DE102019213273B4 - System for roll stabilization of a motor vehicle - Google Patents

Abstract

System for the roll stabilization of a motor vehicle, having an adjustable roll stabilizer (1) with an actuator (2) which is drive-connected to two stabilizer sections (6a, 6b) and which can be operated to rotate them in relation to one another about an axis of rotation (3), the stabilizer sections (6a, 6b) radially away from the axis of rotation (3) are each coupled to a wheel suspension (7a, 7b, 8a, 8b, 9a, 9b), so that the rolling behavior of the motor vehicle can be influenced by controlling the actuator (2). by a protective device that can be operated, based on the evaluation of recorded level signals (z7a, z7b) of the wheels (7a, 7b), to detect an impending critical operating state of the actuator (2), the critical operating state being an operation of the actuator (2) operates at excessively high speed.

Description

The invention relates to a system for the roll stabilization of a motor vehicle according to the features of claim 1 and a method for protecting an actuator of an adjustable roll stabilizer according to claim 11.

It is known from motor vehicle technology, in particular chassis technology, to influence the roll or roll behavior of motor vehicles by means of so-called roll stabilizers. The basic structure is an essentially C-shaped torsion bar, which is mounted in the central area so that it can rotate relative to the vehicle body and whose outer, opposite ends are each coupled to a wheel suspension by means of coupling elements, so-called pendulum supports. With this construction, the roll stabilizer ensures that the body of the vehicle not only deflects on the outside of the curve when cornering (caused by the centrifugal force), but also that the wheel on the inside of the curve is lowered slightly. Roll stabilizers improve the vehicle's directional stability and reduce the lateral inclination of the vehicle body (roll), making cornering safer and more comfortable.

In order to further increase vehicle stability and driving comfort, it is known to make roll stabilizers of this type adjustable. In this case, the roll stabilizer includes an actuator and is divided into two stabilizer sections that can be rotated relative to one another about a rotational axis with the aid of the actuator. By twisting the stabilizer sections relative to each other, a rolling movement of the vehicle body is generated in a targeted manner or a rolling movement of the vehicle body caused by external influences is counteracted in a targeted manner. Adjustable roll stabilizers are known from the prior art, the actuator of which has an electric motor which is drive-connected to a mechanical gear, in particular in the form of a multi-stage planetary gear, in order to achieve suitable speeds or torques. In this context, an example is DE 10 2016 219 399 A1 referred.

In a system for roll stabilization of a motor vehicle, having an adjustable roll stabilizer with an actuator which is drive-connected to two stabilizer sections and which can be operated to rotate them about an axis of rotation in relation to one another, the stabilizer sections being coupled radially away from the axis of rotation with a wheel suspension in each case, so that a rolling behavior of the motor vehicle can be influenced by controlling the actuator, critical operating states for the actuator can occur under certain operating conditions. In particular, when a motor vehicle equipped with an adjustable roll stabilizer drives over what is known as a "rough road", i.e. a stretch of road with numerous bumps in the road, the adjustable roll stabilizer can be stimulated to move externally, which in the worst case scenario stimulates the adjustable roll stabilizer, for example in the range of its natural frequency . In this case, the height movements of the wheels, which are coupled to the adjustable roll stabilizer and which are caused when driving on an uneven road surface, have a retroactive effect on the actuator due to the mechanical drive connection. Because of the mechanical speed transmission that takes place within the actuator through the multi-stage planetary gear that is usually present, it can happen in these situations that the electric motor in the actuator is accelerated to a very high speed, or that an excessively high speed is imposed on it.

Such an operating situation is disadvantageous in various respects. First of all, very high engine speeds, in particular impermissibly high engine speeds, can lead to a system failure if, for example, a motor position can no longer be clearly detected due to the high speed. This may be due to the engine position sensor exceeding a sampling rate. In addition, mechanical damage to the electric motor can occur if the speed is too high. In any case, as the engine speed increases - due to the speed or torque characteristics of an electric motor - a braking torque that can be generated with the electric motor decreases, so that at an already high engine speed it is no longer possible to generate sufficient braking torque, which in turn leads to a further increase in the speed can no longer be prevented.

the end DE 10 2013 205 370 A1 a system for roll stabilization of a motor vehicle according to the features of the preamble of patent claim 1 is known.

It is an object of the present invention to specify a system for roll stabilization of a motor vehicle of the type described above, with which a critical operating state of the actuator, in particular operation at an excessively high speed, can be detected at least early on. In addition, a method for protecting an actuator of an adjustable roll stabilizer is to be specified.

The object described above is initially achieved by a system for roll stabilization of a motor vehicle according to claim 1. This has an adjustable roll stabilizer with an actuator which is drive-connected to two stabilizer sections and which can be operated to rotate them in relation to one another about an axis of rotation, the stabilizer sections radially removed from the axis of rotation are each coupled to a wheel suspension, so that a rolling behavior of the motor vehicle can be influenced by controlling the actuator. According to the further features of the invention, the system for roll stabilization is characterized by a protective device that can be operated to detect an impending critical operating state of the actuator based on the evaluation of detected height signals of the wheels, the critical operating state being an operation of the actuator with excessively high speed.

According to the invention, it was therefore first recognized that when operating an adjustable roll stabilizer on a motor vehicle in certain operating situations, in particular when driving on rough roads, external excitations of the adjustable roll stabilizer can occur, which react on the actuator of the adjustable roll stabilizer - and thus also on the Drive train mechanically coupled electric motor of the actuator. It was also recognized that there is a need to identify such operating situations as early as possible, ideally before the critical operating state occurs. According to the invention, an idea that is relatively easy to implement in terms of design was developed for this purpose, namely to conclude on an impending critical operating state of the actuator on the basis of an evaluation of the detected level signals of the wheels.

The ride height signals of the wheels can be generated in a relatively simple manner via appropriate ride height sensors, which are regularly already present in known systems for roll stabilization or generally in the chassis of motor vehicles. Within the scope of the invention, a possibility was recognized of using the recorded level signals of the wheels to recognize a situation early on that has the potential to trigger a critically high engine speed on the electric motor of the actuator. In this context, early detection using suitable criteria, in particular based on an evaluation of the ride height signals of the wheels, means detection before the critical operating state is reached. The premature nature of the detection (“announcing a critical operating state”) creates a basis or advantageously makes it possible to initiate a preventive measure which ideally can aim to even avoid the occurrence of the critical operating state.

According to the invention, the protective device uses the ride height signals from the wheels and evaluates them. It has been shown that an impending critical operating state of the actuator can already be recognized from the height levels of both wheels coupled to an adjustable roll stabilizer. The wheel heights are thus used for early detection. The task mentioned at the outset is thus achieved.

In principle, various operating situations of an adjustable roll stabilizer can be regarded as critical. In the context of the present invention, the critical operating state is operation of the actuator at an excessively high speed. The drive train of the actuator usually contains an electric motor, which is coupled to an output shaft of the actuator via a multi-stage planetary gear. Accordingly, an excessively high speed of the actuator corresponds to an impermissibly high speed occurring at the electric motor. Since an impermissibly high speed for an electric motor harbors the risk of mechanical damage and/or due to a high speed, a clear motor position detection may no longer be possible (because a sampling frequency of an associated motor position sensor is exceeded) and/or with increasing speed If a braking torque that can be generated with the electric motor also decreases, an impermissibly high speed can be regarded as a critical operating state of the actuator.

A critical operating state, in particular an excessively high speed of the actuator, can have various causes. In the context of the invention, a critical operating state is based in particular on an external movement excitation of the adjustable roll stabilizer during operation of the motor vehicle, in particular due to vertical movements of the wheels caused by the roadway. This is because such a movement excitation is transmitted to the actuator or the electric motor located in the drive train of the actuator due to the mechanical coupling.

According to the invention, it is provided that the protective device recognizes the impending critical operating state of the actuator at an early stage on the basis of an evaluation of the detected level signals of the wheels. Advantageously, the protective device can be operated as part of the evaluation of the level signals of the wheels, to calculate a wheel hub difference speed and with a predefinable threshold value of the wheel hub difference compare speed. In other words, the protective device runs an algorithm which calculates the wheel stroke differential speed based on the detected level signals of the wheels (of the axle equipped with the adjustable roll stabilizer) and compares it with a threshold value. In this context, wheel lift differential speed is the speed at which a difference in the height of one wheel compared to the height of the other wheel (especially the left wheel compared to the right wheel) changes over time. Accordingly, the difference in height of the wheels over time is derived and compared to the threshold value mentioned.

A critical operating state is expediently present when the differential wheel stroke speed exceeds a predefinable threshold value of the differential wheel stroke speed. This is based on the finding that a wheel lift differential speed that is above a threshold value has the potential to trigger a high speed at the actuator or a high speed multiplied by the corresponding transmission ratio at the electric motor of the actuator. A consideration of the wheel hub differential speed or its comparison with a threshold value offers the possibility of recognizing an imminent increase in rotational speed with relatively simple means, ie in particular of predicting it.

Advantageously, a critical operating state is detected based on suitable criteria already mentioned before the critical operating state is reached, which makes it possible to initiate a preventive measure. Various measures are conceivable in this context, e.g. the output of a warning (optical and/or acoustic).

According to a preferred development of the system for roll stabilization, the protective device can be operated to cause the actuator to be braked when the critical operating state is detected. In other words, in this case the protective device causes the critical operating state of the actuator to be counteracted. Ideally, the measure can even prevent the critical operating state from occurring at all.

According to an advantageous embodiment of the system for roll stabilization, the protective device will reduce a maximum engine speed of a position speed controller in order to cause the actuator to be braked. In this way, the electric motor of the actuator can generate a braking torque at an early stage, which counteracts the externally generated acceleration of the motor.

According to a further advantageous embodiment of the system, the protective device can also be operated, but then refrain from braking the actuator if the present wheel stroke differential speed contributes to reducing a difference between the desired position and the actual position of the actuator. The protective device thus advantageously makes a case distinction, according to which braking for overspeed protection is then omitted if the existing movement of the stabilizer sections relative to one another reduces an existing control deviation. In this case, braking the actuator would be counterproductive with regard to position control.

The object mentioned at the outset is also achieved by a method for protecting an actuator of an adjustable roll stabilizer with the features of claim 11. The method can be used in a system for roll stabilization of a motor vehicle as described above. According to the invention, an imminent critical operating state of the actuator is recognized on the basis of the evaluation of recorded level signals of the wheels, the critical operating state being operation of the actuator at an excessively high speed. To avoid repetition, reference is made to the previous explanations regarding the system for roll stabilization, which can also be applied correspondingly to the method for protecting an actuator.

• 1 einen verstellbaren Wankstabilisator für ein Kraftfahrzeug in schematischer Ansicht,
• 2 eine graphische Darstellung einer Regelstrategie eines verstellbaren Wankstabilisators.

The invention is explained in more detail below with reference to a drawing. This also results in further advantageous refinements of the invention. In the drawing shows:

• 1 an adjustable roll stabilizer for a motor vehicle in a schematic view,
• 2 a graphical representation of a control strategy of an adjustable roll stabilizer.

To illustrate the field of application of the invention shows 1 first an adjustable roll stabilizer 1 in a schematic view. The adjustable roll stabilizer 1 is part of a chassis, not shown in full, of a motor vehicle (not shown). Only a vehicle body 10 of the motor vehicle is indicated by reference symbols. The roll stabilizer 1 is also part of an axle of the motor vehicle, for example the front axle and/or rear axle of the motor vehicle can be equipped with the adjustable roll stabilizer 1 .

how 1 shows, a left wheel 7a and a right wheel 7b, which is arranged on the opposite side of the vehicle, are each connected to the vehicle body 10 via a link arrangement 8a or 8b, which is not to be explained in any more detail. Wheel 7a and link arrangement 8a or wheel 7b and link arrangement 8b thus each form a unit and are each coupled to one end of an associated stabilizer section 7a or 7b of the adjustable roll stabilizer 1 via a pendulum support 9a or 9b. The left-hand stabilizer section 6a and the right-hand stabilizer section 6b are connected to one another in the center of the vehicle via an actuator 2, which is shown as a substantially cylindrical body.

In a manner known per se, the adjustable roll stabilizer 1 is mounted such that it can rotate about an axis of rotation 3 with respect to the vehicle body 10; 1 enclose a region of the respective stabilizer section 6a or 6b facing the actuator 2--shown in simplified form--in a U-shape.

The actuator 2 shown here as a cylindrical body essentially comprises a housing (not specified) that is essentially rotationally symmetrical with respect to the axis of rotation 3, in which an electric motor 4 and a multi-stage planetary gear 9 and a speed sensor 13 (each only indicated by reference numbers) are arranged are. The stabilizer sections 6a and 6b are drive-connected to one another via the electric motor 4 and the multi-stage planetary gear 5 . When the actuator 2 is stationary, the two stabilizer sections 6a, 6b are rigidly connected to one another via the stationary electric motor 4 and the multi-stage planetary gear 5 drive-connected thereto. However, due to the operation of the electric motor 4, the stabilizer sections 6a, 6b can be rotated relative to one another about the axis of rotation 3, depending on the direction of rotation of the electric motor 4. The multi-stage planetary gear 5 specifies a fixed speed ratio between the drive (electric motor 4) and the output (right-hand stabilizer section 6b coupled to the gear output). The adjustable roll stabilizer 1 can thus be adjusted in a way that is known per se.

Depending on the operating state of the adjustable roll stabilizer 1 or the vehicle equipped with it, torsion of the stabilizer sections 6a, 6b coupled to one another via the actuator 2 can occur, depending on which a moment Msystem acting about the axis of rotation 3 develops. This moment Msystem is present at the actuator 2 in the form of a system moment.

With the help of the roll stabilizer 1, a roll moment M _Wank can be supported, which acts between the vehicle body 10 and the wheels 7a, 7b. The roll moment M _Wank that can be supported can be influenced by adjusting the roll stabilizer 1 . For needs-based control of the roll stabilizer 1, the left wheel 7a and the right wheel 7b are each assigned a ride height sensor 12a or 12b, which enable wheel lifting movements of the respective wheel to be detected and in the form of a ride height for the left wheel z7a or ride height for the output right wheel z7b. In addition, the rotation of the electric motor 4 can be detected via the rotation speed sensor 13 and is output in the form of a rotation speed signal as the motor rotation speed n.

The regulation of the 1 The adjustable roll stabilizer 1 shown schematically is based on the 2 illustrated control strategy explained in more detail below. Accordingly, a so-called system setpoint torque is included as an input variable in the regulation of the adjustable roll stabilizer 1 . This is a variable specified by the vehicle, which corresponds to the moment _Msystem acting around the axis of rotation 3 (cf. 1 ) corresponds, which is to be supported by the adjustable roll stabilizer 1 at the level of the actuator, which means that the actuator 2 - comprising electric motor 4 and gear 5 - with a direction of rotation about the axis of rotation 3 attacks. Via the kinematic interaction of the adjustable roll stabilizer 1, the wheel suspensions 7a, 7b, 8a, 8b, 9a, 9b and the connections 11a, 11b to the vehicle body 10, the adjustable roll stabilizer 1 thus supports - at vehicle level - an axis-related roll moment M _Wank (see Fig. 1 , running around the longitudinal direction of the vehicle).

The system target torque is converted via a known system stiffness into a torsion angle for the torque requirement, with the known system stiffness being composed of individual stiffnesses, in particular the stiffness of the stabilizer itself (stabilizer sections, gears, housing, if necessary decoupling elements, pendulum support, stabilizer bearing and the like).

At the same time, a variable for compensating for disturbances is included in the regulation of the adjustable roll stabilizer. For this purpose, wheel movement data, recorded by level sensors assigned to the wheels, in the form of level signals (wheel-specific) as well as a characteristic value table for a decoupling angle (with previously determined vehicle-specific data) are used to determine a so-called "zero moment angle", i.e. the angle that corresponds to the outer torsion angle of the adjustable roll stabilizer, ver caused, for example, by an uneven road, and which would make the actuator of the adjustable roll stabilizer torque-free. The two angles determined in this way, namely the angle of rotation for the torque requirement and the zero torque angle, are then added to form a setpoint angle.

The setpoint angle is then fed to a cascaded position/speed controller. This includes a position controller, which determines a setpoint speed from the incoming setpoint angle - also taking into account a feedback signal from the motor - which in turn is used in a speed controller. On the basis of the setpoint speed and feedback from the electric motor (speed), the speed controller determines a motor setpoint torque for controlling the electric motor. The desired engine torque is in turn supplied to a field-oriented control system, which controls the electric motor 4 of the actuator 2--again taking into account feedback signals from the electric motor. An engine output torque generated by the electric motor 4 is converted - now mechanically - via a gear 5 (multi-stage planetary gear) to a system torque that is transmitted between the stabilizer sections (cf. 1 Reference numerals 6a and 6b) acts.

This in 2 The control scheme shown is advantageously used on a system as shown in 1 illustrated adjustable roll stabilizer 1. In the control principle described there, an incoming system setpoint torque is converted via the system stiffness into a setpoint angle, from which a motor setpoint torque is determined by means of a position speed controller, with the motor being subjected to corresponding motor currents .

In operation of the basis of 1 described adjustable roll stabilizer on a motor vehicle, in particular using the basis of 2 explained control schemes, it can happen when driving on so-called “bad roads” that the adjustable roll stabilizer 1 is excited in the range of its natural frequency due to bumps in the road and the resulting compression or rebound of the wheels 7a, 7b. Such an excitation of the adjustable roll stabilizer 1 from the outside, due to the mechanical coupling of the stabilizer sections 6a, 6b to the actuator 2, or via the transmission 5 to the engine 4, leads to an acceleration of the engine 4 to high, possibly too high, speeds.

In the case of overspeed, the electric motor 4 not only loses a drive torque that can be applied (not necessary in this situation), but also a braking torque that is desirable in this situation. In addition, when very high speeds are exceeded, for example more than approximately 25,000 revolutions/minute, the position signal of the electric motor 4 is lost because a sampling frequency for detecting the motor position is exceeded. As a result, the setting position of the motor 4 is no longer known. In addition, mechanical damage to the motor 4 can occur.

Within the scope of the invention, a system for roll stabilization of a motor vehicle is therefore characterized by a protective device that can be operated by evaluating detected level signals of z7a, z7b of wheels 7a, 7b to detect an impending critical operating state of the actuator at an early stage. This is in particular an operating state in which the actuator 2 or an electric motor 4 located in its drive train is operated at an excessively high speed. For this purpose, the protective device can be operated to evaluate the ride height signals z7a, z7b of the wheels 7a, 7b. To do this, the protective device uses an algorithm to calculate a wheel lift differential speed, i. H. the derivation of the difference between the ride height signals z7a, z7b and compares them with a predetermined threshold value. A critical operating state is present in particular when the wheel stroke differential speed exceeds the specified threshold value.

In order to avoid the above-described disadvantages of a critical operating state in the form of an overspeed of the actuator, the protective device automatically initiates a counteracting measure. According to a preferred exemplary embodiment of the invention, such a measure consists in causing the actuator to be braked when an impending critical operating state of the actuator is detected. This is done, for example, by the protective device setting a maximum motor speed of the position speed controller (cf. 2 ) reduced. As a result of the reduction, a sufficiently high braking torque can be generated in the motor of the actuator at an early stage—ideally before the critical operating state occurs—which counteracts the externally excited acceleration.

Braking of the actuator, as described above, in the event of overspeed detected at an early stage is only omitted if the present wheel stroke differential speed contributes to reducing a difference between the desired position and the actual position of the actuator 2 .

With the system described, critical operating states of the actuator can be detected early in a relatively simple manner, specifically using existing means be carried out and a critical operating state can be counteracted.

Reference List

1

adjustable roll stabilizer

2

actuator

3

axis of rotation

4

electric motor

5

multi-stage planetary gear

6a, 6b

left (or right) stabilizer bar section

7a, 7b

left (or right) wheel

8a, 8b

left (or right) handlebar arrangement

9a, 9b

left (or right) pendulum support

10

vehicle body

11a, 11b

left (or right) stabilizer bearing

12a, 12b

Level sensor left (or right) wheel

13

speed sensor

20

kinematics

z7a, z7b

Height of left (or right) wheel

MWake

rolling moment (axle related)

MSystem

system moment

n

engine speed

a

system angle

β

stabilizer angle

Claims (11)

System for the roll stabilization of a motor vehicle, having an adjustable roll stabilizer (1) with an actuator (2) which is drive-connected to two stabilizer sections (6a, 6b) and which can be operated to rotate them in relation to one another about an axis of rotation (3), the stabilizer sections (6a, 6b) radially away from the axis of rotation (3) are each coupled to a wheel suspension (7a, 7b, 8a, 8b, 9a, 9b), so that the rolling behavior of the motor vehicle can be influenced by controlling the actuator (2) . by a protective device that can be operated, based on the evaluation of recorded level signals (z7a, z7b) of the wheels (7a, 7b), to detect an impending critical operating state of the actuator (2), the critical operating state being an operation of the actuator (2) operates at excessively high speed. system for roll stabilization claim 1 , characterized in that there is an electric motor (4) in the drive train of the actuator (2). system for roll stabilization claim 1 or 2 , characterized in that an excessively high speed is an impermissibly high speed occurring at the electric motor (4). System for roll stabilization according to one of the preceding claims, characterized in that the critical operating state is based on an external movement excitation of the adjustable roll stabilizer (1) during operation of the motor vehicle, in particular due to vertical movements of the wheels (7a, 7b) caused by the roadway, which due to the mechanical coupling to the actuator (2), in particular its electric motor (4). System for roll stabilization according to one of the preceding claims, characterized in that the protective device can be operated as part of the evaluation of the level signals (z7a, z7b) of the wheels (7a, 7b) to calculate a wheel hub differential speed and to compare it with a predefinable threshold value of the wheel hub differential speed. system for roll stabilization claim 5 , characterized in that a critical operating state is present when the wheel hub differential speed exceeds the predefinable threshold value of the wheel hub differential speed. System for roll stabilization according to one of the preceding claims, characterized in that the detection using suitable criteria already takes place before the critical operating state is reached in order to enable the introduction of a preventive measure. System for roll stabilization according to one of the preceding claims, characterized in that the protective device can be operated to cause the actuator (2) to be braked when the critical operating state is detected. System for roll stabilization according to one of the preceding claims, characterized in that in order to cause the actuator (2) to be braked, the protective device reduces a maximum motor speed of a position speed controller. System for roll stabilization according to one of the preceding claims, characterized in that the protective device can be operated to refrain from braking the actuator (2) if the present wheel stroke differential speed is required to reduce a difference between the desired position and the actual position of the actuator (2). contributes. Method for protecting an actuator (2) of an adjustable roll stabilizer (1), applicable to a system for roll stabilization of a motor vehicle according to one of the preceding claims, wherein based on the evaluation of detected level signals (z7a, z7b) of the wheels (7a, 7b) an announced critical operating state of the actuator (2) is detected, the critical operating state being operation of the actuator (2) at an excessively high speed.

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