DE102024001777A1 - Method for positioning an actuator - Google Patents

Abstract

2. Method for positioning an actuator (12), in particular in the form of a hydraulic working cylinder (14) which is connected to a hydraulic supply circuit (10) with a pressure supply device (32) in the form of a motor-pump group (34), characterized in that during the movement process of the actuator (12) a theoretical position s (t) _cyl and actual speed v (t) _cyl is calculated by means of the hydraulic transmission ratio between the pump (36) and the ^actuator (12) taking into account the respective current speed n of the motor (M) and that at least this theoretical actual position value serves as an actual value of a position controller for a motor control (FU) of the motor-pump group (34).

Description

The invention relates to a method for positioning an actuator, in particular in the form of a hydraulic working cylinder, which is connected to a hydraulic supply circuit with a pressure supply device in the form of a motor-pump group.

• - Zulaufanschluss einer Zulaufseite für die Versorgung eines am Zulaufanschluss anschließbaren hydraulischen Verbrauchers, insbesondere in Form eines hydraulischen Arbeitszylinders, mit Druckfluid,
• - Ablaufanschluss einer Ablaufseite für das Abführen von Druckfluid aus dem anschließbaren Verbraucher, wobei je nach Ansteuerrichtung dieses Verbrauchers die Zulaufseite sich in die Ablaufseite und die Ablaufseite in die Zulaufseite ändert,
• - Druckversorgungsanschluss, und
• - Rücklaufanschluss, wobei auf die jeweilige
• - Zulaufseite eine Druckregelungseinrichtung und
• - Ablaufseite eine Volumenstromregelungseinrichtung einwirkt.

Through DE 10 2018 001 303 A1 is a valve device known with a

• - Inlet connection of an inlet side for supplying a hydraulic consumer, in particular in the form of a hydraulic working cylinder, which can be connected to the inlet connection, with pressurized fluid,
• - Outlet connection of an outlet side for the discharge of pressurized fluid from the connectable consumer, wherein, depending on the control direction of this consumer, the inlet side changes to the outlet side and the outlet side to the inlet side,
• - Pressure supply connection, and
• - Return connection, whereby the respective
• - Inlet side a pressure regulating device and
• - A volume flow control device acts on the outlet side.

In this way, a kind of decentralized valve control is created with so-called separate control edges, which offer the possibility of separate control of valve elements on the inlet and outlet side of a hydraulic consumer, such as a hydraulic working cylinder, that can be connected to the valve device.

Through DE 10 2020 002 960 A1 A system for braking a displacement-controlled drive system is known, which can be driven for movement by means of an inlet and an outlet pressure on an inlet and outlet side, respectively. In this system, an outlet flow rate of the drive system is controlled by means of an electro-proportional adjustment of at least one valve element such that the outlet pressure is decoupled from the movement of the drive system and can be freely set, while being coupled to the inlet pressure, which can thus be reduced to the level necessary for the movement of the drive system. Because the inlet and outlet pressures can be adjusted electro-proportionally independently of each other, it is possible to set the pressure at the working port associated with the outlet path independently of the pressure at the working port associated with the inlet path.

• - Ermitteln von Messwerten des Proportionalventils während seines Betriebes außerhalb des Fluidsystems;
• - Erstellen eines Kennlinienfeldes basierend auf den Messewerten;
• - Integrieren des Proportionalventils in das Fluidsystem; und
• - Anpassen der Ansteuerung des Proportionalventils an das Fluidsystem, basierend auf dem Kennlinienfeld mittels einer Steuereinrichtung.

Through DE 10 2021 003 236 A1 A method for adapting the control of a proportional valve to its functional operation as part of a fluid system is known, comprising the following steps:

• - Determining measured values of the proportional valve during its operation outside the fluid system;
• - Creating a characteristic curve field based on the measured values;
• - Integrating the proportional valve into the fluid system; and
• - Adapting the control of the proportional valve to the fluid system, based on the characteristic curve field, using a control device.

The aforementioned process steps eliminate the need for costly and time-consuming active adaptation of the proportional valve's control to the fluid system, which includes a hydraulic consumer such as a working cylinder and into which the proportional valve is integrated, in the sense of a learning process by the manufacturer or user of the fluid system.

Based on this prior art, the invention aims to further improve known solutions. A method comprising all the features of claim 1 solves this problem.

By calculating, according to the characterizing part of claim 1, a theoretical position s (t) _cyl and actual speed v (t) _cyl value is calculated during the actuator's movement process using the hydraulic transmission ratio between the pump and the actuator, taking into account the current rotational speed n of the motor, and by using at least this theoretical actual position value as the actual value of a position controller for a motor control of the motor-pump group, this theoretically determined position value can be used as the actual value of the position controller.

The theoretical position value s (t) _cyl is determined according to the following formulas. $$v{\left(t\right)}_{zyl}=\frac{V_{Pumpe}*n{\left(t\right)}_{Motor}*{\mu }_{vol}*10}{A_{zyl}*60}$$ $$s{\left(t\right)}_{zyl}={\displaystyle \int v{\left(t\right)}_{zyl}}dt$$ with
V _pump = delivery volume of the pump
n(t) _Motor = Motor speed
µ _vol = volumetric efficiency
A _zyl = piston area on one piston or rod side of the actuator.

In a further preferred embodiment of the method according to the invention, it is provided that, during initialization, the actuator is moved to at least one of its two end positions by means of a defined setup speed. The detection of this end position is achieved by evaluating the increase of an attributable load pressure. If a predefinable threshold value for the load pressure is exceeded, the motor-pump assembly, which drives the actuator, is stopped in order to subsequently relieve the pressure in the actuator's associated pressure chamber. Alternatively, if the predefinable threshold value for the load pressure is undershot, the motor-pump assembly is stopped again, and the resulting current position of the actuator is defined as the zero point or starting position. In this way, precise positioning of the actuator during operation is enabled.

Preferably, it is further provided that continuous referencing takes place during operation in order to include system and environment-related factors such as temperature, pump wear, oil condition, etc., and to keep the associated trailing error regarding the actual position value of the actuator low.

Preferably, it is further provided that, within the framework of the referencing, a process step "clamping the workpiece" comparable to performing an initialization routine serves as a reference point.

After completion of the function or process step "clamping the workpiece," in which the pressure control has generated a desired clamping pressure, the actuator is actively relieved by the motor-pump group according to a preferred embodiment of the inventive method. When the pressure falls below a predefinable value, the motor-pump group stops, and the resulting current position is stored as a new reference or starting point in the motor control unit, so that any function can subsequently be called up again via the actuator. In this way, the respective cylinder chamber of the actuator is actively relieved by the drive, and when the pressure falls below a defined value, the drive stops, and the current position is stored as a new reference point. Subsequently, any function can be called up again.

This method enables the positioning of an actuator-supported clamping system using a displacement-controlled hydraulic system without a translational absolute encoder. Initially, during the setup phase, and because no information about the actuator's current position is available after the system is switched on, the actuator is moved to one of its two cylinder end positions at a defined setup speed. The respective end position is then detected by evaluating the load increase. If the load exceeds a defined threshold, the drive is stopped, and the system then actively relieves the pressure chamber to a defined setpoint. If the desired pressure is undershot, the drive stops, and the current position is defined as the zero point relative to the actuator's position.

The solution according to the invention also includes a device for carrying out the method described above with the feature configuration of claim 7. Further embodiments of the device according to the invention are the subject of the dependent claims.

• 1 und 2 in der Art von hydraulischen Schaltplänen eine hydraulische Versorgungseinrichtung für einen Aktor, wie einen hydraulischen Arbeitszylinder; und
• 3 und 4 in der Art eines Ablaufplanes das Durchführen einer Initialisierung sowie eines Arbeitszyklus unter Verwendung einer Vorrichtung nach den 1 und 2, wobei der in 3 bei „Initialisiert ja“ rechts abgehende Pfad in Pfeilrichtung auf die linke Eingangsseite „Betriebsbereit“ in 4 ausmündet.

The inventive method is explained in more detail below with reference to a device as shown in the drawing. The drawing is a simplified, not to-scale, representation of the device.

• 1 and 2 in the manner of hydraulic circuit diagrams, a hydraulic supply device for an actuator, such as a hydraulic working cylinder; and
• 3 and 4 in the manner of a flowchart, the execution of an initialization and a work cycle using a device according to the 1 and 2 , wherein the in 3 At "Initialized yes", the path to the right leads in the direction of the arrow to the left entrance page "Ready for operation". 4 leads to...

1 Figure 1 shows a fluidic or hydraulic supply circuit 10 with a hydraulic consumer in the form of an actuator 12, which is designed as a hydraulic differential piston cylinder 14. The differential piston cylinder 14 has a conventional piston-rod unit 16, which separates a piston chamber 18 from a rod chamber 20. Furthermore, the piston-rod unit 16 is longitudinally movable within an actuator housing 22. When the piston-rod unit 16 extends in the direction of the 1 Looking to the right, the volume of the piston chamber 18 increases and, correspondingly, the volume in the rod chamber 20 decreases. During a retraction movement of the unit 16, the corresponding volume ratios for the piston chamber 18 and the rod chamber 20 are reversed.

An electromagnetically actuated 4/2-way valve 24, as shown in the illustration, is used to control the opposing traverse movements of the actuator 12. 1 The actuator is shown in its spring-loaded initial position, in which the piston chamber 18 is connected to a reservoir 28 via fluid lines 26, and the rod chamber 20 is connected to a central fluid supply or pressure supply unit 32 via further fluid lines 30. When the valve 24 is switched, the conditions reverse in the next valve position; that is, the piston chamber 18 is directed towards the discharge side of the central pressure supply unit 32, and the rod chamber 20 is relieved of pressure towards the reservoir 28. In this way, the piston-rod unit 16 moves in and out in opposite directions within the actuator housing 22. These processes are well known, so they will not be described in further detail here.

The central pressure supply unit 32 has a motor-pump group 34 in the usual manner with a hydraulic pump 36, designed in the type of a constant-displacement pump, which takes fluid from the storage tank 28 on the input side and feeds fluid with a predeterminable quantity and pressure into the supply circuit 10 via a supply line 38 on the output side, to which the valve 24 is connected with an inlet carrying fluid or media.

Furthermore, the motor-pump assembly 34 includes a variable-speed electric motor M, which is coupled to the input side of the hydraulic pump 36 via a shaft connection 40. A frequency converter (FC) controls the motor M, receiving input sensor data from a pressure sensor 42 and a speed sensor 44. For pressure measurement, the pressure sensor 42 is connected in the supply line 38 of the working circuit 10, and for speed measurement, the speed sensor 44 measures the rotational speed at the shaft connection 40. Other motor control concepts are conceivable. A pilot-operated pressure relief valve 46 with spring relief, connected to the discharge side of the valve 46 towards the reservoir 28 in the return line, serves to protect the hydraulic supply or working circuit 10. For this function, the pressure relief valve 46 is connected between a junction 48 and the storage tank 28 in the supply circuit 10, with the discharge side of the hydraulic pump 36 opening into the junction 48, as well as one of the other fluid lines 30 along with the associated supply line 38 as part of it. For completeness, it should also be mentioned that the pressure sensor 42, with its pressure-measuring input side, is connected to the supply line 38 via another junction 50.

With the in 1 In the device shown, a method for positioning the actuator 12 can be carried out, in particular in the form of the hydraulic working cylinder 14, which is connected to the hydraulic supply circuit 10 with the central pressure supply device 32 in the form of the motor-pump group 34, wherein during the movement process of the actuator 12, a theoretical position s (t) _cyl and actual speed v (t) _cyl is calculated by means of the ^hydraulic transmission ratio between the pump or hydraulic pump 36 and the actuator 12, taking into account the respective current speed n of the motor M, wherein at least this theoretical actual position value serves as the actual value of a position controller for the motor control FU of the motor-pump group 34.

After the theoretical position value s(t) _cyl can be determined according to the formulas given above, the actuator 12 is moved to at least one of its two end positions 52, 54 by means of a defined setup speed during initialization for the position method. One end position 52 is formed by housing parts of the actuator housing 22, against which the piston of the piston-rod unit 16 abuts with its free end face, whereas the other or further end position 54 is formed by further housing parts of the actuator housing 22, against which the piston abuts on the rod side in its maximum deflected position. The method according to the invention does not necessarily require that the end positions 52, 54 are actually reached by the piston-rod unit 16; Rather, it suffices to move to the relevant positions, the detection of which is achieved by evaluating the increase of an attributable load pressure. If a predefinable threshold value for the load pressure is exceeded, the motor-pump group 34, which drives the actuator 12, is stopped in order to subsequently relieve the pressure in the associated pressure chamber 18 or 20 of the actuator 12. If the predefinable threshold value for the load pressure is undershot, the motor-pump group 34 is stopped again, and the corresponding current position of the actuator 12 is defined or referenced as the zero point or initial position.

The individual initialization steps associated with this, as well as the resulting process cycle, are described in 3 The process is illustrated using flowcharts, so the individual steps will not be discussed in detail here. It is understood that the evaluation steps mentioned, as well as the sensor data acquisition, take place over at least [number of days/weeks]. A computer unit (CPU) is used, which is an integral part of the motor control unit (FU).

Another device for realizing the method according to the invention is in 2 shown, whereby the corresponding solution is only explained insofar as it differs significantly from the embodiment according to the 1 differs in the embodiment according to the 2 The 4/2-way valve 24 is thus eliminated, and the alternating supply of the piston chamber 18 and rod chamber 20 of the actuator 12 is achieved via a fluid pump 36, which, in reversing mode, can feed fluid at a predetermined pressure in both directions into the associated supply lines 38 connected to the piston chamber 18 and the rod chamber 20. To implement a closed-loop system, a hydraulic accumulator 56 is connected to the supply circuit 10. This accumulator compensates for any missing volume during the oscillating operation of the actuator 12 and, when the pressure relief valve 46 is activated, is supplied with fluid at a predetermined pressure from the lines 38 on its inlet side.

To monitor the pressure at actuator 12, two pressure sensors 42 are connected in the supply circuit 10, one facing the piston chamber 18 and the other the rod chamber 20. On the output side, the two pressure sensors 42 supply their sensor data, in the form of pressure values, to the motor control unit (FU) of the motor-pump group 34. Furthermore, the hydraulic accumulator 56 can be supplied with fluid at a predefined pressure, provided that a controllable check valve 58 opens and then, in the direction of view towards the 2 The hydraulic pump 36 transfers the supply fluid from the left supply line 38 to the fluid supply line 60 of the storage tank 56, whereby the hydraulic pump 36 is directly supplied with circulating fluid, bypassing the storage tank 28. A control line 62, connected to the right supply line 38, which leads to the rod chamber 20 of the actuator 12, serves to actuate the check valve 58. If the fluid pressure is [missing information] in the direction of view of the 2 As seen in the right supply line 38 higher than in the left, the check valve 58 opens and establishes a fluid-carrying connection between the left fluid supply line 38 and the fluid supply line 60.

Ten additional spring-loaded check valves 64 connected in the supply circuit prevent unwanted backflow of fluid in the opposite direction to the actual supply direction. Thus, looking towards the 2 The pressure relief valve 46 is protected against backflow on the inlet side by the two upper spring-loaded check valves 64, so that the pressure relief valve 46 receives its fluid on the inlet side exclusively via the respective supply line 38, provided that the corresponding response pressure is above the preset actuation pressure of the respective check valve 64 of the upper pair. The further spring-loaded check valve 64 opens towards the right supply line 38 with one outlet of the fluid or hydraulic pump 36 as soon as the pressure in the fluid supply line 60 is greater than in the aforementioned right supply line 38. Instead of a differential cylinder as actuator 12, a synchronous cylinder (not shown) or a correspondingly designed hydraulic motor (also not shown) can also be used.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 10 2018 001 303 A1 [0002]
• DE 10 2020 002 960 A1 [0004]
• DE 10 2021 003 236 A1 [0005]

Claims (10)

Method for positioning an actuator (12), in particular in the form of a hydraulic working cylinder (14) which is connected to a hydraulic supply circuit (10) with a pressure supply device (32) in the form of a motor-pump group (34), characterized in that during the movement process of the actuator (12) a theoretical position s (t) _cyl and actual speed v (t) ^cyl is calculated by means of the hydraulic transmission ratio between the pump (36) and the _actuator (12) taking into account the respective current speed n of the motor (M) and that at least this theoretical actual position value serves as an actual value of a position controller for a motor control (FU) of the motor-pump group (34). Procedure according to Claim 1 , characterized in that the theoretical position value s (t) _cyl is determined according to the following formulas $$v{\left(t\right)}_{zyl}=\frac{V_{Pumpe}*n{\left(t\right)}_{Motor}*{\mu }_{vol}*10}{A_{zyl}*60}$$ $$s{\left(t\right)}_{zyl}={\displaystyle \int v{\left(t\right)}_{zyl}}dt$$ with V _pump = delivery volume of the pump n(t) _motor = speed of the motor µ _pre = volumetric efficiency A _cyll = piston area on one piston or rod side of the actuator. Procedure according to Claim 1 or 2 , characterized in that, during initialization, the actuator (12) is moved to at least one of its two end positions (52, 54) by means of a defined setup speed, the detection of which is carried out by means of an evaluation of the increase of an attributable load pressure, and that if a predefinable threshold value is exceeded with respect to the load pressure, the motor-pump group (34) is stopped as a drive for the actuator (12) in order to subsequently relieve an associated pressure chamber (18, 20) of the actuator (12), and/or that if the predefinable threshold value with respect to the load pressure is undershot, the motor-pump group (34) stops again, and the associated current position of the actuator (12) is defined as the zero point or starting position. Method according to one of the preceding claims, characterized in that , in order to include system and environment-related factors and to keep a related following error concerning the actual position value of the actuator (12) low, continuous referencing is performed during operation. Method according to one of the preceding claims, characterized in that, within the framework of referencing, a process step “clamping the workpiece” is used as a reference or starting point within the method. Method according to one of the preceding claims, characterized in that after the process step "clamping the workpiece", in which the pressure control has generated a desired clamping pressure, the actuator (12) is actively relieved by the motor-pump group (34) and that if a predefinable pressure value is undershot, the motor-pump group (34) stops and the associated current position is stored as a new reference or starting point in the motor control (VFD) in such a way that any function can subsequently be called up again via the actuator (12). Device for carrying out a method according to one of the preceding claims, characterized in that at least one actuator (12) is provided which is connected to a hydraulic supply circuit (10) with a motor-pump group (34) and with at least one pressure sensor (42) at least on an actuation side (18, 20) of the actuator (12), which transmits its measured value data to a motor control (FU) which specifies the pump power for the hydraulic supply circuit (10) via the speed n of the motor (M). Device according to Claim 7 , characterized in that the actuator (12) is formed from a differential piston cylinder (14) or a synchronous cylinder. Device according to Claim 7 or 8 , characterized in that the motor-pump group (34) has at least one constant-speed pump which operates in one pumping direction ( 1 ) or in reverse mode ( 2 ) feeds fluid into the associated supply circuit (10) in both opposing pump directions. device according to one of the Claims 7 until 9 , characterized in that the hydraulic supply circuit (10) when using a pump (36) with only one delivery direction has a valve control device (24) for reversing the actuator (12).