DE10247975B4 - A method of operating a steering, a computer program, a controller and a steering system for a vehicle - Google Patents

Abstract

A method for operating a steering system for a vehicle with a steering wheel rotation angle sensor (11) for detecting the steering movements of a steering wheel (1), with a pinion rotation angle sensor (19) for detecting the rotation (δ pinion) of a pinion (7) driven by the steering wheel (1) and with a first servomotor rotation angle sensor (17) for detecting the positioning movement (δSM) of a first servomotor, characterized by the following process step: - checking the signals (δpinion, δLR, δSM) generated by the pinion rotation angle sensor (19), steering wheel rotation angle sensor (11) and first servomotor rotation angle sensor (17) ) by calculating a total steering angle (δLW, total) from the signal (δSM) of the servomotor rotation angle sensor (17) and the signal (δLR) of the steering wheel rotation angle sensor (11) according to the following formula: δLW, total = i1 × δLR + i2 × δSM, forming a Angular difference (δDiff) from the total steering angle (δLW, total) and pinion angle (δRitzel) and output of an error signal if the angle difference (δDiff) is a given exceeds the specified limit value (S). With: i1: transmission ratio between the steering wheel rotation angle sensor (11) and pinion rotation angle sensor (19) and i2: transmission ratio between the first servo motor rotation angle sensor (17) and pinion rotation angle sensor (19)

Description

State of the art

The invention relates to a method for operating a steering system according to the preamble of claim 1 or claim 2, a computer program, a control device and a steering system according to the preamble of claim 11.

In this steering, hereinafter referred to as active steering, there is always a mechanical connection between the steering wheel and the steered wheels, in contrast to steer-by-wire steering systems. With an active steering on the one hand the comfort for the driver of the vehicle to be increased by, for example, a power assistance is provided or the gear ratio of the steering speed and / or steering angle is changed dependent. On the other hand, it is possible with an active steering, to increase the active safety of the vehicle by a dynamic driving stability control.

Both can be achieved by a superposition gear with a preferably electric servomotor. Due to the superposition gearing, it is possible to add a superposition angle to the steering angle predetermined by the driver of the vehicle via the steering wheel, so that, for example, the steering angle of the steered wheels is increased when parking in addition to the steering angle predetermined by the driver of the vehicle. If the vehicle should oversteer, the steering angle set by the driver of the vehicle may be reduced by the superposition gear and the servo motor so as to stabilize the vehicle.

Of course, active steering as well as all other steering systems of vehicles are subject to the highest safety requirements. Therefore, it is necessary to detect any errors that may occur during active steering as soon as possible and clearly, so that these errors do not endanger the vehicle occupants.

From the DE 100 12 133 A1 is a method for plausibility of the rotation angle sensors of an active steering a motor vehicle known. The plausibility check is based on a dynamic steering model, which is complex to implement and requires a lot of computation time in operation.

The object of the invention is that a total steering angle of rotation is calculated from the signal of the Stellmotordrehwinkelsensors and the signal of the steering wheel rotation angle sensor.

The object is achieved by a method having the features of claim 1 or of claim 2, by a computer program having the features of claim 8, by a control device having the features of claim 10 and a steering having the features of claim 11 Further developments emerge from the subclaims.

Advantages of the invention

In the claimed method, the steering angle of the steering wheel is detected with the steering wheel rotation angle sensor detects the rotation angle of the pinion of the steering gear with the pinion rotation angle sensor, detects the rotation angle of the first servo motor of the superposition gear with the first actuator rotor angle sensor, the first servomotor driven in response to external inputs and the plausibility of checked by the pinion rotation angle sensor signals by comparing with the signals generated by the steering wheel rotation sensor and the first actuator rotor angle sensor signals.

The plausibility check of the signals from the pinion rotation angle sensors, the steering wheel rotation angle sensor and the first actuator rotor angle sensor makes it possible to check without additional effort whether all three sensors are working properly and whether the active steering works as desired.

δ_LW,GESAMT

Gesamtlenkwinkel

δ_LR

Lenkradwinkel

δ_SM

Stellmotorwinkel

i₁:

erstes Übersetzungsverhältnis

i₂:

zweites Übersetzungsverhältnis.

Of course, when comparing the signals generated by the steering wheel rotation angle sensor and the first servo motor rotation angle sensor with the signals generated by the pinion rotation angle sensor, the gear ratios between the steering wheel rotation angle sensor, the pinion rotation angle sensor, and the first actuator rotation angle sensor are to be considered. This is done by calculating a total steering angle of rotation from the signal of the actuator rotor angle sensor and the signal of the steering wheel angle sensor according to the following formula: δ _{LW, total} = i ₁ × δ _LR + i ₂ × δ _SM With:

δ _{LW, TOTAL}

Total steering angle

δ _LR

steering wheel angle

δ _SM

Servomotor angle

i ₁ :

first gear ratio

i ₂ :

second gear ratio.

The plausibility check is particularly simple if a difference is formed from the total steering angle δ _{LW, TOTAL} and the _pinion angle δ _pinion measured by the pinion angle sensor, and a faulty behavior of the active steering, in particular of the sensors involved, is concluded when the difference exceeds a predetermined limit.

To improve the detection of malfunctions of the active steering, it has proven to be advantageous if the error signal is output only when the difference exceeds a predetermined limit during a certain time interval. This can be very short-term deviations of the total steering angle of the pinion angle, which are not due to a malfunction of the active steering are hidden. Such very short-term deviations can be caused, for example, by different sampling rates of the different rotation angle sensors.

The plausibility check according to the invention can be further improved if the limit value, at the exceeding of which an error signal is output, is determined as a function of the driving speed and / or the rotational speed of the steering wheel. There is a relationship between the rotational speed of the steering wheel and the torque transmitted to the steering wheel by the steering wheel. This relationship can be exploited to close without torque measurement from the rotational speed of the steering wheel on the transmitted torque from the steering wheel.

It is particularly advantageous if the limit value is determined as a function of the torque transmitted between the steering wheel and the steering column, since the torsion of the steering column and any existing play in the transmission of the rotational movement from the steering wheel to the steering gear is highly dependent on the torque. This makes it possible to minimize the limit depending on the operating state of the active steering and thus detect errors faster and with greater reliability. As a result, the potential risk to the occupants of the vehicle equipped with the active steering system according to the invention is reduced.

The advantages of the invention are also with a steering system for a vehicle with a steering wheel, a steering column and a steering gear for implementing the steering movements of the steering wheel in positioning movements of the steered wheels of the vehicle, with a superposition gear for superimposing the adjusting movement of a first servo motor on the steering movements, with a Steering wheel rotation angle sensor for detecting the steering movements of the steering wheel, with a pinion rotation angle sensor for detecting the rotational movement of a steering wheel driven by the steering gear of the steering gear, with a first actuator rotor angle sensor for detecting the actuating movement of the first servomotor and with a control unit, achieved in that the control unit for performing one of the above described method is suitable.

Further advantages of the invention are the following drawings, the description and the claims can be removed.

Show it:

1 a simplified representation of an active steering according to the invention, and

2 a flowchart of an embodiment of the method according to the invention.

Description of the embodiments

In 1 is an active steering shown schematically. The driver's wish is via a steering wheel on a three-part steering column 3 transferred, which in turn a steering gear 5 drives. The steering gear 5 is at the in 1 illustrated embodiment designed as a rack and pinion steering gear. From the rack and pinion steering gear is in 1 just a pinion 7 , which cooperates with a rack, not shown, shown. The steering gear 5 sets the rotational movement of the steering wheel 1 in a substantially rectilinear motion of tie rods 9 at which are in operative connection with the steered wheels of a vehicle, not shown.

In the upper part 3a the steering column 3 is a steering wheel turning angle sensor 11 arranged, which detects the driver's steering request or the steering wheel rotation angle δ _LR . In the lower part 3c the steering column 3 is a superposition gearbox 13 available. That in its entirety with 13 designated superposition gear includes a first servomotor 15 and a first actuator rotor angle sensor 17 ,

The superposition gearbox 13 allows the angle of rotation of the steering wheel 1 add or subtract an additional angle so that the rotation angle of the pinion 7 , which is driven by an output shaft (not shown) of the superposition gear, greater than, equal to or less than the rotation angle of the steering wheel 1 can be. The superimposition of the rotational movements of the steering wheel 1 and first servomotor 15 can for example have an in 1 not shown in detail planetary gear.

For detecting the angle of rotation of the pinion 7 is a pinion rotation angle sensor 19 on the pinion 7 intended. The steering wheel rotation angle sensor 11 , the first servomotor rotation angle sensor 17 and the pinion rotation angle sensor 19 are via signal lines 21 with a control unit 23 connected. The same applies to the first servomotor 15 , from the control unit 23 via a signal line 21 is controllable.

Because of the coupling between the steering wheel 1 and pinion 7 on the one hand and the first servomotor 15 and pinion 7 On the other hand, the rotation angle of the pinion 7 from the angle of rotation of the steering wheel 1 and the angle of rotation of the first servomotor 15 be calculated taking into account the gear ratios. This fact makes use of the inventive method to determine by a plausibility check, if the said sensors 11 . 17 and 19 as well as the remaining active steering work properly.

Here, a total steering angle is δ _{LW, TOTAL} calculated, wherein in the calculation as input values the signal _LR δ of the steering wheel rotational angle sensor 11 and enter the signal δ _{SM of} the first actuator rotor angle sensor. In addition, the gear ratios i ₁ and i ₂ between the steering wheel 1 and pinion 7 as well as servomotor 15 and steering wheel 7 considered.

When the calculated total steering angle δ _{LW, TOTAL} deviates by a predetermined differential angle δ _Diff from a signal δ _{pinion of} the _pinion rotation angle sensor, which is greater than a predetermined limit value S, becomes an error in the active steering, in particular in the said sensors 11 . 17 and 19 , suspected and an error signal from the controller 23 output. This error signal can, for example, cause the illumination of a warning lamp on the dashboard of the vehicle or trigger any other indication to the driver of the vehicle. Additionally or alternatively, the operating mode of the active steering can also be changed. For example, can be switched to a runflat mode by only the most necessary functions required for the function of the steering functions are provided, in which case the comfort of the steering suffers losses.

To increase the safety of the active steering can be parallel to the first servomotor 15 and the first actuator rotation angle sensor 17 a second servomotor 25 with a second actuator rotor angle sensor 27 be provided. Thus, the servo motor and the associated rotation angle sensor are redundant, which further increases the reliability of the electronic active steering system.

2 shows the flow of the claimed method for operating an active steering in diagram form. In a first step 31 the active steering is put into operation. This means that the control unit 23 is initialized and checked, whether by all sensors, in particular by the sensors 11 . 17 and 19 , Signals are present. In addition, it is checked whether in the control unit 23 further input signals, in 1 through the arrow 29 indicated, present. The other signals 29 can be, for example, the speed of the vehicle, its yaw rate and more. With the help of these signals and by the above-mentioned rotation angle sensors 11 . 17 and 19 generated signals becomes the active steering from the control unit 23 controlled.

In a second step 33 becomes the steering angle δ _{LR of} the steering wheel 1 with the steering wheel turning angle sensor 11 detected, the rotation angle δ _{pinion of} the pinion 7 of the steering gear 5 with the pinion rotation angle sensor 19 detected, the rotation angle δ _{SM of} the first servomotor 15 of the superposition gearbox 13 with the first actuator rotor angle sensor 17 captured and the first servomotor 15 depending on further external input variables 29 driven.

In a third step 35 is the plausibility of the pinion rotation angle sensor 19 generated signals δ _pinion by comparing with the steering wheel rotation angle sensor 11 and first actuator rotor angle sensor 17 generated signals δ _LR and δ _SM checked. This is done taking into account the gear ratios between steering wheel angle sensor 11 , Pinion angle sensor 19 and first actuator rotor angle sensor, for example, in the following manner:
First, a total steering _angle δ _{RW, total} of the signal δ _{SM of} the actuator rotor angle sensor 17 and the signal δ _{LR of} the steering wheel rotation angle sensor 11 according to the following formula: δ _{LW, total} = i ₁ × δ _LR + i ₂ × δ _SM

Thereafter, an angular difference δ _Diff of the total steering angle and the pinion rotation angle sensor 19 measured pinion angle δ _pinion formed. In a further step 37 is compared, whether the angular difference δ _diff exceeds a predetermined threshold value S (step 37 ).

If this is the case, an error signal is output. This is in 2 through the step 39 indicated. If this test is negative, the claimed active steering is OK and the process jumps back before the second step 33 ,

The method according to the invention is further improved if an error signal is output only if the angular difference δ _Diff exceeds the predetermined limit value S during the duration of a predetermined time interval Δt. By this measure, short-term deviations that, for example, from different sampling rates of the rotation angle sensors 11 . 17 and 19 can be filtered out.

It has also proved to be advantageous if the limit value S is set as a function of the torque transmitted between the steering wheel and the steering column, since the torsion in the steering column 3 and any existing, albeit unwanted, play in the individual sections of the steering column 3 connecting joints. As a result, the limit S can be minimized so that any errors that occur are detected as quickly as possible.

If no detection of the between steering wheel 1 and steering column 3 transmitted torque is present, alternatively, the limit value S as a function of the vehicle speed and / or the rotational speed of the steering wheel 1 be determined. This can be done, as in the aforementioned embodiment, by storing such limits in curves or maps.

Claims (11)

Method for operating a steering for a vehicle with a steering wheel rotation angle sensor ( 11 ) for detecting the steering movements of a steering wheel ( 1 ), with a pinion rotation angle sensor ( 19 ) for detecting the rotational movement (δ _pinion ) of the steering wheel ( 1 ) driven pinion ( 7 ) and with a first actuator rotor angle sensor ( 17 ) (For detecting the setting movement δ _SM) of a first servo motor, characterized by the following step: - checking (of pinion rotation angle sensor 19 ), Steering wheel rotation angle sensor ( 11 ) and first actuator rotor angle sensor ( 17 ) generated signals (δ _pinion , δ _LR , δ _SM )) by calculating a total steering _angle (δ _{LW, total} ) from the signal (δ _SM ) of the Stellmotordrehwinkelsensors ( 17 ) and the signal (δ _LR ) of the steering wheel rotation angle sensor ( 11 ) according to the following formula: δ _{LW, total} = ₁ i × δ _LR + i ₂ × δ _SM, Forming an angular difference (δ _Diff ) from total steering angle (δ _{LW, total} ) and pinion angle (δ _pinion ) and outputting an error signal when the angular difference (δ _Diff ) exceeds a predetermined limit value (S). With: i ₁ : Gear ratio between steering wheel angle sensor ( 11 ) and pinion angle sensor ( 19 ) and i ₂ : gear ratio between first actuator rotor angle sensor ( 17 ) and pinion angle sensor ( 19 ) Method for operating a steering system for a vehicle with a steering wheel ( 1 ), a steering column ( 3 ) and a steering gear ( 5 ) for implementing the steering movements (δ _LR ) of the steering wheel ( 1 ) in positioning movements of the steered wheels of the vehicle, with a superposition gear ( 13 ) for superposition of the actuating movement of a first servomotor ( 15 ) to the steering movements, with a steering wheel rotation angle sensor ( 11 ) for detecting the steering movements of the steering wheel ( 1 ), with a pinion rotation angle sensor ( 19 ) (For detecting the rotational movement δ _pinion) of a (the steering wheel 1 ) driven pinion ( 7 ) of the steering gear ( 5 ), with a first actuator rotor angle sensor ( 17 ) for detecting the actuating movement (δ _SM ) of the first servomotor ( 15 ), with a control unit ( 23 ) for evaluating the steering wheel angle sensor ( 11 ), Pinion angle sensor ( 19 ) and first actuator rotor angle sensor ( 17 ) generated signals (δ _LR , δ _pinion , δ _SM ) and for driving the first servomotor ( 15 ), characterized by the following method step: - checking the pinion rotation angle sensor ( 19 ), Steering wheel rotation angle sensor ( 11 ) and first actuator rotor angle sensor ( 17 ) Generated signals (δ _pinion, δ _{LR, SM))} δ by calculating a total steering angle (δ _{LW, total)} (from the signal δ _SM) of the servo motor rotational angle sensor ( 17 ) and the signal (δ _LR ) of the steering wheel rotation angle sensor ( 11 ) according to the following formula: δ _{LW, total} = i ₁ × δ _LR + i ₂ × δ _SM , Forming an angular difference (δ _Diff ) from total steering angle (δ _{LW, total} ) and pinion angle (δ _pinion ) and outputting an error signal when the angular difference (δ _Diff ) exceeds a predetermined limit value (S). With: i ₁ : Gear ratio between steering wheel angle sensor ( 11 ) and pinion angle sensor ( 19 ) and i ₂ : gear ratio between first actuator rotor angle sensor ( 17 ) and pinion angle sensor ( 19 ) A method according to claim 1 or 2, characterized in that the error signal is output only when the angular difference (δ _Diff ) exceeds a predetermined limit value (S) during the duration of a predetermined time interval (At). Method according to one of claims 1 to 3, characterized in that the limit value (S) as a function of the rotational speed of the steering wheel ( 1 ). Method according to one of claims 1 to 4, characterized in that the limit value (S) is determined as a function of the driving speed of the vehicle. Method according to one of claims 1 to 5, characterized in that the limit value (S) as a function of the between steering wheel ( 1 ) and steering column ( 3 ) transmitted torque is set. Method according to one of claims 1 to 6, characterized in that the limit value (S) is stored in maps or characteristic curves. Computer program, characterized in that it is suitable for carrying out one of the methods claimed above. Computer program according to claim 8, characterized in that it can be stored on a storage medium. Control device for a steering system of a vehicle, characterized in that it is suitable for carrying out a method according to one of claims 1 to 7. Steering for a vehicle with a steering wheel ( 1 ), a steering column ( 3 ) and a steering gear ( 5 ) for implementing the steering movements of the steering wheel ( 1 ) in positioning movements of the steered wheels of the vehicle, with a superposition gear ( 13 ) for superposition of the adjusting movement (δ _SM ) of a first servomotor ( 15 ) to the steering movements, with a steering wheel rotation angle sensor ( 11 ) for detecting the steering movements of the steering wheel ( 1 ), with a pinion rotation angle sensor ( 19 ) for detecting the rotational movement of a steering wheel ( 1 ) driven pinion ( 7 ) of the steering gear ( 5 ), with a first actuator rotor angle sensor ( 17 ) for detecting the actuating movement (δ _SM ) of the first servomotor ( 15 ) and with a control unit ( 23 ) for evaluating the steering wheel angle sensor ( 11 ), Pinion angle sensor ( 19 ) and first actuator rotor angle sensor ( 17 ) generated signals and for driving the first servomotor ( 15 ), characterized in that the control unit ( 23 ) is suitable for carrying out a method according to one of claims 1 to 7.

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