Data processing: measuring – calibrating – or testing – Measurement system – Speed
Reexamination Certificate
2001-05-22
2004-03-02
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system
Speed
C702S151000, C701S036000, C701S045000
Reexamination Certificate
active
06701276
ABSTRACT:
BACKGROUND
1. Field of the Invention
The invention concerns a method for generating an activating algorithm processing the sensor signal of an angular rate sensor provided within the safety system of a motor vehicle, by means of which an activation decision for activating at least one safety device of the safety system is taken in relation to the sensor signal, and with the sensor signal representing a measure for the rotational velocity of the rolling motion occurring when a rollover is imminent. Furthermore this invention also concerns a safety system for motor vehicles with at least one safety device, which safety system utilizes this activating algorithm. Here, in connection with rollover events, the safety devices in question are mainly roll bars, seat-belt tensioners, and side airbags.
2. Description of the Related Technology
From EP 0 430 813 B1 a safety system for motor vehicles is known which features an electronic arrangement for controlling at least one safety device in the event of a motor vehicle rolling over. The safety system comprises a gyrometer (angular rate or gyro sensor), which measures the rotational velocity of the rolling motion, and acceleration meters, with the electronic arrangement processing the signals coming from the gyrometer and the acceleration sensors in order to control the activation of the safety device. Here, the sensor signals are evaluated by integration for a specified period of time. In order to avoid an overflow of the integration, the ratio of the transverse acceleration to the vertical acceleration is additionally calculated, and if a specified threshold value is exceeded, integration is released.
The disadvantage of the activating algorithm used in this safety system is above all that, in order to avoid an overflow of the integration, further signals are required in addition to the signals of the angular rate sensor, namely acceleration sensor signals; these only meet the purpose to be able to evaluate the angular rate sensor signals, but entail high manufacturing costs for the total system.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a method for generating an activating algorithm processing the sensor signal of an angular rate sensor provided within the safety system of a motor vehicle, by means of which an activation decision for activating at least one safety device of the safety system is taken in relation to the sensor signal, and with the sensor signal representing a measure for the rotational velocity of the rolling motion occurring when a rollover is imminent, and which does not feature the above-mentioned disadvantages, that is, it does not require signals from further expensive acceleration sensors for evaluating the angular rate sensor signals.
According to the present invention, this object is achieved according to the following steps:
a) generating a theoretical characteristic rollover curve as follows:
&agr;
th
(&ohgr;)=−(&agr;
tip
/&ohgr;
lim
)&ohgr;+&agr;
tip
, &ohgr;≧0 Equation (1)
where &ohgr; corresponds to the initial rotational velocity of a rolling motion of the vehicle, and &agr;
th
(&ohgr;) represents the inclination angle of the vehicle, the constants &agr;
tip
and &ohgr;
lim
are determined in relation to the actual vehicle and state the static tip angle of the vehicle, which —if exceeded—causes the vehicle to tip over, and the rotational velocity range, at which with &ohgr;≧&ohgr;
lim
a rollover of the vehicle will occur, and the range B
th
which with (&ohgr;, &agr;)—combinations with |&agr;|≧&agr;
th
(|&ohgr;|) wherein &agr; and &ohgr; are real values, represents the associated rollover risk range where a positive activation decision is expected, and
b) generating an activation algorithm by approximating the characteristic rollover curve of Equation (1) in the first quadrant of a coordinate system with at least two low pass filter functions (Y
1,n
, n=1,2, . . . ; Y
2,n
, n=1,2, . . . ) each having at least one activation threshold (S
1
, S
2
), by the limit frequencies f
g1
, f
g2
) of the two low pass filter functions (Y
1,n
, n=1,2, . . . ; Y
2,n
, n=1,2, . . . ) and determining said activation thresholds (S
1
, S
2
) such that for the range B
F2
of the (|&ohgr;|, Y
l,n
, (&ohgr;)) value pairs and the range B
F2
of the (|&ohgr;|, Y
2,n
, (&ohgr;)) value pairs with
|Y
l,n
(&ohgr;)|>S
1
, and |Y
2,n
(&ohgr;)|>S
2
Equation (2)
and wherein Y
1,n
(&ohgr;) and Y
2,n
(&ohgr;) are real values, and B
F1
⊂B
th
and B
F2
⊂B
th
are satisfied.
Due to the fact that with the method according to the invention an activating algorithm is generated, which evaluates with low pass filter functions the sensor signals generated by the angular rate sensor, the disadvantages occurring when integrators are used have been avoided in a surprisingly simple fashion as the measures required to avoid an overflow—in particular, the additional sensors specified in the state of the art—are now no longer required.
The method according to the invention uses a theoretical characteristic rollover curve as a characteristic curve model for generating the activating algorithm in accordance with the invention. The activation algorithm satisfies equation (1) set forth above. The &ohgr;-&agr;-graph 1 of the equation (1) is shown in
FIG. 1
, wherein |&ohgr;| represents the rotational velocity value of the rolling motion occurring in the x direction or longitudinal axis of the vehicle if a vehicle rollover is imminent and wherein |&agr;| represents the inclination angle value in the y direction or cross-axis of the vehicle. The &ohgr;-&agr; graph subdivides the first quadrant of a coordinate system into two areas which on the one hand concern vehicle conditions with &ohgr;-&agr;-combinations that are to lead to the activation of a safety device, i.e. “fire” scenarios, and, on the other hand, “no-fire” scenarios whose &ohgr;-&agr;-combinations are not to lead to the activation of the safety device. The &ohgr;
lim
, 0-combination or 0-&agr;
tip
—combination represents a limit condition of a vehicle with a rotational velocity &ohgr;
lim
in the x direction and an inclination angle of 0° or with a rotational velocity 0 and an inclination angle (static tip angle) &agr;
tip
that leads to a rollover. These parameters are vehicle specific and, therefore, need to be determined for each vehicle type.
In addition to the theoretical characteristic curve
1
,
FIG. 1
shows three rollover scenarios with the curves
2
,
3
, and
4
. Curve
2
shows the course of a rollover starting with a high initial velocity. Curve
3
shows a situation where the vehicle is driven onto a screwramp with a following rollover. Curve
4
shows a quasi-static rollover where the vehicle reaches the static tip angle with an angular velocity of almost zero and then rolls over.
The low pass filter functions can be generated as digital filters of the 1st magnitude by means of a computer where the filter algorithm consists of linear difference equations with constant coefficients, and where recursive as well as non-recursive difference equations can be used.
A filter algorithm for the first and second low pass filter function Y
1,n
, n=1,2, . . . and Y
2,n
, n=1,2, . . . of a recursive filter of the first magnitude here takes on the following form:
Y
1,n
=d
1
Y
1,n−1
+c
1
X
n−1
, n=
1,2 . . . or
Y
2,n
=d
2
Y
2,n−1
+c
2
X
n−1
, n=
1,2 . . .
with X
n
representing the digitized input sequence of the rotational velocity &ohgr;, and Y
1,n
or Y
2,n
representing the corresponding output sequence, that is the inclination angle &agr; in binary representation. The coefficients of the filter algorithm are determined in accordance with method step (b) by approximation and defining the limit frequencies and the trigger thresholds such that condition (2) is met.
The cutoff fre
Kueblbeck Hermann
Rottenkolber Ernst
Steiner Peter
Steurer Helmut
Weidel Peter
Conti Temic microelectronic GmbH
Fasse W. F.
Fasse W. G.
Hoff Marc S.
West Jeffrey R.
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