Method and system for determining the state of a vehicle

Abstract

The presented invention relates to a method (100) for determining a state of a vehicle, wherein the method (100) comprises: - Determining (101) a static pressure in at least one hydraulic actuator (205) of a height adjustment system (201) for changing the height of the vehicle, - Assigning (103) a state of the vehicle to the determined static pressure, using a given assignment scheme, - Output (105) of the state of the vehicle, wherein the static pressure in the at least one hydraulic actuator (205) is determined on the basis of a rotational speed and an electrical operating parameter of a pump motor of a pump (213) at at least two predetermined operating points of the pump when pumping hydraulic fluid into the at least one hydraulic actuator.

Description

[0001] The invention relates to a method for determining the state of a vehicle according to claim 1, a system for determining the state of a vehicle according to claim 14 and a program product according to claim 15.

[0002] Features according to the invention are specified in claim 1. Embodiments are the subject of claims 2 to 13.

[0003] Determining a vehicle's load status typically requires several sensors, such as pressure gauges. These sensors are expensive and prone to failure.

[0004] The need to determine the pressure of level control actuators is well-known from air suspension systems. Determining the air spring pressure allows conclusions to be drawn about the vehicle's load condition. For cost reasons, these systems typically use only a single, central pressure sensor integrated into the valve block. To enable this sensor to detect the static pressure of the individual air springs, the valves for one or more air springs are opened. Simultaneously, pressure must be prevented from escaping the valve block, for which the outlet line is closed by an electrically controlled release valve. The disadvantages of this solution are the requirement for a pressure sensor, an electrically controlled release valve, and the corresponding interfaces to the control unit.

[0005] Another option is direct pressure measurement in the actuators. The disadvantage here is the need for a pressure sensor per actuator, along with the associated wiring and signal interfaces to the control unit.

[0006] DE 10 2022 213630 A1 describes a method in which pressure peaks in a pressure system are avoided by means of a specifically calculated speed adjustment of a pump.

[0007] DE 10 2022 208706 A1 describes a method in which a gas pressure, a current and a temperature in an actuator are used to calculate a level position.

[0008] DE 19 511 591 A1 describes a system for load detection for a vehicle.

[0009] Furthermore, DE 199 63 402 A1, DE 20 2024 103 450 U1 and KR 10 2024 0 005 316 A represent the state of the art.

[0010] Against this background, it is an object of the presented invention to provide a means of determining a state of a vehicle, in particular its loading state, which is robust and cost-efficient.

[0011] Thus, according to a first aspect of the presented invention, a method for determining the state of a vehicle is presented.

[0012] The presented method comprises determining a static pressure in at least one hydraulic actuator of a height adjustment system for changing the height of the vehicle, assigning a state of the vehicle to the determined static pressure using a predefined assignment scheme, and outputting the state of the vehicle, wherein the static pressure in the at least one hydraulic actuator is determined using a rotational speed and an electrical operating parameter of a pump motor of a pump at at least two predefined operating points of the pump when pumping hydraulic fluid into the at least one hydraulic actuator.

[0013] In the context of the presented invention, the output of a state is understood to be a process in which a message describing the state is output, i.e., transferred, for example, to a memory, in particular an error memory, and / or transferred to a processing function, and / or displayed on an output unit, e.g., a screen. To avoid the use of additional sensors, the presented method is based on an approach in which the static pressure in at least one hydraulic actuator is determined from existing or easily ascertainable measured variables for controlling a motor-pump unit of the height adjustment system.

[0014] Using the presented method, it is possible to reliably determine the static pressure in the at least one hydraulic actuator of the height adjustment system, although the line losses usually cause a significant difference between the pump output and the actuator and depend on several influencing factors that are not measured.

[0015] This involves changing the fluid volume in at least one hydraulic actuator of the height adjustment system. This changes the length of the hydraulic actuator. Because the hydraulic actuator is positioned between the chassis and the vehicle body, this change in length causes the body to move vertically.

[0016] A pump driven by an electric motor with a known gear ratio generates a fluid flow through the lines of the height adjustment system. Electromechanical valves allow the flow to individual hydraulic actuators to be shut off. For example, another valve can be used to regulate the flow from specific hydraulic actuators to a reservoir without causing the pump to run in reverse.

[0017] The pump's motor is controlled by a control unit. This control unit can, among other things, directly or indirectly monitor the current draw and the motor's speed. Furthermore, it allows for the regulation of the motor current. Control parameters for this regulation can include, among others, the motor current (current control) or the motor speed (speed control).

[0018] The following relationships apply: The generated torque of an electric motor MM corresponds to its current consumption I. For the motor types used in this application, a linear relationship can be assumed: M M = m1 · I + n1. The constants m1 and n1 depend on the design data of the motor.

[0019] If the gear ratio between the motor and pump is 1:1, the motor torque corresponds to the pump's drive torque. Otherwise, the gear ratio factor f must be taken into account. MP=MMf

[0020] The drive torque of a pump M P corresponds to the pressure p it generates P For the pump types used in this application, a linear relationship can be assumed: p P = m2 · M P + n2. The constants m2 and n2 depend on the design data of the pump.

[0021] These relationships allow the pump pressure to be calculated directly from the measured motor current: p P = m3 · I + n3. The constants m3 and n3 depend on the design data of the motor-pump combination.

[0022] If the gear ratio between motor and pump is 1:1, the motor speed n corresponds to M also the speed of the pump n P Otherwise, the translation factor f must be taken into account here: n P = n M · f

[0023] The pump speed n P corresponds to the volume flow rate Q conveyed by them: Q = n P · V · η V Here, V denotes the displacement volume; a constant parameter that depends on the pump's design specifications. η V denotes the volumetric efficiency.

[0024] The volumetric efficiency typically decreases with increasing pump pressure. This effect can be represented with sufficient accuracy by a linear formula (1): nV=m4⋅pP+n4

[0025] The constants m4 and n4 depend primarily on the design data of the pump.

[0026] When the pump generates a flow rate, fluid flows through the pipes, valves, connections, etc. Pressure losses occur due to flow resistance. Therefore, the pressure at the pump outlet is higher than the pressure in the hydraulic consumer or actuator.

[0027] Conversely, this means that a pump pressure calculated from the pump motor current does not directly indicate the pressure in the actuator. For this, knowledge of the pressure drop Δp is required so that it can be subtracted from the pump pressure. However, the pressure drop is not a constant value, but depends, among other things, on the length and shape of the elements through which the fluid flows, the flow velocities, and the viscosity of the pumped fluid. While the properties of the pipes and valves may be known and constant, the viscosity of the fluid is often unknown because it is variable. Many hydraulic fluids, for example, exhibit a viscosity that is strongly temperature-dependent. Accurate temperature measurement is particularly complex in branched hydraulic systems, as the temperature can vary at different points in the system; especially since dissipation during operation leads to localized heating.Furthermore, normative requirements for hydraulic fluids often allow wide tolerances regarding viscosity, for example by defining only limit values ​​instead of permissible value ranges.

[0028] According to Bernoulli's pressure equation (2), there are other factors that cause a difference between the pressure measured at the pump outlet and the pressure measured in the actuator. These are explained for the sake of completeness; however, it should be noted beforehand that these effects are not significant for the application described here: pP=ρ2⋅u2+p+ρ⋅g⋅z

[0029] The first term describes the dynamic pressure and states that the flow velocity u leads to a pressure change. However, at the given flow velocities, this change is not significant. Otherwise, the term could be taken into account if the volumetric flow rate, the effective pipe diameter, and the fluid density ρ were known.

[0030] The third term describes the hydrostatic pressure. If the geodetic height difference z between the pump and actuator is small, this factor is also not significant.

[0031] The second summand, the operating pressure, therefore remains the only significant one and will be considered exclusively in the following.

[0032] The presented method is based on the fact that, in order to detect pressure losses in the height adjustment system without requiring precise knowledge of the properties of the fluid and the hydraulic components downstream of the pump, the effect is utilized that the relationship between the volume flow rate Q and the pressure loss Δp is known with sufficient accuracy. For example, this relationship is linear for purely laminar flow and can be calculated using formula (3): pp=m5⋅Q+n5

[0033] The slope m5 depends on the unknown properties of the fluid and the hydraulic components downstream of the pump and therefore cannot be determined initially. The coefficient n5 is the pressure that would prevail at the pump outlet if the flow rate were zero. It is already known that the pressure losses arise from the fluid flowing through the hydraulic components downstream of the pump. Accordingly, no pressure losses occur if there is no flow rate. Thus, the coefficient n5 corresponds to the static system pressure at the pump, so that: n5 = p stacic

[0034] Since, under static conditions, the pressure in all fluidically connected components is the same and there is no significant height difference between the pump and actuator, this pressure also corresponds to the desired pressure in the hydraulic actuator: p Actor = p static

[0035] Thus, the determination of the slope m5 remains. For this purpose, according to the invention, the pump is operated in quick succession at two different operating points, with the volume flow Q and the pressure at the pump outlet p being measured in each case. P is determined. The following applies to the first operating point A: P p,A = m5 · Q A + n5 and for the second operating point B: p p,B = m5 · Q B + n5 Substituting the formulas yields formula (4): pActor=pStatic=n5=pp,A−QA⋅pp,B−pp,AQB−QA

[0036] Accordingly, it may be provided that the pressure in the at least one hydraulic actuator is determined using the following mathematical relationship (5): pActor=pp,A−QA⋅pp,B−pp,AQB−QA where p Actor the pressure in which at least one hydraulic actuator, p p,A a pump pressure at the first operating point, p p,B a pump pressure at the second operating point, Q Aa volume flow at the pump outlet at the first operating point and Q B This corresponds to a volume flow rate at the pump outlet at the second operating point.

[0037] Alternatively, it can be provided that the static pressure is determined using a non-linear function, whereby the non-linear function is determined using pressures and / or rotational speeds at various predetermined operating points.

[0038] Once the static pressure in at least one hydraulic actuator is known, a vehicle state, such as a fault state or a load state, can be assigned to it using an assignment scheme. This assignment scheme could, for example, include a predefined table with values ​​or value ranges of the static pressure, which are assigned to the respective states.

[0039] Once the vehicle's condition is known, it can be displayed, for example, in a fault memory and / or on a screen.

[0040] The message may include a warning indicating a critical vehicle load condition if the measured static pressure exceeds a predetermined threshold.

[0041] By comparing the measured static pressure with a predefined threshold, a user can be informed about, for example, an overload or incorrect charging.

[0042] It may also be provided that the static pressure in the at least one hydraulic actuator is determined on the basis of a first rotational speed and a first electrical operating parameter of the pump motor at a first predetermined operating point, as well as a second rotational speed and a second electrical operating parameter at a predetermined second operating point, wherein the first operating point and the second operating point are different.

[0043] A combination of rotational speed and an electrical operating parameter, such as an electrical current drawn by the pump at two different operating points, has proven suitable for determining the static pressure in a given hydraulic actuator.

[0044] It may also be provided that the at least two operating points have different delivery pressures and delivery volume flows.

[0045] By using different delivery pressures and delivery volumes at at least two operating points, the static pressure can be determined validly and computationally efficiently.

[0046] It may also be provided that the at least two operating points are set by one of the following parameters for regulating the pump flow from the following list of parameters: speed or current consumption of the motor, volume flow or pressure of the pump, electrical or hydraulic power.

[0047] By changing a control parameter, the at least two operating points provided according to the invention can be set indirectly without directly adjusting their parameters.

[0048] It may also be provided that the electrical operating parameter of the pump motor includes a current consumption of the pump motor and / or a power consumption of the pump motor at a known supply voltage and / or a determined phase angle.

[0049] Based on the operating parameters current consumption of the pump motor and / or power consumption of the pump motor at a known supply voltage and / or determined phase angle, the power of the pump motor can be precisely determined.

[0050] It may also be provided that the delivery pressure and delivery volume flow rate are determined for each operating point.

[0051] For example, it may be planned that the delivery pressure is determined by a pressure sensor.

[0052] It may also be provided that the delivery pressure is derived from an electrical operating parameter of the pump motor, such as the current consumption or the phase angle.

[0053] By using an electrical operating parameter of the pump motor to determine the delivery pressure, a pressure sensor for determining the delivery pressure can be dispensed with.

[0054] It may also be provided that the flow rate is determined by a flow sensor.

[0055] It may also be possible to derive the delivery volume flow rate from an electrical operating parameter of the pump motor, such as the rotational speed.

[0056] By using an electrical operating parameter of the pump motor to determine the delivery volume flow rate, a volume flow sensor for determining the delivery volume flow rate can be dispensed with.

[0057] It may also be provided that when determining the static pressure in the at least one hydraulic actuator, a volumetric efficiency is taken into account, wherein the volumetric efficiency is determined by means of a characteristic map, a linear formula or a non-linear formula or is assumed to be constant, and / or the volumetric efficiency is formulated as a function of a temperature of the at least one hydraulic actuator, an ambient temperature and / or a number of operating hours of the at least one hydraulic actuator.

[0058] Formulas (6) and (7) can be used, for example, to calculate the efficiency for the two operating points: nV,A=m4⋅pP,A+n4 nV,B=m4⋅pP,B+n4

[0059] It may also be provided that the rotational speed of the pump motor is measured by means of a sensor, derived from a rotating field of the pump motor, or determined based on the course of an electric current drawn by the pump motor.

[0060] It may also be provided that the pump has a variable displacement volume and that the presented method is carried out using a respective set displacement volume.

[0061] To minimize the influence of a variable displacement geometry on the proposed method, this displacement geometry can be kept constant or set to a fixed value during the presented method.

[0062] It may also be provided that when determining the static pressure in the at least one hydraulic actuator, a geodetic pressure difference is taken into account, given a density of the fluid ρ and a height difference z between the pump outlet and the actuator, according to the following mathematical relationship as per formula (8): pActor=pstatic+ρ⋅g⋅z

[0063] Knowing a geodetic pressure difference allows its influence on a static pressure determined for a given hydraulic actuator to be compensated.

[0064] According to a second aspect, the presented invention relates to a system for determining the state of a vehicle.

[0065] The presented system comprises a height adjustment system for changing the height of the vehicle and a computing unit, the computing unit being configured to execute one possible embodiment of the presented method.

[0066] In the context of the presented invention, a computing unit is understood to be a computer, in particular a cloud computer, a processor, a control unit or any other programmable circuit.

[0067] According to a third aspect, the presented invention relates to a program product, wherein the program product comprises program code means which, when the program product is executed on a computing unit, configure the computing unit to execute a possible embodiment of the presented method.

[0068] Further features, details and advantages of the invention will become apparent from the wording of the claims and from the following description of exemplary embodiments with reference to the drawings. The drawings show: Fig. 1. A possible design of the presented procedure, Fig. 2 a possible design of the presented system, Fig. 3. A possible design of the presented program product with an algorithm for carrying out the presented procedure.

[0069] In Fig. 1 is a method 100 for determining the condition of a vehicle.

[0070] Procedure 100 includes a determination step 101 in which a static pressure in at least one hydraulic actuator of a height adjustment system for changing the height of the vehicle is determined.

[0071] Furthermore, the procedure 100 includes an assignment step 103, in which a state of the vehicle is assigned to the determined static pressure, based on a predefined assignment scheme.

[0072] Furthermore, procedure 100 includes an output step 105, in which the status of the vehicle is output.

[0073] It is intended that the static pressure in the at least one hydraulic actuator is determined based on a rotational speed and an electrical operating parameter of a pump motor of a pump at at least two predetermined operating points of the pump when pumping hydraulic fluid into the at least one hydraulic actuator.

[0074] In Fig. Figure 2 shows a system 200 for determining the state of a vehicle.

[0075] The system 200 comprises a height adjustment system 201 for changing the height of the vehicle and a computing unit 203, wherein the computing unit 203 is configured to perform the procedure 100 according to Fig. 1 to execute.

[0076] In the present case, the height adjustment system 201 comprises several hydraulic actuators 205 which are coupled to a hydraulic fluid reservoir 211 via lines 207 and electromechanical valves 209.

[0077] A pump 213 would be controlled or adjusted via a control unit 215.

[0078] An optional control valve 217 allows the flow rate from the hydraulic actuators 205 to the hydraulic fluid reservoir 211 to be set without running the pump 213 in reverse, so that an operating point of the pump can be freely set.

[0079] In Fig. 3 is an algorithm 300 for carrying out the procedure 100 according to Fig. 1 shown.

[0080] The following parameters are determined in advance by calculation or measurement and made available in the software: Gear ratio between motor and pump: f Pump displacement volume: V Constants for calculating pump pressure: m3, n3 Constants for calculating the volumetric efficiency: m4, n4

[0081] The following steps are performed during algorithm 300. 30: The algorithm 300 starts. 31: Adjustment of the stationary operating point A 32: Determination of the engine speed n M,A as well as the motor current I A 33: Adjustment of the stationary operating point B 34: Determination of the engine speed n M,B as well as the motor current I B 35: Calculation of the pump pressures for both operating points using the following formulas: pP,A=m3⋅IAf+n3 pP,B=m3⋅IBf+n3 36: Calculation of the volumetric efficiency for both operating points using the following formulas: nV,A=m4⋅pP,A+n4 nV,B=m4⋅pP,B+n4 37: Calculation of the pump speeds for both operating points using the following formulas: nP,A=nM,A⋅f nP,B=nM,B⋅f 38: Calculation of the volume flows for both operating points using the following formulas: QA=np,A⋅VA⋅ηV,A QB=np,A⋅VB⋅ηV,B 39: Calculation of static pressure using the following formula: pStatic=pp,A−QA⋅pp,B−pp,AQB−QA 40: The algorithm 300 ends.

[0082] The invention is not limited to one of the embodiments described above, but can be modified in many ways. Reference symbol list 100 procedures 101 Investigation Step 103 Assignment step 105 Output step 200 System 201 Height adjustment system 203 Computing Unit 205 hydraulic actuators 207 lines 209 electromechanical valves 211 Hydraulic reservoir 213 Pump 215 Control unit 217 Control valve 300 Algorithm 30 Start 31 Setting up a first work point 32 Determining a first motor speed and a first motor current 33 Setting up a second work point 34 Determining a second motor speed and a second motor current 35 Calculation of pump pressures 36 Calculation of volumetric efficiency 37 Calculation of pump speeds 38 Calculation of volume flows 39 Calculation of static pressure 40 End

Claims

Method (100) for determining a state of a vehicle, wherein the method (100) comprises: - Determining (101) a static pressure in at least one hydraulic actuator (205) of a height adjustment system (201) for changing the height of the vehicle, - Assigning (103) a state of the vehicle to the determined static pressure, using a predetermined assignment scheme, - Outputting (105) the state of the vehicle, wherein the static pressure in the at least one hydraulic actuator (205) is determined using a rotational speed and an electrical operating parameter of a pump motor of a pump (213) at at least two predetermined operating points of the pump when pumping hydraulic fluid into the at least one hydraulic actuator. Method (100) according to claim 1, characterized in that the method (100) further comprises: - outputting a message describing the state of the vehicle on an output unit. Method (100) according to claim 2, characterized in that the message includes a warning that reports a critical loading condition of the vehicle if the determined static pressure exceeds a predetermined threshold value. Method (100) according to one of the preceding claims, characterized in that the static pressure in the at least one hydraulic actuator (205) is determined on the basis of a first rotational speed and a first electrical operating parameter of the pump motor at a first predetermined operating point, as well as a second rotational speed and a second electrical operating parameter at a predetermined second operating point, wherein the first operating point and the second operating point are different. Method (100) according to claim 4, characterized in that the static pressure in the at least one hydraulic actuator (205) is determined using the following mathematical relationship: pstatic = pp, A − QA ⋅ pp, B − pp, AQB − QA where p static the static pressure in which at least one hydraulic actuator (205), p p,A a pump pressure at the first operating point, p p,B a pump pressure at the second operating point, Q A a volume flow at the pump outlet at the first operating point and Q B This corresponds to a volume flow rate at the pump outlet at the second operating point. Method (100) according to one of claims 1 to 4, characterized in that the static pressure is determined using a nonlinear function, wherein the nonlinear function is determined using pressures and / or rotational speeds at various predetermined operating points. Method (100) according to one of the preceding claims, characterized in that the at least two operating points have different delivery pressures and delivery volume flows. Method (100) according to one of the preceding claims, characterized in that the at least two operating points are set by one of the following: speed or current consumption of the motor, volume flow or pressure of the pump (213), electrical or hydraulic power. Method (100) according to one of the preceding claims, characterized in that the electrical operating parameter of the pump motor comprises a current consumption of the pump motor and / or a power consumption of the pump motor at a known supply voltage and / or a determined phase angle. Method (100) according to one of the preceding claims, characterized in that when determining the static pressure in the at least one hydraulic actuator (205) a volumetric efficiency is taken into account, wherein the volumetric efficiency is determined by means of a characteristic map, a linear formula or a non-linear formula or is assumed to be constant, and / or the volumetric efficiency is formulated as a function of a temperature of the at least one hydraulic actuator (205), an ambient temperature and / or a number of operating hours of the at least one hydraulic actuator (205). Method (100) according to one of the preceding claims, characterized in that the rotational speed of the pump motor is measured by means of a sensor or derived from a rotating field of the pump motor or determined on the basis of a course of an electric current drawn by the pump motor. Method (100) according to one of the preceding claims, characterized in that the pump has a variable displacement volume and the presented method is carried out on the basis of a respective set displacement volume. Method (100) according to one of the preceding claims, characterized in that when determining the static pressure in the at least one hydraulic actuator (205), a geodetic pressure difference is taken into account, given a density of the fluid ρ and a height difference z between the pump outlet and the actuator, according to the following mathematical relationship: pActor = pstatic + ρ ⋅ g ⋅ z System (200) for determining the state of a vehicle, wherein the system comprises: - a height adjustment system (201) for changing the height of the vehicle, - a computing unit (203), wherein the computing unit (203) is configured to perform a method (100) according to any one of claims 1 to 13. Program product, wherein the program product comprises program code means which, when the program product is executed on a computing unit, configure the computing unit to execute a method (100) according to any one of claims 1 to 13.

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