DE102015005124A1 - A method of controlling a steering actuator of a steering system of a vehicle, steering system and vehicle having such a steering system - Google Patents

Abstract

Method for controlling a steering actuator of a steering system with a steering input device and with variable steering ratio in a vehicle, wherein a steering input applied to the steering input device is detected to determine the desired steering movement and an input value (x) is determined as a function of the determined input value (x) Based on a predefined setpoint curve (ASoll = f (x)) a setpoint (ASoll) is determined and the steering actuator with this setpoint (ASoll) for setting a target value (RLW) and thus to implement the desired steering movement, the setpoint curve (ASoll = f (x)), on the basis of which the desired value (ASoll), with which the steering actuator is controlled, is defined by a basic function (fBasis (x)), which is determined via the steering input range of a steering direction (= {xmin }, = {0 ... xmax}) is composed of at least two base setpoint curve segments, the individual base setpoint curve segments parabolic are tangent and merge into each other so tangential that results in a harmonic, polstellenfreier setpoint curve. Furthermore, the invention relates to a trained for carrying out the method steering system and a vehicle with such a steering system.

Description

The invention relates to a method for controlling a Lenkaktuators a steering system with a steering input device with variable steering ratio in a vehicle, preferably for controlling a steer-by-wire steering system, in particular for controlling a steering system with a joystick as a steering input device, wherein the steering input device is designed to determine a desired by a driver steering movement and wherein the steering actuator is adapted to implement the desired steering movement, wherein in a first step to determine the desired steering movement applied to the steering input device steering input is detected and from an input value is determined in a second Step in dependence on the determined input value based on a predefined setpoint curve a setpoint is determined and in a third step, the steering actuator with this setpoint to set a target size and thus to implement the desired Lenkbe movement is controlled.

Furthermore, the invention relates to a steering system with variable steering ratio with a steering input device and a steering actuator and a vehicle with such a steering system, in particular a disabled vehicle, wherein the steering system is preferably a steer-by-wire steering system, in particular a steering system with a joystick as a steering input device ,

Generic methods and appropriately designed steering systems are basically known from the prior art, including steer-by-wire steering systems, steering systems with a joystick as a steering input device and steer-by-wire systems with a joystick as a steering input device. Steer-by-wire steering systems are basically suitable for all types of vehicles, d. H. for air, water and land vehicles, with steer-by-wire steering systems can be used particularly advantageously in aircraft and construction machinery. Often the steering input device is also designed as a joystick or joystick.

Steer-by-wire steering systems, in particular with a joystick as a steering input device, are also preferably used in disabled vehicles, d. H. in specially adapted for disabled people vehicles, such as electric wheelchairs or in specially adapted to the needs of disabled people vehicles, since by-wire technology, a particularly simple adaptation of a vehicle to the needs of a physically disabled driver is feasible. The use of a joystick as a steering input device is in many cases of central importance, since the people are provided for such vehicles, usually due to their disability are not able to operate a conventional steering wheel.

Generic steering systems or vehicles with such steering systems often have a variable steering ratio, for example, a speed-dependent steering ratio. Ie. the steering ratio between an applied steering input and an actually converted steering movement is variable and not constant, in particular different for different driving situations and, for example, depending on the vehicle speed.

It is among other things of the steering ratio itself, d. H. Depending on the absolute ratio of steering input to steering movement, as well as the course of the steering ratio depends on whether the driving experience that a driver experienced when driving a vehicle, as comfortable, especially safe and comfortable, or as unsafe and uncomfortable and thus uncomfortable ,

According to the DE 10 2009 014 392 A1 can be achieved with a generic steering system with variable steering ratio a particularly comfortable steering feel when the global steering ratio from a steering angle of a steering wheel to a Radeinschlagwinkel or the local gear ratio of the change in the steering angle to the change in Radeinschlagswinkels from a middle position of the steering wheel towards larger steering angles decreases and the course of the steering ratio in a first steering angle range about the central position is described by a function of second or higher degree and in an adjoining, second steering angle range by a linear function. In some cases, it may also be advantageous to provide a steering transmission path in a third steering angle range which adjoins the second steering angle range to the outside, which is described by a decreasing e-function or a higher-order polynomial.

From the DE 10 2007 053 818 A1 , Which relates to a method for operating a generic steering system with variable steering ratio, is also known, the target value with which the steering actuator is driven to set the desired value, in this case, a setting angle, not only in response to an applied via a steering wheel input value determine, but in addition other sizes, such as For example, to take into account the vehicle speed or the current setting angle of the steering actuator. Moreover, it is disclosed that in some driving situations it may be advantageous to correct the setting angle, ie the nominal value with which the steering actuator is driven, by adding a so-called correction angle or compensating angle to a base setting angle.

Of particular importance is the steering ratio of a steering system in this case in vehicles for the disabled, especially in those cases in which a joystick is provided as a steering input device. Because in particular the operation of a joystick requires due to the short steering lines good fine motor skills, but about which physically disabled people often due to their disability not or no longer to the required extent, so that the steering ratio may not be too direct. However, the steering ratio may not be chosen too indirectly, since otherwise the vehicle reaction may be perceived as being unreasonably delayed on the steering input, which also makes vehicle control more difficult.

Object of the present invention is to provide an alternative method for controlling a steering actuator of a generic steering system in a motor vehicle, preferably for controlling a steer-by-wire steering system with a joystick as a steering input device, with a pleasant driving feeling can be achieved and in particular also allows physically handicapped people a pleasant driving. It is another object of the present invention to provide a suitably designed steering system and a correspondingly designed vehicle.

This object is achieved by a method having the features of claim 1 and a steering system having the features of claim 17 and a vehicle having the features of claim 18. These and other features will become apparent from the claims and from the description also from the drawings , Wherein the individual features can be realized in each case alone or in the form of sub-combinations in one embodiment of the invention and can represent advantageous and inherently protectable embodiments for which protection is claimed here. Of course, the features described only in connection with a method according to the invention can also be realized in a steering system according to the invention and / or a vehicle according to the invention and vice versa.

A method according to the invention is characterized in that the setpoint curve, on the basis of which the desired value is determined with which the steering actuator is driven, depends on a base function composed of a plurality of base setpoint curve segments, which is composed of at least two basic setpoint curve segments via the steering input section of a steering direction, are the parabolic segments and so tangentially merge into each other, that results in a harmonic, polstellenfreier setpoint curve.

In order to determine the steering movement desired by the driver, a steering input applied by the vehicle driver to the steering input device can be detected at least for one steering direction, preferably for two steering directions, in particular for two opposite steering directions. For this purpose, the steering input device can preferably be moved accordingly, particularly preferably correlated to a desired steering movement and in particular within a defined steering input range, d. H. for example, up to a left stop to the left for a desired steering movement to the left and a maximum to a right stop to the right for a desired steering movement to the right, wherein the movement of the steering input device is detected by means of appropriate sensors. From the driver's input to the steering input device and detected steering input, d. H. preferably from the detected movement, then the input value can be determined, in dependence of which the set value for controlling the steering actuator can be determined in order to determine the required setpoint value, ie. H. to set the desired steering movement.

In this case, the steering system, in particular the steering input device, of course, be designed to detect further driver requests, such as for detecting a desired vehicle speed. Ie. the steering system can additionally be designed to record further driver inputs, the steering system either having at least one additional input device for this purpose, and / or the steering input device of the steering system being designed such that further input values can be detected with the steering input device.

If the steering input device is, for example, a joystick, the joystick is preferably designed such that a desired steering movement is detected by moving the joystick to the left and / or right can be and in particular by moving up and / or down a desired vehicle speed or a desired acceleration and / or deceleration. The associated desired size would be in this case, for example, an accelerator pedal position and / or a brake pressure.

The steering input device is preferably a steering wheel, a control stick, a joystick, a handlebar or a steering slide, wherein the aforementioned steering input devices differ above all in the required for their operation, in particular in the predetermination of a desired steering movement. Ie. Depending on the steering input device, a specific movement is required by the driver to specify the desired steering movement, d. H. to apply the steering input.

For disabled vehicles in particular joysticks, both one-handed joysticks and two-handed joysticks and conventional steering wheels and so-called mini-steering wheels, in particular with a knob or the like, have proven to be suitable. Depending on the steering input device, the input value is thus preferably a steering path, a steering angle or a combination thereof. Of course, other common input devices as steering input device are conceivable.

Preferably, the determined input value from which the setpoint value for controlling the steering actuator is determined on the basis of the predefined setpoint curve is a scaled variable, preferably a scaled-down variable, in particular based on the available steering path of the steering input device, wherein the input value is particularly preferred is scaled each available for a steering direction steering path. Ie. Preferably, the determined input value represents the proportion of the traveled steering path from the total steering travel of the steering input device in the respective steering direction in percent. To distinguish the steering direction, it is advantageous, in particular with only two steering directions, for example, right and left, one of the steering directions to assign a negative sign. That is, the amount of the input value may preferably assume values between 0% and 100%, wherein the input value may preferably assume values of 0% to 100% for each steering direction, ie. H. in particular, values of -100% to 0% for one steering direction and 0% to 100% for the other steering direction in two steering directions.

The steering actuator of the steering system, which is designed to convert the electrical control signal with the desired value, with which it is controlled, into a mechanical steering movement and adjust the desired value as a function of the desired value, preferably has a drive device and corresponding mechanical, kinematically coupled to the Antriebseinreichtung Components with which the steering movement can be mechanically implemented. Particularly preferred are the mechanical components with the support of the drive device, d. H. at least partially by means of the drive means, or even completely moved by the drive means to perform the desired steering movement.

In this case, the drive device of the steering actuator is preferably an electromechanical drive device, but it can of course also be designed electrohydraulically, purely hydraulically, pneumatically or the like. Depending on the type of steering actuator or, depending on the drive device, the desired value for controlling the steering actuator can be, for example, a desired value for an electrical voltage, a hydraulic or pneumatic pressure or a comparable physical variable.

In the mechanical components which are kinematically coupled to the drive device and which are moved for the implementation of the actual steering movement, it is preferably each of the usually steerable components of a vehicle, the term vehicle is not to be understood as limiting motor vehicles, but includes all land, water and air vehicles, d. H. In addition to motor vehicles and construction equipment, such as excavators, helicopters, aircraft and ships, especially handicapped vehicles based on cars, and electric wheelchairs. The usual steerable components are in the case of a motor vehicle, for example, the steering linkage and the steerable wheels of an axle, in an aircraft, for example, the height, side and / or aileron and an excavator, for example, the driven axles and the excavator with the attached thereto attachment, for example, an excavator bucket.

The setpoint curve according to the invention or the setpoint curve course according to the invention preferably apply to a linear behavior of the setpoint to the setpoint, ie. H. they preferably apply to a linear system behavior of the steering actuator. In the control of a steering actuator with non-linear system behavior, it may therefore be necessary to obtain the steering transmission characteristic required for the desired, pleasant driving feel, to adapt the desired value curve by means of a corresponding correction function in order to compensate for the existing nonlinearities.

The method according to the invention is preferably designed to control a steer-by-wire steering system, wherein a steer-by-wire steering system in the sense of this application is understood to mean a steering system with a steering input device and a steering actuator, in which a steering command from a sensor is only electrically passed on to the steering actuator. Ie. a steer-by-wire steering system is a steering system which characteristically has no mechanical connection between the steering input device and the steering actuator, in particular no mechanical transmission between the steering input device and the steering actuator.

The method according to the invention is particularly suitable for controlling a steering actuator of a steering system with a joystick or a joystick or the like, since a steering transmission characteristic which is perceived as very pleasant can be set with the desired-value curve course according to the invention. The desired value curve course according to the invention also enables physically disabled people precise and therefore safe steering, so that the method according to the invention is particularly suitable for controlling a steering actuator of a steering system of a disabled vehicle.

Due to the tangential, harmonic transitions without poles a harmonic curve of the setpoint curve and thus also the setpoint size is ensured. A usually as a particularly unsettling and thus uncomfortable perceived "jumping" of the target size can be avoided.

With the method according to the invention, a very pleasant steering feel, in particular a very precise and thus safe steering feel, can be generated with the help of the setpoint curve characteristic according to the invention, even with only short steering paths compared to the steering wheel, such as a joystick or joystick ,

In an advantageous embodiment, at least one basic setpoint curve segment is described by a parameterizable function. Preferably, the parameters for defining the base target curve segment can be stored in the steering system and adjusted as needed. Ie. Preferably, the setpoint curve is a so-called "controllable" function, so that an adjustment of the steering behavior of the vehicle to the desired steering behavior is possible within the scope of the possible parameter variations. As a result, the steering behavior of the vehicle can be adapted in a simple manner to the respective needs and abilities of the vehicle driver, for example to the special restrictions of a physically handicapped vehicle driver.

In two steering directions, in particular two opposite steering directions, the desired value curve is preferably defined by a basic function, which is composed over the entire steering input range of at least four basic setpoint curve segments, preferably each steering direction at least two base setpoint curve segments are assigned, in particular symmetrically about a zero position , Ie. Preferably, the portion of the setpoint curve of a steering direction is defined in each case by two base setpoint curve segments, wherein the zero position is particularly preferably located in the middle of the entire steering range and the steering range of the individual steering directions are in particular equal.

In a preferred embodiment of a method according to the invention, the setpoint curve A _setpoint = f (x) is point-symmetrical with respect to the point of symmetry (x = 0, A _setpoint = f (x = 0)). As a result, symmetrical steering behavior in both steering directions can be achieved with two steering directions.

The basic function is particularly preferably composed of at least four parabolic segments, in particular of four parabolic segments of the second order, wherein the setpoint curve, starting from a smallest possible, d. H. minimal, input value towards the greatest possible, d. H. maximum input value, in the third quadrant of a first, upwardly open parabolic segment and an adjoining, second, downwardly open parabolic segment is composed and in the first quadrant of a third, upwardly open parabolic segment and an adjoining, fourth, down opened parabolic segment.

In principle, there is the danger that vehicle accelerations occurring due to the movement of the vehicle, for example due to impacts when driving through potholes or the like, and in particular occurring lateral accelerations, lead to an undesired steering movement, in particular coupled with it. Since such, disturbing vehicle accelerations particularly affect the zero position, in the steering systems known from the prior art, the steering ratio to the zero position or a central position, especially at high Fahrzeuggeschwindgkeiten, often rather indirectly chosen with a flat rise with increasing steering input. However, this usually requires to be available with the standing Steering a position range of the steering actuator and thus to be able to fully exploit an adjustment range of the target size, for larger steering input values to compensate for a more direct steering ratio, d. h a steeper increase in the steering ratio curve. However, this means that even in a range of larger steering input values even small steering movements cause a large change in the setpoint and thus the target size. Ie. The direct steering ratio at larger input values, which is required to compensate for the indirect translation of the zero position when the entire range of the target size is to be exploited, leads to the fact that in the range of larger input values even small steering movements cause a significant vehicle response. However, this often leads to uncertainty of the driver and makes it difficult to precisely steer the vehicle, especially at higher speeds in narrower curves, such. B. in roundabouts, etc .. and creates an unpleasant driving experience.

With a prescribed setpoint curve, which starts from a smallest possible, d. H. minimal, input value towards the greatest possible, d. H. maximum input value, in the third quadrant of a first, upwardly open parabolic segment and an adjoining, second, downwardly open parabolic segment is composed and in the first quadrant of a third, upwardly open parabolic segment and an adjoining, fourth, down opened parabolic segment, however, this conflict of objectives can be solved advantageously, in particular with second-order parabola segments.

wobei

die Menge aller mittels des Lenkeingabegerätes aufbringbaren Eingabewerte x ist und x_min, x ' / 2, x ' / 1, x₁, x₂, x_max die Bereichsgrenzen der einzelnen Abschnitte der Basis-Sollkurvensegmente

definieren, wobei jeweils p, Sx, Sy sowie die Wahl der Bereichsgrenzen der einzelnen Abschnitte der Basis-Sollkurvensegmente

die einstellbaren Parameter zur Anpassung der Funktion sind, wobei vorzugsweise gilt x ' / 1 ≤ 0 und x ' / 2 < 0 und x₁ ≥ 0 und x₂ > 0 und wobei gilt

It has to be advantageous for two steering directions, z. B. right and left, preferably input values <0 describe a steering input to the left and input values> 0 a steering input to the right, a basic function f _base (x) exposed, which is defined as follows:

in which

the amount of all applicable by means of the steering input device input values x is and x _min , x '/ 2, x' / 1, x ₁ , x ₂ , x _max the range limits of the individual sections of the basic setpoint curve segments

defining, where p, Sx, Sy and the choice of the range limits of the individual sections of the basic setpoint curve segments

are the adjustable parameters for adapting the function, preferably x '/ 1 ≤ 0 and x' / 2 <0 and x ₁ ≥ 0 and x ₂ > 0 and where

wobei y_min bzw. y_max der minimal bzw. maximal mögliche Sollwert A_Soll ist, mit dem der Lenkaktuator bei dem zugehörigen minimalen bzw. maximalen Eingabewert x_min bzw. x_max angesteuert werden soll, wobei jeweils p sowie die Wahl der Bereichsgrenzen der einzelnen Abschnitte der Basis-Sollkurvensegmente die einstellbaren Parameter zur Anpassung der Funktion sind, wobei vorzugsweise gilt x ' / 1 ≤ 0 und x ' / 2 < 0 und x₁ ≥ 0 und x₂ > 0 und wobei vorzugsweise gilt x_min = –x_max und/oder y_min = –y_max und/oder x₁ = –x ' / 1 und/oder x₂ = –x ' / 2. Particularly preferably, the basis function f _basis (x) is defined as follows:

where y _min or y _{max is} the minimum or maximum possible setpoint A _setpoint with which the steering actuator is to be controlled at the associated minimum or maximum input value x _min or x _max , where p and the selection of the range limits of the individual Sections of the base setpoint curve segments are the adjustable parameters for adapting the function, wherein preferably x '/ 1 ≤ 0 and x '/ 2 <0 and x ₁ ≥ 0 and x ₂ > 0, and preferably x _min = -x _max and / or y _min = -y _max and / or x ₁ = -x '/ 1 and or x ₂ = -x '/ 2.

Particularly preferably, the parameters p each have the same amount, ie p _III-1 = p _III-2 = p _I-1 = p _I-2 is particularly preferred.

Particularly preferably, at least one base setpoint curve segment defines a deadband, wherein the base setpoint segment defining the deadband is preferably associated with a region around the zero position of the steering input device and thus defines a deadband about the zero position, the base Specified curve segment in particular defines a dead band symmetrical about the zero position. Due to the dead band, the insensitivity to disturbing vehicle accelerations around the zero position can be further improved.

In this case, the setpoint curve profile is preferably constant in the area of the deadband. Particularly preferably, the dead band extends in a steering direction over a range of about 1% to 10% of the steering path of this steering direction, starting from the zero position, preferably over a range of 3% to 5%, in particular over a range of 4%.

A particularly advantageous setpoint curve is composed of five base setpoint curve segments, wherein the setpoint curve between the second downwardly opened parabola segment and the third upwardly open parabola segment has a base setpoint curve segment which defines a deadband.

mit x₁, x ' / 1 ≠ 0. In this case, a base function f _basis (x) composed of five basic setpoint curve segments is preferably defined as follows:

With x ₁ , x '/ 1 ≠ 0.

mit x₁, x ' / 1 ≠ 0. In particular, a basic function f _basis (x) has proven to be particularly advantageous, which runs tangentially to a horizontal tangent into the zero position and / or into at least one end point of the dead band and / or into at least one end point at the end of the steering input range. Ie. particularly preferably:

With x ₁ , x '/ 1 ≠ 0.

In other words, it is preferable f '/ base (x = 0) = 0 and or f '/ base (x = x _max , x _min ) = 0 and or f '/ base (x = x ₁ , x' / 1) = 0, where Sy _III-1 = 0 and / or Sy _I-1 = 0 is preferred. This allows a flat rise of the nominal value curve profile due to a flat rise of the base function around the zero position, ie due to the flat gradient of the base function around the zero position and thus, despite short operating paths, a particularly precise steering, especially around the zero position and / or the end point around.

Preferred is an amount of a slope | f '/ base (x) | of the basis function f _basis (x) in at least one transition point between two adjacent base setpoint curve segments ≤ 1 | f '/ base (x' / 2, x '/ 1, x ₁ , x ₂ ) | ≤ 1. As a result, a good leadership, ie a manageable steering behavior can be achieved. In particular, this can ensure that the slope in the relevant transition point is smaller than the slope of a 45 ° straight line, which defines the desired value curve in many steering systems known from the prior art.

Preferably, the amount of a slope | f '/ base (x) | _base function f _base (x) at a transition point between a base target curve segment forming a deadband and an adjacent base target curve segment ≦ 1 adjacent thereto. Preferably, the slope of the base function at the transition point from the deadband or the zero position is smaller than the slope of a 45 ° straight line. As a result, a particularly good controllable and pleasant to be perceived articulation behavior can be achieved.

In a particularly advantageous embodiment of the method according to the invention, the desired value curve not only depends on the basic function f _base (x), but is defined by it. Ie. In a particularly advantageous embodiment, not only is A _setpoint = F (f _basis (x)), but rather A _setpoint = f _basis (x).

Preferably, the function that defines the set value curve, in particular the _base function f _base (x), monotonically increasing and / or continuously differentiable.

Particularly preferably, not only does the basic function f _Basis (x), but in particular the setpoint curve tangent to a horizontal tangent in a zero position and / or in an end point.

The desired value, in particular in addition to the dependence on the basic function f _base (x), is preferably determined as a function of a current vehicle speed. Ie. the setpoint curve is preferably speed-dependent with A _setpoint = f (x, v). This makes it possible, in particular, to set a direct steering ratio required at low vehicle speed and an indirect steering ratio at high vehicle speeds for a pleasant driving feel.

Preferably, the desired value, in particular in addition to the dependence on the _base function f _base (x), determined in dependence on the current target size, wherein in a method for controlling a steering actuator of a motor vehicle, in particular a two-lane motor vehicle, such as a handicapped vehicle, the desired value is determined as a function of the current wheel steering angle (RLW). Ie. In a motor vehicle, the current wheel steering angle preferably forms the desired value, ie, preferably, A _setpoint = f (x, RLW). As a result, with a corresponding definition of the setpoint curve, a setpoint-dependent positional shift of the zero position can be achieved which, as a result, effects a smaller gradient of the setpoint curve profile and thus of the steering ratio. This makes it possible, for example, to reduce the sensitivity of the steering input device in the range of larger input values, so that, for example, in the range of larger input values a larger steering movement is required to trigger the same steering movement as in the range of smaller input values.

However, the setpoint value is particularly preferably determined as a function of a current vehicle speed and as a function of the current setpoint value, with a change in the vehicle speed preferably resulting in a constant setpoint value given a constant input value.

From the prior art is basically known to control the steering actuator depending on a vehicle speed and in particular to change the steering ratio speed-dependent. However, in a steering system with a variable only on the vehicle speed variable steering ratio, a change in speed at a constant input value, for example when driving through a curve with a constant radius usually leads to a change in the steering ratio, so that the constant radius is left or a corrective steering movement to compensate for the speed change is required to hold the radius.

With a setpoint curve, however, in which the setpoint value is determined as a function of a current vehicle speed and as a function of the current setpoint and in which a change in the vehicle speed at a constant input value results in a constant setpoint, this can be avoided, so that a pure speed change no steering movement triggers. Only a change of the input value causes a steering movement.

mit D = [A_v – A_RLW]

wobei v die aktuelle Geschwindigkeit, v_max die maximale Geschwindigkeit, RLW die Sollgröße, k ein Gewichtungsfaktor für den Geschwindigkeitseinfluss und l ein Gewichtungsfaktor für die Sollgröße RLW ist.A setpoint curve A _setpoint = f (x, v, RLW)), which is defined as follows, has proved particularly advantageous.

with D = [A _{v -A RLW} ]

where v is the current speed, v _{max is} the maximum speed, RLW is the setpoint, k is a weighting factor for the speed influence, and l is a weighting factor for the setpoint RLW.

Of course, additional sizes can be used to determine the setpoint in addition to account for additional influences, such. As the (weather-related) Fahrbahnreibwert, the tire inflation pressure, the loading condition or the like.

For applications without the detection of the current setpoint, a virtual setpoint can also be generated, preferably with a programmable attenuation. Ie. The nominal value can also be calculated (virtual) instead of being measured.

The use of a parameterizable damping in this case has the particular advantage that the effect that the actuator or the actuators, such as the front wheels of a vehicle, in principle, slightly delayed respond to the steering input, so that the steering movement caused the steering input always trailing, imitated particularly well can be and thus a particularly accurate virtual target size can be generated. This is advantageous above all in steering systems without feedback of the position of the steering actuator or without feedback of the current setpoint.

The inventive method is in principle suitable for all generic steering systems of vehicles. In particular, however, it is suitable for use in vehicles for the disabled and for steering systems in which a precise operability over a longer period is required and / or in which the driver is subjected to strong movements of the vehicle and thus disturbing vehicle accelerations, such as in off-road vehicles or construction machinery.

The inventive method allows long, relaxed straight ahead without the driver strenuous constant steering corrections on long, straight stretches, especially at high speeds. Furthermore, the method according to the invention also enables precise and therefore fatigue-free steering even in the range of larger input values.

Since the danger of unintentional, to be corrected steering movements is reduced by the setpoint curve according to the invention, the risk of "swinging" of the vehicle by low, fast steering inputs, in particular due to an unintentional, to be corrected steering input, can be reduced with the inventive method.

If the setpoint value is determined in a suitable form as a function of the current setpoint size, the resulting "quasi-extended steering path", i. H. by the resulting reduced sensitivity of the steering input device, the Fahrzeugbeherrschbarkeit be significantly improved. In particular, the steering of the vehicle is simplified, i. H. a precise steering requires less, especially lower motor skills.

Of course, the inventive method can also be used in systems for focusing optical components or the like. Ie. With a method according to the invention, any actuators can be steered, in particular precisely positioned.

An inventive steering system is characterized in that it is designed for carrying out a method according to the invention. Ie. Preferably, the steering system is designed to deposit at least one above-described setpoint curve according to the invention, with particular preference for corresponding parameters being able to be stored.

In a preferred embodiment, a set of parameters can be stored. Ie. Preferably, several parameter sets or several setpoint curves can be stored.

Depending on the intended use of the associated vehicle or the steering system, it may be useful to be able to switch between the individual, stored setpoint curves during operation, for example by means of an operator switch operable by the driver, or to provide only a one-time configuration by an expert, for example in the context of adapting a disabled vehicle to the specific physical limitations of a physically disabled driver.

In a preferred refinement, the steering system has at least one gyrosensor and / or one acceleration sensor for determining further, additional influencing variables, in particular for determining the current vehicle speed, preferably several, in particular at least one 3D acceleration sensor.

Preferably, the steering system is designed such that the desired value is also determined at least as a function of a detected acceleration for error compensation and / or for damping a steering input applied by the driver, in particular as a function of a detected lateral and / or longitudinal acceleration. In this way, for example, due to acting on the vehicle accelerations undesirable steering movements are calculated out and thus compensated and / or attenuated, preferably to the setpoint a scalable, dependent on the detected acceleration correction value is added or subtracted from the setpoint.

A vehicle according to the invention is characterized in that it has a steering system according to the invention.

All the features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the respectively indicated combination but also in other combinations or alone.

Some of the features or properties mentioned relate both to a method according to the invention and to a steering system according to the invention and to a vehicle according to the invention. Some of these features and properties are described only once, but apply independently in the context of technically feasible and useful embodiments both for a method according to the invention and for a steering system according to the invention and for a vehicle according to the invention.

In the following the invention with reference to several preferred embodiments will be further explained, the invention being schematically illustrated in the accompanying drawings. Show it:

1 A first embodiment of a setpoint curve according to the invention,

2 A second embodiment of a setpoint curve according to the invention,

3 A third embodiment of a setpoint curve according to the invention,

4 A fourth embodiment of a setpoint curve according to the invention,

5 A fifth embodiment of a setpoint curve according to the invention,

6a a first exemplary embodiment of a setpoint curve according to the invention for a vehicle speed v = 100 km / h for a wheel angle RLW which sets as a result of an input value of x = 3 set by the driver

6b the setpoint curve according to the invention 6a , also at a vehicle speed v = 100 km / h, but for a wheel steering angle RLW which sets as a result of an input value of x = -105 applied by the driver.

6c the desired value curve according to the invention from the 6a and 6b also at a vehicle speed v = 100 km / h, in this case for a wheel steering angle RLW, which is set as a result of an input value of x = -209 set by the driver.

6d the desired value curve according to the invention from the 6a to 6c , also at a vehicle speed v = 100 km / h, for a wheel steering angle RLW which sets as a result of an input value of x = -302 set by the driver,

6e the desired value curve according to the invention from the 6a to 6d , also at a vehicle speed v = 100 km / h, for a wheel steering angle RLW which sets as a result of an input value of x = -392 applied by the driver,

7a the desired value curve according to the invention from the 6a to 6e , at a wheel steering angle RLW which sets as a result of an input value of x = -209 applied by the driver, but at a vehicle speed of v = 0 km / h,

7b the desired value curve according to the invention from the 6a to 6e and 7a , also at a wheel steering angle RLW which sets as a result of an input value of x = -209 set by the driver, but at a vehicle speed of v = 51 km / h,

7c the desired value curve according to the invention from the 7a and 7b , but at a vehicle speed of v = 100 km / h (see. 6c )

7d the desired value curve according to the invention from the 7a to 7c , but at a vehicle speed of v = 150 km / h and

7e the desired value curve according to the invention from the 7a to 7d , at a vehicle speed of v = 200 km / h.

1 shows a first embodiment of a setpoint curve A _target = f (x) for controlling a steering actuator for adjusting a Radlenkwinkels RLW on the wheels of the front axle as part of a steer-by-wire steering system in a disabled vehicle, as a steering input device to the right and left movable joystick is provided.

= {x_min ... x_max} gebildeten Menge an Eingabewerten repräsentiert, d. h. es gilt x ∊

In the 1 Exemplary setpoint curve A _Soll = f (x) according to the invention, with which a very harmonious steering behavior and also for a handicapped person good vehicle control is enabled, is defined in this case by the basis function f _base (x), ie A _setpoint = f (x) = f _basis (x). The basic function f _base (x) forming the setpoint curve A _setpoint = f (x) is a function dependent on an input value x, where x is an input value applied to a steering input device of an associated steering system according to the invention from a predefined steering input range

= {x _min ... x _max } represents the amount of input values formed, ie x ε

d. h. der Lenkeingabebereich

reicht bei diesem Ausführungsbeispiel von x_min = –392 bis x_max = 392. Dies ist jedoch vom zugehörigen Lenksystem abhängig. In diesem Fall sind Eingabewerte x von x_min = –392 bis x = 0 einer Lenkrichtung nach links zugeordnet, während Eingabewerte x von x = 0 bis x_max = 392 einer Lenkrichtung nach rechts zugeordnet sind. Ein Eingabewert von x_min = –392 entspricht dabei einem Lenkeinschlag nach links von 100% und einem Radlenkwinkel RLW von –100%. Ein Eingabewert von x_max = 392 entspricht einem Lenkeinschlag nach rechts von 100% und einem Radlenkwinkel RLW von 100%.In the embodiment shown, the entire steering input range is defined by

ie the steering input area

ranges from x _min = -392 to x _max = 392 in this embodiment. However, this depends on the associated steering system. In this case, input values x from x _min = -392 to x = 0 are assigned to a steering direction to the left, while input values x from x = 0 to x _max = 392 are assigned to a steering direction to the right. An input value of x _min = -392 corresponds to a steering angle to the left of 100% and a wheel steering angle RLW of -100%. An input value of x _max = 392 corresponds to a steering angle of 100% to the right and a wheel steering angle RLW of 100%.

D. h., The joystick is moved by the driver to the left, for example, to an input value of x = -200, depending on this input value x by means of the setpoint curve A _target = f (x) according to the invention, which in this case by the basic function f _Basis (x) is formed, the associated setpoint A _{setpoint determined} to control the steering actuator of the steering system in order to set the desired _target size, in this case the desired wheel steering angle RLW the front wheels.

und

zusammengesetzt, wobei die Basis-Sollkurvensegmente

und

dabei jeweils Parabelsegmente sind.The basis function f _basis (x), which in the in 1 shown Auführunsgbeispiel a setpoint curve A _Soll = f (x) the setpoint curve A _Soll = f (x) forms, ie A _setpoint = f (x) = f _basis (x), is from five base setpoint curve segments

and

composed, wherein the base target curve segments

and

each parabolic segments are.

und

definieren mit p_min = (x_min; y_min), p ' / 2 = (x ' / 2; y ' / 2), p ' / 1 = (x ' / 1; y ' / 1), p₁ = (x₁; y₁), p₂ = (x₂; y₂) und p_max = (x_max; y_max).In the 1 Setpoint curve A _setpoint = f (x) or the basic function f _base (x) forming the setpoint curve A _setpoint = f (x) runs through the points p _min , p '/ 2, p' / 1, p ₁ , p ₂ and p _max , the points p _min , p '/ 2, p' / 1, p ₁ , p ₂ and p _max the range limits of the individual parabolic segments

and

define with p _min = (x _min ; y _min ), p '/ 2 = (x' / 2; y '/ 2), p' / 1 = (x '/ 1; y' / 1), p ₁ = (x ₁ ; y ₁ ), p ₂ = (x ₂ ; y ₂ ) and p _max = (x _max ; y _max ).

und

sowie die beiden Parabelsegmente

und

derart tangential ineinander über, dass sich ein harmonischer, polstellenfreier Sollwertkurvenverlauf ergibt. Dabei gehen die beiden Parabelsegmente

und

im Punkt p ' / 2 tangential ineinander über, während die beiden Parabelsegmente

und

im Punkt p₂ tangential ineinander übergehen, d. h. es gilt:

und

According to the invention, in each case the directly adjoining, adjacent parabolic segments

and

as well as the two parabolic segments

and

such tangential into each other that results in a harmonic, polstellenfreier setpoint curve. Here are the two parabolic segments

and

at the point p '/ 2 tangentially into each other, while the two parabolic segments

and

pass tangentially into one another at the point p ₂ , that is to say:

and

und

zugeordnet sind und der Lenkrichtung nach rechts die Parabelsegmente

und

Das fünfte Basissegment f_{Basis,Totband} definiert ein symmetrisches Totband um die Nullposition, d. h. um x = 0, wodurch ein besonders harmonisches Anlenkverhalten erreicht werden kann.In this Ausfünrungsbeispiel each steering direction, ie, both the steering direction to the left, and the steering direction to the right, each associated with two parabolic segments, the steering direction to the left the parabolic segments

and

are assigned and the steering direction to the right of the parabolic segments

and

The fifth base segment f _{base, deadband} defines a symmetrical dead band around the zero position, ie around x = 0, whereby a particularly harmonious articulation behavior can be achieved.

und einem sich daran anschließenden, zweiten, nach unten geöffneten Parabelsegment

zusammengesetzt und im ersten Quadranten aus einem dritten nach oben geöffneten Parabelsegment

und einem sich daran anschließenden, vierten nach unten geöffneten Parabelsegment

Das Totband ist dabei zwischen dem zweiten, nach unten geöffneten Parabelsegment

und dem dritten, nach oben geöffneten Parabelsegment

angeordnet.Starting from a smallest possible input value x _min = -392 in the direction of the largest possible input value x _max = 392, the _base function f _base (x) in the third quadrant, based on a Cartesian coordinate system as in this case, consists of a first, upwardly opened parabola segment

and a subsequent, second, downwardly open parabolic segment

composed and in the first quadrant of a third upwardly open parabolic segment

and a subsequent, fourth downwardly open parabolic segment

The deadband is between the second, downwardly open parabolic segment

and the third, upwardly opened parabolic segment

arranged.

und

bzw. die Parabelsegmente

und

tangential ineinander über, sondern bei diesem Ausführungsbeispiel gehen auch jeweils die sich an das Totband f_{Basis,Totband} anschließenden Parabelsegmente

und

tangential in das Totband f_{Basis,Totband} über, d. h. es gilt außerdem:

f ' / Basis,Totband(x ' / 1) und f ' / Basis,Totband(x₁) =

It's not just the adjacent parabolic segments

and

or the parabolic segments

and

tangentially into each other, but in this embodiment also go to each of the deadband f _{base, dead band} subsequent parabola _segments

and

tangential in the deadband f _{base, deadband} above, ie it also applies:

f '/ base, deadband (x' / 1) and f '/ base, deadband (x ₁ ) =

bzw.

jeweils tangential in die Endpunkte p ' / 1 bzw. p₁ des Totbandes f_{Basis,Totband} ein. Demzufolge liegt der Scheitelpunkt S_III-1 bzw. S_I-1 der jeweils zugehörigen Parabel, welche jeweils das betreffende Parabelsegment

bzw.

definiert, jeweils im zugehörigen Endpunkt p ' / 1 bzw. p₁ des Totbandes f_{Basis,Totband}, d. h. im Punkt p ' / 1 bzw. p₁, was in 1 für das Parabelsegment

durch den mit dem Dreieck markierten Punkt S_I-1 beispielhaft gezeigt ist.Ie. in this case the two parabolic segments immediately following the deadband run

respectively.

each tangent to the endpoints p '/ 1 or p _{1 of} the deadband f _{base, dead band} . As a result, the vertex S _III-1 or S _{I-1 of} the respective associated parabola, which in each case the parabola segment concerned

respectively.

defined, in each case in the associated endpoint p '/ 1 or p _{1 of} the deadband f _{basis, deadband} , ie at the point p '/ 1 or p ₁ , which is in 1 for the parabolic segment

is exemplified by the point S _I-1 marked with the triangle.

= f ' / Basis,Totband(x ' / 1) = f ' / Basis,Totband(x₁) =

= 0.As a result, the slope is at the transition point p '/ 1 or p ₁ in this case in each case zero, ie it applies

= f '/ base, deadband (x' / 1) = f '/ base, deadband (x ₁ ) =

= 0.

= {x ' / 1 ... x₁} in die daran angrenzenden, benachbarten, den Parabelsegmenten

bzw.

zugeordneten Lenkbereiche

= {x ' / 2 ... x ' / 1} bzw.

= {x₁ ... x₂} möglich ist. In Fahrversuchen hat sich gezeigt, dass bis zu einem Betrag einer Steigung von |f ' / Basis(x ' / 1)| ≤ 1 bzw. |f ' / Basis(x₁)| ≤ 1 von ein harmonisches Anlenkverhalten erreicht werden kann.As a result, a particularly harmonious articulation behavior, which is perceived as pleasant, can be achieved because a particularly soft transition from the deadband f _{base, dead band} or from the deadband f _{base, dead band} associated steering range

= {x '/ 1 ... x ₁ } into the adjacent, adjacent, the parabolic segments

respectively.

assigned steering ranges

= {x '/ 2 ... x' / 1} respectively.

= {x ₁ ... x ₂ } is possible. In driving tests it has been shown that up to an amount of a slope of | f '/ base (x' / 1) | ≤ 1 respectively. | f '/ base (x ₁ ) | ≤ 1 of a harmonious Anlenkverhalten can be achieved.

This results in the in 1 illustrated, setpoint curve according to the invention A _Soll = f (x) = f _base (x) or the underlying basis function f _base (x) to:

und

d. h. die Punkte p_min, p ' / 2, p ' / 1, p₂ und p_max, dabei derart gewählt, dass x₂ genau in der Mitte zwischen x₁ und x_max liegt und entsprechend x ' / 2 genau in der Mitte zwischen x_min und x ' / 1, d. h. es gilt:

At the in 1 Embodiment shown are the range limits of the individual basic setpoint curve segments

and

ie the points p _min , p '/ 2, p' / 1, p ₂ and p _max , chosen such that x _{2 is} exactly in the middle between x ₁ and x _max and accordingly x '/ 2 right in the middle between x _min and x '/ 1, ie it applies:

Furthermore, the basic function f _base (x) in this exemplary embodiment is point-symmetrical around the zero point, ie formed around p (x = 0, y = 0), ie x _min = -x _max , y _min = -y _max x ₂ = -x '/ 2, y ₂ = -y' / 2, x ₁ = -x '/ 1, y ₁ = -y' / 1.

und

den gleichen Betrag des Stauchungsfaktor p auf, d. h. gilt außerdem |p_III-2| = |p_III-1| = |p_I-1| = |p_I-1|, kann auf besonders einfache Art und Weise erreicht werden, dass jeweils die unmittelbar aneinander angrenzenden, benachbarten Parabelsegmente

und

sowie die beiden Parabelsegmente

und

erfindungsgemäß tangential ineinander übergehen, so dass sich ein harmonischer, polstellenfreier Sollwertkurvenverlauf ergibt.Also assign all four parabolic segments

and

the same amount of compression factor p, ie, | p _III-2 | = | p _III-1 | = | p _I-1 | = | p _I-1 |, can be achieved in a particularly simple way, that in each case the directly adjacent, adjacent parabolic segments

and

as well as the two parabolic segments

and

according to the invention tangentially merge into each other, so that there is a harmonic, polstellenfreier setpoint curve.

For the individual points p ₁ , p ₂ and p _max and the compression factors p _{I-1, the} following applies:
p _max = (x _max = 392; y _max = 408)
p ₂ = (x ₂ = 225, y ₂ = 204)
p ₁ = (x ₁ = 58; y ₁ = 0)
p _I-1 = 0.007315

= {x ' / 1 = –58 ... x₁ = 58}. Das sich im ersten Quadranten Q_I an das Totband f_{Basis,Totband} anschließende Parabelsegment

erstreckt sich entsprechend über einen Lenkeingabebereich von

= {x₁ = 58 ... x₂ = 225} und das sich im dritten Quadranten Q_III an das Totband f_{Basis,Totband} anschließende Parabelsegment

erstreckt sich über ein Lenkeingabebereich

= {x ' / 1 = –58 ... x ' / 2 = –225}. Die weiter außenliegenden Parabelsegmente

und

erstrecken sich entsprechend über einen Lenkeingabebereich

= {x_min = –392 ... x ' / 2 = –225} bzw.

= {x₂ = 225 ... x_max = 392}.D. h., The deadband f _{base, dead band} extends over a steering _input range

= {x '/ 1 = -58 ... x ₁ = 58}. The in the first quadrant Q _I to the deadband f _{base, dead band} subsequent parabola _segment

extends accordingly over a steering input range of

= {x ₁ = 58 ... x ₂ = 225} and that in the third quadrant Q _III to the deadband f _{base, dead band} subsequent parabola _segment

extends over a steering input area

= {x '/ 1 = -58 ... x' / 2 = -225}. The more external parabolic segments

and

extend accordingly over a steering input area

= {x _min = -392 ... x '/ 2 = -225} respectively.

= {x ₂ = 225 ... x _max = 392}.

With x _min = -x _max , y _min = -y _max , x ₂ = -x '/ 2, y ₂ = -y' / 2, x ₁ = -x '/ 1, y ₁ = -y' / 1 as well as | p _III-2 | = | p _III-1 | = | p _I-1 | = | p _I-1 | and S _III-2 = p _min , S _III-1 = p '/ 1, S _I-1 = p ₁ and S _I-2 = p _max results for the setpoint curve

2 shows an alternative embodiment of a desired value curve A _Soll = f (x) = f _basis (x) according to the invention, which is formed by a basic function f _basis (x) according to the invention, in which case:
p _max = (x _max = 392; y _max = 408)
p ₂ = (x ₂ = 207; y ₂ = 204)
p ₁ = (x ₁ = 22; y ₁ = 0)
p _I-1 = 0.005961

As with the in 1 Embodiment shown are also in the in 2 setpoint curve A _setpoint = f (x) = f _basis (x) the vertices S _I-1 and S _III-1 respectively in the end point of the deadband f _{base, dead band} and the vertices S _I-2 and S _III-2 respectively in the Points p _max and p _min , where also: x _min = -x _max , y _min = -y _max , x ₂ = -x '/ 2, y ₂ = -y' / 2, x ₁ = -x '/ 1, y ₁ = -y' / 1 as well as | p _III-2 | = | p _III-1 | = | p _I-1 | = | p _I-1 | and S _III-2 = p _min , S _III-1 = p '/ 1, S _I-1 = p ₁ and S _I-2 = p _max . The deadband f _{base, dead band} is only narrower in this case. With the aforementioned parameter values, the invention results in 2 setpoint curve A _setpoint = f (x) = f _basis (x) consequently to:

und

jedoch nicht tangential in das Totband f_Basis(x) bzw. in die Punkte p ' / 1 und p₁ ein bzw. aus diesen heraus. 3 shows a further alternative embodiment of a setpoint curve according to the invention A _Soll = f (x) = f _base (x), in which the setpoint curve A _Soll = f (x) is also formed by a _base function f _basis (x) according to the invention. In this case, the parabolic segments run

and

but not tangentially in the deadband f _basis (x) or in the points p '/ 1 and p _{1 in} and out of these.

des Parabelsegmentes

liegt in diesem Fall nämlich bei

= (S_x,I-1 = –222; S_y,I-1 = –111). Darüber hinaus liegt der Punkt p₁ bei p₁ = (x₁ = 37; y₁ = 0) und der Punkt p₂ bei p₂ = (x₂ = 215; y₂ = 204) und der Stauchungsfaktor des Parabelsegmentes

beträgt p_I-1 = 0,0016533.The vertex

of the parabolic segment

is in fact in this case

= (S _{x, I-1} = -222, S _{y, I-1} = -111). In addition, the point p _{1 is} at p ₁ = (x ₁ = 37, y ₁ = 0) and the point p ₂ at p ₂ = (x ₂ = 215, y ₂ = 204) and the compression factor of the parabola segment

p is _I-1 = 0.0016533.

With p _max = (x _max = 392, y _max = 408), x _min = -x _max , y _min = -y _max , x ₂ = -x '/ 2, y ₂ = -y' / 2, x ₁ = -x '/ 1, y ₁ = -y' / 1 as well as | p _III-2 | = | p _III-1 | = | p _I-1 | = | p _I-1 |, S _III-1 = (-S _{x, I-1} ; -S _{y, I-1} ) and S _I-2 = (x _max + x _{1 -Sx, I-1} ; y _max - S _{y, I-1} ) as well as S _III-2 = (-S _{x, I-2} ; -S _{y, I-2} ) is given correspondingly for A _setpoint = f (x) = f _basis (x) :

= (S_x,I-1 = –83; S_y,I-1 = –54)
p_max = (x_max = 392; y_max = 408)
p₂ = (x₂ = 225; y₂ = 204)
p₁ = (x₁ = 58; y₁ = 0)
p_I-1 = 0,002725 4 shows a fourth embodiment of a setpoint curve according to the invention A _Soll = f (x) = f _basis (x), wherein the basis function f _basis (x) is defined by the following parameters:

= (S _{x, I-1} = -83; S _{y, I-1} = -54)
p _max = (x _max = 392; y _max = 408)
p ₂ = (x ₂ = 225, y ₂ = 204)
p ₁ = (x ₁ = 58; y ₁ = 0)
p _I-1 = 0.002725

With x _min = -x _max , y _min = -y _max , x ₂ = -x '/ 2, y ₂ = -y' / 2, x ₁ = -x '/ 1, y ₁ = -y' / 1 as well as | p _III-2 | = | p _III-1 | = | p _I-1 | = | p _I-1 |, S _III-1 = (-S _{x, I-1} ; -S _{y, I-1} ) and S _I-2 = (x _max + x _{1 -Sx, I-1} ; y _max - S _{y, I-1} ) as well as S _III-2 = (-S _{x, I-2} ; -S _{y, I-2} ) the A _setpoint = f (x) = f _basis (x) results :

In addition to the previous exemplary embodiments shown, the associated tangent is shown at point p ₁ in this illustration in order to clarify the slope of the basis function f _base (x). The slope is m (x ₁ ) = 0.76 with m = f '/ base (x), ie the slope at this point p ₁ is still <= 1 and thus smaller than the slope of a 45 ° straight line. This allows a particularly pleasant steering behavior can be achieved from the deadband out.

Of course, it is also possible for the individual parabolic segments of the base function f _base (x) does not indicate as described in the apex mold, in applying to the parabola f _base (x) = p (x - S _x) ² + S _v, but for example, in the parameter form f _basis (x) = ax ² + bx + c, where:

Since the conversion of the coefficients between the respective forms for defining a parabola, for example for converting the coefficients of the vertex shape into the coefficients of the parameter form, should be known to the person skilled in the art from school mathematics, this will not be discussed here and will be attributed to corresponding mathematics textbooks referenced this topic.

und

in der Form f_Basis(x) = ax² + bx + c definiert, kann eine besonders einfache Parametrierung erfolgen, d. h. eine besonders einfache Bedatung, wenn die drei Koeffizienten a, b und c für die einzelnen Parabelsegmente

und

jeweils in Abhängigkeit dreier Punkte, durch welche das Parabelsegment verlaufen soll, ermittelt werden, wobei die drei Punkte vorzugsweise derart gewählt werden, dass jeweils ein erster Punkt den Anfang des jeweiligen Parabelsegments definiert, jeweils ein zweiter Punkt das Ende des betreffenden Parabelsegmentes und der dritte Punkt zur Einstellung der Krümmung des jeweiligen Parabelsegmentes verwendet wird.Become the parabolic segments

and

defined in the form f _basis (x) = ax ² + bx + c, a particularly simple parameterization can take place, ie a particularly simple calculation if the three coefficients a, b and c for the individual parabolic segments

and

are respectively determined as a function of three points through which the parabola segment is to run, the three points preferably being selected such that in each case a first point defines the beginning of the respective parabola segment, in each case a second point the end of the parabolic segment concerned and the third point is used to adjust the curvature of the respective parabolic segment.

gezeigt, wobei das Parabelsegment

durch die drei Punkte p₁ = (x₁ = 58; y₁ = 0), p₂ = (x₂ = 225; y₂ = 204) und p_k = (x_k = 142; y_k = 83) definiert ist, aus denen sich für die Koeffizienten a, b und c folgende Werte ergeben: a = 0,002725, b = 0,7665 und c = 0.This is exemplary in 4 for the parabolic segment

shown, the parabolic segment

is defined by the three points p ₁ = (x ₁ = 58; y ₁ = 0), p ₂ = (x ₂ = 225, y ₂ = 204) and p _k = (x _k = 142; y _k = 83) , from which the following values result for the coefficients a, b and c: a = 0.002725, b = 0.7665 and c = 0.

und definiert somit eine linke Bereichsgrenze x₁ sowie einen der linken Bereichsgrenze x₁ zugeordneten Sollwert y₁, während der Punkt p₂ das Ende des Parabelsegmentes

definiert und damit eine rechte Bereichsgrenze x₂ des Eingabewertes x sowie einen der rechten Bereichsgrenze x₂ zugeordneten Sollwert y₂. Mit dem Punkt p_k, d. h. insbesondere durch Verändern des Punktes p_k kann die Krümmung des Parabelsegmentes

eingestellt werden. Wird beispielsweise für einen definierten Eingabewert x_k der zugehörige Sollwert y_k kleiner gewählt, wie beispielsweise bei der in 5 dargestellten Basisfunktion f_Basis(x), welche durch die gleichen Punkte p_min, p ' / 2, p ' / 1, p₁, p₂ und p_max definiert ist, wie die in 4 gezeigte Basisfunktion f_Basis(x) und sich jeweils nur in der Krümmung der einzelnen Parabelsegmente

und

von dieser unterscheidet, wandert der Punkt p_k nach unten, die Krümmung des Parabelsegmentes

nimmt zu. Wählt man hingegen den Sollwert y_k größer, wandert der Punkt p_k nach oben, die Krümmung des Parabelsegmentes

nimmt ab. Dabei sollte die y-Koordinate, d. h. der Sollwert y_k, nicht oberhalb oder auf einer durch die Punkte p₁ und p₂ verlaufenden Geraden liegen.As based on 4 The point p _{1 forms} the beginning of the parabolic segment

and thus defines a left range limit x _1, and a left border region x ₁ associated desired value y _1, while the point p _2, the end of the parabolic segment

defines and thus a right range limit x _{2 of} the input value x and a right range limit x ₂ associated setpoint y ₂ . With the point p _k , ie in particular by changing the point p _k , the curvature of the parabola segment

be set. If, for example, the associated desired value y _{k is selected to be} smaller for a defined input value x _k , as is the case, for example, in FIG 5 represented basis function f _basis (x), which by the same points p _min , p '/ 2, p' / 1, p ₁ , p ₂ and p _max is defined as the in 4 basic function f _basis (x) and each only in the curvature of the individual parabolic segments

and

from this, the point p _k moves downwards, the curvature of the parabola segment

is increasing. On the other hand, if one selects the setpoint value y _k , the point p _k moves upward, the curvature of the parabolic segment

decreases. In this case, the y-coordinate, ie the desired value y _k , should not be above or on a straight line passing through the points p ₁ and p ₂ .

und

von der in 4 dargestellten Basisfunktion f_Basis(x) unterscheidet, denn der Punkt p_k der in 5 dargestellten Basisfunktion liegt bei p_k = (x_k = 142; y_k = 51).As already explained above, shows 5 an inventive, defined by a basis function f _basis (x) setpoint curve by the same points p _min , p '/ 2, p' / 1, p ₁ , p ₂ and p _max is defined as the in 4 basic function f _basis (x) shown and which in each case only in the curvature of the individual parabolic segments

and

from the in 4 _basis (x) differs, because the point p _k of in 5 is represented by p _k = (x _k = 142, y _k = 51).

= (S_x,I-1 = 58; S_y,I-1 = 0) und
mit x_min = –x_max, y_min = –y_max, x₂ = –x ' / 2, y₂ = –y ' / 2, x₁ = –x ' / 1, y₁ = –y ' / 1 sowie |p_III-2| = |p_III-1| = |p_I-1| = |p_I-1| und S_III-2 = p_min, S_III-1 = p ' / 1, S_I-1 = p₁ und S_I-2 = p_max gilt entsprechend für die Sollwertkurve A_Soll = f(x) = f_Basis(x) aus 5:

With
a = 0.002725
b = 0
c = 0

= (S _{x, I-1} = 58, S _{y, I-1} = 0) and
with x _min = -x _max , y _min = -y _max , x ₂ = -x '/ 2, y ₂ = -y' / 2, x ₁ = -x '/ 1, y ₁ = -y' / 1 as well as | p _III-2 | = | p _III-1 | = | p _I-1 | = | p _I-1 | and S _III-2 = p _min , S _III-1 = p '/ 1, S _I-1 = p ₁ and S _I-2 = p _max apply correspondingly to the setpoint curve A _setpoint = f (x) = f _basis (x) off 5 :

mit y_k = 51 kleiner gewählt als der dem gleichen Eingabewert x_k des Punktes p_k zugeordnete Sollwert y_k der in 4 gezeigten Basisfunktion f_Basis(x) mit y_k = 83, wodurch sich bei der in 5 dargestellten Basisfunktion f_Basis(x) eine größere Krümmung des Parabelsegmentes

einstellt und damit auch der übrigen Parabelsegmente

welche aufgrund eines sich daraus ergebenden vorteilhaften Lenkverhaltens die gleiche Krümmung aufweisen, wie das Parabelsegment

Thus, the the input value x _k of the point p _k assigned setpoint value y _k is in the in 5 basic function shown f _base (x) for adjusting the curvature of the parabola segment

with y _k = 51 selected smaller than the setpoint value y _{k associated with} the same input value x _{k of} the point p _k 4 _base function (x) with y _k = 83, which results in the in 5 _base function (f) shows a greater curvature of the parabolic segment

adjusts and thus the other parabolic segments

which due to a resulting advantageous steering behavior have the same curvature, as the parabolic segment

wobei bei diesem Ausführungsbeispiel gilt:
l = 10
k = 0,3180
und

= (S_x,I-1 = 26; S_y,I-1 = –5)
p_max = (x_max = 392; y_max = 408)
p₂ = (x₂ = 225; y₂ = 204)
p₁ = (x₁ = 58; y₁ = 0)
p_I-1 = 0,005307
d. h. für die Basisfunktion gilt:

6a shows a further embodiment of a setpoint curve according to the invention A _Soll = f (x), in which case the setpoint curve A _Soll = f (x) However, not only by the input value x dependent _base function f _base (x) is formed, but also in dependence is defined as a vehicle speed v and as a function of a current wheel steering angle RLW, ie, A _setpoint = f (x, v, RLW) with:

wherein in this embodiment:
l = 10
k = 0.3180
and

= (S _{x, I-1} = 26; S _{y, I-1} = -5)
p _max = (x _max = 392; y _max = 408)
p ₂ = (x ₂ = 225, y ₂ = 204)
p ₁ = (x ₁ = 58; y ₁ = 0)
p _I-1 = 0.005307
ie for the basis function applies:

By means of such a desired value curve A _{target, v, RLW} = f (x, v, RLW) results in a particularly pleasant steering feel, firstly with increasing vehicle speed v of the gradient, ie the slope of the setpoint curve A _{target, v, RLW} = f (x, v, RLW) decreases, ie the target value curve A _{target, v, RLW} = f (x, v, RLW) becomes flatter with increasing vehicle speed v, so that the same change of the input value x at lower vehicle speeds v a smaller change of Target value A _{target has} the consequence, as at a lower vehicle speed v.

On the other hand, by taking into account the current wheel steering angle RLW arithmetically in the range of larger input values x, the sensitivity of the steering input device can be reduced, so that in the range of larger input values x a greater steering movement is required to trigger the same steering movement as in the range of smaller input values x. Furthermore, with a corresponding definition of the setpoint curve A _{setpoint, v, RLW} = f (x, v, RLW), a setpoint-dependent positional shift of the zero position A _setpoint (x = 0) can be achieved, which likewise results in a smaller gradient of the setpoint curve profile and thus the steering ratio causes.

By the combined consideration of the current vehicle speed v and the current wheel steering angle RLW can be achieved that a change in the vehicle speed v at a constant input value x does not lead to a change in the wheel steering angle RLW, ie the target value A _target remains constant despite a change in the vehicle speed v if the input value x remains constant.

The influence of the wheel steering angle RLW on the setpoint curve A _{target, V, RLW} = f (x, v, RLW) is calculated using the 6a to 6e clearly, which in each case the course of the setpoint curve A _{target, v, RLW} = f (x, v, RLW) at constant vehicle speed v = 100 km / h, but each with different current wheel steering angles RLW show. Based on this 6a to 6e In each case, it is easy to see how the currently resulting setpoint value A _{setpoint changes} as a function of the current wheel steering angle RLW, wherein the current setpoint value A _{setpoint is} in each case determined by the setpoint curve A _{setpoint, v, RLW} = f (x, v, RLW) and the dashed line to illustrate the current wheel steering angle RLW formed intersection lies.

6a shows the previously described desired value curve A _{target, v, RLW} = f (x, v, RLW) at a vehicle speed of v = 100 km / h for a set as a result of an input value of x = 3 adjusting the wheel steering angle RLW.

6b shows the setpoint curve according to the invention 6a , also at a vehicle speed v = 100 km / h, but for a wheel steering angle RLW which sets as a result of an input value of x = -105 applied by the driver. The change of the functions A _v , A _RLW entering into the calculation of the setpoint curve A _{setpoint, v, RLW} = f (x, v, RLW) and the resulting difference function D as a function of the current wheel steering angle RLW can be easily recognized.

With a further reduction of the input value x up to an input value of x = -209, ie with a further steering movement to the left, the result in 6c illustrated setpoint curve course, wherein 6c the desired value curve A _{target according to} the invention _{, v, RLW} = f (x, v, RLW) from the 6a and 6b , also at a vehicle speed v = 100 km / h, for a wheel steering angle RLW which sets as a result of an input value of x = -209 applied by the driver.

6d shows according to the invention setpoint curve A _{target, v, RLW} = f (x, v, RLW) from the 6a to 6c , also at a vehicle speed v = 100 km / h, but for a wheel steering angle RLW which sets as a result of an input value of x = -302 applied by the driver.

6e shows the setpoint curve A _{target according to} the invention _{, v, RLW} = f (x, v, RLW) from the 6a to 6d , also at a vehicle speed v = 100 km / h, for a wheel steering angle RLW which is set as a result of an input value of x = -392 applied by the driver, which in this case corresponds to a maximum wheel steering angle RLW, ie a maximum left steering angle.

The influence of the vehicle speed v on the target value curve A _{target, v, RLW} = f (x, v, RLW) is calculated using the 7a to 7e clearly showing each of the course of the setpoint curve A _{target, v, RLW} = f (x, v, RLW) at a constant as a result of an applied by the driver input value of x = -209 adjusting wheel steering angle RLW, but each for different current vehicle speeds v , Based on this 7a to 7e is always good to see that the currently resulting setpoint A _set not changed but constantly bleed, the current setpoint A _set here in each case by the setpoint curve A _{target, v, RLW} = f (x, v, RLW ) and the dashed line to illustrate the current wheel steering angle RLW formed intersection lies.

7a shows the setpoint curve A _target according to the invention _{, v, RLW} = f (x, v, RLW) from the 6a to 6e , at a wheel steering angle RLW that adjusts as a result of an input value of x = -209 applied by the driver, but at a vehicle speed of v = 0 km / h.

7b shows the setpoint curve A _{target according to} the invention _{, v, RLW} = f (x, v, RLW) from the 6a to 6e and 7a , also at a wheel steering angle RLW which sets as a result of an input value of x = -209 applied by the driver, but at a vehicle speed of v = 51 km / h. The change of the functions A _v , A _RLW entering into the calculation of the setpoint curve A _{setpoint, v, RLW} = f (x, v, RLW) and the resulting difference function D as a function of the current vehicle speed v can be clearly recognized.

7c shows the setpoint curve A _{target according to} the invention _{, v, RLW} = f (x, v, RLW) from the 7a and 7b , but at a vehicle speed of v = 100 km / h (see. 6c ).

7d shows the setpoint curve A _{target according to} the invention _{, v, RLW} = f (x, v, RLW) from the 7a to 7c , but at a vehicle speed of v = 150 km / h and 7e shows the setpoint curve A _{target according to} the invention _{, v, RLW} = f (x, v, RLW) from the 7a to 7d , at a vehicle speed of v = 200 km / h.

Of course, a variety of modifications to the illustrated embodiments is possible, in particular the use of other parameter values, ie another Bedatung, as well as the definition the individual parabolic segments of the basis function not in vertex form, but for example in parameter form or other equivalent forms, without departing from the content of the claims.

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 102009014392 A1 [0007]
• DE 102007053818 A1 [0008]

Claims (18)

A method for controlling a steering actuator of a steering system with a steering input device with variable steering ratio in a vehicle, preferably for controlling a steer-by-wire steering system, in particular for controlling a steering system with a joystick as a steering input device, wherein the steering input device is adapted to one of a Driver to determine desired steering movement and wherein the steering actuator is adapted to implement the desired steering movement, wherein in a first step to determine the desired steering movement applied to the steering input device steering input is detected and from an input value (x) is determined, in a second step in dependence on the determined input value (x) on the basis of a predefined setpoint curve (A _setpoint = f (x)), a desired value (A _setpoint ) is determined and in a third step the steering actuator is set with this setpoint value (A _setpoint ) for setting a setpoint variable (RLW ) and thus to the implementation the desired steering movement is controlled, characterized in that the desired value curve (A _target = f (x)), based on which the desired value (A _target ) is determined with which the steering actuator is controlled, from one of a plurality of base target curve segments

composite basis function (f _basis (x)), which depends on the steering input range of a steering direction (

= {x _min ... 0},

= {0 ... x _max }) from at least two base setpoint curve segments

composed, which are parabolic segments and tangentially merge into each other, that results in a harmonic, polstellenfreier setpoint curve. A method according to claim 1, characterized in that the target value curve (A _target = f (x)) in two steering directions, in particular opposite steering directions, of a basic function (f _basis (x)) depends, over the entire steering input range (

= {x _min ... x _max }) from at least four base setpoint curve segments

is composed, wherein preferably each steering direction at least two base target curve segments

are assigned, in particular symmetrically about a zero position. Method according to Claim 1 or 2, characterized in that the setpoint curve (A _setpoint = f (x)) is point-symmetrical with respect to the symmetry point (x = 0; A _setpoint = f (x = 0)). Method according to one of the preceding claims, characterized in that the basis function (f _base (x)) consists of at least four parabolic segments

is composed, in particular of four parabolic segments

second order, wherein the basis function (f _basis (x)), starting from a smallest possible input value (x _min ) in the direction of a maximum input value (x _max ) in the third quadrant (Q _III ) from a first, upwardly open parabola segment

and a subsequent, second, downwardly open parabolic segment

is composed and in the first quadrant (Q _I ) from a third, upwardly open parabolic segment

and a subsequent, fourth, downwardly open parabolic segment

based on a Cartesian coordinate system. Method according to one of the preceding claims, characterized in that the basis function (f _basis (x)) is defined as follows:

in which

the amount of all applicable by means of the steering input device input values x is and x _min , x '/ 2, x' / 1, x ₁ , x ₂ , x _max the range limits of the individual sections of the basic setpoint curve segments

defining, where p, Sx, Sy and the choice of the range limits of the individual sections of the basic setpoint curve segments

are the adjustable parameters for adapting the function, preferably x '/ 1 ≤ 0 and x '/ 2 <0 and x ₁ ≥ 0 and x ₂ > 0 and where

and

Method according to Claim 5, characterized in that the basis function (f _basis (x)) is defined as follows:

where y _min or y _{max is} the minimum or maximum possible setpoint A _setpoint with which the steering actuator is to be controlled at the associated minimum or maximum input value x _min or x _max , where p and the selection of the range limits of the individual Sections of the base setpoint curve segments are the adjustable parameters for adapting the function, wherein preferably x '/ 1 ≤ 0 and x '/ 2 <0 and x ₁ ≥ 0 and x ₂ > 0, and preferably x _min = -x _max and / or y _min = -y _max and / or x ₁ = x '/ 1 and or x ₂ = x '/ 2. Method according to one of the preceding claims, characterized in that at least one basic setpoint curve segment (f _{base, dead band} ) at least partially defines a dead band, wherein the dead band is preferably associated with a region around the zero position of the steering input device and thus forms a dead band around the zero position, in particular a deadband symmetrical about the zero position. Method according to one of the preceding claims, characterized in that the basis function (f _basis (x)) of at least five basic setpoint curve segments

is composed, wherein the basis function (f _base (x)) between the second, downwardly open parabolic segment

and the third, upwardly opened parabolic segment

a base target curve segment (f _{base, dead band} ) defining a deadband. Method according to claim 7 or 8, characterized in that the basis function (f _basis (x)) is defined as follows:

With x ₁ , x '/ 1 ≠ 0. Method according to one of the preceding claims, characterized in that the base function (f _base (x)) enters tangentially with a horizontal tangent to the zero position and / or at least one end point of the dead band and / or at least one end point at the end of the steering input range. Method according to one of the preceding claims, characterized in that an amount of a slope (| f '/ base (x) |) the basis function (f _basis (x)) in at least one transition point (x '/ 2, x' / 1, x ₁ , x ₂ ) between two adjacent, adjacent base setpoint curve segments ≤ 1, preferably at a transition point (x '/ 1, x ₁ ) between a base target curve segment forming a dead band (f _{base, dead band} ) and an adjacent base target curve segment adjacent thereto

Method according to one of the preceding claims, characterized in that the setpoint curve (A _setpoint = f (x)) is defined by the basis function (f _basis (x)). Method according to one of the preceding claims, characterized in that the desired value (A _target ) is determined as a function of a current vehicle speed (v), wherein preferably a change in the vehicle speed (v) at a constant input value (x) a constant desired value (A _Soll ) results. Method according to one of the preceding claims, characterized in that the setpoint value (A _setpoint ) is determined as a function of the current setpoint value (RLW). Method according to claims 13 and 14, characterized in that the target value curve (A _target = f (x, v, RLW)) is determined as a function of the current vehicle speed (v) and in dependence on the current _target value (RLW), wherein preferably, a change in the vehicle speed (v) at a constant input value (x) gives a constant setpoint value (A _setpoint ). A method according to claim 15, characterized in that the desired value curve (A _target = f (x, v, RLW)) is defined as follows:

where v is the current speed, v _{max is} the maximum speed, RLW is the setpoint, k is a weighting factor for the speed influence, and l is a weighting factor for the setpoint RLW. Steering system with variable steering ratio with a steering input device and a steering actuator, wherein the steering system is preferably a steer-by-wire steering system, in particular a steering system with a joystick as steering input device, characterized in that the steering system for carrying out a method according to one of claims 1 to 16 is formed. Vehicle, in particular vehicle for the disabled, with a steering system, characterized in that the steering system is designed according to claim 17.

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