DE102023000817A1 - Method for controlling a fluidic actuator and device for carrying out the method - Google Patents

Abstract

2. Method for controlling a fluidic actuator (10) with at least the following steps:- carrying out an initialization to determine at least one defined end position (x, y) in a direction of movement of the actuator (10), and then- carrying out a position control on the basis of a virtual braking point for the actuator (10) associated with the end position (x, y),- decelerating the speed of the actuator (10) at the braking point until the subsequent end position (x, y) in the direction of movement is reached; and- reversing the actuator (10) in the opposite direction of movement.

Description

The invention relates to a method for controlling a fluidic actuator and a device for carrying out the method.

Through EP 2 610 490 B1 a hydraulic drive is known with a quantity and/or pressure control for a pressure intensifier of a high-pressure device, consisting essentially of a motor drive with a pump for a pressure medium and a control system, wherein a constant flow pump or a pump which delivers a constant volume per revolution is used as the hydraulic drive. The hydraulic drive is driven by a servo motor which can be electrically controlled, regulated and/or switched by means on the low-pressure side and/or high-pressure side. The advantage of this solution is that there is essentially no pulsation when a high-pressure medium is introduced into a filler or no flaking of brittle materials during water jet cutting. Furthermore, pressure fluctuations, especially when switching a cutting valve on and off, are kept to a minimum by using the hydraulic drive, which largely prevents overloading of components.

In the specific embodiment, the low- and/or high-pressure side means referred to are pressure sensors which, when inserted into assignable fluid lines, detect the pressure prevailing there and transmit it as an electrical output variable to an electrical control system for operating the pump's servo motor.

Based on this prior art, the invention is based on the object of creating an improved solution. This object is achieved by a method with the features of patent claim 1 and a device with the features of patent claim 8.

• - Durchführen einer Initialisierung zum Ermitteln mindestens einer definierten Endlage in einer Bewegungsrichtung des Aktors, und anschließendem
• - Durchführen einer Positionsregelung auf der Grundlage eines zur Endlage zugehörigen virtuellen Bremspunktes für den Aktor,
• - Verzögern der Geschwindigkeit des Aktors im Bremspunkt bis zum Erreichen der in Bewegungsrichtung nachfolgenden Endlage; und
• - Umsteuern des Aktors in die entgegengesetzte Bewegungsrichtung.

The method according to the invention for controlling a fluidic actuator is characterized by at least the following method steps:

• - Performing an initialization to determine at least one defined end position in a direction of movement of the actuator, and then
• - Carrying out a position control based on a virtual braking point for the actuator associated with the end position,
• - Deceleration of the speed of the actuator at the braking point until the end position following in the direction of movement is reached; and
• - Reversing the actuator in the opposite direction of movement.

This prevents the actuator from hitting the respective end position at maximum speed, which is usually formed by the front sides of the associated actuator housing. Instead, a position control is used to approach a predeterminable virtual braking point, preferably at maximum speed, and when the braking point is reached, the actuator speed is then slowed down so that it reaches the end position at a significantly slower speed without causing damage to the actuator and its housing. Since the actuator is intended to ensure the delivery of fluid under high pressure to a consumer in both opposing actuation directions as part of a pressure transmission, after reaching one end position the actuator is redirected to the opposite direction of movement in order to reach the opposite end position. If the method and the associated device are used in the area of hydrogen delivery points, such as hydrogen filling stations, the hydrogen is compressed to a high pressure of 700 to 900 bar before being delivered to the vehicle to be refueled.

• - Ansteuern des Aktors mittels eines Antriebes in einer Bewegungsrichtung bis eine von seinen beiden möglichen Endlagen erreicht ist,
• - Erkennen der jeweiligen Endlage mittels einer Sensoreinrichtung,
• - Referenzieren der einen Endlage als Null- oder Ausgangspunkt,
• - Ansteuern des Aktors in die entgegengesetzte Bewegungsrichtung, um die weitere Endlage zu detektieren,
• - Ermitteln von theoretischen Positions- und Geschwindigkeitsistwerten während des Bewegungsvorganges des Aktors zwischen den beiden Endlagen,
• - Abschalten des Antriebes bei Erreichen der weiteren Endlage, und
• - Abspeichern des aktuellen Positionswertes in der jeweiligen Endlage.

Before carrying out the actual cyclic process sequence using position control within the framework of high-pressure compression, an initialization routine is necessary, which is characterized by at least the following initialization steps:

• - Controlling the actuator by means of a drive in one direction of movement until one of its two possible end positions is reached,
• - Detection of the respective end position by means of a sensor device,
• - Referencing one end position as zero or starting point,
• - Controlling the actuator in the opposite direction of movement to detect the further end position,
• - Determination of theoretical position and speed actual values during the movement of the actuator between the two end positions,
• - Switching off the drive when the further end position is reached, and
• - Saving the current position value in the respective end position.

Due to the fact that there is no information about the current position of the actuator after the device or system is switched on, it is initially moved to one of the two end positions at a defined setup speed. The end position is detected by means of an assignable proximity switch, which is preferably arranged stationary on the actuator housing. Proximity switches of this type, also known as proximity initiators, are sensors that react to approach without contact, i.e. without direct contact, for example with the moving parts of the actuator or with the fluid used.

If one of the two end positions is reached by means of the actuator, this reference point is defined as the zero point. This is followed by a movement in the opposite direction to detect the second end point or end position. During the movement process, a theoretical position and speed actual value is calculated using the hydraulic transmission ratio between the pump and actuator and the knowledge of the current speed values. When the end position is reached, the drive is switched off and the calculated current position is saved as the maximum end position. This completes the initialization routine and a cyclical movement sequence can be started.

• - Übernahme des jeweils abgespeicherten aktuellen Positionswertes aus der Initialisierung,
• - Berechnung eines virtuellen Bremspunktes, um in kürzester Zeit die zugehörige Endlage zu erreichen,
• - Verfahren des Aktors, vorzugsweise mit vorgebbarer Maximalgeschwindigkeit, bis zum
• - Erreichen des virtuellen Bremspunktes mit anschließender Reduzierung auf eine vorgebbare Zielgeschwindigkeit bis der Aktor die zugehörige Endlage abschließend erreicht hat,
• - Abschalten des Antriebes nebst vorzugsweise Abspeichern der aktuellen Position, und
• - Berechnen des Bremspunktes für die entgegengesetzte Bewegungsrichtung.

In this case, position control is used as an adaptive position control, which is characterized by at least the following steps:

• - Adoption of the current position value saved from the initialization,
• - Calculation of a virtual braking point in order to reach the corresponding end position in the shortest possible time,
• - Movement of the actuator, preferably with a preset maximum speed, until
• - Reaching the virtual braking point with subsequent reduction to a predefined target speed until the actuator has finally reached the corresponding end position,
• - Switching off the drive and preferably saving the current position, and
• - Calculate the braking point for the opposite direction of movement.

If the initialization routine has been successfully completed as described, the cyclic operation of the application begins with the storage of the current position of the actuator and the calculation of the braking point in order to reach the end point in the shortest possible time. This significantly improves efficiency. The calculated distance to initiate the braking process depends on several factors: deceleration of the drive, maximum speed, distance between the end points and a freely selectable factor to make manual adjustments to the process. The system then moves at a specified maximum speed. As soon as the virtual braking point is reached, the drive unit decelerates to a second specified target speed until the hydraulic actuator has reached the end point. The drive then switches off and again stores the current position and calculates the braking point for the opposite direction of movement. A movement profile follows as described above. This cycle can be repeated as often as required. Due to the recurring storage of the end positions and the respective calculation of the braking point, system and environmental factors are also taken into account. Examples of this include: temperature, pump wear and oil condition. Overall, an adaptive position control for a closed hydraulic axis is created, in the form of the actuator, without a position measuring system.

The invention further relates to a device for carrying out the method described above, wherein the actuator has a hydraulic working cylinder, preferably in the form of a synchronous cylinder. Furthermore, a proximity switch on the housing side determines the end position of the piston-rod unit of the hydraulic working cylinder in question. In contrast to the known displacement measuring devices, the proximity switch responds directly to the end position of the actuator without hysteresis processes occurring that could impair the timely transmission of the sensor measurement. A proximity switch also operates essentially wear-free compared to displacement measuring systems with their assignable, movable components.

Particularly preferably, a hydraulic pump is used to drive the actuator, preferably in the form of a reversible pump which drives the piston-rod unit in both opposite directions of movement, the hydraulic pump and the actuator together forming a closed hydraulic supply circuit so that any leakage losses that may occur are avoided.

Preferably, it is also provided that the piston-rod unit with its two rods drives an independent gas compressor, which alternately sucks in gas in the low-pressure range and delivers it to a consumer in a highly compressed form. Alternatively, it is also possible to initiate the gas compression directly via the actuator.

• 1 in der Art eines hydraulischen Schaltplans die wesentlichen Komponenten einer Vorrichtung zum Durchführen eines Verfahrens gemäß Ablaufdiagramm nach der 2, und
• 2 in der Art eines Ablaufdiagrammes die wesentlichen Verfahrensschritte des erfindungsgenmäßen Verfahrens.

In the following, the method according to the invention and the device are described using an example example according to the drawing. The diagrams show the basic and not to scale representation of the

• 1 in the form of a hydraulic circuit diagram, the essential components of a device for carrying out a method according to the flow chart according to the 2 , and
• 2 in the form of a flow chart, the essential process steps of the process according to the invention.

1 shows the essential components of the device according to the invention in the form of a conventional hydraulic circuit diagram. The device has an actuator 10 in the form of a hydraulic working cylinder, which is designed as a so-called synchronous cylinder. A synchronous cylinder, which is also called a synchronous cylinder, has a piston rod 14 on each side of a centrally arranged piston 12, so that a total of one piston-rod unit 16 of the actuator 10 is formed with two piston rods 14. The volume of the incoming and outgoing hydraulic oil is therefore always the same and thus the piston-rod unit 16 also moves in and out at the same speed in both directions. The piston-rod unit 16 in the starting position of the actuator 10, as in 1 shown, divides two equally sized cylinder chambers 20 within an actuator housing 18. Depending on the application, however, it is certainly possible to change the volume of the cylinder chambers 20 in the initial position by choosing different rod and/or piston cross-sections, for example to design one cylinder chamber with a larger volume than the other cylinder chamber.

The two free ends of the respective piston rod 14 lead out of the associated actuator housing 18 and are each operatively connected to an associated compressor piston 22, which is part of a gas compressor 24. The two compressor pistons 22 correspond in terms of their geometric design to the piston 12 of the actuator 10. The two gas compressors 24 are also constructed in the same way. The respective gas compressor 24 extracts gas, for example hydrogen gas, from the inlet side from a low-pressure line 26 with the check valve 28 then open. Furthermore, the respective gas compressor 24 is connected on the outlet side to a high-pressure line 30, which leads to a consumer, for example in the form of a (motor) vehicle to be refueled with hydrogen. The respective additional check valve 32 is then opened for the delivery to the high-pressure side 30.

A compressor cycle can now run as follows. Moving in the direction of the 1 When the piston 12 of the actuator 10 moves to the right, into the first or front end position x, it takes the two compressor pistons 22 with it in the same direction via the respective piston rod 14. This increases the inflow volume on the inflow side of the left gas compressor 24 and the gas is fed accordingly via the open left check valve 28. On the other side, the compressor piston 22 simultaneously compresses the gas taken up in the right gas compressor 24 in the previous cycle and, with the right check valve 28 closed, pushes the highly compressed gas quantity out into the high-pressure line 30 via the additional right check valve 32 when the additional left check valve 32 is closed.

After the right end position for the piston 12 of the piston-rod unit 16 is reached, the actuator 10 is switched and the piston 12 moves from its right end position in the opposite direction, and thus into the left, rear or second end position y. The gas previously taken in during the inflow process is now compressed in the left gas compressor 24 and delivered to the high-pressure line 30 via the left additional check valve 32 with the left check valve 28 closed. The right check valve 28 also opens and gas flows from the low-pressure line 26 into the increasingly expanding gas space of the right gas compressor 24 as its compressor piston 22 is moved from right to left. The right additional check valve 32 is therefore closed. After the left end position for the piston 12 is reached, the direction is reversed and the loading and unloading cycle for the two gas compressors 24 is repeated as described.

The two cylinder chambers 20 of the actuator 10 are each connected to a supply line 34, 36, which can be supplied with fluid of a predefined pressure by a hydraulic pump 38 in the form of a reversing pump. In particular, the reversing pump 38 is able to alternately push fluid back and forth between the two supply lines 34, 36 in order to alternately move the piston-rod unit 16 of the actuator 10 back and forth. Since the amount of fluid is alternately pushed from one cylinder chamber 20 via the supply lines 34, 36 into the other cylinder chamber 20 at a constant rate, depending on the direction of rotation of the reversing pump 38, the corresponding drive for the actuator 10 essentially manages with a constant amount of fluid. In this respect, the hydraulic pump in the form of the reversing pump 38 together with the actuator 10 and the supply lines 34, 36 forms a closed hydraulic supply circuit 40.

The drive for the hydraulic or reversing pump 38 is an electric motor M which can be controlled by means of a control system 42 and which, with regard to its controllability in the 1 is symbolically provided with an arrow representation. The controller 42 receives on the input side the sensor data of two proximity switches 44, which in the present case are each arranged at the end of the actuator housing 18 and thus monitor the position of the piston 12 as soon as it hits the adjacent front end in the actuator housing 18. In addition to proximity switches, conventional limit switches can also be used, which can detect the end position of the piston 12 in the actuator housing 18 and pass it on to the controller 42. As soon as a limit or proximity switch 44 detects an end position of the piston 12, it informs the controller 42, which then controls the electric motor M in such a way that the reversing pump 38 conveys fluid in the other direction, so that the piston 12 can assume an opposite direction of movement until it hits its opposite end position within the actuator housing 18.

Two valves 46, 48 are used to empty the hydraulic supply circuit 40; when switched accordingly, they establish a fluid-carrying connection between the respective supply line 36, 38 and a storage tank T. The two valves 46 and 48 serve as discharge valves in combination with the additional supply device 50 to regulate the thermal balance of the hydraulic oil. A defined amount of oil is thus discharged when the cylinder is extended and retracted, and fresh oil from the supply device 50 is fed back into the closed circuit. Valve 48 is opened when extending, valve 46 is opened when retracting. The opposite side is closed accordingly. Furthermore, an additional supply device 50 is optionally provided, consisting of a conventional motor-pump unit 52, wherein the output side of the associated hydraulic pump is protected from the tank side with the storage tank T via a pressure relief valve 54. Downstream in the direction of flow, a spring-loaded check valve 56 is provided which opens in the direction of a fluid filter 58 and closes in the opposite direction. The fluid or hydraulic filter 58 is connected on the output side to a branch point 60 which opens into a connecting line 62 between the two supply lines 34, 36 on the output side of the reversing pump 38, with further spring-loaded check valves 64 being arranged towards both supply lines 34, 36, which open in the direction of the respective supply line 34, 36 and close in the opposite direction in order to prevent an unwanted backflow of fluid from the supply lines 34, 36 in the direction of the filter 58.

All essential fluid components mentioned are as shown in the 1 in a dashed frame 66. The device in question does not require low- and/or high-pressure side detection means, such as pressure sensors used in the fluid lines. Instead, the use of proximity switches 44 allows trouble-free monitoring of the actuator piston 12. Since the proximity switches 44 detect the operating situation of the actuator 10 without contact, there are no measurement transmission errors due to the use of transmission media such as a fluid. Hysteresis-prone displacement measuring systems can also be dispensed with during transmission, which are also subject to wear, which is not the case with the proximity switches 44.

In the following, the flow chart is used to 2 , the operation of a device according to the 1 explained in more detail.

After commissioning or starting the device by switching it on, a check is carried out to see whether initialization has already taken place or not. If the system is not initialized, an initialization routine is called. This is in 2 (Continued). The actuator is moved to one of its two end positions x, y at a defined setup speed, for example to a front, first end position x. If the front end position x has not yet been reached, which can be checked with one of the two proximity switches 44, the routine is repeated, i.e. the piston-rod unit 16 of the actuator 10 continues to extend until the front x end position is reached, which the assignable proximity switch 44 detects and forwards to the controller 42.

The control 42 then stops the electric motor M, which in turn stops the hydraulic or reversing pump 38. If one of the two end positions, front x or rear y end position, is reached, this reference point is defined as the zero point by the control 42. The rear, second end position y can therefore also be saved as the zero reference point. If referencing to zero has been successfully completed, the relevant routine does not need to be repeated; instead, the piston-rod unit 16 is retracted with respect to the stationary actuator housing 18 at a predeterminable setup speed and a movement in the opposite direction takes place in order to detect the second end point or end position y.

$$s{\left(t\right)}_{zyl}={\displaystyle \int v{\left(t\right)}_{zyl}}dt,$$

mit

v(t)zyl =

Geschwindigkeit des Kolbens 12 des Aktors 10

VPumpe =

Fördervolumen der Reversierpumpe 38

n(t) =

Drehzahl des Motors M

µvol =

volumetrischer Wirkungsgrad der Pumpe 38

Azyl=

wirksame Ring-Kolbenfläche des Kolbens 12 (ohne Stangenanteil)

s(t)zyl =

Verfahrweg des Kolbens 12

If the rear, second end position y is reached, the retraction routine does not need to be continued and a stop is made again by switching off the motor M. When the second end position y is reached, the drive in the form of the motor M is switched off and the calculated current position is saved as the maximum end position position. Furthermore, during the movement process from the first end position x to the second end position y, a theoretical position and speed actual value is calculated as follows via the hydraulic transmission ratio between pump 38 and actuator 10 and the knowledge of the current speed values $$v{\left(t\right)}_{eyl}=\frac{VPumpe\ast n\left(t\right)MOtOr\ast \mu vOl\ast 10}{Aeyl\ast 60}$$

$$s{\left(t\right)}_{eyl}={\displaystyle \int v{\left(t\right)}_{eyl}}dt,$$

with

v(t)cyl =

Speed of piston 12 of actuator 10

VPump =

Discharge volume of the reversing pump 38

n(t) =

Engine speed M

µvol =

volumetric efficiency of the pump 38

Azyl=

effective ring-piston area of piston 12 (without rod portion)

s(t)cyl =

Piston travel 12

During the initialization, the path of the piston 12 is fixed at the first end position proximity switch 44 with smin = 0 mm and smax is stored according to the above formula at the second end position proximity switch 44 for the initialization routine.

If all steps of the initialization have been completed successfully, the initialization is considered finished and “End Init” is displayed.

mit

Smin =

0 mm als Wert für den ersten Endlagen-Näherungsschalter 44

Smax =

maximale Entfernungsdistanz zum zweiten Endlagen-Näherungsschalter 44

c=

frei wählbarer Faktor

Vmax =

Maximalgeschwindigkeit für den Kolben 12

Vbrems =

Ziel- oder Bremsgeschwindigkeit nach Erreichen des virtuellen Bremspunktes bis zur jeweiligen Endlage x, y.

Once the initialization routine has been completed according to the schedule on the Continued page after the 2 is successfully completed, the cyclic operation of the application begins with a storage of the current position on the 2 In particular, by saving the current position as part of the cyclic process flow, a virtual braking point is calculated in order to reach one of the two end positions x, y in the shortest possible time. The calculated distance Sbrake to initiate the braking process depends on several factors: deceleration of the drive, maximum speed, distance between the end points or end positions x, y and a freely selectable factor c in order to make manual adjustments to the process. The calculation is carried out according to the following formula: $$s_{brems}=s_{min}+\left[\frac{c}{v_{max}\ast v_{brems}}\ast \left(s_{max}-s_{min}\right)\right],$$

with

Smin =

0 mm as value for the first end position proximity switch 44

Smax =

maximum distance to the second end position proximity switch 44

c=

freely selectable factor

Vmax =

Maximum speed for the piston 12

Vbrake =

Target or braking speed after reaching the virtual braking point up to the respective end position x, y.

As explained, the movement is carried out at a specified maximum speed and as soon as the virtual braking point is reached, the drive unit in the form of the motor M decelerates to the second specified target speed, which is significantly lower than the maximum speed until the piston 12 of the actuator 10 reaches the respective end point as end position x, y with a low impact speed on the actuator housing 18. Then the motor M switches off and again saves the current position and calculates the braking point for the opposite direction of movement, which can be seen from the process flow diagram after the 2 If the respective end position x, y is then reached, the cycle is repeated, whereby the initialization routine must be completed. Due to the recurring storage of the end positions x, y using the two proximity switches 44 and the respective calculation of the virtual braking point, system and environmental factors are taken into account, such as temperature, pump wear and oil condition. Overall, the process flow control provides an adaptive position control of a closed hydraulic axis without a position measuring system. This has no equivalent in the state of the art.

QUOTES INCLUDED IN THE DESCRIPTION

This list of 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 accepts no liability for any errors or omissions.

Cited patent literature

• EP 2610490 B1 [0002]

Claims (10)

Method for controlling a fluidic actuator (10) with at least the following steps: - carrying out an initialization to determine at least one defined end position (x, y) in a direction of movement of the actuator (10), and then - carrying out a position control on the basis of a virtual braking point for the actuator (10) associated with the end position (x, y), - decelerating the speed of the actuator (10) at the braking point until the end position (x, y) following in the direction of movement is reached; and - reversing the actuator (10) in the opposite direction of movement. Method for controlling a hydraulic actuator (10) according to Claim 1 with at least the following initialization steps: - controlling the actuator (10) by means of a drive (M) in one direction of movement until one of its two possible end positions (x, y) is reached, - detecting the respective end position (x, y) by means of a sensor device (44), - referencing one end position (x; y) as a zero or starting point, - controlling the actuator (10) in the opposite direction of movement in order to detect the further end position (y; x), - determining theoretical actual position and speed values during the movement of the actuator (10) between the two end positions (x, y), - switching off the drive (M) when the further end position (x, y) is reached, and - storing the current position value in the respective end position (x, y). Procedure according to Claim 1 or 2 , characterized in that the position control implemented as adaptive position control comprises at least the following steps: - taking over the respectively stored current position value from the initialization, - calculating a virtual braking point in order to reach the associated end position (x, y) in the shortest possible time, - moving the actuator (10), preferably at a predefinable maximum speed, until - reaching the virtual braking point with subsequent reduction to a predefinable target speed until the actuator (10) has finally reached the associated end position (x, y), - switching off the drive (M) and preferably storing the current position, and - calculating the braking point for the opposite direction of movement. Method according to one of the preceding claims, characterized in that , as part of the initialization during a movement process of the actuator (10) between the two end positions (x, y), the hydraulic transmission ratio between a hydraulic pump (38) drivable by the drive (M) and the actuator (10) is used to determine the theoretical position and speed actual values, taking into account associated speed values of the drive (M). Method according to one of the preceding claims, characterized in that the position of the two end positions (x, y) is used to calculate the respective braking point, as well as the maximum speed of the actuator (10) during the initialization until the respective end position (x, y) is reached and a braking speed of the actuator (10) at the respective braking point. Method according to one of the preceding claims, characterized in that the end positions (x, y) of the actuator (10) are repeatedly stored and the respective braking point is repeatedly calculated. Method according to one of the preceding claims, characterized in that at least one proximity switch (44) is used to determine the respective end position (x, y) of the actuator (10) without a position measuring system. Device for carrying out a method according to one of the preceding claims, characterized in that the actuator (10) has a hydraulic working cylinder, preferably in the form of a synchronous cylinder, and that a respective proximity switch (44) on the housing side determines the end positions (x, y) of the piston-rod unit (16) of the working cylinder. Device according to Claim 8 , characterized in that a hydraulic pump is a reversible pump (38) which drives the piston-rod unit (16) in both opposite directions of movement and that the pump (38) and the actuator (10) form a closed hydraulic supply circuit (40). Device according to Claim 8 or 9 , characterized in that the piston-rod unit (16) with its two piston rods (14) each drive a gas compressor (24) which alternately sucks in gas in the low-pressure range and releases it in a highly compressed state.

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