Shaft power monitoring system based on wireless power supply and micro strain measurement

Abstract

A shaft power monitoring system based on wireless power supply and micro-strain measurement comprises a rotor, a stator, a wireless power supply system and a display end, the rotor part collects shafting strain signals through a strain gauge, and after signal conditioning and digital processing are completed through a microcontroller, non-contact transmission of data is achieved through a wireless transmitting module; meanwhile, electric energy required by operation is obtained through a wireless power supply receiving end and a rectifying circuit board; the stator part receives and analyzes data transmitted by the rotor through a wireless receiving module, and signal management and state monitoring are carried out by a microcontroller; meanwhile, a rotating speed measuring module arranged in the stator monitors the rotating speed of the shaft system in real time, and continuous and stable energy support is provided for the rotor through a direct-current power supply and a wireless power supply transmitting end. According to the invention, through combination of a high-precision micro-strain measurement technology, wireless power supply and wireless data transmission, technical difficulties of a traditional shaft power measurement system can be effectively solved.

Description

Technical Field

[0001] This invention relates to the field of industrial equipment monitoring technology, and in particular to a shaft power monitoring system based on wireless power supply and micro-strain measurement. Background Technology

[0002] Traditional shaft power measurement systems primarily measure torque and speed. A few systems can measure axial force, but these are mostly indirect calculations with low accuracy. Furthermore, limitations in power supply and signal transmission methods make it difficult to achieve long-term, stable data acquisition and transmission at the rotor end, especially in acquiring minute strain signals generated in bearings, thrust discs, and other components, presenting significant technical challenges.

[0003] 1. Traditional shaft thrust cannot be directly measured:

[0004] Traditional shaft thrust measurement methods often rely on force sensors or large-scale calculations, which have low accuracy and cannot directly and accurately measure minute thrust changes on the shaft. Especially in high-precision application scenarios, they often cannot meet the requirements for real-time and accurate monitoring.

[0005] 2. Difficulty in obtaining high-precision micro-strain signals:

[0006] In high-energy components such as rotors and thrust disks, minute strain signals are often difficult to capture. Existing strain gauge systems have significant limitations in terms of accuracy and stability, and the strain signals are greatly affected by external environmental interference, leading to large data errors.

[0007] 3. The measurement system is integrable:

[0008] Traditional shaft torque and power measurement equipment is usually a standalone device that can only work independently and cannot be integrated into external systems, thus failing to provide effective data support for external system decision-making. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a shaft power monitoring system based on wireless power supply and micro-strain measurement. By combining high-precision micro-strain measurement technology, wireless power supply and wireless data transmission, the technical difficulties of traditional shaft power measurement systems can be effectively solved.

[0010] The technical problem to be solved by this invention is achieved through the following technical solution. This invention is a shaft power monitoring system based on wireless power supply and micro-strain measurement, comprising a rotor, a stator, a wireless power supply system, and a display terminal.

[0011] The rotor section uses strain gauges to collect shaft strain signals. After the microcontroller completes signal conditioning and digital processing, the data is transmitted non-contactly through a wireless transmission module. At the same time, the power required for operation is obtained through a wireless power supply receiver and a rectifier circuit board.

[0012] The stator receives and parses the data transmitted by the rotor through a wireless receiving module, and the microcontroller manages the signal and monitors the status. At the same time, the stator's built-in speed measurement module monitors the shaft speed in real time and provides continuous and stable energy support to the rotor through a DC power supply and a wireless power supply transmitter.

[0013] The wireless power supply system takes the electromagnetic induction coupling between the stator and rotor coils as its core, establishes an efficient power transmission channel from the stator to the rotor, and provides long-term power supply for rotating parts.

[0014] The display terminal transmits data via a 485 communication interface, visually displays key parameters in real time on the matching display screen, and uploads the data to the host computer for centralized monitoring, historical analysis, and command interaction.

[0015] The technical problem to be solved by the present invention can also be further achieved through the following technical solution: For the shaft power monitoring system based on wireless power supply and micro-strain measurement described above, the shear strain of the shaft under test is measured by strain gauges, the torque signal is wirelessly transmitted and received by a telemetry torque meter, and finally the shaft torque signal is acquired by a data acquisition card. During installation, the signal transmitter is fixed on the shaft and rotated with the shaft to generate a torque signal. The torque signal is connected to the transmitter via a wire, the transmitter outputs the torque signal, the receiver receives the torque signal, and then it is transmitted to a computer for effective data analysis and processing to obtain the shaft power.

[0016] The technical problem to be solved by this invention can also be further achieved through the following technical solution: For the shaft power monitoring system based on wireless power supply and micro-strain measurement described above, the torque measurement method in this system is as follows:

[0017] When a torque of magnitude T is applied to a shaft of length L, the shaft system will deform. Any two shaft cross sections rotate relative to each other around the central axis, resulting in a torsional angle. The shear stress at point C, a distance r from the center of the shaft cross section, is:

[0018]

[0019] Where: τ - shear stress at point C of the axial section;

[0020] The distance from point rC to the center of the circle;

[0021] I p - Polar moment of inertia of the axial section about the center of the circle;

[0022] For a hollow circular shaft, the polar moment of inertia I p :

[0023]

[0024] In the formula: d i - The inner diameter of the shaft;

[0025] d0 - outer diameter of the shaft;

[0026] The maximum shear stress occurs on the outer surface of the shaft:

[0027]

[0028] In the formula: τ max - Maximum shear stress on the shaft;

[0029] The angle of twist θ per unit length of the shaft is:

[0030]

[0031] Where: G - shear modulus of the material;

[0032] The shear modulus G of the material is:

[0033]

[0034] Where: E - the elastic modulus of the material;

[0035] μ-Poisson's ratio;

[0036] According to mechanics of materials, the maximum shear strain γ on the surface of an elastic shaft is:

[0037]

[0038] Based on formula (6), the following formula can be derived:

[0039]

[0040] As can be seen from equation (6), the torque T can be calculated by directly measuring the torsion angle.

[0041] The technical problem to be solved by this invention can also be further achieved through the following technical solution: For the shaft power monitoring system based on wireless power supply and micro-strain measurement described above, when using strain gauge torque measurement to measure shaft power, the actual ship mainly uses a combination of strain gauges and telemetry torque meters. First, four strain gauges are attached along the ±45° direction of the given shaft to form a full-bridge circuit. Then, the strain is converted into a voltage value using a telemetry torque meter. Finally, the torque is calculated using the output voltage value. Specifically:

[0042] The strain gauge has a resistance of R. The strain ε will cause a change in the resistance of the strain gauge ΔR. According to the strain effect, the sensitivity coefficient of the strain gauge is defined as follows:

[0043]

[0044] In the formula: k GF -Sensitivity coefficient of the strain gauge;

[0045] In a Wheatstone bridge circuit, the bridge output voltage V out It has a certain proportional relationship with the strain ε, assuming the excitation voltage of the bridge is V. EXC Through derivation, we can obtain:

[0046]

[0047] In the formula: V out - Output voltage (V) of the torque meter;

[0048] V EXC - Excitation voltage (V) of the bridge circuit.

[0049] The technical problem to be solved by this invention can also be further achieved through the following technical solution: For the shaft power monitoring system based on wireless power supply and micro-strain measurement described above, the rotational speed measurement method in this system is as follows:

[0050] First, a magnet is mounted on the shaft. The shaft speed is determined by the pulse signal intervals generated by a Hall sensor. When the shaft rotates, the magnet passes the probe in front of the sensor, which generates a pulse. This pulse signal is transmitted to a counter for counting. Finally, the measured speed signals are averaged to obtain the shaft speed. The shaft speed can be calculated using the following formula:

[0051]

[0052] In the formula: ΔT - the interval between two pulses.

[0053] The technical problem to be solved by this invention can also be further achieved through the following technical solution: For the shaft power monitoring system based on wireless power supply and micro-strain measurement described above, the method for calculating shaft power in this system is as follows:

[0054] The shaft power of a ship's shafting system is measured indirectly by measuring the output torque and speed of the shafting system. Specifically, the torque and speed are measured separately, and then the shaft power is calculated. The formula is as follows:

[0055]

[0056] Where: P - shaft power of the shaft system (kW);

[0057] Output torque of the T-axis system (N·m);

[0058] n - Output shaft speed (r / min).

[0059] The technical problem to be solved by this invention can also be further achieved through the following technical solution: For the shaft power monitoring system based on wireless power supply and micro-strain measurement described above, the system is installed using mounting components, which include a column, a machine-side control box, a wireless power supply transmitter mounting component, a wireless power supply receiver mounting component, and a rotor module mounting component.

[0060] The column adopts a welded rectangular steel pipe structure, with adjustable anchor bolts at the bottom and a flange connection plate at the top of the column to enable fine adjustment of the transmitter's angle and position, ensuring the spatial alignment accuracy of the power supply system.

[0061] The local control box serves as the core control and signal processing unit, performing data acquisition, signal conditioning, wireless power supply control, and communication interface management. The local control box has a metal enclosure structure and adopts a front-opening design. The local control box is equipped with standard guide rails for modular installation of power supply, data acquisition board, and communication module. The local control box is fixed to the lower part of the column by flanges or clamps. The cable is introduced into the box through a waterproof connector. Reliable grounding terminals are set inside and outside the local control box. Critical signal lines are connected with shielded twisted pair cables, and the shielding layer is grounded to the box.

[0062] The wireless power supply transmitter mounting assembly is responsible for providing energy coupling to the receiver on the rotor, enabling non-contact power supply to the on-axis measurement system. The wireless power supply transmitter mounting assembly includes a transmitting coil and a support frame. The transmitting coil and the support frame are configured as a coaxial adjustable structure that can be finely adjusted in the radial and axial directions. The support frame is made of aluminum alloy or stainless steel and is equipped with a precision fine-tuning slide mechanism, which is fixed by locking screws. A protective cover is set around the transmitting coil, and the power supply cable is introduced through the inside of the column.

[0063] The wireless power supply receiver mounting assembly is fixed on the rotating shaft and forms a magnetic coupling circuit with the transmitter. It is used to receive the energy transmitted wirelessly and power the rotor acquisition module. The wireless power supply receiver mounting assembly includes a split clamp-type receiving coil. Its housing material is made of aluminum alloy or high-strength engineering plastic. The inside is filled with shockproof and moisture-proof material, and the outside is equipped with a protective cover.

[0064] The rotor module mounting assembly is used to fix the torque, speed, and signal acquisition modules of the shaft power meter and transmit signals wirelessly to the stationary end. The assembly includes a sensor clamping ring, a signal conditioning board bracket, and a protective cover. The sensor clamping ring integrates a strain gauge torque sensor and a speed sensor to achieve high-precision measurement of the rotating shaft. The signal conditioning board bracket supports the circuit module and provides a heat dissipation channel. The protective cover encapsulates the entire module to prevent mechanical damage, dust, and electromagnetic interference.

[0065] The technical problem to be solved by the present invention can also be further achieved through the following technical solution: For the shaft power monitoring system based on wireless power supply and micro-strain measurement described above, the receiving coil is installed using a lightweight clamping ring structure with an inner hole tolerance grade of H7, and the radial runout after tightening does not exceed 0.02mm.

[0066] When installing the rotor module mounting assembly, the coaxiality error between it and the shaft being measured must not exceed 0.03mm. It should be fixed with an interference fit or locating pins to prevent rotational slippage. All rotating parts must be dynamically balanced to achieve a balance level of G2.5.

[0067] The technical problem to be solved by this invention can also be further achieved through the following technical solution: For the shaft power monitoring system based on wireless power supply and micro-strain measurement described above, an anti-interference method is also designed in this system, specifically as follows:

[0068] Employs multi-channel parallel synchronous sampling technology, with each channel equipped with an independent A / D converter;

[0069] Interference is suppressed by employing multi-layer shielding and advanced isolation techniques, including constructing a complete shield using good conductors and ensuring proper grounding to suppress electric field interference; utilizing the low magnetic reluctance characteristics of high-permeability materials to shunt the magnetic field, and using differential input at the input end to suppress magnetic field interference; using tinplate to absorb and reflect electromagnetic waves to suppress electromagnetic field interference; and suppressing the common-mode voltage of conducted interference through isolation and differential amplifiers, thus achieving common-mode suppression.

[0070] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0071] 1. High-precision thrust measurement:

[0072] This invention uses a full-bridge strain gauge and a high-precision AD sampling chip to accurately capture minute strain changes in components such as rotor bearings and thrust disks. Combined with a data smoothing algorithm, it derives high-precision axial thrust, solving the measurement error and instability problems of traditional methods. Compared with traditional force sensor or strain gauge measurement methods, this invention can provide more stable and accurate axial thrust data.

[0073] 2. Non-contact wireless power supply:

[0074] This invention uses magnetically coupled resonant wireless power supply, which solves the problem of rotor unit power supply and avoids the problem of not being able to monitor for a long time caused by traditional battery power supply.

[0075] 3. System intelligence and integration:

[0076] This invention not only has high-precision measurement capabilities, but also provides real-time feedback of monitoring data and integrates with external energy efficiency management systems. Through intelligent data processing and analysis, the system can provide early warnings and optimizations based on data trends, helping users to take timely maintenance measures, reduce equipment failure rates, and provide users with more decision support by integrating with energy efficiency management systems, thereby improving the overall management level of industrial equipment.

[0077] 4. Cost optimization:

[0078] This invention adopts a modular design, including stator unit, rotor unit, power supply unit, etc., which can be flexibly configured and expanded according to different needs. Compared with traditional equipment and measurement methods, this system has lower cost and stronger scalability. Attached Figure Description

[0079] Figure 1 This is a system diagram of the present invention; Figure 2 This is a schematic diagram of the torque measurement principle of the present invention; Figure 3 This is a schematic diagram of the full-bridge resistance strain gauge of the present invention; Figure 4 This is a general block diagram of the present invention; Figure 5 This is the homepage interface of the display terminal of the present invention; Figure 6 This is the average interface of the display terminal of the present invention; Figure 7 This is the trend interface of the display terminal of the present invention. Detailed Implementation

[0080] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0081] A shaft power monitoring system based on wireless power supply and micro-strain measurement is specifically designed as follows:

[0082] 1. Requirements Analysis and Overall Requirements

[0083] 1.1 Functional Requirements Analysis

[0084] 1.1.1 Core Measurement and Calculation

[0085] Torque, speed, and shaft power are measured and coupled online in real time. Power calculation uses P = 2πnT / 60, and supports output of instantaneous value, moving average, and statistical value (mean / peak / standard deviation).

[0086] Speed: Continuous and stable measurement from low-speed start / parking (<10rpm) to high-speed cruising (thousands of rpm), with no pulse loss or frequency doubling misjudgment; supports adaptive frequency / cycle measurement and self-recovery from code loss.

[0087] Power and shaft diameter range: Standard configuration covers 0–5MW with a typical shaft diameter of 120mm; universal adaptation to higher power and different shaft diameters is achieved through interchangeable bushings, sensing and power supply components.

[0088] 1.1.2 Data and Human-Computer Interaction

[0089] (1) Real-time visualization: torque / speed / power curves, operating condition labels, alarm status;

[0090] (2) Data management: local cyclic storage (≥12 months), historical query, report export (CSV / Excel / PDF);

[0091] (3) Remote monitoring: Ethernet remote access, access control, and log traceability;

[0092] (4) Time synchronization: NTP / local PTP (optional) time synchronization, timestamp accuracy ≤10ms.

[0093] 1.1.3 System and Maintenance

[0094] (1) Self-diagnosis and health monitoring: open or short circuit of sensor bridge, excessive temperature, insufficient power supply, link quality, abnormal speed, and data consistency verification;

[0095] (2) Calibration and calibration: Supports factory calibration and on-site zero-point calibration; provides a one-click calibration wizard;

[0096] (3) Security and permissions: Role / permission hierarchy, auditing and signature of critical operations;

[0097] (4) Engineering deployment: No machining of the shaft is required. Clamping / clamping type installation supports quick disassembly and recalibration.

[0098] 1.2 Performance Indicators and Overall Environmental Requirements

[0099] 1.2.1 Performance Indicators

[0100] Table 1 Performance Indicators

[0101]

[0102]

[0103] 1.2.2 Power Supply and Energy Efficiency

[0104] On-axis wireless power supply: Rated available power 5–10W (depending on configuration), power supply coupling efficiency optimized ≥50% (assembly conditions); power failure restart ≤5s;

[0105] Power supply: 220VAC or 24VDC (18–36V) / 50W, overvoltage / undervoltage / reverse connection protection.

[0106] 1.2.3 Environmental adaptability

[0107] Temperature: -10 to +55℃; Relative humidity: 5–95% (non-condensing);

[0108] Vibration / shock resistance: meets the requirements of long-term vibration and occasional shock conditions of ships (frequency sweep 5–500Hz, displacement / acceleration according to ship equipment level);

[0109] Protection and corrosion resistance: IP65 for shaft and deck connection components (IP67 optional); salt spray resistance for critical metal parts ≥96h; anti-mildew and anti-condensation design;

[0110] Electromagnetic compatibility (EMC): It has design margins for electrostatic discharge (contact / air discharge), conducted / radiated disturbances and immunity, and key interfaces adopt common mode suppression and 360° shielding of the housing.

[0111] 1.2.4 Safety and Electrical Isolation

[0112] Electrical isolation: The on-axis / off-axis data link and power supply isolation withstand voltage meets type test requirements; the equipotential / isolation strategy between the enclosure and electrical circuits is clear;

[0113] Failure safety: When critical sensors or links fail, the system enters a safety degradation mode, maintaining data logging and alarm notifications without affecting the host control chain.

[0114] 1.3 Interface and System Compatibility

[0115] System Interface and Data: Supports RS-485 serial bus (Modbus / RTU); real-time streams and historical files use CSV / JSON, with records including timestamps, operating condition tags, and calibration version numbers. Hardware Interface and Installation: The sensor / speed measurement module supports interchangeable magnetoelectric / photoelectric / Hall effect standards; target discs / encoding marks can be customized according to shaft diameter; cable shielding with 360° housing; controlled coupling between signal ground and housing ground to meet withstand voltage and EMC specifications; assembly windows (concentricity, clearance, and coupling alignment) are provided for installation tolerances, with a target installation time of ≤4 hours per installation. Platform Compatibility and Integration: The system interfaces with ship monitoring / energy efficiency (EEM) systems via standard protocols and supports access from third-party data acquisition devices and data lakes. Testing, Acceptance, and Documentation: The laboratory conducts static torque calibration, linearity and repeatability testing, temperature drift testing, low / high speed coverage testing, link reliability testing, and EMC pre-testing; on-site (onboard) testing is conducted for full speed / multi-load conditions, ≥500 hours of long-term continuous operation, vibration and salt spray adaptability verification; acceptance is based on key accuracy indicators meeting standards, packet loss rate and restart recovery, time synchronization and alarm function compliance, and data integrity and traceability; delivery includes an instruction manual, installation and assembly manual, calibration and maintenance manual, communication protocol and checklist, certificate of conformity and type test report (copies), and a list of spare parts and consumables (BOM).

[0116] Constraints and boundary conditions: This system does not change the host control logic and only serves as an independent monitoring and data service; the solution prioritizes autonomy and maintainability, and any purchased components must have long-term supply and alternative paths.

[0117] 2 Measurement Principle

[0118] Currently, based on different measurement principles, the measurement of shaft power in ship shafting systems is mainly divided into two methods: phase difference method and strain method.

[0119] Phase difference methods utilize torque sensors to measure the torsional angles of different shaft sections under external forces; commonly used instruments include steel wire sensors and laser sensors. Strain gauge methods, on the other hand, use strain gauges to determine the principal stresses generated by torsion in the shaft system; strain gauges are commonly used instruments. Regarding the transmission of measurement data from the rotating shaft system to the measuring instrument, there are two methods: contact and telemetry. Contact methods rely on current collectors for data transmission, while telemetry uses wireless transmission.

[0120] A comprehensive comparison reveals that the steel-string shaft power tester is relatively bulky, cumbersome to install, and its measurement results are easily affected by environmental factors. In contrast, the telemetry-based strain gauge shaft power tester, due to its simple structure, compact size, and convenient operation, is suitable for measuring shaft power of various shaft diameters and is widely used in actual ship shaft power measurement and data analysis. Therefore, this research will focus on the development of a telemetry-based strain gauge shaft power tester.

[0121] 2.1 Strain Gauge Shaft Power Measurement System

[0122] The strain gauge shaft power measurement system consists of strain gauges, a telemetry torque meter, a speed sensor, a magnet, a data acquisition card, and a computer, etc. Figure 1 The strain gauge shaft power system diagram is shown.

[0123] In this system, strain gauges are used to measure the shear strain of the shaft under test. A telemetry torque meter is used for wireless transmission and reception of torque signals. Finally, a data acquisition card is used to collect the shaft torque signals. During installation, the signal transmitter is typically fixed to the shaft and rotates with it to generate a torque signal. The torque signal is connected to the transmitter via a wire, output by the transmitter, received by the receiver, and then transmitted to a computer for effective data analysis and processing to determine the shaft power.

[0124] 2.2 Shaft Power Measurement Principle

[0125] 2.2.1 Torque Measurement Principle

[0126] When a torque of magnitude T is applied to a shaft of length L, the shaft system will deform, and any two shaft cross sections will rotate relative to each other around the central axis, resulting in a torsional angle (e.g., ...). Figure 2 (As shown). Then the shear stress at point C, a distance r from the center of the circle on the cross-section of the shaft, is:

[0127]

[0128] Where: τ - shear stress at point C of the axial section;

[0129] The distance from point rC to the center of the circle;

[0130] I p - Polar moment of inertia of the axial section about the center of the circle.

[0131] For a hollow circular shaft, the polar moment of inertia I p :

[0132]

[0133] In the formula: d i - The inner diameter of the shaft;

[0134] d0 - outer diameter of the shaft.

[0135] The maximum shear stress occurs on the outer surface of the shaft:

[0136]

[0137] In the formula: τ max - Maximum shear stress on the shaft;

[0138] The angle of twist θ per unit length of the shaft is:

[0139]

[0140] Where: G is the shear modulus of the material.

[0141] The shear modulus G of the material is:

[0142]

[0143] Where: E - the elastic modulus of the material;

[0144] μ-Poisson's ratio.

[0145] According to mechanics of materials, the maximum shear strain γ on the surface of an elastic shaft is:

[0146]

[0147] Based on formula (6), the following formula can be derived:

[0148]

[0149] As can be seen from equation (6), the torque T can be calculated by directly measuring the torsional angle. This method is called the phase-type torque measurement method. As can be seen from equation (7), the magnitude of the torque can be obtained by measuring the shear strain γ on the shaft. This is the principle of the strain gauge torque measuring instrument.

[0150] When using strain gauge torque measurement to measure shaft power, the actual shipboard primarily uses a combination of strain gauges and telemetry torque meters. First, four strain gauges are attached along the ±45° direction of the given axis, forming a full-bridge circuit (e.g., ...). Figure 3 As shown in the diagram, the strain is then converted into a voltage value using a telemetry torque meter, and finally the torque is calculated using the output voltage value. The full-bridge circuit provides both temperature compensation and improved output sensitivity, thereby reducing the impact of external environmental changes on the strain gauge resistance.

[0151] The strain gauge has a resistance of R, and the strain ε will cause a change in the strain gauge's resistance ΔR. Based on the strain effect, the strain gauge sensitivity coefficient is defined as follows:

[0152]

[0153] In the formula: k GF -Sensitivity coefficient of the strain gauge;

[0154] In a Wheatstone bridge circuit, the bridge output voltage V out It has a certain proportional relationship with the strain ε. Assume the bridge excitation voltage is V. EXCThrough derivation (based on conditions such as bridge balancing and strain gauge bonding method), we can obtain:

[0155]

[0156] In the formula: V out - Output voltage (V) of the torque meter;

[0157] V EXC - Excitation voltage (V) of the bridge;

[0158] 2.2.2 Rotational Speed ​​Measurement Principle

[0159] Rotational speed is measured using a Hall effect sensor. First, a magnet is mounted on the shaft. The rotational speed is determined by the pulse signal intervals generated by the Hall effect sensor. As the shaft rotates, the magnet passes the probe in front of the sensor, generating a pulse. This pulse signal is transmitted to a counter for counting. Finally, the measured rotational speed signals are averaged to obtain the shaft's rotational speed. The shaft's rotational speed can be calculated using the following formula:

[0160]

[0161] In the formula: ΔT - the interval between two pulses.

[0162] Hall effect sensors have advantages such as simple structure, fast response, strong anti-interference ability, and digital output signal, making them particularly suitable for long-term stable operation in complex electromagnetic environments such as ship engine rooms.

[0163] 2.2.3 Power Calculation Principle

[0164] Currently, the shaft power of a ship's shafting system is measured indirectly by measuring the output torque and rotational speed of the shafting system. That is, the torque and rotational speed are measured separately, and then the shaft power is calculated. The calculation formula is as follows:

[0165]

[0166] Where: P - shaft power of the shaft system (kW);

[0167] Output torque of the T-axis system (N·m);

[0168] n - Output shaft speed (r / min).

[0169] Therefore, the key to measuring shaft power lies in achieving accurate measurement of torque and rotational speed. Shaft rotational speed is a physical quantity that reflects the speed of rotation of the shaft, and shaft rotational speed measurement technology is already very mature, with measurement accuracy easily meeting requirements.

[0170] 3 Overall Functional Design

[0171] This system comprises a rotor, stator, wireless power supply system, and display terminal, integrating data acquisition, wireless energy transmission, and information display. The rotor utilizes strain gauges to collect shaft strain signals. After signal conditioning and digitization by a microcontroller, the data is transmitted non-contactly via a wireless transmitter module. Simultaneously, the system obtains the necessary power through a wireless power supply receiver and rectifier circuit board. The stator receives and analyzes the data transmitted by the rotor via a wireless receiver module. The microcontroller manages the signals and monitors the status. Meanwhile, the stator's built-in speed measurement module monitors the shaft speed in real time and provides continuous and stable power support to the rotor via a DC power supply and the wireless power supply transmitter. The wireless power supply system, based on the electromagnetic induction coupling between the stator and rotor coils, establishes an efficient power transmission channel from the stator to the rotor, effectively solving the problem of long-term power supply difficulties for rotating components. The display terminal uses a 485 communication interface for data transmission, allowing real-time visualization of key parameters such as strain and speed on the display screen. Data can also be uploaded to a host computer for centralized monitoring, historical analysis, and command interaction. This system forms a comprehensive measurement and management solution that integrates rotor condition monitoring, wireless power supply, data transmission, and multi-terminal display, providing technical support for the intelligent and engineering application of shaft power meters.

[0172] 3.1 Rotor Measurement Module

[0173] The rotor measurement module is the core component of the shaft power meter. It is used to collect key parameters such as shaft torque and speed in real time while the shaft is rotating, providing accurate data for power calculation and performance analysis.

[0174] 3.1.1 Measurement Parameter Settings

[0175] (1) Sampling configuration: Supports dynamic setting of sampling frequency through interface / configuration items, covering the industrial standard range (e.g., 10Hz to 1kHz).

[0176] (2) Data processing: Ensure the stability of the sampling process (packet loss rate <0.1%) and data accuracy (error ≤ ±0.5%); automatically convert to the system's unified data format, and support local caching (at least 10,000 records) and real-time push (MQTT / HTTP) dual modes.

[0177] (3) Status monitoring: Real-time feedback of sampling status (normal / abnormal) and key indicators (frequency deviation rate, number of packet loss); abnormal thresholds are configurable (such as frequency fluctuation exceeding ±5%, continuous packet loss ≥3 times), triggering multi-level alarms (log recording + API callback).

[0178] 3.1.2 Average processing

[0179] (1) Second-level average calculation: Based on real-time sampled data from the rotor end, the average torque value is automatically calculated by aggregating data second by second (default arithmetic mean), ensuring that the calculation error is ≤ ±0.1%. For the torque acquisition channel, it is generally recommended to set the data sampling frequency to 1000Hz, i.e., k = 1000Hz, then the average value of the acquired voltage V per second is... out_1s_ave The calculation formula is:

[0180]

[0181] (2) Data standardization: The calculation results are uniformly converted into the system standard format.

[0182] (3) Anomaly handling strategy: Automatically detect missing data (insufficient sampling points to the threshold) or outliers (exceeding the 3σ range); support configuration of replacement strategies (previous value replacement / linear interpolation / empty), with the default being the 3-second moving average; anomaly records include timestamps, anomaly types, and original data snapshots, and support real-time API queries.

[0183] 3.1.32.4G wireless data transmission

[0184] (1) Wireless communication: 2.4G wireless technology is used to realize data transmission between the rotor end and the stator end; the transmission distance is ≥10 meters and can penetrate 1-2 walls; the signal is stable and not easily interfered with.

[0185] (2) Data transmission: accurately and completely transmits the torque data collected at the rotor end to the stator end; the transmission delay is small to ensure the real-time performance of the data; and it has a data verification mechanism to avoid data errors.

[0186] (3) Reliability assurance: Automatic retransmission mechanism to ensure data transmission success rate; low power consumption design to extend device usage time.

[0187] (4) Development interface: Provides a simple and easy-to-use configuration interface for easy setting of transmission parameters; supports remote monitoring and management.

[0188] 3.2 Stator Control Module

[0189] The stator control module is responsible for receiving and processing rotor measurement data, realizing comprehensive control and management of data calculation, display, and system operation.

[0190] 3.2.1 Calculating Torque

[0191] Torque average per second T 1s_ave The calculation formula is:

[0192]

[0193] In the formula: T ONEQ - Voltage and torque calculation coefficients;

[0194] K Q - Torque sign and calibration coefficient.

[0195] 3.2.2 Rotational speed acquisition and calculation

[0196] (1) Hardware adaptation: A Hall element speed sensor is selected to complete the adaptation connection with the stator end, ensuring that the signal is stably transmitted to the main control unit.

[0197] (2) Signal acquisition: Set the counter according to the configurable parameters, acquire the output pulse signal of the Hall element, and adapt to different speed conditions.

[0198] (3) Rotational speed calculation: Based on the acquired pulses, the real-time stator rotational speed is calculated using a precise algorithm, with an accuracy of ±0.1 r / min. The result is stored and transmitted according to the specified format. The average rotational speed per second, n, is acquired. 1s_ave The calculation formula is as follows:

[0199]

[0200] In the formula: r - the acquired rotational speed pulse signal, in Hz;

[0201] The f-axis rotational speed sampling frequency is usually set to Hz.

[0202] (4) Abnormal handling: Monitor sensor signals, trigger alarms and record information when abnormalities occur, to facilitate troubleshooting.

[0203] 3.2.3 Calculate shaft power

[0204] (1) Data acquisition: The system acquires real-time speed data and torque data from the rotor end, etc., to ensure the real-time performance and accuracy of data acquisition.

[0205] (2) Application of calculation formula: Based on the classic shaft power calculation formula, see the power calculation principle for details, and accurately calculate the average power per second.

[0206] (3) Calculation result processing: The calculated shaft power results must be stored in accordance with the data format specified by the system, and support data storage for at least 180 days for subsequent query and analysis.

[0207] (4) Abnormal handling: If data is missing or abnormal values ​​(such as speed or torque exceeding the reasonable range) occur during data acquisition or calculation, the system should be able to detect and trigger the corresponding error prompts or alarm mechanisms in a timely manner, and record the relevant abnormal information to facilitate subsequent troubleshooting and repair.

[0208] 3.2.4 Calculate power within a specific time period

[0209] (1) Data preparation: It can automatically acquire real-time power data generated by the shaft power calculation module (such as the shaft power data calculated in 2.3.2) to ensure the integrity and accuracy of the data.

[0210] (2) Duration setting and calculation: Provides users with the function of setting specific durations (such as input through the interface or API); the duration setting is divided into absolute duration and relative duration.

[0211] (2.1) Absolute duration: The duration ranges from 1 minute to infinity. Based on the set duration, the system automatically filters the power data within the corresponding time period and calculates the average power using the arithmetic mean.

[0212] (2.2) Relative duration: Based on the current time, set the relative duration to trace back, with a duration range of 1 minute to 24 hours. The system automatically filters the power data within the corresponding time period from the current moment according to the set relative duration, displays the trend, and calculates the average power using the arithmetic mean.

[0213] (3) Output of results: The calculated average power over a specific time period must be stored in the system's standard data format, supporting local storage and remote database storage.

[0214] (4) Anomaly Handling: If data loss or errors occur during the data acquisition stage, or if anomalies occur during the calculation process due to unreasonable time settings, the system should issue an alarm in a timely manner, record the anomaly information (including the anomaly time, type, related data, etc.), and take reasonable remedial measures (such as using data from a nearby time period for estimation, etc.).

[0215] 3.2.5 Initiate to display terminal

[0216] (1) Data integration and preprocessing: Collect parameter data such as torque, speed, and average power over a specific time, detect and mark outliers, and configure anomaly handling strategies (default linear interpolation).

[0217] (2) Communication protocol configuration: The touch screen and the stator module communicate via RS485 using Modbus RTU protocol, with the touch screen configured as the master station. It features a reconnection function after disconnection.

[0218] (3) Real-time data push: The communication cycle (interval) is 100-2000m, usually set to 500ms.

[0219] (4) Status monitoring and alarm: Real-time display of link RTT, throughput, packet loss rate and other indicators, abnormal level alarm (warning, error, critical), storage of ≥10,000 historical alarm records, and conditional search.

[0220] 3.3 Wireless Power Supply Module

[0221] This system aims to provide a stable and continuous power supply to the rotating components (rotor end) of the shaft power meter to meet the power requirements of modules such as sensing, signal processing, and wireless data transmission. Traditional slip-ring power supply methods suffer from wear, short lifespan, and severe signal interference, making them unsuitable for the long-term, high-precision operation requirements of deep-sea equipment and high-end vessels. Therefore, this project employs Wireless Power Transfer (WPT) technology based on the principle of electromagnetic induction coupling to construct a non-contact power supply system between the stator and rotor, achieving efficient and reliable energy transfer during rotation.

[0222] The system consists of a stator power supply terminal, a rotor receiver terminal, a rectification and voltage regulation module, an energy storage unit, and a power management circuit. The stator coils transmit energy to the rotor coils through a high-frequency resonant circuit. After rectification and voltage regulation on the rotor side, the energy powers the front-end signal conditioning module, analog-to-digital converter (ADC), microcontroller unit (MCU), and 2.4GHz wireless data transmission module, realizing an overall solution of "energy-data dual wireless channels".

[0223] 3.3.1 Topology and Operating Frequency

[0224] The system adopts a stator-rotor electromagnetic coupling coil structure. Depending on the installation space, coil size and axial structure, a series-to-series (S / S) or series-to-parallel (S / P) resonant compensation topology is selected.

[0225] (1) Series-to-series structure is suitable for applications with high coupling coefficients and can achieve higher efficiency;

[0226] (2) Series-parallel structures exhibit better voltage stability when coupling changes are large.

[0227] The operating frequency range is designed to be 100–300kHz, with the specific frequency optimized based on the permeability, loss characteristics, and Q value of the core material. To balance high efficiency and low heat loss, the core uses low-loss MnZn ferrite material, and the coil geometry and gap arrangement are optimized through finite element simulation (ANSYS Maxwell / COMSOL).

[0228] The rotor is equipped with a rectifier and voltage regulator module, connected in parallel with a large-capacity energy storage capacitor (≥10–47mF). The energy storage unit is used to cope with transient conditions such as short-term coupling interruptions and startup fluctuations, ensuring that the system has a power loss endurance capability of **≥ several seconds**. The system startup response time is controlled within ≤5s, which can meet the continuous operation requirements of sea trials and dynamic experiments.

[0229] 3.3.2 Power Budget and Transmission Efficiency

[0230] Based on the power requirements of the on-axis electronic load, the system power consumption mainly comes from the signal acquisition bridge, front-end amplification, analog-to-digital conversion, microcontroller unit, and wireless transmission module. Calculations show that the total load power at the rotor end is approximately 0.5–2W.

[0231] To ensure system stability and redundancy for future functional expansion, the stator power supply is designed with a power supply capacity of 2–5W, which can still maintain stable energy transmission under maximum load conditions.

[0232] The system design goal is to achieve an energy transfer efficiency of ≥50% within a typical assembly deviation range (radial clearance ≤3mm, axial offset ≤2mm).

[0233] Through coupled magnetic field simulation and experimental calibration, a radial clearance / axial offset-coupling efficiency degradation curve was established, forming a system assembly window and performance tolerance boundary, providing a technical basis for subsequent assembly, debugging and long-term maintenance.

[0234] 3.3.3 Thermal Design, Electromagnetic Compatibility and System Safety

[0235] To ensure long-term stable operation of the system, thermal management optimization was implemented for the coil and core loss paths. A composite heat dissipation structure combining an aluminum alloy shell and thermally conductive silicone is adopted to keep the system shell temperature rise below 25°C, meeting the requirements for continuous operation in marine environments.

[0236] In terms of electromagnetic compatibility (EMC), electromagnetic shielding and functional partitioning were implemented for the high-frequency power transmission module, the 2.4GHz communication unit, and the analog front-end circuitry. Layered wiring and shielding isolation were adopted for signal and power paths, significantly reducing electromagnetic interference (EMI) coupling.

[0237] The system features overcurrent, overtemperature, and undervoltage protection, as well as soft-start functionality, automatically protecting the load and power supply module under abnormal operating conditions. The insulation structure between the stator and rotor has been verified through type testing, and the electrical isolation withstand voltage meets the safety standards for marine power systems (≥1.5kV).

[0238] 3.3.4 Key Parameters and Performance Indicators

[0239] Table 2 Wireless Power Supply Performance Indicators

[0240]

[0241]

[0242] The wireless power supply system, based on electromagnetic coupling resonance, achieves contactless continuous power supply to the rotor, overcoming the lifespan and reliability bottlenecks of traditional slip ring structures. Through energy storage and intelligent management design, it enhances the system's stability and safety under complex operating conditions. The system features modularity, scalability, strong anti-interference capabilities, and high environmental adaptability. It can be widely applied in scenarios involving dual wireless transmission of energy and data for ship propulsion shaft systems, deep-sea equipment power monitoring, and other rotating components, providing crucial technical support for the intelligent monitoring and maintenance of high-end marine equipment.

[0243] 3.4 Display Terminal

[0244] The display terminal has four main interfaces: Home, Average, Trend, and Settings.

[0245] 3.4.1 Homepage Interface

[0246] The homepage includes real-time torque display, real-time speed display, real-time shaft power display, date, status, logo, and interface call buttons. See the detailed interface below. Figure 5 .

[0247] 3.4.2 Average Interface

[0248] The cumulative duration setting interface allows for a range from 1 minute to infinity. Based on the set duration, the system automatically filters power data within the corresponding time period, calculates the average using an arithmetic mean or other suitable algorithm (determined by business needs), and displays the result. See the interface for details. Figure 6 .

[0249] 3.4.3 Trend Interface

[0250] (1) Data switching: The right side displays the switching of speed, torque and power data.

[0251] (2) Time Selection: Based on the current time, set the relative duration to trace back, which can be 5 minutes, 1 hour, or 24 hours. The system displays the trend in the center and the average power at the top based on the set relative duration. See the detailed interface below. Figure 6 .

[0252] 3.4.4 Settings Interface

[0253] (1) Communication Parameter Settings Menu

[0254] (1.1) Communication baud rate;

[0255] (1.2) Stator slave station address.

[0256] (2) Axis parameter setting menu

[0257] (2.1) Shaft outer diameter: XXXX.X (mm);

[0258] (2.2) Shaft inner diameter: XXXX.X (mm);

[0259] (2.3) Shear modulus: XXXX.X (GPa);

[0260] (2.4) Elastic modulus: XXXX.X (GPa);

[0261] (2.5) Poisson's ratio: XX.

[0262] (3) Measurement Parameter Setting Menu

[0263] (3.1) Sampling frequency: XXXX (Hz);

[0264] (3.2) Average time: XXXX (ms);

[0265] (3.3) Averaging method: XX. List two averaging methods.

[0266] 3.5 Installing Components

[0267] The mounting components of the shaft power meter are a crucial foundational structure for the system's mechanical support, energy transmission, and signal acquisition. Their design directly impacts the overall stability and measurement accuracy of the machine. The mounting components primarily consist of a column, a local control box, a wireless power transmitter mounting assembly, a wireless power receiver mounting assembly, and a rotor module mounting assembly. These components work together to secure the shaft power meter, provide power, and facilitate data acquisition.

[0268] 3.5.1 Columns

[0269] The support column is used to support the wireless power transmitter and the local control box of the shaft power meter, and is the main load-bearing structure of the entire system. The column adopts a welded rectangular steel pipe structure with adjustable anchor bolts at the bottom to adapt to different ground levels. A flange connection plate is installed at the top of the column, allowing for fine-tuning of the transmitter's angle and position to ensure the spatial alignment accuracy of the power supply system. The preferred material is Q235B or 304 stainless steel, with a powder-coated or anodized surface treatment to improve corrosion resistance and appearance. The design focus of the column is on structural rigidity and vibration resistance, requiring that the gap between the transmitter and receiver does not exceed 0.5mm at the highest shaft speed to ensure stable and reliable wireless energy coupling.

[0270] 3.5.2 Local Control Box

[0271] The local control box is the core control and signal processing unit of the shaft power meter, primarily responsible for data acquisition, signal conditioning, wireless power supply control, and communication interface management. The control box features an IP65-rated metal enclosure with a front-opening design for easy on-site maintenance and wiring adjustments. Internally, it is equipped with standard DIN rails for modular installation of the power supply, data acquisition board, and communication modules. The control box is fixed to the lower part of the column using flanges or clamps, and cables are introduced into the enclosure through waterproof connectors to ensure dust and water resistance. To improve the system's electromagnetic compatibility, reliable grounding terminals are installed both inside and outside the control box. Critical signal lines are connected using shielded twisted-pair cables, with the shielding layer well grounded to the enclosure. Sufficient space is provided for maintenance and heat dissipation to ensure long-term stable operation of the equipment.

[0272] 3.5.3 Wireless Power Transmitter Mounting Components

[0273] The wireless power supply transmitter mounting assembly provides energy coupling to the receiver on the rotor, enabling contactless power supply to the on-axis measurement system. This assembly consists of a transmitting coil and a support frame, forming a coaxial adjustable structure capable of fine-tuning in both radial and axial directions to ensure the concentricity error between the transmitting and receiving coils does not exceed 0.5mm. The support frame is constructed of aluminum alloy or stainless steel and equipped with a precision fine-tuning slide mechanism, secured with locking screws to ensure its position remains unchanged during operation. A protective cover is installed around the coil to prevent oil mist, dust, and foreign objects from interfering with electromagnetic coupling performance. The power cable is introduced through the inside of the column, avoiding external entanglement and electromagnetic interference, thereby improving the stability and reliability of the wireless power supply.

[0274] 3.5.4 Wireless Power Receiver Installation Components

[0275] The wireless power receiver mounting assembly is fixed on the rotating shaft, forming a magnetically coupled circuit with the transmitter to receive energy transmitted wirelessly and power the rotor acquisition module. The receiver coil adopts a split clamp-type structure for easy installation and ensures good concentricity adjustment performance. Its housing material is made of aluminum alloy or high-strength engineering plastic, featuring lightweight, oil resistance, and corrosion resistance. Internally, it is potted with shock-absorbing and moisture-proof material to improve system reliability. The mounting method uses a lightweight clamping ring structure with an inner hole tolerance grade of H7, ensuring radial runout does not exceed 0.02mm after tightening, guaranteeing high-precision rotation. An external protective cover is installed to prevent exposed rotating parts from causing safety hazards and to provide electromagnetic shielding and protection, thus ensuring long-term stable operation of the system in harsh environments.

[0276] 3.5.5 Rotor Module Mounting Assembly

[0277] The rotor module mounting assembly is used to fix the torque, speed, and signal acquisition modules of the shaft power meter and transmits signals wirelessly to the stationary end. This assembly mainly consists of a sensor clamping ring, a signal conditioning board bracket, and a protective cover. The sensor clamping ring integrates a strain gauge torque sensor and a speed sensor to achieve high-precision measurement of the rotating shaft; the signal conditioning board bracket supports the circuit module and provides a heat dissipation channel; the protective cover encapsulates the entire module to prevent mechanical damage, dust, and electromagnetic interference. During rotor module installation, the coaxiality error with the measured shaft must not exceed 0.03mm. Interference fits or locating pins are used for fixing to prevent rotational slippage. All rotating parts must undergo dynamic balancing to a balance level of G2.5 to ensure smooth system operation and minimal vibration during high-speed rotation.

[0278] 3.6 Anti-interference design

[0279] When designing the acquisition system, necessary channels should be isolated to avoid signal transmission interference.

[0280] (1) Interference coupling method and interference source

[0281] In the field of electronic measurement, electromagnetic field radiation and impedance coupling from various interference sources are commonplace, causing distortion of the measured circuit, instability of instruments, and reduced reliability of measurement data. Interference sources can be divided into natural interference and man-made interference. Natural interference includes atmospheric discharge phenomena such as cosmic radiation and lightning; man-made interference includes discharges from fluorescent lamps and welding machines, electric spark discharges from relays and switches, and mutual interference between high-voltage circuits and power supply circuits. In practice, interference and noise coupling are the most common, including various forms such as electrostatic coupling, mutual inductance coupling, common impedance coupling, and leakage current coupling.

[0282] (2) Anti-interference measures

[0283] This system requires multi-channel parallel synchronous sampling technology, with each channel equipped with an independent A / D converter. It possesses excellent phase characteristics, effectively eliminating crosstalk between channels, and the sampling rate is not limited by the number of channels, significantly improving anti-interference capabilities. Simultaneously, multi-layer shielding and advanced isolation technologies are employed to suppress interference.

[0284] (2.1) Electric field interference suppression: Using good conductors such as copper to construct a complete shield and grounding it well can effectively suppress electric field coupling interference.

[0285] (2.2) Magnetic field interference suppression: The low magnetic resistance characteristics of high permeability materials such as tinplate are used to shunt the magnetic field and reduce the magnetic field inside the shield; differential input is used at the input end to suppress the interference generated by the magnetic field in the input circuit.

[0286] (2.3) Electromagnetic interference suppression: By using the absorption and reflection of electromagnetic waves by tinplate, the electromagnetic field coupling interference is shielded.

[0287] (2.4) Conducted Interference Suppression: Conducted interference is equivalent to the common-mode voltage UC between the input and output grounds. After isolation, the common-mode voltage UCZ1 at the input of the test system is very small because Z2 >> Z1. Furthermore, the differential amplifier's suppression capability effectively suppresses it. After system isolation, for common-mode voltages less than ±500V (DC or AC peak), the common-mode rejection ratio (CMR) is not less than 120dB. In addition, in principle, reducing parasitic capacitance and the equivalent input impedance of the disturbed circuit can reduce electrostatic coupling interference; reducing parasitic mutual inductance can reduce mutual inductance coupling interference; reducing common impedance can reduce common impedance coupling interference; increasing the leakage resistance between the interfering and disturbed circuits or reducing the equivalent input impedance of the disturbed circuit can reduce leakage current coupling interference.

[0288] In summary, this invention is a ship shaft power measurement and management system integrating rotor condition monitoring, wireless power supply, data transmission, and multi-terminal display. It comprises a rotor, stator, wireless power supply system, and display terminal. The rotor uses strain gauges to collect shaft strain signals, processes the data, and wirelessly transmits it to acquire electrical energy. The stator receives and analyzes the data, performing comprehensive control and management such as speed measurement and power calculation. The wireless power supply system uses the principle of electromagnetic induction coupling to provide stable and continuous power to the rotor. The display terminal can display key parameters in real time and supports centralized data upload for monitoring. The system's component design is reasonable, ensuring overall stability and measurement accuracy. Multiple anti-interference measures are adopted to improve system reliability. It can be widely applied to scenarios such as ship propulsion shaft testing, providing technical support for intelligent monitoring and maintenance of high-end marine equipment.

Claims

1. A shaft power monitoring system based on wireless power supply and micro-strain measurement, characterized in that: The rotor, the stator, the wireless power supply system and a display end are included, The rotor part collects shaft strain signals by using strain gauges, and after signal conditioning and digital processing by a microcontroller, realizes non-contact transmission of data through a wireless transmission module, and obtains the required power through a wireless power supply receiving end and a rectifier circuit board; The stator part receives and analyzes the data transmitted by the rotor through a wireless receiving module, and manages the signals and monitors the state by a microcontroller; at the same time, the built-in speed measurement module of the stator monitors the shaft speed in real time, and provides continuous and stable energy support to the rotor relying on the DC power supply and the wireless power supply transmitting end; The wireless power supply system takes the electromagnetic induction coupling between the stator and the rotor coils as the core, establishes an efficient power transmission channel from the stator to the rotor, and provides long-term power supply for rotating parts; The display end realizes data transmission through the 485 communication interface, visualizes the key parameters on the matching display screen in real time, and uploads the data to the upper computer for centralized monitoring, historical analysis and command interaction.

2. The shaft power monitoring system based on wireless power supply and micro-strain measurement according to claim 1, characterized in that: In the system, the shear strain of the measured shaft is measured by strain gauges, and the wireless transmission and reception of torque signals are realized by using a telemetry torque meter. Finally, the shaft torque signal is collected through a collection card. When installing, the signal transmitting device is fixed on the shaft, and the signal transmitting device rotates with the shaft to generate a torque signal. The torque signal is connected to the transmitting device through a wire, and the torque signal is output through the transmitting device. The receiving device receives the torque signal and then transmits it to the computer for effective data analysis and processing, so that the shaft power can be obtained.

3. The shaft power monitoring system based on wireless power supply and micro-strain measurement according to claim 1 or 2, characterized in that: In the system, the torque measurement method is: When a torque of size T acts on a shaft with a length of L, the shaft will deform, and any two shaft cross sections will rotate relative to the center axis to produce a torsion angle. Then the shear stress at point C on the shaft cross section at a distance r from the center is: Where: τ is the shear stress at point C on the shaft cross section; r is the distance from point C to the center; I p - polar moment of inertia of the shaft section with respect to the circle center; For a hollow circular shaft, the polar moment of inertia I p : In the formula: d i - inner diameter of the shaft; d0 is the outer diameter of the shaft; Wherein, the maximum shear stress appears on the outer surface of the shaft: where: τ max - maximum shear stress of the shaft; The torsion angle θ of the shaft per unit length is: Where: G is the shear modulus of the material; The shear modulus G of the material is: Where: E is the elastic modulus of the material; μ is the Poisson's ratio; According to material mechanics, the maximum shear strain γ of the elastic shaft surface is According to formula (6), the following formula can be derived: From formula (6), it can be seen that the torque T can be calculated by directly measuring the torsion angle.

4. The shaft power monitoring system based on wireless power supply and micro-strain measurement according to claim 3, characterized in that: When using strain torque to measure shaft power, strain gauges and telemetry torque meters are mainly used on actual ships. First, four strain gauges are pasted along the given shaft ±45° direction to form a full-bridge circuit, then the strain gauge is converted into a voltage value by using a telemetry torque meter, and finally the torque is calculated by the output voltage value, which is: The strain gauge resistance is R, and the strain ε will cause the resistance change ΔR of the strain gauge. According to the strain effect, the definition of the strain gauge sensitivity coefficient is as follows: wherein: k GF - the sensitivity coefficient of the strain gauge; In the Wheatstone bridge circuit, the bridge output voltage V out There is a certain proportion with the strain ε, assuming the bridge excitation voltage is V EXC , after derivation can be obtained: In the formula: V out - the output voltage (V) of the torque meter; V EXC - the excitation voltage (V) of the electric bridge.

5. The shaft power monitoring system based on wireless power supply and micro-strain measurement according to claim 1 or 2, characterized in that: In the system, the speed measurement method is: First, the magnet is installed on the shaft, the rotation speed of the shaft is determined by the pulse signal interval generated by the Hall sensor, when the shaft rotates, the magnet passes through the probe in front of the sensor, the sensor will generate a pulse, and the pulse signal is transmitted to the counter for counting, and finally the measured rotation speed signal is averaged, that is, the rotation speed of the shaft can be obtained, the rotation speed of the shaft can be calculated according to the following formula: In the formula: ΔT is the interval time of two pulses.

6. The shaft power monitoring system based on wireless power supply and micro-strain measurement according to claim 1 or 2, characterized in that: In the system, the calculation method of shaft power is: The shaft power of the ship shafting is obtained by indirectly measuring the output torque and rotation speed of the shafting, that is, the torque and rotation speed are measured respectively, and then the shaft power of the shafting is obtained, and the calculation formula is as follows: In the formula: P is the shaft power of the shafting (kw); T is the output torque of the shafting (N·m); n is the output shaft rotation speed (r / min).

7. The shaft power monitoring system based on wireless power supply and micro-strain measurement according to claim 1 or 2, characterized in that: The system is installed through an installation assembly, the installation assembly includes a stand, a machine-side control box, a wireless power transmitter installation assembly, a wireless power receiver installation assembly and a rotor module installation assembly, The stand adopts a welded rectangular steel pipe structure, is provided with adjustable foot bolts at the bottom, and is provided with a flange connecting plate at the top end, which is used for realizing angle and position fine adjustment of the transmitter and ensuring spatial alignment accuracy of the power supply system; The machine-side control box is used as a core control and signal processing unit, performs data acquisition, signal conditioning, wireless power supply control and communication interface management, is a metal box structure and adopts a front opening door type design, is internally provided with standard guide rails to modularly install a power supply, a data acquisition board and a communication module, is fixed to the middle and lower parts of the stand through a flange or a clamp, cables are introduced into the box through waterproof joints, reliable grounding terminals are arranged inside and outside the machine-side control box, shielded twisted pair lines are used for connection of key signal lines, and the shielding layer is grounded with the box; The wireless power transmitter installation assembly is used for providing energy coupling for a receiving end on the rotor and performing non-contact power supply of the shaft measurement system, the wireless power transmitter installation assembly includes a transmitting coil and a support frame, the transmitting coil and the support frame constitute a coaxial adjustable structure capable of being finely adjusted in the radial and axial directions, the support frame adopts an aluminum alloy or stainless steel structure and is provided with a precise fine adjustment sliding table mechanism and is fixed through locking screws, a protective cover is arranged around the transmitting coil, and a power supply cable is introduced through the inside of the stand; The wireless power receiver installation assembly is fixed on the rotating shaft and forms a magnetic coupling loop with the transmitting end, is used for receiving wirelessly transmitted energy and supplying power to the rotor acquisition module, and the wireless power receiver installation assembly includes a receiving coil in a split clamp type structure, a shell material thereof is selected from an aluminum alloy or a high-strength engineering plastic, an inside is filled with shockproof and moistureproof materials, and an outside is provided with a protective cover; The rotor module mounting assembly is used for fixing the torque, rotating speed and signal acquisition module of the shaft power instrument, and transmitting the signal to the stationary end by wireless mode. The assembly includes a sensor clamping ring, a signal conditioning board support and a protective cover. The sensor clamping ring integrates the strain torque sensor and the rotating speed sensor together to realize high-precision measurement of the rotating shaft. The signal conditioning board support is used for supporting the circuit module and providing a heat dissipation channel. The protective cover encapsulates the whole module to prevent mechanical damage, dust and electromagnetic interference.

8. The shaft power monitoring system based on wireless power supply and micro-strain measurement according to claim 7, characterized in that: The mounting mode of the receiving coil adopts a light-weight clamping ring structure, the inner hole tolerance level is H7, and the radial runout after tightening is not more than 0.02mm; The rotor module mounting assembly requires that the coaxiality error with the measured shaft is not more than 0.03mm during installation, and interference fit or positioning pin is used for fixation to prevent rotation slip. All rotating parts need to be dynamically balanced and the balance level reaches G2.

5.

9. The shaft power monitoring system based on wireless power supply and micro-strain measurement according to claim 1 or 2, characterized in that: In the system, an anti-interference method is also designed, which is as follows: Multi-channel parallel synchronous sampling technology is adopted, and each channel is equipped with an independent A / D converter; Multi-layer shielding and advanced isolation technology are used to suppress interference, including using good conductors to build a complete shielding body and good grounding to suppress electric field interference; The low magnetic resistance characteristic of high-permeability material is used for magnetic field shunting, and the input end adopts differential input to suppress magnetic field interference; The absorption and reflection of electromagnetic waves by tinplate are used to suppress electromagnetic field interference; the common-mode voltage of the conducted interference is suppressed by isolation and differential amplifier, and common-mode rejection is realized.

Images