Damper device for a motor vehicle

Abstract

The invention relates to a method for controlling a damper device (1) of a motor vehicle (2), wherein the damper device (1) comprises a control apparatus (3) and at least one damper (4) controllable b

Description

The invention relates to a method for controlling a damper device, a damper device for a motor vehicle, and a motor vehicle having such a damper device. Motor vehicles commonly comprise a damper device arranged between the vehicle body and wheels of the motor vehicle to damp relative movement between them. Such a damper device comprises a plurality of dampers, which connect the wheels to the vehicle assembly in a damping manner. These can be passive dampers or active dampers that are actively controllable, e.g. by means of a hydraulic pump. In the design of the controller of the dampers, a compromise is made in this respect between a high body connection, which connects the respective wheel comparatively rigidly to the vehicle body, and a good body isolation, which provides a soft connection between the respective wheel and the vehicle body, e.g. at a high excitation frequency. Also known are damper devices based on the skyhook method. The basic idea of the skyhook method is that the movement of the vehicle body is not controlled with respect to a vehicle underbody, but with respect to a fictitious, fixed sky. Accordingly, the dampers are controlled in a skyhook control or skyhook method to counteract the relative movement of the vehicle body with respect to this fictitious, fixed sky. Such a control does not necessarily counteract a relative movement between the wheel and the vehicle body, but rather reinforces it under certain circumstances. Multi-valve dampers are usually used for this purpose. Multi-valve dampers provide the advantage of enabling a quick response to a load change (between compression and rebound). On the other hand, single valve dampers must be switched for each load change (e.g., between a soft and a rigid state). However, such high-frequency switching has various drawbacks due to valve inertia. As a result, each damping valve of a multi-valve damper is preferably switched in only one direction (compression direction or rebound direction of the damper) respectively. This enables significantly better damping of high-frequency excitations. However, this rapid response can lead to a large build-up of force in the dampers (with a steep gradient) for excitations with a strong amplitude (usually low-frequency excitations) and thus cause a strong acceleration of the vehicle body. This reinforces the conflict described hereinabove resulting from a high body connection and good body insulation. On this basis, the present invention seeks to at least partially overcome the disadvantages known from the prior art. The features according to the invention arise from the independent claims, and advantageous embodiments thereof are disclosed in the dependent claims. The features in the claims can be combined in any technically suitable manner, whereby the explanations in the following description as well as features in which the drawings, which include explanatory embodiments of the invention, can also be used for this purpose. An aspect of the invention relates to a method for controlling a damper device of a motor vehicle, whereby the damper device comprises a control apparatus, at least one damper controllable by means of the control apparatus, and a body spring arranged between a vehicle body and a wheel, whereby the method comprises at least the following steps in the order specified: a. determining a potential energy in a body spring by means of a control apparatus; b. predicting a body movement of the vehicle body resulting from the potential energy by means of the control apparatus based on the determined potential energy in the body spring; c. determining a damping control value by means of the control apparatus based on the predicted resulting body movement of the vehicle body; d. damping the resulting body movement by means of the damper based on the determined damping control value. Ordinal numbers used in the description hereinabove and hereinafter are used only for clear differentiation and do not reflect any order or ranking of the designated components, unless explicitly indicated otherwise. An ordinal number greater than one does not necessitate that a further such component must necessarily be present. A method is proposed herein, by means of which a motor vehicle is damped. To this end, the motor vehicle comprises a damper device having a control apparatus, at least one damper controllable by means of the control apparatus, and a body spring. The damper device or the at least one damper and the body spring are arranged between a wheel and a vehicle body of the motor vehicle. In this way, excitations caused by, e.g., the vehicle underbody (e.g., a roadway or unevenness on the road) and / or other accelerations can be damped. In this respect, a distinction is, e.g., made between the damping of roll movements, pitch movements, and lifting movements. The skilled person is aware of this differentiation between roll movements, pitch movements and lift movements, so that further explanations are omitted herein. The damper comprises at least one controllable damping valve, e.g. a proportional valve, preferably a plurality of damping valves, particularly preferably two damping valves. For example, the damper is a telescopic damper. By means of the at least one damping valve, e.g., a pressure differential between two chambers of the telescopic damper separated by a piston can be compensated. Opening and / or closing of the at least one damping valve is in this case controlled by means of the control apparatus. The body spring is, e.g., a mechanical spring (e.g., a coil spring), a hydraulic spring, and / or a pneumatic spring. For example, the spring is integrated into the damper. The control apparatus is then used to determine a potential energy in the body spring in step a. of the method. If the damper and the body spring are, e.g., compressed because the wheel and the vehicle body move towards each other, then the potential energy in the body spring increases. The potential energy absorbed by the body spring is subsequently converted back into kinetic energy. At least one portion of this kinetic energy leads to an acceleration of the vehicle body, and another portion leads to, e.g., an acceleration of the wheel. With a high-frequency excitation of the wheel, e.g. due to a road with a low level of unevenness, a large portion of the potential energy returns to the wheel, which is, e.g., pushed downwards again after passing over a small protrusion. Larger or static excitations, on the other hand, can cause a significant portion or total kinetic energy to cause acceleration of the vehicle body. This happens when, e.g., cornering, during acceleration phases, braking phases, or driving over low-frequency excitations. In order to avoid unwanted strong accelerations of the vehicle body in such a case, the body movement resulting from the potential energy (i.e., the movement of the vehicle body) is predicted, i.e. estimated, in step b. For example, the body movement is estimated in the form of an acceleration value of the vehicle body. Based on the body movement of the vehicle body estimated in step b, a damping control value is determined in step c. by means of the control apparatus. Based on the damping control value, the damper is controlled and thus damps the resulting body movement of the vehicle body in step d. For example, a damping valve of the damper is opened or closed by means of the damping control value. For example, a skyhook control of the damper is in this case bypassed or suspended. In the example of cornering, the motor vehicle leans towards the outside of the curve due to the inertial forces. A skyhook control would apply high pressure to the external dampers in order to compensate, which can result in a sharp acceleration of the vehicle body. The proposed method, on the other hand, detects the potential energy in the body springs and therefore prevents overreaction of the damper device. The damper device preferably comprises a damper and a body spring for each wheel of the motor vehicle. Each of the dampers can in this case be controlled individually by means of the control apparatus. By means of the method proposed herein, overreactions of the damper device and thus unwanted strong accelerations of the vehicle body are can thus be prevented. It is further proposed in one advantageous embodiment of the method that the potential energy be determined by an integration of a spring force via a deflection of the body spring in step a. According to the embodiment proposed in this case, the potential energy in the body spring is then determined by means of an integration of the spring force via the deflection of the body spring. The deflection of the body spring is the distance at which the wheel and the vehicle body are moved towards each other, taking into account the transmission, i.e. the spring travel. The spring force of the body spring can, e.g., be determined using characteristic maps, in which the spring force is stored as a function of the known operational variables. It is further proposed in one advantageous embodiment of the method that when determining the damping control value in step c., an estimated conversion time and / or an estimated conversion duration is further considered, during which the potential energy is converted into the resulting body movement of the vehicle body. According to this embodiment, when determining the damping control value in step c., an estimated conversion time or an estimated conversion duration, during which the potential energy is converted into the resulting body movement of the vehicle body, is also further considered. The conversion time or the conversion duration can, e.g., be estimated based on the type of excitation, or a predictive detection of the preceding excitation reasons. For example, the length or duration of a cornering can be detected based on camera recordings, the excitation frequency can be determined based on the current vehicle underbody, or a remaining duration of a braking operation can be estimated. It can therefore be estimated whether, e.g., a classic skyhook control should be performed or whether the body movement resulting from the potential energy should be damped. It is further proposed in one advantageous embodiment of the method that, based on at least one of the following characteristics of the motor vehicle, it is estimated which portions of the potential energy are basically stationary: a longitudinal acceleration; a lateral acceleration; a track width; a wheel base; a centre of gravity; and an axle kinematics. According to this embodiment, a longitudinal acceleration, a lateral acceleration, a track width, a wheelbase, a centre of gravity and / or an axle kinematics of the motor vehicle are used to estimate which portions of the potential energy are basically stationary, i.e., remain constant over a longer period of time, e.g. more than one second. It is thus determined which portion of a measured roll angle and or pitch angle is caused by longer-acting reasons / causes, e.g., by cornering, acceleration of the motor vehicle, or braking of the motor vehicle. This is used to, e.g., determine the conversion duration described hereinabove or the conversion time. In this way, the basically stationary portions of the potential energy can be compensated for and unnecessary acceleration of the vehicle body can be prevented. It is further proposed in one advantageous embodiment of the method that the damper be controlled based on a skyhook method. According to this embodiment, the damper device is based on the skyhook method, unless it is bypassed in certain situations of the method described hereinabove to prevent too high acceleration or undesirable body movement of the vehicle body. As already described hereinabove, control of the damper according to a skyhook method is based on the fact that the movement of the vehicle body is not controlled in relation to a vehicle underbody, but in relation to a fictitious, fixed sky. Accordingly, the dampers are controlled in a skyhook control to counteract the relative movement of the vehicle body with respect to this fictitious, solid sky. Multi-valve dampers are usually used for this purpose. Preferably, in a multi-valve damper, each damping valve is switched in only one direction (traction direction or compression direction of the damper) respectively. This enables a significantly better damping of high-frequency excitations. The conflict between a high body connection linkage and a good body isolation described hereinabove is achieved by means of the method described hereinabove. It is further proposed, in one advantageous embodiment of the method, that the damper is a passive damper or an active damper, preferably driven by a hydraulic pump. According to this embodiment, the damper is an actively controlled damper. The damper is actively controlled by means of a hydraulic pump. To this end, the hydraulic pump is connected to the damper by means of a hydraulic circuit. For example, the hydraulic circuit includes damping valves that can be used to control the direction in which a force generated by the hydraulic pump acts. For example, the damper is a hydraulic telescopic damper and can be controlled by means of the control apparatus. The damping valves can, e.g., be used in this case to control which of the two chambers of the hydraulic telescopic damper is pressurised. Furthermore, the lines in which the damping valves are arranged can, e.g., be used as a bypass between the chambers of the telescopic damper. It is further proposed, in one advantageous embodiment of the method, that the damping of said body movement resulting from the potential energy occurs in step d. by opening or closing a damping valve of the damper. According to this embodiment, a damping valve is actuated, e.g. opened or closed, in order to control the damper. Preferably, as described hereinabove, a plurality of damping valves is provided, which can be controlled by means of the control apparatus (i.e., able to be opened or closed). The damping valve or damping valves are, e.g., arranged in a bypass line, e.g. a hydraulic circuit, or within the damper, e.g. in a piston of the damper. Proposed according to another aspect is a damper device for a motor vehicle, whereby the damper device is designed to perform a method according to an embodiment according to the description hereinabove, and comprises at least the following components: at least one body spring; at least one controlled damper; and a control apparatus designed to control the damper. According to this embodiment, a damper device for a motor vehicle is designed to perform the method described hereinabove. The damper device comprises a control apparatus and a damper that can be controlled by means of the control apparatus. The damper and the body spring are designed to be mounted between a wheel and a vehicle body of a motor vehicle and to damp unwanted movements, e.g., pitch movements, roll movements, or lift movements of the vehicle body. To this end, the damper device is, e.g., based on the skyhook method and damps the relative movement between the vehicle body and a fictitious, fixed sky. According to the method hereinabove, given a deflection of the damper or the body spring (due to a relative movement between the wheel and the vehicle body), the potential energy introduced by this relative movement into the body spring is determined in order to predict a body movement of the vehicle body based on this. This is performed by means of the control apparatus, which comprises a processor and a memory. The damper device proposed herein offers the advantage that undesirable accelerations of a vehicle body of a motor vehicle can be prevented or reduced. It is further proposed, in one advantageous embodiment of the damper device, that the damper features a damping valve, which can be controlled by means of the control apparatus for damping the resulting body movement of the vehicle body. According to this embodiment, the damper device comprises at least one damping valve, preferably a plurality of damping valves, particularly preferably two damping valves for each damper, which can be controlled by means of the control apparatus based on the estimated potential energy in the body spring. As explained hereinabove, a pressure that provides the potential energy can be released from the damper, e.g. via a bypass or an internal damping valve (e.g., arranged in the piston of a telescopic damper), or pressure compensation can be induced between two chambers of the damper. Proposed according to a further aspect is a motor vehicle comprising: a plurality of wheels, at least one of which is designed as a drive wheel; a drive motor for providing a drive torque, which is connected to the at least one drive wheel in a torque-transmitting manner; a vehicle body; and a damper device according to one embodiment according to the description hereinabove, which is arranged between the plurality of wheels and the vehicle body, to damp a body movement of the vehicle body. The motor vehicle proposed herein comprises a plurality of wheels, preferably four wheels, a drive motor, a vehicle body, and a damper device. The drive motor is designed to provide a drive torque. For example, the drive motor is an internal combustion engine or an electric drive motor. At least one of the plurality of wheels is designed as a drive wheel. The drive torque can, e.g., be transferred to the drive wheel by means of a transmission, by means of which a corresponding drive of the motor vehicle can be generated. The damper device is a damper device according to the description hereinabove. The damper device or the at least one damper and the at least one body spring of the damper device, are arranged between the wheels and the vehicle body. Preferably, a damper and a body spring of the damper device are arranged between each wheel and the vehicle body. The damper device is in this case designed and arranged to damp a body movement of the vehicle body. As already explained, such a body movement results from, e.g., an excitation of the wheel or a relative movement between the wheel and the vehicle body. The invention described hereinabove is, in light of the relevant technical background, explained in detail hereinafter with reference to the accompanying drawings, which illustrate preferred embodiments. The invention is not limited in any way by the purely schematic drawings, whereby it is noted that the drawings are not true to size and are not suitable for defining proportions. Shown are: Fig. 1: a damper device in a schematic diagram; Fig. 2: a schematic diagram of how the damper device in Fig. 1 works; Fig. 3: a curve diagram of a road excitation, a potential energy and a body movement according to the principle representation in Fig. 2; Fig. 4: a motor vehicle having a damper device; and Fig. 5: a flow chart of a method for controlling the damper device in Fig. 1. A preferred embodiment of a damper device 1 according to the invention is shown schematically in Fig. 1. A damper 4 is arranged between the wheels 6 of a motor vehicle 2 and its vehicle body 5, one of which is shown pars pro toto in this case. According to the illustration, the damper 4 is a telescopic damper, which can be controlled by means of a hydraulic pump 9. A body spring is integrated into the damper 4 (not shown separately in this case). The hydraulic pump 9 is connected to the damper 4 by means of a hydraulic circuit. Two chokes 17 and two damping valves 10 are arranged in the hydraulic circuit. Furthermore, in the illustrated exemplary embodiment, a compensation tank 16 for the hydraulic fluid is arranged in the hydraulic circuit. If there is a relative movement between the wheel 6 and the vehicle body 5, e.g. due to unevenness on the road 13, acceleration of the motor vehicle 2, braking of the motor vehicle 2, cornering or the like, the damper 4 and the body spring are deflected, i.e., compressed or extended, as shown in the illustration. According to the illustration, a lower fluid chamber of the damper 4 is compressed when the wheel 6 and the vehicle body 5 move toward each other, e.g., when the wheel 6 is on the outside when cornering, or the wheel 6 rolls up a protrusion on a road 13. Accordingly, the pressure in the lower fluid chamber, or the differential pressure for the upper fluid chamber, increases accordingly. At the same time, the spring is compressed, so the potential energy stored in the spring increases, pushing the piston upwards for pressure compensation, thereby also pushing the vehicle body 5 upwards. This resulting body movement 8 can lead to undesirably strong accelerations of the vehicle body 5. To avoid this, a bypass is opened, e.g. by opening the damping valves 10, through which the hydraulic fluid flows into the upper fluid chamber. Pressure compensation thus takes place, and the body movement 8 or the acceleration of the vehicle body 5 is damped. The control apparatus 3 comprises a processor 18 and a memory 19. For example, the processor 18 comprises one or multiple processor units. One such processor unit is, e.g., a general purpose processor (CPU) or microprocessor, RISC processor, GPU, and / or DSP. In one embodiment, the processor 18 is configured solely for the task specified herein. In a preferred embodiment, the processor 18 is configured for a plurality of tasks that are capable of being processed by the processor 18 in real-time and / or basically in parallel. The memory 19 is, e.g., a hard drive (HDD, solid-state drive, HDD) or a (non-volatile) solid state memory, e.g. a ROM memory or flash memory (Flash EEPROM). The memory 19 often comprises a plurality of individual physical storage units or is distributed across a plurality of individual devices, so that it can be accessed via data communication, e.g. a package data service. The latter is a decentralised solution utilising data memory and processor 18 (units) of a plurality of separate processors 18 instead of a (single unitary) central processor 18 or in addition to a central processor 18. In one embodiment, the memory 19 is arranged in the motor vehicle 2. In one embodiment, the memory 19 is replaced or supplemented by an external storage apparatus. In one embodiment, the memory 19 is configured solely for the task specified herein. In a preferred embodiment, the memory 19 is configured for a plurality of storage tasks, in which case, e.g., a portion of the physically integral and / or unitary data memory is solely responsible for a virtual partition, and / or the data are registered contiguously on the software side, but physically stored in a more or less randomly distributed manner. Fig. 2 shows a schematic diagram of the operating principle of the damper device 1. The device is in this case, e.g., a damper device 1 according to Fig. 1. The damper 4 and the body spring 14 are shown parallel to each other and connect a wheel 6 to a vehicle body 5 of a motor vehicle 2. The wheel 6 rolls on a surface, in this case and by way of example a road 13. The road 13 according to the illustration has a step over which the wheel 6 rolls (see first and second illustrations). The damper 4 and the body spring 14 are compressed and thereby receive a potential energy 7 (see third illustration). The potential energy 7 corresponds, e.g., to the energy 7 of a tensioned spring. Accordingly, the potential energy 7 can be determined by an integration of the spring force via the spring range, i.e., the deflection of the body spring 14. Due to the stored potential energy 7 or the spring force, the vehicle body 5 is accelerated upwards in a body movement 8 (see fourth illustration). As a countermeasure, e.g. by means of the damper 4, this acceleration of the vehicle body 5 or the body movement 8 can be damped. For this purpose, the damper 4 is softened, e.g. by opening a damping valve 10. Fig. 3 shows the excitation of the wheel 6 over a step in the road 13 shown in the schematic diagram. The path of the wheel 6 is shown as road excitation 12. The potential energy 7 thus introduced into the body spring 14 is shown in a further second curve. The result thereby is the corresponding body movement 8 according to the third curve. By damping the effect of the damper 4 or the body spring 14, the potential energy 7 is not reduced in a strong overreaction, but oscillates slowly away. Shown in Fig. 4 is a motor vehicle 2 having a damper device 1, e.g. as shown in Fig. 1. According to the illustration, the motor vehicle 2 comprises four wheels 6, each of which is designed as a drive wheel. According to the illustration, the wheels 6 can be driven by means of an electric drive motor 11 per axle. To this end, the electric drive motor 11 (shown at the rear according to the illustration) is connected to the wheels 6 of the rear axle by means of a transmission 21 in a torque-transmitting manner. Furthermore, a differential transmission 20 is shown on the rear axle for distributing the drive torque to the two wheels 6. Fig. 5 shows a flow chart of the method for controlling a damper device 1, e.g. a damper device 1 as shown in Fig. 1. In step a. the potential energy 7 in the body spring 14 is determined using the control apparatus 3. For example, the spring force of the body spring 14 is for integrated via the spring travel for this purpose. To this end, the damper device 1 comprises, e.g., distance measurement sensors, as well as force measurement sensors or pressure sensors. In a subsequent step b. a body movement 8 of the vehicle body 5 is predicted, i.e. estimated, by means of the control apparatus 3. The estimated body movement 8 results from the potential energy 7 in the body spring 14 and is estimated based on the potential energy 7 determined in step a. Based on the resulting body movement 8 for the vehicle body 5 estimated in step b., a damping control value for the damper 4 or the damping valves 10 of the damper 4 is determined in step c. by means of the control apparatus 3. By means of the damping control value, the damper 4 or the damping valve 10 is controlled. In step d. the resulting body movement 8 of the vehicle body 5 is therefore damped by means of the damper 4 based on the determined damping control valve. The invention relates to a method for controlling a damper device, which estimates the body movement of a vehicle body based on a potential energy in a body spring. In this way, e.g., undesirably strong accelerations of the vehicle body can be prevented.

Claims

1. A method for controlling a damper device of a motor vehicle, wherein the damper device comprises a control apparatus, at least one damper controllable by means of the control apparatus, and a body spring arranged between a vehicle body and a wheel, wherein the method comprises at least the following steps in the order specified:a. determining a potential energy in the body spring by means of a control apparatusb. predicting a body movement of the vehicle body resulting from the potential energy by means of the control apparatus based on the determined potential energy in the body spring;c. determining a damping control value by means of the control apparatus based on the predicted resulting body movement of the vehicle body;d. damping the resulting body movement by means of the damper based on the determined damping control value.

2. The method according to claim 1, wherein,in step a., the potential energy is determined by an integration of a spring force of the body spring via a deflection of the body spring.

3. The method according to claim 1 or claim 2, wherein,when determining the damping control value in step c., an estimated conversion time and / or an estimated conversion duration is further considered, during which the potential energy is converted into the resulting body movement of the vehicle body.

4. The method according to any one of the preceding claims, wherein, based on at least one of the following characteristics of the motor vehicle, it is estimated which portions of the potential energy are basically stationary:-a longitudinal acceleration;- a lateral acceleration;- a track width;- a wheel base;- a centre of gravity; and-an axle kinematics.

5. The method according to any one of the preceding claims, wherein the damper is controlled based on a skyhook method.

6. The method according to one of the preceding claims, wherein the damper is a passive damper or an active damper, preferably driven by a hydraulic pump.

7. The method according to any one of the preceding claims, wherein the damping of the body movement resulting from the potential energy occurs in step d. by means of the opening and / or closing of a damping valve of the damper, the damping of the body movement resulting from the potential energy being performed in step d. by opening or closing a damping valve of the damper.

8. A damper device for a motor vehicle, wherein the damper device is designed to perform a method according to one of the preceding claims, and comprises at least the following components:- at least one body spring;-at least one controlled damper; and-a control apparatus designed to control the damper.

9. The damper device according to claim 8, whereinthe damper comprises a damping valve, which is controllable by means of the control apparatus for damping the resulting body movement of the vehicle body.

10. A motor vehicle, comprising- a plurality of wheels, at least one of which is designed as a drive wheel;-a drive motor for providing a drive torque which is connected to the at least one drive wheel in a torque-transmitting manner;-a vehicle body; and- a damper device according to claim 8, which is arranged between the plurality of wheels and the vehicle body in order to damp a body movement of the vehicle body.