained in the LUT of
It is of course also possible to use some arithmetic formula for calculating the control signal instead of using LUT.
The windscreen 303 should be fabricated from a material which allows three pulsed beams of infrared radiation 305a, 305b, 305c to propagate through the windscreen 305 and be subsequently reflected from oncoming objects in front of the vehicle 301 to generate corresponding reflected radiation which is received back at the CVS 302. By one or more of pulse-echo signal detection techniques and optical Doppler shift techniques, closing velocities of the oncoming objects can be computed at the CVS 302. By sending the signals at different times and/or having different characteristics of the signal sent, it may be possible to distinguish the different signals such that information concerning in which area or areas an upcoming object is detected.
Implementation and operation of the CVS 302 will now be described in greater detail. The CVS 302 is designed to be optionally mounted at a relatively high position onto or close to the windscreen 305 of the vehicle 301. Such a mounting position potentially provides an optimal field of view of a region in front of the vehicle 301, namely in a region wherein one or more potential impact hazards are likely to be encountered. The sensor 302 employs the three beams 305a, 305b, 305c to provide a sensing field having an approximate lateral angular extent of θ1=45° as depicted in
In operation, the CVS 302 provides distance and velocity information regarding one or more oncoming objects in front of the vehicle 301 at an update rate of substantially 100 Hz, namely at 10 millisecond intervals. When measuring position and velocity, a sensing cycle is optionally implemented in the sensor 302 for each of the sectors. The cycle commences by each laser in the sensor 302 providing a burst of laser radiation for emission from the sensor 302. The burst has a duration of 2 milliseconds and comprises 100 pulses of radiation, wherein each pulse has a duration of substantially 30 nanoseconds. For each pulse emitted from the sensor 302, the aforesaid light sensitive diodes are scanned for substantially 100 nanoseconds to derive reflected radiation signals. Thereafter, according to one embodiment, a sum of all intensities in the reflected radiation signals are used for performing a distance calculation, the calculation optionally being implemented using a simple “center of mass” approach, thereby simplifying computation required. From a determination of distance as a function of time, a closing velocity can be derived. Thus, in overview, the CVS 302 employs time-of-flight (TOF) measurements of IR-laser pulses to calculate relative distances between the vehicle 301 and one or more potentially hazardous objects in front of the vehicle 301; measured distance changes within a well-defined period of time are used to generate relative velocity data and hence aforesaid closing velocity data for the Automatic Belt Load Limiter collision management system. In order to use the sensor data for classification of different crash types, it is possible to distinguish the sensor data received from each area.
However, it will be appreciated that the CVS 302 can also be implemented using optical or radar Doppler techniques, wherein a portion of reflected radiation from one or more oncoming objects in a direction of travel of the vehicle 301 is mixed at the sensor 302 with a portion of radiation emitted from the sensor 302 towards the one or more oncoming objects to generate a Doppler beat signal from which a measure of closing velocity of the one or more objects to the vehicle 301 can be derived.
It will be appreciated that embodiments of the invention described in the foregoing are susceptible to being modified without departing from the scope of the invention.
Although application of the present invention in the context of a road vehicle is described in the foregoing, it will be appreciated that the present invention is also applicable to trucks, lorries, vans, motorcycles, motorbikes and scooters to mention some examples. The term “vehicle” in the accompanying claims is therefore to be construed to include at least such a range of vehicle types.
While the best mode for carrying out the invention has been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 07117762.0 | Oct 2007 | EP | regional |
