A method and system for hybrid transmission of power and multi-stream data based on tether of underwater robot

Abstract

A kind of power and multi-flow data hybrid transmission method and system based on tethered rope of underwater robot, propose hybrid communication architecture: downlink utilizes switch ripple energy signal transmission technology (TPC), by fine-tuning the zero level time or phase shift angle of power converter bridge arm voltage, control instruction is embedded in voltage ripple, realize microsecond level deterministic low delay transmission;Uplink utilizes frequency shift keying energy signal transmission technology (FSK-TPC), by energy storage or power driven power converter, state data is returned, and integrated broadband high-speed power line communication module transmission high-definition video stream;While introducing hybrid duplex communication mode (uplink and downlink TPC time division duplex, TPC and PLC frequency division duplex), coordinate duplex timing and isolate high and low frequency signals, effectively suppress high-power switch noise interference.The present application significantly reduces the weight of tether, reduces hardware volume by more than 70%, suitable for tethered underwater robot, tethered unmanned aerial vehicle, deep sea exploration and mine operation and other scenes.

Description

Technical Field

[0001] This invention relates to the field of power electronics and information communication technology, and in particular to a method and system for hybrid transmission of power and multi-stream data based on an underwater robot tether. Background Technology

[0002] With the deepening exploration of extreme environments such as marine development, high-altitude operations, and underground mining, tethered unmanned platforms (such as tethered underwater robots (ROVs), tethered drones, and deep-earth drilling equipment) are playing an increasingly crucial role in marine resource development, disaster relief, and scientific observation. These platforms, connected to base stations via tethers, have achieved virtually unlimited endurance, but the tethers have also become a key bottleneck restricting system performance. Taking underwater robots as an example, in deep-sea operations, the water resistance experienced by the cable increases quadratically with its diameter. Traditional heavy multi-core cables generate enormous drag forces in complex ocean currents, not only weakening the robot's thrust bandwidth but also leading to decreased positioning accuracy, and potentially even equipment loss due to cable entanglement. Therefore, "lightweight cables" and "single-core" cables have become urgent industry demands for improving operating depth, current resistance, and load-bearing capacity.

[0003] However, achieving coaxial cable transmission of energy and information over a single-core cable, coaxial cable, or single power line presents extremely serious engineering challenges. First, there is the interference challenge posed by the strong electromagnetic interference (EMI). To meet the platform's power requirements of several kilowatts or even higher, high-frequency switching control currents flow through the cable. The switching ripple and electromagnetic noise frequency bands generated by power electronic converters (such as dual active bridge DAB converters) often overlap with traditional communication signals, forming an extremely high noise floor and causing a surge in the bit error rate of traditional communication solutions. Second, tethered operations involve three types of heterogeneous data streams with drastically different characteristics: downlink control command streams requiring microsecond-level extremely low latency to ensure the robustness of the motion system; uplink sensor status streams requiring high robustness; and video or sonar media streams requiring Mbps-level high bandwidth. Within the limited channel capacity of a single-core cable, effectively suppressing the severe interference caused by high-power transmission while simultaneously balancing the conflicting data requirements of low-latency control and high-bandwidth transmission has become a core technical challenge that urgently needs to be overcome in the field of tethered unmanned systems.

[0004] Currently, the main technical solutions for tethered underwater robots to achieve energy and information transmission are divided into multi-core cable physical isolation method, traditional high-speed broadband power line communication method, and switch ripple energy and information transmission method.

[0005] The first method is the multi-core cable physical isolation method, which is the most traditional engineering solution. This involves setting up independent power and signal cores inside the cable. Its significant disadvantages are that the cable has a large diameter and heavy weight, which will generate huge fluid resistance in deep-sea operations and occupy a large drum volume, severely limiting the robot's operating depth and mobility.

[0006] The second method is the traditional high-speed broadband power line communication (PLC) method. This technology injects high-frequency signals (such as the HomePlug AV scheme based on the IEEE 1901 standard, 2-68MHz) into the power line through a coupling transformer. Although this method solves the bandwidth problem of single-core transmission, its protocol stack is extremely complex, resulting in data packet processing delays typically in the millisecond (ms) range. This cannot meet the requirements of motor control commands such as ROV dynamic obstacle avoidance that require extremely high real-time performance. In addition, under the severe electromagnetic interference (EMI) generated by high-power switching operations, PLCs are prone to packet loss, limiting communication reliability.

[0007] The third method is based on Talkative Power Conversion (TPC) (see Talkative Power Conversion: Atutorial, published in the Proceedings of the IEEE in 2025). This method embeds data directly by controlling the switching frequency or duty cycle of the power converter. Although this method has extremely low transmission latency, its communication bandwidth is typically limited to the tens of kbps range due to the power switching frequency. This makes basic TPC solutions only capable of transmitting simple sensor monitoring data, completely unable to support large data volume services such as high-definition video streams or sonar images.

[0008] Traditional tethered underwater robots typically rely on bulky multi-core cables to transmit power, high-speed video, and real-time control commands separately, resulting in large system size, high cost, and complex wiring. While existing technologies attempt to achieve simultaneous power and signal transmission over a single-core cable, they often face challenges such as high real-time control latency, insufficient bandwidth for high-speed streaming media, or severe signal interference from power conversion ripple, making it difficult to simultaneously achieve reliable bidirectional communication between high-power transmission and heterogeneous multi-stream data.

[0009] While the aforementioned existing technologies can achieve energy or information transfer in specific scenarios, they still have the following significant drawbacks in the complex application environments of tethered underwater robots: Poor adaptability of multi-stream data transmission: Existing technologies typically employ a single modulation method, which cannot simultaneously handle heterogeneous data with drastically different characteristics. While multi-core cables can solve this problem, the resulting cable weight and fluid resistance severely limit operational capabilities. Traditional PLC technology suffers from excessive protocol overhead when processing small data packets and high-frequency control commands, leading to poor performance in "control flow"; while basic TPC technology, due to its baud rate limitation, is completely unable to handle "media streams." This contradiction between a single transmission mechanism and the complex data requirements of modern tethered platforms is the biggest drawback of existing technologies.

[0010] Communication delays and insufficient determinism: Traditional PLC solutions based on standards such as IEEE 1901 employ contention mechanisms or complex addressing protocols in their media access control layer, resulting in unpredictable latency (milliseconds) for data under network congestion or strong interference. For motor closed-loop control systems requiring microsecond-level response cycles, this uncertain delay can easily lead to control overshoot or even system crashes. Existing technologies struggle to provide deterministic real-time control channels in the context of high-power noise from single-core cables.

[0011] Balancing electromagnetic interference resistance and reliability is challenging: In applications where single-core cables carry several kilowatts of power, the high-energy harmonics generated by converter switching operations strongly suppress traditional communication signals. To maintain high-speed transmission, PLC technology must employ complex error correction algorithms, further increasing the processor's computational burden and processing time. While existing basic TPC solutions offer strong anti-interference capabilities, the lack of effective bidirectional multiplexing mechanisms (such as time-division duplexing and frequency decoupling) makes it easy for weak uplink and downlink signals to be overwhelmed by switching noise, hindering stable and reliable full-duplex communication.

[0012] The challenge of balancing system complexity and cost: Overcoming interference issues with PLCs often requires designing large, complex isolation filters and coupling transformers, which is unacceptable for underwater robot cabins with extremely limited space. Current technology lacks a lightweight solution that can deeply integrate the inherent characteristics of the power circuit and achieve reliable multi-stream data transmission without redundant hardware.

[0013] In summary, existing single-core cable transmission solutions exhibit a significant technological gap in achieving high bandwidth, low latency, and high reliability, failing to simultaneously meet the complex heterogeneous data transmission requirements of modern tethered platforms. Existing solutions often present a trade-off: either they can transmit large amounts of data but suffer from high latency (PLC), or they offer low latency but extremely limited bandwidth (TPC). Therefore, modern tethered underwater robots urgently require a solution that can simultaneously satisfy the conflicting demands of high-power transmission, ultra-low latency control (for precise manipulation), and ultra-high bandwidth video transmission (for visual feedback) over a single cable.

[0014] It should be noted that the information disclosed in the background section above is only for understanding the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0015] The main objective of this invention is to overcome the deficiencies in the aforementioned background technology and provide a method and system for hybrid transmission of power and multi-stream data based on an underwater robot tethering rope.

[0016] To achieve the above objectives, the present invention adopts the following technical solution: A method for hybrid power and multi-stream data transmission based on an underwater robot tether, wherein the tethered underwater robot is connected to a central control station via a single-core cable, the method comprising the following steps: The single-core cable connects the surface control center and the underwater robot, enabling DC power transmission and hybrid duplex communication of time-division and frequency-division. During downlink transmission, the parent control center uses the energy and signal transmission technology based on switch ripple to embed downlink control commands into the switch ripple by modulating the switching action parameters of the power switch in the power converter, and then transmits them to the underwater robot end via the single-core cable. During uplink transmission, the underwater robot injects the sensor status data modulated by frequency shift keying into the single-core cable in the form of switching ripple through the battery-side converter, and transmits it back to the mother control center. An integrated broadband power line communication module superimposes a high-definition video stream onto the DC bus of the single-core cable via a high-frequency carrier signal, and transmits it in parallel with the downlink switch ripple and the uplink switch ripple. The transmission timing of the downlink and uplink of the power line communication is coordinated by the time division duplex strategy, and the frequency decoupling technology is used to isolate the high-frequency power line communication signal and the intermediate frequency power conversion signal in the frequency domain, so as to realize the coexistence of multi-stream data and bidirectional reliable communication.

[0017] A hybrid power and multi-stream data transmission system based on an underwater robot tether rope includes: The mother control center includes dual active bridge converters and control units; A single-core cable connects the mother control center to the underwater robot. The underwater robot end includes a power electronic converter, a power line communication module, energy storage, and load. The mother control center is configured to: transmit DC power to the underwater robot via a single-core cable through the dual active bridge converter; and use the power and signal transmission technology based on switching ripple to embed downlink control commands into the voltage ripple for transmission by modulating the operating parameters of the switching transistors in the dual active bridge converter. The underwater robot end is configured to: inject sensor status data modulated by frequency shift keying into a single-core cable in the form of switching ripple via a battery or power drive converter; and transmit high-definition video streams superimposed on the single-core cable in the form of high-frequency carrier waves via the power line communication module. The system is also configured to coordinate downlink and uplink transmission timing through a time-division duplex strategy, and to isolate high-frequency power line communication signals from intermediate-frequency power conversion signals through frequency decoupling.

[0018] The beneficial effects of this invention compared to the prior art are as follows: This invention addresses the shortcomings of traditional multi-core cable solutions for tethered underwater robots, including heavy cables, poor maneuverability, high real-time control latency, limited video transmission bandwidth, and severe noise interference from high-power switching. It proposes a hybrid power and multi-stream data transmission method and system based on the underwater robot's tethering rope. While existing technologies, such as multi-core cable physical isolation, can separate energy and data, the large cable diameter and weight generate significant fluid resistance in deep-sea operations, severely limiting operating depth and maneuverability. Traditional broadband power line communication (PLC) solutions based on standards like IEEE 1901 can solve the bandwidth problem of single-core transmission, but their complex protocol stack and contention mechanisms in the media access control layer result in millisecond-level transmission delays with random uncertainty, failing to meet the microsecond-level real-time response required for underwater robot thruster vector control. Existing basic switch ripple energy-to-signal (TPC) technology, while offering low latency, is limited by the power switching frequency, with a communication bandwidth of only tens of kbps, completely unsuitable for high-definition video streams or sonar images and other high-data-volume services. It is evident that existing technologies face a dilemma where "high bandwidth" and "low latency" cannot be achieved simultaneously.

[0019] The core innovation of this invention lies in its departure from the traditional power line carrier superposition and instead, by deeply reusing the inherent switching actions of power electronic converters, a heterogeneous multi-current energy-information co-transmission architecture with complementary physical characteristics—the "tethered communication" hybrid modulation architecture. This architecture integrates three complementary modulation techniques via a single-core cable: the downlink utilizes energy-information co-transmission technology based on switching ripple, finely adjusting the zero-level time or phase shift angle of the bridge arm voltage of the power switches in the power converter (such as a dual active bridge converter) to directly embed high-priority control commands into the waveform distortion characteristics of the output voltage ripple. This significantly reduces the transmission delay of downlink control commands from milliseconds to microseconds (measured at 10μs±1μs), fundamentally eliminating the queuing and processing time overhead of traditional protocol stacks. This ensures high determinism and real-time performance of command transmission between the mother ship control unit and the underwater robot actuators, greatly improving the robot's control closed-loop frequency and obstacle avoidance stability in dynamic waters. Simultaneously, since this modulation does not change the average direction of the output voltage vector, it achieves "lossless" embedding of control commands.

[0020] In the uplink, this invention uses an energy storage or power drive converter on the underwater robot to inject sensor status data (such as depth and attitude) into a single-core cable via frequency shift keying (FSK) in the form of switching ripple. A broadband power line communication (PLC) module is integrated on this basis to transmit high-definition video streams superimposed on a DC bus via a high-frequency carrier (e.g., 2-68 MHz). Frequency decoupling technology completely isolates the PLC high-frequency signal from the TPC intermediate frequency power conversion signal in the frequency domain—the receiving end first filters out the high-frequency media signal using a hardware low-pass filter, and then achieves physical separation through a high-low frequency splitter, thereby ensuring that the high-bandwidth media stream and the intermediate frequency control stream do not interfere with each other.

[0021] To address the challenges of high-power power transmission switching noise easily overwhelming information and crosstalk between multiple converters, this invention introduces a time-division duplex cooperation mechanism based on microscopic time-domain segmentation multiplexing. The system divides the communication time axis into alternating independent time slots, allowing the DAB converter and the battery-side Buck converter to transmit information alternately in different time slots. During non-communication time slots, the converter only maintains high-frequency continuous switching operation to perform high-power transmission and does not modulate information. For example, the DAB converter maintains normal dual-phase-shift power transmission during non-communication time slots and slightly modulates the zero-level time information during dedicated downlink time slots; the battery-side Buck converter maintains single-frequency power transmission during non-communication time slots and performs FSK modulation by switching between two different frequencies during dedicated uplink time slots. Because the uplink FSK signal generated by the battery-side Buck converter, after transmission through a high-impedance topology network and long-distance cables, is overwhelmed by high-power high-frequency switching noise at the motherboard end, it exhibits a weak feedback signal. To address this, the mother receiver initiates sampling within a specific uplink detection window synchronized with hardware timing, and applies a squared amplitude moving average filtering algorithm. This algorithm's window width is perfectly synchronized with the power switching cycle. Utilizing the physical characteristic that the integral mean of high-power switching noise is zero over a complete cycle, it precisely filters out periodic switching ripple by integrating and averaging the sampled values ​​within a single cycle to extract the low-frequency feedback signal envelope. Real-world testing shows that, under 1kW-level high-power conditions, the uplink decoding bit error rate is as low as 10%. -6 The order of magnitude ensures the robustness of the system's operation from both the physical and algorithmic layers.

[0022] Through the comprehensive design of "ripple multiplexing, time-frequency alignment, and heterogeneous current splitting" described above, this invention significantly reduces cable weight and system cost while achieving deterministic, highly reliable, and lossless collaborative transmission of power, control, feedback, and video streams within a single-core physical channel. Compared to traditional solutions that require heavy LC filters weighing several kilograms to achieve single-core communication, this invention reduces the size of underwater end-filter hardware by more than 70% through switching ripple modulation and algorithmic noise reduction, significantly reducing the drag burden on the tethered cable and the number of penetrations in the sealed compartment, thereby significantly improving the overall mobility and system reliability of the tethered underwater robot. This invention is not only applicable to tethered underwater robots (ROVs) but can also be widely used in scenarios requiring high-power power transmission and multi-stream data exchange simultaneously through a single wire, such as tethered unmanned aerial vehicles (UAVs), deep-sea exploration platforms, and unmanned mining equipment. Traditional research and development approaches have long regarded the ripple generated by power conversion as "harmful noise" that needs to be filtered out, while the communications field tends to avoid interference by avoiding the power line environment. This invention breaks this mindset by actively transforming the physical characteristics of the power conversion process into communication resources. Through interdisciplinary system-level integration and deep coupling of timing synchronization algorithms, it achieves for the first time the four-in-one coordinated transmission of high-power electrical energy, ultra-low latency control flow, highly robust state feedback flow, and high-bandwidth video stream on a single-core cable.

[0023] Other beneficial effects of the embodiments of the present invention will be further described below. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the communication and communication architecture of a tethered underwater robot according to an embodiment of the present invention.

[0025] Figure 2 This is a schematic diagram of the time slot division for duplex communication of an underwater robot according to an embodiment of the present invention.

[0026] Figure 3a This is a circuit topology diagram of a dual active bridge converter according to an embodiment of the present invention.

[0027] Figure 3b This is a timing diagram of a switch drive based on data modulation according to an embodiment of the present invention.

[0028] Figure 3c This is a diagram of the system equivalent discrete-time model according to an embodiment of the present invention.

[0029] Figure 4a This is a comparison diagram of the downlink TPC modulated load voltage waveforms according to an embodiment of the present invention.

[0030] Figure 4b This is a waveform diagram of the downlink TPC modulated inductor current according to an embodiment of the present invention.

[0031] Figure 5aThis is a half-bridge circuit topology diagram according to an embodiment of the present invention.

[0032] Figure 5b This is an uplink FSK switching timing diagram according to an embodiment of the present invention.

[0033] Figure 5c This is an equivalent discrete-time circuit diagram of an embodiment of the present invention.

[0034] Figure 6a This is a diagram illustrating the downlink received signal filtering effect of an embodiment of the present invention.

[0035] Figure 6b This is a diagram illustrating the uplink received signal filtering effect of an embodiment of the present invention.

[0036] Figure 7a This is a three-dimensional structural diagram of the tethered underwater robot according to an embodiment of the present invention.

[0037] Figure 7b This is a cross-sectional view of the sealed pressure chamber and internal components according to an embodiment of the present invention.

[0038] Figure 8a This is a screenshot of the original waveform measured by an oscilloscope according to an embodiment of the present invention.

[0039] Figure 8b This is a comparison chart of theoretical analysis and actual measurement of downlink and uplink waveforms in an embodiment of the present invention.

[0040] Figure 8c This is a waveform comparison diagram before and after moving average processing according to an embodiment of the present invention.

[0041] Figure 9 This is the overall flowchart of the method for hybrid transmission of power and multi-stream data for tethered underwater robots according to the present invention. Detailed Implementation

[0042] The embodiments of the present invention will be described in detail below. It should be emphasized that the following description is merely exemplary and not intended to limit the scope and application of the present invention.

[0043] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of the present invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0044] To address the shortcomings of traditional technologies, such as poor maneuverability due to heavy tether cables, high latency in underwater real-time control, limited video transmission bandwidth, and weak communication reliability in high-power deep-sea environments, this invention provides a method and system for hybrid power and multi-stream data transmission based on an underwater robot tether rope, solving the following specific technical problems: Addressing the compatibility issue of single-core tethered cables with heterogeneous multi-stream underwater data: To meet the needs of tethered underwater robots operating in deep sea environments for simultaneous transmission of power, control commands, sensor status, and high-definition video, this invention aims to construct a hybrid modulation framework integrating switch-ripple-based power line communication (TPC) and broadband power line communication (PLC). By complementaryly applying multiple communication technologies on a single tethered cable, it achieves the coordinated transmission of high-power electrical energy and multi-characteristic data streams without increasing cable weight.

[0045] Establishing a deterministic, low-latency channel to meet the requirements of precise underwater control: Addressing the millisecond-level uncertain latency inherent in traditional PLC solutions when processing real-time commands such as thruster control, this invention aims to utilize the switching characteristics of the underwater power converter to implement a power-to-information simultaneous transmission technology based on switching ripple. By modulating the switching actions of the power transistors (such as zero-level time modulation of the bridge arm voltage), a microsecond-level downlink communication link is established. This ensures a high degree of real-time performance and determinism in command transmission between the mother ship control unit and the underwater robot actuators.

[0046] Eliminating interference from high-power switching noise in deep-sea environments on uplink monitoring signals: Addressing the issue of electromagnetic interference generated by high-current power conversion at underwater robots easily overwhelming uplink and downlink switching ripple signals, this invention proposes a synchronous control strategy combining time-division duplexing and frequency decoupling. By precisely allocating the signal detection window within the power conversion cycle, it ensures that uplink sensor status data (such as depth and attitude) and high-definition video streams can still be clearly extracted against a strong noise background, achieving stable and reliable bidirectional communication.

[0047] Achieving lightweight integration of underwater module communication and power hardware: Addressing the challenges of extremely limited space in the pressure chamber of underwater robots and the difficulty in arranging traditional large-volume isolation filters, this invention aims to simplify the underwater coupling interface by reusing existing power conversion circuits as the communication physical layer. This significantly reduces the size and weight of the underwater system while minimizing the number of penetrations through the sealed chamber, thereby improving the overall mobility and system reliability of the tethered underwater robot.

[0048] See Figures 1 to 9 This invention provides a method for hybrid power and multi-stream data transmission based on an underwater robot tethering tether. The tethered underwater robot is connected to a central control station via a single-core cable. The method includes the following steps: Step S1. Transmit DC power through the single-core cable and form a switching ripple generated by the interaction of multiple heterogeneous power converters on the DC power; wherein, the multiple heterogeneous power converters include at least a bus-side dual active bridge (DAB) converter and a battery-side Buck converter, and the switching ripple includes downlink control ripple information and uplink state feedback ripple information alternately modulated by the DAB converter and the battery-side Buck converter according to a micro-time domain segmentation multiplexing strategy.

[0049] In some embodiments, the power converter in step S1 may be a dual active bridge converter, whose switching frequency may be configured to be on the order of 100kHz. The single-core cable may be a coaxial cable, whose inner core and outer shielding mesh respectively form positive and negative current loops, and at the same time serve as a unified transmission medium for DC power and switching ripple.

[0050] Step S2. During downlink transmission, the parent control center utilizes a power-information co-transmission technology based on switch ripple to adjust the switch ripple characteristics online by modulating the switching action parameters of the power switches in the power converter. Downlink control commands are embedded into the switch ripple and transmitted to the underwater robot via the single-core cable. As an example, the circuit topology, switch drive timing, and equivalent discrete-time model of the dual active bridge converter can be described as follows: Figure 3a , Figure 3b , Figure 3c As shown, the load voltage and inductor current modulation waveform can be represented as follows: Figure 4a , Figure 4b As shown.

[0051] In some embodiments, the switching action parameters of the power switch in the modulated power converter in step S2 specifically include: by fine-tuning the zero-level time or phase shift angle of the bridge arm voltage in the power converter, the digital bits of the downlink control command are mapped to the waveform distortion characteristics of the output voltage ripple, wherein different digital logics correspond to different zero-level time modulation amounts or phase shift angle offsets of the bridge arm voltages, and the modulation does not change the power transmission.

[0052] Step S3. During uplink transmission, the underwater robot injects the sensor status data, modulated by frequency shift keying, into the single-core cable in the form of switching ripple via an energy storage or power drive converter, and transmits it back to the mother control center. As an example, the topology of the Buck half-bridge circuit can be as follows: Figure 5a As shown, its FSK switching timing can be as follows: Figure 5b As shown, the equivalent discrete-time circuit model can be represented as follows: Figure 5c As shown.

[0053] In some embodiments, the step S3, which involves injecting sensor state data modulated by frequency shift keying via a Buck half-bridge circuit into a single-core cable, specifically includes: the underwater robot end, through a Buck half-bridge circuit, switching between at least two different preset carrier frequencies according to the sensor data bits to be transmitted back, generating voltage switching ripple in a frequency shift keying manner and injecting it into the single-core cable.

[0054] Step S4. Integrate the broadband power line communication module to superimpose the high-definition video stream onto the DC bus of the single-core cable via a high-frequency carrier signal, transmitting it in parallel with the downlink switching ripple (switching ripple generated by the DAB converter at the bus end) and the uplink switching ripple (battery port voltage switching ripple generated by the battery-side converter at the underwater robot end). As an example, the measured waveform including the PLC high-frequency carrier can be shown as follows: Figure 8a As shown.

[0055] In some embodiments, the frequency decoupling technique described in step S4 for isolating the high-frequency power line communication signal from the intermediate-frequency power conversion signal in the frequency domain specifically includes: configuring the operating frequency band of the power line communication module to be higher than the switching frequency and main harmonic frequency band of the power converter; firstly filtering out the high-frequency media signal through a hardware low-pass filter at the receiving end of the mother control center; and then further separating the remaining high-frequency power line communication signal from the intermediate-frequency switching ripple signal through a high-low frequency splitter or a low-pass filter.

[0056] Step S5. The transmission timing of the downlink and uplink is coordinated using a hybrid time-division duplex strategy, and frequency decoupling technology is used to isolate the high-frequency power line communication signal from the intermediate-frequency power conversion signal in the frequency domain, achieving coexistence of multi-stream data and reliable bidirectional communication. As an example, the time slot division mechanism can be as follows: Figure 2 As shown, the effects of downlink and uplink filtering can be seen as follows: Figure 6a and Figure 6b As shown, the waveform comparison before and after moving average processing can be seen as follows: Figure 8c As shown.

[0057] In some embodiments, the coordination of the transmission timing of the downlink and uplink via a time-division duplex strategy in step S5 specifically includes: dividing the communication time axis into alternating independent time slots, allowing the dual active bridge (DAB) converter and the battery-side Buck converter to transmit information alternately in different time slots, with a small time interval between the time slots. In communication time slots not allocated to the converter, the converter only maintains high-frequency continuous switching operation to perform high-power transmission and does not modulate information. For example, the DAB converter maintains normal dual-phase-shift transmission power in non-communication time slots, and slightly changes the zero-level time in a dedicated downlink control window (time slot) to modulate downlink control commands; the battery-side Buck converter maintains single-frequency transmission power in non-communication time slots, and switches its switching frequency between two different frequencies in a dedicated uplink communication time slot to perform FSK modulation.

[0058] In some embodiments, step S5 further includes a noise suppression step for the uplink received signal: after the mother control center receiver samples the injected feedback TPC switching ripple, it applies a moving average filtering algorithm to process the sampled signal; the filtering window width of the moving average filtering algorithm is set to be synchronized with the power switching cycle, and by integrating and averaging the sampled values ​​within a complete switching cycle, the periodic switching ripple is filtered out by utilizing the characteristic that the integral mean of the power switching noise within a complete cycle is zero, and the basically constant low-frequency feedback signal envelope is extracted. Further, the moving average filtering algorithm specifically includes: keeping the sampling frequency synchronized with the power switching cycle, collecting a fixed number of sampling points in each power switching cycle; using each complete power switching cycle as the filtering window, calculating the arithmetic mean of all sampling points in the current window as the filtered output value for that cycle; then sliding the filtering window sequentially to the next power switching cycle, repeating the above calculation process, thereby realizing cycle-by-cycle noise filtering and signal envelope extraction.

[0059] See Figures 1 to 8c The present invention also provides a method and system for hybrid transmission of power and multi-stream data based on an underwater robot tether, comprising: a mother control center, including a dual active bridge converter and a control unit; a single-core cable connecting the mother control center and the underwater robot end; and the underwater robot end, including a power electronic converter, a battery-side Buck half-bridge circuit, a power line communication module, and a load.

[0060] The mother control center is configured to: transmit DC power to the underwater robot via a single-core cable through the dual active bridge converter; and utilize a power-to-information transmission technology based on switching ripple to embed downlink control commands into the voltage ripple for transmission by modulating the operating parameters of the switching transistors in the dual active bridge converter. As an example, its switching drive timing can be as follows: Figure 3bAs shown, the modulation waveform can be as follows: Figure 4a , Figure 4b As shown.

[0061] The underwater robot end is configured to: inject sensor status data modulated by frequency shift keying (FSK) into a single-core cable via the battery-side Buck half-bridge circuit for transmission back in the form of switching ripple (e.g., its FSK switching timing can be as follows). Figure 5b As shown, the equivalent circuit model can be as follows: Figure 5c (As shown); and the high-definition video stream is transmitted via high-frequency carrier superimposed on a single-core cable through the power line communication module (measured waveform as shown). Figure 8a (As shown).

[0062] The system is also configured to coordinate downlink and uplink transmission timings using a time-division duplex strategy (as an example, the time slot division is as follows). Figure 2 (As shown), and frequency decoupling is used to isolate the high-frequency power line communication signal from the intermediate frequency power conversion signal. Simultaneously, a moving average filtering algorithm is employed to suppress noise in the uplink received signal (see details). Figure 6a , Figure 6b and Figure 8c The filtering effect is shown.

[0063] In some embodiments, the mother control center maps the digital bits of the downlink control command to the waveform distortion characteristics of the output voltage ripple by finely adjusting the zero-level time or phase shift angle of the bridge arm voltage of the switching transistor in the dual active bridge converter. Different digital logics correspond to different zero-level time modulation amounts or phase shift angle offsets of the bridge arm voltages, and the modulation does not change the average direction of the output voltage vector.

[0064] In some embodiments, the Buck half-bridge circuit at the underwater robot end is configured to: switch between at least two different preset carrier frequencies based on the sensor data bits to be transmitted back, generate switching ripple in a frequency shift keying manner, and inject it into a single-core cable; the mother control center further includes a receiver configured to sample the injected switching ripple and apply a moving average filtering algorithm to filter out periodic switching noise, wherein the filtering window width of the moving average filtering algorithm is set to be synchronized with the power switching cycle, and by integrating and averaging the sampled values ​​within a complete switching cycle, the periodic switching ripple is filtered out by utilizing the characteristic that the integral mean of the power switching noise is zero within the complete cycle, thereby extracting a basically constant low-frequency feedback signal envelope.

[0065] In some embodiments, the time-division duplex strategy specifically includes: dividing the communication time axis into alternating independent time slots, so that the dual active bridge (DAB) converter and the battery-side Buck converter alternately transmit information in different time slots, and maintaining a certain small time interval between the time slots. In communication time slots not allocated to this converter, the converter only maintains high-frequency continuous switching operation to perform high-power transmission and does not modulate information.

[0066] The main technical advantages of this invention are as follows: Addressing the challenge of coexisting high-power electrical energy and multi-stream data on a single-core cable of a tethered underwater robot, this invention proposes a hybrid modulation architecture integrating "time-varying zero-level switching ripple energy-signal co-transmission (TPC), broadband power line communication (PLC), and frequency-shift keying switching ripple energy-signal co-transmission." By deeply multiplexing the inherent switching action of the power converter, downlink control commands are directly embedded in the switching ripple, achieving microsecond-level deterministic low-latency transmission and completely eliminating the millisecond-level protocol stack latency of traditional PLC solutions. Simultaneously, by introducing a time-division duplex cooperation mechanism and a frequency decoupling strategy, transient crosstalk between uplink and downlink communication switches is precisely avoided in the time domain, and high-frequency PLC signals are isolated in the frequency domain, effectively solving the problem of high-power switching noise suppressing status feedback signals and high-definition video streams. Therefore, this invention achieves integrated collaborative transmission of power, control, feedback, and video streams without increasing cable weight, and reduces the size of underwater communication hardware by more than 70%, significantly improving the mobility, real-time response accuracy, and communication reliability of the tethered platform.

[0067] The following further describes the implementation, working principle, and advantages of specific embodiments of the present invention.

[0068] Traditional solutions typically require multi-core cables or extremely bulky impedance filters installed on single-core cables to separate signals, which increases the robot's weight and reduces system response speed. The key difference of this invention is that it abandons bulky physical isolation and instead utilizes the switching characteristics of power electronic converters for "software-defined modulation," combined with "time-domain synchronous sampling" and "moving average denoising" algorithms to achieve logical decoupling of multiple links. This significantly reduces hardware size while achieving microsecond-level deterministic control delay. To address the challenge of coexisting high-bandwidth video streams and ultra-low-latency control streams under strong electromagnetic interference in single-core cable transmission for tethered underwater robots, this invention proposes a heterogeneous multi-stream power and signal transmission architecture with complementary physical characteristics. Its core innovation lies in moving away from simple reliance on traditional power line carrier (PLC) superposition and instead deeply reusing the inherent switching actions of power electronic converters. By fine-tuning the zero-level time of the bridge arm voltage, high-priority control commands are transformed into the intrinsic properties of power ripple, eliminating the millisecond-level latency introduced by traditional protocol stacks at the underlying physical mechanism. Simultaneously, a time-division duplex cooperation mechanism that follows the power converter's switching cycle precisely avoids the suppression of weak uplink signals by transient noise from power switching in the time domain, and utilizes the decoupling of the broadband PLC in the frequency domain to achieve high-volume data transmission. This comprehensive design of "ripple multiplexing, time-frequency alignment, and heterogeneous splitting" achieves, for the first time, deterministic, highly reliable, and lossless collaborative transmission of power, control, and multi-path feedback streams without altering the physical topology of the single-core cable.

[0069] The core key points of this invention are further reflected in three levels of innovation: At the system-level architecture, this invention integrates the hardware topology and logic architecture of simultaneous transmission of signals based on switching ripple (TPC) and broadband power line communication (PLC) on a single tethered cable; at the method level, by finely adjusting the zero-level time of the switching arm voltage of the power electronic converter (such as a dual active bridge converter) to embed the downlink control bit stream, and this modulation does not change the average direction of the output voltage vector, which is the core means to achieve microsecond-level ultra-low latency; at the hardware level, this invention designs a filter network with multiplexed power loop and frequency division multiplexing function, which can simultaneously isolate / pass intermediate frequency switching ripple signals (100 kHz level) and high frequency PLC signals (MHz level), which is the physical basis for achieving lightweight integration.

[0070] To address this, this invention proposes a hybrid modulation architecture called "Tethered Talk," the core of which lies in integrating three complementary modulation techniques through a single-core cable: the downlink utilizes a phase-shifting full-bridge converter to implement simultaneous energy and signal transmission based on switching ripple, and embeds control commands through the zero-level time of the dual-modulation bridge arm voltage to achieve extremely low-latency command transmission; the uplink uses frequency shift keying (FSK) technology to transmit low-speed sensor status data back, and integrates a broadband power line communication (PLC) module to transmit high-definition video streams through orthogonal frequency division multiplexing (OFDM); the coordination mechanism introduces a time-division duplex strategy to coordinate the transmission of downlink control and uplink status data, and uses frequency decoupling technology to ensure that high-frequency PLC signals and intermediate-frequency power conversion signals do not interfere with each other.

[0071] Compared with existing technologies (such as those relying solely on PLCs or physical isolation via multi-core cables), this invention offers significant performance advantages. First, addressing the conflict between balancing high-bandwidth data and high-real-time control in single-core cable environments, this invention introduces Transmission-to-Consciousness (TPC) technology based on switching ripple, utilizing the inherent switching action of dual active bridge converters as signal carriers. Since control commands are directly embedded in the power switching sequence and do not involve complex network protocol stacks, downlink command latency is drastically reduced from milliseconds in existing PLC technology to microseconds (measured at 10 μs ± 1 μs), fundamentally ensuring the real-time response speed and closed-loop stability of tethered underwater robots in complex deep-sea currents. Second, this invention solves the problem of interference from high-power transmission to weak communication signals through deep spatiotemporal coupling. By utilizing decoupling in the frequency domain of the coupling circuit and peak-shifting sampling in the time domain using a time-division duplex strategy, uplink and downlink transmission-to-consciousness data can avoid transient pulse crosstalk caused by power switching. This "converter-transmitter" multiplexing design not only eliminates the drag force burden caused by bulky multi-core cables in traditional solutions, but also significantly reduces the size and weight of the underwater robot's communication hardware (measured reduction of over 70% in the volume of communication-related hardware). Through this causal hybrid modulation mechanism, this invention achieves highly reliable synchronous transmission of power, control, and multi-flow feedback within an extremely limited single-core physical channel.

[0072] This architecture can significantly reduce cable weight and system costs while ensuring a continuous power supply to the platform and highly reliable bidirectional transmission of high-definition video and precise control commands. It is mainly used in scenarios such as tethered underwater robots (ROVs), tethered drones, deep-sea exploration platforms, and unmanned mining equipment.

[0073] The following further explains the detailed working principle of this invention. The single-core cable simultaneous transmission system proposed in this invention is mainly based on the principle of heterogeneous hybrid modulation and time-frequency domain synchronous cooperation, achieving multi-stream data transmission through the physical characteristics of a multiplexed power converter. For example... Figure 1As shown, the system is an integrated system consisting of a mother controller, a single-core tethered cable, and an underwater robot end (ROV). Its core power unit is a dual active bridge (DAB) converter, and the output is connected to the single-core cable through a coupling network composed of capacitors and other components. This architecture cleverly utilizes the DC component of the cable to transmit power, while using the switching ripple superimposed on the DC and high-frequency carrier to transmit multiple heterogeneous data, achieving deep integration of power and signal in the physical channel.

[0074] The downlink employs zero-level time modulation technology for the bridge arm voltages based on a dual active bridge converter with switched ripple energy transmission (TPC). For example... Figures 3a to 3c As shown, the mother controller finely adjusts the zero-level time of the bridge arm voltage of the DAB converter power transistor in each switching cycle according to the binary data to be transmitted: when transmitting logic "1", the zero-level time of the bridge arm voltage is set to... t d1 When sending logic "0", it is set to t d2 This modulation directly alters the edge transition times of the output voltage waveform, thus embedding digital information into the output voltage ripple. Since this process does not involve the network protocol layer, it ensures that control commands have deterministic delays at the microsecond level.

[0075] The uplink utilizes frequency shift keying-based simultaneous transmission of signal and energy (TPC-FSK) technology and injection techniques to transmit low-speed status data from the ROV end. The half-bridge circuit at the ROV end injects a TPC voltage signal modulated by sensor data into the cable. Due to severe switching noise generated by the DAB at the mother end of the cable, the system employs a moving average algorithm at the receiving end to process the power waveform in real time, canceling periodic ripple interference and thus accurately extracting a smooth uplink FSK signal from the interfered signal.

[0076] For high-definition video and other data-intensive services, the system integrates a broadband power line communication (PLC) module via a high-frequency coupling interface. The PLC module utilizes an ultra-high frequency band of 2–68 MHz for data transmission, a frequency significantly higher than the switching frequency of the TPC (approximately 50–100 kHz). Through deep decoupling in the frequency domain, PLC signals do not interfere with signals from different TPCs, achieving a "four-in-one" function that simultaneously transmits power, control, status feedback, and high-definition images over a single-core cable.

[0077] To address the near-end crosstalk issue within a single-core channel, the system also introduces measures such as... Figure 2 The time-division duplex (TDD) cooperation logic shown divides a complete control cycle into downlink command time slots and uplink data time slots. This precise timing alignment based on the power switching cycle ensures zero packet loss and high robustness in heterogeneous data stream transmission under the background of high-power transmission of several kilowatts.

[0078] At the system implementation level, this invention provides a heterogeneous power and communication simultaneous transmission system for tethered underwater robots based on a single-core cable. Through deep fusion of the time, frequency, and spatial domains, it achieves integrated transmission of high-power energy transmission, high-real-time downlink control flow, high-robust uplink feedback flow, and high-bandwidth media stream on a single coaxial cable. The system consists of a ground control unit at the mother end, a single-core coaxial cable, and an underwater robot end. The mother end power source employs a dual active bridge (DAB) converter, such as... Figure 3a As shown, the converter includes two full-bridge circuits on the primary and secondary sides, as well as a high-frequency transformer. This scheme uses gallium nitride (GaN) power devices, whose high-frequency characteristics support a switching frequency of 100 kHz, providing a high-resolution time base for embedding communication features. The single-core transmission link utilizes a single coaxial cable as a unified medium. The inner core and outer shielding mesh of the cable respectively form the positive and negative loops of the current, and simultaneously serve as carriers of heterogeneous signals. The underwater injection unit is as follows... Figure 5a As shown, the underwater robot's battery pack is equipped with a Buck half-bridge circuit, which can actively inject weak switching ripple for signal feedback without interfering with the DC power flow.

[0079] The downlink control flow employs a switching ripple-reducing simultaneous transmission technology based on the zero-level time. For example... Figure 3b As shown, while maintaining 100 kHz energy exchange, the mother-side controller fine-tunes the zero-level time or phase shift angle of the secondary-side switching transistor's bridge arm voltage according to control commands (fine-tuning amount, for example, 200 ns), resulting in a slight phase shift or amplitude change in the load-side voltage ripple. The downlink control link adopts the Transmit-Transmit-Power (TPC) technology based on switching ripple. Its core modulation parameter, the bridge arm voltage zero-level time modulation amount Dtd, is set in the range of 50 ns to 500 ns, with a preferred value of 200 ns. The setting of this parameter range has a rigorous physical basis and engineering logic: The necessity of the lower limit (50 ns): Since the system uses GaN (gallium nitride) power devices, although they have nanosecond-level switching characteristics, they are limited by the clock resolution of the controller's PWM generator (e.g., a 100MHz clock step of 10 ns) and the basic safety dead-time requirement to prevent half-bridge shoot-through. The modulation amount needs to be greater than 50 ns to ensure the feasibility and safety of the signal at the physical layer. The upper limit (500ns) constraint: At an operating frequency of 100 kHz, a complete switching cycle is 10 μs. 500ns represents only 5% of the cycle, ensuring that the increased zero-level time of the bridge arm voltage results in extremely low body diode freewheeling losses, and will not have a significant negative impact on the overall power transfer efficiency of the converter (1kW level). Figure 4aAs shown, digital logic "0" and "1" are mapped to different waveform distortion characteristics. This method does not require an additional communication carrier generator and directly reuses the power switching action as the information source. Since the modulation period is aligned with the switching period, the downlink control delay is only 10 μs (measured at 10 μs ± 1 μs). Through this power-to-information transmission technology based on switching ripple, utilizing the inherent switching action of the DAB converter as the signal carrier, control commands are directly embedded in the power switching sequence without involving complex network protocol stacks. The downlink command delay is significantly reduced from the millisecond level of existing PLC technology to the microsecond level, fundamentally ensuring the real-time response speed and closed-loop stability of tethered underwater robots in complex deep-sea current fields.

[0080] Regarding downlink communication capabilities, this invention quantitatively analyzes the reliability of the 200ns zero-level-time modulation (Dtd) by establishing an equivalent channel model that includes the distributed inductance and capacitance of the cable. Simulation and field measurements show that at a 100kHz switching frequency, the voltage ripple phase offset generated by this modulation at the end of a 50-meter single-core cable is much higher than the dynamic noise threshold at the receiver. Combined with a differential decision algorithm based on high-speed oversampling, a gain of over 12dB in signal-to-noise ratio can be achieved. To meet real-time control requirements, the downlink command adopts a lightweight short frame structure of 16-32 bits, including a start bit, opcode, payload, and CRC check bit. At a rate of 100kbps, the physical layer transmission time of a single command packet is only 0.16ms-0.32ms. Furthermore, since TPC modulation directly acts on the power switching sequence, the packet encapsulation and queuing delays of the traditional communication protocol stack are eliminated, thus achieving nanosecond-level deterministic response at the physical layer. In addition, the system supports adaptive modulation depth adjustment. When increased link interference is detected, the modulation amount can be dynamically increased in steps within the range of 50ns-500ns, or switched to multi-level dead-zone modulation mode to increase the bandwidth by a factor of two, ensuring the robustness of heterogeneous data transmission under complex operating conditions.

[0081] To address the near-end crosstalk problem causing signal interference on single-core cables, this solution is designed as follows: Figure 2 The diagram illustrates a time-division duplex (TDM) cooperation mechanism. At the beginning of each switching cycle, the mother terminal performs TPC modulation to send commands (control window). During the voltage stabilization period after the switching action, the mother terminal receiver turns on, and the underwater robot terminal uses frequency shift keying (FSK) modulation (10 kHz / 20 kHz). By avoiding the voltage spikes generated during the power transistor switching, the accuracy of signal extraction is significantly improved. Due to the significant 100 kHz switching noise on the single-core cable, the uplink feedback signal (TPC-FSK) is often overwhelmed. The mother terminal receiver first filters out high-frequency media signals above 2 MHz using a hardware low-pass filter, and then applies a moving average filtering algorithm (such as...). Figure 8c(As shown). The window width of this algorithm is precisely set to one switching cycle (10 μs). Since the integral mean of the switching noise is zero over the entire cycle, and the low-frequency feedback signal is basically constant within the window, this processing can completely "smooth out" the power ripple.

[0082] The digital signal processor of the mother-end control unit executes a moving average filtering algorithm, the specific steps of which include: the sampling window of the moving average filtering algorithm is a unit switching cycle. T s The voltage signal is sampled continuously at 200 points; that is, the sampling frequency is 200 / T s The arithmetic mean of these 200 points is calculated as the filtered output value at that moment. The number of sampling points can be dynamically adjusted according to the system requirements. N The sampling interval is T s / N .

[0083] At the signal processing level, the algorithm takes as input a raw signal sampled from a single-core cable, which contains strong switching noise. V raw (t), the output is the smoothed envelope signal after filtering out periodic power noise. V filtered (t). In specific implementation, the algorithm is implemented in a digital processor through discrete formulas. By utilizing physical symmetry, the algorithm cancels out strong electromagnetic interference of 100 kHz, since the power ripple of the DAB converter integrates to zero over a full cycle, thus enabling high-definition restoration of the 10k / 20kHz uplink feedback signal buried in noise.

[0084] In the uplink design, this invention will use the carrier frequency f up The 10kHz to 20kHz frequency band was selected based on the principle of frequency domain avoidance: the switching frequency of the mother DAB converter is 100kHz, and its power noise and higher harmonics are mainly concentrated in the mid-to-high frequency range, while the conducted interference floor in the low-frequency range below 20kHz is relatively low, providing a natural low-noise window for the weak uplink switching ripple. In the receiver algorithm flow, the system first performs square amplitude processing on the original signal y[n] after AC coupling sampling, and then implements moving average filtering. The core physical mechanism of this algorithm is: utilizing the characteristic that the output ripple of the DAB converter has periodicity and zero mean in idle mode, by setting the power switching period... TA strictly equal-length integration window of s (10μs) effectively cancels periodic intermediate frequency power interference in the time domain. The processed signal forms a smooth energy envelope, significantly improving the signal's eye diagram opening. Finally, the receiver employs a low-complexity threshold detection method, performing logical judgments based on the envelope amplitude at the end of each symbol period. This algorithm, combining "low-frequency noise reduction" and "time-domain energy smoothing," ensures that uplink FSK data still possesses a clear decision threshold and an extremely low bit error rate even under 1kW high-power switching conditions.

[0085] like Figure 6b As shown, the processed waveform reveals a clear pulse envelope from the chaotic noise, ensuring reliable transmission of feedback data such as depth and attitude. Through deep coupling in the spatiotemporal dimension, utilizing the decoupling of the coupling circuit in the frequency domain and the staggered sampling in the time domain using a time-division duplex strategy, the uplink high-definition video stream and sensor status data can avoid transient pulse noise generated by power switching. This "converter as transmitter" multiplexing design not only eliminates the drag burden caused by bulky multi-core cables in traditional solutions, but also significantly reduces the size and weight of the underwater robot's communication hardware (measured reduction of over 70% in the volume of communication-related hardware).

[0086] For video backhaul requiring large amounts of data, the system integrates a power line communication (PLC) module. The PLC signal occupies the 2–68 MHz frequency band, significantly higher than the downlink TPC control signal (100 kHz) and uplink TPC feedback signal (10–20 kHz), achieving frequency domain isolation. For example... Figure 8a As shown, the PLC's high-frequency carrier is directly superimposed on the rippled DC bus. At the receiving end, a high-low frequency splitter achieves physical isolation, ensuring that the video stream, control stream, and power stream do not interfere with each other. Through this causal-correlated hybrid modulation mechanism, this invention achieves highly reliable synchronous transmission of power, control, and multi-stream feedback within a single-core physical channel.

[0087] Figure 1This section showcases the energy and signal transmission architecture of the tethered underwater robot, illustrating the system's global physical connections and logical composition. The main unit (control center) includes an energy management unit and a control unit. The ground controller modulates control commands into the power stream using switching ripple energy and signal transmission technology. A single-core tether cable serves as the sole physical medium, simultaneously carrying DC power, intermediate-frequency control, low-frequency feedback, and high-frequency media streams. The diagram illustrates the frequency domain distribution of the signals on the single cable, achieving coexistence of heterogeneous data through frequency decoupling. The underwater unit (robot side) demonstrates the robot's integrated logic. The power electronic converter transforms high-voltage DC into the required system voltage while simultaneously acting as a command receiver. Attitude and depth data acquired by sensors are transmitted back via injection circuitry. This architecture eliminates the reliance on multi-core cables inherent in traditional tethered systems through hardware multiplexing, significantly reducing cable fluid resistance and system weight.

[0088] Figure 2 This is a schematic diagram of time slot division for full-duplex communication of an underwater robot. To achieve full-duplex communication and suppress noise, the system divides each switching cycle into two time slots: a control window at the beginning of the cycle is used for the parent end to send commands, and a detection window in the latter half of the cycle, where the voltage is stable, is used for the parent end to sample the feedback signal from the underwater end. This spatiotemporal decoupling mechanism ensures high signal-to-noise ratio transmission of weak data streams under high-power backgrounds.

[0089] Figure 3a This is the circuit topology of a dual active bridge (DAB) converter, used to achieve efficient power conversion and isolation. Figure 3b The timing diagram for a data modulation-based switch drive demonstrates how control bits "0" and "1" can be embedded into the power waveform by fine-tuning the phase or dead-time state of the switch transistor. Figure 3c This is an equivalent discrete-time model of the system, used to quantitatively analyze the voltage ripple characteristics on a single-core cable, supporting accurate demodulation of communication signals.

[0090] Figure 4a and Figure 4b The simulation waveforms of voltage and current at the load end of a single-core cable are shown when downlink data modulation is performed using switching ripple energy transmission technology at the mother end. Figure 4a The diagram shows the load voltage waveform, where the black curve represents the steady-state voltage ripple when there is no data transmission, and the red curve represents the voltage waveform after the downlink control data is embedded. By fine-tuning the phase of the switching transistor or the zero-level time of the bridge arm voltage, the peak value and phase of the voltage ripple are identifiable shifts, which serve as the physical carriers of digital logic "0" and "1". Figure 4b The waveform diagram of the inductor current shows the change in the current of the inductor inside the converter under the corresponding operating conditions. The red curve shows that the current produces regular amplitude fluctuations under the modulation effect.

[0091] Figures 5a to 5cThe battery-side Buck half-bridge circuit and the uplink TPC-FSK modulation mechanism were demonstrated. Figure 5a The topology of the Buck half-bridge circuit on the battery side is shown, demonstrating a miniature half-bridge structure composed of switching transistors. It is connected to a single-core cable through a coupling capacitor. This circuit is responsible for converting the low-voltage sensor signal from the robot end into switching ripple and injecting it into the DC power line. It is the hardware foundation for realizing reverse transmission of "energy carrying signal". Figure 5b The FSK switching timing diagram details the uplink frequency shift keying modulation principle: when transmitting logic "0", the switching transistor operates at frequency f0, and when transmitting logic "1", it switches to frequency f1. By distinguishing the frequency dimension, the recognition of the uplink signal in a strong electromagnetic noise environment is effectively enhanced. Figure 5c To obtain the equivalent discrete-time circuit diagram, the FSK injection unit at the robot end, the DAB converter at the mother end, the single-core cable impedance R_coax, and the load R_load were modeled at the system level. This model was used to quantitatively analyze the coupling relationship between the uplink current and the cable voltage waveform, providing theoretical support for the demodulation algorithm of the mother end receiver.

[0092] Figures 6a to 6b The study demonstrates a comparison of the system's processing effects of combined analog and digital filtering on signals at the downlink and uplink receivers. Figure 6a The downlink received waveform diagram shows the voltage signal received by the underwater robot. The black curve is the original ripple signal superimposed with severe power noise, which completely obscures the logical characteristics. The red curve is the waveform after analog filtering and digital algorithm processing, which clearly restores the step characteristics representing the control command, proving the high accuracy of TPC command decoding at the underwater end. Figure 6b The uplink received waveform diagram shows the feedback current signal received by the mother control center. The black curve shows the original waveform affected by the impedance of the single-core cable and the transient interference of the DAB switch. The red curve is the envelope signal after filtering. The processed waveform successfully filters out high-frequency spurious interference, so that the uplink feedback current still has a clear decision threshold in a strong noise environment.

[0093] Figure 7a The diagram shows the overall three-dimensional structure of the tethered underwater robot, illustrating its external design and layout. The single-core tethered cable interface on its top serves as a unified physical entry point for energy and multiple heterogeneous data streams. Figure 7b The cross-sectional view of the sealed pressure chamber and its internal components shows the integration of the underwater end hardware. Its compact internal space significantly improves the space utilization of the pressure chamber by reducing the volume of the hardware filters.

[0094] Figures 8a to 8c The system experimental results under full-function integrated conditions are presented, including the measured waveforms and analysis of the downlink and uplink under real-world conditions containing high-bandwidth PLC data packets. Figure 8aThe image shows a screenshot of the original waveform measured by an oscilloscope. The upper curve is the TPC downlink waveform containing the PLC high-frequency carrier, and the lower curve is the waveform after a 500 kHz low-pass filter. It can be seen that the PLC data packet exhibits obvious voltage fluctuations, which can be filtered out by a simple low-pass filter while retaining the complete switching ripple characteristics. This verifies the separability of the high-frequency media stream and the intermediate-frequency control stream in the frequency domain. Figure 8b The graph shows a comparison between theoretical analysis and actual measurement of the downlink and uplink waveforms, illustrating the voltage ripple after filtering. The red curve (measured value) and the black curve (analyzed value) are in high agreement, proving that the established discrete-time circuit model can accurately predict the cable voltage behavior under complex noise environments. Figure 8c The image shows a comparison of the downlink and uplink waveforms before and after moving average processing. The left side shows the clear step logic of the downlink after processing, while the right side shows the stable PWM envelope of the uplink after filtering out DAB switch interference. This intuitively demonstrates that even in the context of PLC signals, the system can still robustly extract key control and feedback data through the time-domain synchronization cooperation mechanism.

[0095] Experimental verification: The following description, in conjunction with specific examples, further illustrates a preferred embodiment of the present invention, a method and system for hybrid transmission of power and multi-stream data based on an underwater robot tether.

[0096] 1. Experimental prototype construction and key parameters To verify the decoupling capability of the method described in this invention under extreme noise environments, this embodiment constructs an experimental platform with a power level of 1 kW. The core of the system adopts a dual active bridge (DAB) converter based on gallium nitride power devices, and its specific experimental parameters are shown in Table 1 below: Table 1. Parameter List of DAB Converter Experimental Platform 2. Detailed operating procedures and working mechanism The operational logic of this verification example is divided into four stages: Link establishment: The mother control center starts the DAB converter and transmits 400V DC power to the ROV end through a 50-meter single-core cable. At this time, the cable has a 100 kHz inherent switching ripple.

[0097] Modulation execution: The mother end fine-tunes the switching transistor drive timing in real time according to the downlink control command; the sensor data at the ROV end is injected into the cable via the Buck half-bridge circuit in FSK mode to modulate the voltage ripple.

[0098] Timing-synchronized sampling: The system starts sampling at the stable voltage moment of each cycle according to the time slot division shown in Figure 2.

[0099] Multi-dimensional signal separation: The PLC video signal of 2-68 MHz is stripped by a hardware low-pass filter at the master end, and then the switching transient noise is filtered out by the moving average algorithm shown in Figure 8c, so as to achieve parallel extraction of control flow, state flow and media flow.

[0100] 3. Comparison of experimental results and beneficial effects Under full-power operation, the following key indicators were measured in this experiment: Command response determinism: The downlink control link latency is always locked within the range of 10μs ±1μs, which solves the problem of increased latency in traditional power line communication when the network is congested.

[0101] Communication robustness: Even with ±5% ripple fluctuations in the inductor current, the moving average preprocessing described in this invention significantly improves the eye diagram opening of the uplink signal, resulting in a decoding error rate as low as 10%. -6 .

[0102] Lightweight benefits: Compared to traditional solutions that require a heavy LC filter weighing 3-5 kg ​​to achieve single-core communication, this invention reduces the size of the underwater end-filter hardware by more than 70% through switching ripple modulation and algorithm denoising.

[0103] Deformation scheme: Under the core architecture of this invention, the downlink modulation method is not limited to zero-level time modulation of the bridge arm voltage. In optional implementations, the modulation parameters can be flexibly switched to phase angle fine-tuning, duty cycle modulation, or switching frequency modulation according to the real-time load of the power converter. Simultaneously, to further improve the transmission throughput of control commands, this invention supports the introduction of multi-level encoding mechanisms (such as quaternary amplitude shift keying or multi-level dead-time modulation), which carry multiple bits of information within a single switching cycle by defining multiple discrete modulation steps, thereby multiplying the bandwidth of the real-time control flow without increasing the switching frequency.

[0104] The proposed simultaneous communication mechanism possesses strong topology adaptability. Its power conversion unit is not limited to single-phase dual active bridge (DAB) converters, but can also be extended to three-phase AC / DC converters, multi-module parallel systems, or non-isolated Buck-Boost, Cuk, and other power topologies. In multi-phase or multi-module parallel systems, this invention supports the use of multi-channel parallel modulation strategies. By alternately embedding control information between different phases or modules, redundancy backup or bandwidth superposition of the communication link can be achieved. Furthermore, the coupling network in the hardware interface can dynamically adjust the filter capacitor and impedance matching parameters according to the cable length and impedance characteristics to adapt to single-core moored cables of varying lengths from several meters to several kilometers.

[0105] For ultra-deep-sea or extremely long-distance transmission scenarios, this invention can also derive a cascaded architecture with relay functionality. By setting up active nodes with TPC capabilities in the middle of long-distance mooring cables, energy and signal regeneration and forwarding are achieved step-by-step. Regarding interference suppression, in addition to the aforementioned time-division duplex strategy, this invention can also incorporate an adaptive noise cancellation algorithm. Utilizing prior predictions of converter ripple at the control end, power noise is deducted in real-time at the receiving end, thereby attempting to achieve full-duplex simultaneous energy and signal transmission during specific time periods.

[0106] As mentioned above, the core of this invention lies in achieving deterministic, highly reliable, and lossless collaborative transmission of power, control, and multi-path feedback streams through a comprehensive design of "ripple multiplexing, time-frequency alignment, and heterogeneous current splitting." Furthermore, this invention also possesses the following features: deep coupling logic between energy transmission and multi-stream data within a single physical channel; utilizing the timing or level switching of internal switching transistors in the power electronic converter as the physical carrier of control information; modulation parameters can be the zero-level time of the bridge arm voltage, phase shift angle, or pulse frequency; the system features a heterogeneous multiplexing architecture spanning frequency bands or time domains, with a single cable simultaneously carrying a low-delay control stream carried by power conversion ripple and a high-bandwidth media stream carried by a high-frequency carrier; and for interference suppression in high-power environments, the system includes a logic feature that synchronizes the communication window with the power switch phase, ensuring reliable uplink signal return even under kilowatt-level power transmission conditions by avoiding or decoupling power noise and signal detection in the time or frequency dimensions.

[0107] In summary, this invention achieves downlink transmission by embedding control commands into voltage ripple through the power switching action of dual active bridge converters; simultaneously, uplink feedback is achieved by injecting frequency-modulated switching ripple into the underwater robot using a Buck half-bridge circuit; and by combining a time-division duplex time slot partitioning mechanism, sampling time avoids power switching noise transients; finally, a high-frequency power line communication module is integrated at the physical layer to achieve decoupled coexistence of power, control, feedback, and video streams within a single physical channel. Compared with existing technologies, the advantages of this invention are as follows: Extremely low deterministic latency: By using TPC technology, the downlink control latency is reduced from milliseconds to microseconds (≤20 μs), eliminating protocol stack processing time and significantly improving the control closed-loop frequency of the robot in dynamic waters; Significant lightweight advantage: Utilizing the inherent ripple communication of the converter, there is no need to install bulky traditional LC filters underwater, reducing the size of communication-related hardware by more than 70% and significantly reducing the dragging burden of the mooring cable; Highly reliable communication quality: Through dual decoupling of the time domain (time division duplex) and frequency domain (moving average filtering), the interference of 1kW-level high-power switching noise on weak state feedback signals is effectively solved, with a bit error rate as low as 10%. -6 This ensures the safety and stability of the system under extreme operating conditions.

[0108] Compared to traditional technologies, this invention primarily addresses the severe engineering conflicts and performance bottlenecks that exist between energy transmission and the transmission of heterogeneous data streams with multiple characteristics in a single-core cable environment for tethered underwater robots. Specifically, it addresses the following four core issues: First, resolving the contradiction between lightweight single-core cables and data diversity, i.e., simultaneously and in parallel transmitting high-voltage, high-power energy, microsecond-level ultra-low latency control commands, highly robust status data, and Mbps-level high-definition video streams within a single physical channel. This is the primary challenge that existing technologies have failed to solve. Second, addressing the high latency and uncertainty issues in real-time control using traditional PLC technology. Existing technologies based on IEEE... Broadband power line communication schemes such as 1901 suffer from extremely complex protocol stacks and media access control layer contention mechanisms, resulting in control command transmission delays typically on the order of milliseconds and exhibiting randomness. For thruster vector control, which requires extremely high real-time performance, this delay leads to poor system dynamic response, decreased obstacle avoidance performance, and even instability. Third, there is the issue of suppressing strong electromagnetic interference generated by high-power switching actions. Under high-power transmission conditions of several kilowatts, the severe switching ripple and high-frequency noise generated by the underwater power electronic converter often cover the spectrum of traditional communication signals. This causes weak uplink signals (such as depth and attitude sensor data) to be easily submerged by noise, resulting in extremely high bit error rates and severely affecting communication reliability. Fourth, there is the issue of addressing the size and power consumption redundancy of underwater robot communication hardware. Traditional solutions require bulky and complex heavy-duty isolation filters and coupling transformers to isolate strong electrical noise within the underwater pressure tank. This not only increases the weight of the underwater end but also occupies extremely valuable internal space and increases the number of penetrations in the sealed compartment, reducing the overall reliability of the system.

[0109] Compared to solutions that rely solely on broadband power line communication or traditional multi-core cable physical isolation, this invention has significant performance advantages and practical engineering value.

[0110] First, addressing the physical contradiction between balancing "high bandwidth" and "high real-time control" in a single-core cable environment, this invention introduces a power-to-signal transmission technology based on switching ripple, utilizing the inherent switching action of the dual active bridge converter directly as the signal carrier. Since control commands are embedded in the power switching sequence, they do not require encapsulation and queuing through complex network protocol stacks, significantly reducing downlink control latency from milliseconds to microseconds. This fundamentally ensures the real-time response accuracy and system stability of the tethered robot in dynamic interference environments.

[0111] Secondly, this invention solves the problem of suppressing weak communication signals by high-power transmission through a comprehensive strategy of "time-domain peak shifting" and "frequency-domain decoupling." Utilizing the proposed time-division duplex cooperation mechanism, the uplink signal sampling window is precisely aligned with the steady-state period of power switching operation. Combined with a highly efficient filtering network, this enables the system to extract clear feedback data from the "sea of ​​background" noise during high-power switching. This design approach of "transforming interference into a carrier" not only eliminates the heavy filters used in traditional solutions to suppress electromagnetic interference but also achieves zero packet loss in communication under multi-kilowatt high-power conditions, significantly improving the system's integration and lightweight design. Traditional research tends to view the ripple generated by power conversion as "harmful noise" that needs to be filtered out, while the communication field tends to avoid interference by avoiding power line environments. The uniqueness of this invention lies in breaking this mindset, transforming the physical characteristics of the power conversion process into communication resources. While there have been basic TPC attempts in the field before, they were mostly limited to low-speed data transmission and failed to foresee that a heterogeneous hybrid architecture of "uplink and downlink TPC (zero-level time + FSK) + PLC" could perfectly match the stringent requirements of tethered platforms for latency, bandwidth, and reliability. This interdisciplinary system-level integration and deep coupling with timing synchronization algorithms constitute the solution of this invention.

[0112] This invention is not only applicable to tethered underwater robots, but can also be widely used in high-altitude tethered unmanned aerial vehicle platforms, deep-earth drilling equipment, polar scientific detectors, and emergency rescue platforms in complex electromagnetic environments. Any scenario involving the simultaneous transmission of high-power electrical energy and exchange of multi-stream data (such as real-time control signals, multimedia video streams, and sensor feedback) through a single wire falls within the scope of this invention.

[0113] The above description provides a further detailed explanation of the present invention in conjunction with specific / preferred embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various substitutions or modifications can be made to these described embodiments without departing from the concept of the present invention, and all such substitutions or modifications should be considered within the scope of protection of the present invention. In the description of this specification, the reference to terms such as "an embodiment," "some embodiments," "preferred embodiment," "example," "specific example," or "some examples," etc., indicates that the specific features, structures, materials, or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. Without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications can be made herein without departing from the scope of protection of the patent application.

Claims

1. A method for hybrid transmission of power and multi-stream data based on an underwater robot tether, characterized in that, The underwater robot is connected to the main control center via a single-core cable tether. The method includes the following steps: S1. The single-core cable connects the mother control center and the underwater robot to achieve DC power transmission and time-division frequency-division hybrid duplex communication; S2. During downlink transmission, the parent control center uses the energy and signal transmission technology based on switching ripple to adjust the switching ripple characteristics of the converter online by modulating the switching action parameters of the power switch tube in the power converter, embedding the downlink control command into the switching ripple, and transmitting it to the underwater robot end through the single-core cable. S3. During uplink transmission, the uplink switching ripple characteristics are adjusted online by frequency shift keying modulation, and the sensor status data is injected into the single-core cable in another form of switching ripple and transmitted back to the mother control center. S4. An integrated high-speed broadband power line communication module is used to superimpose high-definition video streams onto the DC bus of the single-core cable via high-frequency carrier signals, and transmit them simultaneously with the time-division duplex uplink and downlink switching ripples. S5. The transmission timing of the downlink and uplink is coordinated by the time division duplex strategy, and the high-frequency power line communication signal and the intermediate frequency power conversion signal are isolated in the frequency domain by the frequency decoupling technology, so as to realize the coexistence of multi-stream data and bidirectional reliable communication.

2. The method according to claim 1, characterized in that, In step S2, the switching action parameters of the power switch in the power converter are modulated. Specifically, this includes: by fine-tuning the zero-level action time or phase shift angle of the bridge arm voltage in the power converter, the digital bits of the downlink control command are mapped to the waveform characteristics of the output voltage ripple. Different digital logics correspond to different zero-level time modulation amounts or phase shift angle offsets of the bridge arm voltages, and the modulation in step S2 does not change the output power.

3. The method according to claim 1, characterized in that, In step S3, the sensor status data modulated by frequency shift keying is injected into the single-core cable in another form of switching ripple through uplink simultaneous transmission. Specifically, the underwater robot end uses a power-driven converter to switch between at least two different preset carrier frequencies according to the sensor data bits to be transmitted back, generating a high-frequency signal pulse sequence in the frequency shift keying mode and injecting it into the single-core cable.

4. The method according to claim 1, characterized in that, Step S5 coordinates the transmission timing of the downlink and uplink using a time-division duplex strategy, specifically including: Each power switching cycle is divided into a downlink control window and an uplink detection window, wherein the downlink control window corresponds to the switching action period of the power switch tube, and the uplink detection window corresponds to the voltage stabilization period after the switching action ends; Within the downlink control window, the mother control center performs simultaneous transmission modulation based on switching ripple to send downlink commands; Within the uplink detection window, the mother control center activates the receiver to sample the feedback high-frequency signal pulses injected by the underwater robot.

5. The method according to claim 4, characterized in that, Step S5 also includes a noise suppression step for the uplink received signal: After the mother control center receiver samples the injected feedback high-frequency signal pulse, it applies a moving average filtering algorithm to process the sampled signal; the filtering window width of the moving average filtering algorithm is set to be synchronized with the power switching cycle. By integrating and averaging the sampled values ​​within a complete switching cycle, the periodic switching ripple is filtered out by utilizing the characteristic that the integral mean of the power switching noise within the complete cycle is zero, and a constant low-frequency feedback signal envelope is extracted; further, the moving average filtering algorithm specifically includes: keeping the sampling frequency synchronized with the power switching cycle, collecting a fixed number of sampling points within each power switching cycle; using each complete power switching cycle as the filtering window, calculating the arithmetic mean of all sampling points within the current window as the output value after filtering for that cycle; then sliding the filtering window sequentially to the next power switching cycle, repeating the above calculation process, thereby realizing cycle-by-cycle noise filtering and signal envelope extraction.

6. The method according to claim 1, characterized in that, In step S5, frequency decoupling technology is used to isolate the high-frequency power line communication signal from the intermediate-frequency power conversion signal in the frequency domain. Specifically, this includes configuring the operating frequency band of the power line communication module to be higher than the switching frequency and main harmonic frequency band of the power converter. At the receiving end of the mother control center, the high-frequency media signal is first filtered out by a hardware low-pass filter, and then the remaining high-frequency power line communication signal is further separated from the intermediate-frequency switching ripple signal by a high-low frequency splitter or a low-pass filter.

7. A hybrid power and multi-stream data transmission system based on an underwater robot tethering tether, characterized in that, include: The mother control center includes dual active bridge converters and control units; A single-core cable connects the mother control center to the underwater robot. The underwater robot end includes a power electronic converter, a power line communication module, energy storage, and load. The mother control center is configured to: transmit DC power to the underwater robot via a single-core cable through the dual active bridge converter; and use the power and signal transmission technology based on switching ripple to embed downlink control commands into the voltage ripple for transmission by modulating the operating parameters of the switching transistors in the dual active bridge converter. The underwater robot end is configured to: transmit sensor status data modulated by frequency shift keying in the form of switching ripple into a single-core cable via a battery or power drive converter; and transmit high-definition video streams superimposed on the single-core cable in the form of high-frequency carrier waves via the power line communication module. The system is also configured to coordinate downlink and uplink transmission timing through a time-division duplex strategy, and to isolate high-frequency power line communication signals from intermediate-frequency power conversion signals through frequency decoupling.

8. The system according to claim 7, characterized in that, The mother control center maps the digital bits of the downlink control command to the waveform distortion characteristics of the output voltage ripple by fine-tuning the zero-level time or phase shift angle of the bridge arm voltage of the dual active bridge converter. Different digital logics correspond to different zero-level time modulation amounts or phase shift angle offsets of the bridge arm voltages, and this fine-tuning does not change the power transmission.

9. The system according to claim 7, characterized in that, The transducer at the underwater robot end is configured to switch between at least two different preset carrier frequencies based on the sensor data bits to be transmitted back, generate a switching ripple pulse sequence using frequency shift keying, and inject it into a single-core cable. The mother control center also includes a receiver configured to sample the injected high-frequency signal pulses and apply a moving average filtering algorithm to filter out periodic switching noise. The filtering window width of the moving average filtering algorithm is set to be synchronized with the power switching cycle. By integrating and averaging the sampled values ​​within a complete switching cycle, the algorithm utilizes the characteristic that the integral mean of the power switching noise is zero within the complete cycle to filter out periodic switching ripple and extract a constant low-frequency feedback signal envelope.

10. The system according to claim 7, characterized in that, The time-division duplex strategy specifically includes: the dual active bridge converters and the battery-side Buck circuit half-bridge topology converters alternately transmit information in different time slots, and maintain a preset time interval between time slots; in time slots other than the working time slot of the converter, each converter only maintains normal power transmission function and does not modulate information. When it is their turn to work in their time slot, the corresponding converter begins to embed information into the modulation degree of freedom.

11. The system according to claim 10, characterized in that, The dual active bridge converter maintains normal dual-phase-shift power transmission during non-communication time slots and changes the zero-level time modulation information during communication time slots. The battery-side converter maintains single-frequency power transmission during non-communication time slots and switches between two different frequencies during communication time slots.

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