Method for controlling an adjustable vibration damper

Abstract

Method for controlling an adjustable vibration damper having at least one adjustable damping valve, wherein at least one working chamber of the vibration damper is connected to a hydraulic device comprising a pump with a motor, wherein a resulting support force of the vibration damper to be calculated comprises a passive damping force of the at least one adjustable damping valve and an active actuating force of the hydraulic device, wherein, based on an actuating force request from a controller unit to the vibration damper, a pump signal and a valve signal for the at least one adjustable damping valve are determined, wherein the pump signal and the valve signal are determined on the basis of an actuator characteristic map comprising a plurality of characteristic curves for actuating currents for actuating the adjustable damping valve, wherein the characteristic curves representing the actuating currents are at least tangent to a pump characteristic curve,so that the pump signal and the valve signal are determined via a point of contact between the pump characteristic curve and a current characteristic curve in combination with the actuating force requirement.

Description

[0001] The invention relates to a method for controlling an adjustable vibration damper according to the preamble of patent claim 1.

[0002] DE 10 2018 221 576 A1 describes an adjustable vibration damper featuring adjustable damping valves that throttle the damping medium flow between two working chambers. An adjustable damping valve device is provided for each flow direction of the damping medium or each working direction of the vibration damper.

[0003] Furthermore, the vibration damper is connected to a hydraulic system comprising a pump with a motor. Fluid connections between each working chamber and the reversible pump allow the vibration damper to not only generate a passive damping force, but also act as an actively driven actuator, exerting a force on, for example, a vehicle body. This can be used, for example, to level a vehicle body relative to the road surface, e.g., when cornering.

[0004] Both the pump and the damping valve assembly are continuously adjustable. Both passive damping forces and the active actuating force are utilized for leveling.

[0005] To ensure the simplest possible interaction of the two force components, a control unit, reference number 46, is used in DE 10 2018 221 576 A1, which has a target pressure and parameters for the pump and the operating behavior of the vibration damper as input variables and defines a target operating point for the pump and the adjustable vibration dampers.

[0006] One problem arises when, for example, a low-frequency actuating force must be applied over an extended period of time, while road excitation occurs superimposed on it. An unfavorable combination of the actuating force of the pump and the damping force of the adjustable damping valve can then result in a lack of comfort, especially with high-frequency excitation and, for example, during extended cornering.

[0007] The object of the present invention is to solve the comfort problem known from the prior art.

[0008] The solution to the problem is achieved in that the pump signal and the valve signal are determined on the basis of an actuator characteristic map which comprises a plurality of characteristic curves for actuating currents for actuating the adjustable damping valve, wherein the characteristic curves representing the actuating currents are at least tangent to a pump characteristic curve, so that a determination of the pump signal and the valve signal is made via a point of contact of the pump characteristic curve with a current characteristic curve in combination with the actuating force requirement.

[0009] By applying a pump characteristic curve, the calculation effort required to determine the actuating force components from the damping force and the hydraulic system is significantly simplified, allowing the chassis to be adapted very quickly to changing requirements. By using a pump characteristic curve, the travel speed is given higher priority than an optimized actuating force distribution.

[0010] With a normal pump characteristic curve, one can assume that at a force demand of 0 N, the damping force at the lowest current characteristic curve and pump demand are zero, i.e., the pump characteristic curve would pass through the origin of the actuator characteristic map. However, for the comfort behavior of a vehicle, it is significantly more advantageous if the pump characteristic curve is used with an offset, which amplifies the pump signal relative to the force demand.

[0011] In a further advantageous embodiment of the method, the offset is set as a function of at least one driving state parameter.

[0012] It has proven more advantageous to use a road signal representing a road surface as a relevant driving condition parameter for determining the offset. A road signal can be determined with comparatively little effort, for example, using a wheel acceleration sensor.

[0013] A linear function in the form of a straight line is preferably used for the pump characteristic curve. This provides a simple and unambiguous signal processing situation.

[0014] In addition to or in addition to the aforementioned offset of the pump characteristic curve, the slope of the linear function can be adjusted depending on the driving condition parameter.

[0015] Alternatively, the gradient of the linear function can also be adjusted so that the gradient is changed over the course of the pump characteristic curve by the driving state parameter. This would then transform a straight line as the pump characteristic curve into a curve comparable to a root or quadratic function.

[0016] The invention will be explained in more detail with the help of the following description of the figures.

[0017] It shows: Fig. 1 Schematic diagram of an adjustable vibration damper in combination with a hydraulic device Fig. 2 Controller structure for a method for controlling a vibration damper according to Fig. 1 Fig. 3A - 3C Characteristic maps for the controller structure according to Fig. 2

[0018] The Fig. Figure 1 shows a schematic diagram of an adjustable vibration damper 1, which comprises a working cylinder 3 filled with damping medium, in which an axially movable piston rod 5 is guided with a piston 7. The piston 7 divides the working cylinder 3 into a working chamber 9; 11 on the piston rod side and a working chamber 9; 11 remote from the piston rod. A compensation chamber 13 is provided to compensate for the volume displaced by the piston rod 5. The compensation chamber 13 does not necessarily have to be arranged within the working cylinder 3. The invention can be used for both a conventional single-tube and a dual-tube vibration damper. In this exemplary embodiment, the compensation chamber 13 is separated from the working chamber 11 remote from the piston rod by an axially movable separating piston 15.

[0019] The piston 7 can be equipped as a closed displacer or with any damping valve or pressure relief valve technology.

[0020] Furthermore, the vibration damper 1 comprises at least one adjustable damping valve 17; 19. In this exemplary embodiment, two adjustable damping valves 17; 19 are present, with flow passing through each adjustable damping valve in the direction of flow of a single working chamber 9; 11. The adjustable damping valves 9; 11 can be connected to the working chambers 9; 11 within the vibration damper 1, e.g., in the piston 7, on the outside of the working cylinder 3, or via an external fluid line 21; 23.

[0021] Connected hydraulically in parallel to the at least one adjustable damping valve 17; 19, the vibration damper 1 is connected to a hydraulic device 25 comprising at least one pump 27 with a motor 29. The pump 27 can be designed, for example, as a reversing pump with two delivery directions. Alternatively, a pump with a single delivery direction and at least one switching valve for selectively connecting the pump to one of the two working chambers 9; 11 can also be used.

[0022] The combination of a vibration damper 1 with the hydraulic device 25 represents an actuator 31, which can exert an active actuating force, e.g., on a vehicle body 32, via the pressure force generated by the hydraulic device 25. In addition, the passive damping force of the vibration damper 1, generated by the working movement of the vibration damper 1 and the flow through the adjustable damping valves 17; 19, can also be utilized. The resulting support force of the actuator 31 is therefore determined by the sum of the two actuating forces.

[0023] A control unit 33 is connected to the at least one adjustable damping valve 17; 19 as well as to the motor 29 of the pump 27. If the pump 27 itself can be adjusted, a control line can also lead to the pump 27.

[0024] This overall configuration is preferably intended for each individual vibration damper on / in the vehicle.

[0025] The control unit 33 is connected to a sensor system 35 that detects at least one driving condition parameter. Preferably, a sensor 37 is used to detect road surface excitation. Additional sensors can detect, for example, the driving speed, longitudinal and lateral acceleration, or their derivatives such as spring travel or suspension speed. For example, a CAN bus connection within a vehicle can be used to utilize existing signals for this application.

[0026] The Fig. 2 shows a controller structure 39 within the control unit 33 in Fig. 1. The controller structure 39 comprises several controller units. In a first controller unit 41, based on a predetermined actuating force F soll a target pressure difference Δ psollThe necessary parameters such as the pressurized surfaces in the vibration damper 1, the storage parameters and the ambient pressure can be used to determine the target pressure difference Δ psoll between the working chambers 7; 9. This output variable of the first control unit 39 "set pressure" is fed to a second control unit 43, which specifies a set operating point for the pump 27 and the adjustable damping valves 17; 19.

[0027] A third control unit 45 takes a speed n Pumpe the pump 27 and a speed signal v Dämpf of the vibration damper and calculates a volume flow Q Pumpe , ist , as well as the volume flows Q Zyl 1 ist , Q Zyl 2 ist , Q CDC1 ist and Q CDC 2 ist within the vibration damper. The parameters of pump 27 are known, so that the speed of pump 27 can be used to determine its instantaneous flow rate Q Pumpe ist is easy to calculate. Q Zyl 1 istand Q Zyl 2 ist represent the volume flows in the working spaces 9; 11 and “Q CDC “ represents a volume flow through one of the two adjustable damping valves 17; 19. These signals are also fed to the second control unit 43.

[0028] The second controller unit 43 stores characteristic maps 47 of the adjustable valves 17; 19. These characteristic maps 47 describe the functional relationship between the differential pressure and actuating current of the adjustable damping valves 17; 19 on the one hand, and the volume flow (X-axis) and actuating force of the pump (Y-axis) on the other.

[0029] Based on the characteristic maps 47 of the adjustable damping valves 17; 19 and a pump model, the parameters Δ Q Pumpe soll and Δ p Pumpe sollwhich are fed to a fourth controller unit 49, which represents a pump model. Additionally, the fourth controller unit 49 can also be fed with the signal "T öi", which represents an oil temperature. The fourth controller unit 49 outputs the signals n Pumpe soll and M vost . to a fifth control unit 51, which provides an actual signal n Pumpe ist about the pump speed. From these input signals, a motor current signal I Motor which is passed on to the motor 29 of the respective pump 27. The current motor torque can be calculated, for example, by means of a subordinate motor control from the phase currents of the pump 24.

[0030] As already explained, the pressure setpoints p CDC1 soll and p CDC2 soll as well as the volume flow specifications Q CDC1 soll and Q CDC2 solleach provided to a control unit of the adjustable damping valve 17; 19 as sixth and seventh control units 53; 55. Based on the current characteristic maps contained therein, the adjustment of the damping valves 17; 19 is carried out in the connected eighth and ninth control units 57; 59 by sending a current signal I CDC1 and I CDC2 is fed to the respective adjustable damping valve 17; 19.

[0031] For the control of the actuator 31, the resulting actuating force from passive damping force and active pump force 27 is considered, which is necessarily equal to zero when the pump 27 and the vibration damper 1 are at a standstill, as an actuator characteristic map 60 according to the Fig. 3 shows. Consequently, both the relevant characteristic curves for the adjustable damping valves 17; 19 and a pump characteristic curve 61, viewed in simplified terms, start at the origin of the characteristic map. The damping valve characteristic curves show a damping force FD as a function of a current I(x). For a desired actuating force, a practically infinite number of combinations of pump settings and damping valve settings are available. The course of the pump characteristic curve 61 is selected such that the characteristic curves I(X) representing the actuating currents are at least touched, or better yet, intersected, by the pump characteristic curve 61. A point of contact between the pump characteristic curve 61 and a current characteristic curve in combination with the actuating force requirement F determines the pump signal Q. Pumpe soll and the valve signal I(X). These adjustments of the basic parameters for the adjustable damping valves 17; 19 and for the pump 27 can be made very quickly.

[0032] For example, on an ideally flat road, one could set a high damping force (= high passive support force) and use a comparatively low pump flow rate. An ideally flat road would not present any comfort disadvantage even with a high damping force setting, as no excitation occurs. The support force would then be predominantly a passive damping force, e.g., to suppress rolling motion when cornering. This setting would also be very advantageous in terms of energy consumption.

[0033] Even a small excitation of the chassis and a related change in the actuating force F causes the operating point to move into the steeply declining characteristic curve range. This operating behavior manifests itself as a loss of comfort. An excitation of the chassis is always associated with a working movement of the vibration damper and consequently with a change in the volume of the working chambers 9; 11. This change in the working volume ΔV must be compensated by the pump 27 with a ΔQ in order to generate an actuating force on the pump side. If this actuating force F is not maintained on the pump side, the system reaches the area of ​​the declining characteristic curve of the adjustable damping valves 17; 19 and leads to the aforementioned disadvantage in comfort.

[0034] To minimize the effect of fluctuating actuating forces, the pump characteristic curve 61 is used with an offset 63, whereby the pump signal is amplified in relation to the actuating force requirement F. In Fig. 3B, this offset 63 tends to be small in order to optimize the pump work. Fig. Figure 3C shows that with a larger offset 63 of the pump characteristic curve 61 from the origin of the characteristic field, a larger excitation, equal to ΔQ, has no noticeable effect on the actuating force. A constant actuating force F then means no force jumps that would reduce comfort for vehicle occupants.

[0035] As already mentioned, greater pump work always requires greater energy input. A small offset 63 is desirable for this purpose. Therefore, offset 63 is adjusted depending on at least one driving condition parameter. A road signal representing a road surface is used as a relevant driving condition parameter to determine offset 63. For example, a wheel acceleration signal a Radof the wheel-side acceleration sensor 37. Of course, one could also record a displacement or speed signal from a spring-loaded wheel and use a time derivative as the signal.

[0036] In its simplest form, the pump characteristic curve 61 is used as a linear function in the form of a straight line. This pump characteristic curve 61 can not only be shifted in parallel with the offset 63, as the Fig. 3B and Fig. 3 C shows that the gradient of the pump characteristic curve 61 can also be changed depending on the driving state parameter, see pump characteristic curve 61'. The change can also vary within the pump characteristic curve 61'', so that the course of the pump characteristic curve is changed by the driving state parameter. Reference symbol 1 vibration damper 3 working cylinders 5 Piston rod 7 pistons 9 piston rod side working chamber 11 Working space remote from the piston rod 13 Compensation space 15 separating pistons 17 adjustable damping valve 19 adjustable damping valve 21 Fluid line 23 Fluid line 25 Hydraulic equipment 27 Pump 29 Engine 31 Actuator 32 Vehicle body 33 Control unit 35 Sensor technology 37 Sensor for detecting road excitation 39 Controller structure 41 first control unit 43 second control unit 45 third control unit 47 Characteristic map of the adjustable damping valve 49 fourth control unit 51 fifth control unit 53 sixth control unit 55 seventh control unit 57 eighth control unit 59 ninth control unit 60 Actuator map 61 Pump characteristic curve 63 Offset of the pump characteristic curve QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2018 221 576 A1 [0002, 0005]

Claims

[1] Method for controlling an adjustable vibration damper (1) having at least one adjustable damping valve (17; 19), wherein at least one working chamber (9; 11) of the vibration damper (1) is connected to a hydraulic device (25) comprising a pump (27) with a motor (29), wherein a resulting support force F of the vibration damper 1 to be calculated comprises a passive damping force of the at least one adjustable damping valve (17; 19) and an active actuating force of the hydraulic device (25), wherein, based on an actuating force request from a controller unit to the vibration damper (1), a pump signal and a valve signal for the at least one adjustable damping valve (17; 19) are determined, characterized by that the pump signal and the valve signal are determined on the basis of an actuator characteristic map (60) which comprises a plurality of characteristic curves for actuating currents I (X)for actuating the adjustable damping valve 1(7; 19), wherein the control currents I (X) representing characteristic curves are at least touched by a pump characteristic curve (61), so that a determination of the pump signal and the valve signal is made via a point of contact of the pump characteristic curve (61) with a current characteristic curve in combination with the actuating force requirement. [2] Method according to claim 1, characterized by that the pump characteristic curve (61) is used with an offset (63), whereby the pump signal is amplified in relation to the actuating force requirement. [3] Method according to claim 2, characterized by that the offset (63) is set depending on at least one driving state parameter. [4] Method according to claim 3, characterized by that a relevant driving condition parameter is a road signal representing a roadway a Rad used to determine the offset (63). [5] A method according to any claim 3 or 4, characterized by that the course of the pump characteristic curve (63) is changed by the driving state parameter. [6] Method according to at least one of claims 1 to 5, characterized by that the pump characteristic curve (61) is used as a linear function in the form of a straight line. [7] Method according to claim 6, characterized by that the slope of the linear function is adjusted depending on the driving state parameter. [8] Vibration damper (1) characterized by that the method according to claim 1 is used to control the vibration damper (1).

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