DE102020001633A1 - Roll stabilization system for a vehicle - Google Patents

Abstract

A roll stabilization system for a vehicle comprising four shock absorbers which are each assigned to a wheel of the vehicle, several hydraulic circuits each coupled with several shock absorbers, at least one diaphragm expansion tank coupled to the respective hydraulic circuit. Two hydraulic circuits are provided, each of which is coupled to all shock absorbers, and several diaphragm expansion vessels are provided that are coupled to the respective hydraulic circuit, the roll stabilization system comprising: a hydraulic pump coupled to a reservoir and via valves to the two hydraulic circuits for setting a hydraulic system pressure - pressure sensors coupled to the respective hydraulic circuit for measuring a hydraulic pressure in the respective hydraulic circuit, - comfort valves for fluidically connecting the two hydraulic circuits while the vehicle is traveling straight ahead and for fluidically separating the two hydraulic circuits when the vehicle is cornering, and - a hydraulic pressure regulator with a system pressure estimator and a volume error estimator.

Description

The invention relates to a roll stabilization system for a vehicle according to the features of the preamble of claim 1.

From the prior art, as in the US 7,751,959 B2 described, a semi-active anti-roll system known. A suspension system includes four electronically controlled actuators, one on each of the four wheels. The actuators are each controlled / regulated by an electronic control / regulating unit. The left front and right front actuators are mechanically linked. The left rear and right rear actuators are also mechanically interconnected. The only connection between the front two and the rear two actuators is an electronic connection through the electronic control unit.

From the WO 2004/085178 A1 an anti-roll system is known. The anti-roll system or roll stabilization system includes a stabilizer and an actuator designed as a swivel motor or cylinder on the front axle and on the rear axle of a motor vehicle to influence the stabilizer and a common supply of the actuators by means of a pump and a control valve.

In the DE 10 2017 215 526 B3 describes a switchable stabilizer arrangement of a vehicle for roll stabilization. It comprises a first and a second stabilizer half, each coupled to a wheel of the vehicle, wherein the first and the second stabilizer half are coupled by means of a hydraulic actuator so that they can rotate relative to one another about their longitudinal axis. The actuator has at least two working chambers filled with a hydraulic medium and comprises at least one fluid-conducting connection between the at least two working chambers, the passage cross section of which can be changed. The working chambers of the actuator themselves cannot be elastically deformed. Instead, a spring element, which is supported between a rotor and a stator of the actuator, is arranged in the at least two working chambers of the actuator and / or in at least two further working chambers of the actuator. Furthermore, the passage cross section of the fluid-conducting connection can be changed as a function of the oscillation frequency of the stabilizer arrangement.

The invention is based on the object of specifying a roll stabilization system for a vehicle that is improved compared to the prior art.

The object is achieved according to the invention by a roll stabilization system for a vehicle having the features of claim 1.

• - vier Stoßdämpfer, welche jeweils einem Rad des Fahrzeugs zugeordnet sind,
• - mehrere mit jeweils mehreren Stoßdämpfern gekoppelte Hydraulikkreise,
• - mindestens ein mit dem jeweiligen Hydraulikkreis gekoppeltes Membranausdehnungsgefäß,

A particularly semi-active roll stabilization system for a vehicle comprises

• - four shock absorbers, each assigned to a wheel of the vehicle,
• - several hydraulic circuits, each coupled with several shock absorbers,
• - at least one diaphragm expansion tank coupled to the respective hydraulic circuit,

• - eine mit einem Vorratsbehälter und über Ventile mit den beiden Hydraulikkreisen gekoppelte Hydraulikpumpe zur Einstellung eines hydraulischen Systemdrucks,
• - mit dem jeweiligen Hydraulikkreis gekoppelte Drucksensoren zur Messung eines hydraulischen Drucks im jeweiligen Hydraulikkreis,
• - Komfortventile zum fluidischen Verbinden der beiden Hydraulikkreise während einer Geradeausfahrt des Fahrzeugs und zum fluidischen Trennen der beiden Hydraulikkreise während einer Kurvenfahrt des Fahrzeugs, und
• - einen Hydraulikdruckregler mit einem Systemdruckschätzer und einem Volumenfehlerschätzer.

According to the invention, two hydraulic circuits are provided which are each coupled to all shock absorbers, and several diaphragm expansion vessels coupled to the respective hydraulic circuit are provided, the roll stabilization system comprising:

• - a hydraulic pump coupled to a reservoir and via valves to the two hydraulic circuits for setting a hydraulic system pressure,
• - Pressure sensors coupled to the respective hydraulic circuit for measuring a hydraulic pressure in the respective hydraulic circuit,
• Comfort valves for fluidly connecting the two hydraulic circuits while the vehicle is traveling straight ahead and for fluidically separating the two hydraulic circuits when the vehicle is cornering, and
• - a hydraulic pressure regulator with a system pressure estimator and a volume error estimator.

The system pressure estimator is set up to estimate the system pressure that will be established after cornering, based on the measured hydraulic pressures of the two hydraulic circuits, using an isothermal gas model while the vehicle is cornering. The hydraulic pressure regulator is set up to decide on the basis of this system pressure estimate whether oil has to be pumped into the hydraulic circuits or whether it has to be drained into the storage tank. The volume error estimator is set up to determine oil volumes for the two hydraulic circuits by means of damper travel of the vehicle determined by a level sensor system and the measured hydraulic pressures of the two hydraulic circuits, which must be pumped into the two hydraulic circuits in order to achieve a predetermined setpoint value for the system pressure. The hydraulic pressure regulator is set up, based on the ratio of these oil volumes, to open the valves to the two hydraulic circuits alternately in a pulse-width-modulated manner and, with the hydraulic pump, to share oil in the two To pump hydraulic circuits until the setpoint for the system pressure is reached.

The continuous pressure estimation makes it possible to determine the current system pressure in every driving situation. With the help of the alternating valve control, the setpoint of the system pressure can be adjusted within a few seconds even when cornering. The almost synchronous pressure increase in the two hydraulic circuits prevents the vehicle from tilting due to unequal pressures.

Embodiments of the invention are explained in more detail below with reference to drawings.

• 1 schematisch einen Systemaufbau eines Wankstabilisierungssystems für ein Fahrzeug,
• 2 schematisch zwei Hydraulikkreise des Wankstabilisierungssystems aus 1,
• 3 schematisch eine Reglerstruktur eines Hydraulikdruckreglers des Wankstabilisierungssystems aus 1, und
• 4 schematisch Verlaufskurven mehrerer Parameter des Wankstabilisierungssystems und des Fahrzeugs.

Show:

• 1 schematically a system structure of a roll stabilization system for a vehicle,
• 2 schematically two hydraulic circuits of the roll stabilization system 1 ,
• 3 schematically shows a controller structure of a hydraulic pressure controller of the roll stabilization system 1 , and
• 4th Schematic curves of several parameters of the roll stabilization system and the vehicle.

Corresponding parts are provided with the same reference symbols in all figures.

1 shows a schematic representation of a system structure of an, in particular semi-active, roll stabilization system 1 for a vehicle not shown in detail. This roll stabilization system 1 includes four shock absorbers VL , VR , HL , MR which are each assigned to a wheel of the vehicle, ie a front left shock absorber VL , a front right shock absorber VR , a rear left shock absorber HL and a rear right shock absorber MR .

The roll stabilization system also includes 1 two with the shock absorbers VL , VR , HL , MR coupled hydraulic circuits H1 , H2 . Every hydraulic circuit is included H1 , H2 with every shock absorber VL , VR , HL , MR coupled, but the hydraulic circuits are H1 , H2 each with different cylinder chambers of a hydraulic cylinder of the respective shock absorber VL , VR , HL , MR fluidically coupled by an in the respective shock absorber VL , VR , HL , MR hydraulically movable piston 2 are fluidically separated from each other.

It also includes the roll stabilization system 1 with the respective hydraulic circuit H1 , H2 coupled membrane expansion vessels 3 , in the example shown here per hydraulic circuit H1 , H2 two such membrane expansion vessels 3 . These diaphragm expansion vessels 3 each include one with the hydraulic circuit H1 , H2 fluidically coupled hydraulic chamber 3.1 and one of them by a flexible and fluid-tight, ie both liquid-tight and gas-tight, membrane 3.2 separate pneumatic chamber 3.3 , which is filled with a gas, for example with air or nitrogen. Through these membrane expansion vessels 3 are temperature-related hydraulic pressure fluctuations in the hydraulic circuits H1 , H2 avoided.

The roll stabilization system also includes 1 one with a storage container 4th and via valves 7H1 , 7H2 with the two hydraulic circuits H1 , H2 coupled hydraulic pump 5 for setting a hydraulic system pressure P _Sys , with the respective hydraulic circuit H1 , H2 coupled pressure sensors 6th for measuring a hydraulic pressure p _H1 , p _H2 in the respective hydraulic circuit H1 , H2 , Comfort valves 8th for the fluidic connection of the two hydraulic circuits H1 , H2 while the vehicle is traveling straight ahead and for fluidic separation of the two hydraulic circuits H1 , H2 while the vehicle is cornering, in the example shown four such comfort valves 8th , and one in 3 hydraulic pressure regulator shown in more detail 9 with a system pressure estimator 10 and a volume error estimator 11 .

The system pressure estimator 10 is set up for this, based on the measured hydraulic pressures p _H1 , p _{H2 of} the two hydraulic circuits while the vehicle is cornering H1 , H2 Using an isothermal gas model to estimate the system pressure psys that will be established after cornering. The hydraulic pressure regulator 9 is set up to decide on the basis of this system pressure estimate whether oil (or another hydraulic fluid used) is in the hydraulic circuits H1 , H2 needs to be pumped or into the storage tank 4th must be drained. For draining oil from the hydraulic circuits H1 , H2 into the storage container 4th is a hydraulic pump 5 immediate bypass line with a non-return valve 12 to the storage container 4th intended.

The volume error estimator 11 is set up for this purpose by means of a level sensor system 13 determined damper paths DW of the vehicle and the measured hydraulic pressures p _H1 , p _{H2 of} the two hydraulic circuits H1 , H2 Oil volumes V _errH1 , V _errH2 for the two hydraulic _circuits H1 , H2 to determine which is in the two hydraulic circuits H1 , H2 each must be pumped in order to achieve a predetermined setpoint value p _{Soll of} the system pressure p _Sys . The hydraulic pressure regulator 9 is set up to _operate the valves based on the ratio of these oil volumes V _errH1 , V _errH2 7H1 , 7H2 to the two hydraulic circuits H1 , H2 to open alternately with pulse width modulation and with the hydraulic pump 5 proportionally oil in the two hydraulic circuits H1 , H2 to pump until the setpoint p _set for the system pressure psys is reached.

Is it determined on the basis of the system pressure estimate that oil is in the reservoir 4th needs to be drained, then the volume error estimator determines 11 advantageously by means of the level sensors 13 determined damper travel DW of the vehicle and the measured hydraulic pressures p _H1 , p _{H2 of} the two hydraulic circuits H1 , H2 the oil volumes V _errH1 , V _errH2 for the two hydraulic _circuits H1 , H2 coming from the two hydraulic circuits H1 , H2 each in the storage container 4th must be drained in order to achieve the specified setpoint p _{setpoint of} the system pressure psys. This is where the volume error estimator is 11 advantageously set up accordingly to do this. The hydraulic pressure regulator 9 is then advantageously set up, based on the ratio of these oil volumes V _errH1 , V _errH2, the valves 7H1 , 7H2 to the two hydraulic circuits H1 , H2 , advantageously also pulse-width modulated and advantageously also alternately, to open and also the backflow valve 12 to open to share oil from the two hydraulic circuits H1 , H2 into the storage container 4th until the setpoint p _set for the system pressure psys is reached.

The two hydraulic circuits H1 , H2 are in 2 again shown schematically. 3 shows a schematic representation of a controller structure of the hydraulic pressure controller described above 9 .

The following is the roll stabilization system 1 , in particular its structure and functionality as well as the resulting process for its operation, based on this 1 to 3 again described in detail.

1 shows, as already described above, the system structure of the roll stabilization system 1 . Its main components have already been described. For completeness, clarity and comprehensibility of the presentation according to 1 Some of the other components shown are named below. So includes the roll stabilization system 1 In the example shown, there is also a roll stabilization control and / or regulation unit 14th . For example, is the hydraulic pressure regulator 9 in this roll stabilization control and / or regulation unit 14th integrated or the hydraulic pressure regulator 9 is for example with the roll stabilization control and / or regulation unit 14th identical. This roll stabilization control and / or regulation unit 14th is with a CAN network 15th connected to the vehicle. Furthermore, there is also a damper control and / or regulation unit 16 with this CAN network 15th connected to the vehicle.

The roll stabilization control and / or regulation unit 14th is with the comfort valves 8th , the valves 7H1 , 7H2 , the pressure sensors 6th , a motor of the hydraulic pump 5 and, as already mentioned, with the CAN network 15th connected to the vehicle.

As mentioned earlier, shows 2 the two hydraulic circuits H1 , H2 , the representation, in particular the position of the pistons 2 in the shock absorbers VL , VR , HL , MR and the filling of their cylinder chambers with oil and the filling of the hydraulic chambers 3.1 the diaphragm expansion vessels 3 with oil, corresponds to driving through a left turn with the vehicle. A corresponding roll angle ϕ of a vehicle body of the vehicle is also shown. Due to the roll angle ϕ, there is a volume shift ΔV with respect to the oil between the two hydraulic circuits H1 , H2 and therefore due to the compensation via the membrane expansion vessels 3 in the pneumatic chambers 3.3 the one with the first hydraulic circuit H1 coupled membrane expansion vessels 3 a first gas volume V _H1 and in the pneumatic chambers 3.3 the one with the second hydraulic circuit H2 coupled membrane expansion vessels 3 a second volume of gas V _H2 . The volume shift .DELTA.V can have a positive or negative sign, depending on whether a left or right curve is being driven through and in which direction the vehicle body is thus wobbling.

The calculations required for the functionality described above are explained below:

Due to the isothermal gas model, the following applies to isothermal compression: $$V_{H1}=\frac{p_0{V}_0}{p_{H1}}$$

$$V_{Soll}=\frac{p_0{V}_0}{p_{Soll}}$$

Here p _{0 is} a filling pressure of the pneumatic chambers 3.3 , ie from gas storage tanks in the diaphragm expansion vessels 3 , and V ₀ is a gas volume of the pneumatic chambers 3.3 , ie the gas storage of the diaphragm expansion vessels 3 . $${\mathrm{<figure-callout\; id="2"\; label="V\; H"\; filenames="DE102020001633A1\_0009.png,DE102020001633A1\_0010.png"\; state="\{\{state\}\}">V</figure-callout>}}_H=\frac{p_0{V}_0}{{\mathrm{<figure-callout\; id="2"\; label="p\; H"\; filenames="DE102020001633A1\_0009.png,DE102020001633A1\_0010.png"\; state="\{\{state\}\}">p</figure-callout>}}_H}$$

$$V_{\mathrm{S.}Oll}=\frac{p_0{V}_0}{p_{\mathrm{S.}Oll}}$$

V _{Soll is} a _target gas volume of the pneumatic chambers 3.3 , ie the gas storage of the diaphragm expansion vessels 3 , at target pressure, ie at The setpoint p _{setpoint of} the system pressure psys is available.

The filling pressure p ₀ and the gas volume V ₀ are specified. The pressure p _H1 , p _H2 in the respective hydraulic circuit H1 , H2 is by means of the pressure sensors 6th determined. The setpoint pressure, ie the setpoint p _{setpoint of} the system pressure P _Sys , results from a respective chassis setting of the vehicle and is therefore predetermined via the respective chassis setting.

$$V_{Gerade,H2}=V_{H2}-\mathrm{\Delta }V$$

The calculation of the volume errors for the respective hydraulic circuit H1 , H2 , ie the oil volume V _errH1 , V _errH2 , which in the respective hydraulic _circuit H1 , H2 must be pumped or drained from it, is carried out as follows: $$V_{Gerade,H1}=V_{H1}+\mathrm{\Delta }V$$

$$V_{Gerade,\mathrm{<figure-callout\; id="2"\; label="H"\; filenames="DE102020001633A1\_0009.png,DE102020001633A1\_0010.png"\; state="\{\{state\}\}">H</figure-callout>}2}=V_{H2}-\mathrm{\Delta }V$$

$$V_{err,H2}=V_{Gerade,H2}-V_{Soll}$$

V _{straight line, H1} and V _{straight line, H2 is} the gas volume in the pneumatic chambers 3.3 the diaphragm expansion vessels 3 of the respective hydraulic circuit H1 , H2 when the vehicle is traveling straight ahead, ie with a roll angle ϕ = 0. $$V_{err,H1}=V_{Gerade,H1}-V_{\mathrm{S.}Oll}$$

$$V_{err,\mathrm{<figure-callout\; id="2"\; label="H"\; filenames="DE102020001633A1\_0009.png,DE102020001633A1\_0010.png"\; state="\{\{state\}\}">H</figure-callout>}2}=V_{Gerade,H2}-V_{\mathrm{S.}Oll}$$

The volume shift ΔV can be derived from the roll angle ϕ, which is determined by the level sensors 13 can be determined.

The system pressure psys is calculated as follows: $$p_{\mathrm{S.}ys}=\frac{2p_0{V}_0}{V_{H1}+{\mathrm{<figure-callout\; id="2"\; label="V\; H"\; filenames="DE102020001633A1\_0009.png,DE102020001633A1\_0010.png"\; state="\{\{state\}\}">V</figure-callout>}}_H}$$

The regulator structure of the hydraulic pressure regulator described above 9 , what a 3 is shown schematically, will now be described again in detail. As mentioned earlier, the hydraulic pressure regulator includes 9 the system pressure estimator 10 and the volume error estimator 11 .

The system pressure estimator 10 uses the pressure p _H1 , p _H2 in the respective hydraulic circuit H1 , H2 , which by means of the pressure sensors 6th is determined to estimate the system pressure p _Sys .

Input quantities of the volume error estimator 11 are the damper paths DW, which are determined by the level sensors 13 can be determined, as well as the pressure p _H1 , p _H2 in the respective hydraulic circuit H1 , H2 , which by means of the pressure sensors 6th is determined, and the setpoint p _{setpoint of} the system pressure psys. The volume estimator 11 estimates the volume errors for the respective hydraulic circuit from this H1 , H2 , ie the oil volume V _errH1 , V _errH2 , which in the respective hydraulic _circuit H1 , H2 must be pumped or drained from it.

The one from the system pressure estimator 10 The estimated system pressure p _Sys is subtracted from the setpoint p _{Soll of} the system pressure psys in order to determine a pressure deviation p _err , which is a control requirement determination 18th is supplied, which determines whether there is a rule requirement RB or not. This result, that is to say whether or not there is a regular requirement RB, and that of the volume estimator 11 estimated volume error for the respective hydraulic circuit H1 , H2 , ie the oil volume V _errH1 , V _errH2 which is in the respective hydraulic _circuit H1 , H2 must be pumped or drained from this, are input variables of an actuator control 19th which due to this the valves accordingly 7H1 , 7H2 of the two hydraulic circuits H1 , H2 and the hydraulic pump 5 controls in the manner described above.

The following describes how the roll stabilization system works 1 and the procedure for its operation again briefly summarized. With this by means of the roll stabilization system 1 If hydraulic roll stabilization is enabled, the roll rigidity is influenced by the system pressure p _Sys . In different driving programs and in particular the different chassis settings used in this context, this system pressure psys is therefore generated via the hydraulic pump 5 varies.

When driving straight ahead, the two hydraulic circuits H1 , H2 through the comfort valves 8th connected so that in both hydraulic circuits H1 , H2 the same pressure p _H1 , p _H2 prevails. This pressure P _H1 , p _H2 can be via the pressure sensors 6th measured and corresponds to the system pressure psys when driving straight ahead.

The two hydraulic circuits are during cornering H1 , H2 of the, in particular semi-active, roll stabilization system 1 but separately and there are different pressures p _H1 , p _H2 in the two hydraulic circuits due to the roll support H1 , H2 . Thus there is no measurable controlled variable and an extended control method, as described above, is used.

The hydraulic pressure regulator described here 9 initially estimates, especially using its system pressure estimator 10 , based on the two measurable pressures p _H1 , p _H2 in the two Hydraulic circuits H1 , H2 the system pressure psys, which will be established according to the curve, via the isothermal gas model. On the basis of this system pressure estimate, a decision is made as to whether there is oil in the hydraulic circuits H1 , H2 needs to be pumped or whether oil in the reservoir 4th must be drained.

The second estimator, ie the volume error estimator 11 , determined by means of the level sensors 13 determined damper travel DW and by means of the measured pressures p _H1 , p _H2 in the two hydraulic circuits H1 , H2 the two oil volumes V _errH1 , V _errH2 , which are in the individual hydraulic _circuits H1 , H2 must be pumped in order to achieve the setpoint pressure, ie the setpoint p _{setpoint of} the system pressure P _Sys . Based on the ratio of these oil volumes V _errH1 , V _errH2 the valves 7H1 , 7H2 to the individual hydraulic circuits H1 , H2 pulse width modulated alternately opened to with the hydraulic pump 5 proportionally oil in the two hydraulic circuits H1 , H2 to pump. As soon as the setpoint p _Soll for the system pressure p _{Sys is} reached, pumping stops.

The continuous pressure estimation makes it possible to determine the currently applied system pressure p _Sys in every driving situation. With the help of the alternating valve control, the setpoint pressure, ie the setpoint p _{setpoint of} the system pressure psys, can be adjusted within a few seconds even when cornering. Due to the almost synchronous pressure increase in the individual hydraulic circuits H1 , H2 an inclined position of the vehicle due to unequal pressures p _H1 , p _{H2 is} avoided.

4th shows a schematic representation of an example of curves of several parameters of the roll stabilization system 1 or the vehicle, which consists of the structure described above and the mode of operation of the roll stabilization system described above 1 and thus result from the method described above for its operation in a selected example case.

The upper diagram shows the setpoint p _{Soll of} the system pressure P _Sys , the pressure p _H1 in the first hydraulic circuit H1 , measured by means of the first hydraulic circuit H1 assigned pressure sensor 6th , the pressure p _H2 in the second hydraulic circuit H2 , measured by means of the second hydraulic circuit H2 assigned pressure sensor 6th , and the estimated system pressure psys, each over time t.

The lower diagram shows a transverse acceleration a of the vehicle, a valve position and / or control of the valve 7H1 of the first hydraulic circuit H1 , a valve position and / or control of the valve 7H2 of the second hydraulic circuit H2 and an activity, ie a control and thus an activation and a deactivation of the hydraulic pump 5 shown.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• US 7751959 B2 [0002]
• WO 2004/085178 A1 [0003]
• DE 102017215526 B3 [0004]

Claims (1)

Roll stabilization system (1) for a vehicle, comprising - four shock absorbers (VL, VR, HL, HR), which are each assigned to a wheel of the vehicle, - several hydraulic circuits (H1) coupled with several shock absorbers (VL, VR, HL, HR) , H2), - at least one diaphragm expansion vessel (3) coupled to the respective hydraulic circuit (H1, H2), characterized in that two hydraulic circuits (H1, H2) are provided, each with all shock absorbers (VL, VR, HL, HR) are coupled, and that several diaphragm expansion vessels (3) coupled to the respective hydraulic circuit (H1, H2) are provided, the roll stabilization system (1) comprising: - one with a storage container (4) and via valves (7H1, 7H2) with the two Hydraulic pumps (5) coupled to hydraulic circuits (H1, H2) for setting a hydraulic system pressure (p _Sys ), - pressure sensors (6) coupled to the respective hydraulic circuit (H1, H2) for measuring a hydraulic pressure (p _H1 , p _H2 ) in the respective Hydraulic circuit (H1, H2), comfort valves (8) for fluidly connecting the two hydraulic circuits (H1, H2) while the vehicle is traveling straight ahead and for fluidically separating the two hydraulic circuits (H1, H2) when the vehicle is cornering, and - a hydraulic pressure regulator (9) with a system pressure estimator (10) and a volume error estimator (11), - wherein the system pressure estimator (10) is set up to calculate based on the measured hydraulic pressures (p _H1 , p _H2 ) of the two hydraulic circuits (H1 , H2) using an isothermal gas model to estimate the system pressure (psys) that will be established after cornering, - the hydraulic pressure regulator (9) is set up to decide on the basis of this system pressure estimate whether oil is in the hydraulic circuits (H1, H2) has to be pumped or has to be drained into the storage container (4), the volume error estimator (11) being set up to use a level sensor rik (13) determined damper travel (DW) of the vehicle and the measured hydraulic pressures (p _H1 , p _H2 ) of the two hydraulic _circuits (H1, H2) to determine oil volumes (V _errH1 , V _errH2 ) for the two hydraulic _circuits (H1, H2) which have to be pumped into the two hydraulic circuits (H1, H2) in order to achieve a predetermined setpoint value (p _setpoint ) of the system pressure (psys), and the hydraulic pressure regulator (9) is set up based on the ratio of these oil volumes (V _errH1 , V _errH2 ) to open the valves (7H1, 7H2) to the two hydraulic circuits (H1, H2) alternately with pulse width modulation and to pump a proportion of the oil into the two hydraulic circuits (H1, H2) with the hydraulic pump (5) until the The setpoint ( _PSoll ) for the system pressure (p _Sys ) has been reached.

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