Study On The Design Of Integrated Starter/Generator For Multi Rotor Oil-powered Unmanned Aerial Vehicle

The power system of the traditional multi rotor oil-powered unmanned aerial vehicle(UAV)consists of gasoline generator,starting motor,propeller,on-board battery and reducer.The limited capacity of the on-board battery and lack of power supply unit limit the endurance time of the UAV.Integrated Starter/Generator(ISG)is used instead of starting motor,one machine is dual-use,providing power source,and multi machine power generation can provide power source for electrical load.ISG is the core of power system of the multi rotor oil-powered UAV,and its electromagnetic performance affects the operation of the starting/generator system.For the ISG of UAV,it is necessary to provide enough output torque to drive the engine for ignition in a short time under the electric condition,and the input power and input voltage at both ends of the load should be met under the power generation condition.At the same time,it also needs to achieve small size,light weight,and good heat dissipation to meet the actual load requirements and environmental temperature requirements of UAV.Because of its small size,light weight,small loss,high efficiency and simple mechanical structure,permanent magnet synchronous motor(PMSM)is very suitable for the application in the field of UAV motor.In this thesis,the research contents of ISG for multi rotor oil powered UAV can be divided into the following parts:Firstly,combining the structural form of multi rotor oil powered UAV and the operating characteristics of the power system,the operating characteristic curve and main electromagnetic performance of the motor are proposed.According to the principle and structure of the PMSM,the overload capacity of the motor is improved by changing the structure parameters of the stator and rotor,analyzing the selection of the pole slot matching and the size of the permanent magnet(PM),and finally the structure of the 42 pole 36 slot fractional slot concentrated winding is determined;The selection of motor materials to meet the operating environment conditions of multi rotor UAV,and the corresponding solutions to the motor lightweight problem are proposed.Secondly,the changing rule of demagnetization area of the PM at different time and current is analyzed,and the magnetic density values of all PMs in the unit motor at different positions are compared.Based on the demagnetization phenomenon of the PM,a new type ofasymmetric magnetic pole structure is proposed,and the key parameters of the magnetic pole structure are optimized.Compared with the conventional magnetic pole structure,the new magnetic pole structure improves the anti-demagnetization ability of the pole when the output torque is satisfied.Finally,the electromagnetic performance of the ISG under the condition of electric and power generation is simulated and verified by the finite element method.In view of the phenomenon that the local temperature rise of the motor may be too high when the motor operates in the state of short-time and high overload,the transient temperature rise of the motor is simulated and compared with the actual situation;Under the condition of power generation,three-phase bridge uncontrolled rectifier circuit and step-down chopper circuit are built to make the motor output meet the requirements of power generation system.