METHOD AND DEVICE FOR CONTROLLING THE STABILITY OF A VEHICLE, IN PARTICULAR A UTILITY VEHICLE

Abstract

The invention relates to a method and a device for controlling the stability of a vehicle, in particular a utility vehicle, in which an anti-tilt control method is carried out in which at least one lateral acceleration signal (ay), one steering wheel angle signal (LRW) and one vehicle speed signal (v) are sensed and control signals (S1, S2) for vehicle interventions are formed therefrom and output, and a yaw control method is carried out during which the steering wheel angle signal (LRW), the lateral acceleration signal (ay) and the vehicle speed signal (v) are sensed, a yaw rate setpoint value signal (ψs) and a yaw rate actual value signal (ψi) are determined and compared with one another and a yaw control process is carried out during which control signals (S3, S4, S5) for vehicle interventions are formed and output.

Description

The invention generally relates to embodiments of a method and a device for controlling the stability of a vehicle, in particular a utility vehicle.

Stability control systems of vehicles serve to intervene in critical situations of the vehicle such as, for example, understeering, oversteering or a tendency to tilt by means of, inter alia, braking interventions, in particular modulation of the brake pressure, in such a way as to assist the driving of the vehicle.

Input variables which are used in this context are measurement signals of different sensors, in particular of a yaw rate sensor, steering wheel angle sensor and lateral acceleration sensor as well as, if appropriate, of a longitudinal acceleration sensor; in addition, driving state variables such as, for example, the mass of a vehicle and a reference speed, which are determined by other brake control systems such as ABS or EBS systems, are used to a certain extent.

In particular in utility vehicles, stability control systems are used which have one control circuit for yaw control and a further control circuit for anti-tilt control. The anti-tilt controller generally receives input signals for the lateral acceleration, the vehicle mass which is determined and the vehicle reference speed and, if appropriate, a steering wheel angle signal. The yaw controller generally receives the steering wheel angle signal, the vehicle reference speed and the yaw rate signal.

The extensive sensor systems result in corresponding costs both for the hardware of the sensors used and for the software implementation. Furthermore, the sensors, in particular the yaw rate sensor, are susceptible to faults so that a high degree of expenditure on software development is necessary for reliable implementation.

Furthermore, the individual control channels give rise to corresponding costs for the brake system, the yaw controller in this context requiring two individual control channels for the front axle.

An object of the invention is to provide a method and a device for controlling the stability of a vehicle which permit reliable control of the driving stability with relatively little expenditure.

This object is achieved by means of a method according to claim 1 and a device according to claim 14. The subclaims describe preferred embodiments.

Inventive embodiments involve estimating the actual yaw behaviour from the measured lateral acceleration, and determining the setpoint yaw behaviour from the steering wheel angle signal, and of comparing with one another the actual values and setpoint values of the yaw behaviour which are acquired in this way. In contrast to conventional systems, according to the invention no specific yaw rate sensor is needed for yaw control in order to output a yaw rate measurement signal.

This is based on the inventive realization that a lateral acceleration signal is used in any case for anti-tilt control or rolling stability control and this lateral acceleration signal can basically also be used for limiting the inclination to understeer in the yaw control without an additional yaw rate signal or yaw rate measurement signal. In contrast to existing anti-tilt controllers, in this context the steering wheel angle sensor is not dispensed with but rather the latter is consciously included not only in the anti-tilt control but also in the yaw control. As a result, a relatively high level of performance, in particular in the case of dynamic manoeuvres, is obtained compared to known anti-tilt control systems or rolling stability control systems without a steering wheel angle sensor.

The method according to embodiments of the invention and the device according to embodiments of the invention are advantageous in particular in vehicles with a large wheel base, for example lorries and buses, since the latter tend to understeer in the case of instability at low values of the coefficient of friction. In this context, according to the invention it is realized that in such vehicles an understeering intervention by braking the rear wheels on the inside of a bend is very effective while, in contrast, an oversteering intervention by braking the front wheel on the outside of a bend is less effective. In the case of train systems, the method according to embodiments of the invention is relevant in particular for the traction vehicle.

The anti-tilt control process can be carried out, in particular, on all wheels of the traction vehicle and trailer vehicle.

By eliminating the yaw rate sensor which is very costly in terms of hardware and software and is also susceptible to faults, and by including the steering wheel angle signal and lateral acceleration signal, a cost-effective and nevertheless very reliable, robust system is provided for the anti-tilt control and for the yaw control.

The invention will be explained below with reference to the appended drawing of an exemplary embodiment.

FIG. 1 shows a block diagram of a stability control system according to an embodiment of the invention.

In the stability control system 1 shown in FIG. 1, an anti-tilt control system 2 and a yaw control system 3 are provided as two control systems with common input signals. The control systems 2 and 3 may be embodied here in terms of software in a common control unit or in two control units which are separated in terms of hardware.

The anti-tilt control system 2 receives as an input signal a vehicle mass signal m which is determined by a subordinate brake system, for example an ABS or EBS control system, in a manner known per se as a reference value from the inertia when different accelerations or braking effects are acting, if appropriate including axle load sensors. Furthermore, the anti-tilt control system 2 receives a vehicle speed signal v which is present, for example, in the brake systems of the ABS or EBS system as a reference speed and is determined, in particular, from the wheel speeds which are determined by wheel speed sensors, and forms the basis of the additionally implemented slip control systems and, if appropriate, braking force distribution systems. As an alternative, a measurement signal can also be received from a wheel axle as a vehicle speed signal v. Furthermore, the anti-tilt control system 2 receives a lateral acceleration signal ay from a lateral acceleration sensor 4 of the vehicle, and a steering wheel angle signal LRW from a steering wheel angle sensor 5 of the vehicle. In block 8 in the anti-tilt control system 2, the tilting limit is estimated from the vehicle mass signal m and an estimated tilting limit signal c1 is output.

Furthermore, in block 9 the tilting dynamics are estimated from the steering wheel angle signal LRW and the vehicle speed signal v; the locked steering wheel angle and the vehicle speed permit here the change in the lateral acceleration to be estimated and an estimated tilting dynamics signal c2 to be output. According to this embodiment, the estimation of the tilting dynamics in block 9 does not comprise the inclusion of the lateral acceleration or of the lateral acceleration signal ay but merely the dynamic change which is to be expected from the steering wheel angle LRW and the vehicle speed v. In this context, the steering wheel angle which is determined and the vehicle speed permit sufficiently precise estimation of the expected tilting dynamics in order to subsequently receive the signals c1 and c2 in a comparison device 10 and to compare the tilting limit which is determined or estimated in block 8 with the tilting dynamics estimated in block 9, wherein the lateral acceleration signal ay is advantageously additionally included in this comparison.

The comparison device 10 therefore compares the tilting angles or tilting torques which are expected from the lateral acceleration and the tilting dynamics with the estimated tilting limit, as indicated in FIG. 1 by the plus and minus signs, and passes on the anti-tilt comparison signal c3, which is generated by the comparison and communicates the risk of tilting or probability of tilting, to an anti-tilt controller 12 which subsequently determines the scope of an anti-tilt control process and initiates the latter by outputting a control signal c4 to a deceleration controller 14 for controlling the deceleration by action of the brake on one or more axles and/or to a controller 15 for the engine torque for setting an engine braking effect, which in turn output control signals S1, S2 to the respective actuating devices. The scope of the actuation of the controllers 14 and 15 depends on the necessary intervention such as, for example, is also known in the case of actuation of the vehicle brakes or of an engine brake in the case of brake control in the longitudinal direction. According to the invention, the deceleration controller 14 can act on one of more brakes of the traction vehicle and trailer vehicle, preferably it acts on all the brakes of the traction vehicle and trailer vehicle or trailer.

The yaw control system 3 has a device 16 for determining a yaw setpoint value which receives the steering wheel angle signal LRW and the vehicle speed signal v and determines therefrom the yaw setpoint value which is input by the driver and outputs said yaw setpoint value as a yaw setpoint value signal ψs. During this determination, it is possible in particular to set travel on a circular path with the steering wheel angle lock and the vehicle speed to which a specific yaw rate is assigned. Furthermore, a device 17 for estimating a yaw actual value, i.e. the actual yaw rate of the vehicle about its vertical axis, is provided, which device 17 receives the lateral acceleration signal ay and the vehicle speed signal v and outputs a yaw actual value signal ψi. The yaw control system 3 therefore advantageously primarily determines the yaw behaviour of the traction vehicle.

The estimation in the device 17 can take place, in particular, by forming a ratio or quotient of the lateral acceleration signal ay and the vehicle speed signal y, i.e. as ay/v. This is based on the inventive concept that during cornering the yaw rate or the yaw actual value ψi of the centre of gravity of the traction vehicle is formed by this quotient ay/v, and this value can be used in cases in which no lateral skidding movement is present, i.e. during desired cornering or even in the case of understeering. It can therefore be used for control in the case of understeering of the traction vehicle; use in the case of an inclination to oversteer or in the case of oversteering, during which basically a skidding movement with a veering-off rear part of the vehicle and front part of the vehicle can take place and therefore the yaw rate of the traction vehicle no longer corresponds to the yaw rate of its centre of gravity, is therefore detected according to the invention as not being so advantageous and is not carried out according to this embodiment.

The yaw setpoint value signal ψs and the yaw actual value signal ψi are subsequently output to a comparison device 18 which compares these values with one another. In this context, it is advantageously determined whether the difference between the setpoint value and the actual value exceeds a predefined threshold value. The comparison device 18 outputs a comparison signal c5 to a yaw controller 20 which subsequently actuates, with a control signal c6, a controller 21 for the engine torque and/or a controller 22 for brake slip control per side and/or a brake controller 23 of the trailer, which respectively output control signals S3, S4, S5 to corresponding actuating devices. AS a result, the controller is correspondingly actuated for the engine torque and/or the brake as in the anti-tilt control system 2 above. Basically, the devices 15 and can also be embodied as a common engine torque controller which is therefore actuated by the anti-tilt controller 12 or yaw controller 20 depending on the instability which is detected.

The devices 8 to 23 in FIG. 1 are advantageously embodied purely in software terms so that implementation as a program in one or more existing control devices is possible.

Claims

1. Method for controlling the stability of a vehicle, in particular a utility vehicle, in which an anti-tilt control method is carried out in which at least one lateral acceleration signal (ay), one steering wheel angle signal (LRW) and one vehicle speed signal (v) are received and control signals (S1, S2) for vehicle interventions are formed therefrom and output, anda yaw control method is carried out during which the steering wheel angle signal (LRW), the lateral acceleration signal (ay) and the vehicle speed signal (v) are received, a yaw rate setpoint value signal (ψs) and a yaw rate actual value signal (ψi) are determined and compared with one another, and a yaw control process is carried out during which control signals (S3, S4, S5) for vehicle interventions are formed and output.

2. Method according to claim 1, characterized in that the yaw rate actual value signal (ψi) is determined, in particular estimated, from at least the lateral acceleration signal (ay) and the vehicle speed signal (v) without using a yaw rate sensor or a yaw rate measurement signal.

3. Method according to claim 2, characterized in that, in the yaw control method, a yaw rate setpoint value signal (ψs) is determined from the steering wheel angle signal (LRW) and the vehicle speed signal (v),the yaw rate actual value signal (ψi) is estimated from the lateral acceleration signal (ay) and the vehicle speed signal (v), and the yaw rate setpoint value signal (ψs) and the yaw rate actual value signal (ψi) are compared and a yaw controller (20) is actuated as a function of the comparison.

4. Method according to claim 3, characterized in that the yaw rate actual value signal (ψi) is estimated from a ratio between the lateral acceleration (ay) and the vehicle speed (v).

5. Method according to claim 3 or 4, characterized in that the yaw controller (20) actuates a controller (21) for an engine torque and/or at least one brake controller (22, 23).

6. Method according to claim 5, characterized in that the brake controller (22, 23) is a brake slip controller (22), preferably of the rear axle of the traction vehicle, which acts per side of the vehicle, and/or a brake controller (23) of a trailer.

7. Method according to one of claims 3 to 6, characterized in that the yaw control method is carried out only when understeering of the traction vehicle or an inclination of the traction vehicle to understeer is detected.

8. Method according to claim 7, characterized in that, when understeering of the traction vehicle or an inclination of the traction vehicle to understeer is detected, the wheel on a rear axle or on both rear axles which is on the inside of a bend is braked.

9. Method according to one of the preceding claims, characterized in that, in the anti-tilt control method, a vehicle mass signal (m) is additionally received, a tilting limit of the vehicle is estimated from the vehicle mass signal (m), and in a downstream comparison device (10) a tilting state and/or a risk of tilting and/or a probability of tilting are determined from at least the estimated tilting limit and tilting dynamics which are estimated from the steering wheel angle signal (LRW) and the vehicle speed signal (v).

10. Method according to claim 9, characterized in that a reference value of a control system, preferably of a brake control system (ABS, EBS) is used as a vehicle speed signal (v).

11. Method according to claim 9 or 10, characterized in that, during the comparison of the estimated tilting limit with the estimated tilting dynamics, the lateral acceleration signal (ay) is additionally received, and an anti-tilt controller (12) is actuated on the basis of the result of the comparison.

12. Method according to claim 11, characterized in that the anti-tilt controller (12) actuates a deceleration controller (14) for one or more brakes, preferably all the brakes, of the traction vehicle and of the trailer vehicle.

13. Method according to claim 11 or 12, characterized in that the anti-tilt controller (12) actuates a controller (15) for an engine torque.

14. Device for controlling the stability of a vehicle, which has: an anti-tilt control system (2), which receives at least one lateral acceleration signal (ay) from a lateral acceleration sensor (4), a steering wheel angle signal (LRW) from a steering wheel angle sensor (5) and a vehicle speed signal (v) and forms control signals (S1, S2) for vehicle interventions therefrom and outputs said control signals, and a yaw control system (3) which receives the lateral acceleration signal (ay), the steering wheel angle signal (LRW) and the vehicle speed signal (v), determines a yaw rate setpoint value signal (ψs) and a yaw rate actual value signal (ψi) and compares them with one another, carries out a yaw control process, and outputs control signals (S3, S4, S5) for vehicle interventions.

15. Device according to claim 14, characterized in that the yaw control system (3) is embodied without including a yaw rate sensor or a yaw rate measurement signal.

16. Device according to claim 14 or 15, characterized in that the yaw control system (3) has: a device (16) for determining a yaw rate setpoint value signal (ψs), which device (16) receives at least the steering wheel angle signal (LRW) and the vehicle speed signal (v),a device (17) for determining a yaw rate actual value signal (ψi), which device (17) receives at least the lateral acceleration signal (ay) and the vehicle speed signal (v), anda comparison device (18) which receives the yaw rate setpoint value signal (ψs) and the yaw rate actual value signal (ψi) and compares them with one another, and a yaw controller (20) which receives an output signal (c5) of the comparison device (18).

17. Device according to claim 15 or 16, characterized in that the device (17) for determining the yaw rate actual value signal (ψi) estimates the yaw rate actual value signal (ψi) from a ratio between the lateral acceleration (ay) and the vehicle speed (v).

18. Device according to claim 16 or 17, characterized in that the yaw controller (20) actuates a controller (21) for an engine torque and/or at least one controller (22, 23) for a braking intervention.

19. Device according to claim 18, characterized in that the yaw controller (20) actuates a controller (22) for brake slip control per side, preferably of the rear axle of the traction vehicle, and/or a brake controller (23) of a trailer.

20. Device according to one of claims 16 to 19, characterized in that the yaw control system (3) carries out the yaw control method only when understeering of the traction vehicle or a tendency of the traction vehicle to understeer is detected.

21. Method according to claim 20 and claim 19, characterized in that, when understeering or the tendency of the traction vehicle to understeer is detected, the yaw controller (20) actuates the controller (22) in order to brake the wheel on the inside of a bend of a rear axle or of both rear axles.

22. Device according to one of claims 14 to 21, characterized in that the anti-tilt control system (2) receives a vehicle mass signal (m), for example from a further brake control system (ABS, EBS), in particular a brake slip control system.

23. Device according to one of claims 14 to 22, characterized in that the anti-tilt control system (2) has: a device (8) for estimating a tilting limit, which device (8) receives a vehicle mass signal (m),a device (9) for estimating tilting dynamics, which device (9) receives the steering wheel angle signal (LRW) and the vehicle speed signal (v),a comparison device (10) for receiving the output signals (c1, c2) of the device (8) for estimating a tilting limit and the device (9) for estimating tilting dynamics, for receiving the lateral acceleration signal (ay) and for outputting an anti-tilt comparison signal (c3),an anti-tilt controller (12) for receiving the anti-tilt comparison signal (c3) and actuating a deceleration controller (14) for brakes and/or for actuating a controller (15) for an engine torque.

24. Device according to claim 23, characterized in that the deceleration controller (14) is a controller for one or more brakes, preferably all the brakes, of the traction vehicle and of the trailer vehicle.