Method for operating a wheel suspension system

Abstract

In a method for operating a wheel suspension system of a motor vehicle, a sensor checks the ground for the presence of an obstacle, as identified by a control device, and predicts for the obstacle a first value for an amount of electrical energy, which is to be converted from mechanical energy by an electrical machine, when a damping ratio is set with a defined recuperation value for a damper connecting a wheel to a chassis. The control device predicts a second value for a ride comfort and determines a third value for a decision criterion, which is a function of the first and second values. The identified obstacle is to be driven over with the recuperation value set for the damping ratio of the damper, when the value for the decision criterion corresponds to a target value.

Claims

1. A method for operating a wheel suspension system of a motor vehicle, comprising: ascertaining by a sensor a ground to be traveled in the future by the motor vehicle; checking the ground for the presence of an obstacle; identifying an unevenness as the presence of the obstacle, when a value of at least one measurement of the unevenness deviates by a tolerance value from a threshold value; predicting for the identified obstacle a first value for an amount of electrical energy which is converted from mechanical energy by an electrical machine of the motor vehicle operated as a generator, when a damping ratio is set with a defined recuperation value for a damper via which a wheel is connected to a chassis of the motor vehicle, as the motor vehicle drives over the identified obstacle; predicting a second value for a ride comfort by setting the damping ratio with the recuperation value for the damper, as the motor vehicle drives over the identified obstacle; determining a third value for a decision criterion as a function of the first value and of the second value; and driving over the identified obstacle with the recuperation value set for the damping ratio of the damper, when the third value corresponds to a target value.

2. The method of claim 1, further comprising adjusting the damper at set recuperation value for the damping ratio harder than when traveling a level ground in which a comfort value is set for the damping ratio.

3. The method of claim 2, further comprising reducing the damping ratio from the recuperation value to the comfort value after driving over the obstacle.

4. The method of claim 1, further comprising: predicting a mechanical power of the damper from a square of a speed of the damper multiplied by the recuperation value for the damping ratio; and determining the first value through integration of the mechanical power over the time during which the obstacle is to be traveled.

5. The method of claim 1, further comprising: ascertaining by the sensor a region of the ground to be traveled in the future; and defining a reference plane having a level which corresponds to a mean value of point heights along the region.

6. The method of claim 5, wherein a deviation of the unevenness from the level of the reference plane is determined as the at least one measurement of the unevenness.

7. The method of claim 5, wherein a change of a deviation of the unevenness from the level of the reference plane in a direction that is parallel to the reference plane is determined as the at least one measurement of the unevenness.

8. The method of claim 5, wherein a length of the unevenness in a direction that is parallel to the reference plane is determined as the at least one measurement of the unevenness.

9. The method of claim 5, wherein a frequency of a periodically repeating shape of the unevenness in a direction that is parallel to the reference plane is determined as the at least one measurement of the unevenness.

10. The method of claim 1, further comprising using at least one simulation model for the wheel suspension system for predicting the first value of the amount of convertible electrical energy, when traveling the ground.

11. A system for operating a wheel suspension system of a motor vehicle, comprising: a control device configured to check a ground to be traveled in the future by the motor vehicle for the presence of an unevenness of the ground and to identify the unevenness as an obstacle, when a value of at least one measurement of the unevenness deviates by a tolerance value from a threshold value; and a sensor, said control device configured to predict a value for a ride comfort for the identified obstacle, which is established when the damping ratio is set with the recuperation value for the damper when traveling the identified obstacle, to determine a value for a decision criterion, which is a function of the value for the amount of electrical energy converted from mechanical energy and of the value for ride comfort with the recuperation value set for the damping ratio of the damper, and to cause the identified obstacle to be driven over with the recuperation value set for the damping ratio of the damper, when the value for the decision criterion corresponds to a target value.

12. The system of claim 11, wherein the sensor is arranged on an outer wall of the motor vehicle and has a detection region which is oriented in a travel direction of the motor vehicle.

13. The system of claim 11, wherein the sensor is configured to ascertain an environment of the motor vehicle based on waves that are to be emitted by the sensor, to be reflected from at least one object in the environment of the motor vehicle, and to be received again by the sensor.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) Embodiments of the invention are schematically illustrated in the drawing and described schematically and in detail with reference to the drawing.

(2) FIG. 1 shows a schematic illustration of a motor vehicle which is equipped with an embodiment of the system according to the invention and which travels a ground, wherein an embodiment of the method according to the invention is carried out.

(3) FIG. 2 shows a schematic illustration of a detail of the embodiment of the system from FIG. 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(4) The motor vehicle 2 shown in FIG. 1 includes four wheels 4, 6, of which, however, only a first wheel 4, configured as a front wheel, and a second wheel 6, configured as a rear wheel, are shown. Each wheel 4, 6 is connected via one wheel suspension system 8, 10 to a chassis 12 of the motor vehicle 2.

(5) A detail of the wheel suspension system 8 of the first wheel 4 is shown in FIG. 2. Provision is hereby made for all wheel suspension systems 8, 10 of all the wheels 4, 6 to have the same components. Thus, each wheel suspension system 8 includes, as a first component, a damper 14 and a spring 16. As an additional component of the respective wheel suspension system 8, an electrical machine 18 is associated with the damper 14 as an actuator. The electrical machine 18 can be used either as a motor, wherein electrical energy is to be converted into mechanical energy, or as a generator, wherein mechanical energy is to be converted into electrical energy and thus recuperated.

(6) When the electrical machine 18 is operated as a motor or motor-driven, the damper 14 associated with the electrical machine 18 is to be mechanically acted upon by the electrical machine 18 and thus to be excited. Conversely, when the electrical machine 18 is operated as a generator, it is mechanically acted upon by a movement of the associated damper 14, so that mechanical energy, which is generated by the damper 14 during its movement, is converted by the electrical machine 18 into electric energy in a generator-driven operation.

(7) in this context, a damping ratio of the damper 14 is also to be varied, with the damper 14 being adjusted increasingly harder, as the damping ratio increases. When the damping ratio is greater than a threshold value to be defined beforehand and thus has a recuperation value and the electrical machine 18 operated as a generator is acted upon by the thus set hard damper 14, mechanical energy of the damper 14 is converted into electric energy by the electrical machine 18.

(8) The introduced embodiment of the system 22 includes a control device 24 with which at least one step of an embodiment of a method according to the invention is to be controlled and thus controlled via an open loop control and/or closed loop control, and at least one sensor 26 for ascertaining and thus for recognizing and/or locating an environment of the motor vehicle 2, with this sensor 26 being arranged here on an outer wall of the motor vehicle 2. In this case, the environment is detected without contact by the sensor 26 on the basis of electromagnetic or acoustic waves which are emitted by the sensor 26, reflected by objects in the environment and are received by the sensor 26. Such a sensor can be designed as a camera for electromagnetic waves in the visible region, but also as a radar or lidar sensor. A sensor 26, which detects the environment on the basis of acoustic waves is generally designed as an ultrasonic sensor.

(9) All wheel suspension systems 8, 10 of all wheels 4, 6 and thus all dampers 14, springs 16 and electrical machines 18 are each, depending to the definition, configured as components of the embodiment of the system 22 according to the invention introduced here.

(10) All the introduced components of the embodiment of the system 22 can also be used for carrying out other functions of the motor vehicle 2, independent of the intended embodiment of the method.

(11) Furthermore, it is provided here that the motor vehicle 2, in a situation illustrated with reference to FIG. 1, travels a ground 28 with a height profile which has several unevennesses. Three of these unevennesses are also defined or designated as obstacles 32, 34, 36 based on their respective measurements and/or size. In the situation described here, the motor vehicle 2 approaches the unevennesses, classified here as obstacles 32, 34, 36, along the height profile of the ground 28.

(12) When carrying out the embodiment of the method, the environment and thus, i.a., the ground 28 is ascertained within a detection range 38 of the sensor 26, wherein the detection region 38 is oriented forwardly in an anticipatory manner in travel direction of the motor vehicle 2.

(13) Moreover, the height profile of the ground 28 is analyzed by the control device 24, wherein unevennesses are also recognized and/or identified and, in the present situation, categorized or classified as obstacles 32, 34, 36 which are relevant in the embodiment of the method. For this purpose, the height profile of the ground 28 is measured, with local changes of a contour of points on a surface of the ground 28 being determined to provide the height profile. In the introduced embodiment, a reference plane 40 which is arranged parallel to the chassis 12 of the motor vehicle 2, for example, is hereby defined for at least one region of the ground 28, and, alternatively or additionally, can correspond with reference to its height to a mean value of point heights along the at least one region.

(14) A possible unevenness of the height profile of the ground 28 is recognized and/or classified as an obstacle 32, 34, 36, when the contour of the height profile of the ground 28 in a direction changes, e.g., in a desired travel direction of the motor vehicle 2, relative to the reference plane 40 at a location of the ground by a value which is at least as great as a threshold value to be defined for this purpose. In this case, the contour of the height profile with respect to a straight line can be defined as an abscissa, which is oriented according to the direction provided and runs through the reference plane 40, as a curve which is to be plotted along an ordinate which is perpendicular to the straight line or abscissa, wherein a first derivative of this curve corresponds to a change in the course. A value of the derivative and thus the value of the change is compared to the threshold value to be defined for this purpose. In the present embodiment, a first and a second obstacle 32, 34 are classified as elevations and a third obstacle 36 as a depression.

(15) Furthermore, with the control device 24, it is to be determined for each obstacle 32, 34, 36 how much energy can be recovered by the electrical machine 18 associated with the respective damper 4 at a certain recuperation value for the damping ratio which is set for the damper 14 during an operation of the electrical machine 18 as a generator. In this case, a value of an amount of energy which may be recovered is dependent on the measurement of the respective obstacle 32, 34, 36 as well as on the damping ratio to be set, when a wheel 4 drives over and/or passes the obstacle 32, 34, 36. Moreover, a value for a ride comfort of the motor vehicle is to be determined, which value is established, when the obstacle 32, 34, 36 is driven over by the wheel 4 with increased recuperation value set for the damping ratio, wherein the value for the ride comfort also depends on the measurement of the obstacle 32, 34, 36 as well as the recuperation value for the damping ratio. A decision can be made based on a value of a decision criterion to be calculated as to whether the obstacle 32, 34, 36 can be driven over with the increased damping ratio and thus electric energy recovered by the electrical machine 18, wherein the value of the decision criterion depends, on one hand, on the value of the ride comfort and, on the other hand, on the value of the electrical energy which can be recovered, when the obstacle 32, 34, 36 is driven over. Normally, the lower the ride comfort, the higher the damping ratio and/or the amount of electrical energy to be recovered, Conversely, the higher the ride comfort, the lower the damping ratio and/or the amount of electrical energy to be recovered.

(16) Depending on the definition of the decision criterion, an obstacle 32, 34, 36 can be driven over with an increased value and thus the recuperation value for the damping ratio of the damper 14, when the value of the decision criterion corresponds to a target value to be defined for this purpose. In this case, the target value for the decision criterion can be set individually by a person driving the motor vehicle 2. By providing the decision criterion with consideration of the individually adjustable target value for this purpose, there is thus a balance between the ride comfort on one hand and the amount of electrical energy to be recovered on the other hand.