DE2124344A1 - - Google Patents

Description

212A3W

ALFRED TEVES GMBH February 11, 1971

Frankfurt (M) SL / Mit / Rie

P 3448a

H.G. Klein, G. Werner - 66,

Method and device for determining the rotational delay of a Vehicle wheel for anti-lock control systems

Addendum to patent

(Patent application file number P 16 55 447.5-21)

The invention relates to a method and a device for determining the rotational deceleration of a vehicle wheel for anti-lock control systems and represents a further refinement

the subject of the invention according to the patent

(Patent application file number P 16 55 447.5-21).

With increasing size and possible speed of today's motor vehicles and their increasing number road traffic is more dangerous every day; therefore, efforts are made to use brake systems with anti-lock control systems as far as possible equip. Some of these control systems influence or regulate the braking force as a function of the instantaneous Rotational acceleration or rotational deceleration of the vehicle wheels in order to block them and thus to block them ineffective braking or to prevent the vehicle from skidding.

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These devices have mostly been equipped with accelerometers that pass through or together with the vehicle wheels were driven. These acceleration meters "include all parts that are subject to severe wear and tear (such as grinding brushes, Slip rings or the like) and which are also disadvantageous because they are due to the wear during the Can contaminate operation and thereby the entire device may be put out of operation. Besides, these are Accelerometers are often highly inaccurate because they are almost complete build on mechanical measuring devices.

The object of the invention is to propose an improved method for the precise measurement or determination of the rotational acceleration, that is independent of wear-sensitive or dirt-sensitive parts that are attached to the wheel.

In addition, a device for performing the proposed Method are created that generates a signal proportional to the rotational acceleration, which is used for actuation an anti-lock control system of the type described can be used.

This is achieved according to the invention in that two magnetic members are fixedly rotated by 90 ° against each other and these output signals IL · = U sin wt and U ₂ = U _Q cos wt depending on a magnetic flux, the functions only of the angular velocity of a magnetic field and are phase-shifted by 90 ° with respect to one another, where w is the angular velocity and IJ _{0 is} a frequency-independent constant. A permanent magnet is set in rotation together with the vehicle wheel in the area of the magnetic members, so that these are exposed to the action of the magnetic field rotating at the angular velocity w of the vehicle wheel. Of the emerging

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Voltage _{signals U 1} and U "become the second derivative close to the time U. and Ü _o formed and the signals thus obtained are according to the relationship m ψ = Ü. . U "- Up. U. processed, where m is a constant.

First of all, the output _{signals U 1} and U _{9 are} differentiated to generate signals which U ^ and U "correspond to the first derivatives according to the time of the signals U ₁ and Up, each of these signals U. and Up is differentiated one more time the second derivative after the time Ü. and get up.

The mentioned magnetic members can be Hall effect crystals in one embodiment, through each of which a constant current is sent in one direction. They become in a direction perpendicular to this first direction Hall effect crystals are then exposed to the field lines of a magnetic field, and the voltage signals U. and Up are tapped on these crystals in a third direction that is perpendicular to the first two.

In another embodiment, these magnetic members can be magnetoresistors that were connected in series with a load resistor to a voltage source emitting a constant voltage, the signals U ₁ and Up are tapped at the load resistors.

A device according to the invention thus includes a pair of magnetic members rotated by 90 ° relative to one another for generation two sinusoidal output signals U .. and Up, phase-shifted by 90 °, the frequency of which is a function of the The angular velocity of a rotating magnetic field penetrating the magnetic members is, however, its amplitude depending on the direction of the magnetic field, but independent

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is of said frequency. The magnetic field is generated by a permanent magnet connected to the vehicle wheel and rotatable with it. Means are also provided for generating the signals U ₁ and U _{o representing the second derivative according to the time of the signals TJ 1} and U ₀ and means for processing the signals obtained Signals according to the relationship m ψ = Ü. .U ₀ -

■ -2

U ₂ . U ₁ , where m is a constant.

In one embodiment, the magnetic members are Hall effect crystals through which a constant current flows in one direction and which are exposed to a magnetic field in a direction perpendicular to this first direction. The voltage signals U. and U _? can be tapped on the crystals in the direction perpendicular to the first two.

In another embodiment, the magnetic members are magnetoresistors, each with a load resistor and a voltage source emitting a constant voltage in Are connected in series; the voltage signals U. and U "are can be tapped at the load resistors "

The device has two differentiators for generating the signals TL and U ₀ , which represent the first derivatives with respect to time of the signals U. and Up, and two further differentiators for generating the signals U ₁ and U _2, which are the second derivatives after the time of the signals U ₁ and U _? represent.

Two multipliers are then provided for generating the products U ₁ U „and U.p U ₁ and an Ade
Output signals of the multipliers,

Products U ₁ and Up U ₁ and an adder for subtracting the

The invention thus takes advantage of the fact that around 90

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phase shifted sine waves of the sine and oosine function correspond to the same wave signal.

In order to reduce wear as much as possible, the generator used consists of two identical magnetic members, which, rotated 90 against each other, on a common Axis are mounted. This way, only the shaft bearings that must be present in each pail are subject to wear and exposed to pollution, which is a noticeable advantage over what is known so far.

The logic circuit provided in the device according to the invention takes advantage of the fact that the signals are always in the same relationship to one another in terms of their phase, but they are variable ! Frequencies, and calculates the angular acceleration using the relationship

U ₁ U ₂ - U ₂ U ₁ = ηι ² γ> (t) where U _{1 is} an amplitude of one signal, Up is the corresponding amplitude of the other signal,

if (t) is the second derivative of the angle of rotation with time and, as a result, the angular acceleration O <.

2 2 2

m = U ₁ + Up is almost a constant, the value of which depends

of the voltage, resistance or current amplitudes, in which the value of the signals is determined.

While normal voltage generators are used, consisting of a permanent magnet and an induction coil, it is possible to provide differentiation circuits that the Might linearity of the frequency dependence of the output signals

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(ie the constancy of the expression U or the multiplier of the frequency-dependent expression eliminated), voltage generators are used according to the invention, in which the output variable is solely a function of the frequency, as defined by the following expressions U = U sin ψ or U = U cos ψ . According to the invention, this is achieved by means of magnetically influenceable members which are arranged offset from one another by 90 ° and have a resistance or conductivity which is a puncture of the magnetic flux passing through them. Such a link is e.g. B. a Hall-effect crystal, which is fed perpendicular to each other with an electric current and a magnetic flux and emits an output signal that can be picked up perpendicular to the electric and magnetic field, the magnetic field being a function of the variable input signal. Another useful arrangement is a magnetoresistance, the ohmic resistance of which changes linearly with the flux passing through it.

The invention is described in more detail below with reference to the accompanying drawings.

Fig. 1 is a graph showing the relationship of the two sine wave output signals before differentiation according to the principle of the present invention;

Fig. 2 shows in a sketch the principle of the Hall generator;

FIG. 3 shows a block diagram of the logic circuit which is fed by the output signals of the generator according to FIG will;

Fig. 4 shows the sketch of an influencing the braking force

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Control loop for a motor vehicle, wherein the principles of the present invention are applied ;

5 shows the sketch of a signal generator in which magnetoresistors be used;

Pig. 6 shows the circuit diagram showing the connection of the magnetic Member of a device according to FIG. 5 illustrates.

As already stated above, it is an important basic idea of the present invention to provide a new system for generating output signals which can be used to influence the braking force in the anti-lock control system of a motor vehicle. The method according to the invention uses a generator which contains a magnetic member, indicated at 9a in FIG. 2. If this magnetic member represents a Hall-effect crystal with a prismatic shape, so that an electric field (arrow A) running through two surfaces of the crystal can be applied by a generator 100 delivering a constant current, a magnetic flux φ runs between two other opposite faces of the crystal at right angles to the electric field. As a result, a voltage difference U can be picked up at two connections which are connected to a further pair of the opposing surfaces, since a further field is generated at right angles to the applied electric field and the applied magnetic field. If one of the two applied fields is constant, then the output U is a function of the other. So if a current source is used that provides a constant current, then the output voltage U is a function of the magnetic flux and, as already noted above, changes with the frequency and only with the frequency. The initial

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voltage is therefore U = U sin wt. U is determined by the constant current flowing through the crystal and is not a function of frequency.

In the system according to FIG. 4, the vehicle wheel 21 is connected via a shaft 12 to a magnetic yoke 101, between the pole pieces 102 and 103 of which there is a radial magnetic field. The magnetic members 9a and 10a of a pair of sine wave generators 9 and 10, the output voltages U and U _{2 of which are} exclusively frequency-dependent, as already described above, are fixedly arranged in this field and with it in one plane. The magnetic members 9a and 10a are fed by a constant current supplying current source according to FIG. 2 and operate according to the principles of the Hall effect.

FIG. 5 shows another arrangement which can be used as sine wave generators 9 and 10. In this embodiment, a permanent magnet 104 is arranged on the shaft 12 and is connected between two diametrically opposite pairs of magnetic resistors 9a ¹ , 9a ¹ 'and 9b', 9b ¹ ', which are connected by a magnetic yoke, indicated by dashed lines, in Offset. As illustrated in FIG. 6, each of the magnetoresistors 9a ¹ , 9b ^{f is connected} in series to a voltage source 105 which emits a constant voltage and to a las twiders taiid 106 at which a voltage drop U is generated. If a magnetic field changes the ohmic resistance of the members 9a ¹ , 9b ¹ , 9a ¹¹ , 9b ¹¹ , this change in resistance is noticeable in a change in the current flowing in the circuit according to FIG Resistor 106, here too U = U sin wt.

The respective output voltage of these generators 9 and 10

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are fed into a logic circuit 1, which processes them in accordance with the laws described below and determines the angular acceleration o (of the wheel 21. The output signal of the logic circuit 1 is fed to a valve arrangement 23, which influences the brake pressure in the pressure medium line between the master cylinder 24 and the wheel brake cylinder 22 The braking process is thus carried out as a function of the angular acceleration cK of the wheel 21 in order to avoid locking of the wheel 21 and thus ineffective braking.

Mg. 1 shows a graphic representation of the two output _{signals U 1} and U ₂ , their amplitude (e.g. voltage, current) being plotted on the ordinate and the angle of rotation on the abscissa. As can be clearly seen, the two sinusoidal voltage signals U. and U ₂ are phase-shifted by 90 °. This known phase difference is the reference variable in relation to which the angular acceleration oi is measured.

3 shows the logic arranged between the braking force regulating valve 23 and the sine wave generators 9 and 10 Circuit.

The sine wave generators 9 and 10 generate the signals

U ₁ = U ₀ sin wt or U ₁ = U _Q sin <p (1)

U ₂ = U cos wt or Up = U cos ψ (2)

The voltage signals U and U ₂ are each fed to a differentiator 13, 14, which form the first derivatives with respect to time:

U ₁ = U ₀ cos «f? '« P (3)

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_ = - U ₀ ζύιψ'ψ (4)

Y = ti (5)

German

The signals U ₁ and U ₂ are each fed to a further differentiator 15, 16, which form the functions:

U ₁ = U ₀ .If cos * P - U _o (* J?) ² sin <f>"(6)

U ₂ = - U _Q. ψ sin ψ - U _Q (tj?) ² cos «p (7)

Cp = ^ Ψ . (8th)

German ²

For better handling and to avoid confusion, the constant U is replaced by the constant m.

In the next. Level, the products Ü. . U ₂ and U ... U ₂
be formed according to the following relationships:

U ₁ . U ₂ = + m ² . ψ . eos ² <p - m ² (ψ) ² sin * p. cos ψ (9) U ₁ . U ₂ = - m ² . ψ. sin ² <f - m ² (ψ) ² sin * f cos <p (10)

The multiplication is carried out in multipliers 17 and 18, the output signals of which are an algebraic
Summing circuit 19 is supplied, in which the subtraction is carried out:

U ₁ U ₂ - U ₁ U ₂ = m ψ t (sin ψ + cos ψ) (11)

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(sin ² <f + cos ² cf) = 1 is (12)

you get

U ₁ -U ₂ - U ₁ U ₂ β Hi ² Cp (13)

The two signals U ₁ and U _{2 of} the generators 9 and 10 are both differentiated twice in the differentiators 13, 15 and 14, 16, respectively. These second derivatives near the time U ₁ and Ü _? are fed into multipliers 17 and 18 in order to obtain the two products U ₁ U "and U ₁ U ₂ . An adder circuit 19 subtracts the second of these two products from the first and outputs a signal which corresponds to equation (13) and is therefore proportional to the angular acceleration.

Although the invention is based on the particular example of a motor vehicle brake system as described, it can be used in any system that provides an accurate measurement of the Requires angular acceleration. Also, although the use of alternators 9 and 10 in this System is desirable, generators can also be used, which generate a sinusoidal resistance or current signal.

The invention described allows numerous improvements and modifications without affecting the basic concept as set out and claimed again in the following claims will be left.

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Claims (1)

Claims experience to determine the turning deceleration of a vehicle wheel for anti-lock control systems according to patent (Patent application file number P 16 55 447.5-21) characterized in that two magnetic members are fixedly rotated by 90 ° against each other and _{emit sinusoidal output signals U 1} = U sin wt and Up = U cos wt depending on a magnetic flux, the functions only the angular velocity of a magnetic field and each other are phase-shifted by 90 °, where w is the angular velocity and U is a frequency-independent constant that a permanent magnet is set in rotation together with the vehicle wheel and in the area of the magnetic members, so that this has the effect of the are exposed to the angular velocity w of the vehicle wheel rotating magnetic field, that of the signals U ₁ and Up, the second derivative after the time Ü, and Ü _{o is} formed that the obtained Signals according to the relationship m = U ver where m is a constant. Yerfahren according to claim 1, characterized in that the output _{signals U 1} and U ^ are differentiated to generate signals which U ₁ and Up thus correspond to the first time derivatives of the signals U ₁ and U ₉ , and that each of these Signals U. and U _{2 on} - 13 - 209833/0578 - 13 - P 3448a additional. Times are differentiated in order to receive the second instructions after the time Ü .. and U ₂ . 3. The method according to claim 2, characterized in that these magnetic members are Hal-effect crystals (9a, 10a), through which a constant current is sent in one direction and in a direction perpendicular to this first direction Field lines are exposed to a magnetic field and that the signals U ₁ and Up are tapped in a third direction perpendicular to the first two at these crystals (9a, 10a). 4. The method according to claim 2, characterized in that these magnetic members are magnetoresistors (9a ¹ , 9a ¹¹ and 9t » ¹ , 9t» ¹ ') which with a load resistor (106) in series to a voltage source emitting a constant voltage ( 105) are connected, and that the signals U ₁ and U ₂ are tapped at the load resistors (106). 5. Device for performing the method according to one of the preceding claims, characterized by a pair of mutually rotated by 90 ° magnetic members for generating two sinusoidal, 90 ° phase-shifted output signals U. and U ₂ , the frequency of which punctures the angular velocity of a rotating the magnetic Members penetrating magnetic field, the amplitude of which is dependent on the direction of the magnetic field but independent of said frequency, also characterized by a permanent magnet connected to the vehicle wheel and rotatable with it for generating a magnetic field penetrating the magnetic members, by means for generating the second 209833/0578 " ^U " - 14 - P 3448a Derivation according to the time of the signals F. and U ₂ representing signals U ₁ and U ₉ , and by means of processing 2 * of the signals obtained according to the relationship m «^ = U ₁ . Q 1 U ₂ -Up. IL, where ra is a constant. 6. Apparatus according to claim 5, characterized in that that the magnetic members are Hall effect crystals (9a, 1Oa), through which each in one direction constant current flows and a magnetic field in a direction perpendicular to this first direction are exposed and that the voltage signals U. and IT «on the crystals can be tapped in the direction perpendicular to the first two. 7. The device according to claim 5, characterized in that the magnetic members are magnetoresistors (9a ¹ , 9a ¹¹ and 9b ^f , 9b ¹¹ ), that these are each with a load resistor (106) and a constant voltage emitting voltage source (105) in Are connected in series and that the voltage signals U and Up can be tapped off at the load resistors (106). 8. The device according to claim 5, characterized by two first Mfferentiatoren (13, 14) for generating the signals U. and U ", which represent the first derivatives according to the time of the signals U, and Up, and by two further Mfferentiatoren (15, 16) to generate the signals Ü ^ and ϋ _? which represent the second derivatives with respect to time of the signals U ₁ and U ₂ . 9. Apparatus according to claim 8, characterized by two multipliers (17, 18) for generating the products U ₁ U ₂ and U ₂ U ₁ . - 15 - 209833/0578 - V5 - P 3448a 10. The device according to claim 9, characterized by an adder (19) for subtracting the output signals of the multipliers (17, 18). 209833/0578