WO2007054165A1

WO2007054165A1 - Chassis design and chassis control for a multi-axle double-track vehicle

Info

Publication number: WO2007054165A1
Application number: PCT/EP2006/009613
Authority: WO
Inventors: Andreas Goubeau; Josef Forster; Andreas Gleser; Christopher Eschenbach; Pavel Kvasnicka; Sergey Repp; Sebastian Hertlen; Axel Pauly
Original assignee: Bayerische Motoren Werke Aktiengesellschaft
Priority date: 2005-11-08
Filing date: 2006-10-05
Publication date: 2007-05-18
Also published as: DE102005053222A1

Abstract

The invention relates to a chassis design and chassis control for a multi-axle double-track vehicle with an active suspension system comprising individual actuators for each wheel to influence the relative movement between the wheel and the vehicle body as well as a control unit for generating actuating signals for the actuators in accordance with input variables representing the travel condition. The vehicle body is actively lowered, preferably on both axles, on the inner side of a curve by means of the associated actuator during cornering of the vehicle. The vehicle body is thus largely prevented from performing a rolling motion with the aid of said control strategy combined with compression on the outer side of the curve. The kinematics of the wheel suspension are designed such that the wheels of all axles are subjected to a change in camber relative to the vehicle body, i.e. towards larger negative camber angles, as compression travel increases such that the potential of the wheels located on the outer side of the curve to transmit force is boosted. Additionally, toe-in modifications influencing the road performance can be effected preferably on all axles during cornering via the spring excursion.

Description

Suspension design and control for a multi-axle two-track vehicle

The invention relates to a chassis design and control for a multi-axle two-track vehicle with an active suspension system with individual wheel actuators to influence the relative movement between the wheel and the vehicle body and with a control unit for generating actuating signals for the actuators in response to the Driving state representing input variables. For the technical environment reference is made to DE 10 2004 039 973 A1.

Are known Fzg.- trolleys with active roll stabilization, in which an on or off spring movement between the respective wheel and vehicle body is largely prevented, with the aim, just as when driving straight even when cornering a substantially horizontally oriented Fzg. -Aufbau to obtain. For this purpose, the chassis can have either so-called active stabilizers or wheel-individual actuators with which a relative movement can be generated specifically in the vertical direction between the respective wheel and the vehicle.

For the latter embodiment, further improvements are to be shown hereby (= object of the present invention).

The solution to this problem is for a chassis design and control according to the preamble of claim 1, characterized in that during cornering of the vehicle, the vehicle body at least on one axis, preferably on both or all axes, on the inside of the curve side by means of the associated actuator active is lowered and thus by this control strategy in conjunction with the compression on the outside of the curve a rolling movement of the structure is largely prevented, the kinematics of the wheel suspension is designed such that the wheels of all axes with increasing compression travel a camber change relative to the vehicle body towards experience larger negative camber angles. Advantageous developments are content of the dependent claims. Thus, a chassis, in particular a four-wheeled two-track motor vehicle with four active control elements (= actuators) for wheel-individual influencing the relative movement between each wheel and the vehicle body and with a drive strategy for a controllable active suspension system, which lowers the vehicle body on the inside of the curve when cornering and (in conjunction with the centrifugal force-dependent, automatic lowering or compression of the vehicle body. Construction on the outside of the curve) prevents rolling motion of the vehicle body and, consequently, generates a favorable for the lateral force transmission potential of the tire negative camber angle. The latter should apply to all wheels of the vehicle. The fact that now takes place when cornering on all wheels compression, or should the wheel suspension be altogether designed such that with such a compression (= reducing the vertical distance between the wheel center and Fzg. Aubau) on each wheel a camber change relative to the vehicle body in the direction of increasing negative camber angle adjusts. This increases, in addition to the inhibited rolling motion of the vehicle, the lateral force transmission potential at the outer wheels, which are governed by the increased wheel load during cornering for the transmission of power.

While the deflection takes place on the outside wheels centrifugally by itself, is preferably caused by corresponding Aktuatoransteuerung also on both or all inside wheels a deflection, which due to appropriately designed Radführungskinematik at the same time an increase in the lateral force transmission potential and in particular the outside wheels or tires by the described Camber change caused. Thus, no camber angle loss, which can be detected in the conventional state of the art, can occur at the wheels due to an otherwise occurring body roll angle. In combination, the features of the chassis according to the invention with the actuators, the described drive strategy and the design of the wheel kinematics lead to the fact that the power transmission potential of the tires is increased when cornering. The camber angle of a tire is known to be the angle enclosed by the wheel plane and the road normal in the vehicle transverse plane. The camber angle is known to affect the power transmission potential of the tire. If the tire is tipped at the top to the outside of the curve, there is a loss of lateral force potential, ie the tire must roll for a greater lateral slip force at the same lateral force to be transmitted. The maximum transmittable lateral force is weakened by such a camber angle. Conversely, when the negative camber angle is opposite, the power transmission potential of the tire is increased to some extent and the required slip angle is reduced.

In conventionally sprung vehicles there is the problem that undergoes a rolling motion under the influence of a lateral acceleration of the vehicle body. If the suspension for attachment of the wheels to the vehicle body has independent wheel suspensions, the rolling motion of the vehicle body transfers to the wheels. This roll motion conventionally causes an adverse camber change of the wheels, which weakens the lateral force transmission potential of the tires.

The camber angle of a wheel relative to the roadway is composed of the described rolling motion of the body and a portion of the wheel relative to the body. This camber angle between body and wheel depends on the suspension kinematics of the deflection of the wheels. In design position, the static camber is set. In addition, elasticity in the handlebars and bearings causes unfavorable camber changes under lateral force.

In order to achieve maximum tracking when cornering, avoiding a positive fall caused by the rolling motion and the lateral forces and, if possible, to maintain negative camber or to reinforce such a negative camber. This is achievable by negative static fall as well as an increase of the negative fall over the spring deflection. These measures are in conflict with the straight-ahead requirements of the vehicle, where a camber angle on the order of zero is desirable in order to minimize tire wear and straight-line interference. According to the invention, this described conflict of objectives can be resolved in order to combine the extension of the driving dynamic limits and a clear gain in driving safety with a reduction in tire wear and an improvement in the straight-line running characteristics. In order to achieve a camber angle of 0 ° or a slight negative camber to the road on the outside wheel when cornering, thus the fall increase in compression in the direction of negative camber to compensate for the resulting elasticity in the handlebars and bearings positive camber or slightly overcompensate, so that the static fall can be reduced and given a potential for improving the straight-line running in a chassis according to the invention.

The aforementioned actuators for influencing a relative movement between in each case one wheel and the vehicle body can be designed and arranged differently and have different active principles (preferably electromechanical or hydraulic). Each actuator can be connected in parallel with a support spring, so that it is designed to carry a part, or the actuators are executed fully supporting. Further, the suspension design can be made so that the travel when cornering preferably on all axes causes the driving behavior favorably influencing toe changes. By allowing compression movements of the wheels when cornering according to the features of the invention is namely in addition the possibility to influence the handling of the vehicle when cornering by toe changes of the wheels on the compression travel. This option is not given in actively roll-stabilized vehicles in which compression movements of both wheels are largely avoided. On the latter vehicles, the Wank steering, which is designed into the axle kinematics, has no influence, since the suspension travel is not utilized when cornering.

Since the rolling moment causing the rolling motion is proportional to the transverse acceleration acting on the vehicle, this lateral acceleration measured in or on the vehicle is suitable for driving the actuators. A direction detection recognizes the inside of the vehicle on the inside of the curve and controls the actuators of the inside of the vehicle on the inside of the bend according to the proposed driving strategy. In order to avoid a time delay through the actuator, is in an appendant electronic control and processing unit, the use of vehicle models using the steering angle signal possible. If the roll angle in the vehicle is available as a direct measurement signal, the control according to the invention of the active control elements can alternatively be realized by regulating the roll angle. Furthermore, there is the possibility to detect by measuring the suspension travel the outside of the curve, automatic compression of a vehicle side and nachzuführen the inside of the curve side by the control of the active control elements of the outside of the vehicle side.

For further explanation, reference is made to the accompanying figures, of which

Figure 1 shows a schematic representation of a two-track motor vehicle when cornering with passive roll suspension, while in

A schematic representation of a two-track motor vehicle when cornering with conventional active roll stabilization, and in

A schematic representation of a two-track motor vehicle at

Cornering is shown with inventive active roll stabilization and center of gravity lowering taking advantage of the fall increase in compression.

Shown is schematically only one axis of the vehicle.

FIG. 1 shows a two-track motor vehicle with passive roll suspension. On the presentation of a stabilizer spring has been omitted due to better clarity. The on-curve (when viewed from behind on the vehicle rear is a left turn) of the vehicle acting superstructure centrifugal force (= centrifugal force F _F | _ieh ) engages the vehicle body 1 at. The rolling moment effecting this causes the outer curve, the Fzg. -Aufbau bearing support spring 3 compress while the curve inner suspension spring 2 is stretched or lengthened. As a result of the rolling motion and the elasticities take the wheels 4 and 5 of the vehicle positive camber angle to the road. Although the suspension kinematics, represented by the links 6 and 7, can partially counteract this positive camber due to the rolling motion on the wheels 4 and 5, they can not completely compensate for them. 2 shows the schematic representation of a conventional actively roll-stabilized vehicle, which has active spring elements or the like, here so-called actuators 8 and 9, which can actively influence or change the distance between the vehicle body 1 and the wheels 4 and 5. The suspension kinematics shown by the arrangements of the handlebars 6 on the inside of the curve and the handlebars 7 on the outside of the vehicle has no significant influence on the position of the wheels, since the vehicle body 1 is held in its starting position when driving straight ahead. Due to the elasticities in the links 6, 7 and their bearings can despite the lack of rolling motion positive camber angle occur, which weaken the power transmission potential of the tires.

Fig. 3 shows a schematic representation of a vehicle with inventive suspension design and control. The vehicle body 3 is (vis-à-vis FIGS. 1, 2) visibly lowered so that the handlebars 6, 7 with their positions relative to the vehicle body 1 force the respective associated wheel 4 or 5 into negative camber (also to the vehicle body 1). In the inside of the curve actuator 8, the force arrow F _actively clarifies the control action, with the help of which the vehicle body is lowered, while the deflection on the outside of the vehicle side analogous to Fig.1 is passive.

With a chassis according to the invention, the inside wheel as shown in FIG. 3 is subjected to an impact position which is unfavorable at first glance when subjected to deflection by the suspension kinematics, as in the case of a passive roll-stabilized vehicle according to FIG. Due to the displacement of the wheel loads on an axle when cornering, however, the outside wheel dominates the power transmission in the horizontal plane, so that the power transmission potential of the axle is significantly increased by the measures described in total.

In the case of the vehicle with proposed suspension design and chassis control, the situation-dependent lowering of the center of gravity of the vehicle additionally has a positive effect on the driving dynamics. Namely, the height of the center of gravity of the vehicle, in conjunction with the effective lateral acceleration, determines the wheel load differences occurring at the wheels of an axle. Due to the degressive characteristic of the tire horizontal force as a function of the tire vertical force decreases with increasing wheel load difference of the wheels of an axle, the horizontal force potential of the entire axis. By lowering the center of gravity of the vehicle when cornering, the wheel load differences on both axles are reduced and the power transmission potential of the axles is increased.

In case of a system failure of the active control elements (actuators) behaves an inventive suspension as a conventional passive suspension, so that a roll angle occurs. Due to the existing camber increase in the direction of negative camber the camber angle loss due to the roll angle is counteracted, and prevents an excessive reduction of the lateral dynamic potential of the tire in case of failure of the active system.

Claims

claims

1. Suspension design and control for a multi-axis two-track vehicle with an active suspension system with individual wheel actuators (8, 9) for influencing the relative movement between the wheel (4, 5) and the vehicle body (1) and with a control unit for generating control signals for the actuators (8, 9) as a function of the driving state representing input variables, characterized in that when cornering of the vehicle of the vehicle body (1) at least on one of the axes, preferably on both or all axes, on the inside of the curve is actively lowered by means of the associated actuator (8, 9) and thus by this control strategy in conjunction with the compression on the outside of the bend a rolling movement of the body (1) is largely prevented, the kinematics of the wheel suspension (6, 7) such is designed so that the wheels of all axes with increasing compression travel a camber change relative to the vehicle body (1) out to experience larger negative camber angles.

2. chassis design according to claim 1, characterized in that the actuators (8, 9) for influencing the relative movement between each one wheel (4, 5) and the vehicle body (1) latter are carried out partially carrying or fully supporting.

3. chassis design according to claim 1 or 2, characterized in that the actuators (8, 9) have an electromechanical or a hydraulic action principle.

4. Suspension design according to one of the preceding claims, characterized in that the spring travel when cornering

, preferably on all axes causes the driving behavior affecting toe-in changes.

5. chassis design and control according to one of the preceding claims, characterized in that by the lowering of the vehicle body on the inside of the curve, a roll angle in the direction of the inside of the curve is generated in the sense of a Kurvenlegers.

6. landing gear control according to one of the preceding claims, characterized in that the actuating signal for the actuators (8, 9) is generated by evaluating the transverse acceleration measured in the vehicle and / or the measured roll angle.

7. landing gear control according to one of the preceding claims, characterized in that detected by measuring the spring deflection the outside of the bend side of the vehicle side and the inside of the curve side is tracked by suitable control of the actuators (8, 9) of the outside of the vehicle side.