Method and apparatus for operating a brake system, brake system

Abstract

The present invention relates to a method for operating a brake system (1), the brake system (1) having at least one hydraulic brake circuit (6, 7) with at least one hydraulically operable wheel brake (8-11), and at least one pressure generator (12) for generating a hydraulic pressure in the brake circuit (6, 7), each wheel brake (8-11) being assigned at least one controllably operable inlet valve (EV8-EV11), and a hydraulic pressure value (p actual At least one pressure sensor (15) for detecting a pressure value (p) detected by the pressure sensor (15) is disposed between the inlet valves (EV8 to EV11) and the pressure generator (12), and the inlet valves (EV8 to EV11) are controlled by a hydraulic pressure control device (19). actual a pressure sensor (15) operated at a first clock frequency, and a hydraulic pressure control device (19) operated at a second clock frequency lower than the first clock frequency, characterized in that a correction current value (Δi) for controlling the operation of the inlet valves (EV8 to EV11) is determined at the first clock frequency, and the target current (i_EV_Target) is corrected by the correction current value (Δi).

Description

[Technical Field]

[0001] The present invention relates to a method for operating a brake system, the brake system having at least one hydraulic brake circuit with at least one hydraulically operable wheel brake and at least one pressure generator for generating hydraulic pressure in the brake circuit, the wheel brakes being assigned at least one controllably operable inlet valve, at least one pressure sensor for detecting a hydraulic pressure value being arranged between the inlet valve and the pressure generator, in particular between the pressure generator and a switching valve connecting the brake circuit to the pressure generator, the inlet valve being controlled by a hydraulic control device by setting a target current depending on the pressure value detected by the pressure sensor, the pressure sensor being operated at a first clock frequency and the hydraulic control device being operated at a second clock frequency lower than the first clock frequency.

[0002] The present invention further relates to a control device for operating a brake system, the brake system having at least one hydraulic brake circuit with at least one hydraulically operable wheel brake and at least one pressure generator for generating hydraulic pressure in the brake circuit, the wheel brakes being assigned at least one controllably operable inlet valve, at least one pressure sensor for detecting a hydraulic pressure value being arranged between the brake circuit and the pressure generator, the inlet valve being controlled by the hydraulic control device by setting a target current depending on the pressure value detected by the pressure sensor, the device comprising a control device configured to operate the pressure sensor at a first clock frequency and to control the inlet valve depending on the target current.

[0003] The invention further relates to a braking system as described above, comprising a control device as described above. [Background technology]

[0004] The method of the aforementioned type is already known in the prior art. In electronically controllable hydraulic braking systems, it is common to detect or monitor the hydraulic pressure generated in the brake system or in the brake circuit of the brake system using a pressure sensor. In this case, a pressure sensor is typically arranged between a pressure generator, such as a main brake cylinder, an electromechanical brake force booster, or a pump, and an inlet valve for a wheel brake, thereby detecting the pressure in the brake circuit. By controlling the inlet valve, the pressure provided in the brake circuit is supplied to the wheel brake for hydraulically operating the wheel brake. Therefore, knowledge of the hydraulic pressure present in the brake circuit is important for controlling the inlet valve, particularly in the case of wheel-individual pressure control, such as may occur in ABS control interventions. Individual control of all inlet valves is necessary so that the individual brake pressures can be precisely adjusted at all wheels of a vehicle. This is also because all inlet valves of a brake circuit must operate with the pressure provided by the pressure generator in the brake circuit. Disturbances in pressure generation or dynamic changes in the generated pressure must therefore be decoupled as best as possible from the individual inlet valve control. A "pre-pressure disturbance" occurring in front of the inlet valve in the brake circuit can be caused, for example, by the pressure generator itself or by the control of the inlet valve of an adjacent wheel brake or of one of the wheel brakes in the same brake circuit. To compensate for this type of pressure disturbance, hydraulic pressure changes must be detected as quickly as possible, leading to an adapted electrical control of the inlet valve. In particular, in the case of relatively new electrohydraulic systems with low hydraulic elasticity, the pressure in the brake circuit can change quickly even when the volume change is small. The latency of the pressure sensor can in this case lead to inconsistencies or inaccuracies in the control of the inlet valve. Summary of the Invention

[0005] The method according to the invention allows for optimal control of one or more inlet valves to achieve wheel-specific braking pressures even in brake systems with low hydraulic elasticity. The increased precision of the control of the at least one inlet valve according to the invention allows for more precise operation of wheel control functions, for example, wheel control functions of anti-lock systems. In particular, this allows for more reliable prevention of unintended wheel locking.

[0006] According to the present invention, this is achieved by determining a corrective current value for controlling the inlet valve at a first clock frequency and correcting the target current by the corrective current value. The first clock frequency preferably corresponds to the clock frequency at which a pressure sensor detecting one or more pressure values ​​in the brake circuit is operated. A current regulator element, operating at a second clock frequency, is connected upstream of each inlet valve. The brake pressure demand, which is the basis for controlling the valve, is detected by a hydraulic control device, which typically operates at a second clock frequency lower than the first clock frequency. This allows the system to react to pressure changes more slowly than would theoretically be possible with a current regulator element. The present embodiment of the method now ensures that the slower calculation path through the hydraulic control device is maintained, but at the same time, it is bypassed via a sort of bypass to react more quickly to pressure changes. For this purpose, at the first clock frequency, for example, a corrected current value for controlling the operation of the inlet valve is determined by a separate control device, which in particular also has a current regulating element, and the target current provided by the hydraulic control device is corrected by the corrected current value. The correction of the target current is thus performed at the first clock frequency, so that the target current can be corrected more quickly than would be possible with a hydraulic control device. This allows for a rapid adaptation of the target current and thus an optimized operation of the corresponding inlet valve.

[0007] Preferably, the corrected current value is determined as a function of a first average value of a predetermined number of pressure values ​​detected by the pressure sensor. By determining the corrected current value as a function of the average value of the pressure values ​​detected by the pressure sensor, it is achieved that the slower clock frequency of the hydraulic control device is replicated or imitated. Based on the slower clock frequency of the hydraulic control device, the average value of the more rapidly detected pressure sensor values ​​is obtained as a transfer value from the pressure sensor or a control device or circuit, which also has the first clock frequency. Since the corrected current value is now also determined as a function of the average value, equivalent results are obtained with respect to the corrected current value.

[0008] Preferably, a second average value of the pressure values ​​is determined from the pressure values ​​of the pressure sensor for delivery to a hydraulic control device having a second clock frequency, this second average value being the delivery value already mentioned above.

[0009] It is furthermore preferred to provide for the first average value to be formed from the same number of pressure values ​​as the second average value or from more pressure values ​​than the second average value, in particular from twice as many pressure values.

[0010] It is furthermore preferred to provide that the correction current value is determined as a function of the last detected pressure value, so that not only the first average value but now also the last detected pressure value is taken into account when determining the correction current value, resulting in an adaptation of the correction current value being carried out at the rate of the first clock frequency, thereby ensuring a particularly immediate correction of the correction current value.

[0011] In particular, a corrected current value is determined from the difference between the first average value and the last detected pressure value, which gives the deviation of the last detected pressure value from the first average value (and vice versa), which deviation is then used as the basis for correcting the target current.

[0012] Particularly preferably, the corrected current value is also determined as a function of the valve characteristic curve, in particular taking into account the slope of the valve characteristic curve.

[0013] A device according to the invention with the features of claim 8 is characterized in that the control device is specially designed to carry out the method according to the invention, which results in the advantages already mentioned.

[0014] A braking system according to the invention with the features of claim 9 is characterized by a control device according to the invention, which has the advantages already mentioned above. The control device preferably comprises a current regulating element.

[0015] The present invention will be described in detail below with reference to the drawings. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a simplified diagram of a braking system for an automobile; [Figure 2] FIG. 2 is a diagram showing signal paths for controlling the operation of a brake system. DETAILED DESCRIPTION OF THE INVENTION

[0017] 1 shows, in a simplified diagram, an advantageous brake system 1 for a motor vehicle, not shown in detail here. This exemplary brake system 1 comprises a reservoir 2 for providing brake fluid, a main brake cylinder 3, here configured as a tandem cylinder and operable by the driver of the motor vehicle by actuating a brake pedal 4, a brake pedal force simulator 5 connected downstream of the main brake cylinder 3, two brake circuits 6 and 7 connected downstream of the main brake cylinder 3 and each having two wheel brakes 8, 9 or 10, 11, and a pressure generator 12 having a displaceable pump piston 13 and an electric motor 14 for displacing the pump piston, the pressure generator 12 being connected to both brake circuits 6, 7 and to the hydraulic reservoir 2. In each brake circuit 6 or 7, an electrically controllably operable inlet valve EV8 to EV11 is further connected upstream of each wheel brake 8 to 11, and an electrically controllably operable outlet valve AV8 to AV11 is connected downstream of each wheel brake 8 to 11.

[0018] A pressure sensor 15 is also connected directly downstream of the pressure generator 12, which detects the hydraulic pressure between the pressure generator 12 and the inlet valves EV8 to EV11. Optionally, the brake circuits 6, 7 can be connected to the pressure generator by means of changeover valves V6, V7, whereby the pressure sensor 15 is arranged to detect or monitor the pressure for both brake circuits 6, 7 or the pressure before distribution to the brake circuits 6, 7.

[0019] The inlet valves EV8 to EV11 are operated electrically in response to a brake request set by the driver via the brake pedal 4. The inlet and outlet valves can also be operated automatically by a safety system, for example an ABS system. The pressure acting in the brake circuits 6, 7 can be generated, on the one hand, by the main brake cylinder 3 and, alternatively, on the other hand, by a pressure generator 12. In particular, by means of the pressure generator 12, the generation of the brake force or hydraulic pressure in the brake system 1 during semi-autonomous or fully autonomous driving is possible without actuation of the brake pedal 4.

[0020] 2 shows, in a simplified diagram, the signal path from the pressure sensor 15 to the inlet valve EV. A dashed line 16 divides the signal path into a first part and a second part. These parts of the operating control of the brake system 1 differ in terms of the clock frequency at which the signals are processed. In the first part, which is located substantially above and to the left of the dividing line 16, the signals are processed by hardware operating at a first clock frequency, which in this example operates at 1 ms raster / clock.

[0021] In particular, this hardware is provided by a control device 17, which is formed from one or more parts. In particular, the control device 17 has a current regulating element 18, which is located in the second part, i.e. which operates at a second clock frequency, and which determines a target current for operating the plurality of inlet valves EV8 to EV11, or a selected one of the plurality of inlet valves EV8 to EV11, depending on the pressure value detected by the pressure sensor 15.

[0022] Within the second section, in particular below and to the right of the dividing line 16, the signals are processed at a second clock frequency slower than the first clock frequency, in particular running at a 5 ms raster or clock. For this purpose, in particular, a hydraulic control device 19 is present, which determines a target current i_EV_Target depending on a braking force request p_Target detected by a pressure sensor device 20, which is used to control the operation of the inlet valve or valves EV8 to EV11 selected in order to realize the braking request. The pressure sensor device 20 includes, for example, a stroke sensor 21, as shown in FIG. 1, which detects the movement of the brake pedal 4. Alternatively or additionally, the braking force request may be generated by an autonomous driving system of the motor vehicle or by a driving safety device of the motor vehicle, for example an ABS device.

[0023] The signals in the first section must be passed to the hardware in the second section for further processing so that the selected inlet valves can be optimally controlled according to the actual pressures in the respective brake circuits 6, 7. Because the hydraulic control device 19 operates at a slower second clock frequency, e.g., 5 ms, a delay occurs when controlling the inlet valves to be controlled. This results in the signal inputs and outputs of the control device 17 being subject to at least one time delay p_MC relative to the pressure value detected by the pressure sensor 15. Additionally, the optional mean value filter 22 of the control device 17 may introduce a further time delay. In older systems, however, such a mean value filter is advantageous for suppressing unwanted disturbance signals.

[0024] The target current i_EV_Target is passed on to the (upper) hardware driver layer (HSW) or to the control device 17 with a faster first clock frequency and back. The target current is thus based on the pressure sensor signal p_MC, which due to the system has a value that is already outdated with respect to the current pressure value at the pressure sensor, here by 5 ms. The target current value is converted into an actuation voltage U by a current regulating element 18, for example with power electronics, which actuates the actuator coil 23 of the inlet valves EV8 to EV11 to be actuated, which acts to generate a magnetic field in the coil 23 that operates the inlet valves EV to be actuated.

[0025] Advantageously, the pressure values ​​detected by the pressure sensor 15 are collected, for example in a register 24, converted into an average value by the clock of the hydraulic control device 19 and passed on to the hydraulic control device 19, as indicated in Figure 2 by the arrow 25. The average pressure value p_MC is then taken into account by the hydraulic control device 19 to determine the target current as a function of the request p_Target, as previously described.

[0026] Advantageously, the "slower" pressure signal p_MC of the hydraulic control device 19 is now advantageously replicated on the side of the hardware driver layer HSW or the control device 17 and is hereinafter referred to as p_MC'. This pressure value p_MC' then corresponds to the average value last transmitted to the hydraulic control device. When a shift register is present, as shown in FIG. 2, this is possible with older pressure sensor generations. With pressure sensors of newer pressure sensor generations, the calculation of the pressure average value is simplified to a comparison of the actual pressure value p_actual with the average value p_MC': ΔpASW-error=p_Mc'-p_actual This difference represents the absolute value of the dynamic error ΔpASW-error in the pressure value that occurs on the ASW side or by the hydraulic pressure control device 19 based on the latency when calculating i_EV_Target.

[0027] As soon as the hydraulic control device 19 now transmits the target current i_EV_Target for controlling the selected inlet valve EV, an additional correction of the current error ΔpASW is carried out by the control device 17. Advantageously, the slope of the static valve characteristic line 26 is also taken into account, so that the current error is corrected by the slope of the valve characteristic line as a correction value Δi: Δi=ΔpASW-error*di / dp The quotient di / dp in this context indicates the slope of the static valve characteristic line, which represents the conversion of the pressure error into a current correction value. Since the hydraulic control device 19 calculates the target value only at a 5 ms raster (second clock frequency), corrections on the part of the control device 17 are also only necessary at a 5 ms raster or at the second clock frequency. However, it is advantageous to use the current pressure value determined at the first clock frequency each time the target current is dynamically corrected at the second clock frequency. The current regulator element 18 in this case does indeed operate at a 5 ms raster or clock, but obtains the current current correction value regardless of when the work cycle of the current regulator element 18 begins.

[0028] The DT1 pre-control 27, additionally shown in Figure 2, is optional and allows any remaining signal delay for the coil 23 and of the pressure sensor 15 itself to be corrected.

[0029] By this advantageous method it is achieved that, despite the different clock frequencies, the operating control, or the current controlling the operating of the respective inlet valve EV, is modified at the faster / shorter clock frequency.

[0030] A further advantage is that existing hardware can be maintained, and in particular, acceleration, particularly acceleration of the current regulator element 18, does not need to be implemented. The current value implemented by the current regulator element 18 is thereby dynamically corrected so that the valve adjustment current corresponds to the current pressure sensor value available at the first clock frequency. This minimizes dynamic pressure adjustment errors, and for example, the pressure buildup ramp of each wheel brake is optimized, particularly in ABS applications. Based on the ABS measurements performed, it was confirmed that when applying the method described here, continuous adjustment of the brake pressure is implemented even with high front pressure gradients, particularly without significant crosstalk that could result in front pressure disturbances. [Explanation of symbols]

[0031] 1. Brake system 2 reservoirs 3 Main brake cylinder 4. Brake pedal 5. Brake pedal force simulator 6,7 Brake circuit 8,9,10,11 Wheel brakes 12 Pressure generator 13 Pump piston 14 Electric motor 15 Pressure Sensor 16 Dividing Line 17 Control device 18 Current Regulating Element 19 Hydraulic pressure control device 20 Pressure sensor device 21 Stroke sensor 22 Mean Filter 23 Actuator coil 24 registers 25 Arrow 26 Static valve characteristic curve 27 DT1 front control section AV8~AV11 outlet valve EV8~EV11 Inlet valve V6, V7 switching valve

Claims

1. A method of operating a brake system (1), comprising: The brake system (1) at least one hydraulic brake circuit (6, 7) having at least one hydraulically operable wheel brake (8-11); at least one pressure generating device (12) for generating hydraulic pressure in said brake circuits (6, 7); and Each wheel brake (8-11) is assigned at least one inlet valve (EV8-EV11) that can be operated controllably; Hydraulic pressure value (p ａｃｔｕａｌ At least one pressure sensor (15) for detecting a pressure difference between the inlet valves (EV8 to EV11) and the pressure generator (12) is disposed between the inlet valves (EV8 to EV11) and the pressure generator (12), The inlet valves (EV8 to EV11) are controlled by a hydraulic pressure control device (19) based on the pressure value (p ａｃｔｕａｌ ) and the operation is controlled by setting a target current (i_EV_Target) according to the The pressure sensor (15) is operated at a first clock frequency; The hydraulic control device (19) is operated at a second clock frequency lower than the first clock frequency. In the method, determining a corrected current value (Δi) for the operation control of the inlet valves (EV8 to EV11) at the first clock frequency; The target current (i_EV_Target) is corrected by the corrected current value (Δi). A method for operating a brake system (1), characterized in that:

2. The corrected current value (Δi) is calculated based on a predetermined number of pressure values ​​(p ａｃｔｕａｌ 2. The method according to claim 1, wherein the first average value (pMC') of the total number of MC's is determined.

3. The pressure value (p ａｃｔｕａｌ ) for delivery to the hydraulic control device (19) having the second clock frequency, ａｃｔｕａｌ 3. The method according to claim 1, further comprising determining a second mean value (pMC) of the measured values ​​of the chromatic aberrations (a, b, c, d, d, e, d, s, s).

4. The first average value (pMC') is divided into the same number of pressure values ​​(p ａｃｔｕａｌ ) or from the second average value (pMC) more pressure values ​​(p ａｃｔｕａｌ ), especially the double number of pressure values ​​(p ａｃｔｕａｌ 4. The method according to claim 1, wherein the polymer is formed from a polymer of the formula (I).

5. The corrected current value (Δi) is calculated by multiplying the last detected pressure value (p ａｃｔｕａｌ 5. The method according to claim 1, wherein the determination is made depending on:

6. The corrected current value (Δi) is calculated by multiplying the first average value (pMC′) and the last detected pressure value (p ａｃｔｕａｌ 6. The method according to claim 1, wherein the difference between the

7. 7. The method according to claim 1, wherein the corrective current values ​​(.DELTA.i) are determined as a function of a valve characteristic line (26).

8. A device for operating a brake system (1), comprising: The brake system (1) at least one hydraulic brake circuit (6, 7) having at least one hydraulically operable wheel brake (8-11); at least one pressure generating device (12) for generating hydraulic pressure in said brake circuits (6, 7); and Each wheel brake (8-11) is assigned at least one inlet valve (EV8-EV11) that can be operated controllably; Hydraulic pressure value (p ａｃｔｕａｌ At least one pressure sensor (15) for detecting a pressure difference between the inlet valves (EV8 to EV11) and the pressure generator (12) is disposed between the inlet valves (EV8 to EV11) and the pressure generator (12), The inlet valves (EV8 to EV11) are controlled by a hydraulic pressure control device (19) based on the pressure value (p ａｃｔｕａｌ ) and the operation is controlled by setting a target current (i_EV_Target) according to the The pressure sensor (15) is operated at a first clock frequency; The hydraulic control device (19) is operated at a second clock frequency lower than the first clock frequency. In the apparatus, a control device (17) specially adapted to carry out the method according to any one of claims 1 to 7, in intended use; A device for operating a brake system (1), characterized in that

9. A braking system (1), comprising: at least one hydraulic brake circuit (6, 7) having at least one hydraulically operable wheel brake (8-11); at least one pressure generating device (12) for generating hydraulic pressure in said brake circuits (6, 7); Equipped with Each wheel brake (8-11) is assigned at least one inlet valve (EV8-EV11) that can be operated controllably; Hydraulic pressure value (p ａｃｔｕａｌ At least one pressure sensor (15) for detecting a pressure difference between the inlet valves (EV8 to EV11) and the pressure generator (12) is disposed between the inlet valves (EV8 to EV11) and the pressure generator (12), The inlet valves (EV8 to EV11) are controlled by a hydraulic pressure control device (19) based on the pressure value (p ａｃｔｕａｌ ) and the operation is controlled by setting a target current (i_EV_Target) according to the The pressure sensor (15) is operated at a first clock frequency; The hydraulic control device (19) is operated at a second clock frequency lower than the first clock frequency. In a brake system (1), 9. The device of claim 8, A brake system (1) characterized by:

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