Method for controlling an adjustable damper

Abstract

The invention relates to a method for controlling an adjustable vibration damper having at least one adjustable damping valve, at least one working chamber of the vibration damper being connected to a hydraulic device comprising a pump with a motor, the generated support force of the shock absorber to be calculated comprises a passive damping force of the at least one adjustable damping valve and an active adjusting force of the hydraulic device, a pump signal and a valve signal of the at least one adjustable damping valve are determined from an adjusting force requirement of the adjuster unit for the shock absorber, a pump signal and a valve signal are determined on the basis of a family of actuator characteristic curves comprising a plurality of characteristic curves of an adjustment current for actuating the adjustable damping valve, the characteristic curve characterizing the adjustment current being at least tangent to the pump characteristic curve, and the characteristic curve characterizing the adjustment current being at least tangent to the pump characteristic curve. The pump signal and the valve signal are determined through the contact point of the pump characteristic curve and the current characteristic curve in combination with the adjusting force requirement.

Description

Field of the Invention

[0001] The present invention relates to a method for controlling an adjustable shock absorber as described in the preamble of claim 1. Background Art

[0002] DE 10 2018 221 576 A1 describes an adjustable shock absorber having an adjustable damping valve that throttles the volume flow of damping medium between two working chambers. An adjustable damping valve device is provided for each flow direction of the damping medium or for each working direction of the shock absorber.

[0003] Furthermore, the shock absorber is connected to a hydraulic device that includes a pump with a motor. The fluid connection between the respective working chamber and the reversible pump enables the shock absorber to not only generate passive damping forces, but also to act as an actively driven actuator, for example, to exert adjustment forces on the vehicle body. Thus, for example, during cornering, it is possible to level the vehicle body relative to the road surface.

[0004] The pump and the damping valve device are continuously adjustable. To level the vehicle body, both passive damping forces and active adjustment forces are used.

[0005] To achieve the simplest possible interaction between the two force components, a regulator unit with the reference numeral 46 is used in DE 10 2018 221 576 A1. The regulator unit has the target pressure and parameters for the operating characteristics of the pump and the shock absorber as input variables and determines the target operating points of the pump and the adjustable shock absorber.

[0006] A problem is that, for example, if a low-frequency adjustment force has to be exerted over a relatively long period of time and road excitations are superimposed thereon, a lack of comfort may occur under an unfavorable combination of the adjustment force of the pump and the damping force of the adjustable damping valve, especially in the case of high-frequency excitations and, for example, cornering for a long time. Summary of the Invention

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

[0008] The solution to this object is to determine a pump signal and a valve signal based on a family of actuator characteristic curves that includes a plurality of characteristic curves of an adjustment current for actuating an adjustable damping valve, wherein the characteristic curves representing the adjustment current are at least tangent to the pump characteristic curve, so that the pump signal and the valve signal are determined by the contact point of the pump characteristic curve and the current characteristic curve in combination with the adjustment force requirement.

[0009] By using the pump characteristic curve, the computational effort for determining the regulating force component by the damping force and the hydraulic device will be significantly reduced, so that the chassis can very quickly adapt to changing requirements. In the case of using the pump characteristic curve, the moving speed has a higher priority than the optimized regulating force distribution.

[0010] For a normal pump characteristic curve, it can be assumed that when the regulating force requirement is 0 N, the pump requirement and the damping force on the lowest current characteristic curve are zero, that is, the pump characteristic curve will extend through the origin of the actuator characteristic curve family. However, if a pump characteristic curve with an offset is used, whereby the pump signal is amplified corresponding to the regulating force requirement, it is significantly more favorable for the comfort characteristics of the vehicle.

[0011] In a further advantageous design of the method, the offset is set according to at least one driving state parameter.

[0012] Here it has proven advantageous to use the lane signal characterizing the lane to determine the offset as the relevant driving state parameter. The lane signal can be obtained relatively easily, for example, by using a wheel acceleration sensor.

[0013] Preferably, a linear function in the form of a straight line is used for the pump characteristic curve. Thereby, the signal processing situation is simple and clear.

[0014] In addition to or as a supplement to the offset of the pump characteristic curve, the slope of the linear function can also be adjusted according to the driving state parameter.

[0015] Alternatively, the slope of the linear function can also be adjusted in such a way that the slope is changed along the trend of the pump characteristic curve by the driving state parameter. Thus, for example, a curve similar to a root function or a square function can be obtained from a straight line as the pump characteristic curve. Description of the Drawings

[0016] The present invention will be explained in more detail based on the following drawings, wherein:

[0017] Figure 1 is a schematic diagram of the combination of an adjustable shock absorber and a hydraulic device;

[0018] Figure 2 shows the regulator structure for the method of controlling the shock absorber according to Figure 1 ;

[0019] Figures 3A to 3C shows Figure 2 the family of characteristic curves of the regulator structure according to Detailed Description of the Invention

[0020] Figure 1The schematic diagram of an adjustable shock absorber 1 is shown. The shock absorber includes a working cylinder 3 filled with a damping medium, in which an axially movable piston rod 5 with a piston 7 is guided. The piston 7 divides the working cylinder 3 into a working chamber 9 on the piston rod side and a working chamber 11 away from the piston rod. In order to compensate for the volume displaced by the piston rod 5, a compensation chamber 13 is provided. The compensation chamber 13 does not have to be arranged within the working cylinder 3. The present invention can be used both for single-tube shock absorbers known per se and for double-tube shock absorbers. In this embodiment, an axially movable separating piston 15 separates the compensation chamber 13 from the working chamber 11 away from the piston rod.

[0021] The piston 7 can be equipped as a closed displacer or with any damping valve mechanism or overpressure valve mechanism.

[0022] In addition, the shock absorber 1 further includes at least one adjustable damping valve 17, 19. In this embodiment, there are two adjustable damping valves 17, 19, and one adjustable damping valve flows through respectively along the flow direction towards the single working chambers 9, 11. The adjustable damping valves 17, 19 can be connected to the working chambers 9, 11 within the shock absorber 1, i.e., for example, in the piston 7 on the outside of the working cylinder 3, or also through external fluid lines 21, 23.

[0023] The shock absorber 1 is connected to a hydraulic device 25 in a manner hydraulically parallel to at least one adjustable damping valve 17, 19. The hydraulic device includes at least one pump 27 with a motor 29. The pump 27 can be designed, for example, as a reversible pump with two delivery directions. Alternatively, a pump with a single delivery direction and at least one reversing valve can also be used, and the reversing valve is used to selectively connect the pump to one of the two working chambers 9, 11.

[0024] The combination of the shock absorber 1 and the hydraulic device 25 forms an actuator 31, which can apply an active adjustment force to the vehicle body 32, for example, through the pressure generated by the hydraulic device 25. In addition, the passive damping force of the shock absorber 1 generated by the working movement of the shock absorber 1 and the flow through the adjustable damping valves 17, 19 can also be used to generate a passive adjustment force. Therefore, the final support force of the actuator 31 is determined by the sum of the two adjustment forces.

[0025] The controller 33 is connected both to at least one adjustable damping valve 17, 19 and to the motor 29 of the pump 27. If the pump 27 itself is adjustable, the control line can also lead to the pump 27.

[0026] This overall construction is preferably provided for each individual shock absorber on / in a vehicle.

[0027] The controller 33 is connected to a sensing mechanism 35 which detects at least one driving state parameter. Preferably, a sensor 37 for detecting lane excitation is used. Additional sensors can for example determine the driving speed, the longitudinal acceleration and the lateral acceleration or derived quantities thereof, such as spring deflections or bounce speeds. Here, for example, the CAN bus connection within the vehicle can be utilized in order to use the existing signals for this application.

[0028] Figure 2 shows Figure 1 the regulator structure 39 within the controller 33. The regulator structure 39 comprises a plurality of regulator units. In a first regulator unit 41, a target pressure difference Δp 目标 is calculated based on a predetermined adjustment force F 目标 . As the target pressure difference Δp 目标 between the working chambers 7, 9, the parameters required therefor, such as the area on which pressure is exerted in the damper 1, the storage parameter and the ambient pressure, can be calculated. This output variable “target pressure” of the first regulator unit 39 is supplied to a second regulator unit 43 which specifies the target operating points of the pump 27 and the adjustable damping valves 17, 19.

[0029] A third regulator unit 45 receives the rotational speed n 泵 of the pump 27 as well as the speed signal v 减振器 of the damper and therefrom calculates the volume flow rate Q 泵 in the damper, the volume flow rates Q Zyl1,实际 , Q Zyl2,实际 , Q CDC1,实际 and Q CDC2,实际 . The parameters of the pump 27 are known, so that its current delivery rate Q 泵 can also be easily calculated based on the rotational speed of the pump 27. Q Zyl1 and Q Zyl2 represent the volume flow rates in the working chambers 9, 11 and “Q CDC ” represents the volume flow rate through one of the two adjustable damping valves 17, 19 respectively. These signals are also supplied to the second regulator unit 43.

[0030] Characteristic curve families 47 of the adjustable damping valves 17, 19 are stored in the second regulator unit 43. These characteristic curve families 47 describe on the one hand the functional relationship between the pressure difference and the adjustment current of the adjustable damping valves 17, 19 and on the other hand the functional relationship between the volume flow rate (X-axis) and the adjustment force of the pump (Y-axis).

[0031] Based on the characteristic curve families 47 of the adjustable damping valves 17, 19 and the pump model, the parameters ΔQ 泵,目标 and Δp 泵,目标, which is supplied to a fourth regulator unit 49 representing the pump model. In addition, a signal "T 油 " representing the oil temperature can also be supplied to the fourth regulator unit 49. The fourth regulator unit 49 further transmits signals n 泵,目标 and M Vorst . to a fifth regulator unit 51, which receives a signal n 泵,实际 regarding the actual pump speed. The motor current signal I 马达 is determined from these input signals and is further transmitted to the motor 29 of the corresponding pump 27. The current motor torque can be calculated, for example, from the phase current of the pump 24 by means of the underlying motor control system.

[0032] As already explained, the pressure target values p CDC1,目标 and p CDC2,目标 as well as the volume flow preset values Q CDC1,目标 and Q CDC2,目标 are respectively supplied to one of the regulator units, namely the sixth regulator unit 53 and the seventh regulator unit 55, of the adjustable damping valves 17, 19. The setting of the damping valves 17, 19 is carried out in the connected eighth regulator unit 57 and ninth regulator unit 59 according to the current characteristic curve families contained therein, by supplying the current signals I CDC1 and I CDC2 to the corresponding adjustable damping valves 17, 19.

[0033] For the control of the actuator 31, the adjustment force generated by the passive damping force and the active pumping force 27 is considered. When the pump 27 is not working and the shock absorber 1 is not working, this adjustment force must be equal to 0, as shown by the actuator characteristic curve family 60 according to FIG. 3. Therefore, seen simply, both the relevant characteristic curves of the adjustable damping valves 17, 19 and the pump characteristic curve 61 start from the origin of the characteristic curve family. The damping valve characteristic curve shows the damping force FD varying with the current intensity I (X) . In fact, an infinite number of combinations of pump settings and damping valve settings can be used to achieve the desired adjustment force. Here, the pump characteristic curve 61 is selected in terms of its trend such that the pump characteristic curve 61 is at least tangent to, and preferably intersects, the characteristic curve I (X) representing the adjustment current. The pump signal Q 泵,目标 and the valve signal I (X) are determined through the contact point of the pump characteristic curve 61 and the current characteristic curve in combination with the adjustment force requirement F. The basic parameters of the adjustable damping valves 17, 19 and the pump 27 can be set very quickly.

[0034] On an ideal, flat road, for example, a large damping force, i.e., a large passive support force, can be set, and a relatively small pump volume flow rate can be used. Even with a stiff damping force setting, an ideal, flat road will not exhibit comfort disadvantages because there is no excitation. Thus, the support force will mainly be the passive damping force, which is used, for example, to suppress roll motion during cornering. This setting is also very advantageous in terms of energy use.

[0035] Even a small excitation of the chassis and the associated change in the driving force F will cause the operating point to shift into the steeply declining characteristic curve region. This operating characteristic will significantly reduce comfort. The excitation of the chassis is always associated with the working motion of the shock absorber and thus with the volume change of the working chambers 9, 11. This change in the working volume ΔV must be compensated by the pump 27 with ΔQ in order to generate an adjustment force on the pump side. If this adjustment force F is not maintained on the pump side, the system reaches the region of the declining characteristic curve of the adjustable damping valves 17, 19 and results in the aforementioned comfort drawbacks.

[0036] To minimize the influence of the fluctuating adjustment force, a pump characteristic curve 61 with an offset 63 is used, whereby the pump signal is amplified relative to the adjustment force requirement F. In Figure 3B this, the offset 63 is often chosen to be small in order to optimize the pump work. Figure 3C It is shown that when the pump characteristic curve 61 has a large offset 63 relative to the origin of the characteristic curve family, a greater excitation, the same magnitude of ΔQ has no significant effect on the adjustment force. A constant adjustment force F then means that there will be no force jumps that would reduce the comfort of the vehicle occupants.

[0037] As already mentioned, a greater pump work always requires more energy. For this purpose, a small offset 63 is ideal. Therefore, the offset 63 is set according to at least one driving state parameter. As the relevant driving state parameter, a lane signal characterizing the lane is used to determine the offset 63. For example, the wheel acceleration signal a of the wheel-side acceleration sensor 37 can be used 车轮 . Of course, the displacement signal or speed signal of the elastic wheel can also be detected, and the time derivative can be used as the signal.

[0038] In the simplest form, a linear function in the form of a straight line is used for the pump characteristic curve 61. This pump characteristic curve 61 can not only be moved parallel with an offset 63, as Figure 3B and Figure 3C shown, but also the slope of the pump characteristic curve 61 can be changed according to the driving state parameter, see the pump characteristic curve 61'. This change can also vary within the pump characteristic curve 61", thereby changing the trend of the pump characteristic curve through the driving state parameter.

[0039] List of reference numerals:

[0040] 1 Shock absorber

[0041] 3 Working cylinder

[0042] 5 Piston rod

[0043] 7 Piston

[0044] 14 Working chamber on the piston - rod side

[0045] 17 Working chamber away from the piston - rod

[0046] 20 Compensation chamber

[0047] 23 Separation piston

[0048] 26 Adjustable damping valve

[0049] 29 Adjustable damping valve

[0050] 32 Fluid pipeline

[0051] 35 Fluid pipeline

[0052] 38 Hydraulic device

[0053] 41 Pump

[0054] 44 Motor

[0055] 47 Actuator

[0056] 50 Vehicle body

[0057] 53 Controller

[0058] 56 Sensing mechanism

[0059] 59 Sensor for detecting lane excitation

[0060] 62 Regulator structure

[0061] 65 First regulator unit

[0062] 68 Second regulator unit

[0063] 71 Third regulator unit

[0064] 74 Characteristic curve family of adjustable damping valve

[0065] 77 Fourth regulator unit

[0066] 80 Fifth regulator unit

[0067] 83 Sixth regulator unit

[0068] 86 Seventh regulator unit

[0069] 57 The eighth regulator unit

[0070] 59 The ninth regulator unit

[0071] 60 Actuator characteristic curve family

[0072] 61 Pump characteristic curve

[0073] 63 Offset of the pump characteristic curve.

Claims

1. Method for controlling an adjustable shock absorber (1), the shock absorber (1) having at least one adjustable damping valve (17, 19), wherein: At least one working chamber (9, 11) of the shock absorber (1) is connected to a hydraulic device (25), the hydraulic device comprising a pump (27) with a motor (29), wherein the generated supporting force (F) of the shock absorber (1) to be calculated comprises a passive damping force of at least one of the adjustable damping valves (17, 19) and an active adjusting force of the hydraulic device (25), wherein a pump signal and a valve signal of at least one of the adjustable damping valves (17, 19) are determined from an adjusting force requirement of the shock absorber (1) by a regulating unit, characterized in that the pump signal and the valve signal are determined based on an actuator characteristic curve group (60), the actuator characteristic curve group comprising an adjusting current (I (X) ), wherein the adjusting current is used to actuate the adjustable damping valve (17, 19), wherein the adjusting current (I (X) ) is at least tangent to the pump characteristic curve (61), so that the pump signal and the valve signal are determined by the contact point of the pump characteristic curve (61) with the current characteristic curve and in combination with the adjustment force requirement.

2. The method according to claim 1, characterized in that The pump characteristic curve (61) is used with an offset (63), whereby the pump signal is amplified relative to the actuating force requirement.

3. The method according to claim 2, characterized in that The offset (63) is set as a function of at least one driving state parameter.

4. The method according to claim 3, characterized in that Using lane signals (a 车轮 ) determines the offset (63) as a relevant driving state parameter.

5. The method according to any one of claims 3 or 4, characterized in that The course of the pump characteristic curve (63) is changed by means of the driving state parameter.

6. The method according to at least one of claims 1 to 5, characterized in that A linear function in the form of a straight line is used for the pump characteristic curve (61).

7. The method according to claim 6, characterized in that The slope of the linear function is adjusted as a function of the driving state parameter.

8. A shock absorber (1), characterized in that: The vibration damper (1) is controlled using the method according to claim 1.

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