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EP-4741953-A1 - METHOD FOR DETERMINING THE CONTROL VALUES OF A MANIPULATED VARIABLE FOR A PRESSURE MEDIUM SUPPLY SYSTEM OF A HYDRAULIC SYSTEM

EP4741953A1EP 4741953 A1EP4741953 A1EP 4741953A1EP-4741953-A1

Abstract

The invention relates to a method for determining control values of a manipulated variable for a pressure medium supply system of a hydraulic system with at least one hydraulic consumer (10), wherein the pressure medium supply system comprises a hydraulic machine (2) and an electric drive (4, 6) coupled thereto and is controlled by the manipulated variable, wherein an inverse plant model (47) is given for the hydraulic system, which uses values of a state variable to be controlled of the hydraulic system and of time derivatives of the state variable up to a predetermined maximum order as input values and maps these to an output value for the manipulated variable; comprising determining (110) trajectory values (36) of a trajectory for the time course of the state variable and derivative values (38, 40) for time derivatives of the course of the state variable up to the maximum order from predetermined setpoint values (32) for the state variable; Determining (120) compensation values (73) with a compensation controller (75) from a control deviation (61) between the trajectory values (36) and actual values (54) of the state variable; and determining (130) manipulated values (50) for the manipulated variable using the inverse plant model (47) from the trajectory values (36), the derivative values (38, 40) and the compensation values (73).

Inventors

  • ROSE, STEFFEN
  • WIEDMER, Fabian
  • Neyer, Daniel
  • HOFFMANN, DOMINIK THOMAS

Assignees

  • Robert Bosch GmbH

Dates

Publication Date
20260513
Application Date
20251103

Claims (20)

  1. Method for determining control values of a manipulated variable for a pressure medium supply system of a hydraulic system with at least one hydraulic consumer (10), wherein the pressure medium supply system has a hydraulic machine (2) and an electric drive (4, 6) coupled thereto and is controlled by the manipulated variable, wherein an inverse plant model (47) is given for the hydraulic system, which uses values of a state variable to be controlled of the hydraulic system and of time derivatives of the state variable up to a predetermined maximum order as input values and maps these to an output value for the manipulated variable; the procedure comprehensively: - Determining (110) trajectory values (36) of a trajectory for the time course of the state variable and derivative values (38, 40) for time derivatives of the course of the state variable up to the maximum order from given setpoint values (32) for the state variable; - Determining (120) compensation values (73) with a compensation controller (75) from a control deviation (61) between the trajectory values (36) and actual values (54) of the state variable; and - Determining (130) of control values (50) for the manipulated variable using the inverse path model (47) from the trajectory values (36), the derivative values (38, 40) and the compensation values (73).
  2. The method of claim 1, wherein when determining (130) the control values (50) for the control variable, the derivative values (40) of the time derivative with the maximum order are changed by the compensation values in order to determine modified derivative values (44); wherein the trajectory values (36), the derivative values (38) of time derivatives with an order smaller than the maximum order and the modified derivative values (44) are used as input values of the inverse path model (47); wherein, in particular, the compensation values (73) are added to the derivative values (40) of the time derivative with the maximum order in order to determine the modified derivative values (44).
  3. Method according to one of the preceding claims, wherein when determining (110) the trajectory values (36) and the derivative values (38, 40) a filter (34) whose order is equal to the maximum order is used to determine the trajectory values (36) and the derivative values from the specified setpoint values (32) for the state variable.
  4. Method according to claim 3, wherein the filter (34) comprises or is designed as a number of PT1 filters connected in series, the number being equal to the maximum order.
  5. A method according to one of the preceding claims, wherein one or more characteristic maps for the hydraulic machine (2) are used in the inverse system model (47); wherein, in particular, a volume flow characteristic map, which indicates the volume flow delivered by the hydraulic machine and which depends on a pressure and a speed of the hydraulic machine (2), and/or a torque characteristic map, which indicates the torque occurring at the hydraulic machine (2) and which depends on the pressure and the speed of the hydraulic machine (2), and/or one or more characteristic maps for the derivatives of the volume flow characteristic map and/or the torque characteristic map with respect to pressure or speed, and/or one or more inverted characteristic maps, which are inverses of the volume flow characteristic map or the torque characteristic map resolved with respect to pressure or speed, are used.
  6. Method according to one of the preceding claims, wherein when determining (110) the trajectory values (36) and the derivative values (38, 40) the derivative values for one of the temporal derivatives, in particular for the one with the maximum order, are limited upwards and/or downwards by respective first limiting values.
  7. The method of claim 6, wherein the first restriction values are varied depending on the trajectory values (36) and/or the derivative values that are not restricted, and/or on the actual value of the manipulated variable and/or on a possible range of values of the manipulated variable and/or on estimates of at least one disturbance variable determined by a disturbance estimation method, which represents an unobserved or is an unobservable quantity in the hydraulic system; wherein the at least one disturbance variable includes in particular a total volume flow rate of the at least one consumer and/or its time derivative.
  8. A method according to one of the preceding claims, wherein a disturbance estimation method is used to determine estimates for at least one disturbance variable, which is an unobserved or unobservable quantity in the hydraulic system; and wherein the estimates for the at least one disturbance variable are used when determining the trajectory values and the derivative values and/or in the inverse system model (47); wherein the at least one disturbance variable includes, in particular, a total volume flow rate of the at least one consumer and/or its time derivative.
  9. Method according to claim 7 or 8, wherein the disturbance estimation method uses an observer (112), in particular a Luenberger observer, or an iterative estimation method, in particular a Kalman filter.
  10. Method according to one of claims 7 to 9, wherein in the disturbance estimation method actual values of the torque (116) applied by the electric drive (2, 4) and/or the rotational speed (118) of the electric drive are used or evaluated.
  11. Method according to one of the preceding claims, wherein when determining (130) the control values for the control variable, output values (47) of the inverse path model (47) are restricted in order to determine the control values (50).
  12. Method according to claim 11, wherein the compensation controller (75) has an integral component; wherein difference values between the output values and the restricted control values (50) are determined and used in a first anti-windup function of the integral component.
  13. A method according to any of the preceding claims, wherein the compensation controller (75) has an integral component; wherein a second anti-windup function of the The integral part depends on the derivative values (38, 40), in particular the derivative values (38) of the first time derivative.
  14. Method according to claim 13, wherein the second anti-windup function limits the control deviation for the integral term downwards and/or upwards by respective second limit values, the second limit values depending on the derivative values (38, 40), in particular the derivative values (38) of the first time derivative; and/or wherein the second anti-windup function changes an integral factor depending on the derivative values (38, 40), in particular the derivative values (38) of the first time derivative; and where, in particular, the second restriction values and/or the integral factor are smaller in absolute value for derivative values (38, 40) that are larger in absolute value, especially for derivative values (38) of the first time derivative that are larger in absolute value.
  15. Method according to one of the preceding claims, wherein the manipulated variable is a torque to be applied by the electric drive (4, 6) or a rotational speed of the electric drive.
  16. Method according to one of the preceding claims, wherein the state variable is a pressure in the hydraulic system, in particular a pressure at a connection of the hydraulic machine (2) or a hydraulic line (12) connected to the connection or a hydraulic channel connected to the connection, a rotational speed of the hydraulic machine or a volume flow of pressure medium delivered by the hydraulic machine.
  17. Computing unit (20, 22) comprising a processor configured to perform the method according to any one of the preceding claims.
  18. Hydraulic system comprising a pressure medium supply system with a hydraulic machine (2) and an electric drive (4, 6) coupled thereto and a computing unit according to claim 17, wherein an inverse path model (47) for the A hydraulic system is given that uses values of a state variable of the hydraulic system to be controlled and of time derivatives of the state variable up to a predetermined maximum order as input values and maps these to an output value for the manipulated variable.
  19. Computer program comprising commands which, when the program is executed by the computing unit of the hydraulic system according to claim 18, cause it to execute the method according to claims 1 to 16.
  20. Computer-readable data carrier on which the computer program according to claim 18 is stored.

Description

The present invention relates to a method for determining control values of a control variable for a pressure medium supply system of a hydraulic system, as well as a computing unit and a computer program for its implementation and a hydraulic system. Background of the invention Machines, especially mobile construction equipment (e.g., excavators), can have a working hydraulic system to move components (e.g., boom sections) using hydraulic actuators (e.g., hydraulic cylinders and/or hydraulic motors). One way to make the use of the working hydraulic system more efficient is to provide a demand-based flow rate, for example, by using a variable displacement pump, which is typically relatively expensive compared to fixed displacement pumps. In hydraulic systems with a fixed displacement pump driven by an electric motor, the speed of the pump or the motor can be varied to adjust the flow rate. Various control concepts are possible to supply hydraulic systems used in mobile applications to control working equipment with the desired flow rate. For example, flow-matching systems like EFM (Electro-hydraulic Flow Matching) use flow rate or speed control. In systems whose control is based on a pressure or pressure difference, such as LS and LUDV systems (LS: Load-Sensing, LUDV: Load-pressure-independent flow distribution), pressure control is used. Disclosure of the invention According to the invention, a method for determining the setpoints of a control variable for a pressure medium supply system of a hydraulic system (or electro-hydraulic system), as well as a computing unit and a computer program for its execution, and a hydraulic system with the features of the independent claims are proposed. Advantageous embodiments are the subject of the dependent claims and the following description. The method for determining the manipulated variable values for a hydraulic system's pressure supply system uses an inverse plant model. This model takes as input values the values of the controlled state variable of the hydraulic system and time derivatives of that state variable up to a predetermined maximum order, mapping these values to an output value for the manipulated variable. The method comprises determining trajectory values representing the time course of the state variable and derivative values representing time derivatives of the state variable's course up to the maximum order from given setpoint values for the state variable. It also involves determining compensation values using a compensation controller based on the control deviation between the trajectory values and the actual values of the state variable. Finally, it determines the manipulated variable values using the inverse plant model from the trajectory values, the derivative values, and the compensation values. By determining the trajectory for the state variable and using the inverse plant model, feedforward control with low deviations is enabled, in particular reducing undesirable discontinuities in the controlled state variable, which can occur, for example, when the manipulated values are determined directly from the specified setpoints (e.g., with a single controller). The manipulated variable is, for example, the torque to be applied by the electric drive or the rotational speed of the electric drive. The state variable is, for example, a pressure in the hydraulic system, in particular a pressure at a connection of the hydraulic machine or a hydraulic line or channel connected to the connection, a rotational speed of the hydraulic machine, or a volumetric flow rate of hydraulic fluid delivered by the hydraulic machine. In one embodiment, when determining the manipulated variable's values, the derivatives of the time derivative with the maximum order are modified by compensation values to obtain the altered derivatives. The trajectory values, the derivatives of time derivatives with an order smaller than the maximum order, and the modified derivatives are used as inputs to the inverse system model. Specifically, the compensation values are added to the derivatives of the time derivative with the maximum order to determine the altered derivatives. Alternatively, the compensation values can be used to modify the output values of the inverse system model (e.g., by adding them to the output values). In this case, the trajectory values and the derivatives (of all orders) remain unchanged, or at least are not modified by the compensation values, as inputs to the inverse system model. According to one embodiment, a filter whose order equals the maximum order is used to determine the trajectory values and derivative values from the specified setpoints for the state variable. The filter, in particular, comprises a number of series-connected first-order (PT1) filters or is implemented as such, with the number of filters equal to the maximum order. Using a filter is advantageous because it avoids the direct calculation (e.g., by subtraction) of derivatives from