Method for controlling an occupant protection system of a vehicle and control unit

Abstract

Method (800) for controlling an occupant protection system (204) of a vehicle (200), wherein the method (800) comprises the following steps: Reading in (810) at least one vehicle acceleration value (712) representing an acceleration of the vehicle (200) and at least one model parameter (714) of an occupant model (214) by which an occupant (212) of the vehicle (200) is represented by at least two; Processing (820) the vehicle acceleration value (712) and the model parameter (714) to determine at least one motion parameter (722) related to the two; and Generating (830) a control signal (222) to control the occupant protection system (204) using the motion parameter (722). characterized in that, in the reading step (810), a parameter is read in as the model parameter (714) which is assigned to a head mass point (216) representing a head and / or neck of the occupant (212) and / or an upper body mass point (218) representing an upper body of the occupant (212) and / or a lower body mass point (220) representing a lower body of the occupant (212), and in the processing step (820), the vehicle acceleration value (712) and the model parameter (714) are processed to determine a parameter related to the head mass point (216) and / or the upper body mass point (218) and / or the lower body mass point (220) as the motion parameter (722).

Description

State of the art

[0001] The invention is based on a device or a method according to the class of the independent claims. The present invention also relates to a computer program.

[0002] Since the introduction of mandatory seat belt use in 1977, as well as the introduction of seat belts in the 1970s and airbags in the 1980s, the number of fatalities has been significantly reduced from 21,000 to 3,500 annually. Along with other restraint systems, seat belts are responsible for almost 75 to 80 percent of the restraint effect on occupants in the event of an accident. A further development in this area was the introduction of systems with irreversible belt pretensioners in the mid-1980s. In recent years, work has been done on systems designed to prevent accidents and mitigate their severity. Systems ranging from interior sensing to so-called pre-crash detection systems have been developed.

[0003] To couple the occupant to the vehicle's deceleration as early as possible in the event of an accident, excess slack, e.g., from thick clothing or for comfort reasons, can be removed by pyrotechnic belt tensioning after the collision begins. Recently, reversible mechanical actuators have been used as belt tensioners. These can be activated in a critical driving situation or by environmental sensing. They can very effectively eliminate excess slack because they are activated before the collision. If a collision does occur, the pyrotechnic belt tensioning can also be activated. This can ensure even earlier coupling of the occupant.

[0004] The targeted coupling of the occupant to vehicle deceleration can result in very severe loads for the occupant, primarily in the head and thorax area. These load peaks can be reduced, for example, by belt force limiters. The principle is based on the release of belt webbing once a certain belt force has been reached, for example a force level in the range of 2 to 3 kN. In general, the force can be limited using mechanical energy conversion principles, for example through destruction, such as tear seams on the belt webbing or tear plates, through deformation, such as through torsion bars in the retractor, sometimes even in multiple stages, or through friction, for example through multi-disc brakes. The aim is to ensure that energy is absorbed by increasing forward displacement of the occupant while the belt force remains constant, i.e. that a front airbag takes over from the occupant from the belt system at a certain point in time, such as after 40 to 60 ms.During a collision, the occupant's kinetic energy should be distributed as effectively as possible between the components of the occupant protection system and the interior. Current systems reduce belt force, for example, using a mechanism based on a coupled torsion bar or a wedge brake.

[0005] DE 102 46 055 A1 discloses a device in which the restraint devices in a vehicle are triggered in the event of an accident depending on the movement of the vehicle's occupants. This system records the occupant's weight distribution to determine their seating position. A similar approach is pursued in DE 103 45 726 A1.

[0006] Other documents from which it is known to detect the movement of a vehicle occupant in order to control the restraint systems are DE 10 2008 002 243 A1, DE 10 2009 000 656 A1, DE 10 2009 012 407 B3 and DE 10 2014 000 842 A1. Disclosure of the invention

[0007] Against this background, the approach presented here presents a method for controlling a vehicle occupant protection system, a control unit that uses this method, and finally a corresponding computer program according to the main claims. The measures listed in the dependent claims enable advantageous refinements and improvements of the device specified in the independent claim.

[0008] A method for controlling an occupant protection system of a vehicle is presented, the method comprising the following steps: Reading in at least one vehicle acceleration value representing an acceleration of the vehicle and at least one model parameter of an occupant model by which an occupant of the vehicle is represented by at least two, in particular three, mass points; Processing the vehicle acceleration value and the model parameter to determine at least one motion parameter related to the two, in particular three, mass points; and Generating a control signal for controlling the occupant protection system using the movement parameter.

[0009] An occupant protection system can be understood as a system consisting of a plurality of reversible or irreversible restraint devices for protecting a vehicle occupant in the event of a collision. A restraint device can be, for example, a seat belt, an airbag, a belt tensioner, or a seat. A vehicle acceleration value can be understood as a measured vehicle acceleration value. As an alternative to the measured vehicle acceleration value, a predicted acceleration value can also be used for predictions. This predicted value can either be based on previous acceleration values ​​or be determined based on environmental sensors (radar, video, lidar, etc.) based on a foreseeable accident. An occupant model can be understood as a simplified calculation model for simulating the actual movement of the occupant during a collision.For example, the occupant model can be a spring-damper model, through which the two, in particular three, mass points are linked to one another, taking into account certain spring or damping constants. The occupant model can, for example, be designed as a differential equation model to describe a respective movement of the two, in particular three, mass points in three-dimensional space. A model parameter can be understood, for example, as a parameter representing the occupant, such as a mass, a size, or an age of the occupant, or another variable characterizing the occupant.

[0010] For example, the model parameter can represent a respective mass of the two or three mass points or a respective position of the two or three mass points relative to one another or with respect to a common coordinate system. The position of the two or three mass points can be defined, for example, by a length of imaginary connecting lines between the two or three mass points or an angle between the imaginary connecting lines. Alternatively or additionally, the model parameter can be a parameter of a seat, a belt (e.g., a belt length or force), an airbag (e.g., an inflation pressure or airbag volume), an instrument panel, or a steering wheel of the vehicle. The model parameter can be vehicle- or component-specific and, for example, be provided in advance by a respective manufacturer.Thus, the model parameter can be determined once in advance, for example, eliminating the need to determine the model parameter during vehicle operation. Data obtained in crash tests, for example, can be used to determine the model parameter. Alternatively or additionally, the model parameter can be determined, checked, or adjusted using at least one vehicle sensor, such as an environment sensor, an interior sensor, a seat position switch, or an airbag pressure sensor, particularly during a collision, in order to be able to take the actual course of the collision into account when activating the occupant protection system.

[0011] The two or three mass points can, for example, each be assigned to a different part of the occupant's body, such as a head and neck area, an upper body and a lower body of the occupant.

[0012] A motion parameter can be understood, for example, as a respective acceleration, a respective speed or a respective path of the two, in particular three, mass points.

[0013] The approach presented here is based on the finding that, using an occupant model that simulates a vehicle occupant or components of a vehicle's occupant protection system as a model of at least two, particularly three, mass points assigned to the occupant, the movement of the occupant in a vehicle collision can be determined quickly and reliably with relatively little computational effort based on a modeled movement of the two, particularly three, mass points. Depending on this, the vehicle's restraint devices can be optimally controlled.

[0014] The approach described here makes it possible to efficiently and accurately describe complex-world accident scenarios and, based on this, achieve the greatest possible protection for vehicle occupants in real-life accidents. Previous approaches focus primarily on specific load cases that can be verified by crash tests such as Euro NCAP, US NCAP, FMVSS208, or AZT. Due to their small number, these crash tests are unable to provide an adequate description of real-life accidents. Complex occupant models make it possible to achieve optimal protection in areas that deviate from the clearly defined load cases of the crash tests.

[0015] Initially, control can be performed conventionally according to predefined rules within a range of clearly defined crash test load cases, while model-based interpolation is only performed in significantly different load cases. In a final development stage, for example, the restraint devices are controlled in every case without special consideration of the crash test load cases. An optimal control should then be found for these cases as well, based on the occupant model.

[0016] In contrast, the approach presented here makes it possible to describe the forces acting on the occupant and the resulting movement and kinematics based on a complex occupant model. This results in the advantage of reliable occupant position determination at any time during an accident, as well as reliable control of the restraint devices present in the vehicle based on this position determination. Advantageously, an occupant model, such as the one described here, can be adapted to a vehicle interior using a few parameters, while the occupant's internal kinematics remain independent of the vehicle.

[0017] Very simple models are unable to adequately describe occupant movement during an accident, as occupant movement differs significantly from the movement of a free-flying mass. Determining occupant position using interior sensors, such as an interior camera or ultrasonic sensors, can quickly reach its limits, as for a typical accident duration of approximately 100 ms, an interior camera with a typical frame rate can only deliver three images. The repetition rate of conventional ultrasonic sensors is in a similar range.

[0018] The interior sensors are generally too slow to track the occupant movement during the accident, but can be very suitable, for example, to determine the initial conditions for the occupant model.

[0019] Using the approach presented here, the gap between very simple models, such as free-mass models, and very complex numerical models, such as those based on the finite element method or multi-body dynamics, where the simulation of a single accident can take several hours to several days, can now be closed. For example, a reference implementation of the approach presented here in Matlab allows calculations on standard PCs within a few milliseconds, thus enabling sufficiently fast calculations even on control units with low computing power.

[0020] Approaches are known that either determine the forward displacement of a free-flying mass based on the second integral or determine more precise information about the occupant position with the aid of interior sensing systems. However, since the second integral for a free-flying mass does not accurately reflect the occupant's condition, as it does not take into account the belt system, the airbag, and the occupant's internal mechanical structure, significant errors can occur when calculating the forward displacement. Such errors can be avoided using the approach presented here. Furthermore, the approach presented here offers the advantage of eliminating the need for interior sensing.

[0021] An overriding advantage of the approach presented here is the increased occupant safety in the event of a vehicle collision, as well as the reduction of occupant load and thus injury severity, even in cases where a collision can no longer be avoided and a distinct pre-crash phase with occupant movement is present. Furthermore, the approach described here enables a precise estimation of the occupant position during the crash phase, for which imaging techniques, for example, are less suitable for technical and economic reasons. A further advantage is the easy adaptability to different occupant characteristics such as mass, height, proportions, gender, or age. This makes the approach presented here suitable for application.Furthermore, the approach described here makes it possible to continuously correct a prediction result, for example by feeding in current measured values ​​during an accident, such as acceleration or a crash pulse, so that errors can be reduced compared to purely predictive models. The approach presented here also allows for the coordinated deployment of different restraint systems and thus the development of the full effectiveness of all available actuators not only for standard crash cases, but also in particular for real accident scenarios. Depending on the embodiment, the approach presented here makes it possible to react to changing external conditions even after the restraint systems have been deployed, such as the deployment of an airbag, and to adapt the state of the restraint systems if necessary. In this way, the load on the vehicle occupant can often be reduced compared to a conventional system in these cases.The occupant model, as the subject of the approach presented here, also enables a post-crash assessment of the occupant, which can provide useful information for a secondary crash, or the provision of a driver for individual occupant safety, also known as Individual Occupant Safety (IOS), or an enabler and motivator for adaptive restraint systems such as an adaptive airbag, an electric motor retractor, or an adaptive belt force limiter. The occupant model can also be used to provide feedback to the occupant, for example, to signal a safe location during partially or fully automated driving functions.

[0022] According to one embodiment, in the reading step, a parameter can be read in as the model parameter, which can be assigned to a head mass point representing a head and / or neck of the occupant, an upper body mass point representing an upper body of the occupant, a lower body mass point representing a lower body of the occupant, or a combination of at least two of the aforementioned mass points. Accordingly, in the processing step, the vehicle acceleration value and the model parameter can be processed to determine a parameter related to the head mass point, the upper body mass point, or the lower body mass point as the movement parameter. This allows the movement of individual body parts of the occupant to be simulated.

[0023] The method may further comprise a step of determining at least one restraining force acting on the occupant using the vehicle acceleration value or, additionally or alternatively, the model parameter. In the processing step, the motion parameters may be determined taking the restraining force into account. A restraining force may be understood as a force that counteracts a movement of the occupant caused by a deceleration of the vehicle. For example, the restraining force may be exerted on the occupant by a belt, a seat, or an airbag. This embodiment allows the occupant's movement to be determined in a particularly realistic manner.

[0024] According to a further embodiment, the restraining force can be determined with respect to at least one of the three mass points in the determining step. This enables a simple, rapid, and reliable determination of the restraining force.

[0025] It is advantageous if, in the determining step, a force exerted on the occupant by a belt, a seat, or an airbag of the vehicle, or by a combination of at least two of the aforementioned components of the occupant protection system, is determined as the restraining force. Additionally or alternatively, a neck force of the occupant can be determined as the restraining force in the determining step. This allows the restraining force to be determined based on easily provided model parameters.

[0026] Furthermore, the method can include a step of comparing the restraining force with a reference force. In the generating step, the control signal can be generated depending on the result of the comparison. The reference force can, for example, represent a maximum or minimum restraining force. Depending on the result of the comparison, the control signal can be generated, for example, to increase or decrease the restraining force by controlling a corresponding restraining means of the occupant protection system. This embodiment allows the restraining force to be changed in a targeted manner.

[0027] In addition, the control signal can be generated in the generating step to increase the length of the belt by unwinding the belt if the comparison shows that the restraining force is greater than the reference force. This can prevent occupant injuries caused by excessively tight belt webbing.

[0028] According to a further embodiment, in the reading step, environmental information representing the surroundings of the vehicle or, additionally or alternatively, interior information representing the interior of the vehicle can be read in. Environmental information can be understood as information provided by an environmental sensor such as a camera, an ultrasound, an infrared, or a laser sensor of the vehicle. Interior information can be understood, for example, as information relating to the occupant, a seat setting, a seat occupancy, or a belt status. The interior information can be provided by a corresponding interior sensor system of the vehicle. Accordingly, in the processing step, the movement parameters can be determined using the environmental information or the interior information, or both.This design allows the motion parameter to be determined in a particularly realistic manner. For example, the motion parameter can be continuously adjusted to the actual collision course. This allows the occupant's safety to be further increased by appropriately controlling the occupant protection system.

[0029] This method can be implemented, for example, in software or hardware or in a mixture of software and hardware, for example in a control unit.

[0030] The approach presented here further provides a control unit configured to perform, control, or implement the steps of a variant of a method presented here in corresponding devices. This embodiment of the invention in the form of a control unit also allows the problem underlying the invention to be solved quickly and efficiently.

[0031] For this purpose, the control unit can have at least one computing unit for processing signals or data, at least one memory unit for storing signals or data, at least one interface to a sensor or an actuator for reading sensor signals from the sensor or for outputting control signals to the actuator, and / or at least one communication interface for reading or outputting data embedded in a communication protocol. The computing unit can be, for example, a signal processor, a microcontroller, or the like, wherein the memory unit can be a flash memory, an EPROM, or a magnetic storage unit.The communication interface can be designed to read in or output data wirelessly and / or wired, wherein a communication interface that can read in or output wired data can read this data, for example, electrically or optically from a corresponding data transmission line or output it to a corresponding data transmission line.

[0032] In this context, a control unit can be understood as an electrical device that processes sensor signals and outputs control and / or data signals depending on them. The control unit can have an interface that can be implemented in hardware and / or software. In a hardware implementation, the interfaces can, for example, be part of a so-called system ASIC, which contains a wide variety of functions of the control unit. However, it is also possible for the interfaces to be separate integrated circuits or to consist at least partially of discrete components. In a software implementation, the interfaces can be software modules that are present, for example, on a microcontroller alongside other software modules.

[0033] In an advantageous embodiment, the control unit controls the vehicle. For this purpose, the control unit can access sensor signals such as acceleration, pressure, steering angle, or environmental sensor signals. Control is provided via actuators such as brake or steering actuators or an engine control unit of the vehicle.

[0034] Also advantageous is a computer program product or computer program with program code that can be stored on a machine-readable carrier or storage medium such as a semiconductor memory, a hard disk memory or an optical memory and is used to carry out, implement and / or control the steps of the method according to one of the embodiments described above, in particular when the program product or program is executed on a computer or a device.

[0035] Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. It shows: Fig. 1 a diagram schematically depicting a real accident scenario as a function of a mass and a change in speed of a vehicle; Fig. 2 a schematic representation of a vehicle with a control unit according to an embodiment; Fig. 3 shows an overall diagram of an occupant protection system for control by a control unit according to an embodiment; Fig. 4 a schematic representation of an occupant model for determining an occupant movement by a control unit according to an embodiment; Fig. 5 shows a schematic representation of occupant elements of an occupant model for determining an occupant movement by a control unit according to an embodiment; Fig. 6 is a flowchart of calculations within the framework of an occupant model for determining an occupant movement by a control unit according to an embodiment; Fig. 7 a schematic representation of a control device according to an embodiment; and Fig. 8 a flowchart of a method according to an embodiment.

[0036] In the following description of advantageous embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and having a similar effect, whereby a repeated description of these elements is omitted.

[0037] Fig. Figure 1 shows a diagram schematically depicting a real-world accident scenario as a function of a vehicle's mass m and a change in speed Δv. It depicts an accident scenario in a real, complex world 100, simulated by crash tests 102, such as NCAP tests, with associated interpolation curves 104, which serve to describe scenarios using a corresponding model.

[0038] Fig. Figure 2 shows a schematic representation of a vehicle 200 with a control unit 202 according to one exemplary embodiment. The control unit 202 is configured to control an occupant protection system 204 of the vehicle 200.

[0039] By way of example, the occupant protection system 204 comprises an airbag 206 and a belt force limiter 208 for limiting the belt force acting on a belt 209. The vehicle 200 is about to collide with an object 210, in this case a tree. To actuate the occupant protection system 204, the control unit 202 determines a movement of an occupant 212 of the vehicle 200 caused by the collision of the vehicle 200 using an occupant model 214 and a current acceleration of the vehicle 200, which is in accordance with the Fig. 2 involves a deceleration of the vehicle 200. By way of example, the occupant 212 is represented by the occupant model 214 by at least two, in particular three, interconnected mass points, here by a head mass point 216 assigned to a head region of the occupant 212, an upper body mass point 218 assigned to an upper body of the occupant 212, and a lower body mass point 220 assigned to a lower body of the occupant 212. The control unit 202 uses the current acceleration of the vehicle 200 and suitable parameters of the occupant model 214, also referred to below as model parameters, to model the movement of the occupant 212 based on a movement of the two, in particular three, mass points 216, 218, 220. Example directions of movement of the two, in particular three, mass points 216, 218, 220 are schematically illustrated by four arrows.The model parameters are determined, for example, through crash tests and stored in the control unit 202. Additionally, the model parameters can be adapted to the actual course of an accident using measurements from sensors of the vehicle 200. Depending on the movement of the occupant 212 determined using the occupant model 214, the control unit 202 generates control signals 222 for controlling the components of the occupant protection system 204, here the airbag 206 and the belt force limiter 208. This allows the occupant protection system 204 to be controlled with minimal computational effort and thus particularly quickly.

[0040] Optionally, the control unit 202 is connected to an environment sensor 224 for detecting the environment of the vehicle 200 in order to read in environment information 226 provided by the environment sensor 224 and representing the object 210. According to this exemplary embodiment, the control unit 202 is configured to determine the movement of the two, in particular three, mass points 216, 218, 220 with additional use of the environment information 226.

[0041] According to one exemplary embodiment, the control unit 202 determines the respective movements of the two, in particular three, mass points 216, 218, 220, taking into account at least one restraining force exerted on the occupant 212 by the occupant protection system 204. The restraining force is exerted, for example, by the airbag 206, the belt 209, or a seat 228 occupied by the occupant 212. The control unit 202 determines the restraining force, in particular, using the model parameters. For example, the control unit 202 is configured to activate the belt force limiter 208 when the restraining force exceeds a predetermined reference force.

[0042] Fig. 3 shows a representation of an overall scheme of an occupant protection system 204 for control by a control unit 202 according to an embodiment, such as a control unit as described above with reference to Fig. 2. Shown are a block 300 representing occupant information, a block 302 representing the occupant model, a block 304 representing actuator control, a block 306 representing a restraint control strategy, and a block 308 representing energy management. The directions of signal flow between the individual blocks are marked with arrows.

[0043] The occupant protection function is represented by an overall system consisting of a higher-level control instance that releases the use of certain restraint devices, for example in groups, based on external conditions, and the combination of occupant model and actuator control, which negotiate an optimal deployment strategy in a particularly iterative process and taking into account existing occupant parameters.

[0044] The occupant model is designed as a differential equation model, which, depending on the specific implementation, is solved analytically or as a numerically calculated occupant simulation. The occupant model represents a three-dimensional model that describes the occupant's complete movement in space.

[0045] Fig. 4 shows a schematic representation of an occupant model 214 for determining an occupant movement by a control unit according to an embodiment, for example by a previously determined based on the Fig. 2 and Fig. 3 described control unit.

[0046] According to this exemplary embodiment, the occupant model 214 is designed as a spring-mass-damper model to represent the occupant movement in an accident. For example, the focus is on a frontal collision. The occupant model 214 comprises the two, in particular three, mass points 216, 218, 220 with the masses m h , m t and m l. The lower body mass point 220 represents the lower body up to the pelvis, the upper body mass point 218 the upper body with arms and the head mass point 216 the head of the occupant. These are point masses that are connected to each other via spring-damper links. The connection between the pelvis and upper body (thorax) is fixed in length but rotatable. In the model, the pelvis only moves one-dimensionally in the x-direction, which here corresponds to the direction of travel of the vehicle. Movements in the z-direction (vertical axis) and y-direction (transverse direction) are not possible. The upper body is connected to the pelvis and designed as a stationary pendulum, i.e. the connection is rigid but rotatable. The length of this connection corresponds, for example, to the distance between the upper body's center of gravity and the pelvis in humans, as known from the literature.

[0047] The two mass points 218, 220 are further coupled to the elastic belt 209. Also shown is the airbag 206 with a gas volume V and a gas pressure p. The two variables V, p are influenced by two pistons 400, 402 acting on the airbag 206, with a first piston 400 representing a contact surface of the head with the airbag 206, and a second piston 402 representing a contact surface of the upper body with the airbag 206. An outlet direction of the airbag 206 is indicated by an arrow.

[0048] The shoulder point is also located on the axis from the pelvis to the upper body's center of gravity, but further away from the pelvis. This distance is also known from the literature.

[0049] The upper body is connected to the head at the shoulder point. The connecting element from the shoulder point to the head's center of mass is designed as a combined spring-damper element and a torsion spring, meaning that a change in length and angle is possible, but is restorable by internal forces. To determine neck stiffness values, the spring constants of a Hybrid III dummy, such as those used in crash tests to model human bodies, are used.

[0050] Fig. Figure 5 shows a schematic representation of occupant elements of an occupant model 214 for determining occupant movement by a control unit according to an embodiment. The occupant model 214 essentially corresponds to an occupant model as shown in Fig. 4 is outlined. In Fig. 5 additionally shows various model parameters of the occupant model 214, as they are used in the motion equations described below to determine the occupant movement.

[0051] An input variable for the calculation using the occupant model 214 is, for example, a crash pulse, specified in sampled form. The crash pulse is transferred in one piece, so that the simulation is calculated completely and immediately. Alternatively, the data points are transferred to the occupant model 214 directly after a measurement in the vehicle, and the corresponding current occupant movement is calculated from them. In each case, the times t k known, as well as the vehicle acceleration values ​​a Fz (k) with the corresponding time values ​​t(k) strictly monotonically increasing with k. Thus, the smallest representable time step is dt(k) = t(k)-t(k-1). Furthermore, for k, 1≤k≤K with k, K ∈ N.

[0052] Starting with the vehicle acceleration values, the vehicle motion is first calculated. For this purpose, the vehicle acceleration values ​​are summed and an integration constant is chosen such that the final velocity is zero, i.e. vFz(k)=∑l=1kaFz(l)−vFz(K).

[0053] By further summation the vehicle position is determined: SFz(k)=∑l=1kvFz(l)−SFz(K).

[0054] Here too, the integration constant is chosen so that the final position s Fz (K) = 0.

[0055] Depending on the specific implementation, the crash pulse is specified explicitly or determined generically. In this case, an initial velocity is reduced via a sinusoidal deceleration pulse. The deceleration is aFz(k)={amax⋅12(1−cos2πtτ)0 with the maximum delay amax=2v0τ and the pulse duration τ. For typical load cases, i.e., initial speeds in the range of approximately 50 km / h, the pulse duration is in the range of approximately 120 ms.

[0056] For the purpose of describing the occupant, it is divided into two, or rather three, elements. These two, or rather three, elements are the pelvis and legs, the upper body with arms, and the head. These elements are represented by the point masses m p for the legs, mt for the upper body and m h for the head, which are connected to each other. The connection between the pelvis and upper body is rigid, while the connection between the upper body and head is implemented via a spring that can be stretched and compressed.

[0057] As an example, the occupant model 214 is described below in simplified form as a two-dimensional model that is solved numerically step by step.

[0058] The positive x-axis points in the direction of travel, while the positive z-axis points upward. Lateral movements within the vehicle are not considered.

[0059] For the simulation, a common coordinate system is used in which the basin is located p is initially located at the origin. Furthermore, the pelvis can only move in the x-direction; movement in the z-direction is not possible. The position on the x-axis is x p . For the upper body mt, due to the constraint of the rigid connection with the pelvis, only the angle φ t If absolute coordinates are required, these can be xt=xp+lt⋅sinφt and zt=lt⋅cosφt The head is defined by the free coordinates x h and z h described, whereby the connection to the upper body is maintained by the spring element.

[0060] In a crash, the vehicle's acceleration acts on all occupant components. Restraint systems ensure that the occupant does not leave the vehicle. Particular attention should be paid to the seat, seat belt, and airbag.

[0061] The pelvis is firmly connected to the seat and is also held in position by the belt. The acceleration acting on the pelvis is therefore ap(k)=aFz(k)+Fp,g(k−1)+Fp,s(k−1)mp and can be converted into pelvic velocity and pelvic position by summing twice, ie vp(k)=vp(k−1)+ap(k)⋅dt(k) and xp(k)=sp(k−1)+vp(k)⋅dt(k)

[0062] For the upper body, mass mt and lever arm I t the moment of inertia Jt=mt⋅lt2 This means that the angular acceleration that occurs is at(k)=aFz(k)⋅cosφt(k−1)lt+Mt,g(k−1)+Mt,b(k−1)+Mt,n(k−1)Jt with the applied torques M t,g through the belt, M t,b by the airbag and M t,n through the neck, if the angle enclosed between the neck and the upper body does not vanish. This gives the angular velocity by summing twice as ωt(k)=ωt(k−1)+αt(k)⋅dt(k) and the angle to φt(k)=φt(k−1)+ωt(k)⋅dt(k).

[0063] For the head, all position calculations should be performed in two dimensions. The airbag force F acts on the head. h,b and the neck force F h,n , each with a different angle of attack. The neck force requires the position of the neck in space. It is calculated as φn,g=arctan(xh−xt,zh−zt) with the inverse tangent function over four quadrants arctan. From the neck length ln=(xh−xt)2+(zh−zt)2 The spring force of the neck is |F→n(k)|=[ln(k)−ln(0)]⋅kf,n with the spring constant k f,n . This is decomposed into x- and z-components. Fn→=|Fn→|⋅(xh−xtlnzh−ztln).

[0064] The neck force can also be used to determine the torque exerted on the upper body. Mt,n=|Fn→|⋅ls⋅sinφh, because the effective lever arm depends on the angle between the upper body and the neck.

[0065] As an alternative to describing the neck as a torsion spring, which allows rotation along a circular path as well as changing the radius of this circular path, it is also possible to describe it as a bending beam. This changes the trajectory, in which only a moment and no axial force is transmitted, from a circular path to a modified path.

[0066] The head is also held back by the airbag, so that the total acceleration of the head in vectorial representation is ah→(k)=aFz(k)⋅ex→+Fn→(k−1)Fh,b→(k−1)mh with the unit vector ex→ in the x-direction. By summation, the head speed is vh→(k)=vh→(k−1)+ah→(k)⋅dt(k) and by re-summing the head position xh→(k)=xh→(k−1)+vh→(k)⋅dt(k), also in vectorial representation. This provides the equations of motion for the occupant in the vehicle without any restraint systems.

[0067] In its simplest form, the belt is described as an elastic band whose spring constant depends on its effective length. Friction is initially neglected, so the belt force of the lap and shoulder belts is initially assumed to be equal. In this case, however, only the tension of the belt is equal. The effective restraint force, however, is not necessarily identical, as the belt geometry is generally different.

[0068] The initial belt length is determined by the geometry of the belt system. An initial length in the x- and z-direction is provided for both the upper body and pelvic areas, with the belt then stretching in the x-direction during a crash.

[0069] The belt length is always lg=(xt+xt0)2+zt02+(xp+xp0)2+zp02, with the positions x t of the upper body and x p of the pelvis. The stretch of the belt is then ε(k)=lg(k)lg(0) and dimensionless, which is why the belt force is Fg=kf,g⋅ε with the elastic constant k f,g , which has the dimension of a force. The belt force is then converted into the effective restraining forces for the upper body and pelvis, taking into account the geometric relationships. The force on the pelvis is Fp,g=Fg⋅xplg and the force on the upper body Ft,g=Fg⋅xtlg and from this the effective moment Mt,g=Ft,g⋅lt assuming that the belt force acts on the center of mass of the upper body.

[0070] As an extension of the belt, for example, a belt force limiter is modeled that limits the effective belt force to a maximum value. If the force exceeds the maximum specified belt force, the initial length of the belt is increased to reduce the stretch and thus the effective force. The belt force is then equal to the maximum force, and the belt output is lPO=lg(k)Fmaxkf,g+1−lg(0), whereby the belt force is limited to the maximum force, since then with the new stretch ε(k)=lg(k)lg(0)+lPO The belt force limiter can then be designed so that only a certain amount of belt strap is released. This then provides an upper limit for I POIf the stretching is even greater, the belt force can reach values ​​greater than F max increase. In any case, it is important that the belt force limiter releases belt webbing but does not retract it. This ensures effective energy absorption by the belt force limiter. This energy is then transferred away from the occupant.

[0071] The airbag is described as a volume of gas that is compressed by two pistons, as shown in Fig. 4, is partially compressed. The two pistons have cross-sectional areas that correspond to the contact areas of the occupant's head and chest on the airbag. This applies restraint forces to the head and upper body area.

[0072] The gas volume within the airbag is compressed adiabatically, i.e., without heat exchange with the environment, by the restraint and the impact of the occupant. In addition to compression, the airbag also loses gas through an opening, which is modeled as a hole in a flat surface. The gas flow through such an opening is Vout=CdAoutΔpρ with the discharge coefficient C d = 0.61 for flat openings, the opening area A out , the pressure difference Δp and the density ρ of the escaping gas. The density depends particularly on the temperature of the gas. Assuming that the volume remains constant and the pressure inside decreases due to the outflow, the pressure reduction can be calculated according to Pout=Vout⋅PV This assumption applies particularly only to small outflows, for example, when the time steps are chosen sufficiently small.

[0073] In addition to the loss of gas, the conditions inside the airbag change due to compression by the impacting occupant. The volume V(k)=V(1)−Ah⋅(xh−xh,0)−Ah⋅(xt−xt,0) with the contact surfaces A h and A t of the head and upper body. The respective volume-reducing terms are only active when the parentheses are greater than zero, i.e., when contact has been established between the head and the airbag or between the upper body and the airbag.

[0074] In this case, the restraining forces are Fh,b=p⋅Ah and Ft,b=p⋅At and thus the moment Mt,b=Ft,b⋅lt.

[0075] To achieve a more realistic transition from the unrestrained to the restrained state, the contact surface is designed to be variable according to one embodiment to achieve a smooth transition. Considering the force on a ball falling into an air cushion, the relevant cross-sectional area is the area that intersects the ball perpendicular to the direction of the force. The size of this area is given by Av=Amax⋅[1−(1−dr)2] for the sinking depth d in the range 0 ≤ d ≤ r.

[0076] The pressure in the airbag changes due to adiabatic compression after p(k)=p(k−1)⋅[V(k−1)V(k)]K with the adiabatic coefficient κ = 1.4 for air.

[0077] This means that all forces acting on the occupant within the model are known and the simulation can be continued in the next time step.

[0078] A mass flow into the airbag can be modeled by an inflow of gas with the time-dependent gas flow rate: n˙in=n1⋅tτ⋅exp(−tτ)

[0079] This corresponds to a good approximation of the actual gas flow rate of a gas generator as used in airbags.

[0080] Fig. 6 shows a flow chart of calculations within the framework of an occupant model for determining an occupant movement by a control unit according to an embodiment, for example by a previously based on the Fig. Control unit described in 2 to 5. Shown is a block 600 representing the airbag with a block 602 for the pressure and a block 604 for the volume, a block 606 representing the head with a block 608 for a restraining force acting on the head, a block 610 for the speed of the head and a block 612 for the position of the head, a block 614 representing the upper body with a block 616 for a restraining force acting on the upper body, a block 618 for a speed of the upper body and a block 620 for a position of the upper body, a block 622 representing the pelvis with a block 624 for a restraining force acting on the pelvis, a block 626 for a speed of the pelvis and a block 628 for a position of the pelvis and a block 630 representing the belt with a block 632 for an elongation of the belt webbing and a block 634 for the belt output by the belt force limiter.A distance between head and upper body is represented by a block 636.

[0081] Internal connections are marked by arrows with reference numeral 638. Force effects of the occupant on the restraint system, previously also referred to as the occupant protection system, are marked by arrows with reference numeral 640. Force effects of the restraint system on the occupant are marked by arrows with reference numeral 642.

[0082] Fig. 7 shows a schematic representation of a control unit 202 according to an embodiment, such as one previously described with reference to the Fig. 2 to 6. The control unit 202 comprises a read-in unit 710 for reading in a vehicle acceleration value 712 representing the acceleration of the vehicle and at least one model parameter 714 of the occupant model representing the occupant of the vehicle by at least two, in particular three, mass points. A processing unit 720 is designed to use the vehicle acceleration value 712 and the model parameter 714 to determine at least one movement parameter 722 related to the two, in particular three, mass points, such as an acceleration, a speed, or a path of the two, in particular three, mass points. A generation unit 730 is designed to use the movement parameter 722 to generate the control signal 222 for controlling the occupant protection system of the vehicle.

[0083] Fig. 8 shows a flowchart of a method 800 according to an embodiment. The method 800 can, for example, be used in connection with a method previously described with reference to Fig. 7. In a step 810, the vehicle acceleration value and the model parameter are read in. In a step 820, the vehicle acceleration value and the model parameter are processed to determine the motion parameter. Finally, in a step 830, the control signal for controlling the occupant protection system is generated using the motion parameter.

[0084] According to one embodiment, the method 800 for determining an occupant kinematics comprises a step of providing model parameters of the occupant protection system, a step of detecting a deceleration, an environment and an interior of the vehicle, and a step of determining the movement trajectory of the occupant according to a determination rule from the model parameters and the detected parameters.

[0085] According to a further embodiment, method 800 includes a step of sensing an accident by determining an environmental characteristic using environmental sensors of the vehicle. For example, the environmental sensors detect that an accident is imminent and unavoidable, whereupon the control signal is generated in step 830 before the vehicle comes into contact with the respective collision object in order to trigger reversible or irreversible restraint devices of the occupant protection system. Based on the data on the type or severity of the accident determined by the environmental sensors in combination with data from the interior sensors, an optimal triggering strategy can then be determined.

[0086] If an embodiment comprises an “and / or” link between a first feature and a second feature, this is to be read as meaning that the embodiment according to one embodiment has both the first feature and the second feature and according to another embodiment has either only the first feature or only the second feature.

Claims

[1] Method (800) for controlling an occupant protection system (204) of a vehicle (200), the method (800) comprising the following steps: Reading (810) at least one vehicle acceleration value (712) representing an acceleration of the vehicle (200) and at least one model parameter (714) of an occupant model (214) by which an occupant (212) of the vehicle (200) is represented by at least two; Processing (820) the vehicle acceleration value (712) and the model parameter (714) to determine at least one motion parameter (722) related to the two; and Generating (830) a control signal (222) for controlling the occupant protection system (204) using the movement parameter (722). characterized byin that, in the reading step (810), a parameter is read in as the model parameter (714), which is assigned to a head mass point (216) representing a head and / or neck of the occupant (212) and / or to an upper body mass point (218) representing an upper body of the occupant (212) and / or to a lower body mass point (220) representing a lower body of the occupant (212), and in the processing step (820), the vehicle acceleration value (712) and the model parameter (714) are processed to determine a parameter related to the head mass point (216) and / or the upper body mass point (218) and / or the lower body mass point (220) as the movement parameter (722). [2] Method (800) according to one of the preceding claims, comprising a step of determining at least one restraining force acting on the occupant (212) using the vehicle acceleration value (712) and / or the model parameter (714), wherein in the processing step (820) the movement parameter (722) is determined taking into account the restraining force. [3] Method (800) according to claim 2, wherein in the determining step the restraining force is determined with respect to at least one of the two, in particular three mass points (216, 218, 220). [4] Method (800) according to one of the preceding claims, characterized by that in the step of reading (810), processing (820) and / or determining, three mass points (216, 218, 220) are taken into account. [5] Method (800) according to claim 2, 3 or 4, wherein in the step of determining, a force exerted by a belt (209) and / or a seat (228) and / or an airbag (206) of the vehicle (200) on the occupant (212) and / or a neck force of the occupant (212) is determined as the restraining force. [6] Method (800) according to one of claims 2 to 5, comprising a step of comparing the restraining force with a reference force, wherein in the step of generating (830) the control signal (222) is generated as a function of a result of the comparison. [7] Method (800) according to claim 4 and 6, wherein in the generating step (830) the control signal (222) is generated to increase a length of the belt (209) by unrolling the belt (209) if the comparison shows that the restraining force is greater than the reference force. [8] Method (800) according to one of the preceding claims, wherein in the step of reading (810) environmental information (226) representing an environment of the vehicle (200) and / or interior information representing an interior of the vehicle (200) is read in, wherein in the step of processing (820) the movement parameter (722) is determined using the environmental information (226) and / or the interior information. [9] Control device (202) with units (710, 720, 730) which are designed to carry out and / or control the method (800) according to one of the preceding claims. [10] Computer program designed to execute and / or control the method (800) according to one of claims 1 to 8. [11] A machine-readable storage medium on which the computer program according to claim 10 is stored.

Images