NL2024199B1

NL2024199B1 - Hydraulic system comprising active devices and method for controlling such a hydraulic system

Info

Publication number: NL2024199B1
Application number: NL2024199A
Authority: NL
Inventors: Henk Cnossen Jan; Johannes Gerardus Heijlen Martinus; Alexandrovích Burakov Denis
Original assignee: Flamco Bv
Priority date: 2019-11-08
Filing date: 2019-11-08
Publication date: 2021-07-20
Also published as: WO2021091386A1; EP4055327A1

Abstract

14 TITLE: HYDRAULIC SYSTEM COMPRISING ACTIVE DEVICES AND METHOD FOR CONTROLLING SUCH A HYDRAULIC SYSTEM 5 ABSTRACT: The invention disclosed herein relates to a hydraulic system comprising fluid conduits and a plurality of active devices to adjust an operational parameter of said hydraulic system. Hydraulic systems of this type commonly form part of a central heating system or hot water system in which heated fluid is transferred through the conduits towards and from radiators located in spaces to be 10 heated. Further, the disclosure relates to a method REPRESENTATIVE FIGURE: figure 1.

Description

HYDRAULIC SYSTEM COMPRISING ACTIVE DEVICES AND METHOD FOR

CONTROLLING SUCH A HYDRAULIC SYSTEM The invention disclosed herein relates to a hydraulic system comprising fluid conduits and a plurality of active devices to adjust an operational parameter of said hydraulic system. Hydraulic systems of this type commonly form part of a central heating system or hot water system in which heated fluid is transferred through the conduits towards and from radiators located in spaces to be heated.

Hydraulic systems of the aforementioned type are closed systems to avoid the introduction of in particular oxygen into the conduits, where it may cause corrosion. A consequence of being a closed system is that such hydraulic systems are continuously subjected to variations in fluid pressure and fluid volume stemming from temporal and spatial variations in temperature of fluid located therein. This poses the risk that a pressure of fluid within the hydraulic system rises to excessive levels, which may damage the hydraulic system and/or interrupt a proper functioning thereof.

To prevent damage to or malfunctioning of the hydraulic system, hydraulic systems comprise one or more active devices designed to diminish exuberant pressures of fluid to acceptable levels. For this purpose, such active devices typically comprise a hollow tank or vessel bisected by a flexible diaphragm. The section of the hollow vessel beneath this flexible diaphragm is fluidly connected to the fluid conduits of the hydraulic system and therefore contains fluid, whereas the section above the flexible diaphragm contains gas and is fluidly connected to a compressor and/or a pump. A buildup of excess pressure of fluid in the hydraulic system is offset by allowing fluid from the fluid conduits to enter the lower section of the hollow vessel, thereby displacing the flexible diaphragm, in conjunction with an operation by the compressor or pump.

Moreover, active devices may likewise raise pressure of fluid by injecting fluid into the fluid conduits of hydraulic system, and periodically degas the hydraulic system be venting off gasses trapped therein.

Larger hydraulic systems typically comprise a plurality of active devices, each of which comprises a finite expansion volume and remaining expansion capacity; and therefore a finite capability of adjusting pressure of fluid in the hydraulic system. Moreover, when pressure of fluid in the hydraulic system is adjusted by an active device as described above, the expansion volume and remaining expansion capacity of said active device are changed. This in turn affects the ability of said active device to react to subsequent deviations in pressure of fluid, as doing so requires an appropriate amount of expansion volume or expansion capacity.

Furthermore, in hydraulic systems comprising a plurality of active devices, for example due to space limitations, said active devices are often located at different height levels relative to one another. Due to static fluid pressure stemming from a height distance between the highest point of the hydraulic system and the height level at which a given active device is placed, each of the active devices experiences a different pressure of fluid in the hydraulic system even under normal operating conditions.

Moreover, the flexible diaphragm comprised by each active device exhibits a tendency to retain its initial shape when displaced while said active device injects fluid into the hydraulic system or withdraws fluid therefrom, As such, there exists no linear relationship between pressure of fluid in the hydraulic system and an expansion volume of a given active device; the active devices in such a hydraulic network instead exhibiting hysteretic behavior.

The above described properties of active devices contribute to overall complexity of designing, installing, maintaining and efficiently operating hydraulic systems in which a plurality of such active devices is applied.

An objective of the present invention is to provide a hydraulic system that is improved relative to the state of the art in that at least one or some of the above described drawbacks is obviated or abated. This objective is achieved with a hydraulic system comprising fluid conduits, a plurality of active devices, such as expansion pumps or compressor devices, fluidly connected to the fluid conduits, to adjust an operational parameter of the hydraulic system, and a controller, wherein at least one of the active devices comprises a fluid based transmitter and at least one other of the active devices comprises a fluid based receiver to respectively transmit and receive at least one signal through the fluid conduits with the fluid therein as a transmission medium.

Preferred embodiments of a hydraulic system in accordance with the present invention are subject of the appended dependent apparatus claims.

The above objective is furthermore achieved with an active device of or for such a hydraulic system.

The objective stated above is furthermore achieved with a method in accordance with the present invention for controlling an hydraulic system comprising fluid conduits and a plurality of active devices, such as expansion pumps or compressor devices, fluidly connected to the fluid conduits, to adjust an operational parameter of fluid in the conduits, said method comprising transmitting a signal at an active device comprising a fluid based transmitter, and receiving said signal at an active device comprising a fluid based receiver, wherein the signal is transmitted through the fluid conduits with the fluid therein as a transmission medium.

Preferred embodiments of a method for controlling a hydraulic system are subject of the appended dependent method claims. Lastly, the above objective is achieved with a computer program comprising instructions to cause a controller comprised by a hydraulic system to execute the steps of the aforementioned method.

Herein above, general concepts of a hydraulic system and corresponding control method in accordance with the present invention are referred to on the basis of relatively generic indications of the features thereof, which correspond to the definitions in the appended independent claims. Herein below, preferred exemplary embodiments of the present invention are elucidated with reference to the appended drawing. It is emphasised here that these embodiments are merely of an exemplary nature and that the same or similar functionalities may be achieved with the basic principles of the present invention.

Throughout the below description of the exemplary embodiments of the present invention, identical or similar entities, components, functional units or concepts and the like may be referred to using similar or identical reference signs when referring to the appended drawing, in which: Figure 1 depicts an exemplary embodiment of a hydraulic system in accordance with the present invention; Figure 2 depicts an exemplary embodiment of an active device comprised by the hydraulic system of Figure 1; and Figure 3 depicts a graph illustrating at least part of a scheme for determining that at least two of the active devices depicted in figure | are fluidly connected to one another.

With reference to Figure 1 a hydraulic system 1 comprises fluid conduits 2 carrying fluid towards and from various components or devices comprised by the system. Hydraulic system 1 is a closed off system with no substantial amount of fluid being exchanged with its surroundings.

Hydraulic system | may comprise any number of devices or components fluidly connected with fluid conduits 2 including boilers or other heating elements and radiators and other types of heat exchangers (not shown).

During operation of hydraulic system 1 fluid within conduits 2 is subjected to temporal and spatial temperature variations. As this fluid expands when its temperature increases and compresses when its temperature decreases, hydraulic system 1 is consequently subjected to variations in pressure of fluid therein. The variations in pressure of fluid in hydraulic system 1 may result in a pressure of fluid that is either excessively high or excessively low, which may hamper the operational functionality of hydraulic system 1 or cause damage to hydraulic system 1.

To prevent such issues from occurring hydraulic system 1 comprises a plurality of active devices 3a, 3b, 3c, 3d configured to, if deemed to be necessary, adjust a pressure of fluid within hydraulic system 1 to a safe or acceptable level.

In hydraulic system 1 each of the active devices 3a, 3b, 3c, 3d is fluidly connected to fluid conduits 2 and configured to adjust an operational parameter of hydraulic system 1. In the context of the present disclosure, the term “operational parameter” may constitute any parameter related to an operation of hydraulic system 1; and may comprise, for example, pressure of fluid, flow speed of fluid, temperature of fluid or the like. In accordance with the present exemplary embodiments,

said operational parameter constitutes a pressure of fluid within hydraulic system 1 that is adjustable by an action of a pump or a compressor comprised by active devices 3a, 3b, 3c, 3d.

In Figure 1 each of the plurality of active devices 3a, 3b, 3c, 3d is additionally connected to a communication network 4 schematically represented by the dashed lines connecting each of said active devices 3a, 3b, 3c, 3d.

The communication network 4 may be embodied by a wired communication network or by a wireless communication network.

In embodiments of hydraulic system | wherein communication network 4 is embodied by a wireless communication network, said wireless communication network may be based on any suitable technology, such as wireless fidelity (Wi-Fi), cellular technology, Bluetooth or ZigBee.

Communication network 4 may furthermore be connected to an external server or client or cloud-based computing platform (not shown). Figure 2 depicts an exemplary embodiment of an active device 3 comprised by hydraulic system 1 as depicted in Figure 1 with reference signs 3a, 3b, 3c, 3d.

Active device 3 comprises a fluid based transmitter 5 configured to transmit a signal through fluid conduits 2 with the fluid therein as a transmission medium.

Active device 3 furthermore comprises a fluid based receiver 6 configured to receive a signal through fluid 2 with the fluid therein as a transmission medium.

Fluid based transmitter 5 and fluid based receive 6 of active device 3 are respectively configured to transmit and receive signals to and from other active devices 3, which likewise comprise a similar or identical fluid based transmitter 5 and/or fluid based receiver 6. In the embodiment depicted in Figure 2, fluid based transmitter 5 and fluid based transmitter 6 are embodied by distinct, separate components.

Alternatively, there may be provided a transducer (not shown) having the combined functionality of fluid based transmitter 5 and fluid based transmitter 6. Active device 3 furthermore comprises a controller 8. The scope of the functionality of controller 8 may vary in accordance with different embodiments of the present invention, which will be elucidated here below.

In the embodiment of an active device 3 depicted in Figure 2, controller 8 is comprised by active device 3. Alternatively, controller 8 may embodied by a distinct entity located within hydraulic network 1 that does not form part of any one of active devices 3a, 3b, 3c, 3d in particular.

Moreover, controller 8 may alternatively be located outside of the physical boundaries of hydraulic network 1; being embodied by a an external server, client or cloud-based computer platform connected to any one or more of devices 3a, 3b, 3c, 3d via communication network 4. Moreover, hydraulic system 1 may comprise a plurality of controllers 8, each of which exhibiting at least some of the functionality that will be described here below.

In certain embodiments of hydraulic system 1, the controller 8 is in communication with, for example, active device 3a comprising fluid based transmitter 5 and, for example, active device 3b comprising fluid based receiver 6. In this embodiment, controller 8 is configured to — upon transmission of a signal by fluid based transmitter 5 of active device 3a and reception of said signal by fluid based receiver 6 of active device 3b — determine that active device 3a and active device 3b are fluidly connected to one another via fluid conduits 2. Consequently, existence of a fluid connection between two or more of the active devices 5 3a, 3b, 3c, 3d can be determined quickly and reliably, which is considered advantageous when designing or installing hydraulic system 1 or expanding an existing hydraulic system 1 with additional fluid conduits 2 and/or active devices 3a, 3b, 3c, 3d. In addition, such a determination scheme may be applicable for diagnosing a malfunctioning of hydraulic system 1, for example when detecting leaks in fluid conduits 2.

Moreover, as will be elucidated here below, knowledge of an existent fluid connection between two or more of active devices 3a, 3b, 3c, 3d may be applied to adjust an operational parameter of hydraulic system 1 in a manner wherein fluidly connected active 3a, 3b, 3c. 3d work together in a coordinated manner, thereby enhancing a degree efficiency with which said adjustment of the operational parameter is performed.

In preferred embodiments of the present invention fluid based transmitter 5 is configured to transmit a signal by manipulating a pressure of fluid in conduits 2, thereby emitting a predetermined pressure coded signal through fluid conduits 2. Such a pressure coded signal may be embodied by one or more pressure pulses with a predetermined duration, amplitude and/or time intervals between them. Alternatively, the signal may constitute at least one of a flow speed coded signal, an acoustic signal, an optical signal, an electrical signal and an electromagnetic signal that propagates through fluid in fluid conduits 2. Evidently, in these embodiments fluid based transmitter 5 and fluid based receiver 6 comprise appropriate means to respectively transmit and receive the fluid based signal that is used, such as respectively an acoustic transmitter and acoustic receiver in embodiments wherein an acoustic signal is applied.

In accordance with certain embodiments of the present invention wherein the fluid based signal is a pressure coded signal or a flow speed coded signal, fluid based transmitter 5 may be embodied by a pump and/or a compressor comprised by active device 3a, 3b, 3c, 3d that is additionally configured perform adjustment of pressure of fluid in hydraulic system 1.

During operation of hydraulic system 1, there may arise a need to adjust an operational parameter of hydraulic system 1. For example, it may required to adjust pressure of fluid within hydraulic system 1 when said pressure exceeds a predetermined maximum value, at which pressure of fluid there exists a possibility that operation of hydraulic system 1 will be compromised or damage to hydraulic system 1 will occur.

In accordance with certain embodiments of the present invention, controller 8 may be configured to select at least one active device 3a, 3b, 3c, 3d fluidly connected with to least one other active device 3a, 3b, 3c, 3d and to drive said at least one selected active device 3a, 3b, 3c, 3d to adjust the operational parameter. Controller 8 may drive active device 3 to withdraw fluid from hydraulic system 1 or inject fluid therein, thereby adjusting pressure of fluid in hydraulic system.

In these embodiments, controller 8 may select one or more of fluidly mutaally connected active devices 3a, 3b, 3c, 3d based on an operational characteristic of one or more of these active devices 3a, 3b, 3c, 3d. For example, controller 8 may select one or more of active devices 3a, 3b, 3c, 3d based on an available expansion volume, thereby ensuring that the at least one selected active device 3a, 3b, 3c, 3d contains a sufficient volume of fluid to be injected into hydraulic system 1 to adjust a pressure of fluid therein. An alternative or additional operational characteristic, on the basis of which a fluidly connected active device 3a, 3b, 3c, 3d may be selected by controller 8, is a remaining expansion capacity in said active device 3a, 3b, 3c, 3d required for withdrawing liquid from hydraulic system 1, to thereby lower a pressure of fluid in hydraulic system 1. Furthermore, as described above each active device 3a, 3b, 3c, 3d exhibits hysteretic behaviour due to the presence of a flexible diaphragm therein. Consequently, each of active devices 3a, 3b, 3c, 3d comprises a hysteresis characteristic with a certain hysteresis or bandwidth, which likewise constitutes an operational characteristic of said respective active devices 3a, 3b, 3c, 3d.

In particular during coordinated adjustments of an operation parameter by a plurality of fluidly mutually connected active devices 3a, 3b, 3c, 3d the active device comprising the widest bandwidth or hysteresis may dictate; the bandwidth of other active devices being recalculated based thereon and the newly found bandwidth for an individual hysteresis being normative for a specific active device 3a, 3b, 3c, 3d to all actions.

Controller 8 may furthermore be configured to drive the at least one selected active device 3a, 3b, 3c, 3d by transmitting thereto a control signal. The control signal is preferably transmitted using wired or wireless communication network 4. Alternatively, control signal may be transmitted by controller 8 using fluid based transmitter 5 comprised by a selected active devices 3a, 3b, 3c or 3d to a fluid based receiver 6 comprised by an other active device 3a, 3b, 3c or 3d through fluid conduits 2, thereby using the fluid located therein as a transmission medium. These embodiments obviate the need for the presence of dedicated communication network 4. Nevertheless, controller 8 is preferably configured to be capable of transmitting control signals through both fluid conduits 2 and communication network 4 to achieve an increased degree of flexibility and reliability. In these embodiments, fluid based transmission of control signals through fluid conduits 2 may be used in the event that communication by means of communication network 4 is not available, for example due to a technical malfunction or a power failure. Similarly, transmission of control signals may occur exclusively through communication network 4 in the event that fluid based transmission of control signals is not possible in a reliable manner, for example due to a leak in somewhere in fluid conduits 2 of hydraulic system 1.

In accordance with certain embodiments, active device 3a, 3b, 3c, 3d may comprise a sensor 7 configured to sense an operational parameter of hydraulic system 1. The operational parameter of hydraulic system 1 may be a pressure of fluid within hydraulic system 1, wherein sensor 7 comprises a pressure sensor.

In certain embodiments of hydraulic system 1 in accordance with the present invention controller 8 may be configured to determine a need to adjust an operational parameter of hydraulic system 1. Determination of this need may be based on the operational parameter exceeding a predetermined range as measured by sensor 7 by exceeding a lower or upper threshold. Correction of said operational parameter may subsequently be performed as described above.

Referring now to Figure 3, there is depicted a total of four graphs, with reference to which an exemplary scheme for determining that at least two of active devices 3, 3a, 3b, 3c, 3d are fluidly connected to one another will be further elucidated.

In Figure 3, the top two graphs respectively represent an expansion volume V, of a given active device 3, for example active device 3a, as a function of time; and a pressure of fluid P, in hydraulic system 1 as a function of time, at or near a location at which active device 3a is fluidly connected to fluid conduits 2. The bottom two graphs of Figure 3 respectively represent an expansion volume V of an other active device 3, for example active device 3b, a function of time; and a pressure of fluid Py, in hydraulic system 1 at or near a location at which active device 3b is fluidly connected to fluid conduits 2 of hydraulic system 1.

At time to, as indicated on the horizontal axes in the graphs of Figure 3, a fluid based transmitter 5 comprised by active device 3b transmits a pressure coded signal to a fluid based receiver 6 comprised by active device 3a. Transmission of the pressure coded signal comprises, in this exemplary embodiment, injection of fluid into hydraulic system 1 from an expansion volume V‚ of active device 3b, for example by means of a pump or compressor comprised by active device 3b.

As indicated in the bottom two graphs of Figure 3, the initial injection of fluid into hydraulic system 1 occurs over the time period from t to t,, during which time pressure Py, of fluid in hydraulic system 1, as measured near active device 3b, increases while an expansion volume Vy, of active device 3b decreases. The increase in pressure Py, dissipates throughout fluid conduits 2 of hydraulic system 1 with a finite speed, therefore experiencing a “delay” before reaching active device 3a at ty, where it is detected as pressure P, by a fluid based receiver 6 comprised by the active device 3a. The injection of fluid into hydraulic system 1 by active device 3b is subsequently followed by withdrawal of fluid therefrom starting at t,, during which the expansion volume Vy, of active device 3b increases. In the graphs of Figure 3, this withdrawal of liquid from hydraulic system 1 continues until tz, the resulting increase in pressure being detectable as pressure Pa at active device 3a at ty. Upon successful transmission and reception of this signal, controller 8 may determine that active devices 3a and 3b are fluidly connected to one another via fluid conduits 2.

The determination scheme depicted in Figure 3 may furthermore comprise transmission and reception of a signal in a reverse direction to determine that active devices 3a, 3b are fluidly mutually connected. In other words, said determination scheme may furthermore comprise transmitting, by fluid based transmitter 5 comprised by active device 3a, a subsequent pressure coded signal to fluid based receiver 6 comprised by active device 3b.

The manipulation of pressure P,, Py, of fluid in hydraulic system 1, that is to say the rise and decline thereof, may be repeated a predetermined number of times as represented by the exemplary sawtooth wave in the graphs of Figure 3. The predetermined number of increases and decreases in pressure P,, P, of fluid in hydraulic system 1 constitute an example of a pressure coded signal in the context of the present disclosure and invention.

The person skilled in the art will understand that, in embodiments of the present invention wherein a signal other than a pressure coded signal is applied, determination schemes similar or otherwise comparable to the one illustrated in Figure 3 may be applied.

While the exemplary embodiments described thus far concerned a hydraulic system 1 forming part of a heating system, the scope of the present disclosure is not limited thereto. The skilled person will acknowledge that the merits of the present invention may equally be beneficial in comparable hydraulic systems serving alternative purposes with nevertheless similar or otherwise comparable underlying techniques.

Yet another special application of the invention can be mentioned, in which two {or more) active devices, for example expansion devices, are provided, of which at least one is setin a degassing mode. In such a degassing mode, an amount of fluid is extracted from the system, degassed under a lower pressure in the expansion space, and degassed fluid is returned to the system. Another of the at least two active devices may then be adjusted by means of the invention to operate asynchronously, relative to the at least one in the degassing mode, i.e. to inject fluid into the system. Thereby, the goal may be pursued that no or hardly any pressure change occurs in the system during the degassing process, or at least a pressure drop due to the extraction of fluid to be degassed is as small as possible. Likewise, the injecting active device may then be adjusted to operate so as not to raise pressure in the system, and merely compensate for the extracted fluid as accurately as possible. The active devices may be specific degassing devices, such as pressure step degassers, wherein the fluid is brought to vacaum during such a cyclic degassing mode. Active devices may operate semi-continuously in complementary modes, as disclosed above, in particular during a start-up phase, where new fluid is inserted into a system, which may require degassing over a considerable start-up period.

It is noted here that the scope of protection for the developments described in the present disclosure are by no means limited to any particular feature of the embodiments described above and illustrated in the appended drawing.

The scope of protection is exclusively determined based on the limitations of the appended independent claims, but may, in some jurisdictions, even encompass obvious alternatives for features in the independent claims.

Other variations for specifically described elements, components and functionalities, that may also be embodied within the scope of the appended claims of the present disclosure, have been at least hinted at in the above embodiment description or the skilled person may be considered to be able to contemplate these variations within the range of this skilled person’s general knowledge.

This exemplary reference to alternative embodiments substantiates that any limitation to any specific feature, that is not defined as a limitation in the independent claims, is unwarranted.

Claims

CONCLUSIONS i. A hydraulic system comprising: fluid lines; a plurality of active devices, such as expansion pumps or compressor devices, in fluid communication with the fluid lines, for adjusting an operational parameter of the hydraulic system; and a controller, wherein at least one of the active devices comprises a fluid-based transmitter and at least one other of the active devices comprises a fluid-based receiver, for respectively transmitting and receiving at least one signal, through the fluid lines with the fluid therein as a transmission medium.

The hydraulic system of claim 1, wherein the controller communicates with the active device including the fluid-based transmitter and with the active device including the fluid-based receiver and is configured to transmit and receive the signal by respectively the fluid-based transmitter and the fluid-based receiver determine that the active device comprising the fluid-based transmitter and the active device comprising the fluid-based receiver are in fluid communication with each other through the fluid lines.

The hydraulic system of claim 1 or 2, wherein the signal comprises at least one signal from a group of signals, said group comprising: a pressure coded signal, a flow rate coded signal, an acoustic signal, an optical signal, an electrical signal, an electromagnetic signal .

A hydraulic system according to any one of the preceding claims, wherein the fluid-based transmitter and the fluid-based receiver are respectively arranged to transmit and receive the signal by manipulating and detecting manipulation of fluid pressure in the hydraulic system .

Hydraulic system according to any one of the preceding claims, wherein the control is adapted to select, in case of necessity of adjusting the operational parameter of the hydraulic system, at least one active device, which is in fluid communication with at least one at least one other active device, and controlling said at least one selected active device to adjust the operational parameter.

Hydraulic system according to claim 5, wherein the control is adapted to control the at least one selected device for injecting fluid into the hydraulic system or withdrawing fluid therefrom.

A hydraulic system according to claim 5 or 6, wherein the controller is further adapted to select the at least one selected active device based on an operational characteristic of said selected active device.

The hydraulic system of claim 7, wherein the operational characteristic comprises one of an expansion volume, an expansion capacity and a hysteresis characteristic of the selected active device,

Hydraulic system according to any one of claims 5 - 8, wherein the control is arranged for sending a control signal to the at least one selected active device for controlling said selected device.

The hydraulic system of claim 9, wherein the controller is configured to transmit the control signal to the at least one selected active device through the fluid lines, the fluid therein being the transmission medium.

A hydraulic system according to claim 9 or 10, further comprising a wired or wireless communication network, wherein the controller is adapted to transmit the control signal to the at least one selected active device via the communication network.

A hydraulic system according to any one of the preceding claims, wherein the hydraulic system comprises a sensor which is adapted to detect the operational parameter of the hydraulic system.

The hydraulic system of claim 12, wherein the sensor comprises a pressure sensor.

The hydraulic system of claim 5 and claim 12 or 13, wherein the hydraulic system is adapted to determine the need to adjust the operational parameter of the hydraulic system based on exceeding a predetermined range by the sensed operational parameter.

15. Hydraulic system according to any of the preceding claims, wherein the control is comprised by one of the active devices among the number of active devices.

16. Hydraulic system according to any of the preceding claims, wherein the control is adapted to control the active devices in opposite but complementary modes.

17. An active device of or for a hydraulic system according to any of the preceding claims.

A method of controlling a hydraulic system comprising fluid lines and a plurality of active devices, such as expansion pumps or compressor devices, in fluid communication with the fluid lines for adjusting an operational parameter of fluid in the lines, the method comprising: transmitting a signal at an active device comprising a fluid-based transmitter; and, receiving said signal at an active device comprising a fluid-based receiver, the signal being transmitted through the fluid conduits with the fluid therein as a transmission medium.

The method of claim 18, wherein the method, upon transmission and reception of the signal, further comprises: determining on the basis of the received signal that the active device comprising the fluid-based transmitter and the active device comprising the fluid-based receiver are in fluid communication with each other through the fluid lines.

The method of claim 18 or 19, wherein transmitting and receiving the signal comprises transmitting and receiving the at least one signal from a group of signals, said group comprising: a pressure coded signal, a flow rate coded signal, an acoustic signal , an optical signal, an electrical signal, an electromagnetic signal.

A method according to any one of the preceding claims 18 - 20, wherein transmitting the signal and receiving the signal respectively comprise manipulating and sensing the manipulation of fluid pressure in the hydraulic system.

A method according to any one of the preceding claims 18-21, wherein the method further comprises, in case of necessity of adjusting the operational parameter of the hydraulic system: selecting at least one active device that is in flaidum interconnection. stands with at least one other active device; and controlling said at least one selected active device to adjust the operational parameter.

The method of claim 22, wherein controlling said at least one selected device comprises injecting fluid into or withdrawing fluid from the hydraulic system.

The method of claim 22 or 23, wherein selecting the at least one active device in fluid communication with at least one other active device is based on an operational characteristic of said selected active device.

The method of claim 24, wherein the operational characteristic comprises one of an expansion volume, an expansion capacity and a hysteresis characteristic of the selected active device.

A method according to any one of claims 22 - 25, further comprising sending a control signal to the at least one selected active device for controlling said selected device.

The method of claim 26, wherein the transmitting comprises: transmitting the control signal to the at least one selected active device through the fluid lines, the fluid therein being the transmission medium.

The method of claim 26 or 27, wherein the transmitting comprises: transmitting the control signal to the at least one selected active device via a wired or wireless communication network.

A method according to any one of the preceding claims 18-28, further comprising sensing the operational parameter of the hydraulic system.

The method of claim 29, wherein sensing the operational parameter comprises sensing a fluid pressure in the hydraulic system.

The method of claim 22 and claim 29 or 30, further comprising determining the need to adjust the operational parameter of the hydraulic system by detecting the operational parameter exceeding a predetermined range.

A method according to any one of the preceding claims 18-31, further comprising driving the active devices in opposite but complementary modes.

A computer program comprising instructions for causing a controller according to any one of claims 1 to 17 to perform the steps of the method according to any one of claims 18 to 33.

A non-perishable computer readable medium that stores the computer program of claim 33.