Development With Shaft Power Monitoring System For Marine Diesel Engine Based On The Way Of Phase Difference

The shaft power of a marine diesel engine is one of the most important parameters for powertrain properties, it can serve as the main information source of powertrain monitoring and fault detection and alarm, and it can be used to judge the efficiency, condition, performance of ship-engine-propellor matching, furthermore, it can be used to help determine the working condition of a marine diesel engine for fault diagnosis. Therefore, it is very important to develop a shaft power online monitoring system for marine diesel engines so as to ensure their safety and reliable operation.A marine diesel engine powertain is taken as the research object in this dissertation, the shaft power measurement method is investigated based on non-contact phase difference technology. Some magnetic resistance sensors for non-contact measuring shaft torque are used, a signal acquisition and processing hardware system is set up based on DSP, which can extract phase difference and speed from original signals, and eventually calculate the shaft power. A on-line shaft power monitoring system is developed, which is able to monitor the ship’s running performance combined with other parameters. The main achievements made in this study are as follows:(1) The non-contact measurement principle of shaft power for diesel engine and powertrain is analyzed. With a electromagnetic field analysis software, the magnetic field distribution characteristics are analyzed to study the influence of magnets distribution for the output signal of a magnetic resistance sensor. It is shown that when the magnets not evenly distributed, the output signal of magnetic resistance sensors have an apparent features, so that it is possible to extract the torque and speed measurement even without BDC signal.(2) The hardware circuits of magnetic resistance sensor and signal conditioners are designed. A magnetic susceptibility resistance component is utilized in the sensor, whose output signal has linear relationshitp with change of magnetic field strength through the peak detection circuit, peripheral circuit and the PIC microcontroller, therefore the sensor is able to meet the torque sensor measuring technology requirements; Signal conditioning circuit makes the signal amplitude keep in the requirerriental range of hardware through zeroing and amplifying circuit.(3) The charactertistics of output signal of magnetic resistance sensor in time domain and frequency domain is analyzed, along with verifying experiment on the LabVIEW software platform.Through the simulation experiment; The zero interpolation method is applied to extract the phase difference of torque signal. It is shown that zero interpolation method meets the requirements of measurement precision.(4)The DSP hardware system was builded, which includes the circuit of power, acquisition module, DSPVC5416and its peripheral, liquid crystal display and CAN communication module etc, with functions of acquisition and processing for output signal from the magnetic resistance sensor, display of the related parameters value on LCD panel, and transmitting these processing results to PC through the CAN bus.(5) The shaft power of a diesel engine was test when the ship in sailing, the measurement precision is verified, the reasons of inducing measurement errors are analyzed, some technical measures to reduce the inaccuracy is put forward.The non-contact shaft power measuring method is inverstigated, apart from this; magnetic resistance sensors and peripheral circuits are designed, which satisfied non-contact measurement requirements. The hardware based on DSP platform is designed with functions of acquisition, analysis and processing of torque signal. The feasibility, validity and measuring precistion are verified in a real ship experiment.