EP1827951A2

EP1827951A2 - Method for guiding a vehicle into a parking space, and parking assistance device

Info

Publication number: EP1827951A2
Application number: EP05850494A
Authority: EP
Inventors: Stefan LÜKE
Original assignee: Continental Teves AG and Co OHG
Current assignee: Continental Teves AG and Co OHG
Priority date: 2004-12-24
Filing date: 2005-12-22
Publication date: 2007-09-05
Also published as: WO2006069976A2; JP4865727B2; JP2008525263A; DE102005062084A1; US20080125939A1; US8065058B2; WO2006069976A3

Abstract

The invention relates to a method for reversing a vehicle into a parking space. According to said method, a nominal parking trajectory of the vehicle is determined by means of a control unit, and a steering angle for steerable wheels of the vehicle, which can be adjusted in order to drive into the parking space, is determined on the basis of the nominal parking trajectory. The inventive method is characterised in that the nominal parking trajectory (YB(X) ) is determined on the basis of two reference trajectories (yLower(x); YUpper(x)) according to a position of the vehicle. The reference trajectories (yLower(x); YUpper(x)) represent parking trajectories for parking carried out from different starting points.

Description

Method for steering a vehicle into a parking space and parking assistance device

Besehreibung:

The invention relates to a method for steering a vehicle to be parked backwards into a parking space, in which a desired parking path of the vehicle is determined by means of a control unit and in which a steering angle of steerable wheels of the vehicle to be set for driving the parking space is determined on the basis of the desired parking path ,

Furthermore, the invention relates to a parking aid device suitable for carrying out the method.

It is known to control vehicles automatically along a desired path in a parking space previously detected with the aid of environmental sensors. The desired path is usually given in the form of polynomials or as a sequence of circular and clothoid arcs, as disclosed, for example, in German Offenlegungsschrift DE 199 400 07 A1.

Starting from the starting point, a calculation of the parameters of the intended path is usually carried out. As a rule, a very high computational effort is required in order to determine the setpoint path, for example on the basis of a higher-order polynomial, in such a way that a comfortable entry into the parking space is ensured. This has the disadvantage that in vehicles for calculating a comfortable desired course very complex and powerful computing units must be used. It is therefore an object of the present invention to reduce the calculation effort for determining the desired path for parking a vehicle.

According to the invention, this object is achieved by a method having the features of patent claim 1 and by a parking aid device having the features of patent claim 31.

Accordingly, it is provided that a method of the type mentioned above is carried out so that the target parking path is determined in accordance with a position of the vehicle from at least two reference tracks, wherein the reference trains are Einparkbahnen that different starting points of the Vehicle included.

In addition, the invention provides that a parking assistance device for steering a vehicle to be parked backwards into a parking space, comprising a control unit by means of which a desired parking path of the vehicle and a steering angle of steerable wheels of the vehicle to be set for driving the parking space can be determined is configured such that the desired parking path can be determined in accordance with a position of the vehicle from two reference tracks, the reference tracks representing parking tracks for parking starting from different starting points.

The invention thus includes the idea of determining the desired parking path on which the vehicle or a predefined reference point of the vehicle is controlled into the parking space on the basis of two reference paths. The Einparkbahn must therefore not be completely recalculated during each parking process, but it can be used with each parking the same reference paths. These are in accordance with the existing conditions, such as in particular the present position of the vehicle to a desired parking path for the

Parking procedure combined. As a result, a significant reduction of the calculation effort for the calculation of the parking track is achieved.

A position of the vehicle is understood in the context of the invention, in particular the position of a predetermined Aufpunktes of the vehicle.

In a particularly advantageous embodiment of the method according to the invention and the parking aid device according to the invention, it is provided that the reference paths correspond to parking paths which contain starting points with different lateral distances from the parking space.

A lateral distance of a point from the parking space is understood to be the distance between the point and the parking space measured in the transverse direction of the parking space.

An expedient embodiment of the method according to the invention and of the device according to the invention is characterized in that the desired parking path is determined from the reference paths such that one point of the desired parking path corresponds to the position of a predetermined Aufpunktes of the vehicle.

In a further particularly advantageous embodiment of the method according to the invention and the inventive Parking assistance device, it is provided that the reference tracks are stored in the control unit.

In order to minimize the required memory requirement, it is provided in a particularly advantageous development of the method and the parking aid device according to the invention that the reference tracks in relation to the parking are stored in a parking space with the smallest possible longitudinal extent for trafficability, and that an adaptation of at least one reference track to the present parking space takes place.

As a result, the memory requirements for the storage of the reference tracks in the control unit can be minimized, since only the reference tracks must be stored, which relate to the parking space with the smallest sufficient for drivability longitudinal extent.

An expedient embodiment of the method according to the invention and the parking aid device according to the invention is characterized in that the adaptation takes place by using a scaling factor by stretching the reference track in the direction of the longitudinal extent of the parking space.

An advantageous development of the method according to the invention and the parking aid device according to the invention is characterized in that the scaling factor is determined from a ratio of the longitudinal extent of the present parking space to the longitudinal extent of the parking space with the smallest possible longitudinal extent for a passability. In an equally advantageous development of the method according to the invention and the parking aid device according to the invention, it is provided that the scaling factor is predetermined as a function of the longitudinal extent of the present parking space.

Furthermore, an advantageous embodiment of the method according to the invention and the Einparkhilfeein- device according to the invention is characterized in that the reference path, which contains the starting point with the greatest lateral distance to the parking space is taken without stretching, while the other reference tracks by using the scale factor by stretching adapted to the existing parking space.

A preferred development of the method according to the invention and of the parking aid device according to the invention provides that the desired parking path results from an addition of the reference paths multiplied by in each case one factor.

A particularly preferred embodiment of the method according to the invention and the parking aid device according to the invention is characterized in that the desired parking path y _B (x) in the form

YB (X) = Fy _Up by (x) + (1-F) -Vloudfx) is calculated from a first reference trajectory yupp _e r (x) and a second reference trajectory yLower (x), where x is a coordinate on a longitudinal direction of the Parking space directed coordinate axis and F is an interpolation factor. The y-coordinate is a coordinate on a directed in the transverse direction of the parking space coordinate axis.

Thus, the desired parking path is advantageously determined by an interpolation method from the reference paths.

In addition, an advantageous embodiment of the method according to the invention and the parking aid device according to the invention is characterized in that the reference paths consist of several sections, wherein the last four sections in the direction of travel to a clothoid section, a circular arc section, another clothoid section and a another arc section is.

Under the direction of travel is understood here the direction in which the vehicle is controlled starting from the starting position in the parking space.

Based on reference trajectories having such track sections, a desired parking track can be determined, which ensures a particularly comfortable parking with not too large maximum steering angles and steering angular velocities. In particular, it can be avoided on the basis of such reference paths that, when the target parking path is being traveled, steering angle changes occur which make it necessary to stop the vehicle during the parking process.

An expedient embodiment of the method according to the invention and of the parking aid device according to the invention is additionally characterized in that the reference tracks are composed of five sections, wherein the in Driving direction first section is about a straight line section.

A preferred embodiment of the method according to the invention and the parking aid device according to the invention provides that points of the desired parking track are each assigned a desired yaw angle of the vehicle.

In an embodiment of the method according to the invention and the device according to the invention, it is advantageously provided that in each case a yaw angle is stored in the control unit to points of the reference paths, and that the desired yaw angle, which is assigned to the desired parking path, from the yaw angles is determined, which are stored to points of the reference orbits.

A further preferred embodiment of the method according to the invention and the parking aid device according to the invention provides that points of the desired parking path are each assigned a desired steering angle.

In an embodiment of the method and the device according to the invention, it is advantageously provided that in each case a steering angle is stored in the control unit for points of the reference paths, and that the desired steering angle, which is assigned to the desired parking path, is determined from the steering angles which are stored to points of the reference orbits.

Furthermore, a preferred embodiment of the method according to the invention and the parking aid device according to the invention is characterized in that the for driving on the Parking space to be set steering angle in the control unit is determined based on a feedforward control, wherein a proportion of the steering angle in response to one of the actual position of the vehicle on the target parking path after a predetermined distance subsequent point of the target parking path and assigned to this point Target yaw angle is determined.

On the basis of the feedforward control, a control of the vehicle which is particularly comfortable for the driver during the parking process can be carried out without phase delay.

It is advantageously provided in one embodiment of the method according to the invention and the Einparkhilfeein- device that the feedforward control is combined with a position control, wherein a proportion of the set for driving the parking space steering angle in dependence on a deviation between the actual position of the vehicle and the desired parking path is determined.

On the basis of such a position control thereby possible inaccuracies in the feedforward control can be corrected.

Furthermore, it is advantageous in one embodiment of the invention to provide that the feedforward control is combined with a yaw angle control, a proportion of the steering angle being dependent on a deviation between the actual yaw angle of the vehicle and the desired yaw angle which corresponds to one of the actual yaw angles. Position of the vehicle is assigned to the adjacent point of SoIl- Einparkbahn, is determined. On the basis of such a yaw angle control also possible inaccuracies in the feedforward control can be corrected.

In general, the values of the state variables of the vehicle, in particular of the yaw angle and of the steering angle, set in a driver-selected starting position for the parking operation do not correspond to the values predefined for the desired parking path, so that the vehicle usually does not respond as required the initial position determined desired parking track can be controlled in the parking space.

The state variables of the vehicle must therefore be adapted to the state variables specified for a desired parking path. This is preferably done by means of a controller, without stopping the vehicle thereby, so that a comfortable parking is guaranteed.

In a preferred embodiment of the invention

Method and the parking aid device according to the invention, it is provided for this purpose that the vehicle is initially controlled starting from a starting point on the basis of a predictive control to the desired parking path, and that subsequently the feedforward control is made.

Thus, advantageously, a predictive controller is used to drive the vehicle onto a possible desired parking path.

An advantageous embodiment of the method according to the invention and the parking aid device according to the invention provides in that the steering angle to be set for driving the parking space is monitored by the control unit on the basis of a predictive control as a function of a deviation between a driving distance of a given distance from an actual position of the vehicle assuming a constant steering angle during the driving of the distance expected position of the vehicle and a provisional target Einparkbahn is determined.

Due to such a predictive control, the control behavior largely corresponds to that of the driver. Thus, the vehicle control during the parking process for the driver is easy to understand, whereby the comfort for the driver is further increased.

An advantageous embodiment of the method and the parking aid device according to the invention is characterized in that the deviation corresponds to a measured in the transverse direction of the parking space distance between the expected position of the predetermined Aufpunktes of the vehicle and the desired parking path.

In an expedient embodiment of the method according to the invention and the parking aid device according to the invention, it is provided that the provisional desired parking path is determined from the reference paths in accordance with the actual position of the vehicle.

An advantageous embodiment of the method according to the invention and the parking aid device according to the invention further provides that the vehicle used for driving through the parking space can be used. steering angle δ _So ii is determined on the basis of the predictive control on the basis of the relationship δsoll = ^K Preview] ^{AY dt} , where Kp _rev i _ew an amplification factor, ΔY the transversely to the parking space (9) measured distance between the expected position of the predetermined Aufpunktes (A ) of the vehicle (1) and the provisional desired parking path (V _B (X)) and t describes a time variable.

Based on such a rule law can advantageously be avoided a permanent control deviation.

An advantageous development of the method according to the invention and the parking aid device according to the invention is characterized in that the control unit operates intermittently and that in each clock step a desired parking path is determined in accordance with the current actual position of the vehicle from the reference paths.

Advantageously, it is provided in one embodiment of the method and the parking aid device according to the invention that the feedforward control is made after it has been determined that the deviation between the expected after driving the predetermined distance position of the vehicle and the provisional desired parking path is smaller than is a predetermined threshold.

It is also provided in an advantageous embodiment of the method according to the invention and the Einparkhil- feeinrichtung invention that the feedforward control is made after it has been determined that a deviation between the after driving the predetermined distance expected yaw angle of the vehicle and a target yaw angle, which is assigned to one of the expected after the driving of the predetermined distance position of the vehicle point of the provisional target Einparkbahn, is smaller than a predetermined threshold.

In a further embodiment of the method according to the invention and the parking aid device according to the invention, it is provided that the precontrol is carried out after the control unit has determined that the deviation between the actual steering angle of the vehicle and a desired steering angle which corresponds to one of after the vehicle has traveled past the predetermined distance expected position of the vehicle adjacent point of the provisional target parking path is smaller than a predetermined threshold.

In addition, a particularly advantageous embodiment of the method according to the invention and the parking aid device according to the invention is characterized in that the desired parking path corresponds to the provisional desired parking path determined immediately before the switching to the pilot control.

Advantageous embodiments of the invention thus include the idea of controlling the vehicle based on the predictive control with a predetermined yaw angle and a predetermined steering angle to a desired parking path and subsequently make a feedforward, in which the vehicle is controlled in this parking path in the parking space ,

For this purpose, preliminary provisional parking paths are successively determined as part of the predictive control. The real one Desired parking track corresponds to the provisional desired parking track for which only a small expected position deviation only small expected deviations between the target yaw angle and the yaw angle of the vehicle and the target steering angle and the steering angle are determined at the steerable wheels of the vehicle. Thus, the vehicle is controlled on the basis of the predictive control with "matching" yaw and steering angle to a desired parking path.

Further advantages, features and expedient developments of the invention will become apparent from the dependent claims and the following description of preferred embodiments with reference to FIGS.

From the figures shows

1 is a schematic representation of a suitable for carrying out the invention motor vehicle,

2 is a schematic representation of a desired parking path for a parking operation and two reference paths, from which the desired parking path is determined in the context of the invention and

Fig. 3 is a schematic representation of a desired parking path for a parking operation and two maps that limit a valid range of possible starting points for the parking operation.

The motor vehicle shown schematically in Figure 1, which is designated as a whole by the reference numeral 1, has four wheels 2a, ..., 2d, which each have a wheel speed sensor 3a, ..., 3d, which is signal-wise connected to a control unit (ECU) 4. The vehicle 1 has at least two steerable wheels, which in the illustrated embodiment of the invention are the front wheels 2a, 2b. The front wheels 2 a, 2 b are connected via a steering line to a steering actuating means, not shown in FIG. 1, with which the driver of the vehicle 1 can set a steering angle at the front wheels 2 a, 2 b. Furthermore, the steering column preferably contains an electromechanical adjusting device 5, which also allows adjusting a steering angle or a steering torque that can be felt by the driver, independently of the driver's specification. The control commands for adjusting the steering angle or the steering torque receives the adjusting device 5 from the control unit 4. In the following it is assumed by way of example that the adjusting device 5 is a steering angle adjusting device which receives control commands for setting a steering angle δsoii from the control unit 4 and implements.

To measure the steering angle δ present at the front wheels 2a, 2b, the steering line includes a steering angle sensor 6 which is signal-wise connected to the control unit 4.

From the signals of the wheel speed sensors 3 a, 3 b, 3 b, it is possible in particular to determine in the control unit 4 the distance which the vehicle 1 traveled from a certain point. The direction of the vehicle movement can be determined based on the signal of the steering angle sensor 6. Thus, in each case the current position of the vehicle can be determined relative to a reference point, such as the corner of a parking space. Furthermore, the yaw angle θ of the vehicle can be determined from the wheel speed and the steering angle signal, the yaw angle θ being understood to mean the angle between the vehicle longitudinal axis and the longitudinal axis of the parking space to be traveled, ie the x axis of the coordinate system illustrated in FIG ,

Optionally, in one embodiment of the invention, the vehicle 1 may have a yaw rate sensor 8 or a yaw rate sensor likewise connected in a signal-wise manner with the control unit 4. These sensors can serve to check or check the plausibility of the yaw angle θ of the vehicle 1 calculated from the wheel speed and steering angle signals.

In addition, the vehicle 1 has at least one signal sensor connected to the control unit 4 environment sensor 7, with the distances between the vehicle 1 and laterally located from the vehicle 1 objects can be determined. The surroundings sensor 7 can be embodied, for example, as a radar, lidar, ultrasound or infrared sensor. Furthermore, the surroundings sensor 7 can also be a camera which provides images of the vehicle surroundings, from which in particular the distance between the vehicle 1 and objects located laterally from the vehicle 1 can be determined.

By means of the control unit 4, a parking function is performed, in which a parking space is automatically measured and the vehicle 1 is automatically parked in a parking space.

Preferably, it is provided that the vehicle 1 during the parking process on the basis of control commands of the tax unit 4 is directed by means of the adjusting device 5, that the longitudinal guidance of the vehicle 1, that is, the acceleration and deceleration, but automatically by the driver of the vehicle 1 is made.

Before the start of the actual parking process, first the size of the parking space and its position relative to the vehicle 1 are determined by means of the environment sensor 7. For this purpose, for example, the distance between the vehicle 1 and objects located laterally from the vehicle 1 is determined while driving past the parking space. The section on which this distance is greater than on the remaining sections corresponds to the lateral boundary of the parking space.

Based on the signals from the wheel speed sensors 3a,..., 3d and the steering angle sensor 6, starting from a point in front of the parking space, the position of the vehicle 1 is detected continuously in a reference system fixedly connected to the starting point. Knowing the position of the vehicle 1 and based on the distance signals of the environment sensor while the position of the parking space can be determined in the coordinate system.

Thus, the location of the parking space is known relative to a position of the vehicle 1 behind the parking space in which the vehicle 1 has been stopped by the driver. The stopping of the vehicle 1 can take place, for example, as a result of a triggered by the control unit 4 signal indicating to the driver that a parking space of sufficient size has been determined. The position assumed is the initial position for the controlled by the control unit 14 parking.

The method provided in the context of the invention for parking the vehicle 1 in the parking space starting from the starting position is explained below with reference to FIG. The figure shows schematically a parking space 9, the longitudinal extent (expansion in the x direction) of two vehicles 10, 11 is limited. This may be, for example, two vehicles 10, 11 parked on the roadside.

Likewise, the parking space 9 can be limited by other obstacles. The vehicle 1 is shown in Figure 2 in the starting position for the parking operation.

For this starting position of the control unit 4 is a

Einparkbahn calculated on which a given point of the vehicle 1 is to move in the parking in the parking space 9. For example, the center point of the rear axle 12 of the vehicle 1 (FIG. 1) designated as point A in FIG.

The determination of a desired parking path y _B (x) takes place within the scope of the invention using two reference paths V _L0 - _who (x) and yupper (x) • These are parking paths on which the parking starting from starting points with different lateral distances (ie distances in the y-direction) of the Aufpunktes A from the parking space 9 would take place. The reference trajectory yL _owe r (x) describes a parking path for parking starting from a smaller lateral distance than the reference trajectory yupper (x). For example, the reference paths can be the two parking paths with the smallest and the largest lateral distance from the parking space 9, on which a sufficiently comfortable drive into the parking space 9 is possible. Basically, however, the reference tracks can be chosen arbitrarily.

Furthermore, within the scope of the invention, it is also possible to use more than two reference paths for calculating the setpoint parking path, in order to possibly determine an even more comfortable setpoint parking path. In the following, however, it is assumed by way of example that the desired parking path is determined on the basis of two reference tracks.

The reference trajectories each consist of several

Rail sections together, starting from the parking space at least two circular arcs (Kr) are provided with opposite curvature and a straight line (G). However, in order to pass through two circular arcs of opposite curvature, the vehicle must travel at the turning point, i. the point at which the circular arcs connect to each other, are stopped. In addition, the vehicle 1 and its steering are heavily loaded in such a train. Preferably, therefore, a Doppelklothoidbogen is inserted between the two circular arcs at the deflection point. Another clothoid bow is preferably inserted between the second circular arc and the straight line to match the curvature of the web to the yaw angle of the vehicle 1.

As shown in FIG. 2, the reference paths thus have five track sections starting from the parking space 9, the first track section being a circular arc (Kr), the second track section being a clothoid arc (Kl), wherein the third track section to another arc (Kr), in the fourth track section to another Klothoidbogen (Kl) and the fifth track section is a straight line (G).

The reference trajectories are calculated offline-for example as part of a simulation of the parking process-and are stored in the control unit 4. In this case, for example, support points within a coordinate system whose origin lies approximately at a corner point of the parking space 9, in the

Control unit 4 are stored. The position of the vehicle 1 determined in a certain coordinate system can be transformed by a shift into the system used to define the reference paths. Likewise, it may also be provided that the reference tracks are transformed by a shift in the coordinate system used for the parking operation.

In addition, it is provided that the reference tracks stored in the control unit 4 are related to the smallest possible parking space, ie the parking space with the smallest extension in the x-direction, at which parking is just possible. If there is a parking space 9 with a greater longitudinal extent, the reference paths are stretched in the x direction on the basis of a function which is determined by the longitudinal extent of the present parking space. In particular, the function specifies a scaling factor for the reference paths, wherein the scaling factor does not have to be specified uniformly by the function for an entire path. Such a scaling corresponds to an extension of the reference paths in the x-direction, which could in principle also be dispensed with. The extension, however, has the consequence that the maximum steering angle occurring during the parking process and the maximum steering angle speed are reduced, so that the parking operation is more comfortable for the driver.

Preferably, there is no scaling or stretching of the farthest towards the center of the road extending reference path with the greatest lateral distance to the parking space. This is taken over without stretching. In this way, the valid starting range between the reference path with the greatest lateral distance to the parking space and the reference path with the smallest lateral distance from the parking space is increased.

Further, in the extension of the reference paths, it is checked whether the minimum distance between the front right corner of the vehicle 1 to be parked and the rear left corner of the front parking space boundary (ie, the vehicle 11) is rightward when parking respectively the minimum distance between the front left corner of the vehicle to be parked and rear right corner of the front parking space boundary when parking to the left due to the scaling over the parking in the smallest possible parking space changed by the corresponding desired parking path. If it is found that this minimum distance decreases, a larger scaling factor is used.

The function indicating the scaling factor is preferably calculated offline for different parking space lengths and stored within the control unit 4 as a function of the longitudinal extent of the present parking space.

In the following, it is assumed that such a scaling of the reference orbits has been carried out. The im

The reference tracks described below are thus preferably in the manner previously described scaled tracks.

Preferably, interpolation points 4 of the reference tracks yi, ower (x) and yupper (x) are stored within a memory of the control unit 4. For each support point of the lower reference track y _Lo _ _wer (x) are additionally a target yaw angle θ _LoW er (x) and a target steering angle δ _Lower (x) and for the nodes of the upper reference track yupp _e r (x) respectively a desired yaw angle θupper (x) and a target steering angle δ _Up per (x) stored. Due to the scaling of the reference paths, an adjustment of the desired yaw angle and the desired steering angle takes place in relation to the present parking space.

The desired parking path for parking is determined within the control unit 4 by an interpolation method from the two reference tracks. The following applies to the desired parking path: y _B (X) = F - y _Upper (X) ₊ (I -F) - y _Lower (x) (1)

The interpolation factor F is determined so that the desired parking path y _B (x) contains the point A with the coordinates (x _A , y _A ), ie that y _B (XA) = YA holds. Accordingly applies

T _? In this case, it can be shown that the interpolated desired parking path Y _B (X) satisfies the required secondary conditions, in particular the requirements for a steady steering angle progression, if the maximum steering angle and maximum steering angle speed are not exceeded and if there are no collisions, if the state variables yaw angle and Steering angle when traveling the web have the predetermined values.

The target yaw angle θ _B (x) for a certain point of the lane is determined by a similar interpolation method as the target parking lane. Specifically, the target yaw angle θ _B (x) at a point (x, y _B (x)) of the target parking trajectory is θ _B (x) = F Θ _Upper (x) + {IF} θ _Lower (x) ( 4), the interpolation factor F corresponding to the interpolation factor F determined in the calculation of the desired parking path.

Similarly, the target steering angle δ _B (x) is determined at a point (x, Y _B (X)) of the target parking trajectory. In the context of the invention, this results in δ _B (x) = F δ _Upper (x) + {1 F} δ _Lower (x) (5) where F is again the interpolation factor determined in the calculation of the desired parking path.

In order to control the vehicle as accurately as possible and with a good steering feel for the driver along a desired parking path, a combination of a pre-control and a yaw angle and position control is performed. The pilot control is performed by means of a pilot control unit in the control unit 4. In this case, in each clock step, a proportion of the manipulated variable δ _So n as a function of one of the current position (x _A , y _A ) of Aufpunktes A of the vehicle 1 on the target parking path after a predetermined distance of, for example, a few centimeters subsequent point of the target Einparkbahn and determined this point associated set yaw angle.

The feedforward control is combined with a position and

Yaw rate control. Due to the position control, a further portion of the desired steering angle is determined as a function of a deviation between the current position of the vehicle 1 and the desired parking curve. In particular, the position control is based on the deviation of the y-coordinate of the position (x _A , y _A ) of the Aufpunktes A of the vehicle 1 from the point (x _A , y _B (x _A )) of the desired parking path. Based on the yaw rate control, a proportion of the desired steering angle is determined as a function of the deviation between the current yaw angle of the vehicle 1 and the desired yaw angle, which is assigned to the point of the desired parking path which corresponds to the current position of the point A of the Vehicle 1 is adjacent, ie the point of the desired parking path with the same x-coordinate as the current position of the point A of the vehicle 1. For the position and yaw rate control P or PI controller are preferably used.

The various portions of the desired steering angle are then arbitrarily arbitrated, for example by summing, to obtain the manipulated variable δ _So n. The steering angle δs _o ii is then by means of the adjusting device. 5 set. In this way, the vehicle 1 is then controlled to a position in the parking space 9.

As a rule, however, the actual values of the steering angle and the yaw angle present in the initial position do not correspond to the predefined setpoint values. In order to control the vehicle 1 in the correct orientation, ie with the predetermined desired yaw angle and the predetermined target steering angle to a possible desired parking path on which it can be parked in the parking space, by a in the control unit. 4 integrated control unit, the steering angle δ _So n determines that causes the values of the relevant state variables of the vehicle 1 to approach the intended parking for a target parking, without having to stop the vehicle after the start of the parking operation.

In particular, for this purpose, a so-called predictive controller (Preview Controller) is used, whose control behavior is closely based on that of the driver. As a result, the control interventions are plausible and pleasant for the driver. Furthermore, the control parameters "foresight" and "amplification" are easy to apply, since their effects for the application engineer are generally known from their own driving experience.

The control unit preferably operates in cycles. In each clocking step, it determines a provisional desired parking path in accordance with the actual position of the point A of the vehicle 1 in the manner described above.

In addition, in each timing step, it determines the deviation of the actual position of the point A from the provisional desired parking track, which, assuming a constant steering angle kels after a distance l _{pre is} to be expected. The expected path of the vehicle 1 is a circular arc of length lpr _er whose radius results from the present steering angle δ. This trace can be used to calculate the expected position of point A, where the difference between the y coordinate of the expected position of the point A and the y coordinate y _{A of} the current position is dy and the difference of the x coordinates is the expected point Position and the x-coordinate x _{A of} the current position should be denoted by dx. If the amount of the steering angle δ is smaller than a predefined threshold value, the differences dx and dy are determined by linear interpolation on the basis of the singularity occurring for the value δ = 0 in the circular calculation.

The expected deviation from the provisional target parking trajectory y _B (x) is thus:

AY = y _B (x _A + dx) -y _A -dy (3)

In addition, the yaw angle is calculated, which is expected after the distance l _pre , ie the yaw angle θ _pre , the vehicle 1 after the distance l _pre when driving at a constant steering angle at the point (x _A + dx, y _A + dy) having. In addition, the deviation between the yaw angle θ _pre and the target yaw rate θ _B (x) provided for the point (x _A + dx, y _B (x _A + dx)) of the provisional sole parking trajectory is determined. The deviation between the yaw angle θ _pre and the predetermined yaw angle is Δθ = θ _pre - Θ _B (x _A + dx).

Similarly, a steering angle deviation between the present steering angle δ and that provided for the point (x _A + dx, y _B (x _A + dx)) of the provisional target Einparkbahn Target steering angle determined. The steering angle deviation is given by Δδ = δ - δ _B (x _A + dx).

The amounts of the deviations ΔY, Δθ and Δδ are then compared with a predetermined threshold value. If one of the amounts is greater than the corresponding threshold value, the control variable δ _So ii is calculated in accordance with the control law (6) within the control unit 4 by means of the control unit. where _Kprev i _{ew is} the gain of the look-ahead controller. The steering angle δ _So ii is adjusted or adjusted by means of the adjusting unit 5 on the steerable wheels 2a, 2b.

Preferably, it is provided that the magnitude of the variable Kpr _e vi _ew 'ΔY is limited at the beginning of the parking process and that the possible values are increased with increasing distance traveled during the parking process, until after a predetermined distance there is no limitation. The maximum values of the amount are predetermined as a function of the traveled distance in the form of a ramp function.

The provisional desired parking path is recalculated in each clock step of the control unit 4 based on the current position (x _A , y _A ) of the Aufpunktes A of the vehicle 1 from the reference tracks yL _owe r and Yupper, if the difference y _Up per (x _A ) - YLower (x _A ) is not less than a threshold. If this is the case, the provisional desired parking path y _B (x) is preferably not recalculated. This can avoid numerical problems. Further, the amounts of the deviations ΔY, Δθ and Δδ in each clocking step are compared with their associated threshold values. If one of these amounts is greater than the corresponding threshold value, the steering angle control is carried out as described above on the basis of the control law specified in equation 6.

If, however, it is found in a timing step that deviations ΔY, Δθ and Δδ are smaller than the corresponding threshold values, the steering angle control switches from the forward-looking control to the previously described combination of precontrol, yaw angle and position control. The previously calculated provisional desired parking path y _B (x) is no longer changed, but this path is used in the pre-control as a target parking path basis. On this target parking the vehicle is then controlled in the parking space.

In the method described above, in principle for each possible starting position of the vehicle 1, a desired parking path can be calculated or interpolated from the reference paths. However, it is not possible for each starting position to control the vehicle 1 without collision in the parking space 9.

Therefore, it is provided within the scope of the invention to ascertain the trafficability of the parking space 9 before the start of the parking operation, which will be explained below with reference to FIG. In this case, it is provided that, at the beginning of the parking process started by the driver, it is first checked whether the parking space can be driven without collision starting from the starting position.

In a further embodiment of the invention, it may be provided that the driver is informed continuously after passing through the parking space whether the vehicle 1 is in a position from which the parking space is passable. If the driver recognizes on the basis of this message that the vehicle 1 assumes such a position, he can stop the vehicle 1 and start the parking procedure.

The navigability of the parking space 9 is determined in a preferred embodiment of the invention with reference to two maps Ymin (δ, θ, x _A ) and ymax (δ, θ, x _A ). In this case, the map y-min (δ, θ, x _A ) indicates the lower limit and the map y-m _a χ (δ, θ, x _A ) the upper limit for the y-coordinate of the point A of the vehicle 1, for parking at a given steering angle δ and a given yaw angle θ of

Vehicle 1 and a given x-coordinate of the Aufpunktes A of the vehicle 1 is possible.

For a given yaw angle and given steering angle, the maps y _min (δ, θ, x _A ) and y _max (δ, θ, x _A ) thus limit a valid range of possible starting points for the parking maneuver, in Figure 3, using a hatched area is shown.

The maps y _min (δ, θ, x _A ) and y _max (δ, θ, x _A ) are stored in the control unit 4, wherein for different combinations of discrete values for the steering angle δ, the yaw angle θ and the x-coordinate of the Aufpunktes A of the vehicle 1 each have a value y _m in and y _{max is} stored. There is thus a grid of characteristic map points in a (δ, θ, x _A ) space in which a value for y _min and y _max is stored in the control unit 4 for each characteristic field point.

It can be shown that the parking space 9 for a given value triplet (δ, θ, x _A ) of the values for the yaw angle, the steering angle and the x-coordinates of the Aufpunktes A of the vehicle 1 for all lateral distances y _{A of} the Aufpunktes A of the vehicle 1 from the parking space 9, which are between y _min and y _max , passable.

However, it is also possible within the scope of the invention, instead of the maps y _min (δ, θ, x _A ) and y _max (δ, θ, x _A ) to use other maps, as will be described in more detail below.

The maps stored in the control unit 4 again relate to the smallest possible parking space. If there is a parking space with a greater longitudinal extent, the maps are scaled in the same way as the scaling of the reference paths in their x-coordinate. The scaling factor is in turn given as a function of the longitudinal extent of the present parking space 9, wherein, as with the scaling of the reference paths, it may be provided that the scaling can be carried out in different ways based on the function in different regions of the x-coordinates of the maps ,

Likewise, it is possible in one embodiment of the invention that determined position of the vehicle 1 and the Point A is transformed by a scaling of the x-coordinate of the Aufpunktes A in the coordinate system in which the maps and reference trajectories are defined. Furthermore, the determined yaw angle of the vehicle is also transformed into this coordinate system in the manner already explained. The scaling factor for scaling the x-coordinates is determined in the manner described above.

In the following it is assumed that such a scaling of the x-coordinate of the Aufpunktes A of the vehicle 1 and the yaw angle has been performed or that the maps have been scaled in the manner shown.

In order to determine the trafficability of the parking space 9, it is checked for the present steering angle δ, the present yaw angle θ and the x coordinate determined for the point A of the vehicle 1, whether for the y coordinate of the point A the condition

Ymin (δ, θ, X _A ) <y _A <Ym _a x (δ, θ, X _A ) is satisfied. If this is the case, the trafficability of the parking space 9 is detected and signaled to the driver. If the condition is not met, then it is determined that the parking space is not passable starting from the present position of the vehicle 1.

In general, however, the present value triplet (δ, θ, x _A ) will not match one of the value triples stored in the control unit 4. The determination of the value triples to be used for the check stored in the control unit 4 takes place in the context of the invention in a secure approach, wherein for a value triplet (δ, θ, x _A ) with the present in the current state of the vehicle 1 values the "least favorable" stored in the control unit 4 adjacent value triplet is determined.

For the present value triplet (δ, θ, x _A ), the adjacent value triples are first determined, ie the value triplets whose individual values are adjacent to the present values of the corresponding quantities. Then the values assigned to the determined value triplets y _m i _n and y _{max are} determined. Subsequently, it is checked whether the present y-coordinates of the Aufpunktes A of the vehicle 1 is smaller than one of the determined y _min values or greater than one of the determined y _max values. If this is the case, it is determined that the parking space is not passable. If this is not the case, it is determined that the parking space can be driven on the basis of the present position of the vehicle 1.

In order to determine the maps y _m in (δ, θ, x) and y _ma χ (δ, θ, x), the starting space with the possible starting position for a parking process is discretized, ie a grid of

Defined points of the boot space. For the grid points then the parking process for different yaw angles θ and steering angle δ is simulated to check whether parking is possible. In this way, a four-dimensional map f (Ö, 0, X _A , V _A ) can be obtained, in which all possible combinations of the starting values (Ö, 0, X _A , V _A ) are specified, where a parking operation is possible is. From the map f (Ö, 0, X _A , VA) then the maps y _min (δ, θ, x _A ) and y- m _a χ (δ, θ, x _A ) can be determined in the control unit get saved. As mentioned above, however, other maps can be used to determine the passability of the parking space 9, which can also be determined from the map f (Ö, 0, X _A , YA). In principle, any characteristic diagrams Zi, min (z ₂ , Z ₃ , Z ₄ ) and Zi, _max (z ₂ , Z ₃ , Z ₄ ) can be determined with pairwise different numbers {5,0, X _A , YA}, which for given sets (z ₂ , Z ₃ , Z ₄ ) of values of first vehicle quantities specify a minimum value Zi, _min or a maximum value zi, _{max of} a second vehicle size Zi. The trafficability of the parking space 9 is determined when the following applies for the value of zi for given values of Z ₂ , Z ₃ and Z ₄ :

Z _l , min (Z ₂ , Z ₃ , Z ₄ ) <Z i <Z i, _max (Z ₂ , Z ₃ , Z ₄ )

A concrete example of further possible maps are the maps θ _m in (δ, x _A , Y _A ) and θ _ma χ (δ, x _A , Y _A ), which for predetermined value triples (Ö, X _A , YA) each have a minimum value θmin (δ, x _A , YA) and a maximum value θ _ma χ indicate (δ, x _A , YA) for the yaw angle θ of the vehicle 1.

In principle, it would also be possible to determine the trafficability of the parking space 9 on the basis of the characteristic map f (Ö, 0, X _A , YA) ZU. However, this covers considerably more interpolation points than the two characteristic fields, which indicate a minimum and a maximum value for a vehicle size, with the same coverage of the valid range. By using second maps can thus be saved a significant space in the control unit 4.

As already mentioned, it is provided in one embodiment of the invention that after passing through the parking space in clock steps of a predetermined cycle time, ie for successive points of the path of the vehicle or the Aufpunk- tes A of the vehicle is checked whether the present position of the vehicle 1 permits parking in the parking space 9. The cycle time is preferably chosen so that a quasi-continuous check the passability of the parking space 9 is made.

In an advantageous development of the invention, it is provided that after leaving the valid range indicated by the maps the path of the Aufpunktes A of the vehicle 1 and the steering angle set in each case at the track points by the driver stored in the control unit 4. In this way, the track can be traced back to the valid range at a start point outside the valid range after the start of the parking operation. This expands the valid range. In particular, it is thus possible to take into account undercuts or parking on inside curves, since the track has already been driven once and this is obstacle-free assuming stationary conditions.

In this embodiment of the invention, the driver is - after the vehicle 1 has entered the valid range - after leaving this area not indicated that the parking space 9 is not passable. Rather, the driver can start the parking process outside the valid range. After starting the parking operation, the vehicle 1 is then controlled back on the basis of the stored track points and the associated steering angle by means of the control unit 4 in the valid range. For this purpose, the control unit 4 transmits setting commands to the setting device 5, with which the steering angle previously stored for this path point is set at each path point. After the vehicle 1 on this Way has come back into the valid range, the parking operation can be carried out in the manner described above.

Claims

claims:

1. A method for steering a vehicle to be parked backwards in a parking space, in which a desired parking path of the vehicle is determined by a control unit and in which based on the desired parking path to be set for driving the parking space steering angle steerable wheels of the vehicle is characterized, characterized in that the desired parking trajectory (Y _B (X)) is determined according to a position of the vehicle from two reference trajectories (yi, ower (x); Yupper (x)), the reference trajectories (y _Lo - _wer (x); Yupper (x)) represent parking lanes for parking starting from different starting points.

2. Method according to claim 1, wherein the reference paths (yLower (x); Yupper (x)) correspond to parking paths which contain starting points with different lateral distances from the parking space (9).

3. The method according to claim 1 or 2, characterized in that the desired parking path (y _B (x)) is determined from the reference tracks such that a point of the desired parking path (Y _B (X)) of the position of a predetermined Aufpunktes ( A) of the vehicle (1) corresponds.

4. Method according to one of the preceding claims, characterized in that the reference paths (yLower (x); Yupper (x)) in the control unit (4) are stored

5. The method according to any one of the preceding claims, characterized in that stored in the control unit (4) the reference tracks (y _Lo - _who (x); Yupper (x)) based on the parking in a parking space with the smallest possible longitudinal extent for a passability and that an adaptation of at least one reference trajectory (yi, ower (x); Yupper (x)) takes place to the present parking space (9).

6. The method according to claim 5, characterized in that the adaptation using a scaling factor by an extension of the reference track (yLower (x); Yupp _e r (x)) in the direction of the longitudinal extent of the parking space (9).

7. Method according to claim 6, wherein the scaling factor is determined from the ratio of the longitudinal extent of the present parking space (9) and the longitudinal extent of the parking space with the smallest possible longitudinal extent for trafficability.

8. The method according to claim 6 or 7, characterized in that the scaling factor as a function of the longitudinal len of the longitudinal extent of the existing parking space (9) is predetermined.

A method according to any one of claims 5 to 8, characterized in that the reference trajectory (yu _PP er (x)) containing the starting point with the greatest lateral distance to the parking space is taken without stretching, while the other reference trajectories are based on the scaling factor be adapted by an extension to the existing parking space (9).

10. The method according to any one of the preceding claims, characterized in that the desired parking path (y _B (x)) by an addition of each multiplied by a factor reference tracks (γLower (x); Yupper (x)) results.

11. The method according to any one of the preceding claims, characterized in that the desired parking path y _B (x) in the form

YB (X) = Fy _Up by (x) + (1-F) power (X) is calculated from a first reference trajectory yupp _e r (x) and a second reference trajectory yLower (x), where x is a coordinate on an in Longitudinal direction of the parking space directed coordinate axis and F is an interpolation factor.

12. Method according to one of the preceding claims, characterized in that the reference paths (yi, ower (x); Yupper (x)) consist of several sections, the last four sections in the direction of travel being a clothoid section (Kl), a circular arc section (Kr), a further clothoid section (Kl) and a wide ren circular arc section (Kr) acts.

13. The method according to claim 12, wherein the reference paths (yi, ower (x), Yupper (x)) are composed of five sections, wherein the first section in the direction of travel is a straight line section (G).

14. The method according to any one of the preceding claims, characterized in that points of the target parking path (y _B (x)) is assigned in each case a target yaw angle (θ _B (x)) of the vehicle (1).

15. The method according to claim 14, characterized in that at points of the reference tracks (yLower (x); Yupper (x)) each have a yaw angle (θ _LoW er (x); θ _Up per (x)) stored in the control unit (4) and that the target yaw angle (θ _B (x)) which is assigned to a point of the target parking trajectory (y _B (x)) is obtained from the yaw angles (θ _LoW er (x); θ _Up per (x)) is determined, which are stored to points of the reference trajectories (V _LO - who (x); Yupper (x)).

16. The method according to any one of the preceding claims, characterized in that points of the desired parking path (y _B (x)) each have a desired steering angle (δ _B (x)) is assigned.

17. The method according to claim 16, characterized that to points on the reference trajectories (yi, ower (x); yupper (x)) in each case a steering angle (δ _Lower (x); δ _Up per (x)) is stored in the control ^¬ unit (4) and that the desired Steering angle (δ _B (x)), which is assigned to a point of the desired parking path (y _B (x)), is determined from the steering angles (δ _Lower (x); δ _Up per (x)), which points to the Reference tracks (y _Lo _ _who (x); Yupper (x)) are stored.

18. The method according to any one of the preceding claims, characterized in that the for driving the parking space (9) to be adjusted steering angle (δ _So ii) in the control unit (4) is determined based on a pilot control, wherein a proportion of the steering angle (δ _So ii) due to the feedforward control as a function of one of the actual position of the vehicle (1) on the desired parking path (y _B (x)) after a predetermined distance subsequent point of the desired parking path (y _B (x)) and the this point associated Target yaw angle (θ _B (x)) is determined.

19. The method according to claim 18, characterized in that the precontrol is combined with a position control, wherein a proportion of the driving for the parking space (9) to be set steering angle (δ _So ii) in dependence on a deviation between the actual position of the vehicle ( 1) and the desired parking path (y _B (x)) is determined.

20. The method according to claim 18 or 19, characterized in that the feedforward control combined with a yaw angle control. wherein a proportion of the steering angle (δ _So n) to be set for driving the parking space (9) is dependent on a deviation between an actual yaw angle of the vehicle (1) and a desired yaw angle (θ _B (x)), which is assigned to one of the actual position of the vehicle (1) adjacent point of the desired parking path (V _B (X)) is determined.

21. The method according to any one of the preceding claims, characterized in that the vehicle (1) starting from a starting point initially based on a predictive control on the desired parking path (y _B (x)) is controlled, and that subsequently the feedforward control is made.

22. The method according to any one of the preceding claims, characterized in that the adjusted for driving the parking space steering angle (δ _So ii) by means of the control unit (4) due to the predictive control in response to a deviation (.DELTA.Y) between a after driving a predetermined Distance (l _pre ) is determined on the basis of an actual position of the vehicle on the assumption of a while driving the route constant steering angle expected position of the vehicle (1) and a provisional target Einparkbahn (y _B (x)).

23. The method according to claim 22, characterized in that the deviation in a transverse to the parking space (9) measured distance between the expected position of the predetermined Aufpunktes (A) of the vehicle (1) and the provisional desired parking path (y _B (x)) corresponds.

24. Method according to claim 22 or 23, characterized in that the provisional desired parking path is determined on the basis of the actual position of the vehicle from the reference tracks.

25. The method according to any one of claims 22 to 24, characterized in that the to be set for driving on the parking space steering angle δ _So ii due to the predictive control based on the relationship

is determined, where Kp _rev i _ew a gain .DELTA.Y measured in the transverse direction to the parking space (9) distance between the expected position of the predetermined reference point (A) of the vehicle (1) and the provisional setpoint parking trajectory (y _B (x)) and t describes a time variable.

26. The method according to any one of claims 22 to 25, characterized in that the control unit (4) operates in cycles and that in each clocking step a provisional target parking path (Y _B (X)) in accordance with the current actual position of the vehicle (1) the reference orbits (yLower (x); Yupper (x)).

27. The method according to any one of the preceding claims, characterized in that the feedforward control is made after it has been determined that the deviation (.DELTA.Y) between the after driving the predetermined distance (l _pre ) expected position of the vehicle (1) and the provisional target parking path (V _B (X)) is smaller than a predetermined threshold.

28. The method according to any one of the preceding claims, characterized in that the precontrol is carried out after it has been determined that the deviation between the after driving the predetermined distance (l _pre ) expected yaw angle (θ _pre ) of the vehicle (1) and a Target yaw angle (θ _B (x)) which is associated with one of the points of the provisional target parking path (Y _B (X)) adjacent to the expected position of the vehicle (1) after driving on the predetermined distance is less than a predefined threshold value is.

29. The method according to any one of the preceding claims, characterized in that the precontrol is made after it has been determined that the deviation between the actual steering angle to the steerable wheels of the vehicle and a target steering angle (δ _B (x)), which one of the points of the provisional target parking path (y _B (x)) adjacent to the expected position of the vehicle (1) is less than a predefined threshold value.

30. The method according to any one of the preceding claims, characterized in that the desired parking path (y _B (x)) of the provisional determined immediately before switching to the pilot control Target parking path (y _B (x)) corresponds.

31. Parking assistance device for steering a vehicle to be parked backwards in a parking space, comprising a control unit by means of which a desired parking path of the vehicle and to be set for driving the parking space steering angle steerable wheels of the vehicle can be determined, characterized in that the desired parking path (y _B (x)) in accordance with a position of the vehicle from two reference trajectories (Y _Lower (x); Yupper (x)) can be determined, wherein the reference trajectories (y _Lo - _who (x); Yupper (x)) parking trajectories for parking represent different starting points.