Method for operating a brake system of a motor vehicle and control and/or regulating device
阅读说明:本技术 用于运行机动车的制动设备的方法以及控制和/或调节装置 (Method for operating a brake system of a motor vehicle and control and/or regulating device ) 是由 E.曼赫茨 P.施马伊泽勒 于 2018-06-06 设计创作,主要内容包括:本发明涉及一种用于运行机动车的制动设备的方法,在该方法中根据目标-减速度(a<Sub>soll</Sub>)来运行第一液压系统。能够激活第二机电制动系统,以用于使所述机动车减速。在此提出,所述第二制动系统的制动力(F<Sub>ist</Sub>)取决于实际-减速度(a<Sub>ist</Sub>)。(The invention relates to a method for operating a brake system of a motor vehicle, in which method a target deceleration (a) is used as a function of a target deceleration soll ) To operate the first hydraulic system. A second electromechanical braking system can be activated for decelerating the motor vehicle. It is proposed that the braking force (F) of the second brake system ist ) Depending on the actual deceleration (a) ist )。)
1. Method for operating a brake system (10) of a motor vehicle, wherein a target deceleration (a) is determinedsoll) To operate a first hydraulic brake system (26) and wherein activation is possibleA second electromechanical braking system (28) for decelerating the motor vehicle, characterized in that the actual deceleration (a) is taken into accountist) Generating a braking force (F) provided by the second brake system (28)ist)。
2. Method according to claim 1, characterized in that the second brake system (28) is activated automatically if it is determined that the first brake system (26) is malfunctioning and there is a driver's braking demand.
3. Method according to any one of the preceding claims, characterized in that the second brake system (28) is activated when the driver actuates the respective actuating element (16).
4. Method according to any one of the preceding claims, characterized in that the braking force (F) provided by the second brake system (28) is regulated by means of at least one first regulating circuit (52)ist) The input variable of the first control loop (52) is the actual deceleration (a)ist) In particular the actual wheel deceleration or equivalent.
5. Method according to claim 4, characterized in that the braking force (F) provided by the second brake system (28) is regulated by at least one second regulating circuit (54)ist) The input variable of the second control circuit (54) is the actual braking force (F)ist) Or an equivalent variable, wherein the first control loop (52) and the second control loop (54) together form a cascade structure.
6. The method according to claim 5, characterized in that the equivalent variable is an actual motor torque of a control motor (40) of a brake actuator, an actual motor current of a control motor (40) of the brake actuator or an actual displacement path of a control element of the brake actuator.
7. Method according to any of claims 5 or 6, characterized in that the actual braking force (F)ist) Or the equivalent variable is detected by means of a detection device (48) or is estimated by means of an estimation method.
8. Method according to any of claims 5 to 7, characterized in that a pre-control mechanism (68) is provided, which pre-control mechanism (68) is controlled by the target deceleration (a)soll) Generating said actual braking force (F)ist) Or an equivalent parameter.
9. Method according to one of the preceding claims, characterized in that an air gap between an operating element, in particular a spindle nut, and a counterpart, in particular a brake piston, is reduced immediately after activation of the second brake system (28).
10. Control and regulation device (20) for a brake system (10) of a motor vehicle, having a processor (22) and a memory (24), characterized in that the control and regulation device (20) is designed to carry out a method according to one of the preceding claims.
Technical Field
The invention relates to a method for operating a brake system of a motor vehicle and to a control and/or regulating device for a brake system of a motor vehicle according to the preambles of the respective claims.
Background
DE 102014203322 a1 describes a method for generating an emergency deceleration of a moving vehicle. In this case, a first hydraulic brake system for decelerating the front wheels and a second electromechanical brake system acting on the rear wheels of the vehicle are provided as electromechanical parking brakes. Furthermore, it is known from the market to activate an electromechanical parking brake provided as a second brake system for decelerating the motor vehicle if a functional failure (fehlfank) is detected in the first hydraulic brake system. In this case, the braking force (which here refers to, for example, the following clamping forces with which the brake disk is clamped between two brake shoes (Bremsbaken)) is controlled by: for example, the motor current of a control motor (Stellmotor) of a brake actuator of the second brake system is used as the control variable. Such a motor current is detected, for example, with a corresponding tolerance, and the activation state is maintained until a target setpoint value is reached.
Disclosure of Invention
The object of the present invention is to provide a method with which a reliable deceleration of a motor vehicle, in particular independent of a number of external influencing factors, can be achieved even in the event of a failure of the first hydraulic brake system.
This object is achieved by a method having the features of claim 1 and by a control and/or regulating device having the features of the claims that follow. Advantageous developments are specified in the dependent claims. Furthermore, the features that are important for the invention can be found in the following description and the drawings. The features can be essential to the invention both individually and in various combinations without this being explicitly indicated again.
In the method according to the invention, the first hydraulic brake system is operated as a function of the target deceleration. The second electromechanical brake system can be activated for decelerating the motor vehicle, i.e. for decelerating the motor vehicle when the motor vehicle is in motion. According to the invention, it is proposed that the braking force provided by the second brake system is dependent on the actual deceleration, i.e. the braking force is generated taking into account the actual deceleration.
Thus, according to the invention, the deceleration of the vehicle can also be adjusted accurately and reproducibly when using the second electromechanical brake system. Thus, for the use of electromechanical brake systems, further possibilities arise, for example, also for dynamic brake manoeuvres. This makes it possible to expand and more freely design the backup level of the first brake system and thus to increase the overall availability of the brake system.
The difficulty of adapting the braking characteristics to changing frame and environmental conditions is also reduced. For example, for a vehicle, the brake disc friction coefficient of the brake disc of the electromechanical braking system may change on the one hand and on the other hand. Since the braking force of the second brake system depends on the actual deceleration in the present invention, the desired vehicle deceleration, i.e., the target vehicle deceleration, can always be set as long as it is physically possible. The essence of the invention is therefore to set the braking force of the second brake system in such a way that a desired deceleration (target deceleration) of the motor vehicle is set.
It goes without saying that the invention can be used not only in brake systems for which the hydraulic brake system and the electromechanical brake system are completely independent of one another in such a way that they each comprise separate components. However, this is usually achieved by: for example, the electric motor of the electromechanical brake system and other additionally required components, such as, for example, the spindle-nut system, are integrated directly into the brake caliper of the hydraulic brake system, which is usually implemented on the rear axle of the motor vehicle. This means that the first hydraulic brake system and the second electromechanical brake system use the same brake caliper and brake piston and the same brake disc. In this case, the brake piston can be moved either hydraulically or else electromechanically, for example by means of a spindle nut.
Furthermore, it is to be noted here that the dependence of the braking force of the brake system on the actual deceleration can be achieved both in additional electromechanical brake systems and also in brake systems of each type, i.e. in simple hydraulic brake systems. This represents in principle a separate claimed invention. The precondition is merely that a possible solution is provided with which the deceleration desired by the driver of the motor vehicle can be quantified ("driver braking request"). In the simplest case, this can be achieved by a sensor on the brake pedal.
A first refinement of the method according to the invention is characterized in that the second brake system is automatically activated if a malfunction of the first brake system is determined and a braking request by the driver is present. This significantly increases the operational reliability of the motor vehicle and reduces the burden on the driver of the motor vehicle.
It is also possible to activate the second brake system if the driver actuates the corresponding actuating element. If the second electromechanical brake system is an Automatic Parking Brake (APB), such an actuating element is present anyway, since the driver can manually actuate the parking brake with the actuating element in the stationary state of the motor vehicle. However, there may also be situations in which the driver or another person in the motor vehicle wants to decelerate the motor vehicle by means of the second brake system when the motor vehicle is not at a standstill, for example when it is determined that the first brake system is malfunctioning or when the driver is absent. In this case, the person can manually activate the second brake system and ensure a reliable deceleration of the vehicle by adjusting the braking force of the second brake system such that a predefined vehicle deceleration is achieved.
It is particularly advantageous if the braking force of the second brake system is regulated by at least one first control loop, the input variable of which is the actual deceleration, in particular the actual wheel deceleration, or an equivalent variable. This can be easily implemented and allows the actual deceleration to be adjusted directly to the target deceleration. If only the first control loop is provided, it should be designed relatively slowly in order to compensate for the relatively large inertia of the control path (Regelstrecke) formed by the motor vehicle.
It is also particularly advantageous if the braking force of the second brake system is regulated by at least one second control loop, the input variable of which is the actual braking force or an equivalent variable, wherein the first control loop and the second control loop together form a cascade structure. Thus, there is an "inner" control loop, i.e. the second control loop, and an outer control loop, i.e. the first control loop. The inner control loop attempts to set the setpoint value of the outer control loop. The pilot deceleration is returned by the external control circuit and an excessively small deceleration is detected and accordingly a predetermined value for the force (target braking force) or an equivalent variable of the internal control circuit is adapted. A relatively rapid adjustment overall can be achieved by such a cascade structure, so that the actual deceleration reaches the target deceleration very quickly.
In a further development of this type, it is proposed that the equivalent variable is the actual motor torque of the actuating motor of the brake actuator, the actual motor current of the actuating motor of the brake actuator or the actual displacement path of the actuating element of the brake actuator. The actual motor current is a variable which is easy to detect and in many cases is present anyway. The actual motor torque and the actual displacement travel can be estimated in a simple manner from the actual current and the actual voltage. The regulation according to the invention can be carried out precisely with the parameters mentioned.
In this case, it is possible for the actual braking force or the equivalent variable to be detected by means of a detection device or to be estimated by means of an estimation method. Particularly precise control is possible if the parameter is detected by means of a detection device. If the parameters are estimated by an estimation method, for example, by the observation method (Beobachterverfahren), the detection device can be omitted, thereby saving costs.
In particular, it is advantageous to provide a pilot control unit which generates a pilot control value of the actual braking force or of an equivalent variable from the target deceleration. If a second control loop is provided, the generated pilot control value can be initially supplied as a return-related variable to the second control loop. Thereby, the process of adjusting the actual-deceleration to the target-deceleration is accelerated again.
In the same direction, a development is produced in which the air gap between the actuating element, in particular the spindle nut, and the counterpart, in particular the brake piston, is reduced immediately after activation of the second brake system.
The invention also comprises a control and regulation device for a brake system of a motor vehicle, having a processor and a memory, wherein the control and regulation device is designed to carry out a method according to one of the preceding claims.
Drawings
Embodiments of the present invention are explained below with reference to the drawings. Shown in the drawings are:
fig. 1 shows a schematic block diagram of a brake system of a motor vehicle;
fig. 2 shows a functional diagram of a first embodiment of an adjustment scheme of the brake system of fig. 1;
FIG. 3 shows a flow chart of the conditioning scheme of FIG. 2;
fig. 4 shows a diagram in which the braking force and the deceleration of the motor vehicle are plotted over time in two different load states of the motor vehicle;
FIG. 5 shows a functional diagram similar to FIG. 2 of a second embodiment; and is
Fig. 6 shows a functional diagram of a third embodiment similar to fig. 2.
Detailed Description
Hereinafter, such elements, regions and functional blocks having equivalent functions to those of the aforementioned elements, regions and functional blocks have the same reference numerals. It is not explained in detail again.
The brake system of a motor vehicle is generally designated by reference numeral 10 in fig. 1. The motor vehicle itself is not shown in fig. 1. However, it can be any motor vehicle, i.e., for example, a car, a motorcycle or a truck.
The brake system comprises firstly a
The brake system 10 has two brake systems which are substantially independent of one another. The first
The second
Thus, in the presently described embodiment, the hydraulic brake system and the electromechanical brake system are completely independent of each other in such a way that they each comprise separate components. However, in an embodiment that is not shown, this is achieved by: the adjusting motor of the electromechanical brake system acts on the same brake as the adjusting motor of the hydraulic brake system. This is also known as a "motor on tong" system. In such systems, therefore, the same brake calipers, brake discs, brake pistons, etc. are used for the electromechanical brake system and for the hydraulic brake system.
The second
The brake system 10 also comprises a
The brake apparatus 10 generally operates as follows: when the driver wants to decelerate a moving vehicle, he normally presses on the
In a not shown embodiment, the first hydraulic brake system is not operated "automatically" in a regulated manner. Instead, the "adjustment" is undertaken by the driver of the motor vehicle who, by adapting the force with which he presses the brake pedal, adapts the actual deceleration to the target deceleration desired by him.
If, however, the control and regulation device 20 determines that the
In the present practice, the
In order to achieve a real deceleration a when activating the second
The first
Through the use of a pre-control mechanism, the dynamics of the overall system can be improved. Such a pre-control mechanism is indicated at 68 in fig. 2. In the pilot control mechanism, the deceleration a from the targetsollDirect determination of target braking force FsollThe target-braking force FsollBypassing the
Referring now to fig. 3, a flow of a method for operating the brake system 10, in particular the second
By means of the above-described adjustment, even when the load of the motor vehicle differs or between the brake 42 and the wheel system 44When the friction coefficients are different, the target deceleration a can still be achievedsollEquivalent actual deceleration aist. This is exemplarily derived from the diagram shown in fig. 4. The abscissa of the graph in fig. 4 corresponds to the time t, and the two coordinates correspond to the braking force F and the deceleration a, respectively. At time t1A predetermined target deceleration asollTo the regulating part. The corresponding curve has the
Actual deceleration a when the load of the vehicle is largeistHas the
As can be seen from the diagram in fig. 4, the second
It goes without saying that, by means of the above-described control concept, not only different loads of the motor vehicle are compensated, but also further deviations of the
Other deviations may be caused, for example, by fluctuations in the measured supply voltage of the
Fig. 5 shows a second embodiment of the control strategy of the second
Fig. 6 shows a third embodiment of the control strategy of the second
In the above-described embodiment, the braking forces F are used as control variables of the
If the dynamics of the control strategy is to be improved again, that is to say the actual deceleration a is also usedistFaster approach to target-deceleration asollThen, when the deceleration request is determined (at time t in the above-described diagram according to fig. 4)1) The electromechanical air gap is reduced, that is to say immediately after activation of the
The regulating program described above is stored as a computer program on the memory 24 of the control and regulating device 20. The adjustment scheme is implemented in such a way that a stored computer program is implemented by the
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