Method for operating an underwater adjustment device

Abstract

The present invention relates to a method for operating an underwater adjustment device (100b, 140) which is controlled by means of an electrohydraulic drive unit (100a; 110, 120, 122), comprising: measuring at least one operating variable of the electrohydraulic drive unit (100a; 110, 120, 122) during an adjustment of the underwater adjustment device (100b, 140) by means of at least one sensor (130a), the at least one operating variable comprising a hydraulic pressure provided by the electrohydraulic drive unit (100a; 110, 120, 122); determining at least one monitoring variable of the underwater adjustment device (100b, 140) on the basis of the at least one measured operating variable of the electrohydraulic drive unit (100a; 110, 120, 122); and controlling the underwater adjustment device (100b, 140) on the basis of the at least one determined monitoring variable.

Description

[0001] Method for operating an underwater actuating device

[0002] Description

[0003] The present invention relates to a method for operating an underwater actuating device controlled by an electrohydraulic drive unit, as well as to a computing unit and a computer program for implementing the method. Furthermore, the invention relates to an electrohydraulic drive unit for an underwater actuating device and an underwater actuating system comprising an electrohydraulic drive unit and an underwater actuating device.

[0004] Background of the invention

[0005] Underwater actuating devices with electrohydrostatic actuators and the mechanisms they operate can be used in many applications. One example is the use of an electrohydrostatic actuator underwater, e.g., to operate process valves in piping systems (pipelines or similar). In this, as well as in other applications, the highest possible actuator availability is desirable. To ensure this, the actuator status can be monitored, for example, using position or vibration sensors. However, this can increase their costs and component complexity.

[0006] Disclosure of the invention

[0007] According to the invention, a method for operating an underwater actuating device controlled by an electrohydraulic drive unit, a computing unit and a computer program for implementing the method, as well as an electrohydraulic drive unit for an underwater actuating device and an underwater actuating system comprising an electrohydraulic drive unit and an underwater actuating device with the features of the independent patent claims are proposed. Advantageous embodiments are the subject of the dependent claims and the following description.

[0008] The invention makes it possible to determine the state of an underwater actuating device based on operating variables of an electro-hydraulic drive unit for an underwater actuating device, comprising at least one hydraulic pressure. This eliminates the need for sensors that directly measure states of the underwater actuating device, such as its position or adjustment speed, thereby reducing the costs and component complexity of the actuating system. Furthermore, the invention offers the possibility of constructing the actuating system in a modular manner and combining the electro-hydraulic drive unit with different underwater actuating devices, e.g., from different manufacturers.

[0009] According to one embodiment, the underwater actuating device can comprise an actuator and a process valve. The actuator can be, in particular, a hydrostatic actuator, e.g., a linear actuator or a rotary actuator. In another embodiment, this can comprise a return spring that moves the actuator to a safe basic position (fail-safe position). An electric or pneumatic actuator is also possible. The process valve can be, for example, a slide valve or a rotary valve.

[0010] The electro-hydraulic drive unit comprises at least one sensor and is configured to control the underwater actuating device. The electro-hydraulic drive unit may, for example, comprise an electrically driven hydraulic pump and a pressure relief valve to provide the required amount of hydraulic energy for the hydrostatic actuator. The electro-hydraulic drive unit may, for example, contain at least one pressure sensor for detecting the provided hydraulic pressure and a speed sensor for detecting a speed / angular velocity of the hydraulic pump.

[0011] Specifically, in the method according to the invention, at least one operating variable of the drive unit is detected by means of at least one sensor during an adjustment of the underwater actuating device. The at least one operating variable comprises a hydraulic pressure provided by the electro-hydraulic drive unit. An adjustment of the underwater actuating device can, for example, involve the opening or closing of a process valve. The start and / or end of an adjustment can, for example, also be detected by means of the at least one operating variable. For example, this can suddenly decrease or increase at the start or end of an adjustment. A sudden decrease or increase in the operating variable can, for example, be detected when a gradient of the operating variable exceeds a predetermined value.In particular, the start and end of an adjustment can be initiated / controlled by the drive unit by providing the required amount of drive energy. The start of an adjustment can be initiated by the drive unit, for example, based on an external signal that can be received by a processing unit of the drive unit. For example, closing the process valve may be necessary due to maintenance or a leak in the piping system, and a control master of the piping system may issue a signal to the processing unit of the drive unit.

[0012] Based on the at least one detected operating variable of the drive unit, at least one monitoring variable of the underwater actuating device is determined. In particular, a plurality of monitoring variables can be determined from the detected operating variable of the drive unit. In other words, the detected operating variable or a plurality of features of the detected operating variable can be used to infer the behavior of the underwater actuating device, which can be monitored during subsequent adjustments. The underwater actuating device is controlled based on the at least one monitoring variable. In particular, the at least one monitoring variable can be used to adapt the control parameters of the drive unit, by means of which the underwater actuating device is operated, accordingly.

[0013] According to one embodiment, the at least one monitored variable can also be compared with a reference value, and a malfunction of the underwater actuating device can be detected, for example, if a deviation between the at least one specific monitored variable and the reference value exceeds a predetermined threshold value. The reference value can be, for example, a value of the at least one monitored variable when the underwater actuating device is new. According to one embodiment, a position of the underwater actuating device can be determined as a first monitored variable based on a change in the at least one operating variable during adjustment. In the electro-hydraulic drive unit used in conjunction with the hydrostatic actuator, the first monitored variable can be determined by a change in the hydraulic pressure during adjustment.

[0014] According to one embodiment, the position of the hydrostatic actuator can be determined based on an integrated volume flow and a change in the hydraulic pressure of the electro-hydraulic drive unit during the adjustment. For example, a quantity of hydraulic fluid supplied by the electro-hydraulic drive unit from the start of the adjustment until a time t less a quantity of hydraulic fluid required to generate a pressure increase Ap(t) in the actuator can be used to determine its volume change in the working chamber V SVA (t) and thus its position ISVA( ) can be used. In other words, a quantity balance of a quantity of hydraulic fluid supplied by the drive unit and a quantity "consumed" by the hydrostatic actuator can be carried out, for example, according to the following equation (1), where an additional leakage quantity Vi eak of the hydrostatic actuator is taken into account:

[0015] Here ISVAW) denotes the position of the actuator at time t, A A an effective area of ​​the hydrostatic actuator, V g a displacement of the hydraulic pump of the electro-hydraulic drive unit, t0 a starting time of the adjustment, a) P an angular velocity of the hydraulic pump, V a pressurized volume of hydraulic fluid, ß e the compression modulus of the hydraulic fluid, Ap(t) the pressure change at the time relative to the start time t0 of the adjustment and Vi eak the leakage amount of the hydrostatic actuator.

[0016] The pressure or pressure change Ap(t) in the electro-hydraulic drive unit and the angular velocity Ü) P The hydraulic pump's leakage can be determined, for example, using a pressure sensor on an output line of the drive unit and a speed sensor on a drive shaft of the hydraulic pump. The leakage quantity Vi eakof the hydrostatic actuator can be determined, e.g. based on tests carried out in advance on a hydraulic test bench, and stored as a parameter in the computing unit.

[0017] To determine the leakage quantity Vi eakof the hydrostatic actuator during its operation even more precisely, according to one embodiment this can also be determined based on an integrated volume flow and a change in the hydraulic pressure of the electro-hydraulic drive unit when the hydrostatic actuator is in a maximum position. In this case, the position of the actuator corresponds to its maximum adjustment travel and is therefore known. Therefore, the leakage quantity can be determined at this time from the above equation (1). The determination of the leakage quantity can, for example, be repeated during a large number of opening processes of the underwater actuating device, so that future leakage quantities can be predicted, for example by means of regression, whereby the actuator position can be determined more precisely.

[0018] According to one embodiment, a friction force can be determined as a second monitoring variable of the underwater actuating device based on a profile of the at least one operating variable during the adjustment. In particular, a friction force of the process valve of the underwater actuating device can be determined based on a first range of the profile of the at least one operating variable during the adjustment. The first range can comprise an adjustment range of the underwater actuating device in which the process valve is closed. In particular, the first range can contain a profile of the at least one operating variable from the start of an adjustment to a point in time at which the process valve opens. The opening point in time of the process valve can be determined based on the profile of the operating variable, as explained below.When the process valve is closed, the pressure of a medium applied to the process valve, which is conveyed through the piping system, acts on the underwater actuating device. This increases the frictional force that must be overcome in the process valve (e.g. between its actuating element and an associated seal) until a point in time at which the process valve opens a gap and a pressure equilibrium is established at the process valve. This point in time can be defined as the opening point of the process valve. In order to overcome the frictional force, an increased counterforce must be applied to the actuator for a short time, which can be suddenly reduced at the point in time at which the process valve opens. Since this counterforce is provided by means of at least one operating variable (e.g.by means of the pressure provided by the hydraulic drive unit in the working chamber of the hydrostatic actuator), the opening time is clearly visible in its course based on a corresponding negative gradient and can, for example, be determined based on a predetermined threshold value for the gradient in a predetermined time range after the start of an adjustment. The value of the operating variable, e.g. the hydraulic pressure, before the opening time of the process valve is in turn proportional to the friction force of the process valve and can be used to determine its friction coefficient. The friction coefficient can, for example, be determined each time the process valve is opened and closed and compared with a reference value of the friction coefficient in the new state of the process valve. If the determined friction coefficient deviates from the reference value by more than a predetermined threshold value, then, for example,the process valve must be serviced or replaced.

[0019] Furthermore, a frictional force of the actuator of the underwater actuating device can be determined based on a second range of the profile of the at least one operating variable during the adjustment, wherein the second range can comprise an adjustment range of the underwater actuating device in which the process valve is open. In particular, the second range can contain a profile of the at least one operating variable from the time the process valve opens until the end of the adjustment. In this range, the above-described frictional force of the process valve is no longer effective, and the frictional force of the actuator can be deduced from the profile of the at least one operating variable.If, for example, a hydraulic pressure curve for the hydrostatic actuator is evaluated during opening and closing of the process valve in the second area as a function of the actuator position / actuator travel, the frictional force of the actuator can be determined from the difference between the two pressure curves in this area, since this acts in the opposite direction to the hydraulic pressure when opening and in the same direction as the hydraulic pressure when closing. The frictional force of the actuator can, for example, be determined each time the underwater actuating device is adjusted and compared with a reference value when the actuator is new. If the determined frictional force deviates from the reference value by more than a predetermined threshold value, the actuator can be serviced or replaced, for example.

[0020] If the hydrostatic actuator also comprises a return spring, a preload force of the return spring can be determined based on a gradient of the at least one operating variable, in particular based on a pressure gradient, in the second region of the curve. For this purpose, an adjustment to open the process valve can be used, in particular, in which the return spring is compressed and thus its spring force is increased. This increase in spring force causes an increase in the hydraulic pressure provided by the electro-hydraulic drive unit for the actuator, which can be evaluated using the pressure gradient. Based on the determined pressure gradient, the preload force of the spring and its spring constant can be determined. Analogous to the leakage quantity of the hydraulic actuator, the preload force of the return spring can also be determined, e.g.be repeated during a large number of opening operations of the underwater actuating device, so that this can be predicted for future adjustments, for example by means of regression, and thus the friction force of the actuator can be determined more precisely.

[0021] A computing unit according to the invention, e.g. a controller of a drive unit for an underwater actuating device, is configured, in particular in terms of programming, to carry out a method according to the invention.

[0022] Implementing a method according to the invention in the form of a computer program or computer program product with program code for performing all method steps is also advantageous, as this entails particularly low costs, especially if an executing control unit is also used for additional tasks and is therefore already present. Suitable data storage devices for providing the computer program include, in particular, magnetic, optical, and electrical storage devices, such as hard disks, flash memories, EEPROMs, DVDs, and others. Downloading a program via computer networks (Internet, intranet, etc.) is also possible.

[0023] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

[0024] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0025] The invention is illustrated schematically in the drawings using exemplary embodiments and is described in detail below with reference to the drawings.

[0026] Character description

[0027] Figures 1a and 1b each schematically show an underwater actuating system comprising a drive unit and an underwater actuating device according to an embodiment of the invention.

[0028] Figure 2 shows schematically and exemplarily a hydraulic circuit diagram of the control system shown in Figures 1a and 1b.

[0029] Figures 3a and 3b each show a diagram with a pressure curve of an electro-hydraulic drive unit and an adjustment path of a hydrostatic actuator during opening or closing of a process valve according to an embodiment of the invention.

[0030] Figure 4 shows a section of the pressure curves from Figures 3a and 3b as a function of the adjustment travel.

[0031] Detailed description of the drawings Figures 1a and 1b each schematically show an underwater actuating system comprising an electro-hydraulic drive unit and an underwater actuating device according to an embodiment of the invention.

[0032] Figure 1a schematically illustrates a first embodiment of an underwater actuating system 100 according to the invention. By way of example, the underwater actuating system 100 comprises an electrohydrostatic actuator 100, which is schematically indicated here with some components.

[0033] The electrohydrostatic actuator 100 shown has a computing unit 110 designed as a control or regulating unit, a hydraulic unit 122 having a tank and a hydraulic pump and connected to an electric drive 120, as well as an actuator 126 with a safety device 125, and a mechanical interface 128 for connecting a process valve 140. The process valve 140 can be, for example, a slide valve in a line system (pipeline or the like), which is arranged underwater, for example, and must be capable of being actuated as needed. In this case, the actuator 126 can be designed as a linear actuator. However, it is also possible for the process valve to be designed as a rotary valve and the actuator accordingly as a rotary actuator.

[0034] Furthermore, the electrohydrostatic actuator 100 has one or more sensors 130, with which, for example, one or more pressures in the hydraulic unit 122 as well as a drive speed of the electric drive 120 or a hydraulic pump driven by it can be detected / measured. The measured values ​​can be transmitted to the computing unit 110.

[0035] Since the electrohydrostatic actuator 100 shown in Figure 1a includes the drive 120, 122 and the actuator 126 in one module, additional measured variables from sensors attached to the actuator 126, e.g., a position of the actuator 126, can also be transmitted to the computing unit 110. In particular, however, characteristics of the actuator 126 can be determined using sensors contained in the drive unit 120, 122.

[0036] Additionally, communication or data lines may be provided if necessary to transmit external control commands, e.g., from a control master of the line system, to the electrohydrostatic actuator 100. Figure 1b shows a control system 100a, 100b according to a further exemplary embodiment of the invention, which comprises the same components as the electrohydrostatic actuator shown in Figure 1a, but these are arranged in different modules. In this case, the computing unit 110, the electric drive 120, and the hydraulic unit 122 with the sensors 130a form an electrohydraulic drive unit 100a, and the actuator 126 with the safety device 125 and the mechanical interface 128, together with the process valve 140, form an underwater control device 100b. The two modules can be connected via a hydraulic interface 124.In this case, no sensors are included on the underwater actuator 100b, and information about the state of the underwater actuator 100b is determined based on sensor signals from the electro-hydraulic drive unit 100a.

[0037] Figure 2 schematically shows an exemplary hydraulic circuit diagram of the actuating system 100a, 100b shown in Figure 1b. Elements of the individual components 110, 120, 122, 125, 126, and 140 are each outlined in dashed lines.

[0038] Shown are the electrohydraulic drive unit 100a with the processing unit 110, the electric drive 120, and the hydraulic unit 122. Also shown is the underwater actuating device 100b with the hydrostatic actuator 126, the safety device 125, and the process valve 140. In this case, the actuator 126 is designed as a linear actuator 126. The drive unit 100a and the underwater actuating device 100b are connected to each other via the hydraulic interface 124.

[0039] The hydraulic unit 122 of the electro-hydraulic drive device 100a shown comprises a hydraulic pump 27, which is driven by the electric drive 120 and conveys hydraulic fluid from a tank T of the drive unit 100a via a line 25 to the hydraulic interface 124. A volume within the drive unit 100a, in particular the interior itself, can serve as the tank of the drive unit 100a, for example. A speed sensor 130a2 is arranged on a drive shaft (not further designated) between the electric drive 120 and the hydraulic pump 27, with which a speed / angular velocity of the hydraulic pump can be measured. A pressure sensor 130a1, which detects the pressure provided by the electro-hydraulic drive unit 100a, is arranged in the line 25 near the hydraulic interface 124.In the example shown, upstream of the pressure sensor 130a1, a connection 29 branches off from the line 25 to a pressure relief valve 28, by means of which hydraulic fluid can be directed from the linear actuator 126 via the hydraulic interface 124 into the tank T of the drive unit 100a. In the example shown, a check valve 26 is arranged in the line 25 between the hydraulic pump 27 and the connection 29 of the pressure relief valve 28, which prevents the hydraulic fluid from flowing back into the hydraulic pump 27 when the linear actuator 126 is relieved. Furthermore, in the example shown, upstream of the pressure relief valve 28 there is a variable throttle valve 28aa, with which the amount of hydraulic fluid flowing out of the linear actuator 126 can be controlled. In this case, an opening cross-section of the throttle valve 28aa and thus a flow through the throttle valve 28aa can be controlled.In particular, the variable throttle valve 28aa may be an electric valve whose cross section can be varied, e.g. by the computing unit 110, by means of a control current or a control voltage.

[0040] The electric drive 120 is signal-connected to the computing unit 110, which receives signals from the pressure sensor 130a1 and the speed sensor 130a2 and, based on the received sensor signals, outputs control signals to the electric drive 120 and the hydraulic unit 122. Furthermore, the computing unit 110 can include additional signal / data inputs to receive external control commands, e.g., from a control master of the piping system. This master can, for example, send a command to close the process valve 140 to the computing unit when maintenance or repair is required in the piping system.

[0041] The linear actuator 126 of the illustrated underwater actuating device 100b comprises a hydraulic cylinder 21, which is designed as a synchronous cylinder and has a piston rod 23 to which a piston 24 is attached. The piston 24 separates the working chamber 21aa from a second cylinder chamber 21ab, which is hydraulically connected to a tank T of the linear actuator 126. A volume within the linear actuator 126, in particular the interior itself, can serve as the tank of the linear actuator 126, for example. The working chamber 21aa is connected to the hydraulic interface 124 by means of a line (not further designated), and the hydraulic interface 124 is connected to the line 25 of the hydraulic unit 122 of the drive unit 100a. Figure 2 shows a position of the hydraulic cylinder 21 with the relief valve 28 open, in which the working chamber 21aa has a minimum size, while the opposite cylinder chamber 21ab has a maximum size.In the example shown, a hermetically sealed cylinder chamber 21ac is arranged or can be created at an outer end of the piston rod 23, in which a vacuum is formed upon movement of the piston rod 23. A change in the volume of the cylinder chamber 21ac upon movement of the piston expediently corresponds to a change in the volume of the portion of the piston rod outside the housing, i.e., the pendulum volume of the hydraulic cylinder 21 can be reduced.

[0042] The linear actuator 126 is connected to the safety device 125 via the common piston rod 23. In this case, the safety device 125 contains a housing 1 in which a further piston 4 is arranged on the piston rod 23. A spring 6 is clamped between the piston 4 and an end face of the housing 1. The housing 1 of the safety device 125 can be filled with a hydraulic fluid. In this case, the spring 6 of the safety device has its maximum spring travel and thereby presses the piston 4 into an end position. By means of the common piston rod 23, the spring force also moves the piston 24 of the hydraulic cylinder 21 into an end position in which the working chamber 21 aa has a minimal size.

[0043] The mechanical interface 128 is arranged on a side of the safety device 125 opposite the linear actuator 126, by means of which the safety device can be connected to the process valve 140.

[0044] The process valve 140 shown comprises a disc 140b, which opens and closes a valve channel 34 as a result of a movement of the piston rod 23. When the channel 34 is closed by the disc 140b, as shown here, a space 140a adjacent to the disc 140b is also filled with fluid present in the channel 34. This fluid exerts a force on the disc 140a in the closing direction of the process valve 140, thus supporting the spring force of the spring 6 of the safety device 125.

[0045] To open the closed process valve shown in Figure 2, the relief valve 28 must first be closed, and then hydraulic fluid must be pumped from the hydraulic pump 27 via the hydraulic interface 124 between the hydraulic unit 122 and the linear actuator 126 into the working chamber 21aa of the linear actuator 126. As a result, a force from the hydraulic cylinder 21 acts against the spring force of the spring 6 of the safety device 125, so that the spring 6 is preloaded / compressed. The piston rod 23 of the linear actuator 126 and the safety device 125 moves against the direction of the spring force and displaces the connected disc 140b of the process valve 140 such that the valve channel 34 is opened (not shown).

[0046] A position of the linear actuator 126 can be determined during adjustment, for example, using a quantity of hydraulic fluid pumped from the hydraulic unit 122 into the working chamber 21aa and the pressure measured by the pressure sensor 130a1 (operating variables of the electro-hydraulic drive unit 100a) at the output of the hydraulic unit 122. The pumped volume flow can be determined based on the displacement of the hydraulic pump 27 and the measured speed of the pump 27. Based on these measured variables, the computing unit 110 can calculate a quantity balance at the hydraulic interface 124, e.g., using equation (1), by means of which the position of the linear actuator (first monitoring variable) can be continuously determined during adjustment. In this way, the adjustment of the process valve 140 can be determined even without direct position measurement or without a position sensor, and the linear actuator 126 can be controlled accordingly.

[0047] Furthermore, the friction of the underwater actuating device 100b (second monitoring variable) can be determined by measuring the hydraulic pressure in the drive unit 100a at the output of the hydraulic unit. The measured pressure at this point essentially corresponds to the pressure in the working chamber 21aa of the hydraulic cylinder 21.

[0048] For this purpose, Figures 3a and 3b each show a diagram with a pressure curve PHSU of the electro-hydraulic drive unit 100a and an adjustment path ISVA of the linear actuator 126 during opening or closing of the process valve 140, wherein the adjustment path ISVA (first monitoring variable) was determined based on the quantity balance of the hydraulic fluid as described above.

[0049] The pressure curve PHSU shown in Figure 3a during opening of the process valve is divided into four ranges po to ps. When the process valve is closed, the piston 24 in the hydraulic cylinder 21 of the linear actuator 126 is pressed into the end position by the force of the spring 6 of the safety device and a pressure of the fluid in the chamber 140a acting on the disc of the process valve 140, in which the working chamber 21aa has a minimal volume. The relief valve 28 is open, so that the pressure pO measured by the pressure sensor 130a1 at the output of the hydraulic unit 122 in this position essentially corresponds to the pressure in the tank T of the electro-hydraulic drive unit 100. In order to open the process valve 140 from the closed state, an increased frictional force between the disc 140b and an associated seal (not shown) must be overcome, which is caused by the pressure in the space 140a.For this purpose, the pressure of the hydraulic unit 122 must be raised to the value pi, which is present at the output of the hydraulic circuit, and thus also in the working chamber 21aa of the hydraulic cylinder 21, between 12 s and 60 s. In this first range pi of the pressure curve PHSU, the pressure in the hydraulic unit 122 is thus proportional to the friction force of the process valve 140 and can be used to determine its friction coefficient.

[0050] At time t = 60 s, the process valve is opened slightly, and fluid present at disk 140b can flow through channel 34. This creates a pressure equilibrium between chamber 140a and channel 34, eliminating the increased frictional force between disk 140b and the associated seal. Consequently, the pressure in the hydraulic unit can be reduced to pressure p2 to further open process valve 140. This pressure acts on piston 24 in a second range of pressure curve PHSU and causes the process valve to be fully opened between 60 s and 365 s. Pressure p2 is essentially proportional to the sum of the force of spring 6 counteracting the force of hydraulic cylinder 21 and the friction present in linear actuator 126 and safety device 125.

[0051] When the process valve 140 is fully open at time t = 365 s, the pressure in the hydraulic unit 122 is raised to the operating pressure p3, with which the process valve is kept permanently open.

[0052] The pressure curve PHSU_O clearly shows that a pressure gradient occurs between the described individual opening phases pi to pa of the process valve 140, which can be used to determine the start and end of the adjustment as well as the opening time of the process valve. Similarly, a pressure curve PHSU_C shown in Figure 3b can be divided into individual phases during a closing of the process valve 140.

[0053] At the beginning of the closing process when the pressure relief valve 28 is opened (t - 420 s), the latter drops steeply from the operating pressure pa to a pressure p4 in the working chamber 21aa of the hydraulic cylinder 21, which during the closing process in the period from -420 s to -425 s (second range of the pressure curve PHSU_C) together with the friction of the linear actuator 126 and the safety device 125 opposes the spring force of the spring 6.

[0054] At time t - 425 s, the disc 140a of the process valve 140 closes the channel 34, and the spring force of the spring 6 must overcome the frictional force between the disc 140a and the seal to completely close the process valve 140. During this period between -425 s and -428 s, the pressure ps prevails in the working chamber 21aa, which drops to the output pressure po after the process valve has completely closed. This pressure po occurs when the pressure of the fluid in the channel 34 present in the chamber 140a also acts on the linear actuator 126 in the closing direction of the process valve 140. Accordingly, the frictional force of the process valve can also be deduced from the pressure ps, and the range of the pressure curve PHSU_C in which this pressure prevails corresponds to the first range.

[0055] Analogous to the pressure curve PHSU_O when opening the valve, the pressure curve PHSU_C when closing the valve also has pressure gradients between the individual closing phases, which can be used to determine a start and end of the adjustment as well as a closing time of the process valve.

[0056] This makes it possible to differentiate between the individual loads on the underwater actuating device 100b and to monitor the friction of the process valve 140 in the first range of adjustment (PHSU_O = Pi; PHSU_C = ps), while in the second range of adjustment (PHSU_O = P2; PHSU_C = P4) the friction of the linear actuator 126 and the safety device 125 can be monitored.

[0057] This is further illustrated by Figure 4, which shows the relevant sections of the pressure curves PHSU_O, PHSU_C from Figures 3a and 3b as a function of the adjustment range ISVA. Figure 4 shows the first and second ranges Ai, A2 of the pressure curves PHSU_O, PHSU_C during the opening and closing of the process valve 140 over the adjustment range ISVA of the linear actuator 126. In the first range Ai, up to an adjustment range of ISVA_I2 = 20 mm in this case, the pressures pi (opening) and ps (closing) are present in the working chamber 21aa of the hydraulic cylinder 21. These are both proportional to the friction force of the process valve described above and can therefore be used to determine the friction coefficient of the process valve. In this respect, in the first range Ai of the pressure curves PHSU_O, PHSU_C below the adjustment path ISVA_I2, the friction of the process valve 140 can be determined during each adjustment and a course of the friction coefficient can be monitored.For example, the determined friction coefficient can be compared with a reference value in the new state of the process valve 140 after each adjustment, and if a deviation between the determined friction coefficient and the reference value exceeds a predetermined threshold, maintenance / repair of the process valve 140 can be initiated.

[0058] In the second range A2 of the pressure curves PHSU_O, PHSU_C, in which the frictional force of the process valve 140 is no longer effective, the frictional force of the linear actuator 126 and the safety device 125 can be determined based on a difference between the pressures p2 and p4. This force acts against the pressure force of the hydraulic cylinder 21 during the opening of the process valve 140 and against the spring force of the spring 6 of the safety device 125 during the closing of the process valve 140.

[0059] In this respect, during the opening process, the pressure force of the hydraulic cylinder 21 : p2■ A = F F + F R (2) where A is the area of ​​the piston 24, F F the spring force and F R denote the frictional force.

[0060] However, during the closing process by the spring force of the safety device 126, the following applies:

[0061] F F = p4■ A + F R (3) By inserting equation (3) into equation (2) and rearranging for the friction force FR, we get:

[0062] The friction force determined in this way can also be determined during each adjustment of the process valve 140 and compared with a reference value of the friction force in the new state of the linear actuator 126 and the safety device 125. If a deviation between the determined friction force and the reference value exceeds a predetermined threshold, appropriate maintenance or repair can be initiated.

[0063] Furthermore, in the second area A2 with known friction force F R a change in the spring force F F over the adjustment range ISVA, e.g., during the opening of the process valve 140, based on equation (2) from a pressure gradient Ap2. This value can also be determined during each adjustment and monitored accordingly.

[0064] In summary, it is clear from the described embodiments that the invention makes it possible to control and monitor the components of the underwater actuating device 100b without additional sensors by means of a suitable evaluation of the operating variables of the drive device 100a.

Claims

Claims 1. A method for operating an underwater actuating device (100b, 140) controlled by an electrohydraulic drive unit (100a; 110, 120, 122), comprising the steps: - detecting at least one operating variable of the electrohydraulic drive unit (100a; 110, 120, 122) during an adjustment of the underwater actuating device (100b, 140) by means of at least one sensor (130a), wherein the at least one operating variable comprises a hydraulic pressure provided by the electrohydraulic drive unit (100a; 110, 120, 122); - determining at least one monitoring variable of the underwater actuating device (100b, 140) based on the at least one detected operating variable of the electrohydraulic drive unit (100a; 110, 120, 122); and - controlling the underwater actuating device (100b, 140) based on the at least one specific monitoring variable.

2. The method of claim 1, further comprising the steps - comparing the at least one specific monitoring variable with a reference value; and - detecting a malfunction of the underwater actuating device (100b, 140) when a deviation between the at least one specific monitoring variable and the reference value exceeds a predetermined threshold value.

3. The method according to claim 1 or 2, wherein determining the at least one monitoring variable comprises: Determining a position of the underwater actuating device (100b, 140) as a first monitoring variable based on a change in the at least one operating variable during the adjustment.

4. Method according to one of the preceding claims, wherein determining the at least one monitoring variable comprises: Determining a friction force as a second monitoring variable of the underwater Adjusting device (100b, 140) based on a course (PHSU_O, PHSU_C) of the at least one operating variable during the adjustment.

5. The method according to claim 4, wherein the underwater actuating device (100b, 140) comprises an actuator (100b) and a process valve (140), and a frictional force of the process valve (140) is determined based on a first range (Ai) of the curve (PHSU_O, PHSU_C ) of the at least one operating variable during the adjustment and a frictional force of the actuator (100b) is determined based on a second range (A2) of the curve (PHSU_O, PHSU_C ) of the at least one operating variable during the adjustment.

6. The method according to claim 5, wherein the first range (Ai) comprises an adjustment range of the underwater actuating device (100b, 140) in which the process valve (140) is closed, and the second range (A2) comprises an adjustment range of the underwater actuating device (100b, 140) in which the process valve (140) is open.

7. The method according to claim 5 or 6, wherein the actuator (100b) contains a return spring (6) and the determination of the at least one monitoring variable comprises: determining a pretensioning force of the return spring (6) as a monitoring variable based on a gradient of the at least one operating variable in the second region (A2) of the curve (PHSU_O, PHSU_C).

8. The method according to any one of the preceding claims, wherein the actuator (100b) is a hydrostatic actuator (125, 126) and the position of the underwater actuating device (100b, 140) is determined based on an integrated volume flow and a change in the hydraulic pressure of the electro-hydraulic drive unit (110, 120, 122) during the adjustment.

9. The method according to claim 8, wherein determining the at least one monitoring variable comprises: Determining a leakage of the hydrostatic actuator (125, 126) as a monitoring variable based on an integrated volume flow and a change in the hydraulic pressure of the electro-hydraulic drive unit (110, 120, 122) when the hydrostatic actuator (125, 126) is in a maximum position.

10. A computing unit (110) configured to carry out a method according to any one of the preceding claims.

11. A computer program which causes a computing unit (110) to carry out a method according to one of claims 1 to 9 when it is executed on the computing unit (110).

12. A machine-readable storage medium having stored thereon a computer program according to claim 11.

13. Electro-hydraulic drive unit (100a; 110, 120, 122) for an underwater actuating device (100b, 140) comprising an electric drive, a hydraulic pump, at least one sensor (130a) and a computing unit (110) according to claim 10.

14. Underwater actuating system comprising an electro-hydraulic drive unit (100a; 110, 120, 122) according to claim 13 and an underwater actuating device (100b, 140).

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