The Key Technology Research On Main Propulsion High Energy Density Permanent Magnet Motor Of Unmanned Aerial Vehicle

UAV Main Propulsion Permanent-magnet Motor (MPPM) requires high energy density(power and torque density), and the UAV flight condition is complex, divided into groundtaxiing, take-off and climb, cruise, descent and landing five stages. The energy density ofmotor is the highest in the climbing stage while the temperature of motor is the highest in theearly cruise. New problems of the motor design and analysis are appeared due to high energydensity and complex working condition. This doctoral thesis focuses on the key technology ofMPPM for UAV. The main contents are as follows:For MPPM, according to the requirements of volume and weight and the particularity ofheat load that is5times to heat load of ordinary motor, this doctoral thesis particularlyresearches the design method of ultra-high energy density permanent magnet motor. The effectof structural parameters on motor energy density is researched in theory. The different poles,pole arc coefficient, thickness of permanent magnet and motor size are compared to researchthe effect on air gap flux density, the d-axis and q-axis reactance and cogging torque. TheMPPM magnetic circuit structure is optimized. Different rib, non-uniform air gap duo to rotorout arc, length between permanent magnet and rotor inner diameter is analyzed to research theeffect on air gap flux density and EMF. The basic MPPM optimization design method is given.The core loss calculation method of MPPM is researched at high frequency and high fluxdensity, especially considering the impact of local hysteresis loop on hysteresis loss. Thehysteresis loss factor Kminfor each local loop is set according to the empirical formula, and thecalculation formula for correction coefficient of core loss is given under high electrical load.High energy density will cause the increase of motor temperature rise. The temperature risewill be an important indicator of assessment on main propulsion motor. MPPM uses openstructure to improve energy density, which has good ventilation; However, Reynolds numberof the cooling air is over10000, and the strong turbulence characteristics of fluid increasecomplexity for calculating temperature field. In this doctoral thesis, according to fluidmechanics and heat transfer theory, considering the effect of high frequency skin effect oncopper loss, the fluid solid coupling physical models and mathematical models to study theMPPM temperature field are established under strong wind cooling conditions for thecharacteristics of motor open architecture. The temperature distribution of main components and fluid is given, and the temperature rise of main components in different workingconditions is analyzed. The temperature rise characteristics of MPPM under different thermalload conditions, different climb time and climb angle are researched. The suitable heat loadrange is3000-5500A2/cm·mm2for MPPM of UAV, which provides theoretical reference fordesigning heat load of main propulsion motors.MPPM has characteristics of extra-high energy density, which asks a higher requirementfor mechanical strength and vibration. Based on elasticity theory, the calculation model ofmechanical strength for main components is established and the stress distribution of motorunder different flight conditions of UAV is analyzed. According to the stress analysis structure,the influence of motor cover support ribs on mechanical strength of motor house is analyzed.Based on the modal analysis theory, the vibration characteristic of rotor body is analyzed.Based on the elasticity matrix theory, modes at different frequencies are analyzed. Consideringthe vibration frequency caused by the flow fluctuations of actual operation of UAV, thevibration frequency and quality participation factor of MPPM are researched, and some waysto avoid the occurrence of resonance are given.The MPPM prototype was developed successfully and the first flight test was completed.The ground tests, wind tunnel tests and flight tests were performed for MPPM prototype.MPPM prototype performance indicators were: weight20kg, power25kW, torque100N·m,energy density6.25kW·N·m/kg2, which were much higher than the national level. The highesttemperature rise is appeared in the early cruise during flight test, and the maximumtemperature rise was89.49K while the maximum core temperature was105.07K. Thesimulation results, wind tunnel test data and flight test data of MPPM were compared amongeach flight conditions, which provided the correctness of theoretical analysis.