DE2844279A1 - Electronic control for antilock brakes - uses AC signal from wheel speed sensors as input for digital control - Google Patents

Abstract

The anti lock brake control uses wheel speed signals in the form of impulses related to the speed. These are processed by a digital control and a programmed anti lock control to provide optimum braking control related to the dynamic state of the vehicle. The wheel speed pulses are generated by AC generators on the wheels and are translated into digital signals. The main control uses a programmed processor which can be set to cater for most types of vehicle, so that the control becomes a universal fitting.

Description

Hanover, October 2nd, 1978 Wabco Westinghouse GmbH UP 26/78 Dr.K.

Method for regulating the brake pressure in anti-lock vehicle brake systems

The invention relates to a method for regulating the brake pressure in anti-lock vehicle brake systems according to the preamble of claim 1.

It is known for the generation of control signals for controlling the brake pressure in anti-lock vehicle brake systems to use special procedures and special circuit arrangements, which are usually customer-specific and must be structured specifically for the type. These have the disadvantage that they are not compatible and for further developments and improvements, as well as changes and adjustments to changing parameters, always new methods and circuit arrangements have to be developed and set up, which time- and is unfavorable in terms of cost.

The present invention is therefore based on the object of specifying a method of the type mentioned at the beginning, through which further developments, adjustments, changes and improvements can be carried out faster and more cost-effectively

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are, in particular, more familiar to the use per se programmable microcomputer is intended.

According to the invention, this object is achieved by the characteristics of claim 1 specified measures solved.

The main advantage of the solution according to the invention is to be seen in the fact that with the help of the microcomputer through Program change a solution to a variety of problems can be found without having to set up a new customer circuit each time. The procedure is not more type and customer specific.

Further refinements of the invention are characterized in the subclaims.

The invention will now be explained in more detail with reference to the accompanying drawing, in which exemplary embodiments are shown will.

Show it

1 shows a block diagram to illustrate the signal flow from the rotary encoder (Sensor) to the solenoid valve, Fig. 2 is a flow chart for illustration

the overall process with the process steps for computer preparation and the actual process for obtaining the control signals,

3 shows a flow chart of a higher-level interrupt program for control

030016 / 0A57 - ¹² ~

the correct execution of the main computer program,

Fig. 4 is a flow chart of the program for obtaining the acceleration and Deceleration control signals,

5 shows a flow chart to illustrate the method for obtaining the slip control signals;
Fig. 6 is an illustrative flow chart

the method for the logical combination of the determined control signals and generation the control signals necessary for controlling the brake pressure and FIG. 7 shows a pulse diagram to explain the interrupt and the logic program according to FIGS. 3 and 6.

The reference variables that are fed to a microcomputer must be digitized in order to be processed by it to be able to. This digitization is carried out by an input circuit - not described in detail here carried out, to which is indicated in Fig. 1 with the reference numeral 2 and that of a scanning the wheel course Sensor 4 obtained analog measured variables are fed. The digitized analog measured variables are stored as data words in given a buffer 6 and from this via a multiplexer 8 from the computer 1o for the purpose of obtaining control

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Signals retrieved. The control signals are then fed to solenoid valves 14 as manipulated variables via amplifiers 12.

The conversion of the measured variable present in the form of an alternating voltage takes place by counting into the duration one period falling counting pulses of a pulse generator (not shown). To count the counting pulses preferably two counters are used, one of which at the beginning of the negative half-cycle of the AC voltage and the second is started at the beginning of the positive half-wave. The counting time goes over a full period.

The data word is called up via a multiplexer, which can be addressed by the computer, and arrives via a serial data line to the computer.

The binary data word that corresponds to the period of the sensor signal or corresponds to the period of the square wave signal, is always in the buffer as the current value 6 and can be received by the following computer 1o. This data transfer can take place in parallel as well take place serially. For reasons of the necessary number of connections, a serial transmission method is selected here.

Reference should now be made to FIGS. 2 through 6, in which the various flow charts are illustrated which are essentially self-evident, so that it is only necessary to give a few supplementary explanations admit.

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030016/0457

In addition to the overall program scheme according to FIG. 2, it should be noted that the interrupt program (see FIG. 3) is blocked in order to prepare the computer and to be able to load the initial values independently of the interruption program. All initial values are loaded into a dynamic register. For example, the differentiator time base, the reference time base, the differentiator reference variable and the slip signal reference variable are loaded, with in particular all speed values according to a specifiable minimum value or all period duration values according to the corresponding one maximum value can be set and loaded.

The differentiator and slip value generation programs 4 and 5 is essentially the subject of German patent application P 26 31 227 "Method and device for regulating the brake pressure in anti-lock vehicle brake systems ".

The logic program according to FIG. 6 is essentially based on the German patent applications P 26 55 165 "method and Device for regulating the brake pressure in anti-lock systems "and P 27 17 383" Circuit arrangement for regulation of the brake pressure in the control phase in anti-lock vehicle brake systems ".

To explain the essential parts of the interruption program (real-time-dependent interruption program) and the logic program, reference should be made below to FIGS. 3, 6 and 7 and the implementation of the pulsed Pressure control are described.

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28U279

It should be assumed that after the acceleration signal + b has dropped, a pressure build-up phase takes place in which the pressure gradient is controlled by criteria not described here in such a way that the pressure control time and the pressure hold time form a ratio that is optimally adapted to the control behavior. After the + b signal has dropped, the logic program creates the initial condition for the time start of the time TV1, which is characteristic of the entire pulse phase, see fourth, fifth and sixth signal sequence from the top in FIG is, ie the time TV1 has not expired, the program part for the pulsing in the timer interrupt program (FIG. 3) is run through. The registers in which the times are formed by subtracting a value after each defined time unit are decremented. The pulsing is characterized by holding times TV ₁ and control times TV _ (which can also be the same) of the brake pressure, see Fig. 7. The logic program determines the time at which to start by setting or resetting a corresponding mark MH, where the mark "MH set" is the mark for holding pressure and the mark "MH reset" is the mark for pressure control. Two different marks can also be provided for pressure holding and pressure control. If the pulse time has expired, the corresponding mark is changed from control to hold (MH = 1) or vice versa. The time value for the corresponding pulse phase must also be loaded at the same time

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~ ¹⁶ ~ 28U279

is valid. Another criterion for the duration of the pulse is the number of pulse cycles that should be carried out. The pulsing is stopped when, for example, a counter for the number of pulse cycles has counted down to 0.

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Claims (11)

Hanover, on October 2nd, 1978 Wabco Westinghouse GmbH UP 26/78 Dr.K. Claims 1.j Procedure for regulating the brake pressure in anti-lock Vehicle braking systems, at which the speed of one or more vehicle wheels is scanned and an analog measured variable is obtained in the form of an alternating voltage, the period of which is the rotational speed of the corresponding vehicle wheel is inversely proportional, in which the analog measured variable is converted into a digital measured variable is made by counting the counting pulses falling within the duration of a period or a certain partial period, whose frequency is higher than the frequency of the alternating voltage, and in which the digital measured variable for generating controlled variables is evaluated in a control loop for controlling solenoid valves,
characterized by the following features: Dr.K./H. -2- D30Ö16 / G4 & 7 a) Counting in the duration between two successive edges in the same direction of falling counting pulses, b) Saving the respective payment result in a buffer, c) Retrieval of the counter result from the buffer memory by one in the control loop for generating the control signals provided programmable computer (microcomputer) at determinable times with the help of a Data loader, d) Processing of a main program in the computer to determine the control signals after loading the data word C _n * representing the counting result, with the following program steps being carried out one after the other: et ) generation of deceleration and acceleration control signals (-b and + b signals) from the data words Γ «, in that a differentiator reference value Γ_ is formed from the incoming data words for each control channel and compared with the new incoming data word, β ) Generation of slip control signals (λ), characterized in that for each control channel a reference variable Γ representing the vehicle speed from the own Data words Γ _{Ν is} formed and compared with the new incoming data word, \ j) Linking the nachod) and / 3) generated control signals (-b-, -rh-f A signals) to generate 030016/04 67 -3- Control signals (control signals) for the ■ solenoid valves / type V-that 'when .: ·.; "- vv; Signals (-b) of the ... '. RadbremsdrucrK · lowered, when there is a tendency to restart (+ b) signals indicating the wheel brake pressure ;, -.kqnstant "geäal'ten '^ and" after -abfall of the respective . Acceleration rule (+ b signal) Brake pressure -z ': '. Is controlled sv>'. ^r : ": - ·; ■ ■ '■ - 2. The method according to claim 1, characterized in that the storage in the buffer takes place in parallel. 3. The method according to claim 1, characterized in that two counters are used for counting the counting pulses, one of which is started at the beginning of the negative half-wave and the second at the beginning of the positive half-wave, and that the counting duration is in each case over a full period goes. 4. The method according to claim 1, characterized in that the data word T _{n can be called up} via a multiplexer which can be addressed by the computer, and that the data word reaches the computer via a serial data line. 5. The method according to claim 1, characterized in that the main computer program executes the following program steps 030016/0 U 8? -4- a) Blocking all interruption programs except for the interruption program for resetting the computer, b) jump to the beginning of the program, c) Loading of initial values for each control channel (e.g. differentiator time base, reference time base, "Cb '^ -el' ^ N ' ^ents P ^recnen ^ a given minimum speed) in dynamic registers, d) release of all interruption programs, e) Loading the data word T _n (period duration) into the register, f) Start of a main program loop, consisting of differentiator, slip control signal, logic and Reference size program, g) Calling up the differentiator program to determine the deceleration and acceleration signals (-b- and + b-control signals), h) Calling up the program for determining the slip control signals (λ control signals), i) Calling the logic program to logically link the control signals according to g) and h) and to generate them of control signals for the solenoid valves, j) Calling up the reference variable program to determine a common reference variable T _ for generating the slip frequency signal. 6. The method according to claim 5, characterized in that the differentiator program executes the following program steps: 030016/0 ^ 67 -5- a) Formation of the difference Δ between the reference variable T. and the respective data word £ "", b) Saving the sign and calculating the amount of the difference, c) Division of the reference variable Γ_ by a value m (iL / m, m any or m = 2 ⁿ with n = o, 1, 2,.,.) d) Query whether the amount of the difference is greater than the quotient TO e) Use of the data word T _n as a new reference value, if the query result is positive, f) Query whether the sign of the difference is positive, g) Setting a + b signal, if the sign is positive, h) restart differentiator time base, i) Setting the -b signal, if the sign is not positive, j) Restart the differentiator time base, k) If the amount of the difference is not greater than the reference value divided by m, query whether the time base has expired,
1) Resetting the + b and -b signals if the Differentiator time base already expired, m) restart of differentiator time base, n) if differentiator time base according to query k) has not expired and after each restart of the Time base jump to the program for calculating the slip control signals (or generally to the main program) . -6- 030D16 / 0AS7 7. The method according to claim 5, characterized in that the program for obtaining the slip control signal executes the following program steps: a) Query whether the reference time base has expired, b) if the reference time base has not expired, jump to g), c) when the reference time base has expired, the time base is reloaded, d) after reloading the reference time base, query, ^obr own <^ g ' e) ifr _eigen <6 _N , Z _{e ± gen} = F ^ _n + T _eigen / m is set, m = any or m = 2 ⁿ with n = o, 1, 2, ..., f) if! ". _ö according to query d) is not less than Γ"., GXySn JN ^will show ⁼ <"own" ^r _e igen ^{/ m} ^ forms, g) Query whether T _ref <T _n » h) if T "^ is not less than Z" _N , λ is reset and there is a return to the main program loop,
i) if T _f <T " _N , the difference Λ between T and T _f formed,
j) Formation of a permissible deviation by dividing the reference value F _f by m, m = any or m = 2 with n = o, 1, 2, ··., k) Query whether Δ is greater than the permissible deviation, 1) if Δ is greater than the permissible deviation, the λ control signal is set and there is a return jump in the main program, 030016/0467 -7- m) if Δ is not greater than the permissible deviation, the Λ control signal is reset and the main program returns. 8, method according to claim 5, characterized / that the logic program carries out the following program steps a) Query whether the + b control signal is set, b) if the + b control signal is set, a pulsed pressure build-up is prepared for a pulse time TV1, namely for control times TV, for which a brand MH is not is set as well as for hold times TV in which the mark MH is set, with a new numerical value for TV is loaded and the mark MH is inverted when the respective time TV has expired and the time TV1 has not yet expired, c) Switching on a pressure holding phase and resetting the mark MH and loading a time TV, d) Output of a valve control signal to maintain pressure, e) if the + b control signal is not set, query whether the -b control signal is set, f) if the -b control signal is set, activation of the venting phase and output of a valve control signal for venting, g) if the -b control signal is not set, query whether the Λ control signal is set, -8-03001Θ / 04Β7 h) if the Λ control signal is set, the venting phase is switched on and a valve control signal for venting is output, i) if the A control signal is not set, query whether the pulse time TV1 has expired, j) if TV1 has not expired, query whether the mark MH is set, k) if the mark MH is set, activation of the holding phase, 1) Output of a valve control signal to maintain pressure, m) if TV1 has expired or the mark MH is not set, activation of the control phase, n) resetting the valve control signals, o) Return to the main program. 9. The method according to claim 5, characterized in that the reference variable program carries out the following program steps: a) Loading the reference variable XT. (Reference period) of the second control channel as "C _1. , in the first strange Control channel and the reference variable T. (Reference period) of the first control channel as T in the second control channel, b) comparison whether r -9- 030016/0457 c) common reference value i_ = L. If L _s <L * " ref own ^toilet "" «- own '" foreign d) common reference value T _f = ZV. ,, if L _x . _Λ <L. ,
strange own e) Return to the main program / 10. The method according to any one of claims 5 to 9, characterized in that the computer program can be interrupted by a signal controlled by a free-running timer and triggers an interrupt program which carries out the following program steps: a) Decrementing the speed-dependent predetermined reference time base up to the numerical value zero for the interval adjustment of X. to the vehicle speed, b) Decrementing the predefinable differentiator time base up to the numerical value zero for the interval adaptation of T to the wheel speed to determine the differentiator signals, c) Generation of the times (TV1, TV) for the pulsed Pressure build-up, d) Return to the main program. 11. The method according to claim 1 o, characterized in that the interrupt program is superordinate to the main program and is called periodically recurring by an interrupt signal of a free running timer. 030016/0457 -ίο-