Method for adjusting a pressure medium supply for at least one hydraulic actuator, and hydraulic system

Abstract

The present invention relates to a method for adjusting a pressure medium supply for at least one hydraulic actuator (1), wherein the actuator (1) is supplied with a pressure medium by a displacement unit (2) adjustable in its displacement volume, the displacement unit (2) is driven by a variable-speed drive (3) and a quantity of pressure medium to be supplied to the actuator is predetermined by a size profile (4), wherein a speed setpoint value of the drive (3) and / or a setpoint value for the displacement volume of the displacement unit (2) is set taking into account a knowledge-based decision system. The invention also relates to a hydraulic system.

Description

[0001] Method for adjusting a pressure medium supply for at least one hydraulic actuator and hydraulic system

[0002] Description

[0003] The present invention relates to a method for adjusting a pressure medium supply for at least one hydraulic actuator and a hydraulic system which comprises at least one hydraulic actuator.

[0004] The hydraulic system comprises, in particular, a displacement unit with adjustable displacement volume that supplies the hydraulic actuator with a pressure medium, a variable-speed drive that drives the displacement unit, and a control system for adjusting the displacement volume of the displacement unit and the speed of the drive. Accordingly, the method provides that the actuator is supplied with a pressure medium by a displacement unit with adjustable displacement volume, the displacement unit is driven by a variable-speed drive, and the amount of pressure medium to be supplied to the actuator is specified by a size profile.

[0005] In such hydraulic systems, a cyclically repeating variable profile is specified for the states to be assumed by the hydraulic actuator. For example, a time-dependent displacement profile (or position profile) to be assumed by the hydraulic actuator is specified. Alternatively or additionally, a force profile can also be specified.

[0006] To achieve the specified size profile, the volume flow and / or the discharge pressure can be adjusted over time by adjusting the displacement volume of the adjustable displacement unit and / or the drive speed. Since the delivery system, consisting of an adjustable displacement unit and a variable-speed drive, has two degrees of freedom that can be adjusted with a control system, it has proven difficult in practice to operate the hydraulic system optimally.

[0007] In order to improve energy consumption, DE 10 2013 006 137 A1 proposes integrating a model-based optimization problem into the control system for setting the speed setpoint and the setpoint for the displacement volume, for which purpose an objective function for the process sequence is specified. However, such an optimization problem also requires that, in addition to the size profile, further system parameters be incorporated. The object of the present invention is therefore to eliminate the disadvantages explained with reference to the prior art and, in particular, to provide a method for adjusting a pressure medium supply and a hydraulic system with which properties such as, for example, energy consumption and / or the dynamic behavior of a hydraulic system can be improved in an alternative manner, wherein commissioning is also to be simplified in particular.

[0008] A solution to this problem is provided by the method and the hydraulic system with the features of the respective independent claim. Possible further solutions and advantageous developments are specified in the above and following descriptions as well as in the dependent claims, whereby individual features of the advantageous developments can be combined with one another in a technically expedient manner.

[0009] The problem is solved in particular by setting a setpoint speed of the drive and / or a setpoint for the displacement volume of the displacement unit, taking into account a knowledge-based decision system. Preferably, both the setpoint speed of the drive and the setpoint for the displacement volume are set taking into account the knowledge-based decision system. The knowledge-based decision system can be implemented, for example, as fuzzy logic or a neural network.

[0010] Accordingly, it is also proposed that the control of the hydraulic system includes a knowledge-based decision system.

[0011] In other words, the basic idea of ​​the invention is that, instead of a specific optimization problem, an improvement in system behavior (energy consumption, dynamic behavior) is achieved based on a knowledge-based decision system (e.g., fuzzy logic, neural network). When using fuzzy logic, input variables of the fuzzy logic are assigned to a set based on their degree of membership. Operations (fuzzy rules) are executed in the fuzzy logic that lead to specific values ​​or sets of values, on the basis of which the next cycle is executed. The membership functions and the fuzzy rules are based on expert knowledge, which in turn can be based on component knowledge, simulations, empirical values, or experiments.Thus, once a knowledge-based decision system has been set up, it can optimize the speed of the drive and the displacement volume of the displacement unit when the specified size profile changes, in particular so that less energy is consumed for a cycle or the dynamic behavior is improved during critical processes in the cycle.

[0012] For this purpose, the cycle specified by the size profile can be divided by the knowledge-based decision system into various sequentially arranged segments, which differ from one another in particular by a change in at least one state variable of the size profile. The knowledge-based decision system preferably optimizes the speed and the displacement volume for each segment of the cycle. In the subsequent cycle, the speed (or, if applicable, the different speeds of the multiple segments) and the displacement volume (or, if applicable, the different displacement volumes of the multiple segments) are changed, taking into account the initial values ​​of the knowledge-based decision system, and further optimized for the next cycle, taking into account the energy consumed in the cycle.In a preferred embodiment, a closed control loop is designed to adjust the displacement volume, so that the displacement volume is adjusted within a closed control loop. For example, based on the specified size profile, the displacement volume is changed within a cycle using a closed control loop according to the requirements of the size profile.

[0013] However, it is preferably provided that the knowledge-based decision system is configured to provide a manipulated variable for adjusting the speed of the drive. Thus, a discrete output variable or a discrete set of output variables provided by the knowledge-based decision system is used as the manipulated variable for adjusting the speed of the drive. A discrete output variable exists, for example, when the knowledge-based decision system specifies exactly one value for the speed of the drive during an entire cycle. A discrete set of output variables exists when the knowledge-based decision system specifies several different speed variables for a cycle for the drive.It can therefore be provided that the speed of the drive is set exclusively taking into account the knowledge-based decision system, while the displacement volume of the displacement unit is also set in a closed control loop, possibly without taking into account a specification by the knowledge-based decision system.

[0014] In an advantageous embodiment, however, it is provided that the knowledge-based decision system is configured to provide a pilot control variable for the manipulated variable for adjusting the displacement volume. In this case, a discrete output variable (if the displacement volume is constant over a cycle) or a discrete set of output variables (if the displacement volume of the displacement unit changes over a cycle) is fed to the knowledge-based decision system as a pilot control variable for the manipulated variable for adjusting the displacement volume. Alternatively, it can be provided that the displacement volume is also controlled solely taking into account the knowledge-based decision system. The correction value of the displacement volume provided by the knowledge-based decision system as a pilot control value thus serves to further optimize energy consumption.

[0015] The parameters of a cycle are fed into the knowledge-based decision system as input variables. For example, the speed or speeds set during a cycle can be fed into the knowledge-based decision system as input variables. Furthermore, the displacement volume set during a cycle or the various displacement volumes set during a cycle can be fed into the knowledge-based decision system. In addition, the process variables such as displacement and force can be fed into the knowledge-based decision system. Finally, the energy consumed during a cycle (for example, the electrical energy supplied to the drive and, if applicable, also to the displacement unit) is also fed into the system. The discrete input variables can, for example, when using a fuzzy algorithm, be assigned to a fuzzy set with a certain degree based on a membership function.The operations (fuzzy rules) of fuzzy logic are specifically designed to optimize a value, sometimes referred to as a reference value, for a cycle. The operations of fuzzy logic are specifically designed to optimize the output variables provided by the fuzzy logic and / or improve the dynamic behavior of a cycle.

[0016] When implementing a knowledge-based decision system using fuzzy logic, both the assignment of input variables to the fuzzy set and the fuzzy rules of fuzzy logic are based on expert knowledge, derived primarily from component knowledge, simulations, empirical values, and experiments. Fuzzy logic is well-known in its own right, so the specific implementation of fuzzy logic will not be discussed further here.

[0017] The displacement unit is preferably operated as a motor or a positive displacement pump. The displacement unit, which can be adjusted in its displacement volume, can be designed, for example, as a radial piston or axial piston machine. The variable-speed drive is usually an electric motor.

[0018] The invention and the technical environment are explained below using the figure as an example.

[0019] The figure shows a hydraulic system comprising an actuator 1, a displacement unit 2 with an adjustable working volume, and a variable-speed drive 3 that drives the displacement unit 2. The amount of pressure medium to be delivered to the actuator 1 can be adjusted by setting a setpoint speed of the drive 3 and by setting the displacement volume of the displacement unit 2.

[0020] The hydraulic system also includes a closed-loop control system. A closed-loop control system 6 is provided, which includes a position measuring system for the actuator 1. The closed-loop control system 6 also includes a controller 7, by means of which the displacement volume of the displacement unit 2 is adjusted. The control system also includes a knowledge-based decision system 5, whose output variables are transferred to a control system 8. The knowledge-based decision system 5 also receives the process parameters, such as speed, displacement volume, and energy consumption of the drive 3, as input variables. In the specific embodiment shown, the knowledge-based decision system 5 is designed as a fuzzy logic / algorithm. Alternatively, the knowledge-based decision system 5 can be designed as a neural network.

[0021] A variable profile 4 (for example, a force profile and / or a position profile) is specified for the hydraulic system, which is to be cyclically traversed by the actuator 1. The variable profile 4 is fed to both the controller 7 and the pilot control 8.

[0022] The process variables recorded in an identification cycle are fed to the knowledge-based decision system 5, whereby these input variables are assigned to fuzzy sets 9 with a degree of membership when the knowledge-based decision system is designed as fuzzy logic. Based on the fuzzy sets 9 thus defined, an operation (fuzzy rules 10) is performed, resulting in discrete output variables 11. These output variables 11 are fed to the feedforward control 8, whereby the value for the speed of the drive 3 is fed to the drive 3 as a manipulated variable. The value for the change in the displacement volume is fed to the manipulated variable of the controller 7 for adjusting the displacement volume.

[0023] The assignment of the input variables to the fuzzy sets 9 and the fuzzy rules 10 are set up on the basis of expert knowledge in such a way that, on the basis of the input values ​​recorded during a cycle, the speed and / or the displacement volume are optimized for the next cycle in such a way that the lowest possible energy consumption is achieved and / or the dynamic behavior is improved during critical processes in the cycle.

[0024] List of reference symbols

[0025] Actuator

[0026] Displacement unit

[0027] drive

[0028] Size profile

[0029] Knowledge-based decision system closed control loop

[0030] Controller

[0031] Feedforward control

[0032] Fuzzy sets

[0033] Fuzzy rules

[0034] Output variable

Claims

Claims 1. Method for adjusting a pressure medium supply for at least one hydraulic actuator (1), wherein the actuator (1) is supplied with a pressure medium by a displacement unit (2) adjustable in its displacement volume, the displacement unit (2) is driven by a variable-speed drive (3) and a quantity of pressure medium to be supplied to the actuator is predetermined by a size profile (4), characterized in that a speed setpoint of the drive (3) and / or a setpoint for the displacement volume of the displacement unit (2) is set taking into account a knowledge-based decision system.

2. Method according to claim 1, wherein the adjustment of the displacement volume takes place in a closed control loop (6).

3. Method according to one of the preceding claims, wherein a discrete output variable (11) or a discrete output variable set (11) of the knowledge-based decision system is supplied as a pilot control variable of the manipulated variable for adjusting the displacement volume.

4. Method according to one of the preceding claims, wherein a discrete output variable (11) or a discrete set of output variables (11) is used by the knowledge-based decision system as a manipulated variable for adjusting the speed of the drive.

5. Method according to one of the preceding claims, wherein cycle parameters are supplied to the knowledge-based decision system as input variables.

6. The method according to claim 5, wherein the knowledge-based decision system is designed as fuzzy logic and the input variables are fed to fuzzy rules (9) after an evaluation as a fuzzy set.

7. Method according to one of the preceding claims, wherein the size profile (4) is fed to the knowledge-based decision system as an input variable.

8. Method according to one of the preceding claims, wherein the knowledge-based decision system is configured to optimize a cycle.

9. The method according to claim 8, wherein the optimized cycle is predetermined by a minimum energy consumption.

10. Method according to one of the preceding claims, wherein the knowledge-based decision system is designed as fuzzy logic or as a neural network.

11. Method according to one of the preceding claims, wherein the knowledge-based decision system is designed as fuzzy logic and expert knowledge is used to establish fuzzy rules of the fuzzy logic.

12. Hydraulic system, comprising at least one hydraulic actuator (1), a displacement unit (2) adjustable in its displacement volume, which supplies the actuator (1) with a pressure medium, a variable-speed drive (3) which drives the displacement unit (2), and a control system for adjusting the displacement volume of the displacement unit (2) and the speed of the drive, characterized in that the control system comprises a knowledge-based decision system (5).

13. Hydraulic system according to claim 12, wherein a closed control loop (6) is formed for adjusting the displacement volume.

14. Hydraulic system according to claim 12 or 13, wherein the knowledge-based decision system (5) is arranged to provide a manipulated variable for adjusting the speed of the drive (3).

15. Hydraulic system according to one of claims 12 to 14, wherein the knowledge-based decision system (5) is arranged to provide a pilot control variable of the manipulated variable for adjusting the displacement volume.

16. Hydraulic system according to one of claims 12 to 15, wherein the control is arranged to carry out the method according to one of claims 1 to 10.

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