Study On Method About Torque Measurement Of Ship Shafting Based On Inverse Magnetostrictive Mechanism

Shaft power of a ship shafting is not only the important parameter to assess the running condition of marine engine,but it also can provide technical support for the ship's economic navigation by combining some other parameters such as fuel consumption,rotational speed,navigational speed and so on.So it is the important parameter to analyse ship-engine-propeller matching performance and energy efficiency index.Therefore,it has great significance to monitor marine engine condition and improve the safety,reliability and economy of ship power system through the research of the on-line testing technology of the ship shafting power.The key part of shaft power testing is the torque testing,so,it is necessary to develop an on-line torque sensor with high reliability according to the characteristics of ship shafting.The inverse magnetostrictive effect is the phenomenon of permeability transformation due to the shape of magnetic material changing,in recent years,new materials have been developed continuously,for example,amorphous alloys and nanomicrocrystalline alloys,many properties of which are also superior,so that they have been widely used in transducer and brake with many advantages of non-contact,good dynamic performance,etc..The purpose of this paper is to explore ship shaft torque measuring mechanism based on inverse magnetostrictive effect,and verify its feasibility through experiment,in order to lay the foundation in application of new materials on ship.The working principles of several common torque sensors are analysed at first in this paper,their advantages and disadvantages are also compared.Then,the principle of torque measurement based on the inverse magnetostrictive effect of amorphous alloy is studied,and amorphous alloy about iron is selected as the sensitive material of the sensor.According to electromagnetic field theory,the electromagnetic model of sensor is established using Maxwell software,and the influence of excitation voltage,coil number of turns and magnetic gap to sensor have been stimulatingly calculated.The static torque test bench based on the inverse magnetostrictive effect is also designed.The static calibration testing results keep in line with the simulation one,the 3D simulation model,calculation method and conclusion are all verified well.By comparing simulation result and testing one,it is found that the output voltage of designed torque sensor can vary with the torque,what's more,the excitation voltage,the coil number of turns and the magnetic gap have its own proper range,in this range,the output voltage and torque present good linear relationship.Finally,a diesel engine test bench is selected to carry out the torque dynamic measurement in order to investigate the influence of magnetic gap and rotational speed on designed torque sensor.The dynamic test results show that the proposed torque sensor based on inverse magnetostrictive effect can basically meet the requirements of torque test in the ship,and it is more suitable to measure torque of the low speed marine engines.The research results of this topic show that it has advantages of non-contact torque measurement,such as strong signal outputting,better sensitivity and linearity for torque sensor based on amorphous alloy about iron.It also verifies the feasibility about noncontact measurement of torque(shaft power)in marine engine based on inverse magnetostrictive effect.Therefore,with the development of amorphous alloy materials and the maturation of the coating formation process on the shafting surface,the on-line measurement of ship shaft power will become easy and feasible.