CN102135460B - Photoelectric non-contact rotating shaft torque and power measurement device - Google Patents

Abstract

The invention relates to a device for measuring torque and power of a photoelectric non-contact rotating shaft, which mainly comprises a controller (11), a computer (12), a photoelectric code disc and a photoelectric switch, wherein: at least two photoelectric coded disks are arranged on the measured rotating shaft (1), and each photoelectric coded disk corresponds to one photoelectric switch and is provided with a plurality of light through holes and light barriers which are uniformly distributed; the computer is connected with the output interface of the controller through a serial data line, and the measuring signal input end of the controller is respectively connected with each photoelectric switch through a lead; the signals output by all the photoelectric switches are transmitted to a computer after being logically calculated and processed in a controller, and the time-varying curves of the torque and the power are displayed in a display (13) or a liquid crystal screen (14). The invention can carry out long-time on-line measurement and is not in contact with the measured rotating shaft; the deviation generated by the measuring environment can be inhibited; the device has the advantages of convenience in installation, wide application, high precision, lasting stability and the like.

Description

Photoelectric non-contact rotating shaft torque and power measurement device

technical field

The invention relates to a measuring device, in particular to a photoelectric non-contact rotating shaft torque and power measuring device.

Background technique

Of the methods that have been used to measure power on rotating shafts of various types of machinery, a large number rely on the way strain gauges are attached to the rotating shaft. The transmission methods of strain gauge signals mainly include slip rings and telemetry methods. The slip ring can ensure that the strain gauge signal is transmitted to the acquisition circuit uninterruptedly when the shaft rotates. The telemetry method needs to install a transmitter on the rotating shaft to provide power by rotating the battery, and the transmitter transmits the current change of the strain gauge to the collection electronic circuit through a wireless signal.

Some newer systems now use Hall sensors. This solution generally installs two large gears at a certain distance on the rotating shaft to pick up the signal. Two Hall effect sensors are respectively arranged at the measurement sensitive places on the two large gears, and the two Hall devices can output pulses with the same width during the rotation of the shaft. When the shaft is loaded, the phase difference between the two pulses changes. The torsion angle of the loaded shaft can be calculated by detecting the phase difference between the two pulses.

Patent No. CN1162990A published by the Patent Office of the People's Republic of China discloses a system for detecting the torque of a rotating shaft using a laser optical fiber and a laser detector. It is that two rotating code discs are respectively installed at appropriate distances apart from each other on the rotating shaft. A beam of laser light is irradiated onto the first code wheel through an optical fiber, and then received and modulated into a laser pulse by the light modulator corresponding to the first code wheel, and then irradiated to the second code wheel through optical fiber transmission, and passes through the second code wheel. After a code disc is received by the second laser sensor and converted into an electrical pulse signal, the electrical pulse width at this time represents the phase difference between the two code discs. When the rotating shaft is loaded, the width of the final output electrical pulse will increase. Through this phase difference, the twist angle of the rotating shaft can be calculated, so that the torque of the rotating shaft after the load is applied can be calculated.

For the first system above, in order to obtain effective accuracy, it is necessary to ensure that the trigger points of the two sensors do not drift, and with the use of time and/or temperature changes, it is possible for the trigger points of the two sensors to drift relative to each other , and the two may even be in opposite directions. Although the second system uses a single detector to measure the laser signal emitted by a single light source, it can reduce the possible trigger point drift of the two detectors to some extent, but the change of the trigger point of the single detector itself with temperature drift cannot be measured. Therefore, it is impossible to completely eliminate this systematic error. In addition, the second system adopts an optical modulation structure. This method of modulating light into a pulse signal and then outputting it will also have a certain delay, because a certain amount of systematic error that cannot be eliminated is introduced into the system. From these points, neither of the two torque measurement systems can overcome the trigger point drift caused by the characteristic change of the detector itself.

Contents of the invention

The technical problem to be solved by the present invention is: in order to overcome the problem that the trigger points of the two photoelectric switches drift with time and/or temperature changes in the measurement, provide a photoelectric non-contact rotating shaft torque and power measurement device, which can completely The influence of the drift generated by the trigger point of the photoelectric switch on the detection result is eliminated.

The present invention solves its technical problem and adopts the following technical solutions:

The photoelectric non-contact rotating shaft torque and power measuring device provided by the present invention is mainly composed of a controller, a computer, a photoelectric code disc and a photoelectric switch, wherein: there are at least two photoelectric code discs, which are installed on the measured rotating shaft, Each photoelectric code disc corresponds to a photoelectric switch and is equipped with multiple uniformly distributed light holes and light baffles; the computer is connected to the output interface of the controller through a serial data line, and the measurement signal input end of the controller is connected to each The photoelectric switches are connected; all the signals output by the photoelectric switches are transmitted to the computer after logical calculation and processing in the controller.

The corresponding central angles of the light holes and light baffles on each photoelectric code disc are exactly the same.

The light-through hole on the photoelectric code disc is a fan-shaped hole.

The above-mentioned photoelectric non-contact rotating shaft torque and power measuring device provided by the present invention has the purpose of measuring the torsion angle of the measured rotating shaft by using photoelectric technology, and the measurement basis is all logical quantities, specifically: During the process, at least two photoelectric switches are used to detect the square wave signal output when the same number of photoelectric code discs sweep the corresponding photoelectric switch, and the torsional deformation of the measured rotating shaft is measured by detecting the phase difference between the two square waves. Angle signal, after the angle signal is logically calculated and processed in the controller, the computer calculates the torque and power of the measured rotating shaft.

The device does not come into contact with the measured rotating shaft during the measurement process, and does not affect the normal operation of the shaft.

The device can simultaneously measure the torque variation of multiple sections on the same rotating shaft system to be tested.

The device simultaneously measures the torque and power changes on several different rotating shafts under test.

The present invention can use the following method for logic calculation: the phase difference pulse signal is obtained by calculating the square wave pulse signal generated by the corresponding light hole on the photoelectric code disc in the field programmable gate array (FPGA) device, and then by A counter with a certain frequency counts the width of the phase difference pulse, and converts the phase difference into a digital quantity for storage.

In the present invention, two photoelectric code discs are installed on the measured rotating shaft. During the rotation process of the measured rotating shaft, two photoelectric switches are used to detect the square wave signal output by the two photoelectric code discs when they sweep over the corresponding photoelectric switch. The phase difference between the two square waves is used to measure the angle of torsional deformation of the rotating shaft, so as to calculate the torque and power of the measured shaft.

Compared with the prior art, the present invention has the following main advantages:

1. No contact with the rotating measuring shaft, and can measure online for a long time: the shaft torque acquisition method adopts the method of photoelectric code disc combined with photoelectric switch, and the torque of any section or the entire shaft on the shaft can be obtained during the shaft rotation process , and even the torque distribution of the entire shaft can be obtained by introducing multiple photoelectric code discs. The entire measurement process does not come into contact with the measured shaft system, and does not affect the normal rotation of the shaft system, which is convenient for long-term online measurement applications.

2. Can suppress the deviation caused by the measurement environment: In terms of torque calculation, the logic circuit calculation in the controller can eliminate the trigger point drift of the photoelectric switch with time and/or temperature, and ensure the long-term stability of the system. The advantage is that it cannot be achieved by using a single light source and a single photosensitive electron detector in some previous patents.

3. Easy installation: the photoelectric code disc rotates with the shaft on the shaft, and the photoelectric switch is fixed on the mounting frame. Measure rotational torque and power over the entire shaft. In this way more bearings and spacers can be placed on the shaft without being affected by the measurement.

4. Wide application: It can be used to simultaneously measure the torque and power changes of multiple sections on one shaft system, or measure the torque and power changes of several different shaft systems at the same time.

5. It has the performance of high precision and long-lasting stability. The measurement accuracy of the torsion angle of the measured rotating shaft can reach 0.001 degrees, and can be used for long-term on-line monitoring of the power of the shafting shaft of the ship.

Description of drawings

Fig. 1 is a structural schematic diagram of the photoelectric non-contact rotating shaft torque and power measuring device of the present invention.

Figure 2 is a schematic diagram of the photoelectric code disc installed on the measured shaft.

Fig. 3 is a schematic diagram of the phase difference between output pulse signals of two photoelectric switches.

Fig. 4 is a schematic diagram of the logic relationship after the output pulse edge of the photoelectric switch drifts.

Fig. 5 is a schematic diagram of the application of multiple photoelectric code discs to shaft torque measurement.

In the figure: 1. The measured rotating shaft; 2. The first photoelectric code disc; 3. The first light hole; 4. The second photoelectric code disc; 5. The second light hole; 6. The first photoelectric switch; 7 .The second photoelectric switch; 8. Bearing; 9. The first wire; 10. The second wire; 11. Controller; 12. Computer; 13. Display; 14. LCD display screen; 17. The fourth photoelectric code disk; 18. The fifth photoelectric code disk; 19. The sixth photoelectric code disk.

Detailed ways

The photoelectric non-contact rotating shaft torque and power measuring device proposed by the present invention adopts two gear discs or photoelectric encoder discs installed at an appropriate distance on the measured rotating shaft, and the two photoelectric codes are used during the rotation of the measured rotating shaft. The discs are swept across the corresponding high-speed photoelectric switches to generate electrical pulse output. When a load is added to the rotating shaft to be tested, the rotating shaft will intensify its torsion, and a small relative torsion will occur between the two gear discs. By detecting the phase difference between the two pulses output by two photoelectric encoders, the torsion angle of the measured rotating shaft can be calculated. When this angle is calculated, when the rotational speed is also measured or known, the torque and power of the rotating shaft can be calculated.

The invention also provides a logical calculation method for two pulses, which can completely eliminate the influence of the trigger point of the photoelectric switch on the detection result due to the drift caused by environmental factors such as temperature.

The present invention will be further described below in conjunction with the embodiments and accompanying drawings, but the content of the present invention is not limited.

The photoelectric non-contact rotating shaft torque and power measuring device provided by the present invention has a structure as shown in Figure 1, and the device is mainly composed of a controller 11, a computer 12, a photoelectric code disc and a photoelectric switch, wherein: the photoelectric code disc has many They are mounted on the measured rotating shaft 1. Each photoelectric code disc is provided with a photoelectric switch and a plurality of uniformly distributed light holes. The computer 12 is connected to the output interface of the controller 11 through the data line to realize the data communication and the transmission of the control signal, and the measurement signal input end of the controller 11 is respectively connected with each photoelectric switch through the wire. The signals output by several photoelectric switches are transmitted to the computer 12 after logic calculation and processing in the controller 11 .

The present embodiment provides two photoelectric code discs, wherein: the first photoelectric code disc 2 and the second photoelectric code disc 4 correspond to the first photoelectric switch 6 and the second photoelectric switch 7 respectively. When the photoelectric code disc rotates with the measured rotating shaft 1, the blades on the photoelectric code disc will periodically block and open the optical path between the photodetector and the light-emitting diode on the photoelectric switch, and the output of the corresponding photoelectric switch is the same Periodic low and high pulses. The high-level output part of the photoelectric switch is used in the calculation process. Therefore, we have adopted a special design different from the previous ones in the design of the light hole of the photoelectric code disc.

The structure of the first photoelectric code disk 2 and the second photoelectric code disk 4 is as shown in Figure 2: the two photoelectric code disks adopt a symmetrical design, that is, the first optical hole 3 and the blocking hole on the photoelectric code disk The central angles corresponding to the light panels 15 are completely the same. In this way, when the photoelectric code disc sweeps the photoelectric switch, the output electric pulse signal is a square wave pulse with a duty ratio of 1:1. Either positive pulse or negative pulse can be used as the signal for torque detection, depending on the specific application. The photoelectric switch can be installed at any position on the circumference of the photoelectric code disc according to the principle of easy installation, as long as the blades of the photoelectric code disc can completely block the light signal when it sweeps the photoelectric switch. In addition, it is necessary to ensure that when two or more sets of photoelectric code discs and photodiode systems are installed, the positions of each photodiode on the circumference of each photoelectric code disc are as identical as possible to maintain consistency during detection.

Each light hole on the two photoelectric code discs must be designed as a fan-shaped structure. Since the rotational angular velocity of the measured rotating shaft 1 is constant during the measurement process, no matter which section of the optical hole the optical path of the photoelectric switch conducts, the conduction time is only related to the central angle corresponding to the optical hole. Therefore, in the design process of the light hole, it must be ensured that the center of each sector coincides with the center of the measured rotation shaft 1, so that the pulse width output by the photoelectric switch is proportional to the angular velocity of the shaft rotation. The central angle corresponding to each light hole can be determined according to the need of measurement accuracy, as long as it is ensured that the output photoelectric pulse width corresponding to the central angle of the light hole can still satisfy the torsion angle when the rotational speed of the measured rotating shaft is the largest. According to the measurement accuracy requirements, such a central angle size is appropriate.

The invention adopts the combination of two photoelectric code discs and a photoelectric switch to detect the torsion angle, and the information related to the torsion angle is included between the two pulse signals output by the photoelectric switch. In the logic circuit, a certain logic calculation can be adopted for the two pulse signals, so as to eliminate the photoelectric switch trigger point drift caused by the ambient temperature and time in the two pulses. The final measurement results are digitized first, and then can be stored and processed in the computer, and the current torque value and the trend curve of torque over time are displayed in real time on the computer.

The present invention adopts the structure of two photoelectric code discs and photoelectric switch to measure torque and has another advantage. Since it is necessary to install two photoelectric code discs on the measured rotating shaft 1 at an appropriate distance to ensure the accuracy of the measurement, however, generally there will be obstacles similar to the bearing 8 in Fig. 1 on the large-scale measured rotating shaft, If methods such as laser are adopted, these obstacles can only be crossed by optical fiber. Using the combination of photoelectric code disc and photoelectric switch to detect the torque and power of the measured rotating shaft will not be affected by these obstacles on the measured rotating shaft, and the photoelectric code disc can be installed on any suitable position on the measured rotating shaft place.

The measured rotating shaft 1 is the object to be measured by the shaft torque and power measurement system.

Above-mentioned photoelectric code disc, its structure is with prior art, for example: be used with the grating encoder of measuring motor rotating speed. However, the grating encoder uses the number of output pulses to measure the rotational speed of the motor, and what is described here is to use two such photoelectric code discs to measure the angle at which the shaft is twisted.

The controller 11 adopts FPGA and microprocessor to form a logic calculation and control system. Its structure is: FPGA is used as a logical operation module to obtain the digital quantity of the angle of the measured shaft twist; the microprocessor collects the digital quantity of the twisted angle of the shaft and transmits it to the computer 12 through the serial interface.

The computer 12 is an ordinary desktop computer or a notebook computer, and the computer 12 communicates with the controller 11 through a serial interface.

The first photoelectric switch 6 and the second photoelectric switch 7 are composed of infrared light emitting diodes and infrared photodiodes. Both are high-speed photoelectric switches with high response frequency and short rise time.

The working process of the device of the present invention is as follows: the photoelectric code disc scans the photoelectric switch to form light/dark pulses, and the output of the corresponding photoelectric switches is high/low level pulses. In principle, there is only a logically opposite relationship between bright and dark signals, so whichever one is used can be used for the calculation of the torsional angle. As mentioned earlier, the design is based on bright pulses, that is, high-level pulses output by photoelectric switches. When there is no load on the measured rotating shaft 1, the corresponding first light-through holes 3 and second light-through holes 5 on the first photoelectric code disc 2 and the second photoelectric code disc 4 sweep through the photoelectric switch respectively, resulting in Two high-level pulse outputs. There is a fixed phase difference between the two bright pulses, which can be recorded in advance as the initial phase, and the initial phase is set as t. When a load is added to the measured rotating shaft 1, due to the twisting on the rotating shaft, a relative offset occurs between the first light through hole 3 and the second light through hole 5 at this time, and the two output channels of the photoelectric switch The phase difference between the bright pulses will also change, and the value of the phase difference will increase with the increase of the load. Let the increased phase difference at this time be Δt. Through the change of this phase difference, the change of the torsion angle between the two photoelectric code discs can be calculated, combined with the physical parameters such as the elastic modulus of the measured rotating shaft material, the torque change of the rotating shaft after loading can be calculated. This principle is shown in Figure 3. When the load is applied, the width of the phase difference between the two pulses output by the first photoelectric switch 6 and the second photoelectric switch 7 will increase to t+Δt.

In order to extract the phase difference between the two code discs, the pulse signals output from the two photoelectric switches are input into the logic circuit, and the two signals are subjected to XOR operation to extract the phase difference between them. When the measured rotating shaft rotates, the logic circuit outputs a series of pulses, and the pulse width represents the phase difference between the two photoelectric code discs. The pulse waveform is shown in Figure 4. In the figure, A and B are respectively marked for two waveforms with phase difference, and it is assumed that A and B respectively represent the output waveforms of the first photoelectric switch 6 and the second photoelectric switch 7 in FIG. 1 .

As mentioned earlier, the photoelectric sensor will change with temperature and use time, which will cause the trigger point to drift. This phenomenon cannot be overcome in products that only use a single sensor. For the measurement method that uses two sensors, if no compensation is performed, it is likely to cause very large errors due to the different directions of the trigger point drift of the two sensors. . For the design using two photoelectric sensors in the present invention, after the equipment works into a stable state, the designed logic calculation program can be started to compensate the trigger point drift of the two sensors with time and temperature, offsetting the two The drift of the sensor makes the phase difference between the output signals of the two sensors coincide with the steady state. The principle of photoelectric sensor trigger point drift offset is shown in Figure 4: For the phase difference between the two signals of A and B, before no load is applied, it represents the initial phase of the measurement system. After the load is applied, the increment of the phase difference Will be used to calculate the magnitude of the twist angle on the axis of rotation.

In Figure 4, the dotted line signals on the two signals of A and B indicate that there is a certain trigger point drift phenomenon on each signal, and the shaded part represents the magnitude of the drift. Suppose that the signal of A and B has an advanced drift ΔA, and the signal of B has a trigger point drift. Hysteresis drift ΔB. When there is no trigger point drift, directly XOR the A and B signals to obtain the phase difference between the two signals. In the figure, A xor B (org) represents the original phase difference signal. However, when the trigger point drifts, an error occurs in the phase difference between the two signals obtained after the direct XOR, and A xor B (cur) is used in the figure to represent the current phase difference signal. However, by comparing the AND signal A and B (org) before the trigger point drift between A and B and the AND signal A and B (cur) after the trigger point drift between A and B, it can be found that the two The difference between the two signals is just the algebraic difference of the trigger point drift error on the two paths of A and B. Therefore, in the calculation process, we only need to record in advance the result of the phase comparison between the two signals of A and B at this time when the system is working stably as a reference for the stable work of the system. No matter how long the work is later, In time, as long as the phase difference obtained by the XOR of the current A and B signals and the sum of the current two signals and the results are subtracted from the previously saved A and B original signal and results, the phase difference can be eliminated. The error caused by the drift of the trigger points of the two sensors can be used to obtain the real phase difference.

By adopting the above-mentioned logic calculation method, the present invention can overcome the error caused by sensor trigger point drift that has not been eliminated in previous related designs. This module can also be used in other fields where the same two sensors with correlation are used to measure their deviation.

According to Figure 4, one XOR calculation of the two signals of A and B generates two phase differences, and the calculation of eliminating drift can be performed after averaging the two phase difference signals to suppress random errors. The phase difference signal obtained each time can be quantified by a counter with a certain frequency. The higher the counter frequency, the higher the accuracy of the calculation. However, the longer the data length in the calculation process, the longer it takes. long. The appropriate counter frequency can be determined according to the system error situation. Every time the shaft rotates a circle, multiple pulse signals will be generated, and the obtained phase differences can be summed, and then averaged and updated according to the appropriate number of shaft rotations or appropriate time intervals to eliminate the random noise error.

The number of teeth of the photoelectric code disc is fixed, so the number of pulses output by the photoelectric switch is certain for each rotation of the shaft. A timer can record the time required to generate these pulses for each rotation of the measured rotating shaft. , so that the current rotation speed of the measured rotating shaft can be calculated, that is, the RPM value. The RPM value with higher precision and resolution can be obtained by choosing a timer with higher precision.

During the measurement, first record the phase difference t of the output of the two photoelectric switches when no load is applied, and then record the phase difference t+Δt after adding the load, so that the offset Δt can be calculated. In order to eliminate the inaccurate factors caused by periodic motions such as vibration, the signals representing the torsion angle can be superimposed and averaged every certain number of rotations of the shaft. Then, based on the average value of the previously measured RPM and the knowledge of the material parameters of the shaft, the torque on the measured rotating shaft and the power of the shaft can be calculated.

The electric pulse signal output from the photoelectric switch is introduced into the controller 11 through the first wire 9 and the second wire 10 for preprocessing, and then the phase between the two code discs is obtained and calculated by the logic circuit in the controller 11 The variation of the difference, and the calculation result is transmitted to the computer 12 through the serial port. The rotational speed, torque and power of the shaft can be displayed in real time on the display 13 and/or LCD display 14 of the computer 12 in the form of curves and numbers, and the curves can reflect the changes of various physical quantities with time.

In addition to being able to measure physical quantities such as the torque of the entire measured rotating shaft by installing two photoelectric code discs at a certain distance on the measured rotating shaft, another application of the present invention is that it can wait on the measured rotating shaft. The distance is set with multiple photoelectric code discs, as shown in Figure 5: four photoelectric code discs are installed on the measured rotating shaft 1, which are respectively the third photoelectric code disc 16, the fourth photoelectric code disc 17, and the fifth photoelectric code disc. Disk 18, the sixth photoelectric code disk 19. By the same method, the torque change on each section of the tested rotating shaft is detected step by step, so as to obtain the torque distribution on the tested rotating shaft, and it is possible to analyze the changes of the torque and power of each section of the tested rotating shaft under load. Situations to refine measurement and analysis. This application was not possible with previous torque measurement systems.

The biggest advantage of the present invention is that, as shown in Fig. 1, the way to obtain the torque of the measured rotating shaft 1 adopts the combination of the first photoelectric code disc 2 and the second photoelectric code disc 4 in combination with the first photoelectric switch 6 and the second photoelectric switch 7 In this way, the torque of any segment or the entire shaft on the measured rotating shaft can be obtained, and even the torque distribution of each segment on the entire measured rotating shaft can be obtained by introducing multiple photoelectric code discs; in terms of torque calculation, through the controller The calculation of the logic circuit in 11 can eliminate the trigger point drift of the first photoelectric switch 6 and the second photoelectric switch 7 with time and/or temperature, which can ensure the long-term stability of the system; the controller is equipped with multiple photoelectric pulse inputs port to realize the simultaneous acquisition and calculation of multiple sets of phase differences. In addition to measuring the torque and power of multiple segments on the shaft at the same time, it can also simultaneously collect the torsion angles of multiple shafts and calculate the torque and power of multiple shafts. Compared with Strain gauges or steel strings can only measure one shaft at a time, which has the advantage of saving measurement time and manpower.

Claims (5)

1. A photoelectric non-contact rotating shaft torque and power measuring device is characterized in that it is mainly composed of a controller (11), a computer (12), a photoelectric code disc and a photoelectric switch, wherein: there are at least two photoelectric code discs, They are installed on the measured rotating shaft (1), each photoelectric code disc corresponds to a photoelectric switch and is provided with a plurality of evenly distributed light baffles and fan-shaped light holes, and the corresponding central angles of the light holes and light baffles are Exactly the same; Computer (12) links to each other with the output interface of controller (11) by serial data line, and the measurement signal input end of controller (11) is connected with each photoelectric switch respectively by wire; The signal that all photoelectric switches output is in control After being logically calculated and processed in the device (11), it is transmitted to the computer (12). 2. The use of the photoelectric non-contact rotating shaft torque and power measuring device according to claim 1, characterized in that photoelectric technology is used to measure the torsion angle of the measured rotating shaft, and the measurement basis is all logical quantities, specifically: in the measured During the rotation of the rotating shaft, use at least two photoelectric switches to detect the square wave signal output when the same number of photoelectric code discs sweep the corresponding photoelectric switches, and measure the occurrence of the measured rotating shaft by detecting the phase difference between the two square waves. The angle signal of torsional deformation, after this angle signal is through logical calculation and processing in the controller (11), the torque and power of the measured rotating shaft are calculated by the computer (12); Described angle signal adopts following method in controller (11) to carry out logical calculation and processing: by the square wave pulse signal that the corresponding light-through hole on the photoelectric code disc produces in the field programmable gate array device or obtain after operation The phase difference pulse signal, and then count the width of the phase difference pulse through a counter with a certain frequency, and convert the phase difference into digital storage. 3. The use according to claim 2, characterized in that the device does not come into contact with the measured rotating shaft during the measurement process, and does not affect the normal operation of the shaft. 4. The use according to claim 2, characterized in that the device can simultaneously measure the torque variation of multiple segments on the same rotating shaft system to be measured. 5. The use according to claim 2, characterized in that the device simultaneously measures the variation of torque and power on several different rotating shaft systems to be tested.

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