DE4408747A1 - Vehicle control system - Google Patents

Abstract

The invention relates to a vehicle control system for travelling through bends, the vehicle being equipped with a steering system for the rear wheels which control the rear left-hand and right-hand drive wheels when going round a bend, this taking place by means of a steering angle which is determined in accordance with the specific steering angle determination parameters and a drive force distribution system which distributes the drive force like an engine output torque, this distribution between rear left-hand and right-hand drive wheels when going round a bend taking place with a distribution rate which is fixed in accordance with specific distribution determination parameters. The steering system for the rear wheels and the distribution system of the drive force are monitored in such a way that a contribution is made to the cornering of the vehicle with contribution rates which vary in accordance with specific control parameters such as the speed of the vehicle and an engine output torque or the longitudinal acceleration of the vehicle.

Description

The invention relates to a control system for cornering of a vehicle according to the preamble of claim 1. In particular, the invention relates to a vehicle tax system with a distribution system for the drive force on the left and right wheels and with a len system for the rear wheels.

There are traditionally steering systems for the rear actual wheels and distribution systems for the drive force on the left and right areas, the latter the driving force on the left and right rear Distribute wheels, so a facility that actively greed-mo elements without steering the front-wheel drive during a cure ven trips generated.

Such a steering system for the rear wheels sets a yaw rate or ratio as the target and steers the rear wheels so that it is current Develop or get yaw rate that meets the target Yaw rate reached. This type of steering system the back actual wheels is for example from the Japanese patent Application No. 1-262268 known. Furthermore creates a Distribution system for driving the left and right wheels a desired yaw moment by control  the amount of torque that the lin ken and right rear wheels through a clutch each of the drive shafts that have a variable torque carry allowed, is transferred. Such a distribution The system of motive power is, for example, from the yes Panic Patent Application No. 4-68167 known.

As is well known to those skilled in the art there is, among other things, for the grip of a tire one by the friction between the tread of a Force applied to the tire and road surface stands, a limit value, so that a transverse movement of the drive stuff is difficult to produce, even if it is a steering operation during a sudden acceleration or a sudden braking maneuver is performed. If vice versa almost all of the adhesive force exited as a shear force is brought, that is as a curve or sides managerial force, the shear force is reduced when a Driving force or a braking force occurs so that a Slipping or slipping of the tires is caused.

When considering such movements of the vehicle as shown in Fig. 7, it can be imagined that the frictional force generated between the surface of the road and the tread of a tire is determined and generated by force vectors which have a certain length in all directions. The tips of the vectors form a circle, which is referred to as the "circle of friction". When splitting or decomposing the vector of the adhesive force, which points in this "circle of friction" in a certain direction, into longitudinal and lateral force components, it is possible to find the balance between a driving force or a braking force and a cornering force.

A point can be turned around in which a line is perpendicular to the vector of a certain cornering force "Circle of Friction" cuts out to be used find out how big a driving force or a brake must be force in which the vector of the adhesive force under egg effect of the certain cornering force exceeded will. In other words, taking into account such a "circle of friction" say that if a high driving force on the rear drive wheels is transmitted, generating a large corner guide force is impossible, even if the rear wheels controlled by a steering system for the rear wheels be steered or steered.

On the other hand, it can also be said that if one high cornering force is generated, it is impossible high driving force on one of the rear wheels through the distribution system of the driving force. From these aspects it can be seen that it is inevitable is that the split system for the driving force and the rear steering system as a device conditions for the active generation of a yaw moment on the drive serve their own command specialties and mistakes have areas. That is, generate in their error areas both systems, namely the distribution system for the Driving force and the steering system for the rear Wheels, not a greed moment quickly enough, so this too leads to poor cornering characteristics of the vehicle.

It is therefore an object of the invention to drive provide control system that a desired yaw Moment during a cornering of the vehicle through a Community control of the backward steering system wheels and the distribution system for the driving force to the left and right side.  

This object is achieved by the features of Claim 1 solved.

This task is made special by a control system for cures ven trips of a vehicle solved that with a steering is equipped for the rear wheels, the left and right rear drive wheels controls during cornering, using a Steering angle, which corresponds to a special steering win kel determination parameters and a distribution system of Driving force is determined which is the driving force as a Output torque of the machine divided between the left and right rear drive wheels during a cure venfahrt, with a distribution ratio accordingly zial distribution determination parameters is set. This steering device for the rear wheels and the distribution device for the driving force will be so controlled to when turning the vehicle with contribution rates that contribute according to special tax parameters ter, such as the vehicle speed, and the Output torque of the machine or the acceleration of the Vehicle in the longitudinal direction are variable.

The contribution rate of the distribution facility is special the driving force with an increase in vehicle speed reduced, and the contribution rate of steering Direction for the rear wheels is increased the vehicle speed increases. Furthermore, the case Wear rate of the distribution device for the driving force with an increase in the output torque of the machine increased, and the contribution rate of the steering body of the rear wheels will turn with an increase in output moment of the machine.  

On the other hand, the contribution rate of the distribution facility tion for the driving force with an increase in the acceleration inclination of the vehicle can be increased in the longitudinal direction, and the contribution rate of the steering device for the reverse term wheels can increase the acceleration of the Vehicle can be reduced in the longitudinal direction.

With the vehicle control system to manage curves is driven when a small amount of driving force, that is, a small output torque from the machine the rear drive wheels are transmitted like this clear from the "circle of friction" described above results in a great cornering force necessary yaw moment mainly by directing the rear drive wheels by means of the steering system of the rear wheels generated quickly. On the other hand, even then when there is a high driving force on the rear approach drive wheels is transmitted, hardly a large screen leadership through the steering of the rear wheels using the steering system for the rear Wheels generated as is also clear from the previous described "circle of friction" becomes clear, so that a Yaw moment by assigning a high driving force one each of the rear wheels using the Distribution system for the driving force to the left and right wheels is assigned.

In other words, the vehicle control system realizes ge According to the invention, by the concept of the "Circle of Rei exercise "is effectively used that during the cure the left and right divisions of a vehicle Power transmission and steering system the rear wheels are complementary to each other if one of the respective systems during the coping cornering reacted adversely or incorrectly.  

Complementary handling of a curve using the left and right split system for the driving force and the steering system for the rear wheels a necessary greed moment in every kind and phase of one Turning the vehicle.

The above and other goals, aspects and Features of the invention will be apparent from the following Description with reference to preferred embodiment examples of the invention more clearly understandable if this taking into account the attached drawings. The invention will be more schematic based on the following Drawings and processes explained in more detail. Show it:

Fig. 1 is a schematic representation of a vehicle equipped with a vehicle control system according to a preferred embodiment of the inven tion;

Fig. 2 shows a flowchart showing a general sequence or a main program for a microcomputer that controls the operation of a vehicle control system;

Figs. 3A and 3B show a flow chart showing a determination result of a torque distribution or a showing subroutine for the microcomputer;

Fig. 4 shows a flowchart showing a determination sequence for the steering angle of a rear wheel drive wheel or a subroutine for the microcomputer;

Fig. 5 is a flowchart showing a determination rate for a contribution rate or a subroutine for the microcomputer using the output torque of a machine as a determination parameter;

Fig. 6 is a flowchart showing a determination sequence of a distribution rate or a subroutine for the microcomputer using the longitudinal acceleration as a determination parameter, and

Fig. 7 is an explanatory diagram of the "circle of friction".

Referring to the drawings in detail and in particular to FIG. 1, which shows the overall structure of a four-wheel drive vehicle, such as a front engine front drive vehicle (FF), having a vehicle control system according to a preferred embodiment the invention is equipped, this figure shows a drive or power unit 1 , the drive shaft be operatively with a front and rear Radan drive shaft 4 and 5 via a pair of flat gears 2 and 3 , so that the output torque can be carried on this. The drive of the left and right front derrades 8 L and 8 R is realized in that the left and right front wheel drive shaft 7 L and 7 R are connected to the front end of the front wheel drive shaft 4 via a differential gear 6 . The drive shaft 5 for the rear wheels has a hydraulically operated main clutch 9 .

The rear end of the drive shaft 5 for the rear wheels is connected to the left and right drive shafts 13 L and 13 R of the rear wheels through a bevel gear pair 11 and 12 , thereby the left and right rear wheels 14 L and 14 R to be able to drive.

The drive shafts 13 L and 13 R for the rear wheels are equipped with hydraulically operated clutches 15 L and 15 R.

A front wheel steering mechanism 16 includes a steering wheel 17 , a rack and pinion mechanism 18 which converts the rotation of the steering wheel into a linear motion, and tie rods 19 L and 19 R which control the linear motion of the rack and pinion mechanism 18 on the left and right front wheels 8 L and 8 Transfer R so that the wheels can be steered to the left or right. On the other hand, there is a steering mechanism 20 for the rear wheels, which has a maneuvering rod 22 for the rear wheels, which is moved by a power cylinder 21 . Furthermore, tie rods 23 L and 23 R are present, which transmits the movement of the maneuvering rod 22 of the rear wheels to the left and right rear wheels 14 L and 14 R, so that the Len tion of these wheels to the left or right is possible.

A hydraulic pressure, which is given to the corresponding hy metallic clutches 9 , 15 L and 15 R from a hydraulic pressure source (not shown) is regulated by means of solenoid valves or solenoid valves 24 , 25 L and 25 R, the effect of which is controlled by means of control signals from a control device 30 . The control device 30 is part of a microcomputer, the torque transmission to the left and right rear wheels 14 L and 14 R being regulated accordingly.

The controller 30 receives various signals such as wheel speed signals ω _FL and ω _{FR of} the left and right front wheels 8 L and 8 R from the corresponding wheel speed sensors 31 L and 31 R. Furthermore, the controller receives wheel speed signals ω _RL and ω _{RR of} the left and right rear wheels 14 L and 14 R from the corresponding wheel speed sensors 32 L and 32 R. Furthermore signals of a steering angle R and a steering angle speed dR / dt of the steering wheel from a steering angle sensor 33 , a throttle -Opening signal TVO of a throttle valve 10 from a throttle valve sensor 34 and a longitudinal acceleration signal G of the vehicle from an acceleration sensor 35 , the operations of the steering mechanism 20 for the rear wheels and the solenoid valves 24 , 25 L and 25 R being based of these received signals can be checked and controlled.

The mode of operation of the vehicle control system illustrated in FIG. 1 is best understood by studying FIGS. 2-5, which are flowcharts showing various programs and subroutines for the controller 30 microcomputer. Programming a computer is a specialist activity that is well known and understood in the relevant area. The following description is provided in order to enable a programmer who has the usual knowledge in this area to create a suitable program for the microcomputer of the controller 30 . The special details of each such program naturally depend on the structure of the specially selected computer.

Referring to FIG. 2, which is a flowchart of the main routine of the main or usual sequence for the microcomputer of the controller 30 , the sequence starts and the control goes directly to step S1, in which various constants and markings or notices or commands are initialized will. Subsequently, in step S2, the amount of operation of the clutches 9 , 15 L and 15 R for torque distribution is determined, and in step S3, the angle of steering of the rear wheels is determined. Then, in step S4, the distribution ratios of the steering angle of the rear wheels and the clutch actions for torque distribution are set. These steps S2-S4 are repeated.

With reference to FIGS. 3A and 3B, which show a sequence diagram for the subroutine or the subroutine for determining the torque distribution, it is clear that in the first step S11 in FIG. 3A the various signals ω _FL , ω _FR , ω _RL , ω _RR , R, dR / dt and TVO are read in and the speed of the vehicle is set or fixed which corresponds to the minimum of the respective wheel speeds Ω _FL , ω _FR , ω _RL and ω _RR .

In step S12, the speed difference Δωx between front and rear wheels is calculated. This speed difference between front and rear wheels is defined as the speed that is between the sum of the speeds of the left and right front wheels and the sum of the speeds of the left and right rear wheels. Then, in step S13, if there is actually any speed difference between the front and rear wheels, a control amount Tcx of the main clutch 9 on a clutch control list is read in accordance with the speed difference Δωx. In this example, since this four-wheel drive vehicle is a front-engine front-wheel drive type, the turning speeds of the front wheels are basically larger than the turning speeds of the rear wheels.

The difference Δωy subsequently follows in step S14 calculate between left and right wheel speed net. This difference between the left and right wheel speed is defined as the difference between the sum of the speeds of the front and rear left wheels and the sum of the speeds of the front and rear right wheels.

Then, in step S15, if there is actually any speed difference between the left and right wheels, the control amount Tcy of the main clutch 9 is read from a clutch control list corresponding to the absolute value of the speed difference Δωy between the left and right wheels. Control then proceeds to step S16 in FIG. 3B.

In step S16 in FIG. 3B, the control amount Tcv of the main clutch 9 is determined from a clutch control list according to the vehicle speed V and the power output represented by the throttle valve opening TVO. Subsequently, in step S17, the left and right distribution ratios KL and KR of the drive torque, which experience has determined during cornering, are determined from a distribution ratio list. In this case, if the steering angle R is neutral N, the distribution ratio of the drive torque of the left and right wheels is KL: KR 0.5: 0.5 (KL = KR), regardless of the direction of the bends. Further, after allocation of the maximum values of TCX, Tcy and Tcv to the magnitude of the torque Tc, which is transmitted to the rear wheels in step S18, the basic amount of the torque Tcl and Tcr, the left to the ent speaking and right rear wheels 14 L and 14 R are obtained by multiplying the transmission amount of the torque Tc by coefficients KL and KR associated with the left and right rear wheels 14 L and 14 R, respectively, in step S19.

Referring to Fig. 4, which is a flowchart of the contents of the subroutine for determining the steering angle of the rear wheels, it is clear that the subroutine starts and the control goes directly to step S21, in which a steering angle R of the steering wheel 17 and the Vehicle speed V can be read.

After determining a steering ratio KR with a view to the vehicle speed V from a steering ratio list in the following step S22, a basic steering angle 8 R of the rear wheels is calculated by multiplying the steering angle R by the steering ratio KR in step S23.

Referring to FIG. 5, which shows a flowchart of a subroutine for determining the contribution rate, a throttle opening TVO and a vehicle speed V are read in the first step S31. Then, in step S32, the basic contribution rate of the torque distribution W _T and the basic contribution rate of the steering W _{S of} the rear drive wheels are determined from a distribution ratio map corresponding to the throttle valve opening TVO. In this case, as is clear from the contribution rate list shown in step S32, it is clear that the total or the sum of the basic contribution rate W _{T of} the torque distribution and the basic contribution rate W _{S of} the steering of the rear wheels is constant , and "1" is. In other words, the base contribution rate of the torque distribution system W _T to a curve increases with an increase in the drive torque of the machine, which is represented by the throttle valve opening TVO, and on the other hand, the base contribution rate of the steering system W _S becomes rear wheels for cornering increases with a reduction in drive torque.

Accordingly, after determining the correction coefficient K _v in accordance with the vehicle speed V from a correction coefficient list in step S33, the effective contribution rate W _{TF of} the torque split and the effective steering contribution W _{SF of} the rear wheels are calculated in step S34. Specifically, the effective contribution rate W _{TF of} the torque split is obtained by subtracting the correction coefficient K _V from the base contribution rate of the torque split W _T.

On the other hand, the effective rear wheel steering distribution rate W _{SF is} obtained by adding the correction coefficient K _v to the basic rear wheel steering distribution rate W _s . As a result of this correction, the contribution rate of the torque distribution is reduced with an increase in the vehicle speed, while the steering contribution rate for the rear wheels is increased when an increase in the vehicle speed occurs. Thereafter, in step S35, the effective torque division contributions T _CLF and T _CRF are calculated by taking the basic transmission amounts of the torque T _CL and T _CR , which are obtained in step S19 of the subroutine for determining the distribution of the torque shown in FIG. 3, be multiplied by the effective contribution rate W _{TF of} the torque distribution, and the effective steering angle of the rear wheels R _RF is calculated by using the basic steering angle R _{R of} the rear wheels as shown in step S23 of the subroutine in FIG Determination of the steering angle of the rear wheels is obtained is multiplied by the effective contribution rate W _{SF of} the steering of the rear wheels. In step S36, the controller 30 generates control signals representative of these effective amounts of the torque _split T _CLF and T _CRF , and the effective steering angle RRF of the rear wheels to the corresponding solenoid valves 25 L and 25 R and the power cylinder 21 .

It will be seen that the base contribution rate W _{T of} the torque split and the base contribution rate W _S for the steering of the rear wheels can be determined on the basis of the acceleration G _{x of} the vehicle in the longitudinal direction instead of the throttle valve opening TVO. In this case, as shown in Fig. 6 in step S31 'ge, a vehicle speed V and the acceleration Gx are read in the longitudinal direction, and in step S32' who the basic contribution rate W _{T of} the torque distribution and the basic contribution rate W _{S determines} the steering of the rear wheels from the distribution ratio list in accordance with the acceleration in the longitudinal direction Gx. The following steps are the same as those from step S33 to step S36 in Fig. 5. In this way, the base contribution rate W _{T of} the torque split is increased with an increase in the acceleration in the longitudinal direction Gx, and the base contribution rate W _S the steering of the rear wheels is increased with a reduction or reduction in the acceleration Gx in the longitudinal direction.

It should be noted that although the invention in one refer to a preferred embodiment game has been described, various other embodiments Forms and variants are recognizable for the specialist, falling within the scope of this invention.

Claims (8)

1. Control system for a vehicle for cornering, with a steering device for the rear wheels for steering the left and right rear drive wheels on the basis of a steering angle which is determined in accordance with specific steering angle determination parameters,
with a driving force distribution device for distributing a driving force to the left and right rear drive wheels during cornering with a distribution ratio that is determined according to specific distribution determination parameters,
and with
a control device for controlling the relative contributions of the steering device of the rear wheels and the driving force distribution device to a cornering of the vehicle as a function of predetermined variable parameters. 2. Control system according to claim 1, characterized, that the control of the control device with the driving tool speed varies.   3. Control system according to one of claims 1 to 2, characterized, that the control of the control device the relative Contribution of the driving force distribution device with Zu reduced the vehicle speed and the right latent contribution of the steering device of the rear Wheels increased with increasing vehicle speed. 4. Control device according to one of claims 1 to 3, characterized, that the control of the control device accordingly a torque output of the machine is different. 5. Control system according to one of claims 1 to 4, characterized, that the control of the control device the relative Contribution of the driving force distribution device with egg ner increase in the torque output of the machine increases and the relative contribution of the steering device of the backwards wheels with an increase in the torque output of the dimensions seem reduced. 6. Control system according to one of claims 1 to 5, characterized, that the output torque of the machine is dependent to a throttle opening of a throttle valve Machine is determined.   7. Control system according to one of claims 1 to 6, characterized, that the control system is dependent acceleration of the vehicle in the longitudinal direction varies. 8. Control system according to one of claims 1 to 7, characterized, that the control system controls the relative case drive distribution system with a Zu increased the longitudinal acceleration of the vehicle and the relative contribution rate of the steering body of the rear wheels with increasing longitudinal acceleration of the vehicle reduced.