DE2836778A1 - ANTI-BLOCKING CONTROL SYSTEM - Google Patents

Description

28367'7ft

The invention relates to an anti-lock control system from at least one transducer to obtain a speed corresponding to the vehicle wheel Signal, an evaluation circuit to which this signal is fed and which is dependent on the wheel movement behavior Brake pressure control signals generated and a brake pressure control device, to which the brake pressure control signals for varying the brake pressure are fed, wherein in the evaluation circuit with the help of the wheel speed signal approximates the vehicle speed curve Reference signal is generated, with which the signal corresponding to the wheel speed is compared, wherein a Brake pressure control signal is generated when the wheel speed signal is in a predetermined relationship to the reference signal and where the predetermined negative Slope of the reference signal to approximate the actual negative slope of the vehicle speed profile is changeable, at the end of a control cycle the reference variable in a predetermined ratio to the current one Wheel speed is brought.

Anti-lock braking systems that reduce the negative slope of the Make the reference variable dependent on the road condition and thus on the deceleration of the vehicle e.g. from DE-OS 22 09 955 and DE-OS 23 43 743 known. In both cases it is provided that the slope during to change a control cycle. In the solution of DE-OS 23 43 743 only large negative slopes are used and thus no approximation to the vehicle speed curve is sought.

Both known solutions require a brake or vehicle deceleration sensor and one to solve the problem associated evaluation electronics.

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The invention is based on the task of adapting the course of the reference signal to the course of the actual To achieve vehicle speed without the need for additional expensive sensors and evaluation means are needed.

Based on the anti-lock control system described above this object is achieved according to the invention in that evaluation means are provided, each of which the deviation of the wheel speed signal at the end of the control cycle determine of the reference signal according to size and / or direction and that switching means are provided, which, as a result of this measurement, changes the negative slope of the reference value in the sense of an adjustment to the Cause vehicle speed curve.

In the embodiment according to the invention, there is a wheel speed signal and a reference signal anyway are formed, only necessary to determine the deviation of the sizes from one another at a certain point in time. Only a slight additional electronics effort is necessary for this.

It was mentioned above that the wheel speed signal in a predetermined ratio to initiate the pressure reduction must be in relation to the reference signal and that at the end of the wheel cycle the reference signal has a predetermined ratio is brought to the wheel speed signal. For a better understanding it should be mentioned that in general at the end of the Wheel cycle in each case the reference signal is made equal to the wheel speed signal and that in this case the Ratio of the two variables in which the pressure reduction is initiated, determined by a speed difference Av Size or a certain slip S is given.

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Above was the deviation of the wheel speed signal from the Peststellring spoken of the reference signal according to sign and / or amount. With plague of amount and sign, an analog change in the slope of the reference signal can be made, including a search the usable level should fall in the presence of several discrete predetermined slope levels. is the formation of the reference size is designed so that with (again) increasing bath speed from equality of sizes If the reference signal follows the wheel speed signal without delay, the reference signal is exceeded the wheel speed signal is not in front and thus is only determine a deviation according to the amount. Finally, one can only determine the sign of the deviation and due to the determination of the sign, a gradual approximation of the slope to the slope of the Carry out the vehicle speed curve in specified levels. It has been found that it is favorable to allow only those gradients for the reference variable that correspond to a vehicle deceleration range of 0.1 g - 0.8 g correspond. Does the anti-lock controller have a logic in which, due to a high wheel acceleration (+ ap signal) a pressure increase is allowed when the wheel recovers, while the pressure is kept constant with lower acceleration it is useful to limit the negative slope of the reference signal downwards, e.g. do not allow negative slope values smaller than 0.3 g.

The drawing shows exemplary embodiments of the invention explained. Show it

Pig. 1 - a block diagram of an anti-lock control system designed according to the invention

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Fig. 2 - a detailed embodiment

of the block of FIG. 1, which forms the reference variable "

Fig. 3

and FIG. 4 - timing diagrams for explaining FIG

Mode of operation of the circuit of FIG. 2

Fig. 5

and FIG. 6 - two other embodiments for

this block.

In Fig. 1 there is only one transducer for the sake of simplicity 1 for determining the speed of a vehicle wheel and a brake pressure control element for a vehicle wheel provided, consisting of one inlet and outlet valve 2 and 2 connected to the brake line 3. Further transducers and brake pressure control elements can be provided.

The signals from the transducer 1 are converted in the converter 4, for example, into a direct voltage proportional to the wheel speed. The block 5 serves to form the reference signal which is compared in the comparator 6 with the wheel speed signal. The speed difference signal at the output of the comparator 6 is fed to the threshold value stage 6a. Their output signal is fed to the logic together with the wheel deceleration signal -a and zv / ei wheel acceleration signals (+ a .. and + a ^) formed in block 7, in which control signals for valves 2 and 3 are formed in a known manner. The output signal of the comparator 6 is fed back to the block via line 9. Likewise, block 5 receives the -a and + a ₁ signals.

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In Pig. 2 the block 5 is drawn out enlarged j it is assumed here a version of the formation of reference values in analog technology. The direct voltage signal coming from block 4 is fed to a memory in the form of a capacitor 10 here. While, because of the one-way valve 11, the state of charge of the memory 10 adapts to this signal without delay when the DC voltage signal increases, the capacitor 10 can only discharge at a predetermined rate determined by the resistor 13 when the DC voltage decreases rapidly. As long as the control is not yet running, this resistance is very small, so that in this case the state of charge can follow the wheel speed signal even with decreasing speed. When a wheel deceleration of a certain magnitude (- a) occurs, the resistance is brought to a predetermined value 13 via the element 14, which, for example, allows a discharge corresponding to a deceleration of -0.3 g. The signal that can be picked up at the capacitor 10 can then only follow the wheel speed signal with a predetermined negative slope.

The speed signal that can be tapped off at the capacitor 10 is fed to the comparator 6. The resistor 13 is designed to be electronically controllable and is controlled by the block 14 controlled in size. The output signal Ua of the comparator 6 is fed to the block 14. After completion of each control cycle, e.g. when the wheel acceleration signal (+ a ..) disappears, the then existing Among other things, the value is stored in block 14, which is thus for the the following control cycle determines the negative slope of the reference variable. The resistor 13 and the control block 14 can be designed so that only negative slopes are possible which correspond to a range between e.g. -0.1 g and -0.8 g. The mode of operation of the circuit of FIG. 2

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β- ^{/ 6}

is explained with reference to FIGS. 3 and 4. In Fig. 3 is assumes that the braking is based on a relatively high coefficient of friction takes place, i.e. with a large vehicle deceleration of e.g. just - 0.7 g.

In Fig. 3 with V- the vehicle speed, with V-, the reference speed shown in dashed lines and the wheel speed plotted against time with V-n.

At t ₁ the mentioned delay signal (- a) occurs, which makes a time constant of the discharge effective which corresponds to a delay of - 0.3 g. After the end of the control cycle at tg (e.g. end of + a.), The reference variable is once adjusted to the wheel speed signal by briefly reducing the resistance 13, but at the same time the difference Z \ v between the two variables is stored in block 14. The greater the difference Δ.ν between the variables, the more the discharge time constant of the capacitor and thus the resistor 13 must be reduced. It is assumed here that the correct slope, which corresponds to a delay of 0.7 g, is set after the first cycle.

In Fig. 4, a control process on a roadway is assumed with a coefficient of friction that corresponds to a vehicle deceleration of only -0.1 g. At t 'a slope corresponding to -0.3 g is switched on again. From t, ¹ , since this gradient is too great for the road conditions, the wheel speed is again the reference variable. At the end of the cycle (tp ¹ ), since not even a small Ua is measured, an end value of the slope is determined.

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speaking 0.1 g "switched. If necessary, must be here at the next end of the cycle a further adjustment occurs a value e.g. corresponding to 0.2 g.

The embodiment of the Pig. 2 can be modified in such a way that one uses the reference variable at t- ^ of FIG does not follow the wheel speed. For this purpose, only the link 11 would have to be designed as a lockable gate. In addition, the member 14 would then have to be able to recognize the deviation Δ ν according to size and sign. In this case it could the reduction of the slope takes place according to the measured deviation.

A comparable result would be obtained if one took away the reference value according to the point in time t -> * of FIG. 4, but when the wheel speed becomes equal to the reference variable, stores the reference variable value and this value with the wheel speed value compares at the end of the cycle. Here, too, the deviation would have to be measured according to size and sign and could then adjust accordingly.

In the exemplary embodiment in FIG. 5, only block 5 * 'in FIG. 1 is again drawn out. Here, the capacitor 21 is connected via a step switch 22 to discharge resistors 23, which are of different sizes. It is checked with the aid of the block 24 whether the deviation of the wheel speed from the reference signal is positive or negative. It is assumed here that the reference variable can in any case only adjust to the wheel speed at the end of the control cycle, ie ^{it is impossible to keep the reference variable between tJ and tp 1 as a} result of blocking (not shown) in accordance with FIG. 4. If there is a positive deviation + Δ at the end of the cycle. ^v or vv. U λ ν i ^m block 24

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determined, the switch is in each case from its starting position (corresponding to - 0.3 g) in the first cycle or its random position in one of the subsequent cycles in Adjusted in the direction of an increase in the incline by one step (e.g. from the one corresponding to the incline - 0.3 g Position in the position corresponding to the incline - 0.4 g) Accordingly, there is a negative deviation in the plague position (- At) a changeover by one level in the direction a smaller incline (e.g. from a position corresponding to - 0.3 g to a position corresponding to 0.2 g). For this purpose, the step switch 22 is switched from step 24 in one direction or the other. The limitation to a range (e.g. - 0.1 g to 0.8 g) is possible here in a simple manner by adding larger and smaller negative slopes are not provided.

Fig. 6 shows an embodiment of the block 5 of Fig. 1, which requires a digital representation of the speeds. The digital wheel speed value is after every wheel speed measurement (as long as the control has not yet taken place) is written into register 31. From the beginning the control is the control part 32 via line 33 (- a signal) put into operation, which now stores wheel speed signals in register 31 via gate 35 blocks and the value present in the register at predetermined time intervals "supplied to the summing element 34, the then causes the register value to be reduced by a predetermined value. In the course of the first control cycle, let this value is chosen so that there is a mean negative value for the value of register 31 to be used as a reference variable Incline accordingly - 0.3 g results. At the end of the control cycle, the wheel speed value then available is ins Register 31 saved and also by plague position the sign and amount of Av determined in block 36, The mean negative slope with which the register value is to be changed in the subsequent cycle, i.e. in which The amount of the register value at the specified time intervals must be reduced by 30010/0220

Claims (4)

R.> · .3θ August 11, 1978 PT-Ka / Ba Attachment to Patent and utility model Aid registration ROBERT BOSCH GmbH, D-7000 Stuttgart 1 Anti-lock control system Patent claims: Anti-lock control system consisting of at least one transducer for obtaining one of the speed of a vehicle wheel corresponding signal, an evaluation circuit to which this signal is supplied and the brake pressure control signals are generated as a function of the wheel movement behavior and a brake pressure control device, to which the brake pressure control signals for varying the brake pressure are fed, wherein in the evaluation circuit with the aid of the wheel speed signal a reference signal approximating the vehicle speed profile is generated, with which the signal corresponding to the wheel speed is compared, wherein a brake pressure control signal is generated when the wheel speed signal is in a predetermined ratio to the reference signal and where the given negative slope of the loading 030010/0220 '/ 2 ORIGINAL INSPECTED • A ^{/ 2} Zugssignal to approximate the actual negative slope of the vehicle speed curve is changeable, at the end of a control cycle the reference variable is brought into a predetermined ratio to the current wheel speed, characterized in that evaluation means are provided which each time the deviation of the wheel speed signal from the reference signal at the end of the control cycle determine according to size and / or direction and that switching means are provided which, on the basis of this measurement, cause the change in the negative slope of the reference variable in the sense of an adaptation to the vehicle speed profile. 2. Anti-lock control system according to claim 1, characterized in that when only the sign is detected the deviation, the adjustment takes place in specified steps. 3. Anti-lock control system according to claim 1 or 2, characterized in that changes in the slope are only provided in a range that corresponds to a vehicle deceleration range of 0.1 g to 0.8 g is equivalent to. 4. Anti-lock control system according to one of claims to 3, in which additionally at high wheel acceleration a control signal is generated which allows a pressure increase, characterized in that switching means are provided that, when such a control signal occurs, slopes for the reference variable, that are smaller than a specified value. 030010/0220