Plasma generating system and method

Abstract

The plasma generating system (100) comprises a plasma generating device (104) connectable to a hub device (102). The plasma generating device (104) has an interface (106) for data communication with the hub device (102) and a step-up voltage generator (108) comprising an input connectable to a power source and an output connected to an electrode (116) for generating plasma. The plasma generating device (104) further has a sensor (120) arranged to measure one or more properties of the plasma generating device (104). A controller (122) is connected to interface (106), step-up voltage generator (108) and sensor (120). The controller (122) is configured to receive a control signal from the hub device (102) via the interface (106), receive measurement data from the sensor (120), and use the measurement data and the control signal to adjust the operation of the plasma generating device (104).

Description

[0001] PLASMA GENERATING SYSTEM AND METHOD

[0002] The present invention relates to a plasma generating system and method.

[0003] BACKGROUND

[0004] Plasma generating systems are used in a variety of applications. Plasma generating systems may be used to generate a variety of different types of plasma including thermal and nonthermal plasma. Nonthermal plasma, also known as cold plasma or low-temperature plasma, is being investigated for applications included the antimicrobial treatment of food products, the sterilization of medical devices, and the generation of plasma activated liquid. An example nonthermal plasma will have electrons with temperatures exceeding 5000°C and heavy neutral particles with a temperature less than 100°C.

[0005] Plasma generating systems typically comprise a time-varying power source that generates a high voltage (e.g., >500 V) and low current (e.g., <10 A) output. The power source is connected to one or more conductive (e.g., metallic) electrodes. A time varying electric field is applied across the electrodes resulting in the formation of plasma. Under atmospheric pressure operating conditions, nonthermal plasma is inherently unstable and rapidly transitions into a damaging thermal (arc) plasma. To overcome this challenge, a dielectric barrier can be inserted between the electrodes to limit the flow of current which acts to prevent arcing.

[0006] Some example plasma generating systems comprise a transformer having a primary coil connected to a power source and a secondary coil connected to a high voltage electrode. A dielectric is arranged between the high voltage electrode and a ground electrode. A time varying electric field is applied across the electrodes resulting in the formation of plasma.

[0007] There is a need to control the generation of plasma by the plasma generating system. Incorrect operation can lead to ineffective plasma generation, arcing, and can accelerate the degradation of components of the system leading to increased downtime and maintenance.

[0008] SUMMARY

[0009] According to the present invention, there is provided a plasma generating system, method and computer program as set out in the accompanying independent claims. Other aspects of the disclosure are apparent from the dependent claims and the description which follows.

[0010] According to a first aspect of the disclosure, there is provided a plasma generating system. The plasma generating system comprises a hub device connectable to a plurality of plasma generating devices. The hub device comprises an interface for data communication with the plurality of plasma generating devices. The hub device comprises a controller. The controller is configured to obtain contextual data from the plurality of plasma generating devices indicative of the operational conditions of the plasma generating system. The controller is configured to process the contextual data to determine whether there is a change in the operational conditions of the plasma generating system. In response to determining there is a change in the operational conditions of the plasma generating system, the controller is configured to cause one or more of the plasma generating devices to adjust one or more properties of their plasma generation.

[0011] Advantageously, a hub device is provided for controlling a plurality of plasma generating devices which operate to generate plasma such as for decontaminating an object. The plurality of plasma generating devices are part of the plasma generating system. The hub device obtains contextual data from the plurality of plasma generating devices and uses the contextual data to determine whether there is a change in the plasma generating system. Responsive to this, the hub device can adjust properties of the plasma generating by the plasma generating devices. The hub device can therefore make system- wide or local adjustments to the plasma generation considering the performance of the entire system. In this way, the plasma generating devices can be controlled to alter their plasma generation based on changes in operational conditions that may not be detectable by individual plasma generating devices. The hub device may only adjust properties of a subset of the plasma generating devices. This subset may be identified based on the determined change in the operational conditions. For example, the hub device may only adjust properties of plasma generating devices that are affected by the change in operational conditions or that can compensate for the change in operational conditions.

[0012] The change in the operational conditions may comprise a change in the characteristics of the plasma generating devices and / or a change in the environment of the plasma generating system.

[0013] The change in the characteristics of the plasma generating devices may comprise a change in the performance of one or more of the plasma generating devices.

[0014] Advantageously, the hub device is able to determine whether there has been a change in the performance of one or more of the plasma generating devices and adjust the properties of plasma generation accordingly. The hub device may adjust the performance of just the plasma generating devices identified as having a change in performance or may adjust other ones of the plasma generating devices such as to compensate for the change in performance of the affected plasma generating devices.

[0015] The change in the performance of the one or more plasma generating devices may comprise the performance of the one or more plasma generating devices moving outside of a predetermined performance range. The performance range may comprise an output voltage range, operating frequency, output current range, temperature range, optical emission intensity, or a change in one or more properties of the generated plasma such as a change in the type of plasma species or a plasma species concentration range.

[0016] The change in the performance of the one or more plasma generating devices may comprise a fault being present in the one or more plasma generating devices.

[0017] Advantageously, the hub device is able to detect, from the received contextual data, whether a fault is present in a plasma generating device. The hub device can reconfigure the operation of the plasma generating devices based on the detected fault such as to isolate the plasma generating device with the fault, and increase the operational power of one or more of the other plasma generating devices in compensation. In this way, the system is able to continue operating effectively even if a subset of the plasma generating devices develop faults.

[0018] The controller may be configured to cause the one or more plasma generating devices associated with the fault to adjust one or more properties of their plasma generation.

[0019] The controller may be configured to cause the one or more plasma generating devices associated with the fault to adjust their operating power. The controller may be configured to cause the one or more plasma generating devices associated with the fault to decrease their operating power. Decrease their operating power may comprise isolating the affected plasma generating device such that it is not powered to generate plasma. The controller may be configured to cause one or more other plasma generating devices to adjust one or more properties of their plasma generation. The adjustment to one or more properties may compensate for the adjustment made to the plasma generating devices associated with the fault. The controller may be configured to cause the one or more other plasma generating devices to adjust their operating power. The controller may be configured to cause the one or more other plasma generating devices to increase their operating power.

[0020] The change in the characteristics of the plasma generating devices may be due to a plasma generating device being added to the system. The controller may be configured to cause the plasma generating device added to the system to adjust one or more properties of its plasma generation.

[0021] Advantageously, the plasma generating system supports plasma generating devices being removed and replaced. The system is modular and as such the entire system does not need to be decommissioned if one of the plasma generating devices develops a fault. The hub device adjusts the operation of the newly added plasma generating device, such as to gradually increase the operational power of the plasma generating device to acclimatise the plasma generating device to the ambient environment of the system.

[0022] The change in the operational conditions may comprise a change in the environment of the plasma generating system. The change in the environment may comprise a change in the ambient environment such as the ambient temperature, pressure, and / or humidity at the location of the plasma generating system.

[0023] The change in the environment may comprise a change in a property of an object external to the plasma generating devices. The object may comprise an object to be treated (e.g., decontaminated and / or functionalised) by the plasma generating devices. The change in the property of the object comprises one or more of a change in the type of the object, a condition of the object, and a spatial relationship between the object and the plasma generating devices.

[0024] The hub device may adjust the operation of one or more of the plasma generating devices based on a change in a property of the object. A change in the type of the object may mean that a property of the plasma such as the type and concentration of reactive chemical species present in the plasma needs to be adjusted. A change in the type of the object may mean that higher or lower energy plasma is required. A change in the condition of the object may indicate that the object includes debris / contaminants, the level of debris / contaminants on the object, or the level of degradation of the object. A change in the condition of the object may mean that higher or lower power plasma is required.

[0025] A change in a property of the object may comprise a change in the spatial relationship between the object and the plasma generating devices. This may include a change in the distance between the object and the plasma generating device, and / or a change in the speed of the object (such as a conveyor) relative to the plasma generating device. The controller may be configured to cause the one or more plasma generating devices to adjust one or more properties of their plasma generation in response to determining that the object is less than a predetermined distance from the plasma generating devices.

[0026] The object may comprise a conveyor of a conveyor system.

[0027] The controller being configured to cause the one or more plasma generating devices to adjust one or more properties of their plasma generation may comprise the controller being configured to cause the one or more plasma generating devices to adjust one or more of their operating power for plasma generation, their operating voltage for plasma generation, their operating frequency for plasma generation, their operating duty cycle for plasma generation, their distance from an object to be decontaminated by the plasma generating device, the rate at which plasma generated species are extracted, and the temperature of one or more of the electrodes.

[0028] Changing the rate at which plasma generating species are extracted may comprise controlling an extraction unit of the plasma generating system to adjust the extraction rate of the system.

[0029] The controller may be configured to select, based on the change in the operational conditions, the one or more plasma generating devices to be caused to adjust the one or more properties of their plasma generation.

[0030] The contextual data may comprise a compressed representation of measurement data captured by the plasma generating devices.

[0031] The plasma generating system may comprise the plurality of plasma generating devices.

[0032] The plurality of plasma generating devices may each comprise: an interface for data communication with the hub device; a step-up voltage generator comprising an input connectable to a power source and an output connected to an electrode for generating plasma; and a controller connected to the interface and the step-up voltage generator, the controller configured to supply a drive signal to the step-up voltage generator.

[0033] The step-up voltage generator is arranged to receive an input voltage from the power source and generate an output voltage having a higher voltage than the input voltage. The step-up voltage generator may be referred to as a high-voltage generator. The step-up voltage generator may comprise a transformer, such as an iron, ferrite, or air-cored transformer, a voltage multiplier, a RF transistor, or a pulse generator such as a Marx bank generator. The step-up voltage generator may comprise a transformer. The transformer may comprise a primary coil connectable to a power source and a secondary coil connected to the electrode for generating plasma. The controller may be configured to supply the drive signal to the primary coil of the transformer.

[0034] The controller may be configured to receive a control signal from the hub device via the interface, and use the control signal to adjust one or more properties of the drive signal supplied to the step-up voltage generator.

[0035] Each plasma generating device may further comprises a sensor arranged to measure one or more properties of the plasma generating device. The controller may be configured to receive the measurement data from the sensor, and use the measurement data and the control signal to adjust one or more properties of the drive signal. One or more of the plasma generating devices may comprise a plurality of sensors.

[0036] The one or more properties of the plasma generating device may comprise one or more of an electrical property of the plasma generating device, a thermal property of the plasma generating device, a chemical property of the plasma generated by the plasma generating device, a structural property of the plasma generating device, and a spatial relationship between the plasma generating device and an external object.

[0037] According to a second aspect of the disclosure, there is provided a method performed by a plasma generating system. The method comprises obtaining, by a hub device of the plasma generating system, contextual data from a plurality of plasma generating devices, the contextual data indicative of the operational conditions of the plasma generating system. The method comprises processing, by the hub device, the contextual data to determine whether there is a change in the operational conditions of the plasma generating system. In response to determining there is a change in the operational conditions of the plasma generating system, the method comprises causing, by the hub device, one or more of the plasma generating devices to adjust one or more properties of their plasma generation.

[0038] According to a third aspect of the disclosure, there is provided a computer program having instructions recorded thereon which, when executed by one or more processors, cause the one or more processors to perform the method of the second aspect of the disclosure.

[0039] According to a fourth aspect of the disclosure, there is provided a plasma generating system. The plasma generating system comprises a plasma generating device connectable to a hub device. The plasma generating device comprises an interface for data communication with the hub device. The plasma generating device comprises a step-up voltage generator comprising an input connectable to a power source and an output connected to an electrode for generating plasma. The plasma generating device comprises a sensor arranged to measure one or more properties of the plasma generating device. The plasma generating device comprises a controller connected to the interface, the step-up voltage generator, and the sensor. The controller is configured to receive a control signal from the hub device via the interface, receive measurement data from the sensor, and use the measurement data and the control signal to adjust the operation of the plasma generating device. Advantageously, the plasma generating device is connectable to a host device so as to receive a control signal from the host device. The control signal specifies adjustments to the operation of the plasma generating device such as to change the nature of the plasma generation. The control signal may be determined, at least in part, based on factors not measurable by the plasma generating device such as the operational conditions of other plasma generating devices in the plasma generating system, and predetermined plasma generation requirements for the system such as may be set by a human operator. Moreover, the controller adjusts the operation of the plasma generating device based on measurement data received from the sensor. This enables the controller to react to the current operational conditions of the plasma generating device. In this way, the controller can fine-tune operation of the plasma generating in real-time based on locally measured data. The combination of control from a host device and local control using local sensors helps enable effective control of the plasma generating device ensuring treatment uniformity across the entire plasma generating array.

[0040] The controller being configured to adjust the operation of the plasma generating device may comprise the controller being configured to adjust one or more properties of a drive signal supplied to the step- up voltage generator.

[0041] Advantageously, modifying the drive signal modifies the waveform output from the step-up voltage generator which in turn modifies the generation of plasma via the electrode. The output waveform causes a time varying electric field to be applied across the electrode and a ground electrode such that plasma is generated in a gap between the electrodes. A dielectric is typically arranged in the gap but is not required in all examples.

[0042] The step-up voltage generator is arranged to receive an input voltage from the power source and generate an output voltage having a higher voltage than the input voltage. The step-up voltage generator may be referred to as a high-voltage generator. The step-up voltage generator may comprise a transformer, such as an iron, ferrite, or air-cored transformer, a voltage multiplier, a RF transistor, or a pulse generator such as a Marx bank generator.

[0043] The step-up voltage generator may comprise a transformer. The transformer may comprise a primary coil connectable to a power source and a secondary coil connected to the electrode for generating plasma. The controller may be configured to supply the drive signal to the primary coil of the transformer. The plasma generating device may further comprise a power converter. The controller may supply the drive signal to the step-up voltage generator via the power converter. For example, if the step-up voltage generator comprises a transformer, the power converter may convert a DC signal received from the power source to an AC signal for supply to the primary coil of the transformer. The controller may control the switching frequency of the power converter to change the nature of the AC signal supplied to the primary coil of the transformer.

[0044] The one or more properties of the drive signal may comprise one or more of the amplitude, frequency, and duty cycle of the drive signal.

[0045] The controller being configured to adjust the operation of the plasma generating device may comprise the controller being configured to adjust the rate at which plasma generated species are extracted (e.g., locally to the plasma generating device), and / or the temperature of the electrode(s) of the plasma generating device. The plasma generating device may comprise a temperature control unit attachable to the electrode(s). The temperature control unit may be controllable by the controller to adjust the temperature of the electrode(s).

[0046] The controller may be configured to adjust the operation of the plasma generating device in response to determining that the measurement data indicates that a property of the plasma generating device is not within a predetermined range.

[0047] Advantageously, the controller is able to use feedback loops to control the generation of plasma in realtime based on the measurement data. This enables the plasma generating device to work effectively, such as to meet the requirements set by the control signal received from the host device. The control signal may for example, set of range for the properties of the drive signal, such as an amplitude range, frequency range, and duty cycle range. The controller may fine tune the particular amplitude, frequency, and duty cycle within the range based on the measurement data.

[0048] The one or more properties of the plasma generating device may comprise one or more of a characteristic of a component of the plasma generating device, a spatial relationship between the plasma generating device and an external object, and a characteristic of plasma generated by the plasma generating device.

[0049] The characteristic of a component of the plasma generating device may comprise a structural characteristic of a component of the plasma generating device.

[0050] Advantageously, the sensor is arranged to measure the structural characteristic of a component of the plasma generating device such as to determine whether flaws are developing in the component due to stress or impact from an external object. The component may develop flaws due to excessive heat build-up during plasma generation or due to impact from debris in a factory environment such as a food processing environment. The controller is able to detect these structural changes in the component and adjust control operations, such as to reduce the power of plasma generation or disable plasma generation before the component is irreversibly damaged / fragments.

[0051] The structural characteristic of a component of the plasma generating device may comprise a structural characteristic of a dielectric of the plasma generating device.

[0052] The dielectric may be arranged in close proximity to an object to be decontaminated such as a conveyor in a food processing factory. Flaws in the dielectric due to excessive heat build-up or impact from an item of debris could lead to fragmentation of the dielectric which may result in dielectric fragments depositing on the conveyor. This is undesirable as it could lead to contamination of foodstuffs transported by the conveyor. To avoid this, the sensor is able to measure the structural characteristics of the dielectric and identify if heat-stresses or impact damage have occurred. The controller may then proactively control the plasma generation to prevent fragmentation. The plasma generating device may then be removed from the system for maintenance at an appropriate time. The sensor may comprise a strain sensor to measure the structural characteristic of the component of the plasma generating device. The strain sensor may comprise a piezoelectric sensor.

[0053] The controller may be arranged to process the measurement data received from the sensor so as to determine whether a change in the structure of the component has occurred. The controller may be arranged to process the measurement data to identify the type of structural change and / or a location of the structural change on the component. The controller may be arranged to use machine-learning algorithms such as convolutional neural networks to process the measurement data and determine the type of structural change and / or a location of the structural change. The machine-learning algorithms may be trained, at least in part, by measuring the temperature of a dielectric of a plasma generating device using a thermal camera to map the temperature at different locations of the dielectric. The model can then be trained to determine the relationship between measurement data received from the sensor (e.g., strain sensor) and the known temperature measurements from the thermal camera.

[0054] The piezoelectric sensor may comprise a piezoelectric wafer active sensor. The piezoelectric wafer active sensor may comprise an actuator component arranged to transmit guided waves and a sensing component arranged to detect the guided waves after they have passed through at least part of the component (e.g., the dielectric).

[0055] The actuator component and sensing component may be distributed around the perimeter of the component (e.g., the dielectric). The actuator component and sensing component may be spaced apart from the electrode.

[0056] The characteristic of the spatial relationship between the plasma generating device and the external object may comprise the distance between a dielectric of the plasma generating device and the external object.

[0057] Advantageously, the controller is able to detect, from the measurement data, whether an object is less than a threshold distance from the plasma generating device and adjust the operation of the plasma generating device accordingly.

[0058] Responsive to determining that the object is less than a threshold distance from the plasma generating device, the controller may be arranged to adjust one or more properties of the drive signal so as to decrease the power of the output waveform so as to decrease the power of the generated plasma. This helps avoids damage caused by high energy plasma being generated when an object is in proximity to the plasma generating device and, in particular, a dielectric of the plasma generating device.

[0059] The sensor may comprise a proximity sensor arranged to measure the proximity of objects to the dielectric. The controller may be arranged to process the measurement data received from the proximity sensor so as to determine whether an object is less than a predetermined distance from the dielectric. The proximity sensor may comprise a time-of-flight sensor.

[0060] The characteristic of a component of the plasma generating device may comprise an electrical characteristic of a component of the plasma generating device. The sensor may comprise an electrical sensor arranged to measure one or more electrical properties of an output waveform of the secondary coil. The one or more properties of the output current may comprise one or more of the voltage, frequency and current of the output waveform.

[0061] The characteristic of a component of the plasma generating device may comprise a temperature characteristic of a component of the plasma generating device.

[0062] The sensor may comprise a temperature sensor arranged to measure the temperature of one or more components of the plasma generating device.

[0063] The temperature sensor may comprise a thermal camera positioned such that its field of view captures a plurality of components of the plasma generating device.

[0064] The characteristic of plasma generated by the plasma generating device may comprise a characteristic of the reactive chemical species present in the plasma generating device.

[0065] The sensor may comprise a detector arranged to detect reactive chemical specifies in the generated plasma. The detector may comprise a spectrometer. The detector may comprise an electrochemical cell. The detector may comprise an optical sensor.

[0066] The detector may be arranged to detect the type of reactive chemical species in the generated plasma, such as whether the excited reactive chemical species comprise reactive nitrogen chemical species or reactive oxygen chemical species. The detector may be arranged to detect the concentration of one or more types of reactive chemical species. The controller may be arranged to compare the detected type and / or concentration to expected values for the plasma generation application. The controller may be arranged to adjust the operation of the plasma generating device accordingly so as to promote generation of the desired type of reactive chemical species. The controller may be arranged to adjust the operation of the plasma generating device so as to suppress generation of an undesired type of reactive chemical species.

[0067] The plasma generating device may be a first plasma generating device, and the system may comprise a plurality of plasma generating devices including the first plasma generating device. Each of the plurality of plasma generating devices may be connectable to the hub device.

[0068] Advantageously, the system can comprise a plurality of plasma generating devices each connectable to the hub device and configured to control their operation based on a control signal from the hub device and measurement data obtained locally. The plurality of plasma generating devices could be used to collectively generate plasma for decontaminating an object that would be impractical to decontaminate using a single plasma generating device. The plurality of plasma generating devices may each receive an independent control signal from the host device. That is, each of the plurality of plasma generating devices is capable of receiving a different control signal from the host device.

[0069] The plasma generating system may further comprise a support structure on which the plurality of plasma generating devices are retained. Advantageously, the support structure may hold the plasma generating devices in fixed positions relative to one another. The plasma generating devices may be held on the support structure in an arrangement such that, collectively, they can generate plasma to cover the full width of an object to be decontaminated (such as a conveyor) without any or only minimal gaps in plasma generation. This helps ensure uniform and effective plasma treatment of the object.

[0070] The plurality of plasma generating devices may be releasably attached to the support structure. This enables plasma generating devices to be easily removed and replaced.

[0071] The support structure may be arranged to be positioned in close proximity to an object to be decontaminated. The object may comprise a conveyor of a conveyor system. The plurality of plasma generating devices may generate plasma for decontaminating the conveyor. The support structure may be attached to a frame of the conveyor system that carriers the conveyor. The plasma generating system may comprise the conveyor system. Advantageously, the support structure holds the plasma generating devices, and in particular, dielectrics of the plasma generating devices in close proximity to the conveyor such that plasma is generated in the gap between the conveyor and the dielectric. The generated plasma can clean and decontaminate the conveyor. This provides an efficient method of decontaminating the conveyor compared to existing approaches which require the conveyor system to be shut down and pressure washed. The plasma generating system of the present disclosure enables the conveyor to be decontaminated while the conveyor is fulfilling its intended purpose, such as carrying items of food in a food processing factory.

[0072] The plasma generating device may comprise an NFC tag comprising an antenna and a data store. The data store may be arranged to store configuration information received from an NFC writer brought into proximity with the antenna. The data store may be coupled to the controller such that the controller is able to read the configuration information from the data store.

[0073] The controller may be arranged to write data to the data store. The data may comprise contextual data indicative of the operational conditions of the plasma generating device / system. The contextual data may include information about the characteristics of plasma generated by the plasma generating device. Advantageously, plasma characteristics can be stored in the data store to enable the operator to recover information on plasma composition at a later date. This enhances traceability.

[0074] Advantageously, the plasma generating device comprises an NFC tag that enables configuration information to the written to the data store so as to, for example, set-up the plasma generating device when it is first deployed to the plasma generating system. The configuration information may include, for example, a communication address used by the hub device to communicate with the plasma generating device. This approach requires minimal human intervention and does not require the plasma generating device to be powered via the hub device at the time of writing the configuration information.

[0075] The NFC tag may be positioned in a housing of the plasma generating device.

[0076] The housing comprises may comprise visual indicator so as to visually indicate the location of the antenna of the NFC tag. The controller may be arranged to send, via the interface, data to the hub device. The data may comprise contextual data indicative of the operational conditions of the plasma generating system.

[0077] Advantageously, the plasma generating device is able to report back information to the hub device about the operational conditions of the plasma generating system, and in particular the operational conditions of the plasma generating device. The hub device may use this information to update the control signal supplied to the plasma generating device.

[0078] The contextual data may comprise a compressed representation of the measurement data received from the sensor. Advantageously, this reduces the amount of raw data required to be transmitted to the hub device.

[0079] The plasma generating system may comprise the hub device. The hub device may comprise an interface for data communication with the plasma generating device. The hub device may comprise a controller configured to: obtain contextual data from the plasma generating device indicative of the operational conditions of the plasma generating system; process the contextual data to determine whether there is a change in the operational conditions of the plasma generating system; and in response to determining there is a change in the operational conditions of the plasma generating system, cause the plasma generating device to adjust one or more properties of its plasma generation.

[0080] The hub device may be arranged to generate the control signal for the plasma generating device based on the determined change in the operational conditions of the plasma generating system, and send the control signal to the plasma generating device.

[0081] According to a sixth aspect of the disclosure, there is provided a method for generating plasma by a plasma generating system. The method comprises receiving, by a plasma generating device of the plasma generating system, a control signal from a hub device. The method comprises obtaining, by the plasma generating device, measurement data from a sensor of the plasma generating device. The method comprises using, by the plasma generating device, the control signal and the measurement data to adjust the operation of the plasma generating device.

[0082] Using the control signal and the measurement data may comprise adjusting one or more properties of a drive signal based on the control signal and the measurement data, and supplying the drive signal to a step-up voltage generator of the plasma generating device so as to control the output of the step-up voltage generator coupled to an electrode for generating plasma.

[0083] According to a seventh aspect of the disclosure, there is provided a computer program having instructions recorded thereon which, when executed by one or more processors, cause the one or more processors to perform the method of the second aspect of the disclosure.

[0084] BRIEF DESCRIPTION OF DRAWINGS

[0085] Figure 1 shows a simplified schematic diagram for an example plasma generating system according to aspects of the present disclosure.

[0086] Figure 2 shows a flow diagram for an example method according to aspects of the present disclosure. Figure 3 shows a flow diagram for an example method according to aspects of the present disclosure.

[0087] Figure 4 shows a perspective view of an example plasma generating device according to aspects of the present disclosure.

[0088] Figure 5 shows a view of the bottom surface of the plasma generating device of Figure 4.

[0089] Figure 6 shows a view of the bottom surface of the plasma generating device of Figure 4 with the dielectric and encapsulant removed.

[0090] Figure 7 shows a perspective view of the plasma generating device of Figure 4. The housing is transparent in the drawing to show internal components of the plasma generating device.

[0091] Figure 8 shows a perspective view of an example plasma generating system according to aspects of the present disclosure.

[0092] Figure 9 shows a side view of the plasma generating system of Figure 8.

[0093] Figure 10 and 11 show views of the plurality of plasma generating devices mounted on a support structure in the plasma generating system of Figure 8.

[0094] DETAILED DESCRIPTION

[0095] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the disclosure as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the disclosure. In addition, descriptions of well-known functions and constructions may be omitted for clarity and conciseness.

[0096] The terms and words used in the following description and claims are not limited to the bibliographical meanings but are merely used by the inventor to enable a clear and consistent understanding of the disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the disclosure is provided for illustration purpose only and not for the purpose of limiting the disclosure as defined by the appended claims and their equivalents.

[0097] It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0098] Referring to Figure 1 , there is shown a simplified schematic diagram of an example plasma generating system 100 according to aspects of the present disclosure.

[0099] The plasma generating system 100 comprises a hub device 102 and a plurality of plasma generating devices 104 that are connected to the hub device 102. The plasma generating devices 104 generate plasma. The plasma is typically nonthermal plasma, but is not required to be. In the examples described below, the hub device 102 is a dedicated control device for the plasma generation system 100. This is not required in all examples, the hub device 102 may be a plasma generating device 104. In other words, the plurality of plasma generating devices 104 may form a type of mesh network where one of the plasma generating devices 104 acts as the hub device 102.

[0100] The hub device 102 comprises an interface 105. The plasma generating devices 104 each comprise an interface 106 that couples to the interface 105 of the hub device 102 such as via one or more wired connections. The interfaces 105, 106 permit data communication between the hub device 102 and the plasma generating devices 104.

[0101] In this example, the plasma generating devices 104 also receive power from the hub device 102 via interfaces 105, 106. The hub device 102 is typically connected to a mains power supply and has power conversion circuitry such as an AC-to-DC converter so that DC power is supplied to the plasma generating devices 104. The hub device 102 may comprise distribution circuitry such that each plasma generating device 104 receives a separate DC power supply. The hub device 102 may be able to adjust the power level of the individual power supplies to the plasma generating devices 104 such that the plasma generating devices 104 are able to operate at different input power levels.

[0102] In other examples, the plasma generating devices 104 may receive power from power source(s) separate to the hub device 102 such as by being directly connectable to a mains power supply. The plasma generating devices 104 in these examples may include power conversion circuitry such as AC- to-DC converters.

[0103] The plasma generating devices 104 each comprise a transformer 108. The transformer 108 comprises a primary coil 110 that is connected a power source. In this example, the primary coil 110 is connected to the power source of the hub device 102 via the interface 106. The transformer 108 further comprises a secondary coil 112. The secondary coil 112 is connected to a high voltage electrode 114 ofthe plasma generating device 104.

[0104] While the plasma generating devices 104 shown in the drawings include a transformer 108, it will be appreciated that this is just one form of step-up voltage generator that may be used to generate a high voltage output from a lower voltage input. The skilled person may select, as appropriate, any step-up voltage generator, for transforming a low voltage to a high voltage regardless of frequency. The input voltage to the step-up voltage generator may be, for example, a DC voltage, an AC voltage with a frequency in the kHz range, an AC voltage with a frequency in the MHz range, an AC voltage with a frequency in the GHz range, or a pulsed voltage signal. Examples of step-up voltage generators include transformers (e.g., iron, ferrite, or air-cored transformerjm voltage multipliers, RF transistors, and pulse generators. A dielectric 116 is arranged between the electrode 114 and a ground electrode 118. The dielectric 116 may be part of the plasma generating device 104 or may be separate to the plasma generating device 104. The ground electrode 118 may be part of the plasma generating device 104 or may be separate to the plasma generating device 104.

[0105] A dielectric 116 is not always required depending, for example, on the method used for plasma generation. For example, if pulsed or RF excitation is used then a dielectric may not be required. Furthermore, a dielectric 116 may not be required if the object to be treated by the generated plasma is able to function as a dielectric. For example, a polymeric conveyor belt would avoid the need for a separate dielectric.

[0106] The plasma generating devices 104 each comprise one or more sensors 120 arranged to measure one or more properties of the plasma generating device 104.

[0107] The plasma generating devices 104 each comprise a controller 122. The controller 122 of each plasma generating device 104 is connected to the transformer 108 via a power converter 122. The controller 122 is arranged to generate a drive signal which is applied, via the power converter 124, to the primary coil 110 of the transformer 108. The output current generated by the secondary coil 112 causes a timevarying electric field to be applied across the dielectric 116 leading to the generation of plasma. The plasma generating device 104 in this example generates plasma through dielectric barrier discharge. Other plasma generating arrangements such as surface barrier discharge, radio frequency plasma generators, microwave plasma generators, and pulsed plasma generators are possible.

[0108] The controller 122 is connected to the interface 106 so that the controller 122 is able to communicate with the hub device 102. The controller 122 sends contextual data relating to the operation of the plasma generating device 104 to the hub device 102. The contextual data characterises the operational conditions of the plasma generating system 100. The plasma generating devices 104 may send aggregated (processed) data to the host device 102 to reduce the need for raw data transmission. This compressed representation may include metrics such as plasma output, voltage, current, temperature, and any alerts or abnormalities detected by the plasma generating device 104. By analysing this data, the hub device 102 can generate an overview of the performance of the plasma generating system 100 and make informed decisions for system wide optimisation. This includes performing predictive analytics to identify trends that might indicate wear and tear or potential system failure.

[0109] The hub device 102 process the contextual data to determine whether there is a change in the operational conditions of the plasma generating system 100. The change in the operational conditions could comprise a change in the characteristics of the plasma generating devices and / or a change in the environment of the plasma generating system 100.

[0110] In response to determining there is a change in the operational conditions of the plasma generating system 100, the hub device 102 causes one or more of the plasma generating devices 104 to adjust one or more properties of their plasma generation. The one or more properties could comprise one or more of an operating power for plasma generation, an operating frequency for plasma generation, an operating duty cycle for plasma generation, a temperature of the electrode 114, and a distance between the plasma generating device and an external object.

[0111] Changing the operating power may comprise causing the plasma generating device(s) 104 to operate at a higher or lower power. This may involve the hub device 102 modifying a power level of the input power supplied to the plasma generating device(s) 104 and / or may involve the hub device 102 sending a control signal to the controller 122 of the plasma generating device 104 to cause the plasma generating device 104 to change its operating power or frequency. For example, if a transformer 108 is used as the step-up voltage generator, moving away from the resonant frequency can have the effect of reducing the power without requiring a change in the input voltage supplied to the transformer.

[0112] Changing the operating frequency or duty cycle for plasma generation may comprise the hub device 102 sending a control signal to the controller 122 of the plasma generating device(s) 104. The controller 122 may modify the drive signal supplied to the primary coil 110 of the transformer 108 such as to change the frequency and / or duty cycle of the drive signal. This changes the output waveform generated by the transformer 108 which in turn changes properties of the generated plasma.

[0113] The hub device 102 therefore obtains contextual data characterising the operational conditions of the plasma generating system 100 and uses the contextual data to adjust the plasma generation by the plasma generating devices 104 considering the overall performance of the system 100.

[0114] The change in the characteristics of the plasma generating devices 104 could comprise a change in the performance of one or more of the plasma generating devices 104 such as the one or more plasma generating devices 104 falling outside of a predetermined performance range or a fault developing in the one or more plasma generating devices 104.

[0115] In some examples, the contextual data may, for example, indicate that the affected plasma generating device 104 is experiencing voltage fluctuations beyond acceptable limits. In response to this, the hub device 102 may cause the affected plasma generating device 104 to operate at a lower power and may also increase the power of other ones of the plasma generating devices 104 to compensate for the decrease in plasma generation by the affected plasma generating device 104. The hub device 102 may also schedule maintenance to be performed on the affected plasma generating device 104 at a suitable time such as the end of a shift in a factory in which the system 100 is located.

[0116] In some examples, the contextual data may indicate that a plasma generating device 104 has developed a fault. The hub device 102 may, for example, reduce the power of the plasma generating device 104 reporting the fault. The power may be reduced such that it is no longer operating to generate plasma or is generating plasma at a lower energy. The hub device 102 may control other plasma generating devices 104 to increase their power to counteract the faulty plasma generating device 104. At an appropriate time, the plasma generating device 104 reporting the fault can then be manually inspected and repaired or replaced if needed.

[0117] In some examples, if the contextual data is indicative of a critical fault in one or more of the plasma generating devices 104, the hub device 102 can isolate the affected plasma generating devices 104 and reconfigure the rest of the system 100 to continue operating safely. The hub device 102 can also manage emergency shutdowns with the gradual ramping up or down of plasma power to avoid sudden system shocks or potential damage.

[0118] In some examples, the contextual data indicates that a plurality of plasma generating devices 104 are not operating within an acceptable range of performance conditions. For example, the affected plasma generating devices 104 may be operating at a higher than expected temperature or have components, such as their transformers 108, that are operating at a higher than expected temperature. The hub device 102 can use this contextual data to predict when maintenance will be required and schedule maintenance for an appropriate time. This helps to reduce unplanned downtime and improves the longevity of the plasma generating system 100 by catching issues earlier than that of a human operative or simple visual inspection.

[0119] As the hub device 102 is receiving contextual data from the plurality of plasma generating devices 104, the hub device 102 can perform comparative analysis to identify if any of the plasma generating devices 104 are operating outside of expected tolerances. The hub device 102 can then automatically adjust the operation of the affected plasma generating device 104 to bring it back in line with expected tolerances.

[0120] In some examples, one of the plasma generating devices 104 may be reporting back a higher measurement, such as an output voltage measurement for their transformer 108, than the other plasma generating devices 104. The hub device 102 can compare the properties of the plasma generating device 104 to the other plasma generating devices 104 of the system 100. This can include identifying whether the affected plasma generating device 104 is from the same production batch as the other plasma generating devices 104, identifying whether components, such as a voltage sensor, of the plasma generating device 104 have the same tolerance as the other plasma generating devices 104, and identifying whether the input power to the affected plasma generating device 104 is the same as the other plasma generating devices 104. Using this information, the hub device 102 can identify whether the affected plasma generating device 104 is operating erroneously or if the sensor is inaccurate.

[0121] If the hub device 102 identifies that the sensor reading is inaccurate, the hub device 102 can cause the affected plasma generating device 104 to perform a calibration operation, or the hub device 102 can supply a correction factor to the affected plasma generating device 104 so as to adjust the sensor readings. In this way, the system 100 is able to continue to operate avoiding unnecessary downtime and maintenance.

[0122] The hub device 102 may store the contextual data for future analysis. The hub device 102 may update algorithms used by the hub device 102 for controlling the system 100 based on the contextual data. The contextual data may be used to build machine-learning models to aid with predictive maintenance. These models can be deployed to the hub device 102 or on a remote device.

[0123] The change in the characteristics of the plasma generating devices could comprise a change in the configuration of one of more of the plasma generating devices 104 such as due to a plasma generating device 104 being removed from the plasma generating system 100 and replaced.

[0124] The hub device 102 can processes the contextual data to determine that a new plasma generating device 104 has been added to the system and can intelligently manage the integration of the new plasma generating device 104. The hub device 102 may control the new plasma generating device 104 to operate at a different power level than the other plasma generating devices 104 in the system 100. This is beneficial if the new plasma generating device 104 has a lower runtime than the existing plasma generating devices 104 and has not yet stabilised to match the operating conditions of the system 100. In this example, the hub device 102 may override local control mechanisms implemented in the new plasma generating device 104 or may supplement the local control mechanisms such as by applying a correlation factor. This allows the plasma generating device 104 to gradually align with the thermal and operational parameters of the overall system 100. Once the new plasma generating device 104 reaches the operating consistency of the other plasma generating device 104, the hub device 102 can relinquish direct control, allowing local control mechanisms of the plasma generating device 104 to resume normal operation. Overall, this allows this extends the overall operational life of all plasma generating devices 104 within the system 100.

[0125] The change in the environment of the plasma generating system 100 could comprise a change in the ambient environmental conditions, such as a change in the ambient pressure, temperature, and / or humidity at the location of the plasma generating system 100. The hub device 104 may adjust the operation of the plasma generating devices 104 based on these changes in ambient environmental conditions. The plasma generating system 100 may comprise ambient environmental sensors to measure these changes in environmental conditions or may derive these environmental changes based on changes in measurement data from other sensors 120.

[0126] The contextual data may therefore be indicative of the environmental conditions in the location of the system. For example, the contextual data may be indicative of a change in the ambient environment such as the ambient temperature, pressure, or humidity. The hub device 102 may process the contextual data to determine whether a change in the environmental conditions has occurred and generate a control signal accordingly.

[0127] The change in the environment could comprise a change in a property of an object external to the plasma generating devices 104. The object may be an object to be decontaminated by the plasma generating devices 104. The change in the property of the object comprises one or more of a change in the type of the object, a condition of the object, and a spatial relationship between the object and the plasma generating devices 104.

[0128] The hub device is able to adjust the operation of one or more of the plasma generating devices 104 based on a detected change in a property of the object such as a change in the type of the object or a change in the condition of the object. A change in the type of the object may mean that a property of the plasma such as the type and concentration of reactive chemical species present in the plasma needs to be adjusted. A change in the type of the object may mean that higher or lower energy plasma is required. A change in the condition of the object may indicate that the debris is present on the object, the object is contaminated, or the object has degraded. A change in the condition of the object may mean that higher or lower energy plasma is required.

[0129] A change in a property of the object may comprise a change in the spatial relationship between the object and the plasma generating devices 104. This may include a change in the distance between the object and the plasma generating device 104, and / or a change in the speed of the object (such as a conveyor) relative to the plasma generating device 104. The controller 126 may be configured to cause the one or more plasma generating devices 104 to adjust one or more properties of their plasma generation in response to determining that the object is less than a predetermined distance from the plasma generating devices 104. The controller 126 may be configured to adjust the distance between the plasma generating device 104 and the object such as by controlling an actuator to move the plasma generating device 104.

[0130] In some examples, the contextual data comprises an indication of the intended application of the plasma generation such as whether the plasma generation is used for surface treatment, liquid treatment, or decontamination. The hub device 102 can control the plasma generating devices 104 based on the determined application.

[0131] While the contextual data typically comprises a compressed representation of measurement data from the plasma generating devices 104, the hub device 102 may also receive raw, unprocessed, measurement data from one or more of the plasma generating devices 104. For example, the hub device 102 may request raw data from a particular plasma generating device 104 to verify that the plasma generating device 104 is correctly aggregating data. The hub device 102 may be able to diagnose issues from raw data that would not be immediately apparat through aggregate information alone.

[0132] The hub device 102 may comprise or may be in communication with a user interface to provide updates, metrics, and alerts to human operators. The hub device 102 may also send notifications via wireless communication protocols to a remote device to enable the plasma.

[0133] The plasma generating devices 104 are subject to overall control from the hub device 102 but also include local feedback mechanisms to provide real-time adjustments for the plasma generation.

[0134] To provide the local feedback, the controller 122 is connected to the sensors 120 and is arranged to receive measurement data from the sensors 120. The controller 122 processes the measurement data to determine adjustments to be made to the operation of the plasma generating device 104. This may involve adjusting one or more properties of the drive signal supplied to the primary coil 110 of the transformer 108. The adjustments may modify one or more of the frequency, amplitude, and duty cycle of the drive signal. In this way, the controller 122 is able to control the generation of plasma based on measurement data received from the sensors 120. For example, the output voltage of the transformer 110 is dependent on the frequency of the drive signal. Increasing the frequency increases the output voltage and vice versa. The controller 122 adjusting the frequency of the drive signal may therefore adjust the output voltage of the transformer 110 and thus the power of the generated plasma.

[0135] In some examples, the plasma generating device 104 receives input DC power via the interface 106. The power converter 124 acts as an DC to AC converter so as to provide an AC drive signal to the primary coil 110. The controller 120 controls the switching frequency of the power converter 124 to thereby control the frequency and duty cycle of the drive signal. The power converter 124 may be, for example, a full-bridge or half-bridge power converter.

[0136] The plurality of plasma generating devices 104 are able to operate independently to generate plasma. Each plasma generating device 104 has its own transformer 108 (or other form of step-up voltage generator) and controller 122 and thus can, for example, generate plasma at different times or power levels compared to other ones of the plasma generating devices 104. Moreover, the plasma generating devices 104 include sensors 120 that provide real-time feedback on the operational state of the plasma generating device 104. This feedback may characterise the properties of the plasma being generated or the health of components of the plasma generating device 104. The controller 122 uses the measurement data to adjust, in real time, the generation of the plasma to thereby optimise the performance of the plasma generating device 104.

[0137] In addition to controlling the plasma generation based on local feedback, the plasma generating device 104 is able to control the plasma generation based on a control signal received from the hub device 102. In some examples, the controller 122 of the plasma generating device use the measurement data and the control signal to adjust one or more properties of a drive signal supplied to the primary coil of the transformer.

[0138] For example, the control signal received from the hub device 102 may set initial parameters (such as frequency and drive signal) for the drive signal. The controller 122 may then adjust the initial parameters based on the measurement data received from the sensor 120. As the hub device 102 receives contextual data from the plasma generating devices 104 as described above, the hub device 102 may generate an updated control signal due to changes in the operating conditions of the plasma generating system 100, and may send an updated control signal to the plasma generating device 104 which can be used to set updated parameters for the drive signal. The controller 122 may then adjust the updated parameters based on the measurement data received from the sensor 120.

[0139] For example, the control signal may specify an initial frequency of the drive signal. The controller 122 may use an initial frequency set by the hub device 102 but may adjust the frequency based on real-time feedback. The real-time feedback may indicate that the frequency is insufficient to generate the desired plasma and may increase the frequency accordingly. The real-time feedback may indicate that the output voltage of the transformer 110 is too high and causing excessive heat to be generated in the transformer 110 or another component such as the dielectric 116. The controller 122 may then decrease the frequency accordingly.

[0140] In some situations, the control signal received from the hub device 102 overrides the local feedback mechanism such that the controller 122 only sets the drive signal based on the control signal. Typically, this hub device 102 led control of the drive signal is only temporary such as when a new plasma generating device 104 is added to the system. Once the new plasma generating device 104 is stabilised, local control based on measurement data received from the sensors 120 resumes.

[0141] The plasma generating devices 104 preferably comprise a plurality of sensors 120 such that the controller 122 adjusts the drive signal based on feedback received from multiple sensors measuring different properties of the plasma generating device 104.

[0142] The sensors 120 are arranged to measure one or more properties of the plasma generating device 104 such as one or more of a characteristic of a component of the plasma generating device 104, a spatial relationship between the plasma generating device 104 and an external object, and a characteristic of plasma generated by the plasma generating device 104.

[0143] The characteristics of a component of the plasma generating device 104 may comprise an electrical characteristic of a component of the plasma generating device 104, a structural characteristic of a component of the plasma generating device 104, and a temperature characteristic of a component of the plasma generating device 104. The sensors 120 may comprise an electrical sensor arranged to measure one or more properties of the output of the step-up voltage generator (e.g., the output of the secondary coil 112 of transformer 108). The measurement data may therefore comprise electrical measurements. The controller 122 receives the electrical measurements from the electrical sensor and adjusts the drive signal for the step-up voltage generator (e.g., supplied to primary coil 110 of the transformer 108) based on the electrical measurements. This can include the controller 112 comparing the received electrical measurements to desired values, and adjusting the drive signal based on the comparison.

[0144] The electrical sensor may measure one or more of the output voltage, output frequency, or output current of the step-up voltage generator (e.g., by measuring the output of the secondary coil 112).

[0145] As each plasma generating device 104 incorporates its own step-up voltage generator (e.g., transformer 108) characteristics may vary across the plasma generating devices 104. Variations in load or step-up voltage generator behaviour can introduce harmonics or distortions in the output waveform of the step- up voltage generator. Furthermore, the step-up voltage generators may degrade at different rates or be affected differently by temperature changes (such as heating) and component degradation.

[0146] If a global, fixed, drive signal was set for all step-up voltage generators then the plasma generating devices 104 would not be able to compensate for these variations leading to inconsistencies in the plasma generation across the plasma generating devices 104. This may also lead to some of the step- up voltage generators degrading at a faster rate than others. By measuring the output waveform in realtime, the controller 104 is able to identify these local changes and make adjustments to maintain optimal performance. In this way, each plasma generating device 104 can fine tune its drive signal based on real-time measurements.

[0147] The electrical sensor may comprise a voltage ladder connected to the electrode 114. The output from the voltage ladder is fed to a potential divider, followed by a buffer operational amplifier, and then to the controller 122. The electrode 114 and voltage ladder may be encapsulated to prevent electrical arcing and to protect the components from the surrounding environment. The input to the controller 122 may be isolated to enhance safety.

[0148] The sensors 120 may comprise a temperature sensor arranged to measure the temperature of one or more components of the plasma generating device 104. The measurement data may therefore comprise temperature data. The components may include a heat sink, MOSFETs, the transformer 108, the controller 122, and the electrode 114. Other components, and combination of components may be measured. For example, a thermocouple may be provided on each electrode 114 to measure the temperature thereof. The temperature sensor may comprise a plurality of temperature sensors each provided to monitor the temperature of one or a group of the components.

[0149] The temperature sensor may be provided by a (single) thermal camera. The thermal camera is mounted so that it has a field of view of a plurality of components of the plasma generating device. This arrangement allows the thermal camera to capture temperature data from key components in a single snapshot, eliminating the need for multiple sensor types and reducing the complexity and overall cost of the system.

[0150] The controller 122 processes the thermal data to monitor changes over time, and adjust the drive signal accordingly such as to reduce the temperature of a component if it has exceeded or is approaching a predefined temperature threshold. The controller 122 may also send alerts to the hub device 102 if the temperature of a component exceeds predefined thresholds, which could signal fatigue.

[0151] The sensor 120 may comprise a piezoelectric sensor arranged to measure changes in the structural properties of the dielectric 116. The controller 122 receives measurement data from the piezoelectric sensor and uses this measurement data to adjust the operation of the plasma generating device 104, such as by adjusting one or more properties of the drive signal supplied to the step-up voltage generator.

[0152] The structural properties of the dielectric 116 may change due to, for example, temperature increase, damage, or the presence of external objects on the surface of the dielectric 116. The piezoelectric sensor is able to detect these structural changes and feedback to the controller 122 to adjust the performance of the plasma generating device 104 accordingly.

[0153] For example, debris on the surface of the dielectric 116 could cause an electrical arc to form and generate a localised temperature hotspot. The piezoelectric sensor is able to detect this structural change in the dielectric. The controller 122 processes the measurement data received from the piezoelectric sensor and is able to determine the cause and location of the hotspot. The controller 122 is then able to adjust the drive signal accordingly. The controller 122 may adjust the drive signal to increase the plasma power to burn off the debris, or it could lower the plasma power while continuing to monitor the temperature closely. Data may be fed back to the hub device 102 so that the hub device 102 can control neighbouring plasma generating devices 104 to compensate for the change in plasma power.

[0154] The piezoelectric sensor can be used to monitor the dielectric 116 for signs of fatigue, providing early warnings of potential failure. If the controller 122 detects significant wear or degradation, it can relay a message back to the hub device 102 to send a maintenance request to replace the plasma generating device 104.

[0155] The piezoelectric sensor may comprise a piezoelectric wafer active sensor (PWAS). The PWAS comprises actuators and receivers. The actuators transmit guided wave pulses that are received by the receivers. As the waves interact with features such as the dielectric and any anomalies present, the properties of the waves change and these changes are detectable by the receivers. The controller 122 may implement machine-learning techniques to processes the received data from the piezoelectric sensor and characterise the type and location of the anomaly detected. An example machine-learning technique is the use of convolutional neural networks (CNN). The CNN can be trained to perform both regression tasks, such as predictive temperature, and classification tasks, such as identifying the location of hotspots within / across the dielectric 116.

[0156] The machine-learning model may be trained using temperature data for the dielectric obtained from a temperature sensors such as thermal camera described above. The captured temperature data may be used as a reference for the model training.

[0157] The spatial relationship between the plasma generating device 104 and an external object may be measured by a proximity sensor. The proximity sensor is arranged to measure the proximity of objects to the plasma generating device 104 and in particular to the dielectric 116 of the plasma generating device 104. The proximity sensor may comprise a time-of-flight sensor.

[0158] The controller 122 receives measurement data from the proximity sensor and processes the data to determine whether there is an object in the vicinity that could obstruct the operation of the plasma generating device 104 and / or cause damage to a component of the plasma generating device 104 such as the dielectric 116. The controller 122 adjusts one or more properties of the drive signal in response to the measurement data such as to reduce the power of plasma generation if an obstruction is identified.

[0159] The characteristic of plasma generated by the plasma generating device 104 may comprise a characteristic of the reactive chemical species present in the plasma generating device 104.

[0160] The sensor may comprise a detector arranged to detect reactive chemical specifies in the generated plasma. The detector may comprise a spectrometer, such as a UV spectrometer, an IR spectrometer, an FTIR spectrometer, an optical emission spectrometer, a mass spectrometer, an ion mobility spectrometer, an optical absorption spectrometer, a cavity ring down spectrometer, or a laser induced fluorescence spectrometer. The detector may be arranged to detect the type of reactive chemical species in the generated plasma, such as whether the reactive chemical species comprise reactive nitrogen chemical species or reactive oxygen chemical species. The detector detects reactive nitrogen chemical species by measuring for nitrogen dioxide in the generated plasma. The detector detects reactive oxygen chemical species by measuring for ozone in the generated plasma.

[0161] The detector may be arranged to detect the concentration of one or more types of reactive chemical species. The controller 122 compares the detected type and / or concentration to expected values for the plasma generation application. The controller 122 adjusts the operation of the plasma generating device 104 accordingly so as to promote generation of the desired type and / or concentration of reactive chemical species. The controller 122 may also adjust the operation of the plasma generating device 104 so as to suppress generation of an undesired type and / or concentration of reactive chemical species. The controller 122 may, in particular, adjust one or more properties of the drive signal in response to a concentration of a particular reactive chemical species exceeding a predetermined threshold. For example, if plasma comprising reactive oxygen species as the primary chemical species is desired, the controller 122 may determine if a concentration of another reactive chemical species such as reactive nitrogen increases above a predetermined threshold. The predetermined threshold may be zero, <1 %, <5%, <10% for example. Accordingly, the controller 122 can adjust one or more properties of the drive signal to reduce the generation of reactive nitrogen species.

[0162] Not all of the plasma generating devices 104 may comprise a detector. Only one or a subset of the plasma generating devices 104 may comprise a detector. The plasma generating device(s) 104 comprising a detector may serve as the benchmark, providing detailed plasma diagnostics and setting the standard against which the other feedback methods can be compared and calibrated.

[0163] Figure 2 shows an example method performed by a hub device 102 of the plasma generating system 100. The method is performed by the controller 126.

[0164] Step S201 comprises obtaining contextual data from a plurality of plasma generating devices 104 indicative of the operational conditions of the plasma generating system 100 comprising the plurality of plasma generating devices 104.

[0165] Step S202 comprises processing the contextual data to determine whether there is a change in the operational conditions of the plasma generating system 100.

[0166] Step S203 comprises, in response to determining there is a change in the operational conditions of the plasma generating system 100, causing one or more of the plasma generating devices 104 to adjust one or more properties of their plasma generation.

[0167] Figure 3 shows an example method performed by a plasma generating device 104 of the system 100. The method is performed by the controller 122.

[0168] Step S301 comprises receiving a control signal from the hub device 102.

[0169] Step S302 comprises receiving measurement data from a sensor 120 of the plasma generating device 104.

[0170] Step S302 comprises using the control signal and the measurement data to adjust the operation of the plasma generating device 104. In this example method, the control signal and measurement data are used to adjust one or more properties of a drive signal.

[0171] Step S304 comprises supplying the drive signal to the primary coil 110 of the transformer 108 of the plasma generating device 104 so as to control the output of the secondary coil 112 of the transformer 108 coupled to the electrode 114 for generating plasma. It will be appreciated that other forms of step- up voltage generators may be used instead of or in addition to a transformer. In general, step S304 comprises supplying the drive signal to the step-up voltage generator so as to control the output of the step-up voltage generator.

[0172] Referring to Figures 4 to 7, there is shown an example plasma generating device 104 according to aspects of the present disclosure. The plasma generating device 104 comprises a housing 402 having a top 404 (Figure 4) and a base 406 (Figure 5). The base 406 comprises the dielectric 116. The dielectric 116 covers the outer facing surface of the electrode 114. The electrode 114 is arranged within the housing 402 such that it is in contact with the dielectric 116. The housing 402 is made from an electrically insulating material.

[0173] The inner facing surface of the electrode 114 (the surface that faces into the housing) is covered by an encapsulant 408 (Figure 7). A ground electrode is not included in the plasma generating device 104 in this example and instead an external ground electrode is used. In other examples, ground electrode(s) could be provided on an external surface of the base 406 such that the dielectric 116 is arranged between and separates the ground electrode(s) from the electrode 114.

[0174] The step-up voltage generator in this example is a transformer 108. The transformer 108 and controller 122 are arranged within the housing 202.

[0175] The plasma generating device 104 comprises a plurality of sensors 120.

[0176] The sensors 120 comprise an electrical sensor (not shown) that is connected to the electrode 114 for measuring properties of the output waveform generated by the secondary coil 110.

[0177] The sensors 120 comprise a temperature sensor in the form of a thermal camera 410 (Figure 7). The thermal camera 410 is mounted to the inner surface of the top 404 of the housing 402 such that the components contained within the housing 402 can be captured within the field of view of the thermal camera 410. In particular, the transformer 108, controller 122, heat sink 412 and electrode 114 are within the field of view of the thermal camera 410. While the electrode 114 is covered by the encapsulant 408, the encapsulant 408 comprises an optically clear window 414 to allows for the thermal camera 410 to measure the temperature of the electrode 210.

[0178] The sensors 120 comprise a detector 416 (Figure 7) arranged to determine the presence of reactive chemical species in the generated plasma. The detector 416 in this example is a spectrometer and in particular a UV spectrometer. The detector 416 comprises an optical cable 418 (Figure 7) that extends into the encapsulant 408 at an angle to provide a view of the emission of plasma through the dielectric 116. A multi-furcated optical cable could be used to monitor plasma generation at two or more points.

[0179] The spectrometer may be used in conjunction with a light source to perform optical absorbance measurements to determine absolute concentrations of reactive chemical species in the generated plasma.

[0180] The sensors 120 comprise a piezoelectric sensor 420 (Figure 6). The piezoelectric sensor 420 is a piezoelectric wafer active sensor (PWAS). The PWAS comprises actuators and detectors. The PWAS actuator and detectors are arranged around the perimeter of the dielectric 116 and are spaced away from the electrode 114 to avoid arcing.

[0181] The sensors 120 comprise a proximity sensor 422 (Figure 5) integrated into the base 406 of the housing 402 so as to measure the proximity of objects in relation to the base 406 and dielectric 116. The plasma generating device 104 is not required to comprise all of the sensors 120 in this example. The plasma generating device 104 could comprise different combinations of sensors 120.

[0182] The plasma generating device 104 further comprises an NFC tag 424. The NFC tag 424 comprises an antenna and a data store such as an EEPROM. The NFC tag 424 is mounted in a slot formed in the base 406 of the plasma generating device 104. The outside surface of the base 406 may comprise a marker to indicate the location of the NFC tag 424 / tag antenna.

[0183] An NFC writer, when brought into proximity with the NFC tag 424, can write configuration information to the data store. This provides an easy mechanism to write configuration information to the plasma generating device 104 without requiring communication with the hub device 102 over the interface 106. The configuration information may be written when the plasma generating device 104 is added to the system and may indicate, for example, the communication address that will be used by the hub device 102 to communicate with the plasma generating device 104 in future. In this way, a new plasma generating device 104 can be easily configured to communicate with the hub device 102 without requiring manual intervention by a technician such as by adjusting DIP switches or address registers which are time consuming and would require disassembly of the plasma generating device 104.

[0184] When the plasma generating device 104 is powered, the configuration information stored in the data store is readable by the controller 122. The controller 122 may also write data to the data store such as operational information for the plasma generating device 104.

[0185] An NFC reader can also read configuration information / operational information from the data store when the plasma generating device 104 is not powered. This can be used for troubleshooting and maintenance.

[0186] The NFC writer / NFC reader may be part of the hub device 102 or may be a separate device such as a handheld scanner.

[0187] Example data stored in the data store include a unique identifier for the plasma generating device 104, current firmware / software versions, frequency settings, duty cycle, voltage / current measurement with timestamps, current / total runtime, last maintenance date, electrode identifier, temperature data, communication address, failure events, and reset trigger.

[0188] Figures 8 to 11 show an example implementation of the plasma generating system 100. The plasma generating system 100 is used, in this example, to decontaminate a conveyor 802 of a conveyor system 800 such as may be used in the food processing industry.

[0189] The plurality of plasma generating devices 104 (nine in this example) are as described above in relation to Figures 4 to 7. The plasma generating devices 104 are mounted on a support structure 804 and positioned such that the bases of the plasma generating devices 104 (where the electrode 114 and dielectric 116 are located) are in close proximity with the conveyor 802. The plasma generating devices 104 may be positioned such that they are less than 10 mm from the conveyor 802. The maximum / minimum separation depends on factors such as the type of plasma generation used. For example, for dielectric barrier discharge a separation of up to 50 mm may be used whereas surface barrier discharge could use a greater separation. A minimum separation could be 0.5 mm or 1 mm. Example separation ranges include between 0.5 mm and 50 mm, between 0.5 mm and 20 mm, between 0.5 mm and 10 mm, between 0.5 mm and 5 mm, between 1 mm and 50 mm, between 1 mm and 20 mm, between 1 mm and 10 mm, and between 1 mm and 5 mm.

[0190] In this example, the plasma generating devices 104 are mounted above the conveyor 802, but they may also be mounted underneath the conveyor 802. The dielectric 116 therefore faces the conveyor 802 and there is a small gap between the dielectric 116 and the conveyor 802. The support structure 804 may be free standing or may be attached to the conveyor system 800.

[0191] The conveyor 802 is mounted on a frame 806. The frame 806 or a component of the frame 806 functions as a ground electrode for the plurality of plasma generating devices 104. Operation of the plasma generating devices 104 as described above, causes plasma to be generated on the external surface of the dielectric 116 to thereby decontaminate the conveyor 802. As the conveyor 802 moves, different regions of the conveyor 802 are brought into proximity with the plasma generating devices 104 such that the full length of the conveyor 802 can be decontaminated using the plasma generating devices 104 which are generally located in a fixed position relative to the length of the conveyor 802.

[0192] The plurality of plasma generating devices 104 are arranged on the support structure 804 such that they collectively cover the whole width of the conveyor 802. In this way, the whole width of the conveyor 802 can be decontaminated in one operation without having to move any of the plasma generating devices 104. Moreover, the modular approach of the present disclosure means that the system 100 can be easily adapted to different widths of conveyors 802 by using different numbers and combinations of the plasma generating devices 104. In this way, bespoke plasma generating devices 104 are not required for different conveyors 802 simplifying installation and maintenance. Moreover, having multiple plasma generating devices 104 rather than a single plasma generating device 104 simplifies manufacture of the system 100 and reduces cost. Forming a single dielectric 116 that spans the width of the conveyor 802 would be expensive and complicated to manufacture. Moreover, a bespoke plasma generating device 104 would be required for each different width of conveyor 802.

[0193] The plurality of plasma generating devices 104 are removably attached to the support structure 804. This enables plasma generating devices 104 to be easily removed and replaced. This reduces downtime as the entire system 100 does not need to be shut down for extended periods when an error occurs in one of the plasma generating devices 104.

[0194] The support structure 804 in this example is a frame. The plasma generating devices 104 are located in two rows. The rows are staggered to help ensure that the full width of the conveyor 802 is covered. The frame comprises an aperture 808 which, in this example, is arranged between the two rows. The aperture 808 is connectable to an extraction unit (not shown) to bring the extraction unit into fluid communication with the space between the dielectrics 116 and the conveyor. This enables the extraction unit to remove plasma generated species.

[0195] The hub device 102 is mounted in a cabinet 810. A control unit 812 for controlling the conveyor 802 is also provided in a cabinet 814 below the hub device 102. The control unit 810 is connected to the hub T1

[0196] P10004WO device 102 such that the hub device 102 may control the speed of the conveyor 802 and may receive data identifying the speed of the conveyor 802.

[0197] In an example operation, the plurality of plasma generating devices 104 operate to generate plasma for decontaminating the conveyor 802 as the conveyor moves. The hub device 102 may adjust one or more properties of the plasma generation by the plasma generating devices 104 based on speed of the conveyor 802.

[0198] Debris (such as food particles) on the conveyor 802 could potentially land on the dielectric 116 of a plasma generating device 104 potentially causing an arc or creating a hotspot. This may be detected by the sensors 120 of the relevant plasma generating device 104 such as the piezoelectric sensor 420. The controller 122 is able to adjust the drive signal applied to primary coil of the transformer 108 in response to this detection to mitigate for the presence of the debris.

[0199] In addition, contextual data can be sent from the affected plasma generating device 104 to the hub device 102. The hub device 102 can notify a human operator so that they can clean the dielectric 116 at an appropriate time. The hub device 102 can adjust the operation of other plasma generating devices 104 in the vicinity of the affected plasma generating device 104 to compensate for the change in operation of the affected plasma generating device 104. For example, the other plasma generating devices 104 could be controlled to operate at a higher power if the power of the affected plasma generating device 104 is reduced.

[0200] The hub device 102 may also control other aspects of the system 100 such as by reducing the speed of the conveyor 802 and / or increasing the distance between the plasma generating devices 104 and the conveyor 802.

[0201] The plasma generating devices 104 or hub device 102 may detect the presence of obstructions that could impact the plasma generating device 104 and potentially damage the dielectric 116. The obstructions could be debris on the conveyor 802 or irregularities of the conveyor 802 such as localised bulges due to an aging or improperly fitted conveyor 802, or temporary repairs or modifications to the conveyor 802.

[0202] These obstructions may be detected by the proximity sensors 422 of the plasma generating devices 104 which function to monitor the proximity of objects. Individual plasma generating devices 104 can, for example, temporarily deactivate their plasma output when it is determined that the obstruction is below or approaching the dielectric 116 to mitigate the risk of damage.

[0203] The present disclosure is not limited to plasma treatment of conveyor systems such as used in the food processing industry. The plasma generating systems disclosed may be used in other applications where plasma generation is desired. For example, the plasma generating systems may be used to generate plasma activated liquid (e.g., water). Other applications include the treatment, decontamination, and functionalisation of materials such as packaging materials.

[0204] Various combinations of optional features have been described herein, and it will be appreciated that described features may be combined in any suitable combination. In particular, the features of any one example embodiment may be combined with features of any other embodiment, as appropriate, except where such combinations are mutually exclusive. Throughout this specification, the term “comprising” or “comprises” means including the component(s) specified but not to the exclusion of the presence of others. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive.

[0205] Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent, or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0206] The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

29P10004WOCLAIMS1 . A plasma generating system comprising: a hub device comprising an interface for data communication with the plasma generating device; and a plurality of plasma generating devices each connectable to the hub device, each plasma generating device comprising: an interface for data communication with the hub device; a step-up voltage generator comprising an input connectable to a power source and an output connected to an electrode for generating plasma; a sensor arranged to measure one or more properties of the plasma generating device; and a controller connected to the interface, the step-up voltage generator and the sensor, the controller is configured to receive a control signal from the hub device via the interface, receive measurement data from the sensor, and use the measurement data and the control signal to adjust the operation of the plasma generating device.

2. A plasma generating system as claimed in claim 1 , wherein the controller being configured to adjust the operation of the plasma generating device comprises the controller being configured to adjust one or more properties of a drive signal supplied to the step-up voltage generator.

3. A plasma generating system as claimed in claim 2, wherein the one or more properties of the drive signal comprising one or more of the amplitude, frequency, and duty cycle of the drive signal.

4. A plasma generating system as claimed in any preceding claim, wherein the controller is configured to adjust the operation of the plasma generating device in response to determining that the measurement data indicates that a property of the plasma generating device is not within a predetermined range.

5. A plasma generating system as claimed in any preceding claim, wherein the one or more properties of the plasma generating device comprise one or more of a characteristic of a component of the plasma generating device, a spatial relationship between the plasma generating device and an external object, and a characteristic of plasma generated by the plasma generating device.

6. A plasma generating system as claimed in claim 5, wherein the characteristic of a component of the plasma generating device comprises a structural characteristic of a component of the plasma generating device.30P10004WO7. A plasma generating system, as claimed in claim 6, wherein the structural characteristic of a component of the plasma generating device comprises a structural characteristic of a dielectric of the plasma generating device.

8. A plasma generating system as claimed in claim 6 or 7, wherein the sensor comprises a piezoelectric sensor.

9. A plasma generating system as claimed in claim 8, wherein the piezoelectric sensor comprises a piezoelectric wafer active sensor.

10. A plasma generating system as claimed in any of claims 5 to 9, wherein the characteristic of the spatial relationship between the plasma generating device and an external object comprises a characteristic of the distance between a dielectric of the plasma generating device and the external object.11 . A plasma generating system as claimed in claim 10, wherein the sensor comprises a proximity sensor, and optionally wherein the proximity sensor comprises a time-of-flight sensor.

12. A plasma generating system as claimed in any of claims 5 to 11 , wherein the characteristic of a component of the plasma generating device comprises an electrical characteristic of a component of the plasma generating device.

13. A plasma generating system as claimed in any of claims 5 to 12, wherein the characteristic of a component of the plasma generating device comprises a temperature characteristic of a component of the plasma generating device, wherein the sensor comprises a temperature sensor arranged to measure the temperature of one or more components of the plasma generating device, and optionally wherein the temperature sensor comprises a thermal camera positioned such that its field of view captures a plurality of components of the plasma generating device.

14. A plasma generating device as claimed in any of claims 5 to 13, wherein the characteristic of plasma generating by the plasma generating device comprises a characteristic of the reactive chemical species present in the plasma generated by the plasma generating device.

15. A plasma generating system as claimed in any preceding claim, further comprising a support structure on which the plurality of plasma generating devices are retained.

16. A plasma generating system as claimed in claim 15, wherein the plurality of plasma generating devices are releasably attached to the support structure.

17. A plasma generating system as claimed in claim 15 or 16, wherein the support structure is arranged to be positioned in proximity to a conveyor of a conveyor system such that the plurality of plasma generating devices can generate plasma for decontaminating the conveyor.

18. A plasma generating system as claimed in any preceding claim, wherein the plasma generating device comprises an NFC tag comprising an antenna and a data store, wherein the data store is arranged to store configuration information received from an NFC writer brought into proximity with the antenna, and wherein the data store is coupled to the controller such that the controller is able to read the configuration information from the data store.

19. A plasma generating system as claimed in any preceding claim, wherein the controller is arranged to send, via the interface, data to the hub device, wherein the data comprises contextual data indicative of the operational conditions of the plasma generating system.

20. A plasma generating system as claimed in claim 19, wherein the contextual data comprises a compressed representation of the measurement data received from the sensor.

21. A plasma generating system as claimed in any preceding claim, wherein the hub device comprises: a controller configured to: obtain contextual data from the plasma generating device indicative of the operational conditions of the system; process the contextual data to determine whether there is a change in the operational conditions of the plasma generating system; and in response to determining there is a change in the operational conditions of the plasma generating system, cause the plasma generating device to adjust one or more properties of its plasma generation.

22. A method for generating plasma by a plasma generating system, the method comprising: receiving, by a plasma generating device of the plasma generating system, a control signal from a hub device; receiving, by the plasma generating device, measurement data from a sensor of the plasma generating device; using, by the plasma generating device, the control signal and the measurement data to adjust the operation of the plasma generating device.

23. A method as claimed in claim 22, wherein using the control signal and the measurement data comprises adjusting one or more properties of a drive signal based on the control signal andthe measurement data, and supplying the drive signal to step-up voltage generator of the plasma generating device so as to control the output of the step-up voltage generator coupled to an electrode for generating plasma.

24. A plasma generating system comprising: a hub device connectable to a plurality of plasma generating devices, the hub device comprising: an interface for data communication with the plurality of plasma generating devices; and a controller configured to: obtain contextual data from the plurality of plasma generating devices indicative of the operational conditions of the plasma generating system; process the contextual data to determine whether there is a change in the operational conditions of the plasma generating system; and in response to determining there is a change in the operational conditions of the plasma generating system, cause one or more of the plasma generating devices to adjust one or more properties of their plasma generation.

25. A plasma generating system as claimed in claim 24, wherein the change in the operational conditions comprises a change in the characteristics of the plasma generating devices and / or a change in the environment of the plasma generating system.

26. A plasma generating system as claimed in claim 25, wherein the change in the characteristics of the plasma generating devices comprises a change in the performance of one or more of the plasma generating devices.

27. A plasma generating system as claimed in claim 26, wherein the change in the performance of the one or more plasma generating devices comprises the performance of the one or more plasma generating devices moving outside of a predetermined performance range.

28. A plasma generating system as claimed in claim 26 or 27, wherein the change in the performance of the one or more plasma generating devices comprises a fault being present in the one or more plasma generating devices.

29. A plasma generating system as claimed in claim 28, wherein the controller is configured to cause the one or more plasma generating devices associated with the fault to adjust one or more properties of their plasma generation.33P10004WO30. A plasma generating system as claimed in claim 29, wherein the controller is configured to cause one or more other plasma generating devices to adjust one or more properties of their plasma generation.

31. A plasma generating system as claimed in any of claims 25 to 30, wherein the change in the characteristics of the plasma generating devices is due to a plasma generating device being added to the system.

32. A plasma generating system as claimed in claim 31 , wherein the controller is configured to cause the plasma generating device added to the system to adjust one or more properties of its plasma generation.

33. A plasma generating system as claimed in any of claims 25 to 32, wherein the change in the environment comprises a change in the ambient environment of the plasma generating system.

34. A plasma generating system as claimed in any of claims 25 to 33, wherein the change in the environment comprises a change in a property of an object external to the plasma generating devices, optionally wherein the object comprises an object to be treated by the plasma generating devices.

35. A plasma generating system as claimed in claim 34 , wherein the change in the property of the object comprises one or more of a change in the type of the object, a condition of the object, and a spatial relationship between the object and the plasma generating devices.

36. A plasma generating system as claimed in claim 35, wherein the change in the spatial relationship comprises a change in the distance between the object and the plasma generating devices, and wherein the controller is configured to cause the one or more plasma generating devices to adjust one or more properties of their plasma generation in response to determining that the object is less than a predetermined distance from the plasma generating devices.

37. A plasma generating system as claimed in any of claims 34 to 36, wherein the object comprises a conveyor of a conveyor system.

38. A plasma generating system as claimed in any of claims 24 to 37, wherein the controller being configured to cause the one or more plasma generating devices to adjust one or more properties of their plasma generation comprises the controller being configured to cause the one or more plasma generating devices to adjust one or more of their operating power for plasma generation, their operating frequency for plasma generation, their operating duty cycle for plasma generation, their distance relative to an external object, the rate at which plasma34P10004WO generated species are extracted, and the temperature of one or more electrodes of the plasma generating device.

39. A plasma generating system as claimed in any of claims 24 to 38, wherein the controller is further configured to select, based on the change in the operational conditions, the one or more plasma generating devices to be caused to adjust the one or more properties of their plasma generation.

40. A plasma generating system as claimed in any of claims 24 to 39, wherein contextual data comprises a compressed representation of measurement data captured by the plasma generating devices.41 . A plasma generating system as claimed in any of claims 24 to 40, further comprising the plurality of plasma generating devices.

42. A plasma generating system as claimed in claim 41 , wherein the plurality of plasma generating devices each comprise: an interface for data communication with the hub device; a step-up voltage generator comprising an input connectable to a power source, and an output connected to an electrode for generating plasma; and a controller connected to the interface and the step-up voltage generator, the controller configured to supply a drive signal to the primary coil of the step-up voltage generator.

43. A plasma generating system as claimed in claim 42, wherein the controller is configured to receive a control signal from the hub device via the interface, and use the control signal to adjust one or more properties of the drive signal supplied to the step-up voltage generator.

44. A plasma generating system as claimed in claim 43, wherein each plasma generating device further comprises a sensor arranged to measure one or more properties of the plasma generating device, and wherein the controller is configured to receive the measurement data from the sensor, and use the measurement data and the control signal to adjust one or more properties of the drive signal.

45. A plasma generating system as claimed in claim 44, the one or more properties of the plasma generating device comprise one or more of an electrical property of the plasma generating device, a thermal property of the plasma generating device, a chemical property of the plasma generated by the plasma generating device, a structural property of the plasma generating device, and a spatial relationship between the plasma generating device and an external object.

46. A method performed by a plasma generating system, the method comprising:obtaining, by a hub device of the plasma generating system, contextual data from a plurality of plasma generating devices, the contextual data indicative of the operational conditions of the plasma generating system; processing, by the hub device, the contextual data to determine whether there is a change in the operational conditions of the plasma generating system; and in response to determining there is a change in the operational conditions of the plasma generating system, causing, by the hub device, one or more of the plasma generating devices to adjust one or more properties of their plasma generation.

47. A computer program having instructions recorded thereon which, when executed by one or more processors, cause the one or more processors to perform the method as claimed in claim 22 or 23 or claim 46.

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