DE10325182A1 - Adjusting braking or drive moment acting on wheel in motor vehicle involves regulating longitudinal force or parameter derived from it depending on detected driver's intentions - Google Patents

Abstract

The method involves measuring the driver's specified braking or acceleration intention with a sensor arrangement, measuring a longitudinal force acting on a wheel with a wheel force measurement sensing arrangement and regulating the longitudinal force or a parameter derived from it depending on the driver's intentions. The normal force on the wheel is measured and used for regulation. An independent claim is also included for the following: (a) an arrangement for adjusting the braking or drive moment acting on a wheel in a motor vehicle.

Description

The The invention relates to a method for adjusting the on a wheel acting braking or driving torque according to the preamble of the claim 1, and a corresponding device according to the preamble of the claim 7th

modern Motor vehicles usually include a whole host of systems that by specifying braking torque or drive torque for driving operation act. These include in particular driving dynamics controls, including all in the following systems that intervene in driving operations, e.g. ESP (electronic Stability Program) ASR (traction control system), ABS (anti-lock braking system), etc. understood be understood, and systems for braking force distribution are understood.

A Driving dynamics control regulates wheel slip by specifying the target brake pressure. The CP value of a wheel brake, i.e. the ratio between that on the wheel brake exerted Brake pressure and that on the wheel actually acting braking force is usually constant. Brake pressure and braking force are usually proportional to each other. This proportionality is in but in practice disturbed by various factors. For example, the braking force dependent from the wear of the Brake and can especially at high temperatures by so-called Reduce fading. By specifying a specific one Brake pressure can be the one you want Braking effect can therefore not be achieved. Other interferences can arise, for example with an additional Result of the drive train torque.

at known driving dynamics controls and braking force distribution systems the mentioned interferences are not considered. The brake pressure setting is therefore not under the mentioned interference optimal.

Also Systems for controlling the drive torque are subject to interference in the transmission path between internal combustion engine and wheel. Engine torque and drive torque are therefore not always proportional to one another. The scheme is therefore inaccurate.

It is therefore the object of the present invention to compensate for such interference.

Is solved this object according to the invention by the specified in claim 1 and in claim 7 Characteristics. Further embodiments of the invention are the subject of subclaims.

The essential idea of the invention is that on a wheel indeed acting longitudinal force to measure by means of a wheel force sensor system in order to make a statement about the Braking effect of the wheel brake or the actually acting drive torque to get and use the result in a scheme. Thereby it becomes possible e.g. carry out a much more precise slip control and to compensate for the disturbances mentioned.

at the sensor measuring the wheel force is a sensor, the forces acting on the wheel measures directly and, for example, at the wheel bearing or directly can be arranged on the tire.

According to one first embodiment of the invention is the measured longitudinal force or a derived one Torque value fed to a controller as actual value. The longitudinal force or the corresponding one Drive or braking torque can thus be regulated to a setpoint become. The disturbing influences acting on the wheel brake or on the drive train can occur this way and eliminates the braking torque acting on a wheel or drive torque can be set precisely. As part of a braking force distribution system or a vehicle dynamics control, it is thus possible to set the brake pressure in such a way that the one you want Braking effect is achieved.

Out of actuation the brake pedal can e.g. a target braking torque is calculated and by means of Sensor force measuring wheel force (RmS) the actual braking torque can be measured. The controller can now determine the difference between the setpoint and the Adjust the actual value measured by RmS.

According to one another embodiment the invention is the longitudinal force measured and as part of a vehicle dynamics control for calculation a setpoint of the controlled variable. With vehicle dynamics controls, e.g. ESP, ASR, ABS, etc. is common the wheel slip is regulated to a setpoint. The target slip is a function of the longitudinal, transverse and normal forces acting on the wheel. This personnel have been estimated so far and were therefore relatively imprecise. When using a longitudinal, transverse and / or normal force sensor can be the appropriate size directly measured and used to calculate the target slip.

When braking straight ahead, an optimized driving or braking behavior can be achieved if at least two wheels of one axle, preferably all wheels of the vehicle, approximately have the same longitudinal slip. This is fulfilled if the ratio of longitudinal force and normal force is constant and therefore: F L / F N = μ res = const = K where F _{L is} the measured longitudinal force and F _{N is} the wheel contact force or normal force. By using a longitudinal and / or normal force sensor, on the one hand the setpoint slip can be determined precisely and on the other hand the required braking or drive torque can be set precisely. If, for example, the normal force is measured using a normal force sensor, the longitudinal force can be regulated as a function of the normal force. With dynamic wheel relief or load during cornering, the longitudinal force can be readjusted accordingly, for example.

To prevent the vehicle from breaking out, individual wheels, in particular the wheels of the rear axle, can also be braked. In this case, the ratio of longitudinal force and normal force on a rear wheel would be smaller than on a front wheel. The following applies to the constant K _{V of} a front wheel: K V = K H · (1 + k)

wobei F_N,i die Normalkraft am Rad i, F_L,i die Längskraft am Rad i und F_Q,i die Querkraft bzw. die Seitenkraft am Rad i ist.In order to be able to achieve optimum driving or braking behavior even when cornering, the longitudinal wheel force F _L and the lateral wheel force F _Q are preferably measured and the corresponding values are fed to a controller. Optimal traction is obtained if the ratio between the resulting braking force (root term) acting in the horizontal direction and the normal force is the same for each wheel, whereby:

where F _{N, i is} the normal force on wheel i, F _{L, i is} the longitudinal force on wheel i and F _{Q, i is} the lateral force or the lateral force on wheel i.

Also in this case individual wheels, in particular the rear wheels be slowed down.

Preferably will also be the one working on the wheels Normal force measured and the corresponding value fed to the controller. The Control algorithm can thus be static (by loading the vehicle) and dynamic load changes (by cornering or braking) and take into account the brake pressure Adapt individually to the bike. This is preferably done on the condition that no unwanted Yaw moment occurs.

According to one another embodiment of the invention, the control algorithm is dependent on that using RmS measured longitudinal force corrected. If the brake is worn or grips poorly if a brake pressure is specified, it is comparatively too low Braking effect. The regulation is therefore delayed. By a Correction of the control algorithm can e.g. the reinforcement of the Control algorithm increased in this way faster regulation is achieved.

The Controller is preferably capable of at least one actuator from the group consisting of a steering actuator, the clutch, the The transmission, the brake and / or the engine of the vehicle to meet the driver's request (braking, accelerating, cornering).

The Invention is illustrated below with reference to the accompanying drawings explained in more detail. It demonstrate:

1 a schematic representation of a brake slip controller of a vehicle dynamics control;

2a the longitudinal and normal forces acting on a wheel;

2 B the longitudinal and transverse forces acting on a wheel;

3 a controller arrangement for performing slip control when driving straight ahead; and

4 a controller arrangement for performing yaw moment control.

1 shows an electro-hydraulic brake system with a control unit 3 , in which a vehicle dynamics control function, such as ABS, ASR and / or ESP, is integrated as software.

The electro-hydraulic brake system includes a sensor 2 (Brake value sender), which the driver presses on the brake pedal 1 predetermined braking request and a corresponding signal to the control unit 3 transfers. The control unit 3 receives data from various sensors (not shown) about the current driving condition, such as speed or steering angle, and performs slip control. The control unit determines this 3 Signals S for a hydraulic unit 4 , which includes several wheel pressure modulators in which the signals 5 in brake pressures for the individual wheels 5a - 5d be implemented.

When braking, depending on the driver's braking request, the brakes 6 of the wheels 5a - 5d a predetermined brake pressure posed. Due to various interferences, especially due to a non-constant CP value of the brakes 6 , can on the wheels 5a - 5d Actual braking force deviate significantly from the desired braking force.

The actual braking force is therefore measured using a wheel force sensor system 7 measured with a longitudinal force sensor (F _L ) and the control unit 3 supplied as actual value. The control unit 3 regulates the longitudinal force F _L (or a corresponding moment) to a setpoint. The disturbances mentioned can thus be compensated for.

The control unit 3 regulates the braking force preferably in such a way that on all wheels 5a - 5d approximately the same longitudinal slip occurs. This means that the quotient of longitudinal and normal force F _{L, i} and F _{N, i is} essentially constant for all wheels. Therefore:

The wheel contact force or normal force F _N acting on the individual wheels is also determined by means of the sensor system measuring the wheel force 7 measured and the control unit 3 fed. As a result, static (due to vehicle loading) and dynamic load changes (due to cornering or braking) can be taken into account and the optimal longitudinal forces F _L can be set individually for the wheel.

When cornering, it is on the wheels 5a - 5d acting brake pressure preferably set such that for the longitudinal F _{L, i} and normal forces F _{N, i of} all wheels 5a - 5d the following relationship applies:

In this case, the transverse force F _{Q, i} , the longitudinal force F _{L, i} and the normal force F _{N, i are} preferably measured by the wheel force sensor system 7 measured and the longitudinal force regulated depending on the other two quantities. The rear axle of the vehicle can also be braked to additionally stabilize the vehicle. In this case, K in _{front, left} = K in _{front, right} = (1 + k) · K in _{back, left} = (1 + k) · K in _{back, right,} where k is on the order of 0.2.

The RmS 7 Information obtained can also be used to calculate a setpoint of the control, such as a setpoint slip or a setpoint yaw moment. The calculation based on the RmS 7 measured forces is much more accurate than an estimate as it is carried out in the prior art.

alternative can also the control algorithm of the vehicle dynamics control to the current Brake condition can be adjusted. In the case of crazy or bad gripping brake is set when a brake pressure is specified comparatively low braking effect. The regulation is therefore delayed. These disturbances can be compensated for by correcting the control algorithm become. The correction can be made, for example, by changing a control gain or the duration of a control cycle (e.g. with ABS).

2a shows the forces acting on a wheel, the longitudinal force F _L in the circumferential direction of the wheel 5 acting force and the normal force F _{N is} a force acting perpendicular to the contact surface. The normal force F _N depends, for example, on the load on the vehicle, the load distribution, the wheel load distribution, uneven road surfaces, etc.

2 B shows in addition to the longitudinal tire force F _L , the lateral force F _Q , which is directed transversely to the side surface of a tire.

3 shows a controller arrangement for slip control. The controller arrangement comprises means 10 . 11 for detecting the driver's request, which is essentially defined by the position of the accelerator pedal and the actuation of the brake when driving straight ahead. The reference symbol denotes 10 a sensor for determining the accelerator pedal position and the reference symbol 11 a brake value transmitter for recording a braking request. The measured values result in block 12 either a desired drive torque or a desired braking torque. The desired torque or a value proportional to it (eg a braking force) becomes a controller 13 supplied as setpoint.

The regulator 13 is with several actuators 14 - 17 connected with which the driving state 18 influenced, ie acceleration or deceleration can be effected. In the present exemplary embodiment, the clutch is an actuator 14 , The gear 15 , the internal combustion engine 16 and the brake 17 intended. By actuating the actuators 14 - 17 acceleration or deceleration can be achieved.

The one on a wheel 5a - 5d acting longitudinal force F _L is determined by the wheel force sensor system (RmS) 19 measured and from this the driving state 18 of the vehicle, in particular the current braking and driving torque, and the controller 13 supplied as actual size. The RmS 19 comprises at least one longitudinal force sensor for detecting the actually acting acceleration or braking forces. The regulator 13 can now regulate the longitudinal force or the associated torque to the setpoint. By recording the driving status using RmS, disturbing influences such as worn brake shoes or fading on the brakes can be corrected.

In addition to the longitudinal force sensor, the RmS preferably also includes a normal force sensor that measures the wheel contact force on the individual wheels 5a - 5d detected. The corresponding signals are sent to the controller 13 also fed. The normal forces can thus be taken into account in the slip control and the longitudinal forces can be set individually for the wheel.

wobei F_N,i die Normalkraft am Rad i und F_L,i die Längskraft am Rad i ist. Bei Kenntnis der an den Rädern wirkenden Normalkraft F_N,i kann somit die optimale Bremskraft F_L radindividuell eingestellt werden. Dies erfolgt unter der Nebenbedingung, dass die Summe aller Längskräfte F_L,i gleich dem gewünschten Gesamt-Antriebs- bzw. Bremskraft entspricht.In the case of straight braking, for example, optimum driving behavior can be achieved if all of the wheels have approximately the same longitudinal slip. This is achieved if the quotient of longitudinal and normal force is the same for all wheels and the following therefore applies:

where F _{N, i is} the normal force on wheel i and F _{L, i is} the longitudinal force on wheel i. If the normal force F _{N, i} acting on the wheels is known, the optimum braking force F _L can thus be set individually for the wheel. This takes place under the secondary condition that the sum of all longitudinal forces F _{L, i} corresponds to the desired total drive or braking force.

Optional the rear axle can also be braked to add to the vehicle stabilize and oversteer to prevent.

4 shows a controller arrangement compared to that in 3 shown arrangement around a device 21 - 23 is expanded to detect a desired yaw moment and a desired lateral acceleration. The reference symbol denotes 21 a device for detecting a steering wheel angle and the reference numeral 22 a sensor system for recording dynamic vehicle variables, such as the vehicle speed or the lateral acceleration, which are required to determine the desired yaw moment or the desired lateral acceleration.

The desired yaw moment and the desired lateral acceleration are in block 23 calculated and the controller 13 supplied as the target variable. The regulator 13 is next to the previously mentioned actuators 14 - 17 with a steering plate 20 connected with which the steering angle can be influenced. The current driving state, which is described when cornering, among other things, by the yaw rate and the lateral acceleration of the vehicle is in block 18 shown. The forces actually acting on the wheels are in turn measured using the wheel force sensor system 19 detected.

Sensor technology measuring the wheel force 19 comprises a longitudinal force sensor, a lateral force sensor and a normal force sensor. The corresponding measured values are sent to the controller 13 supplied, which can thus perform a control of the longitudinal force F _L or the braking or driving torque. Regulation takes place by actuating the clutch 14 , the transmission 15 , the internal combustion engine 16 and / or the brake 17 , About the steering plate 20 it is also possible to determine the steering angle of the wheels and thus to influence cornering.

at braking of the vehicle when cornering, it is possible to on the individual wheels acting braking forces optimal, individual setting for the bike. The braking torques are preferred on the individual wheels set so that the ratio between the horizontal force and the normal force on each wheel is the same.

Taking into account a measured normal force F _{N, i} , the horizontal force can be activated by actuating one of the actuators 14 - 17 be regulated in the desired manner.

1

brake pedal

2

Brake signal transmitter

3

control unit

4

hydraulic unit

5a-5d

bikes

6

brake

7

wheel force measuring sensors

10

accelerator sensor

11

Brake signal transmitter

12

desired torque

13

regulator

14

clutch

15

transmission

16

internal combustion engine

17

brake

18

driving condition

19

wheel force measuring sensors

20

steering actuator

21

Steering wheel angle sensor

22

Driving condition sensor

23

Desired yaw moment and lateral acceleration

F _L

longitudinal force

F _N

normal force

F _Q

lateral force

Claims (10)

Procedure for adjusting the on a wheel ( 5a - 5d ) acting braking or driving torque in motor vehicles, characterized by the following steps: or acceleration request using sensors ( 10 . 11 ), - measuring one on a wheel ( 5a - 5d ) acting longitudinal force (F _L ) by means of a sensor measuring wheel force ( 19 ) and - regulating the longitudinal force (F _L ) or a derived value depending on the driver's request. A method according to claim 1, characterized in that the on a wheel ( 5a - 5d ) normal force (F _N ) by means of a sensor measuring wheel force ( 7 ) is measured and the longitudinal force (F _L ) or the quantity derived from it is regulated as a function of the measured normal force (F _N ). A method according to claim 1, characterized in that the tire lateral force (F _Q ) is measured and a controller ( 3 . 13 ) is supplied. Method according to one of the preceding claims, characterized in that from the sensor system measuring the wheel force ( 7 ) a yaw moment (M _G ) is calculated and a controller ( 3 . 13 ) is supplied as the actual value. Method according to one of the preceding claims, characterized in that the measured longitudinal force (F _L ) is used to calculate a target value of a vehicle dynamics control, such as a target slip or a target yaw moment. Method according to one of the preceding claims, characterized in that the control algorithm of a vehicle dynamics control is changed as a function of the measured longitudinal force (F _L ). Device for adjusting the on a wheel ( 5a - 5d ) acting braking or driving torque in motor vehicles, characterized by - a sensor system ( 10 . 11 ) for measuring a braking or acceleration request specified by the driver, - a sensor system measuring wheel force ( 7 ) for measuring the on the wheel ( 5a - 5d ) acting longitudinal force (F _L ), and - a controller ( 3 . 13 ) to regulate the longitudinal force (F _L ) depending on the driver's request. Device according to claim 7, characterized in that the wheel force measuring sensor system ( 7 ) comprises a sensor for measuring a normal force (F _N ). Apparatus according to claim 8, characterized in that the controller ( 3 . 13 ) regulates the longitudinal force (F _L ) depending on the normal force (F _N ). Device according to one of claims 7 to 9, characterized in that the wheel force measuring sensor system ( 7 ) includes a sensor for measuring the tire lateral force (F _Q ) and the tire lateral force (F _Q ) is taken into account when regulating the longitudinal force (F _L ).