DE102004024951A1 - Double-tracked four wheeled motor vehicle body`s vertical movement determining method, e.g. for controlling chassis control system, involves detecting speed and acceleration of body based on signals of acceleration and height sensors - Google Patents

Abstract

Vertical movement determining method involves evaluating signals from vertical acceleration sensors (BS) assigned to both front wheels of a motor vehicle and from body height sensors (HS) assigned to three wheels. A distance between a wheel-fixing point and a vehicle body-fixing point and speed and acceleration of the body are determined based on the signals. The signals from the two sensors are passed via differentiation and integration filters, respectively. An independent claim is also included for a double-tracked four wheeled motor vehicle with a spring-damper-system.

Description

The invention relates to a method for determining the vertical movement of the construction of a two-lane biaxial vehicle, in particular for the electronic control of a vertical dynamics influencing chassis control system, in particular an electronically controllable stabilizer system or electronically controlled spring-damper systems that between the structure and The individual vehicle wheels associated wheel guides are provided, under evaluation of the signals from at least the two front wheels associated Vertikalbescheunigungs sensors and at least three individual wheels associated with level sensors, with which the distance can be determined in each case between a wheel-fixed point and a built-up point. Furthermore, the invention relates to a suitably equipped motor vehicle. The technical environment is next to the DE 102 20 575 A1 on the DE 39 30 517 A1 and further to the EP 1 197 409 A2 directed.

The just second-mentioned document describes a device for road-dependent suspension control of a motor vehicle, with the dynamic driving condition detecting Sensors whose data are fed to an evaluation circuit, the one for the road surface unevenness generates characteristic signal that with a spring arrangement of the vehicle controls cooperating actuators. Specifically, these may be active or semi-active dampers, the rest closer in this writing are defined. To determine the road surface unevenness is doing at each vehicle wheel by means of a force sensor the respective damper force, Furthermore, by means of a so-called level sensor in the present application the distance between the wheel and the body section located in the wheel area of the vehicle, and further by means of a vertical acceleration sensor determines the respective vertical wheel acceleration.

In the above first DE 102 20 575 A1 There is also an indication of electronically controllable shock absorbers of a vehicle chassis with variable damper characteristics, ie so-called semiactive dampers. It is also stated that these are usually controlled taking into account the signals of a so-called vertical acceleration pickup. Such a vertical acceleration sensor detects the acceleration of the vehicle body in the vertical direction and is also mentioned in the other DE 39 30 517 A1 mentioned.

Sensors or sensors for determining the vertical acceleration of the vehicle body cause additional costs that can be avoided if a corresponding signal can also be determined differently, namely from sensor signals of existing sensors. It is indeed in the mentioned DE 102 20 575 A1 already mentioned that no independent vertical acceleration sensor for measuring a body acceleration in the vertical direction is required when an acceleration of the vehicle body in the direction of the road from the signals of at least one level sensor, by means of which the distance between the Fzg. Structure and a Fzg . Wheel or an associated chassis part can be measured is determined. However, this is proposed in this prior art for detecting a banked turn on a vehicle moved into such a curve, but not to determine the vertical movement of the vehicle body.

Also in the prior art according to the already mentioned EP 1 197 409 a vehicle dynamics control system is operated solely by evaluating the signals of so-called. Level sensors, but in addition the force in the spring-damper systems of the individual wheels is determined, and that on the basis of the force-displacement characteristics of the affected components, ie the respective Springs or dampers. Also in the prior art after the already mentioned DE 39 30 517 A1 , which deals with the determination of Radlastschwankungen produced a characteristic of the road bump signal and this considered in the control of semi-active dampers, the size of the body acceleration is not needed because there the respective damper force is measured and taken into account.

Herewith So now is a method for determining the movement in the vertical direction the construction of a two-lane two-axle vehicle in particular for the electronic control of a vertical dynamics influencing Suspension control system are shown, without a vertical acceleration sensor for the Construction and without damper force sensors or without determination of the respective damper force (cf the described known prior art) can work and instead on a simple other sensors accesses (= object of the present invention).

to solution this object, the features of claim 1 are proposed, advantageous developments are content of the dependent claims. One corresponding motor vehicle is specified in independent claim 5.

to Determination of the vertical movement of the vehicle body and to the resulting derived electronic control of a chassis control system, For example, spring-damper systems and in particular semi-active dampers, on a two-lane Two-axle vehicle is thus the combination of Radbeschleunigungssensorik and level sensors proposed. The latter is always at several wheels already present if the vehicle with air suspension or generally one Height adjustment system, i.e. the distance of the vehicle body from the ground, is provided. At least on each axis once is such a level sensor already existing due to legal regulations, when the motor vehicle is equipped with xenon headlamps.

The individual wheels associated vertical acceleration sensors can advantageously in one on the respective adjustable spring-damper system, in particular in a provided on a semi-active damper control unit, the u.a. contains the respective power electronics, be integrated, which the construction costs and the wiring costs are kept low. Such a controller controls the respective damper or the respective system individually and must only one Data bus and an electrical power supply with a central electronic control unit and be connected to the electrical system of the vehicle. Other connection and signal lines between the adjustable Spring-damper system and the Fzg. structure are thus advantageously not required In particular, no connection to a (no longer needed and therefore i.d.R. not available) construction acceleration sensor needed and advantageously then can also connect to the respective level sensor be kept simple and short, as this is usually very close to Spring-damper system is appropriate.

Basically the determination of the vertical acceleration of each vehicle by means of a own vertical acceleration sensor can be determined individually alternatively, it is also possible the vertical accelerations of the left and right rear wheels from the vertical acceleration of the left and right front Rades under consideration Derive the vehicle speed, as assumed can be that a bump or the like, which is a front wheel in Vertical direction accelerates after moving the vehicle around the longitudinal distance between the front wheels and the rear wheels too will act on the respective rear wheel in the same way.

Especially is advantageous in the proposed method for determining a Vehicle body movement in vertical direction by means of a vertical Radbeschleunigungssensorik and a level sensors that the Wheel movement and the body movement each viewed in the vertical direction are relatively strongly separated with respect to their frequency range. hereby there is a good chance by using filters or observer approaches and reduced sensor technology both vertical wheel movement and vertical Close construction movement. Because of the higher Radeigenfrequenz and the associated higher difficulty of a Radbewegungsschätzung is Thus, from a functional point of view, the use of a wheel acceleration sensor proposed instead of a build-up acceleration sensor. there can determine the bodywork movement from the altitude and vertical accelerations single wheels preferably be carried out in the following different ways.

Thus, the body speed (and the differentiation of the body acceleration) can be obtained by filter technology of the corresponding structure, the signals of the level sensors via a differentiation and the signals of the wheel acceleration sensors are passed through an integration filter and then added. For further explanation please refer to the attached 1 referenced, which shows a Viertelfahr convincing model (which simulates a semi-axis of the vehicle) and in which by means of a level sensor HS, which outputs a signal (z _A - z _R ) and a wheel associated with the vertical acceleration sensor BS, the signal z .. _R on the body movement in vertical direction, concretely, first the vertical body speed ż _A can be closed.

there In the present text and in the appended figures, first the The following labels are used: The letter z denotes the coordinate or distance in the vertical direction, designated ż the first time differentiation and thus vertical speed and z .. denotes the second temporal differentiation and thus vertical acceleration. "A" is called an index the vehicle structure and "R" referred to as index a vehicle wheel. With the letter "m" is the mass, with "c" a spring constant and with "k" a damper constant designated.

In 1 So it's a vehicle wheel 1 shown, which forms an unsprung mass m _R and thereby has spring properties (c _R ) and damping properties (k _R ). About a spring 2a with the spring constant c _A and a damper 2 B with the damper constant k _A , which together form a spring-damper system 2 make up is on the bike 1 the figuratively not shown vehicle body, which forms the sprung mass m _A , supported. The damper 2 B is preferably a semi-active damper with a due to electronic control variable damping constant k _A.

The vehicle, not shown, moves on an uneven road surface 3 , which forces in the off the lane 3 Rolling vehicle wheel 1 be initiated, leading to a vertical movement not only the wheel 1 , but also the Fzg. structure in the vertical direction z lead, where it is necessary to determine the build-up movement, there on the basis of this size of semi-active damper 2 B to be controlled in a suitable manner. As already mentioned, this is done with the help of a level sensor HS, which continuously measures the current distance between a built-up point and a wheel-fixed point and therefore outputs a signal (z _A - z _R ), and with the help of a wheel 1 associated vertical acceleration sensor BS, which outputs a signal z .. _R , on the body movement in the vertical direction, specifically, first the vertical body speed ż _A closed, and first to that of the structure in the attachment point of the respective spring-damper system 2 ,

For this purpose, the vertical acceleration z .. _{R of} the wheel 1 integrated (with the help of an integration filter 22 ) to close to the wheel speed ż _R , and the ride height (z _A - z _R ) is differentiated (using a differentiation filter) 21 ) to the relative speed (ż _A - ż _R ) between the vehicle body and the wheel 1 to obtain. By adding these two speeds, the body speed ż _{A can be} obtained. The integration filter can do this 22 or the differentiation filter 21 be used in addition to the differentiation or integration to suppress the noise and offset errors of the sensor. By a further differentiation or integration of the body speed ż _A , the body acceleration z .. _A or - if necessary - in principle, the body path z _A can be determined.

alternative can the vertical construction movement by means of a control engineering so-called observers such as Kalman filter or Luenberger observer determined become. For the design of such an observer, there are in the literature different approaches, For example, reference is made to the book by Otto Föllinger, "Control Engineering, Introduction to the methods and their application ", directed. In principle, it will be parallel to the actual controlled system (which in the present case is formed by the vehicle) Model built up or calculated. This model gets the same Input signals such as the controlled system. At the controlled system certain sizes (here Wheel acceleration and ride height) and compared or subtracted from the corresponding model outputs. The resulting error is returned to the observer model via a feedback matrix attributed to what with a suitable choice leads to the decay of the error. For a suitable design the feedback matrix Again, there are different approaches, the corresponding in a Luenberger observer or a Kalman filter, where it is otherwise around a linear or even a suitable nonlinear observer (eg an "extended Kalman filter ") can act.

Observer methods thus differ only in the determination of the feedback matrix, however, the structural design is the same. advantageously, The corresponding control structure can be a disturbance observer be extended, which in addition still the road condition estimated can be. Furthermore The closed observer design offers the advantage of having filters eliminates offsets and suppresses sensor noise can.

After the steps described so far, the vertical movement of the vehicle body is known at the attachment points of the respective spring-damper systems on the vehicle body. Chassis control systems that affect the vertical dynamics, but regulate the individual modal states of motion of the vehicle body, namely Huben (as pure vertical movement), roll (as tilting movement about the vehicle longitudinal axis) and pitch (as tilting movement about the vehicle transverse axis). Therefore, from the vertical movements of the vehicle body at the individual attachment points of the spring-damper systems, the individual so-called. Modal movements ż _A (= Huben), ø. _A (= wavering) and θ. _A (= pitch) of the structure can be determined. This can be done by means of the following matrix equation, with regard to the distance dimensions a ₁ , a ₂ used in the matrix in the longitudinal direction from the centers of the individual wheels 11 (front right), 12 (Left in the front), 13 (back left), 14 (Rear right) to a transverse to the vehicle center of gravity axis, and b ₁ , b ₂ as a half distance between the two-sided wheel centers, to the attached 2 is referenced. In the following matrix equation, the vertical build-up speed at the four Be fixing points of the wheel-individual spring-damper systems front left (left), front right (v, r), rear left (h, l) and rear right (h, r) with the letter v and provided with an index indicating the respective attachment point.

This is an overdetermined system of equations, so that the knowledge of the vertical movement for determining the modal quantities is not needed at all for one of the four attachment points, so that the corresponding sensor system can be omitted with respect to this wheel. On the other hand - also for redundancy reasons - quite in the range of all four wheels of the vehicle, a corresponding sensor system may be present, as in the attached 3 is shown schematically. In this case, "BS1" denotes the vertical acceleration sensor assigned to the right front wheel, and "HS1" denotes the corresponding level sensor, while "HS2" designates the level sensor assigned to the left front wheel and "BS2" denotes the corresponding vertical acceleration sensor. These sensors are also provided on the two rear wheels (BS3, BS4 or HS3, HS4).

In this 3 not registered are the individual wheels 11 . 12 . 13 . 14 associated spring-damper systems that are preferably electronically controlled their semi-active damper and thus in their characteristics are changeable. In order to be able to control these suitably, a knowledge of the current build-up movement in the vertical direction is required, which can be obtained simply and accurately in the manner described. It is in 3 a central electronic control unit is present, which is connected via a data bus with all these sensors and also controls the spring-damper systems, and marked with "ECU." Deviating from this, (not shown figuratively) spring-damper systems of the individual wheels 11 . 12 . 13 . 14 a separate control unit for the respective example. Semi-active damper be provided, wherein it should be noted that quite a variety of other details may be deviated from the above explanations, without departing from the content of the claims.

Claims (5)

Method for determining the vertical movement of the structure of a two-lane two-axle vehicle, in particular for the electronic control of a vertical dynamics influencing chassis control system, in particular an electronically controllable stabilizer system or electronically controllable spring-damper systems ( 2 ) between the bodywork and the individual vehicle wheels ( 1 . 11 , ..., 14 Assigned wheel guides are provided, under evaluation of the signals from at least the two front wheels associated vertical acceleration sensors (BS) and at least three individual wheels associated with level sensors (HS), with which the distance between a wheel fixed point and a built-up point can be determined wherein the build speed and / or the buildup acceleration is determined without using a vertical acceleration sensor for the design and without determining the respective damper force. A method according to claim 1, characterized in that the signals of the level sensors (HS) via a differentiation filter ( 21 ) and the signals of the wheel acceleration sensors (BS) via an integration filter ( 22 ) and then added to obtain the build speed (¿ _A ). Method according to claim 1, characterized in that that the construction movement by means of a linear control or nonlinear observer (Luenberger observer or Kalman filter), if necessary under additional Using a disturbance observer, is determined. Method according to one of the preceding claims, characterized in that the vertical accelerations of the rear wheels ( 13 . 14 ) from the vertical accelerations of the respective front wheels ( 12 . 11 ) are derived taking into account the vehicle driving speed or determined by means of their own wheel associated vertical acceleration sensors (BS). Two-lane biaxial motor vehicle with the individual wheels associated electronically controlled adjustable spring-damper systems between the vehicle body and the individual vehicle wheels associated wheel guides, wherein at least provided for adjustment power electronics directly on each spring-damper system ( 2 ) is provided and at least at the two front wheels ( 1 . 11 . 12 ) the vertical acceleration sensors are installed in the local power electronics, and wherein the body speed (ż _A ) and / or the body acceleration (z .. _A ) without using a build-acceleration sensor from the signals of the vertical acceleration sensors (BS ) of the wheels ( 1 . 11 . 12 , possibly also 13 . 14 ) and level sensors (HS), which are in the range of at least three wheels ( 1 ) are provided and are used to determine the distance between a wheel-fixed point and a built-up point, is determined.