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

Abstract

A method for controlling an occupant protection system of a vehicle includes 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 a vehicle occupant is represented by at least two, in particular three, mass points. The vehicle acceleration value and the model parameter are processed in order to determine at least one motion parameter relating to the two, in particular three, mass points. Using the motion parameter, a control signal for controlling the occupant protection system is produced.

Claims

1. A method for controlling an occupant protection system of a vehicle, the method comprising: reading in, by a processing unit, (a) a vehicle acceleration value representing an acceleration of the vehicle and (b) a model parameter of an occupant model, the occupant model representing an occupant of the vehicle by at least two mass points, wherein the occupant model is a spring-mass-damper model representing motion of the occupant in a crash of the vehicle, and wherein the at least two mass points include a head mass point representing a head and/or a neck of the occupant and an upper body mass point representing an upper body of the occupant, the occupant model connecting the head mass point to the upper body mass point by a spring element; determining, by the processing unit, at least one motion parameter relating to the mass points using the occupant model, the vehicle acceleration value, and the model parameter; and producing, by the processing unit, a control signal for controlling the occupant protection system using the motion parameter.

2. The method of claim 1, further comprising determining, based on at least one of the vehicle acceleration value and the model parameter, at least one restraining force acting on the occupant, wherein the determination of the motion parameter is based on the determined restraining force.

3. The method of claim 2, wherein the at least one restraining force relates to at least one of the mass points.

4. The method of claim 2, wherein the at least one restraining force includes at least one of (a) a force exerted by at least one of a belt of the vehicle, a seat of the vehicle, and an airbag of the vehicle, and (b) a neck force of the occupant.

5. The method of claim 2, further comprising comparing the restraining force to a reference force, wherein the production of the control signal is as a function of a result of the comparison.

6. The method of claim 5, wherein the production of the control signal is in response to the result of the comparison being that the restraining force is greater than the reference force, and the production of the control signal causes a length of the belt to be increased by unrolling the belt.

7. The method of claim 1, further comprising reading in at least one of an item of environmental information representing a surrounding environment of the vehicle and an item of interior compartment information representing an interior compartment of the vehicle, the determination of the motion parameter is further based on the at least one of the item of environmental information and the item of interior compartment information.

8. The method of claim 1, wherein the at least two mass points includes three mass points.

9. The method of claim 1, wherein the spring element connecting the head mass point to the upper body mass point is a rotational spring.

10. The method of claim 1, wherein the occupant model further includes a lower body mass point representing a lower body of the occupant, and wherein in the occupant model, a connection between the lower body mass point the upper body being fixed in length by capable of rotation.

11. A system comprising: an input; and processing circuitry interfacing with a vehicle occupant protection system, wherein the processing circuitry is configured to: read in, via the input, (a) a vehicle acceleration value representing an acceleration of the vehicle and (b) a model parameter of an occupant model, the occupant model representing an occupant of the vehicle by at least two mass points, wherein the occupant model is a spring-mass-damper model representing motion of the occupant in a crash of the vehicle, and wherein the at least two mass points include a head mass point representing a head and/or a neck of the occupant and an upper body mass point representing an upper body of the occupant, the occupant model connecting the head mass point to the upper body mass point by a spring element; determine at least one motion parameter relating to the mass points using the occupant mode, the vehicle acceleration value, and the model parameter; and provide to the vehicle occupant protection system a control signal for controlling, the occupant protection system using the motion parameter.

12. A non-transitory computer-readable medium on which are stored instructions that are executable by a processor and that, when executed by the processor, cause the processor to perform a method for controlling an occupant protection system of a vehicle, the method comprising: reading in (a) a vehicle acceleration value representing an acceleration of the vehicle and (b) a model parameter of an occupant model, the occupant model re resenting an occupant of the vehicle by at least two mass points, wherein the occupant model is a spring-mass-damper model representing motion of the occupant in a crash of the vehicle, and wherein the at least two mass points include a head mass point representing a head and/or a neck of the occupant and an upper body mass point representing an upper body of the occupant, the occupant model connecting the head mass point to the upper body mass point by a spring element; determining at least one motion parameter relating to the mass points using the occupant model, the vehicle acceleration value and the model parameter; and producing a control signal for controlling the occupant protection system using the motion parameter.

13. The system of claim 11, wherein the spring element connecting the head mass point to the upper body mass point is a rotational spring.

14. The system of claim 11, wherein the occupant model further includes a lower body mass point representing a lower body of the occupant, and wherein in the occupant model, a connection between the lower body mass point the upper body being fixed in length by capable of rotation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a diagram schematically representing a real accident event as a function of a mass and a change of speed of a vehicle.

(2) FIG. 2 shows a schematic representation of a vehicle having a control device according to an example embodiment of the present invention.

(3) FIG. 3 shows a representation of an overall schema of an occupant protection system for controlling by a control device according to an example embodiment of the present invention.

(4) FIG. 4 shows a schematic representation of an occupant model for ascertaining of an occupant motion by a control device according to an example embodiment of the present invention.

(5) FIG. 5 shows a schematic representation of occupant elements of an occupant model for ascertaining of an occupant motion by a control device according to an example embodiment of the present invention.

(6) FIG. 6 is a flowchart of calculations in the context of an occupant model for the ascertaining of an occupant motion by a control device according to an example embodiment of the present invention.

(7) FIG. 7 shows a schematic representation of a control device according to an example embodiment of the present invention.

(8) FIG. 8 is a flowchart that illustrates a method according to an example embodiment of the present invention.

DETAILED DESCRIPTION

(9) FIG. 1 shows a diagram for the schematic representation of a real accident event as a function of a mass m and a change in speed v of a vehicle. Shown is an accident event of a real, complex world 100, modeled through queried crash tests 102, such as NCAP tests, with associated interpolation curves 104 that are used to describe scenarios through a corresponding model.

(10) FIG. 2 shows a schematic representation of a vehicle 200 having a control device 202 according to an exemplary embodiment. Control device 202 is fashioned to control an occupant protection system 204 of vehicle 200.

(11) As an example, occupant protection system 204 includes an airbag 206 and a belt force limiter 208 for limiting a belt force acting on a belt 209. Vehicle 200 is about to collide with an object 210, here a tree. In order to control occupant protection system 204, control device 202 ascertains a motion of an occupant 212 of vehicle 200, caused by the collision of vehicle 200, using an occupant model 214 and a current acceleration of the vehicle 200, which in the scenario shown in FIG. 2 is a deceleration of vehicle 200. For example, occupant 212 is represented in occupant model 214 by at least two, here in particular three, mass points linked to one another, here by a head mass point 216 assigned to a head region of occupant 212, an upper body mass point 218 assigned to an upper body of occupant 212, and a lower body mass point 220 assigned to a lower body of occupant 212. Control device 202 uses the current acceleration of vehicle 200 and suitable parameters of occupant model 214, also called model parameters hereinafter, to model the motion of occupant 212 on the basis of a motion of the two, in particular three, mass points 216, 218, 220. Examples of directions of motion of the two, in particular three, mass points 216, 218, 220 are schematically illustrated by four arrows. The model parameters are for example ascertained through crash trials and are stored in control device 202. In addition, the model parameters can be adapted to an actual course of an accident via measurements by sensors of vehicle 200. As a function of the motion of occupant 212 ascertained on the basis of occupant model 214, control device 202 produces control signals 222 for controlling the components of occupant protection system 204, here airbag 206 and belt force limiter 208. In this way, occupant protection system 204 can be controlled with a low computing outlay, and thus particularly quickly.

(12) Optionally, control device 202 is connected to an environmental sensor 224 for acquiring a surrounding environment of vehicle 200, in order to read in an item of environmental information 226 that is provided by environmental sensor 224 and that represents object 210. According to this exemplary embodiment, control device 202 is fashioned to ascertain the motion of the two, in particular three, mass points 216, 218, 220, additionally using item of environmental information 226.

(13) According to an exemplary embodiment, control device 202 ascertains the respective motions of the two, in particular three, mass points 216, 218, 220, taking into account at least one restraining force exerted on occupant 212 by occupant protection system 204. The restraining force is exerted for example by airbag 206, belt 209, or a seat 228 occupied by occupant 212. Control device 202 ascertains the restraining force in particular using the model parameter. For example, control device 202 is fashioned to activate belt force limiter 208 when the restraining force exceeds a specified reference force.

(14) FIG. 3 shows a representation of an overall schema of an occupant protection system 204 for controlling by a control device 202 according to an exemplary embodiment, such as a control device, as described above on the basis of FIG. 2. Shown are a block 300, representing an item of occupant information, a block 302 that represents the occupant model, a block 304 that represents an actuator controlling, a block 306 that represents a restraint controlling strategy, and a block 308 that represents an energy management. The directions of a signal flow between the individual blocks are marked with arrows.

(15) The occupant protection function is represented by an overall system made up of a higher-level controlling instance that enables the use of particular restraint components, for example in groups, on the basis of external conditions, and the combination of the occupant model and actuator controlling, which determine an optimal triggering strategy in a process that is in particular iterative, and including occupant parameters that are present.

(16) The occupant model is designed for example as a differential equation model that, depending on the exemplary embodiment, is solved analytically or as a numerically calculated occupant simulation. The occupant model represents a three-dimensional model that describes the complete motion of the occupant in space.

(17) FIG. 4 shows a schematic representation of an occupant model 214 for the ascertaining of an occupant motion by a control device according to an exemplary embodiment, for example a control device described above on the basis of FIGS. 2 and 3.

(18) According to this exemplary embodiment, occupant model 214 is fashioned as a spring-mass-damper model for representing the motion of the occupant in the case of an accident. Here, for example the focus is on a frontal accident. Occupant model 214 includes the two, in particular three, mass points 216, 218, 220, having masses m.sub.h, m.sub.t, and m.sub.l. Here, lower body mass point 220 represents the lower body up to the pelvis, upper body mass point 218 represents the upper body including the arms, and head mass point 216 represents the head of the occupant. These are point masses that are connected to one another via spring-damper elements. The connection between the pelvis and the upper body (thorax) is here realized so as to be fixed in length but capable of rotation. In the model, the pelvis moves only one-dimensionally in the x direction, here corresponding to a direction of travel of the vehicle. Motions in the z direction (vertical axis) and y direction (transverse direction) are not possible. The upper body is connected to the pelvis and is realized as a standing pendulum; that is, the connection is rigid but capable of rotation. The length of this connection corresponds for example to the distance of the upper body center of gravity from the pelvis in a human being, as is known from the literature.

(19) The two mass points 218, 220 are in addition coupled to the elastic belt 209. Also shown is airbag 206 having a gas volume V and a gas pressure p. The two quantities V, p are influenced by two plungers 400, 402 that act on airbag 206, a first plunger 400 representing a contact surface of the head with airbag 206 and a second plunger 402 representing a contact surface of the upper body with airbag 206. A direction of release of airbag 206 is identified by an arrow.

(20) The shoulder point is also situated on the axis from the pelvis to the upper body center of gravity, but at a greater distance from the pelvis. This distance is also known from the literature.

(21) At the shoulder point, the upper body is connected to the head. The connecting element of the shoulder point to the mass center of gravity of the head is realized as a combined spring-damper element and as a torsion spring; that is, a change in length and a change of angle are possible, but are reset by internal forces. To ascertain the values of the neck rigidity, for example the spring constants of a Hybrid III dummy are used, as is used in crash tests for modeling human beings.

(22) FIG. 5 shows a schematic representation of occupant elements of an occupant model 214 for the ascertaining of a motion of an occupant by a control device according to an exemplary embodiment. Occupant model 214 essentially corresponds to an occupant model as shown in FIG. 4. In FIG. 5, in addition various model parameters of occupant model 214 are depicted, as are used in the motion equations described below in order to ascertain the occupant motion.

(23) The input quantity for the calculation using occupant model 214 is for example a crash impulse, indicated in sampled form. The crash impulse is for example handed over in one piece so that the simulation is calculated completely and immediately. Alternatively, the data points are each handed over to occupant model 214 directly after a measurement in the vehicle, and the corresponding current occupant motion is calculated therefrom. In each case, the time points t.sub.k are known, as are the vehicle acceleration values a.sub.Fz(k) with the associated time values t(k), which increase strictly monotonically with k. Thus, the smallest time step that can be represented is dt(k)=t(k)t(k1). In addition, 1kK, where k, KN.

(24) Starting with the vehicle acceleration values, first the vehicle motion is calculated. For this purpose, the vehicle acceleration values are summed and an integration constant is selected such that the final speed goes to zero, thus:

(25) $v_{\mathrm{Fz}}\left(k\right)=\underset{i=1}{\overset{k}{.Math.}}{a}_{\mathrm{Fz}}\left(l\right)-v_{\mathrm{Fz}}\left(K\right).$

(26) Through further summation, the vehicle position is determined therefrom:

(27) $s_{\mathrm{Fz}}\left(k\right)=\underset{i=1}{\overset{k}{.Math.}}{v}_{\mathrm{Fz}}\left(l\right)-s_{\mathrm{Fz}}\left(K\right).$

(28) Here as well, the integration constant is selected such that the final position is
s.sub.Fz(K)=0.

(29) Depending on the exemplary embodiment, the crash impulse is indicated explicitly or is determined generically. Here, an initial speed is dismantled via a sinusoidal deceleration impulse. The deceleration is

(30) $a_{\mathrm{Fz}}\left(k\right)=\{\begin{array}{c}{a}_{\mathrm{ma}x}.Math.\frac{1}{2}\left(1-\cos 2\frac{t}{}\right)\\ 0\end{array}$
with the maximum deceleration being

(31) $a_{\mathrm{ma}x}=2\frac{v_0}{}$
and the pulse duration . For typical cases of load, i.e., initial speeds in the range of around 50 km/h, the pulse duration is for example in the range of approximately 120 ms.

(32) For description, the occupant is analyzed into two, in particular three, elements. The two, in particular three, elements are the pelvis and legs, the upper body including the arms, and the head. These elements are modeled by the point masses m.sub.p for the legs, m.sub.t for the upper body, and m.sub.h for the head, these being connected to one another. Here, the connection between the pelvis and the upper body is rigid, while the connection between the upper body and the head is realized via a spring that can be expanded and compressed.

(33) As an example, in the following the occupant model 214 is described in simplified fashion as a two-dimensional model that is resolved numerically step-by-step.

(34) The positive x axis points in the direction of travel, while the positive z axis points upward. Lateral movements inside the vehicle are not taken into account.

(35) For the simulation, a common coordinate system is used in which at the beginning the pelvis m.sub.p is situated at the origin. In addition, the pelvis can move only in the x direction; movement in the z direction is not possible. The position on the x axis is x.sub.p. For the upper body m.sub.t, only the angle .sub.t is used for the description, due to the necessary condition resulting from the rigid connection with the pelvis. If absolute coordinates are required, these can be determined as
x.sub.t=x.sub.p+l.sub.t.Math.sin .sub.t
and
z.sub.t=l.sub.t.Math.cos .sub.t.

(36) The head is described by the free coordinates x.sub.h and z.sub.h, the connection to the upper body being held by the spring element.

(37) During a crash, the vehicle acceleration acts on all occupant elements. The restraint systems here ensure that the occupant does not leave the vehicle. In particular, here the seat, the safety belt, and the airbag are to be taken into consideration.

(38) The pelvis is connected to the seat with a non-positive connection, and in addition is held in position by the belt. The acceleration acting on the pelvis is therefore

(39) $a_p\left(k\right)=a_{\mathrm{Fz}}\left(k\right)+\frac{F_{p,g}\left(k-1\right)+F_{p,s}\left(k-1\right)}{m_p}$
and can be converted into pelvis speed and pelvis position by summation two times, i.e.
v.sub.p(k)=v.sub.p(k1)+a.sub.p(k).Math.dt(k)
and
x.sub.p(k)=s.sub.p(k1)+v.sub.p(k).Math.dt(k)

(40) For the upper body, first the moment of inertia J.sub.t=m.sub.t.Math.l.sub.t.sup.2.

(41) is to be calculated from the mass m.sub.t and the lever arm l.sub.t. The following then holds for the occurrent angular acceleration:

(42) ${}_t\left(k\right)=\frac{a_{\mathrm{Fz}}\left(k\right).Math.\cos {}_t\left(k-1\right)}{l_t}+\frac{M_{t,g}\left(k-1\right)+M_{t.b}\left(k-1\right)+M_{t,n}\left(k-1\right)}{J_t}$
with the applied torques M.sub.t,g by the belt, M.sub.t,b by the airbag, and M.sub.t,n by the neck, if the angle enclosed between the neck and the upper body does not disappear. From this, through summation two times the angular speed results as
.sub.t(k)=.sub.t(k1)+.sub.t(k).Math.dt(k)
and the angle results as
.sub.t(k)=.sub.t(k1)+.sub.t(k).Math.dt(k)

(43) For the head, all position calculations are to be carried out in two dimensions. Here, the airbag force F.sub.h,b and the neck force F.sub.h,n, each having different angles of attack, act on the head. For the neck force, the position of the neck in space is required. It is calculated as
.sub.n,g=arctan(x.sub.hx.sub.t,z.sub.kz.sub.t)
with the inverse tangent function over four quadrants of arctan. From the neck length
l.sub.n={square root over ((x.sub.hx.sub.t).sup.2+(z.sub.hz.sub.t).sup.2)}
the spring force of the neck results as
|{right arrow over (F.sub.n)}(k)|=[l.sub.n(k)l.sub.n(0)].Math.k.sub.f,n
with the spring constant k.sub.f,n. This is decomposed into x and z components. The following holds:

(44) ${\stackrel{->}{F}}_n=.Math.{\stackrel{->}{F}}_n.Math..Math.\left(\begin{array}{c}\frac{x_h-x_t}{l_n}\\ \frac{z_h-z_t}{l_n}\end{array}\right).$

(45) With the neck force, the torque exerted on the upper body can also be determined. Here the following holds:
M.sub.t,n=|{right arrow over (F.sub.n)}|.Math.l.sub.n.Math.sin .sub.k,
because the effective lever arm is a function of the angle between the upper body and the neck.

(46) As an alternative to this description of the neck as a rotational spring that permits rotation on a circular path as well as change of the radius of the circular path, a description as a flexible beam is also possible. In this way, the trajectory in which only a torque and no axial force is transmitted is changed from a circular path to a modified path.

(47) In addition, the head is restrained by the airbag, so that the overall acceleration of the head, in a vectorial representation, results as

(48) $\stackrel{.fwdarw.}{a_k}\left(k\right)=a_{\mathrm{Fz}}\left(k\right).Math.\stackrel{.Math.}{e_x}+\frac{\stackrel{.fwdarw.}{F_n}\left(k-1\right)+\stackrel{.Math.}{F_{h,b}}\left(k-1\right)}{m_h}$
with unit vector {right arrow over (e.sub.x )} in the x direction. Through summation, the head speed results as
{right arrow over (v.sub.h)}(k)={right arrow over (v.sub.k)}(k1)+{right arrow over (a.sub.h)}(k).Math.dt(k)
and, through repeated summation, there results the head position
{right arrow over (x.sub.h)}(k)={right arrow over (x.sub.h)}(k1)+{right arrow over (v.sub.h)}(k).Math.dt(k)
also in a vectorial representation. These give the equations of motion for the occupants in the vehicle without any restraint systems.

(49) In the simplest case, the safety belt is described as an extensible band whose spring constant is a function of the effective length. At first, friction is neglected, so that the belt force of the lap belt and shoulder belt are first assumed to be equal. However, in this case only the tension force of the belt is equal. The effective restraining force is however not necessarily identical, because in general the belt geometry is different.

(50) The initial belt length is determined from the geometry of the belt system. Here, both in the upper body region and in the pelvic region an initial length is provided in the x and z directions, and during a crash the belt is then extended in the x direction.

(51) Here, at each time the belt length is
l.sub.g={square root over ((x.sub.t+x.sub.t0).sup.2+z.sub.t0.sup.2)}+{square root over ((x.sub.p+x.sub.p0).sup.2+z.sub.p0.sup.2)},
with positions x.sub.t of the upper body and x.sub.p of the pelvis. The extension of the belt is then

(52) $\mathrm{.Math.}\left(k\right)=\frac{l_g\left(k\right)}{l_g\left(0\right)}$
and is dimensionless, for which reason the following then holds for the belt force:
F.sub.g=k.sub.f,g.Math.
with constant of elasticity k.sub.f,g, having the dimension of a force. The belt force is then converted into the effectively acting restraining forces for the upper body and the pelvis, taking into account the geometric relations. Here the force on the pelvis is

(53) 0$F_{p,g}=F_g.Math.\frac{x_p}{l_g}$
and the force on the upper body is

(54) $F_{t,g}=F_g.Math.\frac{x_t}{l_g}$
and from these there results the acting torque
M.sub.t,g=F.sub.t,g.Math.l.sub.t
under the assumption that the belt force is applied at the mass center of gravity of the upper body.

(55) As an expansion of the belt, for example a belt force limiter is modeled that limits the effective belt force to a maximum value. For this purpose, if the force becomes greater than the maximum provided belt force, the initial length of the belt is increased in order to reduce the extension and thus the effective force. The belt force is then equal to the maximum force and the amount of belt paid out is

(56) $l_{\mathrm{PO}}=\frac{l_g\left(k\right)}{F_{\mathrm{ma}x}/k_{f,g}+1}-l_g\left(0\right)$
whereby the belt force is limited to the maximum force, because the belt force is then determined with the new extension

(57) $\mathrm{.Math.}\left(k\right)=\frac{l_g\left(k\right)}{l_g\left(0\right)+l_{\mathrm{PO}}}.$

(58) The belt force limiter can now in turn be designed such that only a specified amount of safety belt is paid out. In this way, an upper limit for l.sub.PO is then defined. As the expansion becomes greater, the belt force can increase to values greater than F.sub.max. In each case, it is important that an amount of safety belt is paid out by the belt force limiter but is not drawn in again. In this way, there results an effective energy consumption of the belt force limiter. This energy is taken from the occupant.

(59) The airbag is described as a gas volume that is partially compressed by two plungers, shown as examples in FIG. 4. The two plungers have cross-sectional surfaces that correspond to the contact surfaces of the head and chest of the occupant on the airbag. In this way, restraining forces are introduced at the head and in the upper body region.

(60) The gas volume inside the airbag is compressed adiabatically, i.e., without an exchange of heat with the surrounding environment, by the restraint and by the occupants impacting it. Besides the compression, the airbag also loses gas through an opening that is modeled as a hole in a flat surface. The flow of gas through such an opening is

(61) $V_{\mathrm{out}}=C_d{A}_{\mathrm{out}}\sqrt{\frac{p}{}}$
with coefficient of discharge C.sub.d=0.61 for flat openings, opening surface A.sub.out, pressure difference p and density p of the gas flowing out. The density is in particular a function of the temperature of the gas. Under the assumption that the volume remains constant and that the pressure in the interior decreases due to the outflow, the reduction in pressure can be calculated according to

(62) $p_{\mathrm{out}}=V_{\mathrm{out}}.Math.\frac{p}{V}.$

(63) This assumption holds in particular only for small outflow volumes, for example given time steps selected to be adequately small.

(64) Besides the gas loss, the conditions in the interior of the airbag change due to the compression exerted by the impacting occupants. Here, the volume is
V(k)=V(l)A.sub.k.Math.(x.sub.hx.sub.h,0)A.sub.k.Math.(x.sub.tx.sub.t,0)
with contact surfaces A.sub.h and A.sub.k of the head and upper body. The respective terms that reduce the volume are active only when the expressions in parentheses are greater than zero; that is, when the contact between the head and the airbag or between the upper body and the airbag has been produced.

(65) In this case, the restraining forces result as
F.sub.k,h=p.Math.A.sub.k
and
F.sub.t,b=p.Math.A.sub.t,
and the torque thus results as
M.sub.t,b=F.sub.t,b.Math.l.sub.t.

(66) In order to obtain a more realistic transition from the non-restrained to the restrained state, according to an exemplary embodiment the contact surface is made variable in order to achieve a smooth transition. If the force on a sphere that falls into an air cushion is considered, then the relevant cross-sectional surface is that surface that intersects the sphere with an orientation normal to the direction of force. The size of this surface results as

(67) $A_v=A_{\mathrm{ma}x}.Math.\left[1-{\left(1-\frac{d}{r}\right)}^2\right]$
for sink-in depth d in the range 0dr.

(68) Due to the adiabatic compression, the pressure in the airbag varies according to

(69) $p\left(k\right)=p\left(k-1\right).Math.{\left[\frac{V\left(k-1\right)}{V\left(k\right)}\right]}^{}$
with the adiabatic coefficient =1.4 for air.

(70) In this way, all forces acting on the occupant within the model are known, and the simulation can be continued in the next time step.

(71) A mass flow into the airbag can be modeled by an inflow of gas with the time-dependent gas flow rate:

(72) ${\stackrel{.}{n}}_{in}=n_1.Math.\frac{t}{}.Math.\exp \left(-t/\right).$

(73) To a good approximation, this corresponds to the actual gas flow rate of a gas generator as is used in airbags.

(74) FIG. 6 shows a flow diagram of calculations in the context of an occupant model for an ascertaining of an occupant movement by a control device according to an exemplary embodiment, for example a control device described above on the basis of FIGS. 2 through 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, as well as a block 630 representing the belt, with a block 632 for an extension of the belt and a block 634 for the paying out of the belt by the belt force limiter. The distance between the head and the upper body is represented by a block 636.

(75) Internal relationships are marked by arrows having reference characters 638. Actions of force of the occupant on the restraint system, also referred to above as the occupant protection system, are marked with arrows having reference characters 640. Effects of force of the restraint system on the occupants are marked with arrows having reference characters 642.

(76) FIG. 7 shows a schematic representation of a control device 202 according to an exemplary embodiment, for example a control device described above on the basis of FIGS. 2 through 6. Control device 202 includes 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 through at least two, in particular three, mass points. A processing unit 720 is fashioned to determine at least one motion parameter 722 relating to the two, in particular three, mass points, using vehicle acceleration value 712 and model parameter 714, the motion parameter being for example an acceleration, a speed, or a path of the two, in particular three, mass points. A producing unit 730 is fashioned to produce control signal 222 for controlling the occupant protection system of the vehicle, using the motion parameter 722.

(77) FIG. 8 shows a flow diagram of a method 800 according to an exemplary embodiment. Method 800 can for example be carried out in connection with a control device described above on the basis of FIG. 7. Here, 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 in order to determine the motion parameter. Finally, in a step 830, using the motion parameter the control signal for controlling the occupant protection system is produced.

(78) According to an exemplary embodiment, method 800 for determining an occupant kinematics includes a step of providing model parameters of the occupant protection system, a step of acquiring a deceleration, a surrounding environment, and an interior space of the vehicle, and a step of determining the movement trajectory of the occupant, according to a determination rule, from the model parameters and from the acquired parameters.

(79) According to a further exemplary embodiment, method 800 includes a step of sensing an accident by ascertaining an environmental characteristic using an environmental sensor system of the vehicle. Here, for example the environmental sensor system recognizes that an accident is immediately impending and is unavoidable, whereupon, already before the contact of the vehicle with the respective collision object, in step 830 the control signal is produced in order to trigger reversible or irreversible restraint component of the occupant protection system. On the basis of the data ascertained by the environmental sensor system concerning the type of accident or severity of the accident, in combination with data from the interior compartment sensor system, an optimal triggering strategy can then be determined.

(80) If an exemplary embodiment includes an and/or linkage between a first feature and a second feature, this is to be read as meaning that according to a specific embodiment the exemplary embodiment has both the first feature and the second feature, and according to another specific embodiment the exemplary embodiment has either only the first feature or only the second feature.