Method for combined determining of a momentary roll angle of a motor vehicle and a momentary roadway cross slope of a curved roadway section traveled by the motor vehicle

Abstract

A method and device for the combined determining of a momentary vehicle roll angle of a motor vehicle and a momentary roadway cross slope of a curved roadway section traveled by the motor vehicle is disclosed. The momentary vehicle roll angle and momentary roadway cross slope are determined from chassis data and transverse dynamics data of the motor vehicle.

Claims

1. A method for combined determining of a momentary vehicle roll angle of a motor vehicle and a momentary roadway cross slope of a curved roadway section traveled by the motor vehicle, comprising the steps of: receiving a measured momentary transverse acceleration, a measured momentary yaw speed, and a measured momentary speed of the motor vehicle transmitted by a transverse acceleration sensor, a yaw rate sensor, and a speed sensor of the motor vehicle, respectively, at a control device; and determining the momentary vehicle roll angle and the momentary roadway cross slope by the control device from chassis data and transverse dynamics data of the motor vehicle; wherein the chassis data comprises a momentary chassis roll angle of a chassis of the motor vehicle and a momentary tire roll angle of tires of the motor vehicle and wherein the transverse dynamics data comprises the measured momentary transverse acceleration of the motor vehicle; wherein the step of determining the momentary vehicle roll angle includes a step (S1) of calculating the momentary vehicle roll angle (φ.sub.A) from the measured momentary transverse acceleration (a.sub.y.sup.sensor), the measured momentary speed (v.sub.x) of the motor vehicle, and the measured momentary yaw speed (d/dtΨ) of the motor vehicle according to the following equation:
φ.sub.A=(1/g) (a.sub.y.sup.Sensor−v.sub.x d/dtΨ), where g is gravitational acceleration; wherein the step of determining the momentary roadway cross slope includes calculating the momentary roadway cross slope (φ.sub.FB) from the momentary vehicle roll angle (φ.sub.A) calculated in step S1, the momentary chassis roll angle (w), and the momentary tire roll angle (φ.sub.R) according to the following equation:
φ.sub.FB=φ.sub.A−w−φ.sub.R; wherein the momentary chassis roll angle is determined from a height difference of a momentary height of a left strut of the motor vehicle relative to a momentary height of a right strut of the motor vehicle; and wherein the momentary tire roll angle of tires is determined from a height difference of a momentary height of a left tire of the motor vehicle relative to a momentary height of a right tire of the motor vehicle.

2. A device for combined determining of a momentary vehicle roll angle of a motor vehicle and a momentary roadway cross slope of a curved roadway section traveled by the motor vehicle, the device comprising: a transverse acceleration sensor; a yaw rate sensor; a speed sensor; and a control device configured to perform the method of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a roughly schematic flow diagram of the method according to the invention, and

(2) FIG. 2 is a motor vehicle having a device according to the invention to set the curve incline of a motor vehicle, wherein FIG. 2a shows a top view and FIG. 2b shows a back view of the motor vehicle.

DETAILED DESCRIPTION OF THE DRAWINGS

(3) In FIG. 1, a flow diagram of the method according to the invention is depicted roughly schematically, according to which, in a first step S1, firstly a momentary roll angle φA of the motor vehicle 1 relative to a horizontal reference plane 21 (cf. FIG. 2b) is determined and in a subsequent step S2, the momentary roadway cross slope φF of the curved roadway section 20 being travelled by the motor vehicle 1 is determined relative to the reference plane 21.

(4) Here, the horizontal reference plane 21 is set via the direction vector {right arrow over (g)} of the center of gravity which extends in the orthogonal direction to the reference plane 21.

(5) To calculate the roll angle φ.sub.A, knowledge of the momentary speed v.sub.x of the motor vehicle 1 is required, which can be determined by means of a speed sensor 6 integrated into the motor vehicle 1. Furthermore, for the calculation of the roll angle φA a knowledge of the momentary transverse acceleration a.sub.y.sup.Sensor is also required, which in turn is able to be determined by means of a transverse acceleration sensor 3 integrated into the motor vehicle 1.

(6) In the transverse acceleration a.sub.y.sup.Sensor measured by the transverse acceleration sensor 3, according to the equation
a.sub.y.sup.Sensor=a.sub.y cos φ.sub.A+g sin φ.sub.A

(7) so-called “g proportions” caused by the center of gravity are obtained. In the equation above, g is the gravitational acceleration and ay is the transverse acceleration without the g proportion. For small roll angles φA this equation can be simplified by means of Taylor expansion as follows:
a.sub.y.sup.Sensor=a.sub.y+g φ.sub.A

(8) From the equation which is known to the person skilled in the art and describes the driving dynamics of a motor vehicle
a.sub.y.sup.Sensor=d/dt v.sub.y+v d/dt ψ
it follows, for small speed changes (d/dt v.sub.y≈0) by combination with the above equation:
φ.sub.A=(1/g) (a.sub.y.sup.Sensor−v.sub.xd/dt ψ)

(9) The roll angle φ.sub.A can also be calculated from this equation. Here, d/dt ψ is the yaw speed of the motor vehicle 1 which can be determined by means of a yaw rate sensor 5.

(10) By using the different indices y and x, it is therefore expressed that a direction vector of the momentary transverse acceleration a.sub.y.sup.Sensor (in the Y direction) points in an orthogonal direction to the corresponding direction vector of the momentary speed v.sub.x of the motor vehicle (in the X direction) (cf. also FIG. 2a). The Z direction runs orthogonally to both the X and the Y direction.

(11) The sensor output data of the acceleration sensor 3, therefore the momentary transverse acceleration a.sub.y.sup.Sensor, can be filtered by means of a suitable low-pass filter in order to filter out undesired high-frequency disturbances (for example due to unevenness in the roadway section 20 being travelled).

(12) Advantageously, the acceleration sensor 3 is arranged in the motor vehicle as far as possible to the front of the motor vehicle with regard to a vehicle longitudinal direction L of the motor vehicle 10 (cf. FIG. 2a).

(13) In step S2, the sought-after roadway cross slope φ.sub.FB is now calculated, based on a roll angle φ.sub.A calculated in step S1, using the equation
φ.sub.FB=φ.sub.A−w−φ.sub.R.

(14) Here, w is a momentary chassis roll angle set in the chassis of the motor vehicle and φR is a tire roll angle of the tires 13, 14 of the motor vehicle. In a simplified variant, the tire roll angle (p.sub.a can also be ignored (φ.sub.R=0).

(15) For the implementation of step S2, the momentary chassis roll angle w can be determined by means of suitable sensors 2. These sensors can determine a momentary height x.sub.l, x.sub.r of the height-adjustable struts 11, 12 allocated to the left or right tires 13, 14 of the motor vehicle 1, such that the momentary chassis roll angle w can be determined from the height difference Δx=|x.sub.l−x.sub.r| of the momentary height x.sub.l of the left strut 11 relative to a momentary height x.sub.r of the right strut 12.

(16) The tire roll angle φ.sub.R can also be determined in an analogous manner by means of suitable sensors 4. For this purpose, a height difference Δy=|y.sub.l−y.sub.r| of a momentary height y.sub.l, y.sub.r of the left tire 13 relative to the right tire 14 can be determined by means of such sensors 4. This height difference Ay can depend on a different wheel load of the left and right tires 13, 14 of the motor vehicle 1 as well as a different tire pressure-dependent stiffness of the left or right tires 13, 14. The sensors 4 can therefore comprise tire pressure sensors to measure the individual tire pressure in the tires 13, 14.

(17) In the depiction of FIG. 2, the motor vehicle 1 having a device 7 according to the invention for the implementation of the method according to the invention is now shown. FIG. 2a shows the motor vehicle 1 in a top view; FIG. 2b shows it in a rear view. The motor vehicle 1 comprises a control device 8 as well as an acceleration sensor 3, a yaw rate sensor 5, and a speed sensor 6 which are each connected for communication to the control device 8.

(18) The motor vehicle 10 comprises a chassis device which is able to be controlled by the control device 8, which can be formed in the manner of an electro-hydraulic active chassis. The chassis device comprises four actuators 11, 12 formed as height-adjustable struts, wherein an actuator 11, 12 is allocated to each wheel 13, 14 of the motor vehicle 10. By an individual adjustment of the height of the actuators 11, 12, a determined roll angle φ.sub.A can be set in the motor vehicle 10.

(19) Alternatively to the electro-hydraulic chassis device described above, a pneumatic spring-based chassis having a closed pressure supply can also be used. In such a pneumatic spring-based chassis, to adjust the struts, the air is pumped into a closed circuit by an air cell in the pneumatic spring and reversed, which enables a very quick transfer in and out of the struts to set the target curve incline in the chassis of the motor vehicle.

(20) In a further alternative to the electro-hydraulic active chassis, a chassis which is known by the term “ACTIVE CURVE SYSTEM” and which is hydraulically adjustable can be used, which works with an hydraulic pump driven by a belt drive and has an oil container in the motor chamber as well as a valve block and active stabilizer on each of the front and rear axles. Also, such a hydraulic chassis device can be used to set the target curve incline in the motor vehicle.

(21) For the implementation of the method according to the invention, the acceleration sensor 3 transmits the momentary sensor transverse acceleration ay, the speed sensor 6 transmits the momentary speed v.sub.x and the yaw rate sensor 5 of the motor vehicle 1 transmits the momentary yaw speed d/dt ψto the control device 8. The control device 8 can comprise a control unit 9 (ECU) and a storage unit 10 which is connected for communication to the control unit 9. The control unit 9 and the storage unit 10 can be formed in the manner of a conventional microcontroller, wherein numerous technical implementation possibilities are known to the person skilled in the art.

(22) The method according to the invention is implemented in the control device 8 using the input parameters referred to above (momentary speed of the motor vehicle v.sub.x, yaw speed d/dt ψ, momentary sensor transverse acceleration a.sub.y.sup.Sensor). The momentary vehicle roll angle φ.sub.A of the motor vehicle is calculated by the control device 8 for this purpose according to step S1 of the method according to the invention. From the momentary vehicle roll angle φ.sub.A, according to step S2, the momentary roadway cross slope φ.sub.FB of the curved roadway section 20 being travelled is calculated.

(23) To determine the momentary chassis roll angle w in the scope of the implementation of step S2, the device 7 according to the invention has suitable chassis sensors 2 which determine each momentary height x.sub.l, x.sub.r of the height-adjustable struts, 11, 12, such that the control device 8 can determine the momentary chassis roll angle 2 from the height difference Δx=|x.sub.l−x.sub.r| of the momentary height x.sub.l of the struts 11 allocated to the two left tires 13 relative to the momentary height x.sub.r of the struts 12 allocated to the two right tires 14. In an analogous manner, the tire roll angle φ.sub.R can also be determined by means of the (tire pressure) sensors 4.

(24) In a developing variant, it can also be conceived to determine the momentary chassis roll angle w not as explained above by means of a suitable sensor system 2; rather, according to this alternative, it can be conceived to calculate an optimum target roll angle w.sub.Soll by means of a suitable method, for example depending on determined input parameters such as, for example, the momentary transverse acceleration a.sub.y.sup.Sensor and the momentary speed v.sub.x of the motor vehicle 1 and a momentary roadway curvature K of the roadway section 20 being travelled from these initial parameters, the target roll angle w.sub.Soll being set in the struts 11, 12 of the chassis of the motor vehicle 1 in order to reduce transverse forces acting on the passengers of the motor vehicle 1 during travelling of the curved roadway section 20 and thus to increase the driving comfort for the passenger. The calculation of the target roll angle w.sub.Soll thus firstly occurs depending on the momentary roadway cross slope φ.sub.FB. The calculation of the target roll angle w.sub.Soll can, for example, be carried out by the control unit 9 of the control device 8. The height-adjustable struts 11, 12 can therein be controlled by the control device 8 such that the desired target roll angle w.sub.Soll is set in the chassis of the motor vehicle 1. Since, in the case of such a simplified calculation of the target roll angle w.sub.Soll, the momentary roadway cross slope φ.sub.FB remains unconsidered, it is offered to calculate this by means of the method according to the invention and to consider this during the setting of the chassis roll angle w.sub.Soll using the struts 11, 12 of the vehicle.