Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1992-03-25
1992-10-13
Butler, Douglas C.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
188181R, 303 15, 303DIG4, B60T 832, B60T 1368
Patent
active
051544946
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method for converting a signal P* which corresponds, particularly, to a desired brake pressure into a control signal .DELTA.T which and actuates a brake pressure control device for a certain period of time, wherein a measuring device measures the generated pressure and supplies a corresponding signal P.
It is known, for example, to supply a brake pressure to the wheel brake cylinder of a vehicle which corresponds to a signal characterizing a desired brake pressure. For this purpose, the brake pressure supplied is measured and the measured signal is compared to the desired value. A possibly occurring deviation causes a valve device to be actuated which increases or decreases the brake pressure until the desired brake pressure is reached.
SUMMARY OF THE INVENTION
According to the invention, the length of the control signal T (K+1) in the control interval (K+1) is determined by the difference between the signal P*(K+1) representing the desired pressure and the signal P(K) representing the pressure supplied in the preceding control interval (K), as well as a gain factor b.sup.+/- and a response to TO.sup.+/-. Estimated values for the gain factor b.sup.+/- and the response time TO.sup.+/- of the brake pressure control unit are determined from the preceding pressure differences P(j)-P(j-1) and P(j-1)-P(j-2), as well as the actuating times .DELTA.T(j) and .DELTA.T(j-1), where j is the identification index.
As compared to the state of the art, it is an advantage of the invention that the desired pressure can be supplied faster and more accurately. The invention can be used with ABS or ABR, for example. It is a further advantage that the method permits drawing conclusions regarding the condition of the brake system.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram for carrying out the process,
FIG. 2 shows plots of the brake pressure, valve positions, and control signals versus time;
FIG. 3 is a plot of the pressure bounce against the actuating values.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In FIG. 1 a signal P* which corresponds to the desired pressure is supplied at a terminal 1 and at the overlapping point 2 a counter signal is supplied corresponding to the pressure in the wheel brake cylinder. The difference signal is supplied to a control amplifier 3 using this given signal to generate a control signal .DELTA.T which corresponds to the time required at the instantaneously prevailing conditions in order to increase or decrease the pressure to match the desired pressure. The signal at terminal 1 can be a digital signal and the difference can be digitally formed and further processed. The preceding sign of the signal .DELTA.T determines whether pressure is to be increased or decreased. No signal means maintaining the condition. The signal .DELTA.T is supplied to a valve control logic 4 which opens an inlet valve or an outlet valve in brake pressure control device 5 corresponding to the preceding sign of signal T and thus connects a supply pressure PO or a low pressure Pa to a wheel brake cylinder 6. Normally, the valve control logic 4 keeps the inlet valve EV from PO and the outlet valve AV to Pa closed and opens one when the signal .+-..DELTA.T occurs. A sensor 7 measures the brake pressure. The measured signal P is supplied to the overlapping point 2, a memory 8 and an overlapping point 9.
Measuring, storing and evaluating is carried out in small time intervals T between time points k,(k+1), . . . The brake pressure sensed in the respectively preceding interval is stored in the memory 8. Assuming that the sensor 7 senses the brake pressure P(K+1) in the (K+1)nth interval then the brake pressure P(K) is stored in the memory. The magnitude of the pressure bounce .DELTA.p(K+1) is formed at the output of the overlapping site 9.
FIG. 2 shows the pressure curve P and the actuating signals for the valve as well as the appertaining curve of the signal .DELTA.T. The pressure bounce .DELTA.P(K+1) and the control signals .DELTA.T are al
REFERENCES:
patent: 4344137 (1982-08-01), Skarvada
patent: 4938544 (1990-07-01), Braschel et al.
patent: 5016179 (1991-05-01), Utzt
Kost Friedrich
van Zanten Anton
Weiss Karl-Josef
Butler Douglas C.
Robert & Bosch GmbH
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