DE2930433A1 - BLOCKED PROTECTIVE BRAKE CONTROL CIRCUIT FOR RAIL VEHICLES - Google Patents

Description

Anti-lock braking force control circuit for rail vehicles

The invention relates to an anti-lock braking force control circuit for rail vehicles with a pressure medium-actuated braking device, which has a pressure control valve and at least one brake cylinder interacting therewith, with a controller is provided, which is dependent on signals that are proportional to the wheel circumferential speed of a monitored wheel of wheel circumference deceleration or acceleration signals derived from this, of threshold value signals and of the vehicle speed emulating signals lowers the brake fluid pressure in the brake cylinder, keeps it constant or increases it. Such a braking force control circuit has become known for example from US-PS 29 14 359 (Yarber). With most of today's pneumatic and hydraulic Braking causes a brake force control (anti-lock) in principle always to raise, lower and maintain the brake pressure (see Fig. 1). The rule criteria are obtained as follows:

The braking force control requires an encoder that has a rotational speed of ¹ Y. proportional frequency f. supplies. This frequency is then used to generate (digital or analog) values for both the rotational speed ^. as well as for the rotational acceleration for ^a J ' ^{eden wheel} . This then becomes signals for

- 2 - 130021/0009 ORIGIN INSPECTED

/ r

Triggering of the anti-lock braking force control circuit obtained, by, for example, the wheel speed with a fictitious vehicle speed that is as close as possible to the actual vehicle speed is compared. An anti-lock release via differential speeds individual wheels or reaching certain threshold values of the wheel deceleration or wheel acceleration as well as the combination these criteria is possible and leads to the following states: lower brake pressure, keep brake pressure constant and Increase brake pressure, the aim of the control being to control the wheel speed so that the optimum slip is maintained between the wheel and the road.

If the wheel starts to lock, its peripheral speed r falls. Φ. steep and its circumferential lag -r. ^. exceeds a certain value - (r'P) p, which usually leads to ver

is caused that the brake pressure p. after a response time T1 according to p. = p _p .e " ^E It- ⁴ tbsp) decreases. By lowering the lui

Brake pressure can accelerate the wheel again.

130021/0009 CRI3IMAL

It is based on the idea that the wheel has left the stable state when it passes this acceleration threshold and has entered the unstable area of the braking force coefficient / braking slip curve (adhesion value / slip curve). This is particularly often not the case at the beginning of a regulation. For this reason, at the start of a braking force control, if r. ^;> _Ν ? it is true that falling below the - (r 1 ^) _E value only keeps the brake pressure (p ^ = P _F. ), while the lowering is then caused solely by the speed criterion r.Ψ ^ v-. a substitute logic can be achieved.

The tendency that the wheel does not collapse any further is indicated by the fact that the circumferential deceleration is getting smaller and smaller finally turns into an acceleration. This is again a signal that the pressure reduction must be ended. In the Main logic one achieves this in such a way that after exceeding a value (rf L, which is small and always positive, and after a response time t ~ the brake pressure is kept constant (p. =

"Al" * ·
20th

The wheel can continue to accelerate during this stopping time. If the circumferential acceleration exceeds r ^. a high value ⁺ (rf) _A > this is a sign that the friction conditions between the wheel and the roadway allow an immediate strong increase in pressure. If rH *. ^ Vi is still fulfilled in this case, the brake pressure _{is increased after a response time f A}

^μ ι ^H si L-

· ^{ * "* Αΐ * ^T * i Π

with Ί _ΛΛ = 4-Ίη -4l

* 0

raised until the acceleration has the value + {rf ). falls below again and the response time T «has elapsed. The brake pressure is then kept constant again (p. = P _ffi until the circumferential acceleration has decreased so much that it reaches the very small positive value + (r ψ ) "- (r ¹ ^) ...

130021/0009

-Y-

If the high value + (r'fL is not exceeded when the wheel is accelerated again due to poor friction conditions between the wheel and the road, or r.'f. ^ V · ,, then the brake pressure is kept constant until ⁺ (r'f ) _G - (rf L is not reached. This criterion always has the consequence that after a response time Ij the brake pressure according to the formula

^p i

r ~ -k. (t - t. + T -Π Π - e ^{A w1 w1} J

with T _wi

^{A p} si- ^p Ai is flatter than possible (k. <K _s ) is increased again (cf. FIG. 2).

The most important criteria of the main logic are secured by decisions that are based on the speed profile r ^ fj . To do this, it is necessary to simulate the vehicle speed ν well, since for reasons of cost it is not necessary to measure precisely.

The simulation of the vehicle speed is based on the measured circumferential speeds of all wheels of a wagon (or a bogie) at which deep dips are bridged in the logical evaluation by substitute straight lines. These straight lines then begin to replace the actual speed curves when the circumferential decelerations exceed a limit value - (r "f)". The slope of these substitute curves is of the same negative amount - (r ¹ ^) Brake pressure increases,

If this is not the case, ie if the brake pressure drops everywhere or if it is kept constant, then the slope assumes the smaller negative value - (r] p) _w . The vehicle equivalent speed ν is now always formed from the highest value of the circumferential speeds or their equivalent straight line.

ORIGINAL INSPECTED 130021/0009

] Based on the above-mentioned fictitious or simulated vehicle speed 7, two comparison speeds v, and v _? created by subtracting proportional and constant parts from V:

V ₁ = (ι -a _cl ) v - v _cl

V ₂ = (1 -A ₀₂ ) V- v _c2 _

If the peripheral speed falls below γ.Ψ. the comparison speed ν ,, then the brake pressure is reduced after a response time Tj as if the deceleration criterion - (r ^ Jc had been met. The same can be said for the two pressure hold commands if the speed exceeds r. * f.

the comparison speed v _? , then the brake pressure is also kept constant after the response time / £ " _r , although the acceleration threshold + {γΨ) ~ has not been reached

first.
20th

These two speed signals prevent the wheel from locking or the brake pressure if the main logic fails is completely dismantled. In order to prevent the brake pressure from remaining in a holding phase for the remainder of a braking operation, is still

^{£ J} the time tj ,. intended. It begins when, after a pressure increase, the wheel starts to lock and the brake pressure is kept constant or immediately reduced and, when it ends, causes the brake pressure to be increased sharply after the corresponding response time. The formulas already given apply.

Previous experiments have shown that the braking force _{control under consideration works best for rail vehicles if k c} rxj2 for the exponent for the brake pressure drop and for the exponent

1
for the pressure increase k .- ^ l - applies. Now, however, the volumes of the brake cylinders in the individual rail vehicles can be between

130021/0009

] 2.5 1 and 7.5 1 and more fluctuate. As a result, that Pressure control valve for the respective brake cylinder; set must become. So far, this has been done by exchangeable nozzles in the pressure control valve or by a valve with a unitary effect.

I Lately has been used for all types, especially for reasons of cost

a uniform and inexpensive pressure control valve for rail vehicles required. An adaptation of the brake force control to the different brake cylinders through exchangeable nozzles in the pressure IQ control valve or a valve with unitary action is therefore no longer acceptable.

The object of the present invention is therefore to provide an anti-lock To create braking force control circuit for rail vehicles of the type specified above, in which using a pressure control valve and at least one brake cylinder that is not specially adapted to the pressure regulating valve, an optimal brake pressure curve is achievable. - J

This object is achieved by the present invention in that that the pressure control valve is designed so that the largest occurring volume of possible brake cylinder still = an optimal one Brake pressure curve can be achieved and that the controller is designed so that with a smaller volume of the brake cylinder the actual Brake pressure curve as a function of the signals mentioned over alternating pressure increase and pressure holding phases or alternating ones Pressure drop and pressure holding phases are approximated to the optimum brake pressure curve with a period of time that can be set by the controller. Beneficial Refinements and developments of the invention can be found in the subclaims. Essentially weÜ with the present So the invention uses a pressure control valve with invariable nozzles that are dimensioned so that for there? largest occurring Brake cylinder volume the optimal values for the brake pressure drop or the increase in brake pressure can be achieved, the actual brake pressure profile via a pulsing process to the

130021/0009

ORis;

η is adapted to the optimum brake pressure curve. With smaller brake cylinder volumes, the excessively steep brake pressure changes are flattened by pulsing. According to an advantageous development of the invention the times for the pressure rise and drop in pressure c case phases fixed, while the periods of pressure maintenance phases can be changed, after a further embodiment of the invention, the pressure holding phases are linked by factors with the pressure rise or pressure drop phase . The optimal brake pressure curve is thus optimally set by selecting these factors IQ (a. And a.-). These factors - as will be described in more detail below - are determined iteratively and, if necessary, changed so that the braking force control and thus the optimal braking pressure curve are adapted to the actual conditions of the braking.

Of course, it is also possible to set the times of the pressure increase and to make pressure drop phases adaptively variable, it being noted that these time intervals are not in principle mit.der measuring time of digital braking force control loops related. However, the complexity of a digital logic is considerably reduced if these time intervals are multiple the measuring time.

The invention is described below using an exemplary embodiment explained in more detail in connection with the figures. It shows:

Figure 1 shows the brake pressure curve of a general braking force control circuit;

Figure 2 shows the timing of the wheel circumference acceleration

supply or deceleration of the wheel circumferential speed and the regulated brake pressure ^;

FIG. 3 shows the time profile of the wheel circumferential speed for several control cycles and the time

130021/0009

2330433

Course of the simulated vehicle speed;

FIG. 4 shows a block diagram of the braking force control circuit according to the invention;

FIG. 5 shows the brake pressure curve over time in the brake force control circuit according to the invention;

, Q Figure 6 shows the brake pressure curve and the wheel circumferential speed for a control cycle in the braking force control circuit according to the invention; and

FIG. 7 shows a representation of the wheel circumferential acceleration, ic the wheel circumferential speed and the mean

Brake pressure over time in the braking force control circuit according to the invention to explain this Working principle.

FIG. 1 shows the principle of the brake pressure as a function of time in a conventional braking force control loop with the phases: "raise", "Lower" and "Hold".

FIG. 2 shows the time course of the wheel circumferential acceleration as a function of the wheel circumferential speed and the brake pressure of the regulatory criteria described above.

FIG. 3 shows the wheel circumferential speed and the simulated vehicle speed for several control cycles. Details about Figures 2 and 3 were explained in the introduction to the description and need not be repeated here.

FIG. 4 shows a block diagram of the braking force control circuit according to the invention. A monitored wheel 1 of the vehicle is coupled to a generator 2, which is one of the peripheral speed of the wheel indicating a proportional signal to a wheel slide protection device 3. The wheel 1

130021/0009 ORIGINAL INSPECTED

is braked via a brake 4, the brake 4 being actuated via an anti-skid valve or brake cylinder 5. The anti-skid valve or brake cylinder 5 is pneumatically or hydraulically connected to a pressure control valve 6, which in turn is connected to a Pressure vessel 7 is connected. A manual brake actuation initiated by the driver of the vehicle works in a known manner on the pressure control valve, whereby the anti-skid valve 5 is actuated the braking process is carried out accordingly via the anti-skid device 3 the above criteria are monitored, whereby between the sliding

_{Devices connected in the} protection device 3 and the anti-skid valve 5 are provided which, depending on the signals mentioned, provide for a pressure increase 8, a pressure decrease 9 and a pressure maintenance 10. Furthermore, devices 11 and 12 are provided, which are assigned to the devices 8 and 9 and devices for the

■ each learning process for the pressure increase or the learning process for the pressure reduction included, over the devices 11 and 12 thus the factors a. or a _{E is} determined. The anti-skid device 3 and the devices 8 to 12 represent the controller of the braking force control circuit according to the invention.

FIG. 5 shows the time curve of the brake pressure in the pressure drop or pressure increase phase. Both with waste and when the brake pressure rises, there is between the exponent k * of the unregulated pressure curve and the exponent TT of the mean one pulsed pressure curve the relationship

TT = k ___

In this case, η denotes the number of holding phases and a denotes the above-mentioned ones Factors a. respectively.

For η = 1 it follows
35

k *
_ki = 5_

ORIGINAL

130021/0009

while for η? oo we get:

k *

1 + a

From this it can be seen that at the beginning of a pulsed pressure drop or increase (n = 1) the k-value is greater than after (n -> <*>), where an approximately constant ¥ is expected can. This is beneficial for the control because the hysteresis of the brake can be overcome even more quickly.

In order not to shorten the service life of solenoid valves the number of holding levels is limited, for example to four. This means that the brake pressure change is then unpulsed he follows,

If one chooses the times of the pressure increase or pressure decrease phases or β-- constant and the pressure holding phases according to a. (For the pressure increase phase) or a _E ^ p (for the pressure decrease phase), then the Y values (Fp - or k. for brake pressure reduction or brake pressure increase) on the selection of the two factors a _F (brake pressure reduction) and a. (for the brake pressure build-up). The two sizes a, - and a. must be linked with the control logic, whereby in the present invention the factor a _{p is determined} solely from criteria at the end of the pressure reduction phases

becomes, while the factor a. from the data at the end of a brake pressure increase (with one exception to be explained later).

It can be shown that, for example, the venting or aeration times are not suitable quantities to reduce the factors a _E or a. to be determined. This data depends not only on the k values, but also heavily on the brake hysteresis, vehicle data, the friction conditions and the controller data. According to an advantageous development of the invention is therefore

suggested the optimal a _E and a ^ values iteratively

- 11 -

130021/0009

to find. This way is explained below in connection with FIGS. 6 and 7. It is assumed that the speed V (Figure 7), which simulates the vehicle speed ν as closely as possible,

where two reference speeds v, and v " can be derived from this that obey the following regularities:

V ₁ = (1 - Λ _Γΐ ) ^ν - ν,
^{: cl cl}

where V _{1 is} always smaller than V ₂ and v _{2 is} always smaller than ν.

A pressure increase was therefore favorable in terms of time when the brake pressure lowering threshold - (r) _{E was undershot if}

starting speed of the wheel ^r ^ f . between v _? and v, lies.

The factor a. in this case has a favorable value that does not need to be changed. Applies for this criterion, however ^kt fi L · ^V 2 ^{"as bede} ood that that the ventilation was made too steep, a _A is therefore to increase, which in logic by the command

a " ⁼ a. + / \ a.

/ Λ / Λ γλ

is realized. ^ a. symbolizes a constant value with which a _{ft is} optimized. If, on the other hand, the peripheral speed falls below r. Ψ. the comparison speed v «becomes the substitute condition r. ^ P. ^ _ V. met, then

the increase in brake pressure was too flat and a. is to be reduced:

^a A_

ORIGINAL INSPECTED

- 12 130021/0009

λ Care must be taken that a _ft never becomes negative. At the beginning of a controlled braking, a _fl = 0 must be set so that the

Pulsing can adapt to each brake cylinder.

The link between the factor a _£ and the difference in the wheel circumferential speed / χν _Ε , which develops during the venting phase, because during this time the circumferential acceleration rg ?. is negative and positive, i.e. the circumferential speed first decreases and then after passing through its minimum, Q increases again. As a rule, the increase in speed is small until the acceleration threshold + (γΦ) _{ε is} exceeded. / \ v _F is then a suitable quantity to influence _{the factor a p.}

• J5 In the case of very poor friction conditions, it can it can happen that the wheel revs up long before this criterion is reached will. This difficulty is circumvented by specifying the speed differences to be aimed for and the logical ones Traces decisions back to times calculated from them.

7 primarily shows the brake pressure and speed curves and acceleration during a venting phase. In

the time span ^ \ T, the acceleration is always smaller than - {rf ) p, while between T and T + aJ "its value changes from - ( ^Γ ^) ρ ^au ^ ⁺ ( ^{r <} f ) r . If one takes approximately a constant acceleration value - (rY) _c during λΤ and during

- P L ··

/ \ T _fi a linear change in acceleration between - {r ^) ^ and an, then ^ v is calculated. to

.Δν _Ε = - (rf) _E

Is one now based on the idea that with a favorable braking force control the speed difference / \ yp always values between v _? - v. and V - v, should assume the following logical decisions:

- 13 -

130021/0009 v-r ■ '-

a) If the acceleration threshold + (r'f *) _{ß is} exceeded and it applies

^v o " ^v i" ^{d <n <}

> 2-

R,

then the time course of the pressure drop was favorable and the factor a _E does not need to be changed.

b) On the other hand, one registers with this criterion

then this means that the vent was too steep, so it is to be increased, which is indicated by the instruction

A ^a _E

is realized. / \ a _p again represents a constant value that needs to be optimized. At the beginning of every braking force control, a _F must of course be set equal to zero.

c) If one finds that / \ v _F >; VV ₁ , ie

V- V ₁

is fulfilled, the wheel may lock up (e.g. as a result of a sudden change in the coefficient of friction). In order to prevent this under all circumstances, a _f = O must be set immediately. In this case, one must not wait to see whether the + (r ^ f) _G ~ threshold is exceeded, but this criterion must be monitored during the entire venting phase.

- 14 -

130021/0009

For all these decisions, the time must be determined with the help of logic. If the acceleration value - (r'fjp is not undershot when the pressure drops, which can happen with very poor adhesion when the wheel no longer comes up, then ^ \ T = 0 and the time period ^ \ J _E from the point in time Ψ to count.

. The above can also be described as follows

_{(cf. FIG. 6): A pulsed pressure increase was favorable in terms of} control technology if shortly before its end, ie at the moment of the decision, the wheel speed v _R lies between _{two limit speeds v and v o} . The size a _ß in this case has the optimal value, which is retained. Applies against it
v _R => v «, this means that the ventilation was too steep,

a. So it has to be increased the next time the pressure rises

Time v _{R fell} below the limit speed v «, then was

the increase in brake pressure too flat and a. is for the further Downsizing scheme.

In "the selection of a _E , it is assumed that with a favorable braking force control during a pulsed pressure reduction the greatest difference in wheel speed ^

V | j |

(the drop in speed) always values between ^ / \ y.

and A ^ is to assume _1V. If this is determined at the end of the lowering phase, then a _F does not need to be changed. Registered

on the other hand, if at this moment / \ yu SL ^ ^V · » ^this means that the venting is too steep, a _{E must} therefore be increased for the next pressure drop. If, on the other hand, one recognizes at any point in time during the venting phase that ^ A »v _M >_<i / \ v has become,

then there is a risk of the wheel locking. To do this among all 30

To prevent certain circumstances, a _£ is to be set to zero immediately so that the brake cylinder is vented with the greatest possible steepness.

All mentioned in the description and evident from the figures technical details are important for the invention.

13 0021/000 9 _orig1 times inspected

Claims (3)

Knorr-Bremse GmbH Munich, May 14, 1979 Moosacher Strasse 80 TPIl-Dr.v.BU / so 8000 Munich 40 Claims - _n ^ anti-lock braking force control circuit for rail vehicles with a pressure medium-actuated braking device, which has a pressure control valve and at least one brake cylinder interacting therewith, a controller being provided which, depending on signals that are proportional to the wheel circumference speed , c ity of a monitored wheel, derived from this, the wheel circumference deceleration or acceleration signals, of threshold value signals and the vehicle speed simulating signals lowers the pressure medium pressure in the brake cylinder, constant holds or increases, characterized in that - The pressure control valve (6) is designed so that the largest Occurring volume of possible brake cylinder (5) still an optimal brake pressure curve can be achieved - and that the controller (3, 8 - 12) is designed so that with smaller volumes of the brake cylinder (5) the actual brake pressure curve as a function of the signals mentioned over alternating pressure increase and pressure holding phases (an? \.) or alternating pressure drop irSv) and pressure holding phases ( ²¹ F ^ V) The optimal braking pressure curve is approximated with a time period that can be set by the controller. 2. Braking force control circuit according to claim 1, characterized in that - that the pressure rise - (^) and pressure drop phases (^) a - 2 130021/0009 2
predetermined fixed period of time and the pressure holding phases (a »<&"', a _£ o9 "r :) have variable periods of time which can be set by the controller (3, 8-12). 3. Braking force control circuit according to claim 2, characterized in that the pressure holding phases have a correspondingly adjustable factors (a. Or a _c ) changed time duration compared to the time duration of the pressure increase or pressure decrease phases (, J ". Or ^ J p). 4. Braking force control circuit according to claim 3, characterized in that the factors (a »or a _E ) add _G SiP £ n control cycle as a function of the signals mentioned shortly before / the entire pressure rise or. Pressure drop phase of a previous control cycle can be determined. 5. Braking force control circuit according to claim 4, characterized in that the factors (a. Or a _F ) in the first control cycle are equal to zero and in further control cycles by a predetermined value (Aa _n or Aa,.) Are increased or decreased or constant * ^{υ be} kept. 6. Braking force control circuit according to one or more of claims 3 to 5, characterized in that the factor (a ») for the Constant holding phases during a _r brake pressure increase cycle following before the end "de sizes if short / des this brake pressure increase cycle the following conditions occur: ^a An ^{= 3} An-I ^{if V} l < ^V R < ^V 2 ^a An ^{= a} An-l ⁺ Δ * _A if v _R > ^a An ⁼ where a »is the factor for a brake pressure increase cycle (n), ³ An 130021/0009 INSPECTED a », the factor for the previous brake pressure increase cycle (n-1)
/ \ a. is a constant, predetermined value, v _{D is} the peripheral speed of a monitored wheel, κ v. and V _? quantities generated are proportional to the simulated vehicle speed Y, where V) ■ v _? } v .. is. 7. Braking force control circuit according to one or more of the claims 3 to 5, characterized in that the factor (a ^) for the Constant holding phases during a Bremsdruckabsenkzyjclus following Sizes assumes: - ^a c ι if the following applies at the end of the brake pressure reduction cycle: Av - < min a _c = a _c , + AAr if at the end of the brake pressure reduction cycle tn tn-i - * t the following applies: _A v _E. a _E = 0 if at any point in time of the brake pressure reduction cycle; where a _{E is} the factor for a brake pressure reduction cycle (ti), a _{p is} the factor for the previous brake pressure reduction cycle (n-1).
j \ Ac is a constant, given value, / \ y _{c is} the difference between the wheel circumferential speed t the minimum at the beginning of the brake pressure reduction cycle and / of the wheel circumferential speed is during the brake pressure reduction cycle, first specified fixed value, / \ V. is a second predetermined fixed value, where ⁿ and wherein the end of the brake pressure reduction cycle is determined in that the wheel circumferential acceleration is a predetermined, exceeded positive threshold. - ^130021/0009 ORSGim INSPECTED