DE102016008791A1 - Method for operating a vehicle - Google Patents

Abstract

The invention relates to a method for operating a vehicle (1). According to the invention, a transverse guidance assistance system (2) steers the vehicle (1) autonomously or supports a steering operation of a vehicle driver, interventions of the lateral guidance assistance system (2) in a steering device (5) of the vehicle (1) being limited by safety steering force limit values and these safety steering force limit values being dependent on a hand moment applied by the vehicle driver to a steering wheel of the vehicle (1) is adjusted and / or shifted in dependence on a respective driving state of the vehicle (1).

Description

The invention relates to a method for operating a vehicle according to the features of the preamble of claim 1.

From the prior art, as in the DE 10 2009 000 868 A1 described an apparatus and method for controlling a steering system in a vehicle, wherein the steering system comprises a plurality of sub-systems, which are adapted to direct at least one steering request to the steering system in each case. The device has an arbitration and limitation logic that prioritizes steering requests directed to the steering system by different subsystems and optionally suppresses coincident steering requests such that a predetermined overall level of the steering torque exerted by the steering system is not exceeded.

In the DE 10 2011 055 339 A1 For example, a method of determining a rack force for a steering apparatus of a vehicle and a steering apparatus of a vehicle are described. In the method, the rack force is determined as a function of a steering angle magnitude that characterizes an actual wheel steering angle or a desired value of the wheel steering angle. A magnitude is determined which characterizes a lateral force on an axis of the steering device. The rack force is determined as a function of the lateral force, wherein the determination of the rack force comprises filtering by means of a signal processing element with proportional-differential transmission behavior.

The invention is based on the object to provide a comparison with the prior art improved method for operating a vehicle.

The object is achieved by a method for operating a vehicle having the features of claim 1.

Advantageous embodiments of the invention are the subject of the dependent claims.

In a method according to the invention for operating a vehicle, a transverse guidance assistance system steers the vehicle autonomously or supports a steering operation of a vehicle driver, interventions of the transverse guidance assistance system in a steering device of the vehicle being limited by safety steering force limit values, also referred to as safety limits, which are suitably assigned to a steering assistance device Safety steering limits are adjusted in response to a force applied by the driver to a steering wheel of the vehicle manual torque and / or moved in response to a respective driving condition of the vehicle.

The steering assist device is also referred to as power steering and is expediently designed as an electromechanical power steering. The autonomous steering or the support of the steering operation of the vehicle driver by the transverse guidance assistance system is expediently by a basic steering function additively superimposed steering force specification or by an angle of a wheel angle, which is converted by a control law in an additive steering force specification. In a commonly used rack and pinion steering power specification is also referred to as Rackforce. The safety steering force limits are therefore also referred to as rack force limits.

So far, for steering driver assistance systems, i. H. for transverse guidance assistance systems, usually given quasi-static driving speed-dependent safety limits, which, however, can reach their limits, in particular when passing through elongated curves. The solution according to the invention makes better use of limits that are manageable by the driver and stem from functional safety. This improves the performance of the lateral guidance assistance system. In particular, the transverse guidance assistance system is fully operational by the solution according to the invention in traffic situations in which it currently reaches its limits, for example, in tight bends. The method according to the invention expediently builds on signals only in such a way or assembles the signals used in such a way that predetermined functional requirements and safety requirements are still met.

Embodiments of the invention will be explained in more detail below with reference to a drawing.

Showing:

1 a schematic representation of a vehicle on a roadway and a preceding vehicle further.

Corresponding parts are provided in all figures with the same reference numerals.

1 shows a schematic representation of a vehicle 1 on a carriageway FB and a preceding vehicle F. The vehicle 1 has a lateral guidance assistance system 2 on which the vehicle 1 autonomously steers or supports a steering operation of a driver. The lateral guidance assistance system 2 allows, for example, a lane keeping of the vehicle 1 where it is based on the preceding vehicle F and / or lane markings FSM a lane FS. In 1 is in particular a control and / or regulating unit of the lateral guidance assistance system 2 for example, which is also referred to as an intelligent drive controller (IDC) and represents a central fusion and control platform. The lateral guidance assistance system 2 For example, it can be coupled with a distance control system, so that then an assistant for the driver in a transverse guide and longitudinal guidance of the vehicle 1 given is.

For autonomous steering of the vehicle 1 or to assist the driver's steering operation is by the lateral guidance assistance system 2 expediently given a steering force, ie, for example, there is a direct steering force specification and / or a specification of a steering angle resulting from a steering input. The angle specification by the lateral guidance assistance system 2 indicates a respective wheel angle, which steered wheels 3 of the vehicle 1 should take. The lateral guidance assistance system 2 the steering force is expediently a steering assistance device 4 which is part of a steering device 5 of the vehicle 1 is. The steering assist device 4 is expediently designed as a power steering, in particular as an electromechanical power steering, also referred to as Electric Power Steering (EPS). Since steering devices 5 , in particular for transverse guidance assistance systems 2 suitable steering devices 5 , Usually designed as a rack and pinion steering, the steering force, since it is on a rack of the steering device 5 acts, also referred to as Rack Power or Rackforce.

So far are for steering driver assistance systems, ie for lateral guidance assistance systems 2 , usually quasi-static safety limits given, but in particular when driving through long curves can reach their limits. The following describes a method by which functional safety limits are better utilized. This provides a performance of the lateral guidance assistance system 2 improved. In particular, the transverse guidance assistance system 2 thus fully operational even in traffic situations in which it is currently reaching its limits, for example even in tight bends. The method improves a rack force limiter, ie, a power steering limiter, by implementing a hand-torque based rack force limiter, ie, safety steering force limiter, and a drive state-dependent shift of rack force limits, ie, safety steering limits. These are in the process of operating the vehicle 1 in which the lateral guidance assistance system 2 the vehicle 1 autonomously steers or supports a steering operation of the driver, interventions of the lateral guidance assistance system 2 in the steering device 5 of the vehicle 1 limited by safety steering force limits, these safety steering force limits depending on a by the driver on a steering wheel of the vehicle 1 applied hand torque adapted and / or depending on a respective driving condition of the vehicle 1 be moved.

The safety limit values of the steering effort specifications, ie the safety steering force limit values, are based on their effects on the steering wheel and on the vehicle 1 bound. In addition to the manual torque on the steering wheel, the change of the driving state determines the safety steering force limit values. If safety steering force limit values resulting from a steering torque, ie from the hand moment acting on the steering wheel, and safety steering force limits resulting from the driving condition are considered separately from each other, a two-stage rack force limiter concept, ie a two-stage steering force limiter concept, can be implemented.

Directs the driver against an additive steering force, which by the transverse guidance assistance system 2 is caused, this countersteering by the steering torque, ie by the force acting on the steering wheel manual torque of the driver is visible, which against the by the transverse guidance assistance system 2 preset and set steering force acts, the safety steering force limits must be reduced to the smallest safety steering force limit of steering torque, ie manual torque, and driving condition. Directs the driver with an additive steering force, ie the force exerted by the driver on the steering wheel hand moment acts in the same direction as that of the transverse guidance assistance system 2 given and set steering force, so should the Sicherheitslenkkraftgrenzwert primarily on Orient the safety steering force limit from the driving state change. This also applies if the hand moment disappears or is very small when countersteering.

By blending the safety steering force limit values as a function of the manual torque on the steering wheel, a hand-torque-based limiter concept, ie limiting concept, can be realized, which on the one hand affects the steering wheel and, on the other hand, the vehicle 1 holistically limited.

To realize a hand-moment based Rackforce limiter, i. H. Lenkkraftbegrenzers, two vehicle speed-dependent characteristics for the safety steering force limits from manual torque and driving condition must be implemented.

The selection of the maximum permissible steering force, ie the maximum permissible safety steering force limit value RF _Max , should be simplified via a normalized weighting factor μ:

The standardized weighting factor μ describes the proportion of the safety steering force limit values RF _{Max, StW} , which originate from the manual torque, at the maximum permissible safety steering force limit values RF _Max . The normalized weighting factor μ should only be used if the safety steering force limit values RF _{Max, Veh} from the driving state are greater than or equal to the safety steering force limit values RF _{Max, StW} from the manual torque. If the safety steering force limit values RF _{Max, Veh} from the driving state are smaller than the safety steering force limit values RF _{Max, StW} from the manual torque, the safety steering force limit values RF _{Max, Veh} from the driving state should be used as the maximum permissible safety steering force limit value RF _Max . This corresponds to a normalized weighting factor μ of zero.

In order to limit the change dynamics of the maximum permissible safety steering force limit values RF _{Max in a} targeted manner, the normalized weighting factor μ may be subjected to temporal filtering, for example a first-order low-pass filter, in order to obtain a filtered normalized weighting factor μ *.

Since the transition from larger maximum safety steering force limits RF _Max to be made to smaller maximum safety steering force limits RF _Max faster than smaller maximum safety steering force limits RF _Max to larger maximum safety steering force limits RF _Max, no single time constant to be used T _1, but there are different time constants T _{1, up} and T _{1, down} for the construction or dismantling of the normalized weighting factor μ can be used. The time constant T _{1, up} for the construction of the normalized weighting factor μ must be relatively small, for example 0.1 seconds. The time constant T _{1, down} for the reduction of the normalized weighting factor μ must be significantly greater than the time constant T _{1, up} for the construction of the normalized weighting factor μ, for example one second. The exact values for the time constants T _{1, up} and T _{1, down} are expediently in the development of the method, ie in the implementation of the method in practice and in the vehicle 1 , set.

In order to be able to handle the cases of counter steering and countersteering differently, the input of the filter must depend on the steering force specification of the control and / or regulating unit of the lateral guidance assistance system 2 or be controlled by an angle controller and the manual torque.

In order to be able to reliably detect co-steering or countersteering, minimum driver forces RF _Min and two threshold values M _{H, Min} and M _{H, Max} must be defined by the driver for the manual torque M _H. Is that of the lateral guidance assistance system 2 requested steering force RF _Rq magnitude less than the minimum steering force RF _Min should not detected counter-steering and the null input of the filter are set. If the requested steering force RF _{Rq exceeds} the minimum steering force RF _{Min in} absolute terms and a manual torque M _H occurs greater than the lower threshold value M _{H, Min of} the manual torque M _H in the opposite direction, a counter-steering is to be detected and the input of the filter as a function of Hand torque M _{H be} increased linearly. _Exceeds the requested steering force RF _Rq amount by the minimum steering force RF _Min and enters a manual torque M _H magnitude greater than the upper threshold M _{H, Max of} the manual torque M _H in the opposite direction, the input of the filter should be limited to the value one. The lower threshold value M _{H, Min} and upper threshold value M _{H, Max} for the manual torque M _H is defined as a function of the driving speed. Typically, the lower threshold M _{H, Min} for the manual torque M _H between 0.5 Nm and 1 Nm and the upper threshold M _{H, Max} for the manual torque M _H between 1 Nm and 2 Nm. The minimum steering force RF _Min should be greater than a friction force in the steering and a fraction of the maximum allowable steering force, which comes from the driving condition, ie the safety steering force limit RF _{Max, Veh} from the driving condition correspond.

Alternatively or expediently, in addition to the described hand-torque-based adaptation of the safety-steering-force limit values, a driving state-dependent shift of the safety-steering-force limit values described below takes place. The quasi-static safety steering force limit values used hitherto are functionally perfectly adequate on straight carriageway sections. In extended curves, especially at higher vehicle speeds, functional safety steering limits can be achieved quickly without the assistance of the driver. An increase in the intervention of the lateral guidance assistance system 2 even a slow increase is no longer possible with the achievement of static limits. By a suitable driving state-dependent shift of the safety steering force limit values, the functionally usable range can be expanded in curves. On the one hand, the adaptation must be slow enough to ensure control in the event of a fault, and on the other hand fast enough to ensure that S-curves, for example, on rural roads, are also passed through.

To ensure that the displacement takes place only when the driver does not mit- or counter, the manual torque M _H must be taken into account in a shift. Since not all by means of the control and / or regulating unit of the lateral guidance assistance system 2 provided assistance functions require a driving state-dependent shift of the safety steering force limit values, the shift takes place only after a request by the lateral guidance assistance system 2 more precisely by its control and / or regulating unit. For example, an evasive assistance function assisting the vehicle operator does not require a driving state-dependent shift of the safety steering force limit values.

The adjustment of the safety steering force _{limit values} is based on an asymmetric shift of the minimum safety steering force _{limit values} RF _{Dyn, Min} or maximum safety steering force _{limit values} RF _{Dyn, Max} . RF _{Dyn, Max} = RF _Max (1 + σ) [9] RF _{Dyn, Min} = -RF _Max (1 - σ) [10]

The asymmetric displacement should be realized by a quasi driving state dependent value σ. The absolute value of the driving condition-dependent value σ must be limited to a maximum value σ _Max less than 1/2. | Σ | ≤ σ _Max ≤ ½ [11]

The construction and dismantling of the driving state-dependent shift can be done via an aperiodic low-pass filter 2nd order. T 2 / 1σ .. + 2T ₁ σ. + σ = σ _Max ρθ [12]

The time constant T ₁ in formula 12 is usually not identical to the time constant T ₁ used in formulas 2 to 4 above. On the one hand to ensure great variability and on the other hand the controllability of the shift, the time constant T ₁ must be between 0.5 seconds and 2 seconds.

The input of the filter is to be formed by the product of the maximum value σ _{max of} the displacement, a normalized driving state ρ and a manual torque-based component θ. The normalized driving state ρ represents the transverse movement of the vehicle 1 and must be limited in value to one.

und Querbeschleunigung a_y ohne die Unterstützung durch den Fahrzeugführer stationär ein Gleichgewicht einstellt, soll der normierte Fahrzustand ρ aus allen drei Größen gebildet werden, zusammengefasst in dem Wert α.As between the from the cross-guidance assistance system 2 requested steering force RF _Rq and a current yaw rate

and lateral acceleration a _y stationary setting without the assistance of the driver, the normalized driving state ρ should be formed of all three quantities, summarized in the value α.

und Querbeschleunigung a_y zweckmäßigerweise offsetkorrigiert. Anschließend werden die offsetfreien Größen angeforderte Lenkkraft RF_Rq, Querbeschleunigung a_y und Gierrate

normiert. Die Normierung der einzelnen Größen muss über fahrgeschwindigkeitsabhängige Maximalwerte, d. h. über eine maximale Querbeschleunigung a_y,Max und Gierrate

und die Sicherheitslenkkraftgrenzwerte RF_Max,Veh, erfolgen. D. h. als Bezugsgröße für die angeforderte Lenkkraft RF_Rq werden die Sicherheitslenkkraftgrenzwerte RF_Max,Veh verwendet, die aus den Fahrzustandsänderungen stammen. Für die normierte Gierrate bzw. Querbeschleunigung kann eine gemeinsame fahrgeschwindigkeitsabhängige Kennlinie angelegt werden.Where ∧ is the logical operator "and" and ∨ or logical operator "or". In order to be able to compare the sizes, the measured quantities become yaw rate

and lateral acceleration a _y suitably offset corrected. Subsequently, the offset-free quantities requested steering force RF _Rq , lateral acceleration a _y and yaw rate

normalized. The normalization of the individual quantities must be based on maximum speed-dependent maximum values, ie on a maximum lateral acceleration a _{y, max} and yaw rate

and the safety steering force limits RF _{Max, Veh} , occur. Ie. As a reference for the requested steering force RF _Rq , the safety steering force _limit values RF _{Max, Veh} are used which originate from the driving state changes. For the normalized yaw rate or lateral acceleration, a common vehicle speed-dependent characteristic curve can be created.

erfolgt zweckmäßigerweise über die Fahrgeschwindigkeit v_x.

The conversion of the maximum lateral acceleration a _{y, max} and yaw rate

expediently takes place via the driving speed v _x .

If the normalized requested steering force, the normalized lateral acceleration and the normalized yaw rate have a positive sign, the normalized driving state ρ should correspond to the lowest value. If the normalized requested steering force, the normalized lateral acceleration and the normalized yaw rate have a negative sign, the normalized driving state ρ should correspond to the largest value. If the normalized lateral acceleration and the standardized yaw rate have different signs, the normalized driving state ρ should be set to the value zero.

Alternatively or in addition to the normalized individual variables, a normalized steering wheel angle or steering angle can also be used to form the normalized driving state. The normalization of the angle can be done via a driving state related maximum steering wheel angle or steering angle.

The hand torque-based portion θ in the input of the low-pass filter should treat equal and opposite steering equal. The control of the hand torque-based component θ shall be described by means of a normalized quadratic dependence.

Without manual torque M _H , the hand torque-based component θ in the filter input should be one. If the manual torque M _H exceeds a maximum manual torque in absolute terms, the hand torque-based component θ must assume the value zero. If the manual torque M _{H is} smaller in magnitude than the maximum manual torque, the hand-torque-based component θ should be reduced by a normalized quadratic dependence. As a reference for the normalization of the manual torque M _H is advantageously a driving speed-dependent maximum manual torque is used. Ideally, the maximum manual torque corresponds to the upper threshold value M _{H, Max of} the manual torque M _H , which is already used to detect the counter-steering in the hand-torque-based steering force limiter described above.

To activate the driving state-dependent displacement of the safety steering force limit values, the electromechanical power steering system expediently receives a control signal from the control and / or regulating unit of the lateral guidance assistance system 2 , If the control and / or regulating unit requests a movement-state-dependent shift, the maximum permissible shift should be set in the filter input. If the control and / or regulating unit does not request a movement state-dependent shift, the filter input is expediently set to the value zero.

LIST OF REFERENCE NUMBERS

1

vehicle

2

Lateral control assistance system

3

steered wheel

4

Steering assist device

5

steering device

F

preceding vehicle

FB

roadway

FS

lane

FSM

lane marker

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102009000868 A1 [0002]
• DE 102011055339 A1 [0003]

Claims (5)

Method for operating a vehicle ( 1 ), characterized in that a transverse guidance assistance system ( 2 ) the vehicle ( 1 ) autonomously steers or supports a steering operation of a vehicle driver, interventions by the lateral guidance assistance system ( 2 ) in a steering device ( 5 ) of the vehicle ( 1 ) are limited by safety steering force limit values and these safety steering force limit values are determined as a function of the vehicle driver's steering wheel of the vehicle ( 1 ) applied hand torque adapted and / or in dependence on a respective driving condition of the vehicle ( 1 ) are moved. A method according to claim 1, characterized in that the safety steering force limit value is reduced to the smallest predetermined value when the vehicle driver applies this to the steering wheel of the vehicle ( 1 ) applied hand torque against a by the transverse guidance assistance system ( 2 ) predetermined steering force acts. Method according to one of the preceding claims, characterized in that the safety steering force limit value is based on the respective driving state when the vehicle driver applies this to the steering wheel of the vehicle ( 1 ) exerted manual torque in the direction of a transverse guidance assistance system ( 2 ) predetermined steering force acts. Method according to one of the preceding claims, characterized in that during the displacement of the safety steering force limit values as a function of the respective driving state of the vehicle ( 1 ) by the driver to the steering wheel of the vehicle ( 1 ) applied hand moment is taken into account. Method according to one of the preceding claims, characterized in that the displacement of the safety steering force limit values as a function of the respective driving state of the vehicle ( 1 ) only after a request by a control and / or regulating unit of the lateral guidance assistance system ( 2 ) he follows.

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