DE102019206898A1 - Method for operating a chassis of a motor vehicle - Google Patents

Abstract

The invention relates to a method for operating a chassis (4) of a motor vehicle (2), comprising the steps:
(S100) determining a value (W) representative of a frequency of motor vehicle movements,
(S200) comparing the value (W) representative of a frequency of motor vehicle movements with a threshold value (SW1), and evaluating a value representative of a vertical acceleration (x ” _s ) of a sprung mass (m _s ) of the motor vehicle (2) by one Determine the ADD force component (F _ADD ) when the value (W) is representative of a frequency of motor vehicle movements less than the threshold value (SW1), and.
(S300) determining a target actuating force (F _target ) while evaluating at least the ADD force component (F _ADD ).

Description

The invention relates to a method for operating a chassis of a motor vehicle.

The chassis of a motor vehicle is understood to mean the entirety of all parts of the motor vehicle that connect a chassis of the motor vehicle to the roadway via the wheels. The chassis includes components such as wheels, wheel carriers, wheel bearings, brakes, wheel suspension, subframe, suspension including stabilizer, shock absorber and steering.

Together with the shock absorbers, the suspension ensures a compromise between driving comfort and driving safety. The occupants of the motor vehicle should on the one hand be protected from unpleasant lifting, pitching and rolling vibrations and impacts, and on the other hand the most uniform possible grip should be achieved.

Continuous Damping Control (also CDC or Skyhook chassis) is an electronic damping system (adaptive chassis / suspension) for motor vehicles.

Continuous Damping Control gives the motor vehicle a significantly higher level of driving safety, dynamism and comfort by continuously varying and optimizing the damping for each individual wheel. In the millisecond range, a separate control unit evaluates and calculates sensor signals on the motor vehicle for body, wheel and lateral acceleration the required damping and adjusts it directly on the corresponding shock absorber by means of an electrically controllable valve. The control loop follows the Skyhook principle. This aims to immobilize the vehicle body, regardless of the driving and road conditions - comparable to connecting the body to a fixed "skyhook" while driving, which should move parallel to the sky like a litter.

From the U.S. 5,682,980 , the WO 2014/066469 A1 , the WO 2017/147406 A1 , the US 2010/0121529 A1 , the CN 105974821 A and so and so US 2017/0240019 A1 such damping systems are known.

It is also known to evaluate vertical speeds of the motor vehicle or a damper speed in order to determine a setpoint damping force, it being further provided that different control strategies are used depending on whether a threshold value is exceeded or not reached.

Such methods are not suitable for active suspensions or active wheel suspensions.

There is therefore a need to show ways in which improvements can be achieved here.

• Bestimmen eines Wertes repräsentativ für eine Frequenz von Kraftfahrzeugbewegungen,
• Vergleichen des Wertes repräsentativ für eine Frequenz von Kraftfahrzeugbewegungen mit einem Schwellwert und Auswerten eines Wertes repräsentativ für eine vertikale Beschleunigung einer gefederten Masse des Kraftfahrzeugs um eine ADD-Kraftkomponente zu bestimmen, wenn der Wert repräsentativ für eine Frequenz von Kraftfahrzeugbewegungen kleiner als der Schwellwert ist, und
• Bestimmen einer Ziel-Stellkraft unter Auswertung zumindest der ADD-Kraftkomponente.

The object of the invention is achieved by a method for operating a chassis of a motor vehicle, with the steps:

• Determining a value representative of a frequency of motor vehicle movements,
• Comparing the value representative of a frequency of motor vehicle movements with a threshold value and evaluating a value representative of a vertical acceleration of a sprung mass of the motor vehicle in order to determine an ADD force component if the value is representative of a frequency of motor vehicle movements less than the threshold value, and
• Determining a target actuating force while evaluating at least the ADD force component.

In other words, the ADD force component is weakened above a cutoff frequency to avoid high frequency problems.

A simple method for active suspensions or active wheel suspensions is thus provided.

According to one embodiment, the ADD force component is set to zero if the value is greater than or equal to the first threshold value and / or a second threshold value, the second threshold value being greater than the first threshold value. A determination of the ADD force component is therefore not necessary if the value is greater than or equal to the first threshold value and / or a second threshold value. If only one threshold value is provided, there are only two frequency ranges of the motor vehicle movements, while with two threshold values there are three frequency ranges. In this way, the process for active suspensions or active wheel suspensions can be further refined.

According to a further embodiment, the ADD force component is determined ratiometrically if the value is greater than the first threshold value and less than the second threshold value. There are thus three frequency ranges, namely in addition to one range for low and high frequencies, a further range for medium frequencies, for which the ADD force component is determined ratiometrically. This allows the first FDD force component to be mixed in gently and avoids problems at high frequencies.

According to a further embodiment, a factor consisting of a difference between the second threshold value and the value divided by the difference between the second threshold value and the first threshold value is taken into account for the ratiometric determination of the ADD force component. In this way, the gentle mixing of the first FDD force component can be achieved particularly smoothly and free from jumps or discontinuities.

According to a further embodiment, a further force component is determined as a function of a vertical speed of the sprung mass and taken into account when determining the target actuating force. In this way, the process for active suspension systems or active wheel suspensions can be further refined.

According to a further embodiment, a further force component is determined as a function of a prediction of a vertical deflection in front of a tire contact patch and taken into account when determining the target actuating force. In other words, e.g. the unevenness of the road ahead of the vehicle with a sensor, e.g. Potholes, recorded and evaluated in order to determine the prediction of a vertical deflection in front of a tire contact patch. In this way, the process for active suspension systems or active wheel suspensions can be further refined.

According to a further embodiment, a further force component is determined as a function of a spring travel and taken into account when determining the target actuating force. In this way, the process for active suspension systems or active wheel suspensions can be further refined.

The invention also includes a computer program product, a control device and a motor vehicle with such a control device.

• 1 in schematischer Darstellung Komponenten eines Fahrwerks eines Kraftfahrzeugs.
• 2 in schematischer Darstellung Komponenten eines Steuergeräts zur Steuerung des in 1 gezeigten Fahrwerks.
• 3 in schematischer Darstellung einen weiteren Verfahrensablauf zum Betrieb des in 1 gezeigten Fahrwerks.
• 4 in schematischer Darstellung weitere Komponenten des in 1 gezeigten Fahrwerks.

The invention will now be explained with reference to a drawing. Show it:

• 1 components of a chassis of a motor vehicle in a schematic representation.
• 2 Components of a control unit for controlling the in 1 shown chassis.
• 3 a schematic representation of a further process sequence for operating the in 1 shown chassis.
• 4th a schematic representation of further components of the in 1 shown chassis.

It gets on first 1 Referenced.

A model of a quarter of a chassis is shown 4th of a motor vehicle 2 , such as a car.

The model components shown are a sprung mass m _s and an unsprung mass m _u of the motor vehicle 2 , a spring constant ks of the chassis 4th , another spring constant kt, for example representative of a spring behavior of a tire of the chassis 4th and a variable actuating force F _s of the chassis 4th . Also referred to x _r a vertical deflection of the tire over the ground, x _s a vertical deflection of the sprung mass m _s and x _u a vertical deflection of the unsprung mass m _u .

A control unit 6th is designed to send sensor signals to the motor vehicle 2 for body, wheel and lateral acceleration and to determine a required actuating force from this and to set this directly on the corresponding actuator, e.g. by means of an electrically controllable valve, in such a way that the vehicle body of the motor vehicle is immobilized regardless of the driving and road conditions 2 is sought. In other words, a connection to a fixed “sky hook”, ie the virtual attachment point Sky, is sought during a journey, so that the vehicle body moves like a litter parallel to the sky.

The control unit tries during operation 6th the variable actuating force F _s of the chassis 4th a target operator F _target to track.

For this purpose and for the tasks and functions described below, the control unit 6th Hardware and / or software components.

It is now additionally on 2 Referenced.

The control unit 6th calculates a target positioning force F _target which contains several force components. In other words, the target force F _target is made up of a plurality of force components additively.

A first force component, an ADD force component F _ADD , is used by the control unit 6th depending on one vertical acceleration x ” _s the sprung mass m _s of the motor vehicle 2 using a PDD factor P _PDD certainly: $${\text{F.}}_{\text{ADD}}={\text{P}}_{\text{ADD}}*\text{x}\text{'}{\text{'}}_{\text{s}}$$

The control unit 6th determines the ADD force component F _ADD depending on a vertical acceleration x ” _s the sprung mass m _s of the motor vehicle 2 but only if a value W. representative of a frequency of motor vehicle movements smaller than a first threshold value SW1 is.

If, on the other hand, the value W. greater than or equal to the first threshold value SW 1 is, in the present exemplary embodiment, the ADD force component F _ADD set to zero: $${\text{F.}}_{\text{ADD}}=0$$

In this case, the value of the ADD force component can differ from the present exemplary embodiment F _ADD to a value greater than zero, but less than the value of the ADD force component F _ADD be set.

In the present exemplary embodiment, the control unit determines 6th the value W. according to the following formula: $$\text{W.}=\left(\text{x}\text{'}{\text{'}}_{\text{s}}{}^2/\text{x}{\text{'}}_{\text{s}}{}^2\right){1/2}^{}$$

Notwithstanding the present exemplary embodiment, other methods for determining the value can also be used W. representative of a frequency of motor vehicle movements of the motor vehicle 2 be used.

Furthermore is the control unit 6th trained to value W. with a second threshold SW2 to compare, where the the second threshold value SW2 greater than the first threshold SW1 is.

If the value W. greater than the first threshold SW1 and less than the second threshold value SW2 is definitely the control unit 6th the ADD force component F _ADD ratiometric. The control unit determines this 6th a factor consisting of a difference between the second threshold value SW2 and the value W. , divided by the difference from the second threshold value SW2 and the first threshold SW1 : $${\text{F.}}_{\text{ADD}}={\text{P}}_{\text{ADD}}*\text{x}\text{'}{\text{'}}_{\text{s}}*\left(\text{SW}2-\text{W.}\right)/\left(\text{SW}2-\text{SW}1\right)$$

Another force component, a Shyhook force component F _sky , is used by the control unit 6th depending on the vertical speed x ' _s the sprung mass m _s of the motor vehicle 2 using a P _sky factor P _sky certainly: $${\text{F.}}_{\text{Sky}}={\text{P}}_{\text{Sky}}*\text{x}{\text{'}}_{\text{s}}$$

Another force component, a spring force compensation force component F _PDD , is used by the control unit 6th as a function of a spring travel xs - xu of the motor vehicle 2 using a P _PDD factor P _PDD certainly: $${\text{F.}}_{\text{PDD}}={\text{P}}_{\text{PDD}}*\left({\text{x}}_{\text{s}}-{\text{x}}_{\text{u}}\right)*-{\text{k}}_{\text{s}}$$

Another force component, preview spring force compensation force component F _Prev , is used by the control unit 6th depending on a depending on a preview of the vertical deflection x _r the reason before a tire footprint using a P _Prev factor P _Prev certainly: $${\text{F.}}_{\text{Prev}}={\text{P}}_{\text{Prev}}*{\text{x}}_{\text{r}}*{\text{k}}_{\text{s}}$$

Thus, in the present exemplary embodiment, the control unit continues 6th certain target force F _target as follows: $${\text{F.}}_{\text{Target}}={\text{F.}}_{\text{ADD}}+{\text{F.}}_{\text{Sky}}+{\text{F.}}_{\text{PDD}}+{\text{F.}}_{\text{Prev}}$$

The values for the respective factors P _ADD , P _Sky , P _PDD and P _Prev can be predetermined constants or can be taken from lookup tables.

It is also possible to change the values for the respective factors P _ADD , P _Sky , P _PDD and P _Prev adapt in real time, for example depending on a signal quality, a driving mode, a road condition and / or energy requirement.

Furthermore, different from the present exemplary embodiment, further force components can also be determined and when determining the target actuating force F _target be taken into account.

The description is based on a model of a quarter vehicle with purely vertical movements. However, the same approach can be applied to the pitch and roll motion of a full motor vehicle 2 be applied. In such cases, the pitch and roll speeds and accelerations of the sprung mass m _s also when calculating the target force F _target used instead of just vertical speed x ' _s and acceleration x ” _s .

It will now be made with additional reference to FIG 3 a process sequence for operating the chassis 4th explained.

In a first step S100 determines the control unit 6th the value as already described above W. representative of a frequency of motor vehicle movements of the motor vehicle 2 .

For this purpose, the control unit reads in the present exemplary embodiment 6th a value representative of a vertical speed x ' _s the sprung mass m _s and a value representative of vertical acceleration x ” _s the sprung mass m _s one.

The value representative of a vertical speed x ' _s the sprung mass m _s and the value representative of vertical acceleration x ” _s can be recorded with appropriate speed and acceleration sensors. However, provision can also be made for speed values to be determined from recorded acceleration values by means of numerical integration.

In a further step S200 compares the control unit 6th the recorded value W. with the first threshold SW1 and the second threshold SW2 .

If the value W. representative of a frequency of motor vehicle movements less than the threshold value SW1 the value becomes representative of a vertical acceleration x ” _s the sprung mass m _s of the motor vehicle 2 evaluated as described above for the ADD force component F _ADD to determine.

If, on the other hand, the value W. greater than or equal to a second threshold value SW2 becomes the ADD force component F _ADD set to zero.

If the value W. greater than the first threshold SW1 and less than the second threshold value SW2 is becomes the ADD force component F _ADD determined ratiometrically as described above, in that in the present exemplary embodiment a factor is determined and taken into account which is the difference between the second threshold value SW2 and the value W. , divided by the difference from the second threshold value SW2 and the first threshold SW1 , consists.

In a further step S300 determines the control unit 6th the target force F _target by adding the ADD force component F _ADD , the Skyhook force component F _Sky , the spring force compensation force component F _PDD and the preview spring force compensation force component F _Prev .

In contrast to the present exemplary embodiment, the order of the steps can be different. In addition, several steps can also be carried out in time or simultaneously.

A simple method for active suspensions or active wheel suspensions is thus provided.

It is now additionally on 4th Referenced.

The 4th shows a damper 8th of the chassis 4th .

The damper 8th has an actuator as an additional component 10 on, which in the present embodiment is a motor-driven pump, with the hydraulic fluid in the damper 8th can be pressurized.

Furthermore, in the present embodiment, the damper 8th a compression control valve 12 and a check valve 14th assigned.

Further, additional components in the present exemplary embodiment are an actuator controller 16 to control the actuator 10 and a valve controller 18th to control the compression control valve 12 and the check valve 14th .

Here are the actuator controller 16 and the valve controller 18th each designed as a separate controller. A particularly simple and also modular structure can thus be provided. The actuator controller 16 and the valve controller 18th can also exchange data.

List of reference symbols

2

Motor vehicle

4th

landing gear

6

Control unit

8th

mute

10

Actuator

12

Compression control valve

14th

Check valve

16

Actuator controller

18th

Valve controller

F _ADD

ADD force component

F _s

Actuating force

F _PDD

Spring force compensation force component

F _Prev

Preview spring force compensation force component

F _Sky

Skyhook force component

F _target

Target force

k _s

Spring constant

k _t

Tire spring rate

m _s

sprung mass

m _u

unsprung mass

P _ADD

ADD factor

P _Sky

Skyhook factor

P _PDD

PDD factor

P _Prev

Preview factor

SW1

first threshold

SW2

second threshold

W.

value

x _r

vertical displacement above ground

x _s

vertical deflection of the sprung mass

x _u

vertical deflection of the unsprung mass

x ' _s

vertical speed of sprung mass

x ' _u

vertical speed of unsprung mass

x ” _s

vertical acceleration of the sprung mass

x ” _u

vertical acceleration of the unsprung mass

S100

step

S200

step

S300

step

QUOTES INCLUDED IN THE DESCRIPTION

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

Patent literature cited

• US 5682980 [0006]
• WO 2014/066469 A1 [0006]
• WO 2017/147406 A1 [0006]
• US 2010/0121529 A1 [0006]
• CN 105974821 A [0006]
• US 2017/0240019 A1 [0006]

Claims (16)

Method for operating a chassis (4) of a motor vehicle (2), comprising the steps: (S100) determining a value (W) representative of a frequency of motor vehicle movements, (S200) comparing the value (W) representative of a frequency of motor vehicle movements with a threshold value (SW1), and evaluating a value representative of a vertical acceleration (x ” _s ) of a sprung mass (m _s ) of the motor vehicle (2) in order to determine an ADD force component (F _ADD ) if the value (W) is representative of a frequency of motor vehicle movements less than the threshold value (SW1). (S300) determining a target actuating force (F _target ) while evaluating at least the ADD force component (F _ADD ). Procedure according to Claim 1 , wherein in step (S200) the ADD force component (F _ADD ) is set to zero if the value (W) is greater than or equal to the first threshold value (SW1) and / or a second threshold value (SW2), the second Threshold (SW2) is greater than the first threshold (SW1). Procedure according to Claim 1 or 2 wherein in step (S200) the ADD force component (F _ADD ) is determined ratiometrically if the value (W) is greater than the first threshold value (SW1) and smaller than the second threshold value (SW2). Procedure according to Claim 3 , wherein for the ratiometric determination in step (S200) of the ADD force component (F _ADD ) a factor consisting of a difference between the second threshold value (SW2) and the value (W) divided by the difference between the second threshold value (SW2 ) and the first threshold value (SW1) is taken into account. Method according to one of the Claims 1 to 4th , whereby another force component (F _Sky ) is determined as a function of a vertical speed (x ' _s ) of the sprung mass (m _s ) and is taken into account when determining the target actuating force (F _Target ). Method according to one of the Claims 1 to 5 , a further force component (F _Prev ) being determined as a function of a prediction of a vertical deflection (x _r ) in front of a tire contact patch and being taken into account when determining the target actuating force (F _Target ). Method according to one of the Claims 1 to 6th , a further force component (F _PDD ) being determined as a function of a spring deflection (x _s - x _u ) and being taken into account when determining the target actuating force (F _target ). Computer program product designed to carry out a method according to one of the Claims 1 to 7th . Control device (6) for operating a chassis (4) of a motor vehicle (2), the control device (6) being designed to read in a value (W) representative of a frequency of motor vehicle movements, the value (W) representative of a frequency of To compare motor vehicle movements with a threshold value (SW1) and to evaluate a value representative of a vertical acceleration (x ” _s ) of a sprung mass (m _s ) of the motor vehicle (2) to determine an ADD force component (F _ADD ) when the Value (W) is representative of a frequency of motor vehicle movements less than the threshold value (SW1), and for determining a target actuating force (F _Target ) while evaluating at least the ADD force component (F _ADD ). Control unit (6) Claim 9 , the control device (6) being designed to set the ADD force component (F _ADD ) to zero if the value (W) is greater than or equal to the first threshold value (SW1) and / or a second threshold value (SW2), wherein the second threshold value (SW2) is greater than the first threshold value (SW1). Control unit (6) Claim 9 or 10 , wherein the control device (6) is designed to determine the ADD force component (F _ADD ) ratiometrically when the value (W) is greater than the first threshold value (SW1) and smaller than the second threshold value (SW2). Control unit (6) Claim 11 , wherein the control device (6) is designed for the ratiometric determination of the ADD force component (F _ADD ) to take into account a factor derived from a difference between the second threshold value (SW2) and the value (W), divided by the difference from the second Threshold (SW2) and the first threshold (SW1) is formed. Control unit (6) after one of the Claims 9 to 12 , the control unit (6) being designed to determine a further force component (F _Sky ) as a function of a vertical speed (x ' _s ) of the sprung mass (m _s ) and to take this into account when determining the target actuating force (F _Target ) . Control unit (6) after one of the Claims 9 to 13 , the control device (6) being designed to determine a further force component (F _Prev ) as a function of a prediction of a vertical deflection (x _r ) in front of a tire contact patch and to take this into account when determining the target actuating force (F _Target ). Control unit (6) after one of the Claims 9 to 14th , the control device (6) designed to determine a further force component (F _PDD ) as a function of a spring deflection (x _s - x _u ) and to take this into account when determining the target actuating force (F _target ). Motor vehicle (2) with a control unit (6) according to one of the Claims 9 to 15th .

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