Development A Non-contact Shaft Power Testing System Based On Magnetoelectric Method

The shaft power of a marine diesel engine, it can be measured online and servedas an auxiliary parameter for diesel engine condition monitoring and fault diagnosis,to improve the accuracy of monitoring and diagnosis. Furthermore, it can be used toidentify the matching state of ship-engine-propeller, moreover, combining with otherparameters such as fuel consumption and speed, which can provide technical supportfor economic navigation of the ship. Therefore, it has very important significance toimprove the security, reliability and economic of the ship power plant to investigateof the online testing method of marine diesel engine shaft power.An online monitoring shaft power system was developed in this work, based asimulation test bench of a ship power system, using the non-contact magnetoelectricmethod. First of all, the structure and work principle of magnetic resistance sensorwas studied, and the principle of magnetic resistance sensor to measure the torqueand rotational speed was analyzed, as well as a data acquisition system was designedwhich is based on the LabVIEW FPGA Module, including the installation and usageof data acquisition device, the lower machine and the host computer program, it cantake full advantage of flexibility and customizable of the FPGA, combined withLabVIEW graphical interactive interface, the test systems became more simple andflexible. On the LabVIEW software development platform, some original signal wassimulated, analyzed and processed, including zero mean, filtering and extraction ofphase difference, thus, a most suitable method for the test system of filtering andextraction phase difference method was obtained, that is, the zero-offset phase filterand the zero-pole interpolation method to extract phase difference. Finally, acomplete set of shaft power test system used in the simulation test bench was built, aseries of comparative experiments were carried out under different samplingfrequency, different distance of measuring point and different value of torque, andthen the signal processing method was validated. Eventually, some affects factors ofthe precision of shaft power measurement were analyzed.The test system described in this thesis has the following characteristics:1) thenon-contact measurement. The test system not only guarantee the quality of the single transmission, but also keep a certain distance between the magnetic resistancesensor (fixed part) and the sensitive element (rotation part), so it is easy to utilize thetest system in the ship field.2) an external supply power to the magnetic resistancesensor. Due to the adjustable constant voltage supply power to the sensor, thesensitive components do not require power, therefore, it can make the test systemachieve long-term continuous online measurement.3) less external disturbance.Using virtual instrument technology and flexible software function instead of curinghardware devices, the interference of the external hardware circuit was reduced.Therefore, the measurement error generated by the more hardware circuitinterference was effectively avoided.