METHOD FOR COMPENSATING FOR AN INCLINATION

Abstract

A method for compensating for an inclination of a vehicle in at least one spatial direction. The vehicle has a vehicle body and an active chassis with a plurality of wheels, which are in contact with the roadway. Each wheel is joined to the vehicle body by way of an actuator, which can be adjusted in terms of its length, at a suspension point associated with the wheel. An inclination of the vehicle body in the at least one spatial direction is determined. For at least two wheels, respectively, a vertical distance to the suspension point of the vehicle body that is associated with the particular wheel is detected. Via the at least two determined distances, an inclination of the chassis in the at least one spatial direction is calculated by transformation of the vertical distance of the at least two wheels to the vehicle body.

Claims

1-11. (canceled)

12. A method for compensating for an inclination of a vehicle in at least one spatial direction, comprising: wherein the vehicle has a vehicle body and an active chassis with a plurality of wheels, which are in contact with the roadway; wherein each wheel is joined to the vehicle body by an actuator, which can be adjusted in terms of its length, at a suspension point associated with the wheel; wherein an inclination of the vehicle body in the at least one spatial direction is determined, wherein, for at least two wheels, a respective vertical distance to the suspension point of the vehicle body associated with the particular wheel is detected; wherein, via the at least two determined distances, an inclination of the chassis in the at least one spatial direction is calculated by transformation of the vertical distance of the at least two wheels to the vehicle body by using a transformation matrix $\begin{matrix} T = [\begin{matrix} l_{v} & l_{v} & - l_{h} & - l_{h} \\ t_{v} & - t_{v} & t_{h} & - t_{h} \end{matrix}] \end{matrix}$ wherein the inclination of the roadway in the at least one spatial direction is determined from a difference of the inclination of the vehicle body in the at least one spatial direction and the inclination of the chassis in the at least one spatial direction; wherein a value for at least one angle .sub.s, .sub.s, respectively, by which the roadway is inclined in the at least one spatial direction, is determined, wherein a limit value .sub.s,lim, .sub.s,lim, respectively, for the value of the at least one angle .sub.s, .sub.s is predetermined; wherein translation ratios I.sub.VA, i.sub.HA for a distance of the at least one actuator in relation to the vehicle body and for a distance of the at least one wheel in relation to the vehicle body are taken into account; wherein a target value for a change in the length of the at least one actuator is determined by: $\overset{.fwdarw.}{z_{act}} = {diag (i_{VA}, i_{VA}, i_{HA}, i_{HA})}^{T^{T}} [\begin{matrix} _{s, l .Math. im} \\ _{s, \lim} \end{matrix}] .$

13. The method according to claim 12, wherein the inclination of the chassis in the at least one spatial direction is determined by transformation of the vertical distances of the at least two wheels from a center of gravity of the vehicle body by using the transformation matrix $T = [\begin{matrix} l_{v} & l_{v} & - l_{h} & - l_{h} \\ t_{v} & - t_{v} & t_{h} & - t_{h} \end{matrix}]$ wherein a front, longitudinal length l.sub.v defines a distance of a particular front wheel from a center of gravity of the vehicle body in the longitudinal spatial direction; a rear, longitudinal length l.sub.h defines the distance of a particular rear wheel from the center of gravity in the longitudinal spatial direction; a front, transverse length t.sub.v defines the distance of the front wheel from the center of gravity in the transverse spatial direction; and a rear, transverse distance t.sub.h defines the distance of the rear wheel from the center of gravity in the transverse spatial direction.

14. The method according to claim 13, wherein the translation ratios I.sub.VA, i.sub.HA are calculated by way of a distance of an actuator from the center of gravity of the vehicle body in each case, and of a wheel from the center of gravity of the vehicle body in each case.

15. The method according to claim 12, wherein, in the presence of an upward slope travel, a negative angle of pitch .sub.s is determined, and, in the presence of downward slope travel, a positive angle of pitch .sub.s is determined.

16. The method according to claim 12, wherein the respective limit value .sub.s,lim, .sub.s,lim for the value of the at least one angle .sub.s, .sub.s is predetermined by: $\begin{matrix} _{s, \lim} = {\begin{matrix} _{s, \max} .Math. .Math. if .Math. .Math._{s} >_{s, \max} \\ _{s, \min} .Math. .Math. if .Math. .Math._{s} <_{s, \min} \\ otherwise .Math. .Math._{s} \end{matrix} \\ _{s, \lim} = {\begin{matrix} _{s, \max} .Math. .Math. if .Math. .Math._{s} >_{s, \max} \\ _{s, \min} .Math. .Math. if .Math. .Math._{s} <_{s, \min} \\ otherwise .Math. .Math._{s} \end{matrix} \end{matrix}$

17. The method according to claim 16, wherein a value of .sub.s,min in the case of upward slope travel is chosen to be greater than a value of .sub.s,max in the case of downward slope travel.

18. The method according to claim 12, wherein, for the determination of the inclination of the vehicle body, a first, coordinate system that is fixed relative to the vehicle body is used, and, for the determination of the inclination of the chassis, a second chassis-fixed coordinate system is used, and wherein a third, inertial coordinate system is used as reference coordinate system, which is established in relation to the force of gravity.

19. The method according to claim 18, wherein the inclination of the vehicle body in relation to the reference coordinate system is described via a quaternion.

20. The method according to claim 12, wherein a strapdown algorithm is used, with which it is provided that, for the determination of a corrected acceleration of the vehicle, an acceleration measured by sensor is corrected by a centrifugal acceleration and by the gravitational acceleration and, from this, a velocity of the vehicle on a planar surface is determined, and that the inclination of the vehicle body is calculated.

21. A system for compensating for an inclination of a vehicle in at least one spatial direction, wherein the vehicle has a vehicle body and an active chassis with a plurality of wheels, which are in contact with the roadway, wherein the system has a plurality of sensors and a control unit; wherein each wheel is joined to the vehicle body by way of an actuator, which can be adjusted in terms of its length, at a suspension point associated with the wheel; wherein at least a first sensor is designed for the purpose of determining an inclination of the vehicle body in the at least one spatial direction, wherein at least one second sensor is designed to record, for at least two wheels, respectively, a vertical distance to the suspension point of the vehicle body associated with the particular wheel, wherein the control unit is designed for the purpose of calculating, via at least two determined distances of the at least two wheels, an inclination of the chassis in the at least one spatial direction by transformation of the vertical distance of the at least two wheels to the vehicle body by using a transformation matrix $T = [\begin{matrix} l_{v} & l_{v} & - l_{h} & - l_{h} \\ t_{v} & - t_{v} & t_{h} & - t_{h} \end{matrix}]$ wherein the control unit is designed for the purpose of determining the inclination of the roadway in the at least one spatial direction from a difference in the inclination of the vehicle body in the at least one spatial direction and the inclination of the chassis in the at least one spatial direction, and a value for at least one angle .sub.s, .sub.s, respectively, by which the roadway is inclined in the at least one spatial direction; wherein a limit value .sub.s,lim, .sub.s,lim, respectively, for the value of the at least one angle .sub.s, .sub.s is predetermined; wherein the control unit is designed for the purpose of taking into account the translation ratios i.sub.VA, i.sub.HA for a distance of the at least one actuator in relation to the vehicle body and for a distance of the at least one wheel in relation to the vehicle body; wherein the control unit is designed for the purpose of determining a target value for a change in a length of the at least one actuator by: $\overset{.fwdarw.}{z_{act}} = {diag (i_{VA}, i_{VA}, i_{HA}, i_{HA})}^{T^{T}} [\begin{matrix} _{s, l .Math. im} \\ _{s, \lim} \end{matrix}] .$

22. The system according to claim 21, in which the at least one second sensor is designed as a distance sensor.

Description

[0035] The invention is illustrated schematically in the drawings on the basis of embodiments and will be described schematically and in detail with reference to the drawings.

[0036] FIG. 1 shows, in schematic illustration, an example for a vehicle with an embodiment of the system according to the invention.

[0037] FIG. 2 shows a diagram relating to an embodiment of the method according to the invention.

[0038] FIG. 3 shows, in schematic illustration, a detail of the vehicle from FIG. 1.

[0039] FIG. 4 shows the vehicle from FIG. 1 for different variants of the embodiment of the method according to the invention.

[0040] The figures are described in a coherent and overall manner, where identical reference numbers refer to the same components.

[0041] Illustrated schematically in FIG. 1 are a vehicle 2, constructed as a vehicle, and a roadway 4, constructed as a street, on which the vehicle 2 moves when traveling. In this case, the vehicle 2 comprises a vehicle body 6 and four wheels 8, 10, which are provided for locomotion of the vehicle 2 and of which only a front left wheel 8 and a rear left wheel 10 are shown in FIG. 1. Each wheel 8, 10 is joined to the vehicle body 6 via at least one active actuator 12, 14, wherein the wheels 8, 10 and the actuators 12, 14 are designed as components of an active chassis of the vehicle 2.

[0042] The embodiment of the system according to the invention 16 comprises, as components, a control unit 18, at least one first sensor 19 for determination of the inclination of the vehicle body 6, and a plurality ofin this case, foursecond sensors, designed as distance sensors 20, 22, only two of which are illustrated in FIG. 1, wherein a distance sensor 20, 22 of this kind is associated with each wheel 8, 10. The at least one first sensor 19 and the distance sensors 20, 22 are designed, at the same time, as components of a sensor arrangement of the system 16. Furthermore, the sensor arrangement and accordingly the system 16 comprise sensors, which are not illustrated further, for determinationas a rule, for measurementof at least one kinetic variable, usually a velocity and/or acceleration, of the vehicle 2 and/or of the vehicle body 6.

[0043] The embodiment of the method according to the invention described below on the basis of, among other things, the diagram of FIG. 2 is to be implemented with the embodiment of the system according to the invention 16 illustrated schematically in FIG. 1, wherein steps of the embodiment of the method are to be checked by the control unit 18 and accordingly controlled and/or regulated.

[0044] Moreover, three coordinate systems 24, 26, 28 as well as diversein this case, geometricparameters are illustrated in FIG. 1.

[0045] In this case, a first, vehicle body-fixed coordinate system 24 is associated with the vehicle body 6 of the vehicle 2, with its origin lying at the center of gravity 25 of the vehicle body 6. The first coordinate system 24 comprises a first axis in the spatial direction x.sub.a, which is oriented longitudinally to the vehicle body 6 as well as parallel to a direction of travel of the vehicle 2. A second axis is oriented in the spatial direction y.sub.a transversely to the vehicle body 6 as well as parallel to the axes of the vehicle 2 that extend between each two wheels 8, 10 of the vehicle 2. A third axis is oriented in the spatial direction z.sub.a parallel to a vertical axis of the vehicle body 6. All three mentioned axes and accordingly spatial directions x.sub.a, y.sub.a, z.sub.a are oriented perpendicularly to one another. In this case, it is provided in an embodiment that the two first-mentioned axes and accordingly the spatial directions x.sub.a and y.sub.a span a horizontal plane of the vehicle 2 in which the center of gravity 25 lies.

[0046] Furthermore, FIG. 1 shows two examples of vertically oriented distances dz.sub.a,VL, dz.sub.a,HL. A first distance dz.sub.a,VL relates to a distance between the front left wheel 8 and the vehicle body 6. A second distance dz.sub.a,HL relates to a distance between the rear left wheel 10 and the vehicle body 6. These distances dz.sub.a,VL dz.sub.a,HL are oriented along the actuators 12, 14 and are recorded by the distance sensors 20, 22 associated with the wheels 8, 10.

[0047] The distances of the wheels 8, 10 from the center of gravity 25 of the vehicle body 6 in a plane parallel to the horizontal plane are to be defined here via the lengths or side lengths t.sub.v, t.sub.h, l.sub.h, l.sub.v. In this case, for the front left wheel 8, a front, transverse length t.sub.v, which gives the distance of the wheel 8 from the center of gravity 25 in the transverse spatial direction, and a front, longitudinal length l.sub.v, which gives the distance of the wheel 8 from the center of gravity 25 in the longitudinal spatial direction, are to be taken into account. For the rear left wheel 10, a rear, transverse length t.sub.h, which gives the distance of the wheel 10 from the center of gravity 25 in the transverse spatial direction, and a rear, longitudinal length l.sub.h, which gives the distance of the wheel 10 from the center of gravity 25 in the longitudinal spatial direction, are to be taken into account.

[0048] A further vertically oriented distance dz.sub.a,VR relates to a distance between a front right wheel, which is not shown here, and the vehicle body 6. An additional distance dz.sub.a,HR in vertical direction relates to a distance between a rear right wheel, which is not shown here, and the vehicle body 6. The described distances dz.sub.a,VL, dz.sub.a,HL, dz.sub.a,VR, dz.sub.a,HR or distances between the wheels 8, 10 and the vehicle body 6 are given in the embodiment in relation to the horizontal plane, in which the center of gravity 25 lies.

[0049] Furthermore, for the front right wheel, the first, transverse length t.sub.v, which gives the distance of the front right wheel from the center of gravity 25 in the transverse spatial direction, and the front, longitudinal length l.sub.v, which gives the distance of the front right wheel from the center of gravity 25 in the longitudinal spatial direction, are to be taken into account. For the rear right wheel, the rear, transverse length t.sub.h, which gives the distance of this wheel from the center of gravity 25 in the transverse spatial direction, and the rear, longitudinal length l.sub.h, which gives the distance of the rear right wheel from the center of gravity 25 in the longitudinal spatial direction, are to be taken into account, wherein, in FIG. 1, the rear, transverse length that is to be taken into account for the rear right wheel is not drawn.

[0050] A second, chassis-fixed coordinate system 26 is associated with the roadway 4 and comprises a first axis in the spatial direction x.sub.s parallel to an intended direction of travel or longitudinal direction of the roadway 4, a second axis in the spatial direction y.sub.s, which is oriented parallel to a lateral direction of the roadway 4, and a third axis in the spatial direction z.sub.s, wherein all mentioned axes are oriented perpendicularly to one another. An inclination and accordingly a position of the roadway 4 is to be defined here on the basis of a lateral angle or angle of roll .sub.s, which defines an inclination of the roadway 4 in the lateral direction, and on the basis of a longitudinal angle or angle of pitch .sub.s, which defines an inclination of the roadway 4 in the longitudinal direction and accordingly, for example, an upgrade or a downgrade.

[0051] A third coordinate system 28 is designed as a reference coordinate system and comprises a first axis in the spatial direction x.sub.ref, a second axis in the spatial direction y.sub.ref, and a third axis in the spatial direction z.sub.ref, which are all oriented perpendicularly to one another.

[0052] Shown, moreover, are, for the first coordinate system 24, an angle of roll .sub.a, which defines a rotation of the vehicle body 6 around the first axis oriented in the spatial direction x.sub.a, an angle of pitch .sub.a, which defines a rotation of the vehicle body 6 around the second axis in the spatial direction y.sub.a, and an heading angle .sub.a, which defines a rotation of the vehicle body 6 around the third axis oriented in the spatial direction z.sub.a.

[0053] The first coordinate system 24 [x.sub.a, y.sub.a, z.sub.a], which is fixed to the vehicle body at the center of gravity 25 of the vehicle body 6 of the vehicle 2 follows translational and rotational movements of the vehicle body 6. The third, inertial coordinate system 28 [x.sub.ref, y.sub.ref, z.sub.ref] is employed as a reference coordinate system, wherein it is taken into account that the gravitational acceleration g acts exclusively in the spatial direction z.sub.ref parallel to a gravitational vector.

[0054] In an embodiment of the method, for estimation of an inclination or a position of the vehicle body 6, the angle of pitch .sub.a and the angle of roll .sub.a are given in relation to the third coordinate system 28, designed as a reference coordinate system.

[0055] The angles [.sub.a, .sub.a, .sub.a] enclosed between the coordinate system 24 fixed to the vehicle body and the reference system or inertial coordinate systems 28 are also referred to as the inertial angle of pitch .sub.a, the inertial angle of roll .sub.a, and the inertial heading angle .sub.a. The orientation thereof in the direction of pitch and direction of roll is referred to as the inclination of the vehicle body 6, from which the angle of pitch .sub.a and the angle of roll .sub.a are determined.

[0056] In order to be able to estimate the inclination or position of the vehicle body 6, the acceleration {right arrow over (a)}=[{umlaut over (x)}.sub.a, .sub.a, {umlaut over (z)}.sub.a].sup.T of the vehicle body 6 or of the vehicle 2 along the spatial directions x.sub.a, y.sub.a, z.sub.a and the rates of rotation {right arrow over ()}=[{dot over ()}.sub.a, {dot over ()}.sub.a, {dot over ()}.sub.a].sup.T are measured and accordingly determined by using the sensor arrangement for determination of the inertia with six degrees of freedom (IMU, inertial measurement unit), wherein the sensor arrangement can also be employed independently of the implementation of the method in the vehicle 2.

[0057] For estimation of the inclination of the vehicle body 6, it needs to be taken into account, first of all, which physical boundary conditions are to be applied to the variables {right arrow over (a)} and {right arrow over ()} that are to be determined by the sensor arrangement, for example, by way of measurement. From measurement signals of acceleration sensors of the sensor arrangement, three different physical variables are derived: [0058] the centrifugal acceleration {right arrow over (a.sub.zf)}, which depends on the rates of rotation {right arrow over ()} and the planar velocity {right arrow over (v.sub.plane)}=[v.sub.plane,x,v.sub.plane,y,v.sub.plane,z].sup.T of the vehicle 2:

{right arrow over (a.sub.zf)}={right arrow over ()}{right arrow over (v.sub.plane)}(3) [0059] the change in the adjusted, planar velocity {right arrow over (v.sub.plane)} and accordingly acceleration {right arrow over (a.sub.vp)} of the vehicle 2 and/or of the vehicle body 6 in the spatial direction of an axis of a respective acceleration sensor in the horizontal plane of the vehicle:

{right arrow over (a.sub.vp)}=R{right arrow over ({dot over (v)}.sub.plane)}(4)

the gravitational acceleration {right arrow over (a.sub.gv)}=R[0,0,g].sup.T(5)

[0060] In the above formulas, {right arrow over (v.sub.plane)} is the velocity of the vehicle 2 in the horizontal plane and R is Euler's rotation matrix (6), which is calculated taking into consideration Euler's angle in a rotation sequence of the angle of roll , the angle of pitch , and the heading angle . In this case, v.sub.plane,x is the conventional velocity of the vehicle v.sub.Vehicle in the longitudinal direction or direction of travel of the vehicle 2, which is measured via a rotational velocity of the wheels 8, 10 and displayed on the tachometer.

[00008] $\begin{matrix} R = (\begin{matrix} \cos .Math. .Math. .Math. .Math. \cos .Math. .Math. & \cos .Math. .Math. .Math. .Math. \sin .Math. .Math. & - \sin .Math. .Math. \\ \sin .Math. .Math. \sin .Math. .Math. .Math. .Math. \cos .Math. .Math. - \cos .Math. .Math. \sin .Math. .Math. & \sin .Math. .Math. \sin .Math. .Math. .Math. .Math. \sin .Math. .Math. + \cos .Math. .Math. \cos .Math. .Math. & \sin .Math. .Math. \cos .Math. .Math. \\ \cos .Math. .Math. \sin .Math. .Math. .Math. .Math. \cos .Math. .Math. + \sin .Math. .Math. \sin .Math. .Math. & \cos .Math. .Math. \sin .Math. .Math. .Math. .Math. \cos .Math. .Math. - \sin .Math. .Math. \cos .Math. .Math. & \cos .Math. .Math. \cos .Math. .Math. \end{matrix}) & (6) \end{matrix}$

[0061] The angle that is to be determined respectively, that is, .sub.a (for the vehicle body), .sub.f (for the chassis), or .sub.s (for the roadway), and , that is, .sub.a (for the vehicle body), .sub.f (for the chassis), or .sub.s (for the roadway), can usually be determined via two different methods of calculation or calculational approaches: [0062] by time integration of the rates of rotation {right arrow over ()} measured by the sensor arrangement or [0063] by elimination of the centrifugal acceleration {right arrow over (a.sub.zf)} and the change in the planar velocity {right arrow over (v.sub.plane)} and accordingly the acceleration {right arrow over (a.sub.vp)} of the vehicle 2 from the accelerations measured by the sensor arrangement, {right arrow over (a.sub.gv)}={right arrow over (a)}{right arrow over (a.sub.zf)}{right arrow over (a.sub.vp)}, and calculation of the angles via trigonometric functions

[00009] $_{a} = atan .Math. \frac{a_{gv}, x}{a_{gv}, z},_{a} = atan .Math. \frac{a_{gv}, y}{a_{gv}, z} .$

[0064] As already indicated on the basis of Equation (5), {right arrow over (a.sub.gv)} is a vector with the three elements [a.sub.gv,x, a.sub.gv,y, a.sub.gv,z].sup.T=[g*sin , g*sin *cos , g*cos *cos ].sup.T, where, in contrast, the gravitational acceleration g=9, 81 m/s.sup.2 is used in this case as a scalar, which, depending on the inclination of the vehicle body 6, which is described by Euler's rotation matrix R (6), acts on different elements of the vector {right arrow over (a.sub.gv)}. If the vehicle body 6 is not inclined, then {right arrow over (a.sub.gv)}=[0,0, g].sup.T. For an angle of roll .sub.a=90 and an angle of pitch .sub.a=0, {right arrow over (a.sub.gv)}=[0, g, 0].sup.T. If {right arrow over (a.sub.gv)} is known, then the angle of pitch .sub.a and the angle of roll .sub.a can be calculated via the above-described atan functions.

[0065] However, it needs to be taken into account for the calculations that are to be carried out that, on account of time-variable offset errors of rates of rotation sensors, an integration of the rates of rotation in a stationary manner is not precise under circumstances. This means that calculated angles exhibit a low-frequency drift and only high-frequency portions of measurement signals can be used. In contrast to this, high-frequency interferences need to be taken into account for angles determined via acceleration sensors, because changes in velocity that are difficult to record, which occur, for example, during travel over potholes cannot be eliminated from the measurement signals.

[0066] In the embodiment described here, an inclination filter or position filter based on quaternions is used as filter algorithm. It is equally possible to employ a Kalman filter for merging the two methods of calculation. In this way, the two above-mentioned methods of calculation are combined, as a result of which a signal that can be used at both low frequencies and high frequencies is provided.

[0067] A quaternion is a four-dimensional vector {right arrow over (q)}=[q.sub.1, q.sub.2, q.sub.3, q.sub.4].sup.T, via which the orientation of a rigid bodyin this case, the body of the vehicle body 6is to be described. If a rigid body is rotated in relation to a reference system by the angle around the axis {right arrow over (r)}=[r.sub.x, r.sub.y, r.sub.z].sup.T, wherein {right arrow over (r)} is a unit vector, then this orientation is defined in relation to the reference system by the quaternion {right arrow over (q)}=

[00010] ${[\cos .Math. \frac{}{2}, - r_{x} .Math. \sin .Math. \frac{}{2}, - r_{y} .Math. \sin .Math. \frac{}{2}, - r_{z} .Math. \sin .Math. \frac{}{2}]}^{T} .$

[0068] This is utilized, first of all, for the time integration of the rates of rotation {right arrow over ()} measured by the sensor arrangement, wherein the vehicle body 6 is rotated in relation to the inertial reference system at, in the present case, the rate of rotation {right arrow over ()}=[.sub.x, .sub.y, .sub.z].sup.T. Starting from an initial position {right arrow over (q.sub.L)} of the vehicle body 6, the change in the position or inclination on account of the rates of rotation is defined by Equation (7):

{right arrow over ({dot over (q)}.sub.)}={right arrow over (q.sub.L)} custom-character [0,.sub.x,.sub.y,.sub.z](7)

[0069] Here, the operator custom-character symbolizes a quaternion multiplication. In a time-discrete case, it is necessary to solve a resulting differential equation, for example, by an Euler integration (8):

{right arrow over (q.sub.,k)}={right arrow over (q.sub.L,k-1)}+{right arrow over ({dot over (q)}.sub.)}t(8)

wherein t corresponds to a step width between two points in time k and k1.

[0070] In order to define an orientation of the vehicle body 6 from the acceleration a measured by the sensor arrangement and the resulting, adjusted gravitational acceleration a.sub.gv=[a.sub.gv,x,a.sub.gv,y,a.sub.gv,z].sup.T=[g*sin , g*sin *cos , g*cos *cos ].sup.T with quaternions, the following optimization problem (9) needs to be solved:

[00011] $\begin{matrix} \overset{.fwdarw.}{q_{a}} = \min_{q_{L} {.Math.}^{4}} .Math. \overset{.fwdarw.}{f} (\overset{.fwdarw.}{q_{L}}, \overset{.fwdarw.}{a_{gv}}) .Math. .Math. with .Math. .Math. \overset{.fwdarw.}{f} (\overset{.fwdarw.}{q_{L}}, \overset{.fwdarw.}{a_{gv}}) = [\begin{matrix} 2 .Math. (q_{L, 2} .Math. q_{a, 4} - q_{L, 1} .Math. q_{L, 3}) - a_{gv, x} \\ 2 .Math. (q_{L, 1} .Math. q_{L, 2} - q_{L, 3} .Math. q_{L, 4}) - a_{gv, y} \\ 2 .Math. (0, 5 - q_{L, 2}^{2} - q_{L, 3}^{2}) - a_{gv, z} \end{matrix}] & (9) \end{matrix}$

[0071] A direct calculation of the inclination is not possible, because an infinite number of solutions exist around an axis of rotation that is oriented parallel with respect to the gravitational vector. Used for time-discrete solution of the optimization problem is a gradient-based approach (10):

[00012] $\begin{matrix} \overset{.fwdarw.}{q_{a, k}} = \overset{.fwdarw.}{q_{L, k - 1}} - .Math. \frac{V .Math. \overset{.fwdarw.}{f} (\overset{.fwdarw.}{q_{L, k - 1}}, \overset{.fwdarw.}{a_{gv}})}{.Math. .Math. \overset{.fwdarw.}{f} (\overset{.fwdarw.}{q_{L, k - 1}}, \overset{.fwdarw.}{a_{gv}}) .Math.} & (10) \end{matrix}$

[0072] with an adjustable step width .

[0073] In order to merge information about the inclination that results from the measured rates of rotation {right arrow over (q.sub.,k)} and from the accelerations {right arrow over (q.sub.a,k)}, the two quaternions {right arrow over (q.sub.a,k)}, {right arrow over (q.sub.L,k)} are added in a weighted manner by Equation (11):

{right arrow over (q.sub.L,k)}={right arrow over (q.sub.a,k)}+(1){right arrow over (q.sub.,k)}(11)

where 01 is an adjustable parameter. The angle of pitch and the angle of roll are then calculated with Equations (12a), (12b):

[00013] $\begin{matrix} _{a, k} = - \sin^{- 1} (2 .Math. q_{L, k, 2} .Math. q_{L, k, 4} + q_{L, k, 1} .Math. q_{L, k, 3}) & (12 .Math. a) \\ _{a, k} = atan (\frac{2 .Math. q_{L, k, 3} .Math. q_{L, k, 4} - 2 .Math. q_{L, k, 1} .Math. q_{L, k, 2}}{2 .Math. q_{L, k, 1}^{2} + 2 .Math. q_{L, k, 4}^{2} - 1}) & (12 .Math. b) \end{matrix}$

[0074] For elimination of the centrifugal acceleration {right arrow over (a.sub.zf)} and the change {right arrow over (a.sub.vp)} in the planar velocity {right arrow over (v.sub.plane)} from the accelerations measured by the sensor arrangement, the angles of pitch and the angles of roll are to be taken into account, which, in turn, are calculated by use of the gravitational acceleration vector {right arrow over (a.sub.gv)}.

[0075] For implementation of the embodiment of the method, a so-called strapdown approach is used, which is illustrated in the diagram in FIG. 2. Individual steps 40, 42, 44, 46, 48 of the method will be described below in detail.

[0076] At the start of the method, values of the acceleration {right arrow over (a)} and the rate of rotation {right arrow over ()} determined by sensor are provided. These values are used in a first step 40 to carry out a correction of the centrifugal force, wherein the accelerations measured by the sensor arrangement are corrected by the contribution of the centrifugal force {right arrow over (a.sub.zf)}={right arrow over ()}{right arrow over (v.sub.plane)}. In this case, a first corrected acceleration {right arrow over (a)}{right arrow over (a.sub.zf)} is determined. This first corrected acceleration {right arrow over (a)}{right arrow over (a.sub.zf)} is corrected, taking into consideration values for the angle of roll .sub.a and the angle of pitch .sub.a, in a second step 42 with implementation of a correction of the force of gravity by use of the gravitational acceleration as a result of which the acceleration in the horizontal plane is obtained.

[0077] In the scope of the method, two possibilities for calculating the planar velocity {right arrow over (v.sub.plane)} are provided.

[0078] A determination of the velocities is carried out in a third step 44 taking into consideration the acceleration {right arrow over (a.sub.vp)} of the vehicle 2, the measured velocity v of the vehicle 2, and the steering angle .sub.steer thereof, wherein the first planar velocity of the vehicle {right arrow over (v.sub.Int)}, [v.sub.Int,x,v.sub.Int,y,v.sub.Int,z].sup.T is determined by integration (13):

{right arrow over (v.sub.Int)}={right arrow over (a.sub.vp)}dt(13)

and the acceleration {right arrow over (a.sub.vp)} the vehicle 2 is calculated and accordingly determined. This planar velocity {right arrow over (v.sub.Int)} is used, in turn, in a closed control loop for correction of the centrifugal force in the first step 40.

[0079] For the velocity v.sub.plane,x in the spatial direction of a longitudinal axis of the vehicle 2, the velocity v.sub.Vehicle, measured via the rotational speeds of the wheels in the direction x.sub.a of the vehicle 2, is available. By further using a single-lane model, it is further possible to calculate an effective velocity v.sub.y,ESM in relation to the lateral axis of the vehicle from the steering angle .sub.steer and the measured velocity v.sub.Vehicle. For the vertical velocity v.sub.plane,z, no further methods of measurement or calculation are available. The alternatively determined second planar velocity of the vehicle (14):

{right arrow over (v.sub.alt)}=[v.sub.Vehicle,v.sub.y,ESM,0].sup.T(14)

and the velocity {right arrow over (v.sub.Int)} calculated by integration (13) can be merged by a suitable filter algorithm, such as, for example, by a Kalman filter (15), via a calculation procedure that comprises a weighting factor :

{right arrow over (v.sub.plane)}={right arrow over (v.sub.Int)}+(1){right arrow over (v.sub.alt)} with 01(15)

[0080] In a fourth step 46 for the correction of the planar velocity change, values of the measured velocity v.sub.Vehicle, the steering angles .sub.steer, the angle .sub.a, .sub.a, and the acceleration {right arrow over (a)}{right arrow over (a.sub.zf)}, corrected by the centrifugal acceleration {right arrow over (a.sub.zf)}, are taken into account, wherein the corrected acceleration is corrected by the contribution of the change in the planar velocity {right arrow over (a.sub.vp,alt)}=R{right arrow over ({dot over (v)}.sub.alt)}. In order to prevent a negative feedback, the derivative of a vector of the velocity {right arrow over (v.sub.alt)} is used instead of the velocity {right arrow over (v.sub.plane)} determined in accordance with the calculation procedure (15).

[0081] In a fifth step 48, taking into consideration the rate of rotation and the gravitational acceleration {right arrow over (a.sub.gv)} of the vehicle 2, the angle of pitch .sub.a as well as the angle of roll .sub.a and accordingly the inclination or position of the vehicle body 6 of the vehicle 2 are calculated by using the above-described inclination filter based on quaternions. Via the above-described procedure, the angle of pitch .sub.a and the angle of roll .sub.a are determined in relation to the inertial coordinate system 28 and used in a closed control loop for the correction of the force of gravity in the second step 42 as well as for the correction of the planar velocity change in the third step 44.

[0082] Starting from the inclination of the vehicle body 6 determined in the fifth step 48, the inclination and accordingly the position of the roadway 4 are determined, wherein the distances {right arrow over (dz.sub.a)}=[dz.sub.a,VL, dz.sub.a,VR, dz.sub.a,HL, dz.sub.a,HR].sup.T between the wheels 8, 10 and the vehicle body 6 are employed as measured variables, as a result of which, first of all, the angle of pitch .sub.f and the angle of roll .sub.f of the chassis of the vehicle 2 are calculated, wherein a calculation to be carried out depends on a transformation matrix (16):

[00014] $\begin{matrix} T = [\begin{matrix} l_{v} & l_{v} & - l_{h} & - l_{h} \\ t_{v} & - t_{v} & t_{h} & - t_{h} \end{matrix}] & (16) \end{matrix}$

[0083] where a geometric position of the center of gravity 25 will be or is defined in relation to the positions of the wheels 8, 10. In this case, the first column gives the distance of the front left wheel 8, the second column gives the distance of the front right wheel, the third column gives the distance of the rear left wheel 10, and the fourth column gives the distance of the rear right wheel from the center of gravity 25 within the horizontal plane.

[0084] The inclination of the chassis is then determined via the vectorial relation (17):

[00015] $\begin{matrix} [\begin{matrix} _{f} \\ _{f} \end{matrix}] = T .Math. \overset{.fwdarw.}{{dz}_{a}} & (17) \end{matrix}$

[0085] By subtraction of the inclination of the chassis from the inclination of the vehicle body 6, the inclination of the roadway 4 in relation to the first coordinate system 24 fixed to the vehicle body is calculated via the vectorial relation (18):

[00016] $\begin{matrix} [\begin{matrix} _{s} \\ _{s} \end{matrix}] = [\begin{matrix} _{a} \\ _{a} \end{matrix}] - [\begin{matrix} _{f} \\ _{f} \end{matrix}] & (18) \end{matrix}$

[0086] Because any deflection of the wheels 8, 10 is very small in comparison to the distance that is to be taken into account, said wheel deflection is ignored in the above calculation.

[0087] Because the angles .sub.a and .sub.a are estimated values for the inclination of the vehicle body 6 in relation to the vector and .sub.f and .sub.f define the relative angle between the vehicle body 6 and the surface of the roadway 4, .sub.s and .sub.s also provide angles as estimated variables for the inclination of the roadway 4 or street in relation to the gravitational vector.

[0088] For implementation of the method, a compensation of the inclination of the roadway 4 is to be applied to the active chassis of the vehicle 2 by correction of an inclination of the vehicle body 6 and, subsequently, the vehicle body 6 is to be aligned with the horizon or horizontally.

[0089] In this regard, it is to be predetermined on the basis of target values for a change in length of the actuators 12, 14 to what extent such a compensation of the inclination or a horizontal leveling of the vehicle body is to be done. In this way, through adjustment of respective lengths of the actuators 12, 14 to the target values during upward slope travel or uphill travel, a stronger horizontal leveling is to be provided in qualitative terms than for downward slope or downhill travel.

[0090] In the case of upward slope travel, the vehicle body 6 of the vehicle 2 is raised at the rear and lowered at the front, as a result of which a view of the occupants is to be improved and a comfort is to be increased. In the case of downward slope travel, the vehicle body 6 is raised at the front and lowered at the rear, although, in this case, in comparison to upward slope travel, a substantially lesser compensation of the inclination is to be done in order not to worsen the view of the occupants and in order to ensure a ground clearance of the vehicle body 6 during a transition from downward slope travel or downhill travel to the horizontal.

[0091] It is also conceivable to align the vehicle body 6 horizontally laterally to the direction of travel of the vehicle 2, wherein a compensation of the inclination of the vehicle body 6 in the lateral direction can also be limited by specifying target values in order to avoid driving situations in which, for example, a ground clearance might be limited.

[0092] For implementation of the method, the calculated angle of inclination of the roadway .sub.s and .sub.s is limited, first of all, by specifying target or limit values .sub.s,lim, .sub.s,lim:

[00017] $\begin{matrix} _{s, \lim} = {\begin{matrix} _{s, \max} .Math. .Math. if .Math. .Math._{s} >_{s, \max} \\ _{s, \min} .Math. .Math. if .Math. .Math._{s} <_{s, \min} \\ otherwise .Math. .Math._{s} \end{matrix} & (19) \\ _{s, \lim} = {\begin{matrix} _{s, \max} .Math. .Math. if .Math. .Math._{s} >_{s, \max} \\ _{s, \min} .Math. .Math. if .Math. .Math._{s} <_{s, \min} \\ otherwise .Math. .Math._{s} \end{matrix} & (20) \end{matrix}$

[0093] Afterwards, the angles of inclination .sub.s, .sub.s are converted to target values {right arrow over (z.sub.act)}=[z.sub.act,VL, z.sub.act,VR, z.sub.act,HL, z.sub.act,HR].sup.T for the change in length of the actuators 12, 14 of the active chassis. A conversion of the limited angle of pitch and angle of roll of the roadway 4 to the target values for lengths of the actuators 12, 14 is carried out by use of the transformation matrix T and by way of known translation ratios between actuator-related and wheel-related distances, i.sub.VA=

[00018] $\frac{z_{act, VL}}{{dz}_{a, VL}} = \frac{z_{act, VR}}{{dz}_{a, VR}}$ $and$ $i_{HA} = \frac{z_{act, HL}}{{dz}_{a, HL}} = \frac{z_{act, HR}}{{dz}_{a, HR}}$

for the front axle and the rear axle of the vehicle 2, as a result of which a diagonal matrix diag(i.sub.VA,i.sub.VA,i.sub.HA,i.sub.HA) is formed. In this case, the following relation with the transposed transformation matrix (16) is used for the actuator-related target values:

[00019] $\begin{matrix} \overset{.fwdarw.}{z_{act}} = {diag (i_{VA}, i_{VA}, i_{HA}, i_{HA})}^{T^{T}} [\begin{matrix} _{s, l .Math. im} \\ _{s, \lim} \end{matrix}] & (21) \end{matrix}$

[0094] In the above formulas, the maximum or minimum angles .sub.s,max, .sub.s,max, .sub.s,min, and .sub.s,min are adjustable matching parameters or target values, which can be varied depending on the driving situation in each case.

[0095] In an applied example, the following initial values are predetermined:

i.sub.VA=i.sub.HA=1; t.sub.v=t.sub.h=0,5; l.sub.v=l.sub.h=1,5(22)

.sub.s,lim=1/180; .sub.s,lim=0(23)

[0096] There results from this:

{right arrow over (z.sub.act)}=[0,026 0,0260,0260,026].sup.T(24)

[0097] This means that the front actuators 12 are moved 2.6 cm upwards and the rear actuators 14 are moved 2.6 cm downwards, wherein lengths of the respective actuators 12, 14 can be varied in accordance with the lengths given here.

[0098] FIG. 3 shows, in schematic illustration, a detail of the vehicle 2 in the area of the wheel 8 arranged at the front left, which, in this case, is joined via the actuator 12 associated with this wheel 8 at a suspension point 50 of the vehicle body 6 of the vehicle 2. Moreover, FIG. 3 shows the transverse distance t.sub.v of the wheel 8 from the center of gravity 25. Here, too, a transverse distance t.sub.v,act of the actuator 12 from the center of gravity 25 is indicated by a double arrow. A distance dz.sub.a,VL of the wheel 8 to the vehicle body 6 as well as a distance z.sub.act,VL of the actuator 12 from the suspension point 50 of the vehicle body 6 are also illustrated here.

[0099] Accordingly, for the rear left wheel 10, the distance dz.sub.a,HL thereof to the vehicle body as well as the distance thereof to from the center of gravity 25 are to be taken into account. For the actuator 14, which is associated with the rear left wheel 10, correspondingly a distance z.sub.act,HL to a suspension point of the vehicle body 6 as well as t.sub.h,act from the center of gravity 25 are to be taken into account.

[0100] In FIG. 4a, the vehicle 2 is illustrated schematically for upward slope travel on the roadway 4, in FIG. 4b in the horizontal plane of the roadway 4, and in FIG. 4c for downward slope travel, wherein in all three FIGS. 4a, 4b, 4c, a direction of travel of the vehicle 2 forwards is indicated by an arrow 52. Moreover, in FIGS. 4a, 4b and 4c, a front right wheel 54 of the vehicle 2 and a rear right wheel 56 of the vehicle 2 are illustrated. In this case, it is provided that the front right wheel 54 is joined via an actuator 58 at a suspension point of the vehicle body 6 of the vehicle 2, whereas the rear right wheel 56 is joined via an actuator 60 at a suspension point of the vehicle body 6.

[0101] With reference to the illustration of FIG. 1 and/or FIG. 3, the front right wheel 54 exhibits the distance dz.sub.a,VR to the vehicle body 6 and the distance t.sub.v from the center of gravity 25. The actuator 58 associated with the front right wheel 54 exhibits a distance z.sub.act,VR to the vehicle body 6 and a distance t.sub.v,act from the center of gravity 25 of the vehicle body. Accordingly, the rear right wheel 56 exhibits the distance dz.sub.a,HR to the suspension point of the vehicle body 6 and the distance to from the center of gravity 25. The actuator 60 associated with the rear right wheel 56 exhibits a distance z.sub.act,HR to a suspension point of the vehicle body 6 and a distance t.sub.h,act from the center of gravity 25 of the vehicle body 6.

[0102] Taking into consideration the above-described steps of the method according to the invention, the actuators 14, 60, which join the rear wheels 10, 56 at the rear axle of the vehicle 2 to the vehicle body 6 thereof, are lengthened by a greater distance for upward slope travel (FIG. 4a) in comparison to the two actuators 12, 58, which join the front wheels 8, 54 at the front axle of the vehicle 2 to the vehicle body 6 thereof. During a drive on a horizontally oriented roadway (FIG. 4b), the lengths of the actuators 12, 14, 58, 60 are adjusted to be equal in length. For downward slope travel, which is indicated on the basis of FIG. 4c, the actuators 12, 58, which join the two front wheels 8, 54 to the vehicle body 6 of the vehicle 2, are lengthened by a greater distance than the actuators 14, 60, which join the wheels 10, 56 of the rear axle of the vehicle 2 to the vehicle body 6 thereof. However, the lengthening of the actuators 12, 58 at the front axle in comparison to the actuators 14, 60 at the rear axle in the case of downward slope travel is less than the lengthening of the actuators 14, 60 in comparison to the actuators 12, 58 in the case of upward slope travel.

METHOD FOR COMPENSATING FOR AN INCLINATION

Assignee

Inventors

Cpc classification

Classification Explorer

B60G17/01908

PERFORMING OPERATIONS; TRANSPORTING

Classification Explorer

B60G2400/10

PERFORMING OPERATIONS; TRANSPORTING

Classification Explorer

B60G17/0165

PERFORMING OPERATIONS; TRANSPORTING

Classification Explorer

B60G2400/252

PERFORMING OPERATIONS; TRANSPORTING

Classification Explorer

B60G2500/32

PERFORMING OPERATIONS; TRANSPORTING

Classification Explorer

B60G17/0195

PERFORMING OPERATIONS; TRANSPORTING

Classification Explorer

G01C9/00

PHYSICS

Classification Explorer

B60G2600/02

PERFORMING OPERATIONS; TRANSPORTING

Classification Explorer

B60G2800/702

PERFORMING OPERATIONS; TRANSPORTING

Classification Explorer

B60G2800/019

PERFORMING OPERATIONS; TRANSPORTING

International classification

Classification Explorer

B60G17/0165

PERFORMING OPERATIONS; TRANSPORTING

Classification Explorer

B60G17/019

PERFORMING OPERATIONS; TRANSPORTING

Abstract

Claims

Description