Device and method for measuring power loss of intermediate speed reducer in helicopter ground combined test

Abstract

The invention belongs to the technical field of helicopter tests, and discloses a device and a method for measuring power loss of an intermediate speed reducer in a helicopter ground joint test. The device comprises a decoder, an upper computer, a tail inclined shaft torque acquisition assembly and a tail horizontal shaft torque acquisition assembly. The tail horizontal shaft torque acquisition assembly is mounted on a tail horizontal shaft, acquires the torque of the tail horizontal shaft through a strain gauge and transmits the torque of the tail horizontal shaft to the decoder, and the decoder decodes data and transmits the decoded data to the upper computer; the tail inclined shaft torque acquisition assembly is mounted on a tail inclined shaft, acquires the torque of the tail inclined shaft through a strain gauge and transmits the torque of the tail inclined shaft to the decoder, and the decoder decodes data and transmits the decoded data to the upper computer; and the upper computer calculates the torque and the rotating speed of the tail horizontal shaft and the tail inclined shaft under typical working conditions according to the decoded torque data of the tail horizontal shaft and the tail inclined shaft, and further calculates the power loss.

Description

Technical Field

[0001] The invention belongs to the technical field of helicopter testing, and in particular relates to a device and method for measuring power loss of an intermediate reducer in a ground combined test of a helicopter. Background Art

[0002] The transmission system is the core component of the helicopter. Efficient transmission efficiency and reliable and safe operation are the necessary foundations to ensure the smooth flight of the helicopter. Among them, the intermediate reducer is an important part of the helicopter transmission system. Its function is to transfer the tail transmission power of the main reducer to the tail reducer through the tail oblique shaft according to the requirements of speed and steering. There is a certain power loss in the transmission process itself. Therefore, how to accurately measure the power loss of the intermediate reducer is a difficult problem in the ground joint test of the helicopter. At present, there is no mature solution to meet the needs of intermediate reducer power loss testing. It is necessary to design a power loss measurement method and a set of intermediate reducer power loss measurement devices with light structure, accurate measurement and stable operation to provide reliable data support for main and tail rotor power matching analysis, transmission system design optimization, and test safety.

[0003] Power loss needs to be calculated by input and output power, while power needs to be calculated by measuring the torque and speed of the shaft. The shaft power calculation formula is P = NT / k, where N is the shaft speed (in revolutions per minute), T is the shaft torque (in Nm), and k is the conversion factor based on the international system of units to convert speed and torque units into power units.

[0004] The tail horizontal shaft and tail oblique shaft at both ends of the helicopter intermediate reducer are both thin and hollow structures with high rotation speed. The torque measurement mainly adopts phase difference or strain gauge shaft torque measurement method. The phase difference shaft torque measurement method performs phase contrast processing on the torque sensor signals modified at both ends of the shaft, and calculates the torque load based on the measured torsional stiffness and other numerical values. However, the measurement method is not accurate, and the structure is too complicated when applied to the power loss measurement of the intermediate reducer, which has a great impact on the test safety. The strain gauge shaft torque measurement method directly feedbacks the torque load through the torque strain gauge pasted on the shaft. It has a simple structure and can meet the torque measurement requirements of the intermediate reducer power loss. However, this method currently relies on wireless telemetry equipment to realize data acquisition, and the weight of the traditional telemetry equipment itself has a great impact on the dynamic balance of the shaft. Summary of the invention

[0005] Purpose of the invention: To provide a device and method for measuring power loss of an intermediate reducer in a helicopter ground joint test, so as to realize accurate measurement of power loss of an intermediate reducer in a helicopter ground joint test.

[0006] Technical Solution

[0007] A helicopter ground joint test intermediate reducer power loss measurement device, comprising: a decoder, a host computer, a tail oblique axis torque acquisition component, and a tail horizontal axis torque acquisition component;

[0008] The tail horizontal axis torque acquisition component is installed on the tail horizontal axis, collects the tail horizontal axis torque through the strain gauge, and transmits the tail horizontal axis torque to the decoder, which decodes the data and transmits it to the host computer;

[0009] The tail oblique shaft torque acquisition component is installed on the tail oblique shaft, collects the tail oblique shaft torque through the strain gauge, and transmits the tail oblique shaft torque to the decoder, which decodes the data and transmits it to the host computer;

[0010] The host computer calculates the torque and speed of the tail horizontal axis and tail oblique axis under typical working conditions based on the decoded torque data of the tail horizontal axis and tail oblique axis, and then calculates the power loss.

[0011] Furthermore, the tail oblique axis torque collection assembly and the tail horizontal axis torque collection assembly have the same structure.

[0012] Further, the tail oblique shaft torque collection assembly includes a moving unit and a fixed unit;

[0013] The dynamic unit is installed on the tail oblique shaft and is used to collect the torque data of the tail oblique shaft;

[0014] The fixed unit is installed on the floor, and the data collected by the dynamic unit is transmitted to the fixed unit via wireless transmission, and the fixed unit transmits the data to the decoder via wired transmission.

[0015] Further, the dynamic unit includes: a torque strain gauge, a flexible acquisition board and a rotor coil;

[0016] The torque strain gauge is pasted on the tail oblique shaft, the flexible collection plate is pasted on the tail oblique shaft in an embrace, and the rotor coil is pasted on the tail oblique shaft in an embrace and is arranged in parallel with the flexible collection plate and connected by wire;

[0017] The flexible acquisition board is used to convert the torque data collected by the torque strain gauge into a torque digital signal;

[0018] The rotor coil includes: a power supply coil and a communication coil; the power supply coil is used to supply power to the flexible acquisition board and the torque strain gauge, and the communication coil is used to transmit the torque digital signal to the fixed unit.

[0019] Further, the stator unit includes: an annular mounting bracket, a platform floor and a stator coil;

[0020] The annular mounting bracket is sleeved on the tail oblique shaft and installed on the platform floor;

[0021] The stator coil is mounted on the annular mounting bracket and arranged parallel to the rotor coil;

[0022] The stator coil includes a power supply induction coil and a communication induction coil connected to the decoder;

[0023] The power supply induction coil is used to supply power to the power supply coil;

[0024] The communication induction coil is used to receive data transmitted by the communication coil.

[0025] Furthermore, the stator coil is sleeved on the outside of the rotor coil with a radial distance of 20 mm to 30 mm.

[0026] Furthermore, the torque strain gauge is a Wheatstone full bridge composed of two orthogonal resistors with a resistance value of 350Ω;

[0027] The installation direction of the torque strain gauge forms an angle of 45° or 135° with the generatrix of the cylindrical surface of the tail oblique axis.

[0028] A method for measuring power loss of an intermediate reducer in a helicopter ground joint test is implemented based on the device, and the steps are as follows:

[0029] Step 1: Collect the torque time domain data curves of the tail horizontal axis and the tail oblique axis under typical working conditions;

[0030] Step 2: Calculate the torque T1 of the tail horizontal axis and the torque T2 of the tail oblique axis under typical working conditions;

[0031] Step 3: Convert the torque time domain data curves of the tail horizontal axis and the tail oblique axis into frequency domain data;

[0032] Step 4: According to the rated input and output speeds of the intermediate reducer under typical working conditions, find the first-order rated frequencies in the frequency domain data as the rotational frequency f1 of the tail horizontal axis and the rotational frequency f2 of the tail oblique axis, and calculate the rotational speeds N1 and N2 of the two respectively according to the rotational frequencies;

[0033] Step 5: Calculate the input power P1 and output power P2 of the intermediate reducer according to the torque and speed of the tail horizontal shaft and the tail oblique shaft under typical working conditions;

[0034] Step 6: Calculate the power loss μ based on the input and output power of the intermediate reducer.

[0035] Furthermore, the typical operating condition is the stable power operation state of the helicopter ground joint test bench.

[0036] Furthermore, the power loss μ is calculated as follows:

[0037]

[0038] In summary, the beneficial effects of the present invention are as follows:

[0039] The present invention provides a method and device for measuring the power loss of an intermediate reducer of a helicopter based on strain gauge shaft torque measurement. A flexible acquisition device with a light and thin structure is used to measure the input and output torque of the intermediate reducer, which greatly reduces the influence of the measuring device on the dynamic balance of the tail horizontal axis and the tail oblique axis; the stator coil and the rotor coil inductive power supply method are selected to effectively ensure the stable operation of the shaft torque measuring device; relying on the strain gauge shaft torque measurement technology, the torque data of the tail horizontal axis and the tail oblique axis are respectively subjected to spectrum analysis to obtain the speed of the tail horizontal axis and the tail oblique axis, without the need to install a speed measurement device separately, thus saving the installation space at both ends of the intermediate reducer. The measurement method and device are simple in principle, with low installation and maintenance costs, and can safely and accurately measure the power loss of the intermediate reducer during the ground joint test of the helicopter, and provide reliable data support for the power matching analysis of the main and tail rotors, the optimization of the transmission system design, and the guarantee of test safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 The schematic diagram is a structural diagram of a power loss measurement device for an intermediate reducer in a helicopter ground joint test.

[0041] Figure 2 It is the time domain curve of shaft torque and the corresponding frequency domain curve.

[0042] Figure 3 This is the system block diagram of the intermediate reducer power loss measurement device. DETAILED DESCRIPTION

[0043] 1. Torque measurement device

[0044] An axis torque measuring device includes a tail oblique axis torque strain gauge 4, a tail oblique axis flexible acquisition board 5, a tail oblique axis induction coil ring, a tail horizontal axis torque strain gauge 10, a tail horizontal axis flexible acquisition board 11, a tail horizontal axis induction coil ring, a decoder 16, and a host computer 17.

[0045] Figure 1 The schematic diagram of the shaft torque measurement device is shown in Figure 1. Among them, 1 is the intermediate reducer, 2 is the tail oblique shaft, 3 is the tail horizontal shaft, 4 is the tail oblique shaft torque strain gauge, 5 is the tail oblique shaft flexible acquisition board, 6 is the tail oblique shaft rotor coil, 7 is the tail oblique shaft stator coil, 8 is the tail oblique shaft annular mounting bracket, 9 is the tail oblique shaft platform floor, 10 is the tail horizontal shaft torque strain gauge, 11 is the tail horizontal shaft flexible acquisition board, 12 is the tail horizontal shaft rotor coil, 13 is the tail horizontal shaft stator coil, 14 is the tail horizontal shaft annular mounting bracket, 15 is the tail horizontal shaft platform floor, 16 is the decoder, and 17 is the host computer.

[0046] The tail slant axis torque strain gauge 4 is pasted on the tail slant axis 2, and its signal is connected to the tail slant axis flexible acquisition board 5 pasted on the shaft. The tail slant axis induction coil ring is divided into two parts: the tail slant axis rotor coil 6 and the tail slant axis stator coil 7: the tail slant axis rotor coil 6 is fixed on the tail slant axis 2 by the shaft-holding pasting method, and is arranged and connected with the tail slant axis flexible acquisition board 5 at intervals, including a power supply coil for powering the tail slant axis flexible acquisition board 5 and a communication coil for transmitting the tail slant axis torque signal; the tail slant axis stator coil 7 is pasted on the inner wall of the tail slant axis annular mounting bracket 8, including a power supply induction coil for inductive power supply to the power supply coil and a communication induction coil for transmitting the tail slant axis torque data; the tail slant axis annular mounting bracket 8 is composed of two symmetrical semicircular ring structures, fixed on the tail slant axis platform floor 9 by screws, and installed in a circular shaft-holding manner corresponding to the tail slant axis rotor coil 6, and maintaining a safety distance of 20mm to 30mm between the tail slant axis 2.

[0047] The tail horizontal axis torque strain gauge 10 is pasted on the tail horizontal axis 3, and its signal is connected to the tail horizontal axis flexible acquisition board 11 pasted on the axis. The tail horizontal axis induction coil ring is divided into two parts: the tail horizontal axis rotor coil 12 and the tail horizontal axis stator coil 13: the tail horizontal axis rotor coil 12 is fixed on the tail horizontal axis 3 by the axis-holding pasting method, and is arranged and connected with the tail horizontal axis flexible acquisition board 11 at intervals, including a power supply coil for powering the tail horizontal axis flexible acquisition board 11 and a communication coil for transmitting the tail horizontal axis torque signal; the tail horizontal axis stator coil 13 is pasted on the inner wall of the tail horizontal axis annular mounting bracket 14, including a power supply induction coil for inductive power supply to the power supply coil and a communication induction coil for transmitting the tail horizontal axis torque data; the tail horizontal axis annular mounting bracket 14 is composed of two symmetrical semicircular ring structures, fixed on the tail horizontal axis platform floor 15 by screws, and installed in a ring-shaped axis-holding manner corresponding to the tail horizontal axis rotor coil 12, and maintaining a safety distance of 20mm to 30mm between the tail horizontal axis 3.

[0048] The decoder 16 is fixed on the tail horizontal axis platform floor 15 by screws, and is connected to the tail oblique axis power supply induction coil and the tail horizontal axis power supply induction coil by power supply cables, and is connected to the tail oblique axis communication induction coil and the tail horizontal axis communication induction coil by communication cables. The host computer 17 exchanges torque data with the decoder 16 via a network cable.

[0049] Torque strain gauge

[0050] According to the torque measurement requirements of the tail horizontal axis and the tail oblique axis, the torque strain gauge should select two orthogonal resistance strain gauges with a resistance of 350Ω to form a Wheatstone full bridge. When mounting the gauge, the resistance strain gauge should be installed in a direction of 45° or 135° with the generatrix of the shaft cylindrical surface. When calibrating the torque load coefficient of the tail horizontal axis and the tail oblique axis, the torque load coefficient is calibrated by directly applying torque. One end of the shaft is fixed and a lever is fixed at the other end. A known torque is applied at the top of the lever in stages to simulate the change of the real shaft torque state. The output voltage value of the torque strain gauge signal is measured, which has a one-to-one correspondence with the given known torque value. Linear fitting can obtain the change relationship curve between the torque load and the output voltage of the tail horizontal axis and the tail oblique axis, as well as the torque load calibration coefficient.

[0051] Flexible acquisition board

[0052] The flexible acquisition board is mainly constructed as a flexible circuit board. The power supply module, data acquisition module, microcontroller and communication transmission module adopt an integrated design. The structure is light and thin, and can be conformally installed on the curved surface of the tail horizontal axis and the tail oblique axis. It has little effect on the dynamic balance of the axis and is highly safe. The power supply module receives the electromagnetic waves provided by the power supply coil and converts them into electrical energy to supply the entire flexible acquisition board. The data acquisition module transmits the collected torque voltage signal to the microcontroller for data processing, and then sends the processed shaft torque data to the communication coil through the communication transmission module.

[0053] Due to the high rotation speed of the tail horizontal axis and the tail oblique axis, the flexible collection board installed on it needs to be fixed with high-strength and high-toughness structural adhesive. The specific installation steps are as follows:

[0054] 1) Clean the oil stains and dirt on the installation site;

[0055] 2) Wrap paper tape (3M2308) around the installation location;

[0056] 3) Wrap double-sided tape;

[0057] 4) Stick the flexible collection board to the shaft with double-sided tape;

[0058] 5) Connect the flexible acquisition board to the torque strain gauge and the rotor coil for debugging;

[0059] 6) Use a brush to apply SW-9-6 structural adhesive on the surface of the flexible collection board;

[0060] 7) Wrap fiber tape around the outside of the structural adhesive;

[0061] 8) Apply Loctite 411 glue on the side of the fiber tape to prevent air from entering through the side gaps.

[0062] Induction coil ring

[0063] The flexible acquisition board is powered by the stator coil and rotor coil induction power supply method. The power supply voltage is high and stable. The stator power supply induction coil is powered by the decoder and a stable alternating magnetic field is formed near it. The rotor power supply coil generates an induced electromotive force by repeatedly cutting the alternating magnetic lines of force to obtain the power supply voltage, which is then supplied to the flexible acquisition board. The stator communication induction coil senses the electromagnetic wave signal emitted by the rotor communication coil and transmits the electromagnetic wave signal to the decoder.

[0064] Due to the high rotation speed of the tail horizontal shaft and the tail oblique shaft, the rotor coils installed thereon also need to be fixed with high-strength and high-toughness structural adhesive. The specific steps for installing the rotor coils are as follows:

[0065] 1) Clean the oil stains and dirt on the installation site;

[0066] 2) Wrap paper tape (3M2308) around the installation location;

[0067] 3) Wrap double-sided tape;

[0068] 4) Wrap the magnetic conductive material around the double-sided tape;

[0069] 5) Wind the coil on the magnetic conductive material and use double-sided tape for pre-fixing;

[0070] 6) Connect and debug with the flexible acquisition board;

[0071] 7) Use a brush to apply SW-9-6 structural adhesive on the surface of the rotor coil;

[0072] 8) Wrap fiber tape around the outside of the structural adhesive;

[0073] 9) Apply Loctite 411 glue on the side of the fiber tape to prevent air from entering through the side gaps.

[0074] The stator coil is pasted on the inner wall of the annular mounting bracket, and the annular mounting bracket is fixed to the tail horizontal axis and tail oblique axis platform floor by screws. The specific steps for installing the stator coil are as follows:

[0075] 1) Clean the oil stains and dirt on the annular mounting bracket;

[0076] 2) Wrap paper tape (3M2308) around the mounting bracket;

[0077] 3) Wrap double-sided tape;

[0078] 4) Wrap the magnetic conductive material around the double-sided tape;

[0079] 5) Wind the coil on the magnetic conductive material and use double-sided tape for pre-fixing;

[0080] 6) Adjust the induction distance from the rotor coil;

[0081] 7) Use a brush to apply SW-9-6 structural adhesive on the surface of the stator coil;

[0082] 8) Wrap fiber tape around the outside of the structural adhesive;

[0083] 9) Apply Loctite 411 glue on the side of the fiber tape to prevent air from entering through the side gaps.

[0084] Decoder

[0085] The decoder includes a power module, a power supply module and a communication decoding module, wherein the power module supplies power to the power supply module and the communication decoding module, the power supply module sends electric energy to the power supply induction coil through the power supply cable, and the communication decoding module modulates and demodulates the electromagnetic wave signal emitted by the communication induction coil through the communication cable and sends the obtained tail horizontal axis and tail oblique axis torque data to the host computer through the network cable.

[0086] Host computer

[0087] The upper computer communicates with the decoder via a network cable to transmit the torque data of the tail horizontal axis and the tail oblique axis in real time, and uses fast Fourier transform (FFT) to perform spectrum analysis on the time domain data of the tail horizontal axis and the tail oblique axis torque, and calculates the speeds of the tail horizontal axis and the tail oblique axis, that is, the real-time input and output speeds of the intermediate reducer, and then calculates the input and output power of the intermediate reducer and its power loss μ.

[0088] 2. Power loss measurement model

[0089] 1. Based on the above shaft torque measurement device, the real-time torque voltage data of the tail horizontal shaft and the tail oblique shaft are obtained, and then the tail horizontal shaft torque T1 and the tail oblique shaft torque T2 are calculated according to the relationship between the torque load and the output voltage change of the tail horizontal shaft and the tail oblique shaft.

[0090] 2. Under the typical working condition of the helicopter ground joint test bench in stable power operation, the fast Fourier transform (FFT) is used to perform real-time spectrum analysis on the 10-second torque time domain data of the tail horizontal axis and the tail oblique axis to obtain the frequency domain data of the torque of the tail horizontal axis and the tail oblique axis.

[0091] 3. According to the working principle of the intermediate reducer, the input shaft of the intermediate reducer is the tail horizontal shaft, and the output shaft is the tail oblique shaft. The rated input and output speeds of the intermediate reducer under typical working conditions can be used to obtain the first-order rated rotation frequency of the torque acting on the tail horizontal shaft and the tail oblique shaft, respectively. Further combined with the frequency domain data analysis of the tail horizontal shaft and the tail oblique shaft torque, the frequency components close to the first-order rated rotation frequency are obtained as the actual rotation frequency f1 of the tail horizontal shaft and the actual rotation frequency f2 of the tail oblique shaft, and the speed N1 of the tail horizontal shaft and the speed N2 of the tail oblique shaft are calculated respectively.

[0092] N1=60·f1

[0093] N2=60·f2

[0094] Wherein, f1 is the rotation frequency of the horizontal axis of the tail (in Hz), and f2 is the rotation frequency of the oblique axis of the tail (in Hz).

[0095] Figure 2 The time domain curve of the shaft torque for 10 seconds and its corresponding frequency domain curve. Under the stable operation state of this typical working condition, the rated shaft speed is 600 rpm, and the first-order rated rotation frequency acting on the shaft torque is 10Hz. Combined with the frequency domain curve analysis, the frequency component close to the first-order rated rotation frequency is 10Hz, that is, the actual rotation frequency of the shaft is 10Hz. Further calculation shows that the shaft speed under the stable operation state of this typical working condition is 600 rpm.

[0096] 4. The input power P1 of the intermediate reducer can be calculated by measuring the torque T1 and speed N1 of the tail horizontal shaft:

[0097]

[0098] The output power P2 of the intermediate reducer can be calculated by measuring the torque T2 and speed N2 of the tail oblique shaft:

[0099]

[0100] Wherein, k is the conversion factor obtained by converting the speed and torque units into power units based on the International System of Units.

[0101] 5. The power loss of the intermediate reducer is μ, which can be calculated from its input power P1 and output power P2:

[0102]

[0103] 3. Power loss measurement system

[0104] Figure 3 This is the block diagram of the intermediate reducer power loss measurement system.

[0105] The tail horizontal axis flexible acquisition board sends the collected input torque voltage signal of the intermediate reducer to the decoder through wireless transmission, and the tail oblique axis flexible acquisition board sends the collected output torque voltage signal of the intermediate reducer to the decoder through wireless transmission. The decoder supplies power to the tail horizontal axis flexible acquisition board and the tail oblique axis flexible acquisition board respectively through wireless induction power supply, and transmits the torque voltage data to the host computer through the network cable for data processing. According to the relationship between the torque load and output voltage change of the tail horizontal axis and the tail oblique axis, the input torque T1 and output torque T2 of the intermediate reducer are calculated, and the input speed N1 and output speed N2 of the intermediate reducer are obtained by spectrum analysis of the torque data, and finally the power loss μ of the intermediate reducer is output according to the power loss measurement model of the intermediate reducer.

Claims

1. A helicopter ground joint test intermediate reducer power loss measurement device, characterized by: The device comprises: a decoder, a host computer, a tail oblique axis torque acquisition component, and a tail horizontal axis torque acquisition component; The tail horizontal axis torque acquisition component is installed on the tail horizontal axis, collects the tail horizontal axis torque through the strain gauge, and transmits the tail horizontal axis torque to the decoder, which decodes the data and transmits it to the host computer; The tail oblique shaft torque acquisition component is installed on the tail oblique shaft, collects the tail oblique shaft torque through the strain gauge, and transmits the tail oblique shaft torque to the decoder, which decodes the data and transmits it to the host computer; The host computer calculates the torque and speed of the tail horizontal axis and tail oblique axis under typical working conditions based on the decoded torque data of the tail horizontal axis and tail oblique axis, and then calculates the power loss.

2. The device according to claim 1, characterized in that: The tail oblique axis torque collection assembly and the tail horizontal axis torque collection assembly have the same structure.

3. The device according to claim 2, characterized in that: The tail oblique shaft torque acquisition assembly includes a moving unit and a fixed unit; The dynamic unit is installed on the tail oblique shaft and is used to collect the torque data of the tail oblique shaft; The fixed unit is installed on the floor, and the data collected by the dynamic unit is transmitted to the fixed unit via wireless transmission, and the fixed unit transmits the data to the decoder via wired transmission.

4. The device according to claim 3, characterized in that: The dynamic unit includes: torque strain gauge, flexible acquisition board and rotor coil; The torque strain gauge is pasted on the tail oblique shaft, the flexible collection plate is pasted on the tail oblique shaft in an embrace, and the rotor coil is pasted on the tail oblique shaft in an embrace and is arranged in parallel with the flexible collection plate and connected by wire; The flexible acquisition board is used to convert the torque data collected by the torque strain gauge into a torque digital signal; The rotor coil includes: a power supply coil and a communication coil; the power supply coil is used to supply power to the flexible acquisition board and the torque strain gauge, and the communication coil is used to transmit the torque digital signal to the fixed unit.

5. The device according to claim 3, characterized in that: The stator unit includes: an annular mounting bracket, a platform floor and a stator coil; The annular mounting bracket is sleeved on the tail oblique shaft and installed on the platform floor; The stator coil is mounted on the annular mounting bracket and arranged parallel to the rotor coil; The stator coil includes a power supply induction coil and a communication induction coil connected to the decoder; The power supply induction coil is used to supply power to the power supply coil; The communication induction coil is used to receive data transmitted by the communication coil.

6. The device according to claim 5, characterized in that: The stator coil is sleeved on the outside of the rotor coil, with a radial distance of 20mm to 30mm.

7. The device according to claim 4, characterized in that: The torque strain gauge is a Wheatstone full bridge composed of two orthogonal resistors with a resistance value of 350Ω; The installation direction of the torque strain gauge forms an angle of 45° or 135° with the generatrix of the cylindrical surface of the tail oblique axis.

8. A method for measuring power loss of an intermediate reducer in a ground joint test of a helicopter, implemented based on any of the above-mentioned devices, characterized in that: Here are the steps: Step 1: Collect the torque time domain data curves of the tail horizontal axis and the tail oblique axis under typical working conditions; Step 2: Calculate the torque T1 of the tail horizontal axis and the torque T2 of the tail oblique axis under typical working conditions; Step 3: Convert the torque time domain data curves of the tail horizontal axis and the tail oblique axis into frequency domain data; Step 4: According to the rated input and output speeds of the intermediate reducer under typical working conditions, find the first-order rated frequencies in the frequency domain data as the rotational frequency f1 of the tail horizontal axis and the rotational frequency f2 of the tail oblique axis, and calculate the rotational speeds N1 and N2 of the two respectively according to the rotational frequencies; Step 5: Calculate the input power P1 and output power P2 of the intermediate reducer according to the torque and speed of the tail horizontal shaft and the tail oblique shaft under typical working conditions; Step 6: Calculate the power loss μ based on the input and output power of the intermediate reducer.

9. The method according to claim 8, characterized in that: The typical operating condition is the stable power operation state of the helicopter ground combined test bench.

10. The method according to claim 8, characterized in that: The power loss μ is calculated as follows:

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