DE4340932A1 - Automatic stability control for road vehicle - Google Patents

Abstract

A road vehicle (1) has sensors that determine the horizontal (ayh) and vertical (ayv) acceleration components that are used by an arithmetic processor (2) to determine transverse (ay,sp) and yaw (W') acceleration values. They are used by a regulator (4) to provide a control input (U). The forward vehicle velocity (Vx) and steering wheel angle (delta y) are also measured and used in a reference model (3.1,3.2) to control the regulator. The regulator output controls braking, power control and steering.

Description

State of the art

The invention is based on a method or a device according to the preamble of claims 1, 9, 13 and 14.

From DE-PS 35 45 715 and DE-OS 36 25 392 is a device known for propulsion or braking control in a motor vehicle, the yaw rate or to increase driving stability the lateral acceleration of the vehicle is regulated by reference variables becomes. The command variables are based on the steering angle of the driver stuff and the vehicle speed determined. For regulation thereby as actuators on the braking system and / or on the front drive system (motor) accessed.

Also in DE-OS 40 30 846 is the goal of a desired driving to achieve behavior, the yaw rate or lateral acceleration regulated to performance indicators. Again, the leaders sizes from the steering angle and the vehicle speed Right. The steering system (rear axle steering or front axle steering or a combination of both) accessed.  

In DE-OS 42 14 642 a fault-tolerant control of the driving dynamics is proposed, in which the yaw rate is detected and regulated in the normal case, that is, in the error-free case. In the event of an error (generally a sensor failure), redundancy of the yaw rate sensor is provided without providing a second, generally expensive yaw rate sensor. If the yaw rate sensor fails, the lateral acceleration is measured as a substitute signal and a substitute signal for the yaw rate is determined from the lateral acceleration. The replacement signal is then compared with the original reference variable for regulation. That in DE-OS 42 14 642 will be considered in the context of the embodiment with reference to FIG. 1.

The object of the present invention is a system for increasing to design the driving stability of a motor vehicle in which it is used Regulation of a variable representing driving stability not no It is important to measure this size directly.

This object is achieved by the features of claims 1, 9, 13 and 14 solved.

Advantages of the invention

To improve the driving stability of a motor vehicle, a the first quantity representing the driving stability corresponds to one The first command or target variable is regulated. However, this will the first variable to be controlled is not recorded as the actual value and with the Command or target size compared, but it is used as a substitute for at least the actual size corresponding to the first size to be regulated a second representing the driving stability of the motor vehicle Size captured. According to the invention, the second size is then reduced to one  regulated second command or target variable, the second guide tion or setpoint is determined so that the to be controlled first variable the value specified by the first reference variable takes. The procedure according to the invention has the advantage that a Size can be regulated without measuring this size directly. Instead, a substitute size is measured instead. This is in It is always an advantage if a variable is to be regulated, its detection with great effort or with the installation more expensive and / or error-prone sensors is connected. The essence of the invention is here that, in contrast to DE-OS 42 14 642, for the replacement size a second reference or target variable is determined.

A particularly advantageous application of the invention The situation is when the driving state is the first to be represented the vehicle yaw rate at a first level tion or target variable should be regulated. Such greed speed speed sensors that measure the rotation rate around a vehicle-mounted vertical axis sen, are generally expensive. As a replacement for the vehicle greed to be regulated speed can therefore be the second factor in vehicle greed acceleration and / or vehicle lateral acceleration at least a location fixed to the vehicle. Such accelerations sensors are generally cheaper than yaw rate sensors. Here at can the lateral vehicle acceleration in the center of gravity of the vehicle either be sensed directly or it can cross the vehicle accelerations in at least two different vehicle-fixed locations are determined by sensors and from this the desired vehicle cross acceleration in the center of gravity of the vehicle using simple arith metic regulations.

The first command or target variable is advantageously by means of a first vehicle model determined from signals that the Fahrzu represent and / or influence the position of the vehicle. Such Signals can be the sensed vehicle longitudinal speed and / or the sensed steering angle of the vehicle.  

To determine the second command or target variable is advantageous the first reference variable is used. This can be ge see that the second command or target variable by means of a two vehicle model from the first reference variable and from signals is determined, which represent the driving state of the vehicle and / or influence. What is important here is the skilful choice of the second, derived from the first vehicle model, so that according to the first command or target variable desired driving behavior, at for example, the desired yaw rate behavior through which Regulation of the derived control variable (second variable) is achieved.

It is particularly advantageous to use the procedure according to the invention for designing a fault-tolerant control of a first variable representing the driving stability of a motor vehicle 1 to a first command or target variable. For this purpose it is determined whether there is an error. In the fault-free state, an actual variable corresponding to the first variable to be controlled is then detected and the first reference variable or reference variable is controlled by comparing this actual variable with the first reference or reference variable. As an alternative to the actual size corresponding to the first size to be regulated, at least one second size representing the driving stability of the motor vehicle is detected. According to the invention, in the event of a detected error, the second variable is regulated to a second command or target variable, the second guide or target variable being determined in such a way that the first variable to be regulated is the value specified by the first command or target variable occupies. This fault-tolerant control ensures the desired control even in the event of failure of one or more sensors and / or manipulated variables. Furthermore, this embodiment of the invention has the advantage that the controller structure present in normal operation (no error) is retained even in the event of an error. This is particularly advantageous in the case of a hierarchically organized, decentralized, coordinated driving dynamics control system, since even in the event of a fault, reliability is maintained through the decentralized controller structure and the autonomy of the subsystems (e.g. braking system, steering system, propulsion system).

These are the corresponding to the fault-tolerant regulation described above The advantageous configurations relating to the determination of the first and second sizes and first and second guide or Reference sizes can be found in the already mentioned passages.

It is particularly advantageous that the fault-tolerant control to determine an error, the first variable with at least one of the second sizes is compared.

As actuators for regulation according to the invention

• - braking systems and / or
• - power control systems (internal combustion engine or electric motor) and or
• - active rear and / or front axle steering systems can be controlled on the vehicle.

Furthermore, the invention is of course not on the excitement limited yaw rate. Rather, there are other rules sizes conceivable, for example the regulation of the float angle of a motor vehicle that is very difficult to detect directly by sensor is.

Furthermore, the invention relates to the methods described also devices for performing the method according to the invention.  

Further advantageous embodiments of the invention are the Unteran to take sayings.

drawing

The invention is illustrated in the context of exemplary embodiments with reference to FIGS. 1, 2 and 3, FIG. 1 showing the prior art as a block diagram, while FIGS. 2 and 3 show block diagrams of the invention in two exemplary embodiments. In the figures, elements of the same type are provided with the same reference symbols.

Embodiment

In FIG. 1, the prior art, as represented by the content of DE-OS 42 14 642, is to be dealt with first for a better understanding of the invention. The aim of the control arrangement shown in FIG. 1 is the control of the vehicle yaw rate w on the reference variable w _ref . For this purpose, the yaw rate of the vehicle 1 is measured as an actual variable by the yaw rate sensor 1.4 in normal operation (no error) and fed to the controller 4 . The variable w _{ref is also} fed to the controller 4 as a reference or setpoint variable. The command or target variable w _ref is determined in accordance with a vehicle model stored in block 3.1 from the steering angle delta _{y of} the vehicle and the vehicle longitudinal speed V _x . This vehicle model can be based on the well-known Ackermann condition, further details can be found, for example, in the textbook "Chassis technology: driving behavior" by Adam Zomotor, Vogel Buchverlag Würzburg, 1st edition 1987. The steering angle delta _y and the longitudinal vehicle speed V _x can be sensed by suitable sensors 1.3 and 1.6 on the vehicle 1 . The steering angle can be understood to mean the steering wheel angle, that is to say the angle of the steering wheel actuated by the driver or the steering angle of the steerable wheels. In the controller 4 , the actual variable w representing the yaw rate is then compared with the target variable w _ref and, depending on this comparison, the controller output variable u controls one or more actuators 1.5 on the vehicle 1 to minimize the controller deviation. As already mentioned, the actuators 1.5 can be a braking system, a propulsion system (for example an electrically operated throttle valve as a power control element in an internal combustion engine) and / or a steering system. Thus, the desired yaw behavior of the vehicle can be achieved in that, depending on the control deviation, individual wheels of the vehicle are braked or accelerated and / or superimposed on the steering intervention induced by the driver of the vehicle, an additional steering angle on the front axle and / or on the Rear axle is adjusted.

In Fig. 1 it is also provided that an error is detected by means of the error detection 6 . If an error is detected, the switch S is actuated in such a way that an estimated variable w _g is applied to the controller 4 on the input side instead of the actual value of the yaw rate w. This estimated yaw rate w _g is estimated in the state estimator 7 from the lateral acceleration a _y measured on the vehicle 1 (sensor 1.2 ) and the controller output signal u of the controller 4 . However, the controller 4 continues to use the reference or setpoint in the reference model 3.1 . formed size w _ref fed.

The essence of the second embodiment is now to control the yaw rate w, while maintaining a desired yaw behavior, indirectly via other, more accessible, derived variables, such as yaw acceleration or lateral acceleration. Fig. 2 shows schematic configuration of the secondary yaw rate control according to the invention. The yaw rate of a vehicle 1 is to be controlled with the aid of a controller 4 to a desired yaw behavior, which is predetermined by a reference model 3.1 . The control objective of the exemplary embodiment of the invention shown in FIG. 2 is therefore to regulate the yaw rate w of a vehicle 1 to a desired yaw behavior. As already described with reference to FIG. 1, this desired yaw behavior is represented by the command or target variable w _ref , the variable w _ref in block 3.1 . by means of a reference model, which generally simulates the vehicle behavior, as a function of the longitudinal vehicle speed V _x (sensor 1.6. ) and the steering angle (sensor 1.3 ).

Instead of using an expensive yaw rate sensor ( 1.4 in FIG. 1), according to the invention another variable to be detected with cheaper sensors is provided as the control variable. In this exemplary embodiment, the yaw acceleration w 'is used as the control variable as a substitute for the yaw rate w' as the derived control variable and / or the transverse acceleration a _{y, Sp} present in the center of gravity of the vehicle 1 . These derived control variables are fed to the controller 4 . The yaw acceleration w 'and the transverse acceleration a _{y, Sp} present in the center of gravity of the vehicle 1 can be determined by a simple arithmetic operation (block 2 ) from the _{sensor-acquired} transverse accelerations a _yh and a _yv . Here are the sensors 1.1 and 1.2 . detected transverse accelerations a _yh and a _yv the transverse accelerations attacking at different locations of the vehicle 1 , for example at locations that are once in the longitudinal direction of the vehicle in front of the center of gravity and behind the center of gravity. By means of simple geometrical considerations, arithmetic operation 2 is used to obtain the lateral acceleration a _{y, Sp} and / or the yaw acceleration w ′, which acts in the center of gravity of the vehicle, from these lateral acceleration data.

In order to obtain the desired yaw rate w _ref , it is crucial that the desired yaw behavior originally obtained by the reference model 3.1 is retained by a skilful choice of a derived reference model 3.2 with respect to the new controlled variables. To determine the new command or target variables w ′ _ref and / or a _{y, ref} , the target yaw rate w _ref representing the desired yaw behavior is supplied to block 3.2 . Taking into account the current vehicle longitudinal speed V _x and / or the current steering angle delta _y , the new command and target variables w ′ _ref and / or a _{y, ref are} determined and fed to the controller 4 . Here, the new command or setpoints w ′ _ref and / or a _{y, ref are} compared with the current actual values w ′ and / or a _{y, Sp} and a controller output signal u is formed, so that, depending on the controller output signal u, the or the actuator (s) 1.5 on the vehicle 1 are controlled to minimize the controller deviation.

According to the invention, the secondary yaw rate control described above can be used as described with reference to FIG. 2. This has the advantage that the ia expensive yaw rate sensor ( 1.4 in FIG. 1) can be dispensed with while maintaining the desired yaw rate control. In addition, it can also be provided according to the invention to use the secondary yaw rate control in the event of a detected sensor and / or manipulated variable error. This embodiment of the invention is illustrated below with reference to FIG. 3.

The exemplary embodiment shown in FIG. 3 is based on the so-called hierarchically organized driving dynamics control. Characteristic of such a regulation is the division into a coordination and a regulation level, with the latter including, for example, one or more subsystems that are designed for steering, braking, propulsion (motor, translation) and / or for an adjustable Chassis (spring / damper) of vehicle 1 engage. In FIG. 3, the vehicle 1 can be seen with a subsystem to which an actuator 1.5. belongs. The control structure is decentralized because each subsystem is equipped with a local controller (main controller 5 ).

In the coordination level, according to the present Situations the following tasks are omitted:

• - Decoupling of the subsystems by correction signals (is in this Embodiment not shown, since only from a subsystem is gone.
• - Specification of the driver's desired behavior
• - Specification of suitable target and controller variables (yaw rate w _ref or w in this exemplary embodiment).
• - Adjustment of the controller parameters.
• - Strategies for activating an intervention.

As information variables for a situation-appropriate coordination to serve:

• - Driver characteristics
• - Vehicle characteristics
• - environmental characteristics

Such a hierarchically organized driving dynamics control has the following advantages:

• - maintaining the self-sufficiency of the subsystems
• - Reliability due to the decentralized structure
• - Flexibility through the division into hierarchical organization
• - Any extension to further new subsystems.

In this embodiment, the sekun according to the invention is now intended där yaw rate control in such a hierarchical Organized driving dynamics control can be integrated, so also in In the event of a sensor failure or a control value failure, the pre parts of this regulatory structure are retained. Here you get a hierarchically organized fault-tolerant driving dynamics control. It should be noted that the sekun invention The regulation does not apply to an application in the context of a hierarchy organized driving dynamics control is limited, but self-ver is always used when the The "actual" (primary) controller size is to be replaced by a Replacement size.

Fig. 3 shows the schematic construction of the hierarchical intelligent fault-tolerant vehicle dynamics control. The hierarchical organization with the regulation and coordination levels can be easily recognized from this. On the control level there is the main controller 5 for the corresponding subsystem with the actuator 1.5 . on the vehicle 1 . In this exemplary embodiment, the yaw rate w of the vehicle 1 by means of the sensor 1.4 is used as the controlled variable. measured and fed to the main controller 5 as the actual variable. The main controller 5 is also supplied with the command or setpoint variable w _ref for the yaw rate. The main controller 5 is designed such that the controls of the actuator 1.5 . depending on the controller output signal (manipulated variable u₁), the target variable w _ref for the yaw rate is sensibly followed.

As already described in the context of the first exemplary embodiment, the command or target variable w _ref for the yaw rate is determined by means of a desired reference model 3.1 . determined from the vehicle's longitudinal speed V _x and the steering angle delta _y . According to the invention, an additional manipulated variable is now to be generated from the coordination level, so that the quality of this control loop is maintained in a way that is satisfactory in the event of a sensor or manipulated variable failure.

This is now achieved according to the invention in that a redundancy controller 4 is used to generate the additional actuating variable u₂ ver. This redundancy controller 4 can be dimensioned such that, in the normal case (no error), it works harmoniously with the main controller 5 and takes over the control in the event of a failure of the main controller 5 . The entire system is therefore fault-tolerant against a control value failure. If the redundancy controller 4 is now additionally designed for secondary yaw rate control as described in the first exemplary embodiment, then the fault tolerance in the event of a sensor failure is also achieved. For this purpose, as already described, another derived variable is used as the control variable, in these examples the yaw acceleration w ′ and / or the lateral acceleration a _{y, Sp} in the vehicle's center of gravity. As already described, these substitute variables are detected by sensing the transverse accelerations a _yv and a _yh (sensors 1.1 and 1.2 ) and calculation (arithmetic conversion 2 ). For the design of the redundancy controller 4 , it is crucial that the original by the reference model 3.1 . Desired yaw behavior remains unchanged with a clever choice of a derived reference model 3.2 with respect to the new controlled variable.

For error detection 6 , the sensed yaw rate w can be compared with the sensed or ascertained transverse acceleration a _{y, Sp} in the vehicle center of gravity and / or with the sensed or ascertained yaw acceleration w '. As soon as a sensor failure is detected, the main 5 or redundancy controller 4 is switched off. The remaining controller then continues to work as possible without interrupting the entire control system, so that the control behavior of the yaw rate control is continued. With this measure, two "sensors" (sensor 1.4 for w and sensors 1.1 and 1.2 for w ') are available for the same control, so to speak. This has created a fault-tolerant, intelligent yaw rate control even in the event of a failure of the yaw rate sensor.

As an alternative to the embodiment shown in FIG. 3, the summation point 7 can of course be designed as a simple switch which, in the normal case (no error), the manipulated variable u 1 of the main controller 5 to the actuator 1.5 . forwards and in the event of a fault, the manipulated variable u₂ of the redundancy controller 4 to the actuator 1.5 . forwards. The switching state of such a switch is determined by error detection 6 .

Claims (19)

1. A method for controlling the driving stability of a motor vehicle ( 1 ) representing the first variable (w) to a first command or target variable (w _ref ), wherein

• - as an alternative, the at least one second variable (w ′, ay _Sp ) which represents the driving stability of the motor vehicle ( 1 ) corresponds to the actual variable and corresponds to the actual variable,

characterized in that

• - The second variable (w ', ay _Sp ) is regulated to a second management or target variable (w' _ref , ay _{Sp, ref} ), whereby
• - The second command or target variable (w ' _ref , ay _{Sp, ref} ) is determined such that the first variable to be controlled (w) assumes the value specified by the first command variable (w _ref ).

2. The method according to claim 1, characterized in that

• - As the first variable representing the driving state, the vehicle yaw rate (w) is regulated to the first command or target variable (w _ref ) and
• - As an alternative to the vehicle yaw rate to be controlled (w), the vehicle yaw acceleration (w ') and / or the vehicle lateral acceleration (ay _Sp ) is detected as a second variable at at least one fixed location in the vehicle.

3. The method according to claim 2, characterized in that the driving tool lateral acceleration (ay _Sp ) is detected in the center of gravity of the vehicle. 4. The method according to claim 3, characterized in that the vehicle cross-acceleration (ay _Sp ) is determined in the center of gravity of the vehicle from sensor-detected vehicle transverse accelerations at at least two different locations fixed to the vehicle. 5. The method according to claim 1, characterized in that the first command or target variable (w _ref ) are determined by means of a first vehicle model from signals (delta _y , V _x ) which represent and / or influence the driving state of the vehicle. 6. The method according to claim 1 or 5, characterized in that the first command variable (w _ref ) is used to determine the second command or target variable (w ' _ref , ay _{Sp, ref} ). 7. The method according to claim 6, characterized in that the second reference or target variable (w ' _ref , ay _{Sp, ref} ) by means of a second vehicle model from the first reference variable (w _ref ) and signals (delta _y , V _x ) is determined, which represent and / or influence the driving state of the vehicle. 8. The method according to claim 5 and 7, characterized in that the vehicle longitudinal speed (V _x ) and / or the steering angle (delta _y ) of the vehicle are detected as signals which represent and / or influence the driving state of the vehicle. 9. A method for fault-tolerant regulation of a first variable (w) representing the driving stability of a motor vehicle ( 1 ) to a first command or target variable (w _ref ), wherein

• - it is determined whether there is an error, and
• - In the error-free state one of the first variable (w) corresponding to the actual variable is detected and is controlled by comparing this actual variable with the first command or target variable (w _ref ) to the first command or target variable (w _ref ) , and
• - as an alternative, the at least one second variable (w ′, ay _Sp ) which represents the driving stability of the motor vehicle ( 1 ) corresponds to the actual variable and corresponds to the actual variable,

characterized in that

• - In the event of a detected error, the second variable (w ′, ay _Sp ) is regulated to a second reference or target variable (w ′ _ref , ay _{Sp, ref} ), whereby
• - The second command or target variable (w ' _ref , ay _{Sp, ref} ) is determined such that the first variable to be controlled (w) assumes the value specified by the first command or target variable (w _ref ).

10. The method according to claim 9, characterized in that to determine an error, the first variable (w) with at least one of the second variables (w ', ay _Sp ) is compared. 11. The method according to any one of the preceding claims, characterized in that for controlling the first and / or second variables on the respective command or target variables as actuators

• - a braking system and / or
• - a power control system and / or
• - An active rear and / or front axle steering on the vehicle ( 1 ) is controlled.

12. The method according to any one of the preceding claims, characterized ge indicates that the first variable representing the driving state the float angle of the vehicle to the first guide or target size is regulated. 13. The apparatus for performing the method according to claim 1, characterized in that

• - First means ( 1.1 , 1.2. , 2 ) are provided, by means of which, for the actual size corresponding to the first size (w) to be controlled, at least one second size (w ′, ay _Sp ) representing the driving stability of the motor vehicle ( 1 ) is detected becomes,

characterized in that

• - Second means ( 4 ) are provided, by means of which the second variable (w ', ay _Sp ) is regulated to a second reference or target variable (w' _ref , ay _{Sp, ref} ), wherein
• - Third means ( 3 , 3.1 , 3.2 ) are provided by means of which

second command or target variable (w ′ _ref , ay _{Sp, ref} ) is averaged such that the first variable to be controlled (w) assumes the value specified by the first command variable (w _ref ). 14. An apparatus for performing the method according to claim 9, where at

• - Means for error detection ( 6 ) are provided, by means of which it is determined whether an error is present, and
• - A main controller ( 5 ) is provided, by means of which, in the correct state, one of the first variables to be controlled (w) corresponding to the actual variable is detected and by means of a comparison of this actual variable with the first command or target variable (w _ref ) to the first Command or target variable (w _ref ) is regulated, and
• - First means ( 1.1 , 1.2. , 2 ) are provided, by means of which, for the actual size corresponding to the first size (w) to be controlled, at least one second size (w ′, ay _Sp ) representing the driving stability of the motor vehicle ( 1 ) is detected becomes,

characterized in that

• - A redundancy controller ( 4 ) is provided, by means of which the second variable (w ′, ay _Sp ) is regulated to a second reference or target variable (w ′ _ref , ay _{Sp, ref} ) in the event of a detected fault, whereby
• - Third means ( 3 , 3.1 , 3.2 ) are provided, by means of which the second command or target variable (w ' _ref , ay _{Sp, ref} ) is averaged such that the first variable to be controlled (w) is determined by the first Leading or target size (w _ref ) takes a predetermined value.