Method for controlling a hydraulic actuator of an active chassis

Abstract

The method according to the invention is designed for controlling a hydraulic actuator (10) of an active spring-damper element (1) in a vehicle for damping a relative movement between a vehicle body (60) and a wheel suspension (70), wherein a hydraulic arrangement (20) is provided for controlling the hydraulic actuator (10), which comprises a hydraulic pump (21) and at least one control valve (25a, 25b). According to the invention, in a first method step, a relative movement between the vehicle body (60) and the wheel suspension (70) is detected. Based on the detected relative movement, a force to be applied by the hydraulic actuator (10) and a volume flow rate to be applied by the hydraulic pump (21) are determined. Subsequently, the rotational speed of the hydraulic pump (21) is set such that the volume flow rate required for applying the force is provided.

Description

[0001] The present invention relates to a method for controlling a hydraulic actuator of an active chassis or an active spring-damper element in a vehicle.

[0002] To meet the requirements for ride comfort and safety in different driving situations, many vehicle manufacturers rely on damper systems with so-called active dampers with a hydraulic actuator. The behavior of such dampers, with regard to damping properties and the force to be applied, can be highly dynamically adjusted to the respective requirements during operation. For this purpose, a hydraulic arrangement consisting of two hydraulic chambers separated by a piston is connected to the hydraulic actuator. The pressure in the hydraulic chambers can be varied in order to change the damping properties and the force applied by the damper or the hydraulic actuator. The hydraulic arrangement for adjusting the appropriate pressures typically comprises a hydraulic pump and two adjustable valves (called control valves or damper valves).Such a system is known, for example, from patent DE 10 2017 117 658 A1.

[0003] For the operation of the hydraulic actuator, the speed must be regulated in order to provide the appropriate forces. Document DE 102011076849 A1 discloses controlling the speed and direction of rotation of the hydraulic pump of an active chassis system based on measured pressures in the supply lines of a double-acting hydraulic actuator. Document JP 2013174262 A describes controlling the motor of a hydraulic pump of an active damper based on the pressure in a supply line and a damper force signal. Document JP 2014040129 A describes determining a speed control value of a pump motor of a hydraulic pump by multiplying the deviation between a thrust control value and an actual thrust value by a control gain.JP 2015101261 ​​A deals with an active chassis and describes determining a target control force based on the vertical acceleration / speed of an upper and lower part of a chassis spring, and controlling the speed of the active chassis pump such that the target control force can be generated. Patent EP 3378684 A1 discloses controlling the speed of the pump of an active chassis based on the properties of a roadway ahead. Document DE 102021117081 A1 describes determining a motor demand for the pump motor of an active chassis based on a current force demand. Patent JP 2017094808 A describes determining the speed of the pump of an active chassis based on the extension / retraction speed of an actuator.From document JP S60213512 A, it is known to control the pump of an active suspension based on a relative movement between the vehicle body and the axle of a wheel. Document US 2022118810 A1 deals with an active suspension and describes adjusting a torque or speed setting in response to a wheel event.

[0004] Against the background of the described prior art, the object of the present invention is to propose an alternative method for controlling a hydraulic actuator of an active spring-damper element. This object is achieved by the subject matter of the independent claim. Advantageous further developments of the invention are contained in the subclaims.

[0005] The method according to the invention is designed to control a hydraulic actuator of an active spring-damper element in a vehicle for damping a relative movement between a vehicle body and a wheel suspension, wherein a hydraulic arrangement comprising a hydraulic pump and at least one control valve is provided to control the hydraulic actuator. According to the invention, in a first method step, a relative movement between the vehicle body and the wheel suspension is detected. The vehicle body is referred to as the complete vehicle without the wheel suspension and the wheels. The term thus refers to the mass which is to be decoupled from the vertical movements of the wheel suspension or the wheel by the spring-damper system. Furthermore, based on the detected relative movement, a force to be provided by the hydraulic actuator and a volume flow to be provided by the hydraulic pump are determined.When determining the force, particular consideration is given to the direction of the force, the amplitude (i.e., the magnitude) of the force, and the dynamics of the force position. The speed of the hydraulic pump is then adjusted to provide the required flow rate. For the purposes of this application, the term "flow rate" always refers to the flow rate of the hydraulic fluid supplied by the hydraulic pump to the hydraulic chambers of the hydraulic actuator. Preferably, the required flow rate is then converted into a hydraulic pump speed required to generate the flow rate using a characteristic map.

[0006] In this way, it is possible to control the hydraulic pump, or more precisely the speed of the hydraulic pump.

[0007] In a preferred embodiment of the invention, the force to be applied by the hydraulic actuator is set by controlling at least one control valve in the hydraulic actuator. This occurs by changing the opening position of the control valve, which allows the pressure in a hydraulic chamber of the hydraulic actuator to be changed. Particularly preferably, the force setting is achieved by a pressure drop in one of the hydraulic chambers of the hydraulic actuator. A pressure drop caused by increasing the opening position of the control valve can be implemented more quickly than a pressure buildup, thereby increasing the dynamics of the force setting and improving the control of the hydraulic actuator.

[0008] In a further preferred embodiment of the invention, the relative movement between the wheel or wheel suspension and the vehicle body is detected predictively, i.e., before the relative movement occurs. This is done in particular by analyzing the ground conditions ahead of the vehicle, which is particularly preferably carried out by an optical sensor. Alternatively or additionally, information from a database can also be used to analyze the ground conditions. By predictively detecting the relative movement, the hydraulic pump and the control valve can be adjusted early on in order to increase the dynamics of the system and to be able to provide the force directly from the start when it is required, without delay.

[0009] In a further preferred embodiment of the invention, a driver input is taken into account when determining the volume flow required for the force to be applied and to be provided by the hydraulic pump. This input contains information about the desired behavior of the chassis, particularly with regard to a sporty or comfortable driving style, or similar. This driver input can be implemented, for example, by selecting various driving modes, as is already known in the prior art. This allows the operation of the hydraulic actuator and thus of the spring-damper element to be adapted to the driver's needs.

[0010] Further advantages, aspects, and details of the invention will become apparent from the following description with reference to the accompanying figures. They show: Fig. 1 shows a spring-damper element 1 with a hydraulic actuator 10 Fig. 2 shows a flowchart of an embodiment of a method according to the invention for controlling a hydraulic actuator 10

[0011] In Fig. 1 shows a spring-damper element 1 with a hydraulic actuator 10. The hydraulic actuator 10 has a hydraulic cylinder 11 in which a piston 12 is arranged in the plane of the drawing. Fig. 1 is movable up and down, back and forth. The hydraulic cylinder 11 with the piston 12, as hydraulic actuator 10, represents the damper of the spring-damper element 1.

[0012] The hydraulic actuator 10 is, for example, part of a wheel suspension system in a vehicle (not shown). The wheel suspension system comprises, for example, a front axle with two front wheels and a rear axle with two rear wheels. Representative of these possibilities is shown in Fig. 1 schematically shows a wheel suspension 70. Normally, at least one hydraulic actuator 10 is assigned to each wheel. In addition to the hydraulic actuator 10, i.e., the damper, the spring-damper element 1 has a spring element 50 arranged parallel to the hydraulic actuator 10. The spring-damper element 1 connects a vehicle body 60 to the wheel suspension 70 and is designed not to transmit a vertical movement of the wheel to the vehicle body 60, thus improving comfort for the vehicle occupants. It is thus intended to decouple the wheel suspension 70 from the vehicle body 60. To achieve this as best as possible, the hydraulic actuator 10 is designed to be active, whereby the force it exerts is controllable.

[0013] The hydraulic cylinder 11 is designed as a double-acting hydraulic cylinder 11 with a first hydraulic chamber 111 and a second hydraulic chamber 112. A hydraulic arrangement 20 is provided to control the hydraulic actuator 10.

[0014] The hydraulic arrangement 20 comprises a hydraulic pump 21, designed, for example, as a reversing pump, which is operable by an electric motor 22. The hydraulic arrangement 20 is operated with a hydraulic medium from a hydraulic reservoir 23.

[0015] The first hydraulic chamber 111 of the hydraulic cylinder 11 is connected to one side of the hydraulic pump 21 via a first hydraulic line 31. The second hydraulic chamber 112 of the hydraulic cylinder 11 is connected to the other side of the hydraulic pump 21 via a second hydraulic line 32.

[0016] A first hydraulic branch 41 and a second hydraulic branch 42 are provided in the first hydraulic line 31. A third hydraulic branch 43 and a fourth hydraulic branch 44 are provided in the second hydraulic line 32. The second branch 42 and fourth branch 44 are connected by a third hydraulic line 33. The first branch 41 and third branch 43 are connected by a fourth hydraulic line 34.

[0017] A fifth hydraulic branch 45 is provided in the fourth hydraulic line 34. A sixth hydraulic branch 46 is provided in the third hydraulic line 33. A fifth hydraulic line 35 extends from the sixth branch 46 via the fifth branch 45 to the hydraulic medium reservoir 23.

[0018] A first check valve 24a is arranged in the fourth hydraulic line 34 between the first branch 41 and the fifth branch 45. A second check valve 24b is also arranged in the fourth hydraulic line 34 between the third branch 43 and the fifth branch 45. The check valves 24a and 24b both close to the fifth branch 45.

[0019] A first control valve 25a, also referred to as a damping valve or damping control valve, is arranged in the third hydraulic line 33 between the second branch 42 and the sixth branch 46. A second control valve 25b, also referred to as a damping valve or damping control valve, is arranged in the third hydraulic line 33 between the sixth branch 46 and the fourth branch 44.

[0020] By adjusting a pressure difference between the first hydraulic chamber 111 and the second hydraulic chamber 112, a force of the damper 10, or more precisely, of the hydraulic piston 12, can be adjusted. If the hydraulic pump 21 is operated in such a way that a specific pressure is applied to the first hydraulic line 31, this pressure is accordingly present in the first hydraulic chamber 111.

[0021] Fig. Figure 2 shows a flow chart or flow diagram of an embodiment of the method according to the invention, which with reference also to Fig.1 will be explained in more detail below. In a first method step, a relative movement between the vehicle body 60 and the wheel suspension 70 is determined. For this purpose, suitable acceleration sensors can be provided, for example, which detect a movement of both the vehicle body 60 and the wheel suspension 70, and thus the relative movement can be calculated. Alternatively, there are numerous other possibilities for detecting a relative movement. When detecting the relative movement, it is analyzed in particular with regard to the maximum movement, i.e., the amount of change in position, as well as the dynamics with which the movement occurs.

[0022] Subsequently, based on the detected relative movement, a force to be applied by the hydraulic actuator is determined, taking into account in particular the direction of the force, the amplitude (i.e. the magnitude of the force), and the dynamics of the force setting. From the determined force, the force setting is then determined by changing the opening position of a control valve 25a, 25b, and the force is set accordingly. The force setting is preferably achieved by a pressure drop in the corresponding hydraulic chamber 111, 112, which is caused by an opening of the corresponding control valve 25a, 25b. If, for example, a compressive force is to be applied to the wheel suspension 70 by the hydraulic actuator 12, the first control valve 25a increases its opening position, whereby the pressure in the first hydraulic chamber 111 drops and the piston of the hydraulic actuator 10 is pushed upwards in the plane of the drawing, thus allowing the force to be set.

[0023] At the same time, the volume of the second hydraulic chamber 112 suddenly increases, so that the pressure there also threatens to drop. To compensate for this, a volume flow required for the force setting and to be provided by the hydraulic pump 21 to the second hydraulic chamber 112 is determined based on the detected relative movement between the vehicle body 60 and the wheel suspension 70. The required pump speed and delivery direction are then determined from the required volume flow, and the hydraulic pump 21 is operated accordingly. Through the interaction of the control valves 25a, 25b and the hydraulic pump 21, the required force to be provided by the hydraulic actuator can thus be provided.

[0024] In cases where the volume flow induced due to the relative movement from one hydraulic chamber 111, 112 into the other hydraulic chamber 112 via one of the control valves 25a, 25b and check valves 24a, 24b is sufficient, no additional volume flow needs to be provided by the hydraulic pump 21. 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 2017 117 658 A1

[0002] DE 102011076849 A1

[0003] JP 2013174262 A

[0003] JP 2014040129 A

[0003] JP 2015101261 ​​A

[0003] EP 3378684 A1

[0003] DE 102021117081 A1

[0003] JP 2017094808 A

[0003] JP S60213512 A

[0003] US 2022118810 A1

[0003]

Claims

[1] Method for controlling a hydraulic actuator (10) of an active spring-damper element (1) in a vehicle for damping a relative movement between a vehicle body (60) and a wheel suspension (70), wherein a hydraulic arrangement (20) comprising a hydraulic pump (21) and at least one control valve (25a, 25b) is arranged to control the hydraulic actuator (10), wherein a relative movement between the vehicle body (60) and the wheel suspension (70) is detected, based on the detected relative movement, a force to be provided by the hydraulic actuator (10) and a volume flow to be provided by the hydraulic pump (21) are determined, and a speed of the hydraulic pump (21) is set such that the volume flow required for setting the force is provided. [2] Method according to the preceding claim, wherein the force to be set is set by controlling the at least one control valve (25a, 25b) in the hydraulic actuator (10). [3] Method according to the preceding claim, wherein the control of the control valve (25a, 25b) is carried out in such a way that a pressure drop occurs in a hydraulic chamber (111, 112) of the hydraulic actuator (10). [4] Method according to one of the preceding claims, wherein the relative movement is already detected predictively. [5] Method according to one of the preceding claims, wherein a driver input is taken into account in determining the volume flow required for the force to be applied.

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