DE102004031653A1 - Automotive steering mechanism has computer system accepting steering corrections under given dynamic conditions - Google Patents

Abstract

An automobile has a primary steering mechanism working in conjunction with a superimposed steering system that imparts corrections in accordance with other parameters e.g. dynamic vehicle parameters. The correction is effected by an electric motor actuator. The superimposed input correction angle is determined by the resultant steering angle. Also claimed is a commensurate computer program.

Description

The The invention relates to a method for steering a vehicle a superposition steering system, in which a driver entered by the steering angle and another Angle (additional steering angle) is determined and at which the entered steering angle by the additional steering angle in accordance with other sizes, in particular dynamic driving parameters, by means of an electric motor are superimposed can.

The The invention also relates to a computer program and a steering system for a vehicle with one on a steering column arranged steering wheel, with a steering gear, one arranged on the steering column Angle of rotation sensor, one above a superposition gearbox on the steering column acting overlay motor, an electric steering actuator, a sensor for measuring the position the steered wheels and with a steering controller.

today Motor vehicles, especially passenger cars, are usually equipped with hydraulic or electro-hydraulic power steering, where a steering wheel mechanically coupled with the steerable vehicle wheels is. The power assistance is constructed such that in the central region of the steering mechanism Actuators, e.g. Hydraulic cylinders are arranged. By one of The force generated by the actuators becomes the operation of the steering mechanism assisted in response to the rotation of the steering wheel. This is the effort reduced by the driver during the steering operation.

Superposition steering are known. They are characterized by being entered by the driver Steering angle if required another steering angle (additional steering angle) superimposed by an actuator can be. There are usually electrical Actuators used, which act on a superposition gear and adjust the additional steering angle largely independent of the driver.

The additional steering angle is controlled by an electronic controller and serves, for example, to increase the stability and agility of the vehicle. After a well-known control concept, as it in the DE 197 51 125 A1 will be described, the steering components of the superimposed steering angle are formed independently of each other.

Of the Invention is based on the object, a method for steering a Vehicle with a superposition steering to provide that works safely and reliably.

des Überlagerungsgetriebes nach Maßgabe eines resultierenden Lenkwinkels des Lenksystems und nach Maßgabe einer Größe ermittelt wird, welche von dem Zusatzlenkwinkel direkt abhängig ist oder den Zusatzlenkwinkel beschreibt.This object is achieved in that a value for a transmission input angle

the superposition gear is determined in accordance with a resulting steering angle of the steering system and in accordance with a size which is directly dependent on the additional steering angle or describes the additional steering angle.

According to the invention, it is provided that a driver request δ _{CMD, DRV} a steering movement for the steering angle control by multiplying the value for the

(53) mit einem aus der einer variablen Lenkübersetzung resultierenden Verstärkungsfaktor ν_δ,ESAS gebildet wird.Transmission input angle

( 53 ) is formed with a resulting from the variable steering ratio gain ν _{δ, ESAS} .

According to the invention, the resulting steering angle of the steering system is a pinion angle of a rack and pinion steering δ _R = δ _sum

A advantageous embodiment of the method according to the invention is that size, which is directly dependent on the additional steering angle or the additional steering angle describes the location or position of a Überlagerungaktuators characterized.

It is provided according to the invention that the size, which characterizes the position or position of a Überlagerungaktuators, the angle of an electronic overlay motor (motor angle φ _Mot ) is.

To A further embodiment of the invention provides that the method is a steering angle control with underlying current or engine torque control an electric motor as overlay actuator having, as specified a comparison between a steering angle feedback and a steering angle reference a desired current or a desired engine torque is generated by the Electric motor introduces the additional steering angle in the steering system.

It is provided according to the invention that the driver's steering request is formed in accordance with a fixed or variable predefinable transmission ratio factor and the transmission ratio factor according to the current driving situation, in particular a detected vehicle longitudinal speed and / or a steering wheel angle ge is selected, and that based on the driver's steering request, a steering angle target value is determined and the steering control is supplied.

It is provided according to the invention that the driver's steering wish in Connection with a translation factor, with which the driver's steering angle acts directly on a steering gear, is superimposed additively with an additional steering angle in conjunction with a second translation and that a superimposed steering angle is determined and fed as an actual value of the steering control.

A advantageous embodiment of the method according to the invention is that a vehicle dynamics control (ESP system) with the steering control interacts and that if the need for a stabilizing Engaged by the vehicle dynamics control is detected an additional driving dynamics dependent Steering angle is determined and is superimposed additively to the driver's steering request.

To A further embodiment of the invention provides that the electric motor according to specification additional sizes with additional a field weakening current is driven, in order to increase the Engine speed without reduction of available engine torque.

Preferably the electric motor becomes additional with a field weakening current activated, if a very direct steering ratio and / or a large target speed required or required.

To A further embodiment of the invention provides that a feedforward control of a desired speed of the electric motor made and that the pilot control value depends on a desired Motor speed of the electric motor is weighted.

It is provided according to the invention, that a pilot control of a Target speed of the electric motor is made, the off an engine speed command and an engine speed command is determined, the engine speed setpoint based on a comparison of a steering angle setpoint with a determined Steering angle feedback is determined and the engine speed default from the temporal Derivation of the steering angle setpoint separated according to signal components, which are due to the driver's steering request and based on the requested ESP correction angle, determined becomes.

It is also provided according to the invention that a pilot control a desired speed of the electric motor is made and in accordance with a request regarding the dynamics and comfort the signal components that are due to the Driver's steering request and due to the requested ESP correction angle be weighted separately from each other.

According to the invention Task solved by a computer program that to carry out a Method according to one of the preceding claims is suitable.

The Task is also solved by a steering system for a vehicle, with one on a steering column arranged steering wheel, with a steering gear, one arranged on the steering column Angle of rotation sensor, one above a superposition gearbox on the steering column acting overlay motor, a sensor for measuring the position of the steered wheels and with a steering controller, at which steering the steering control device means to carry out of the previously described method according to the invention.

Exemplary embodiments of the method according to the invention are shown in FIG. 1 and 7 ) and described below.

It demonstrate:

1 a schematic representation of a superposition steering with a control according to the invention,

2 a block diagram of the overall control concept of the superposition steering,

3 a block diagram of the control concept for engagement of a vehicle dynamics controller,

4 a block diagram of the steering angle control as a general overview concept,

5 a block diagram for a determination of a gain factor,

6 a block diagram of the steering controller in detail, and

7 a block diagram for a determination of a transmission input signal.

The basic structure of an ESC (Electric Steer Assisted Steering) with a control according to the invention is in 1 shown schematically, in which an electric motor driven superposition gear between a torsion bar of a steering valve (torsion bar) and a steering gear or a pinion of a rack steering is arranged.

This is a superposition gear ( 1 ) of a superposition steering ( 2 ) in the split steering column ( 3 ) a conventional power steering ( 4 ) built-in. By means of a motor ( 5 ) can by the superposition gear ( 1 ) an additional or reduced steering angle ( 6 ) on the front wheels ( 7 ) are generated (variable steering ratio).

The steering angle resulting from the variable steering ratio is controlled by a 8th ), which the electric motor ( 5 ) controls. The controller ( 8th ) signals from rotational angle sensors ( 9 . 10 ), by means of which the angle of rotation δ _H ( 11 ) of the steering column ( 3 ) in front of the torsion bar ( 13 ) (Torsionsstab) of the steering valve ( 14 ) and the angle of rotation after the superposition gear ( 1 ), here the angle of rotation δ _R ( 15 ) of the pinion ( 32 ) of the steering gear ( 31 ).

The driver uses a steering wheel ( 29 ) set steering wheel angle δ _H ( 11 ) preferably with a steering wheel angle sensor used as standard in vehicles with a vehicle dynamics control system (ESP systems) ( 9 ) detected. Between steering wheel angle δ _H ( 11 ) and an input angle δ _T ( 12 ) of the superposition gearing ( 1 ) exists depending on the stiffness of the torsion bar ( 13 ) (Torsionsstabs) of the steering valve ( 14 ) and applied by the driver steering torque a differential angle.

In addition to the rotation angle of the pinion ( 32 ) of the steering gear ( 31 ), the "pinion angle" δ _R ( 15 ), with a third sensor ( 33 ) also the motor angle δ _Mot ( 34 ) of the motor ( 5 ) detected. The requirements for accuracy and resolution for the sensors ( 10 . 33 ) when detecting the angle of rotation δ _{R of} the pinion ( 33 ) and the motor angle δ _Mot ( 34 ) are higher than the steering wheel angle sensor ( 9 ).

The hydraulic pressure for the conventional power steering ( 4 ) is controlled by a pump ( 16 ), which here via a drive ( 17 ) with the drive motor ( 18 ) is connected to a vehicle. Advantageously, it is alternatively provided that the pump ( 16 ) is driven by an electronically controlled motor (electric motor) as needed.

Driver assistance is provided by a hydraulic cylinder ( 19 ), which has two chambers ( 20 . 21 ), which by a hydraulic piston ( 22 ), which is connected to a rack ( 23 ) of the steering. For a supply and a discharge from the hydraulic chambers ( 20 . 21 ) for pressure control are hydraulic lines ( 24 . 25 . 26 . 27 ) and a pressure medium reservoir ( 28 ) intended.

In the overlay function of the steering, the driver steering angle δ _H ( 11 ), over the torsion bar ( 13 ) and the transmission ( 1 ) with a translation factor ν1 directly onto the steering gear ( 31 ) acts, according to the desired basic steering function (essentially steering ratio) of the steering controller ( 8th ) an additional steering angle (motor angle φ _Mot ) ( 35 ), which has a transmission ( 36 ) with a second ratio factor ν2 ( 37 ) on the steering gear ( 31 ) acts, superimposed. The overlay results in a certain angle of rotation of the pinion ( 32 ) of the steering gear ( 31 ), ie the "pinion angle" δ _R ( 15 ).

2 shows the overall control concept of the steering angle control for the superposition steering as well as the communication of the steering controller ( 8th ) to a superordinate vehicle dynamics control system ( 38 ) in an overview.

In addition to a desired additional steering angle Δδ _ESP ( 39 ) from the Vehicle Dynamics Control System (ESP) ( 38 ), an ESP request (ESP request bit, ESP request) ( 40 ), which indicates that there is a driving dynamic steering angle intervention. The steering controller ( 8th ) transmits to the vehicle dynamics controller ( 38 ) from driver steering angle ( 11 ) and a request translation ν _{δ, ESAS} ( 52 , please refer 3 ) driver command δ _{CMD, DRV} ( 42 ), the pinion angle δ _R (characterized 15 ) and information regarding the dynamic reserve DR (or DR_pos or DR_neg) available for ESP steering interventions ( 43 ).

The driving dynamics controller ( 38 ) as well as the steering controller ( 8th ) the vehicle speed ( 45 . 46 ), the driving dynamics controller the driving dynamics variables ( 47 ) as well as the steering controller a speed of the engine N _Engine ( 44 ) and an engine torque M _Mot ( 48 ) of the superposition motor ( 5 ) supplied as input variables.

Based on the _engine speed N _Engine ( 44 ) is in the case of a steering of the type "open center", in which no additional steering torque in the straight-ahead position of the wheels ( 7 ), it is decided whether the steering assistance by the power steering is available. If this is not the case, the superposition steering remains or is deactivated and only the direct penetration of the driver onto the steering gear is effective (ratio factor ν1).

From the input quantities, the ESAS steering controller ( 8th ) corresponding Rnsteuersignale ( 66 ) for the superposition motor ( 5 ).

In the 3 a block diagram of the control concept for an intervention of a vehicle dynamics controller is shown.

Driving dynamics steering intervention of the driving dynamics controller ( 38 ) are used as additional steering angle Δδ _ESP ( 39 ), which intervenes to correct the system. In this case, according to the driver's steering angle ( 11 ) and a desired anc translation i _ESAS a gain factor ν _{δ, ESAS} ( 52 ), from which the driver's request δ _{CMD, DRV} ( 42 ). This is with the from the driving dynamics controller ( 38 ) additional steering angle Δδ _ESP ( 39 ) superimposed. The resulting setpoint for the steering angle δ _{R, CMD} ( 49 ) is added to the control loop ( 50 ) for the superposition steering. Thus, the resulting steering angle δ _R = δ _sum ( 15 ), the resulting steering angle ( 15 ) as an input to the control loop ( 50 ) is returned.

By the overlay can according to a recognized driving situation, the driving behavior and the vehicle dynamics are positively influenced, with the driving stability on the one hand as well as the agility of the Vehicle increased can be. In particular, driving dynamics steering interventions realized in order to support the driver in his steering activity.

(53) der Überlagerungslenkung Lenkwinkelregelung aufgrund des resultierenden Lenkwinkels δ_R = δ_Summe (15) (Ritzelwinkels) und des Motorwinkels ϕ_Mot (35) ermittelt wird (vgl. auch 7). 4 shows the control concept of the steering angle control as a general overview. It is essential that for determining the driver's request, first a value for the transmission input angle

( 53 ) of the superposition steering angle control due to the resulting steering angle δ _R = δ _sum ( 15 ) (Pinion angle) and the motor angle φ _Mot ( 35 ) (see also 7 ).

(53) wird dabei nach Maßgabe der konstruktiv festgelegten Getriebegleichung für die Überlagerungslenkung (54) ermittelt (vgl. 7).The value of the transmission input angle

( 53 ) is determined according to the design gear ratio for the superposition steering ( 54 ) (cf. 7 ).

hereby can the driver's request as a partial setpoint of the steering angle control with much higher resolution be determined, which has a strong positive effect on the steering feel.

(53) der Eingangsseite des Überlagerungsgetriebes wird mit dem aus der variablen Lenkübersetzung (65) resultierenden Verstärkungsfaktor ν_δ,ESAS (52) multipliziert (55). Als Ergebnis liegt der Fahrerwunsch δ_CMD,DRV (42) für die Lenkwinkelregelung vor.The calculated in the form described steering angle

( 53 ) of the input side of the superposition gearing is compared with that of the variable steering ratio ( 65 ) resulting gain factor ν _{δ, ESAS} ( 52 multiplied ( 55 ). As a result, the driver's request is δ _{CMD, DRV} ( 42 ) for the steering angle control.

Thus, it is possible, the superposition steering with the standard used as standard steering wheel angle sensor ( 9 ) (an ESP system).

The value of the vehicle dynamics controller ( 38 ) additional steering angle Δδ _ESP ( 39 ) is determined by an interpolation and increase limitation ( 59 ) into a resulting, corrected additional steering angle Δδ _{ESP, IPO} ( 60 ).

Of the Value of the increase limit can according to control engineering aspects chosen and possibly available accordingly Aktuatorstellgeschwindigkeiten be changed.

The resulting setpoint δ _{R, CMD} ( 49 ) for the steering angle control is obtained by adding the additional steering angle Δδ _{ESP, IPO} ( 60 ) and the driver's angle representing steering angle δ _{CMD, DRV} ( 42 ).

Furthermore, due to the corrected additional steering angle Δδ _{ESP, IPO} ( 60 ) a setpoint ω _{CMD, before} ( 62 ) for a speed precontrol of the engine ( 5 ) of the steering ( 61 ) and also the steering angle controller ( 63 ) ( 62 ), which has a resultant engine torque M _{Mot, Cmd} ( 64 ).

Based on the engine torque M _Mot ( 48 ), the resulting gain factor ν _{δ, ESAS} ( 52 ) and the angle of rotation δ _H ( 11 ) of the steering column ( 3 ) the dynamic reserve is calculated ( 67 ). A positive signal DR_pos ( 68 ) or a negative signal DR_neg ( 69 ) generated.

5 shows the determination of the resulting amplification factor ν _{δ, ESAS} ( 52 ) as a component for calculating the steering angle setpoint. A resulting steering ratio i _{δ, ESAS} ( 52 ) results due to the gain factors K1 ( 70 ) and K2 ( 71 ) based on the angle of rotation δ _H ( 11 ) and the vehicle speed V _Kfz ( 46 ) be determined. The amplification factors K1 ( 70 ) and K2 ( 71 ) are multiplicatively linked to the series steering ratio i _{L, series} .

The following applies: i δ, ESAS = δ V / δ H = i L series / (K1 · K2)

The gains K1 (steering wheel angle dependent Share) and K2 (vehicle speed-dependent share) can be free be selected according to driving dynamics or according to driver specifications.

6 shows the components of the steering controller considered here ( 63 ). The control of the motor torque M _Mot or of the torque-generating motor current I _q and the commutation of the motor ( 5 ) (in the case of electronic commutation) is the engine ( 5 ).

Controlled variable of the steering controller ( 63 ) is the resulting, superimposed steering angle (pinion angle) δ _R ( 15 ), which is measured directly. As an internal control variable, the engine speed ω _Mot ( 73 ), which results from the measured motor angle φ _Mot ( 35 ) by differentiation ( 74 ) can be calculated.

The in 6 The steering angle controller shown is a cascade controller of its basic structure. To increase the control loop dynamics, the setpoint ω _{CMD, Vor} ( 62 ) for a speed control of the engine ( 5 ) piloted. Thus, the steering comfort is not affected by the pilot control, especially at slow steering movements, a weighting of the pilot value takes place depending on the desired engine speed. It is advantageous if the in 4 shown calculation of precontrol values ω _{CMD, Vor} ( 62 ) separated according to signal components, which are due to the driver intervention (speed precontrol value driver steering angle ( 60 )) and on the basis of the requested ESP correction angle (speed precontrol value ESP correction angle ( 49 )). Depending on the requirements regarding dynamics and comfort, these two parts can then be weighted separately.

The through the steering angle controller ( 63 ) value is calculated taking into account ( 75 ) the engine speed ω _Mot ( 73 ) and the precontrol value ω _{CMD, Vor} ( 62 ) a speed controller ( 76 ) for generating signals of the resulting motor torque M _{Mot, Cmd} (FIG. 64 ).

(53) als Grundlage für die Bestimmung des Fahrerwunsches δ_CMD,DRV (42) für die Lenkwinkelregelung gezeigt. Nach der Erfindung wird im Fall, wenn kein ESP-Lenkwinkeleingriff vorliegt, nach Maßgabe des resultierenden Lenkwinkels δ_R = δ_Summe (15) (Ritzelwinkels) und des Motorwinkels ϕ_Mot (35) dieser Wert aufgrund der konstruktiv vorgegebenen Übersetzungsfaktoren ν₁ und ν₂ ermittelt.In the 7 becomes the determination of the transmission input signal

( 53 ) as the basis for determining the driver's request δ _{CMD, DRV} ( 42 ) for the steering angle control. According to the invention, in the case where there is no ESP steering angle intervention, in accordance with the resulting steering angle δ _R = δ _sum ( 15 ) (Pinion angle) and the motor angle φ _Mot ( 35 ) determined this value due to the structurally predetermined translation factors ν ₁ and ν ₂ .

In certain operating traps, a higher engine speed may be required than available. In this case, by using a field weakening of the motor ( 5 ) a demand-dependent, short-term increase in the engine speed can be achieved without reducing the available engine torque. However, this is associated with a short-term increase in the total power consumption.

When If necessary, in particular the presence of a very direct steering ratio as well as a big one Target speed on the part of the driver or the vehicle dynamics control system to watch.

Based of the present Actual state of the steering, i. an applied actual engine speed and an applied steering angle value, as well as the desired Target state, i.e. an engine speed command and a steering angle command, and based on the gain factors the steering ratio will over the use of field weakening and the height of the field deceleration.

Is no field weakening of the engine ( 5 ), then the resulting field weakening current I _{d, setpoint} zero (I _{d, setpoint} = 0A).

In addition to torque-generating current 1 _q , the torque control of the electronically commutated motor must additionally adjust the field-weakening current value I _d .

Claims (16)

A method for steering a vehicle with a superposition steering system, in which an input by the driver steering angle and another angle (additional steering angle) is determined and in which the input steering angle by the additional steering angle in accordance with other variables, in particular driving dynamics variables by means of a Überlagerungaktuators, in particular by means of a Electric motor, and can be superimposed on a superposition gear, for the purpose of setting a resulting steering angle, characterized in that a value for a transmission input angle

( 53 ) of the superposition gear is determined in accordance with a resulting steering angle of the steering system and in accordance with a size which is directly dependent on the additional steering angle or describes the additional steering angle. A method according to claim 1, characterized in that a driver command δ _{CMD, DRV} a steering movement for the steering angle control by multiplying the value for the transmission input angle

( 53 ) with one of a variable steering ratio resulting gain factor ν _{δ, ESAS is} formed. A method according to claim 1 or 2, characterized in that a resulting steering angle of the steering system is formed, the pinion angle of a rack and pinion steering δ _R = δ _sum ( 15 ). Method according to one of claims 1 to 3, characterized that size, which of the additional steering angle directly dependent or describes the additional steering angle, the position or position an overlay actuator characterized. A method according to claim 4, characterized in that the size which characterizes the position or position of a Überlagerungaktuators, the angle of an electronic superposition motor (motor angle φ _Mot ( 35 )). Method according to one of claims 1 to 5, characterized that the method includes a steering angle control with subordinate current or engine torque control of an electric motor as Überlagerungsaktuator having, as specified a comparison between a steering angle feedback and a steering angle reference a desired current or a desired engine torque is generated by the Electric motor introduces the additional steering angle in the steering system. Method according to one of claims 1 to 6, characterized that the driver's steering request in accordance with a fixed or variable predefinable gear ratio factor is formed and the transmission ratio factor according to the current one Driving situation, in particular a detected vehicle longitudinal speed and / or a steering wheel turning angle, and that based on the driver's steering request, a steering angle setpoint is determined and the steering control supplied becomes. Method according to one of claims 1 to 7, characterized that the driver's steering wish in conjunction with a translation factor, with the driver's steering angle acts directly on a steering gear, superimposed additively comes with an additional steering angle in conjunction with a second gear ratio and that one superimposed Steering angle is determined and fed as an actual value of the steering control. Method according to one of claims 1 to 8, characterized that a vehicle dynamics control (ESP system) with the steering control interacts and that if the need for a stabilizing Engaged by the vehicle dynamics control is detected an additional driving dynamics dependent Steering angle is determined and superimposed additively to the driver's steering request becomes. Method according to one of claims 1 to 9, characterized that the electric motor in accordance with additional sizes with additional a field weakening current is driven in order to increase the engine speed without reducing the available engine torque. Method according to claim 10, characterized in that that the electric motor in addition with a field weakening current is controlled when a very direct steering ratio and / or a large target speed required or required. Method according to one of claims 1 to 11, characterized that a pilot control of a desired speed of the electric motor is made and that the pilot value depends on a desired Motor speed of the electric motor is weighted. Method according to claim 12, characterized in that that a pilot control of a desired speed of the electric motor made from an engine speed default and a Engine speed setpoint is determined, the engine speed setpoint based on a comparison of a steering angle command value with a determined steering angle actual value is determined and the engine speed default separated from the time derivative of the steering angle command value Signal components, which are due to the driver's steering request and due of the requested ESP correction angle is determined. Method according to one of claims 1 to 13, characterized that made a feedforward control of a desired speed of the electric motor will and according to specification a request regarding the dynamics and comfort the signal components that are due the driver's steering request and due to the requested ESP correction angle be weighted separately from each other. Computer program, characterized in that it to carry out a method according to any one of the preceding claims suitable is. Steering for a vehicle with a steering column arranged on a steering wheel, with a steering gear, arranged on the steering column rotation angle sensor, acting on a superposition gear on the steering column overlay motor, a sensor for measuring the position of the steered wheels and with a steering control unit, characterized characterized in that the steering control device comprises means for carrying out the method according to any one of the preceding claims.