Method for controlling a spring-damper system for a motor vehicle and spring-damper system

Abstract

The invention relates to a method for controlling a spring-damper system (10) for a motor vehicle and a corresponding spring-damper system (10). The spring-damper system (10) comprises a control module (11), a damper element (12) with an adjustable damping coefficient, a spring element (13) with an adjustable spring stiffness, and a wheel (14) with a tire (15). The tire (15) has an RFID tag containing tire data. The RFID tag of the tire (15) is read, and the tire data is transmitted to the control module (11). The tire pressure of the tire (15) is detected, and the value is transmitted to the control module (11). The damping coefficient of the wheel (14) is determined.Based on the determined damping coefficient of the wheel (14), a target damping coefficient for the adjustable damping element (12) and a target spring stiffness for the adjustable spring element (13) are determined, and the damping coefficient of the damping element (12) and the spring stiffness of the spring element (13) are changed accordingly.

Description

[0001] The present invention relates to a method for controlling a spring-damper system according to the preamble of claim 1 and a corresponding spring-damper system.

[0002] Modern motor vehicles are equipped with adjustable spring and damper systems, allowing the driver to choose between different modes, such as a sport mode or an eco mode, with different settings of the spring and damper system to achieve different dynamic behavior of the spring and damper system and thus correspondingly different driving characteristics of the motor vehicle.

[0003] The various modes, with their respective settings for spring stiffness and damping coefficient of the adjustable spring-damper system, are pre-configured and preset within the system. Accordingly, the spring stiffness and damping coefficient for the selectable modes are no longer adjusted during vehicle operation.

[0004] Over time, however, changes occur in the spring-damper system and the corresponding vehicle that cannot be taken into account when adjusting the spring stiffness and damping coefficient settings for the respective modes. For example, tires are subject to fluctuations in tire pressure. Furthermore, tires age and are replaced at longer intervals. This leads to changes in the spring-damper system over its service life, so that the intended characteristics of the spring-damper system may no longer be fully achieved in the individual modes.

[0005] A suspension device with a damping device for a vehicle according to JP H08 - 324 220 A is known from the prior art, the pneumatic line of which includes an air pressure sensing device and a control device for controlling the spring constant of the spring mechanism.

[0006] Furthermore, DE 10 2016 209 929 A1 discloses a method for operating a control device for the chassis of a motor vehicle, in which the control device receives a class signal for each vibration damper of the chassis. The class signal indicates the respective tire class of the tire held by the respective vibration damper. The control device is further configured to set at least one configuration value for the actuation signal of the respective vibration damper depending on the class signal of the respective tire.

[0007] It is therefore known from the state of the art to automatically detect the tire class of a vehicle using an RFID signal transmitter in the tire and to regulate the vibration dampers depending on this.

[0008] Furthermore, a method for controlling a spring-damper system for a vehicle is known, which includes a control module, a damper element with an adjustable damping coefficient, a spring element with an adjustable spring stiffness, and a wheel with a tire. The method comprises the steps - Detecting tire pressure and transmitting the value to the control module, - Determination of a target damping coefficient for the adjustable damping element and a target spring stiffness based on the tire pressure, - Generating control signals from the target damping coefficient and the target spring stiffness, - Transmission of the control signals from the control module to the damper element and the spring element and - Change in the damping coefficient of the damping element and the spring stiffness of the spring element.

[0009] The object of the present invention is to provide a method for controlling a spring-damper system and a spring-damper system for a motor vehicle that enables adaptation to changes in tire condition for a consistent behavior of the spring-damper system when the tire condition changes.

[0010] The problem of the invention is solved by the independent claims.

[0011] To solve the problem of the invention, a method for controlling a spring-damper system for a motor vehicle is proposed, wherein the spring-damper system comprises a control module, a damper element with an adjustable damping coefficient, a spring element with an adjustable spring stiffness, and a wheel with a tire. The tire has an RFID tag containing tire data. The following steps are proposed: Step (a): Reading the tire's RFID tag and transmitting the tire data to the control module; Step (b): Detecting the tire pressure and transmitting the value to the control module; Step (c): Determining the damping coefficient of the wheel; Step (d): Determination of a target damping coefficient for the adjustable damping element and a target spring stiffness for the adjustable spring element based on the determined damping coefficient of the wheel; Step (e): Generating control signals from the target damping coefficient and the target spring stiffness; Step (f): Transmission of the control signals from the control module to the damper element and the spring element; Step (g): Change of the damping coefficient of the damping element and the spring stiffness of the spring element according to the control signals.

[0012] The proposed method allows for adaptation to changes in tire properties, thus compensating for these changes and maintaining the desired characteristics of the spring-damper system and, consequently, the vertical dynamics of the vehicle. This adaptation can be triggered automatically or manually. Furthermore, it is advantageous to perform this procedure at regular intervals.

[0013] For example, the suspension can be adjusted to be either firmer or softer depending on whether the tire pressure is too low or too high. Furthermore, adjustments can be made automatically to account for tire aging or a change in tire type.

[0014] Preferably, the tire data transmitted to the control module includes one or more of the following information: - Tire's aspect ratio (height-to-width ratio); - Tire dimensions; - vertical stiffness of the tire; - Production date of the tire; - Run-flat capability of the tire.

[0015] The relevant tire data preferably makes it possible to determine the actual damping coefficient and the actual stiffness of the wheel as accurately as possible.

[0016] According to an advantageous embodiment, it is proposed that in step (c) the determination of the damping coefficient of the wheel from the transmitted tire pressure and at least part of the transmitted tire data is carried out using a mathematical model.

[0017] Using the mathematical model, the various parameters and their relationships, such as tire pressure and tire dimensions, can be stored in the mathematical model, so that no direct measurement of the damping coefficient or spring stiffness of the wheel is required to adapt the spring-damper system to the changed properties of a tire during the operation of a vehicle.

[0018] In a preferred embodiment, in step (d) the target damping coefficient is determined using the groundhook principle based on the determined damping coefficient of the wheel.

[0019] The groundhook principle can be used to determine the target damping coefficient of the damping element. This principle allows for the simple calculation of the damping coefficient. Thanks to the simplified calculation method, the calculation can be performed without any time loss using a processor architecture with comparatively lower computing power and therefore lower energy consumption.

[0020] Furthermore, it is proposed that in step (d) the target spring stiffness is determined using the quarter-vehicle model based on the target damping coefficient of the damping element and specific damping coefficients of the wheel. The quarter-vehicle model enables a simple investigation of the vehicle's vertical dynamics and, consequently, also of driving safety and ride comfort. The quarter-vehicle model can be described by a generally known equation of motion.

[0021] According to an advantageous embodiment, it is proposed that the control module determines the damping coefficient of the wheel in step (c) and the target damping coefficient for the damping element as well as the target spring stiffness of the spring element in step (d).

[0022] This allows the vehicle to operate autonomously and to adapt to changing wheel characteristics.

[0023] Preferably, steps (a) and (b) are executed at time intervals, and steps (c) to (g) are preferably executed at time intervals and / or upon changes in the tire detected in step (a) and the tire pressure detected in step (b) that fall outside a tolerance. This allows for efficient operation of the method, with relevant changes triggering the execution of the method so that the desired dynamics of the spring-damper system can be maintained.

[0024] According to an alternative embodiment, it is proposed that after step (a) and step (b) and before step (c), the control module transmits the detected tire pressure and at least part of the data from the read RFID tag of the tire to a stationary server; the stationary server determines the damping coefficient of the wheel in step (c) and the target damping coefficient for the damping element as well as the target spring stiffness of the spring element in step (d); and between step (d) and step (e), the stationary server transmits the target damping coefficient and the target spring stiffness and / or control signals generated by the stationary server to the control module.

[0025] The stationary server is a server that operates outside of a vehicle. This provides the external server with significantly more computing power to calculate the required target damping coefficient and spring stiffness. Furthermore, the corresponding control signals for the damper and spring elements can also be calculated directly on the stationary server. This considerably reduces the required computing power in the control module and in the vehicle itself. Additionally, further development and adjustments for new tire models and types can be easily carried out centrally on the stationary server.

[0026] Furthermore, to solve the problem of the invention, a spring-damper system for a motor vehicle is proposed, wherein the spring-damper system comprises a control module, a damper element with an adjustable damping coefficient, a spring element with an adjustable spring stiffness, and a wheel with a tire, wherein the tire pressure is detectable by a pressure sensor and the detected value is transmittable to the control module. The tire has an RFID tag with tire data, which can be read by a reader and transmitted to the control module. The spring-damper system is configured to carry out the method of the type described above or according to any one of claims 1 to 8.

[0027] The advantages and effects of the proposed spring-damper system are the same as those of the previously described method.

[0028] According to a further development, it is proposed that the control module has a radio module that is equipped to transmit the detected tire pressure and at least part of the data from the read RFID tag to a stationary server and to receive a target damping coefficient and a target spring stiffness and / or control signals.

[0029] The radio module can transmit the relevant data, for example via a mobile network, to a stationary server and receive target damping coefficients or target spring stiffnesses specified by the server.

[0030] The invention is explained below with reference to preferred embodiments and the accompanying figures. Fig. 1. A spring-damper system for a motor vehicle in a schematic representation; Fig. 2. A scheme of the procedural steps for controlling a spring-damper system of a motor vehicle; and Fig. 3 Another spring-damper system for a motor vehicle in a schematic representation.

[0031] Fig. Figure 1 shows a schematic representation of a spring-damper system 10 for a motor vehicle. The spring-damper system 10 comprises a damper element 12 and a spring element 13, which have an adjustable damping coefficient preset according to the selected operating mode, as well as an adjustable spring stiffness preset analogously to the damping coefficient. A wheel 14 with a tire 15 is mounted on the spring element 13 and the damper element 12. The tire pressure of the tire 15 can be measured at intervals by a pressure sensor 18, which transmits the measured tire pressure to a control module 11 according to step (b) of the procedure. The tire 15 also has an RFID tag on which the tire data of the tire 15 is stored. The tire data is read by a reader 20 according to step (a) and also transmitted to the control module 11.Steps (a) and (b) can be performed at different times in any order or in parallel until the tire pressure and tire data are available in control module 11.

[0032] The further procedure is described using a schematically represented process flow in Fig. 2 explained. The tire data and the tire pressure of tire 15 are available on the control module 11 in step (c).

[0033] In this advantageous embodiment, the damping coefficient of the wheel 14 is determined by a mathematical model, with the corresponding input, calculation, and output of step (c) taking place in the control module 11. Based on the damping coefficient of the wheel 14, a target damping coefficient for the adjustable damping element 12 is then determined in step (d) via a calculation according to the groundhook principle, and a target spring stiffness for the adjustable spring element 13 is determined according to the quarter-vehicle model in the control module 11.

[0034] To adapt the spring-damper system 10 to the specified target values, in step (e) control signals are generated in the control module 11 from the target damping coefficient and the target spring stiffness, which are then transmitted in step (f) from the control module 11 to the adjustable damper element 12 and the adjustable spring element 13.

[0035] In the final step (g) the damping coefficient of the damping element 12 and the spring stiffness of the spring element 13 are changed according to the control signals, so that the originally intended dynamic characteristic of the spring-damper system 10 can be restored by adapting to the changed properties of the tire 15.

[0036] In Fig. Figure 3 schematically illustrates a further embodiment of a spring-damper system 10. In contrast to the previous embodiment, the control module 11 has a radio module 17. The control module 11 transmits the data and values ​​acquired in steps (a) and (b) via the radio module 17 to a stationary server 16, which is not located in the vehicle of the spring-damper system 10.

[0037] The previously described steps (c) and (d) are executed on the stationary server 16 and subsequently the target values ​​for the spring-damper system 10, i.e. the target damping coefficient and the target spring stiffness, are sent back to the control module 11.

[0038] In step (e), the corresponding control signals for the damper element 12 and the spring element 13 are generated in the control module 11 and transmitted in step (f). As in the first embodiment, the damping coefficient of the damper element 12 and the spring stiffness of the spring element 13 are changed in the final step (g) according to the control signals, thereby restoring the desired behavior of the spring-damper system 10, taking into account the changed properties of the tire 15.

Claims

[1] Method for controlling a spring-damper system (10) for a motor vehicle, wherein the spring-damper system (10) comprises a control module (11), a damper element (12) with an adjustable damping coefficient, a spring element (13) with an adjustable spring stiffness and a wheel (14) with a tire (15), wherein the tire (15) has an RFID tag with tire data, characterized by the steps: Step (a): Reading the RFID tag of the tire (15) and transmitting the tire data to the control module (11); Step (b): Detecting the tire pressure of the tire (15) and transmitting the value to the control module (11); Step (c): Determination of the damping coefficient of the wheel (14); Step (d): Determination of a target damping coefficient for the adjustable damping element (12) and a target spring stiffness for the adjustable spring element (13) based on the determined damping coefficient of the wheel (14); Step (e): Generating control signals from the target damping coefficient and the target spring stiffness; Step (f): Transmission of the control signals from the control module (11) to the damper element (12) and the spring element (13); Step (g): Change of the damping coefficient of the damping element (12) and the spring stiffness of the spring element (13) according to the control signals. [2] Method according to claim 1, characterized by , that the tire data transmitted to the control module (11) includes one or more of the following information: - Tire height-to-width ratio (15); - Tire dimensions (15); - vertical stiffness of the tire (15); - Production date of the tire (15); - Run-flat capability of the tire (15). [3] Method according to claim 1 or 2, characterized by, that in step (c) the determination of the damping coefficient of the wheel (14) from the transmitted tire pressure and at least a part of the transmitted tire data is carried out using a mathematical model. [4] Method according to any of the preceding claims, characterized by , that in step (d) the determination of the target damping coefficient is carried out using the groundhook principle on the basis of the determined damping coefficient of the wheel (14). [5] Method according to any of the preceding claims, characterized by , that in step (d) the target spring stiffness is determined using the quarter vehicle model based on the target damping coefficient of the damping element (12) and certain damping coefficients of the wheel (14). [6] Method according to any of the preceding claims, characterized by, that steps (a) and (b) are performed at time intervals, and that steps (c) to (g) are performed at time intervals and / or when changes occur in step (a) of the tire (15) detected and in step (b) of the tire pressure of the tire (15) outside of a tolerance. [7] Method according to any of the preceding claims, characterized by , that the control module (11) determines the damping coefficient of the wheel (14) in step (c) and the target damping coefficient for the damping element (12) as well as the target spring stiffness of the spring element (13) in step (d). [8] Method according to any one of claims 1 to 6, characterized by , that after step (a) and step (b) and before step (c) the control module (11) transmits the detected tire pressure and at least part of the data of the read RFID tag of the tire (15) to a stationary server (16); - the stationary server (16) determines the damping coefficient of the wheel (14) in step (c) and the target damping coefficient for the damping element (12) as well as the target spring stiffness of the spring element (13) in step (d); - between step (d) and step (e) the stationary server (16) transmits the target damping coefficient and the target spring stiffness and / or control signals generated by the stationary server (16) to the control module (11). [9] Spring-damper system (10) for a motor vehicle, wherein the spring-damper system (10) comprises a control module (11), a damping element (12) with an adjustable damping coefficient, a spring element (13) with an adjustable spring stiffness, and a wheel (14) with a tire (15), wherein the tire pressure of the tire (15) is detectable by a pressure sensor (18) and the detected value is transmittable to the control module (11), and wherein the tire (15) has an RFID tag (19) with tire data which is readable by a reader (20) and transmittable to the control module (11), characterized by , that the spring-damper system (10) is configured to carry out the method according to one of claims 1 to 8. [10] Spring-damper system (10) according to claim 9, characterized by, that the control module (11) has a radio module (17) which is equipped to transmit the detected tire pressure and at least part of the data of the read RFID tag to a stationary server (16) and to receive a target damping coefficient and a target spring stiffness and / or control signals.

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