Data processing: measuring – calibrating – or testing – Measurement system – Speed
Reexamination Certificate
1998-11-27
2001-05-22
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system
Speed
C073S001370, C073S488000
Reexamination Certificate
active
06236954
ABSTRACT:
The present invention relates to a process intended for estimating the speed of a single vehicle or one which is connected to other vehicles, fitted with wheels which can slip with respect to their rolling surface, when they transmit a load intended for accelerating or decelerating the said vehicle. Application in particular to railway vehicles.
A first type of prior art documents relates to control processes for improving the adhesion of a wheel with respect to the rolling surface.
A second type of prior art documents relates to processes for estimating the speed of a vehicle in particular while all its wheels are slipping with respect to the rolling surface.
Only the second type of prior art documents constitutes the state of the art of the invention, since the present invention pertains to an estimator of vehicle speed when all the wheels can slip simultaneously with respect to the rolling surface.
Nevertheless, it seems of interest to analyse both prior art document types so that the characteristics of the invention may be better placed.
1—Patents Pertaining to the Improvement of Adhesion
1.1—U.S. Pat. No. 5,471,387A—Apr. 18, 1994—Westinghouse Air Brake Company
This is a process intended for reducing the braking load in a manner which is dependent on the deceleration of the axle, when jamming is detected during braking by comparing:
a threshold which depends on the absolute speed of the axle,
with the speed discrepancy resulting from the integration over time of the axle acceleration, when the latter exceeds another pre-set threshold.
The speed discrepancy acting at the same time as the deceleration of the axle for reduction of the braking load.
The inputs of this command are the acceleration of the axle (
12
) and the speed of the axle (
10
). No mention is made of the use of a vehicle speed.
1.2—U.S. Pat. No. 5,390,990A—Nov. 24, 1993—Hydro-Aire Division of Crane Company
This document describes a complete system for applying and distributing loads between the various vehicles, coupled in convoy by a link exhibiting non-zero elasticity, so as to limit the coupling reactions during braking.
It therefore involves modulating the load applied to the wheel by way of a braking electric valve, as a function of the discrepancy between the measured speed of the wheel (
20
) and a speed referred to as the reference speed, the latter being generated in a preferential manner on the basis of a deceleration command emanating from a control handle (
2
-
45
).
1.3—U.S. Pat. No. 5,424,948A—Nov. 10, 1993—General Motors Corporation
The process described maximizes the load transmitted by the wheels of a locomotive to the rail through the coefficient of adhesion, via a command applied to the current and field regulator of the electric motor of the locomotive using the principles of fuzzy logic, the membership functions of which are:
the sliding error between the setting and the measurement
the variation in the slip of the wheel with respect to the rail
a stability function calculated on the basis of the variation in the current of the electric motor and of the sliding error (equations 7 and 8).
To calculate the slip, the speed of the wheels and that of the locomotive with respect to the ground (
3
-
37
) are measured separately.
1.4—EP 0 592 288 A1—Oct. 6, 1992—Thomson CSF
The document pertains to searching for the command which maximizes the braking load produced as a function of the slip of the wheel of a vehicle with respect to a pathway, in respect of a type of adhesion which can be invoked as a function of the slip known in advance. The process described uses a fuzzy-logic regulator, the membership functions of which are:
the value of the slip of the wheel with respect to the pathway
the value of the derivative of this slip with respect to the time
the value of the derivative of the torque produced with respect to the slip
so as to act on the pressure of the braking control fluid.
The slip is obtained by differencing between two speeds every two measurements (FIG.
9
):
the speed of the wheel (
46
),
the speed of the vehicle termed the reference speed (
48
).
1.5—U.S. Pat. No. DE 4,309,183 A1 (FR 9 403 136)—Mar. 22, 1993—Siemens AG
This document pertains to a process intended for maximizing the frictional force which depends on the slip and occurs at surfaces which rub against one another, through the use of a fuzzy-logic regulator, the membership functions of which are:
the variation in the frictional force
the variation in the slip
enabling the slip to be corrected via rules expressing the necessary equality of the signs:
of the partial derivative of the load transmitted with respect to the slip, on the one hand
and of the variation in the slip, on the other hand.
The slip is calculated by differencing between the measured speed of the wheel and the measured speed of the vehicle by devices which are not described.
2—Patents Pertaining to Estimation of the Speed of the Vehicle
2.1—EP 0 716 001 A1—Nov. 30, 1995—Gec Alsthom Transport SA
The process described pertains to the estimation of an upper bound on the speed of the vehicle, to allow the determination of an upper bound on the distance travelled for example by integrating this speed, using a finite-state automaton with defined and quantified conditions of transition from one state to another. One of the states is characterized by the fact that all the wheels of the vehicle skid or jam at the same time. In this case, according to the process described, an upper bound on the speed of the vehicle is calculated by adding during braking, to the speed of the wheel, an upper bound on the slip estimated, according to claim
4
, at 15%. During wheel lock, defined as another state of the automaton, the estimate of the upper bound on the speed is no longer used.
Hence, this is not a matter of estimating the speed of the vehicle including during a transient locking of the wheels, but of defining once-off an upper bound and the conditions of validity of this calculation.
2.2—U.S. Pat. No. 5,453,942 A—Jun. 6, 1994—Westinghouse Air Brake Company
The process described estimates the speed of a railway vehicle during braking on the basis of the measurement of the speeds and decelerations of four axles during prolonged jamming. During this phase, the calculation increments, at a fixed period, the measurement of the speed of the vehicle, obtained before detecting prolonged jamming and stored, by an equal amount. This amount of incrementation is equal to the sliding average of the discrepancys, from a measurement sampled at a fixed period, to the next, of the value of the minimum speed of the four axles, which sliding average is obtained over 32 samples and is itself stored at the moment of detection of prolonged jamming.
The speed of the vehicle before detection of prolonged jamming is obtained by calculating the minimum speed of the four axles during braking before the detection of prolonged jamming.
To summarize, the process described uses an algorithm for estimating the speed of a vehicle during prolonged jamming, based on extrapolation of the speed of the axle having the minimum speed, which extrapolation is carried out by assuming that the deceleration of this axle is constant. The value of the speed and of the deceleration are the values taken by these two quantities respectively during braking and before prolonged jamming, which values are stored after processing.
2.3—U.S. Pat. No. DE 3,837,909—Nov. 4, 1988—Karl Hahn, dipl.-ing., Berlin
The process describes the estimating of the speed of a vehicle under traction and during braking, on the basis of the measurement of the speed of the motor by an incremental encoder. According to this process, an estimated value of the absolute slip, in terms of absolute value, of the wheel with respect to the rail is added to or deducted from this speed depending on whether braking or traction respectively is applied.
This value of slip is deduced from two nets of curves established a priori giving the load produced as a function of the relative slip and of the absolute speed of the vehicle. Each of these nets de
Alacoque Jean-Claude
Alamir Mazen
Bornard Guy
Latteux Patrick
Thomas Jean-Luc
Alstom Transport SA
Hoff Marc S.
Raymond Edward
Young & Thompson
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