Research On Ultrasonic Motor Used For Micro Rotor Aircraft

With the increasing demand for monitoring,detection and rescue in limited space,micro air vehicle?MAV?has become a research hotspot in recent years.Ultrasonic motor?USM?has been widely concerned due to its advantages of high energy density,compact structure and so on.But in recent years,the development of high-speed rotary USM has some problems such as high driving voltage,complex driving method,etc.,which fail to realize its application in MAV.In order to solve the problems in existing powerplant,this paper explored the piezoelectric driving method of MAV and designed a high-speed rotary USM with low driving voltage.The main contents include:1.Aiming at the problems of high driving voltage and low power efficiency in existing powerplant for MAV,a new design of multi-spoke disc-type rotary USM based on in-plane standing wave is proposed.The finite element method was used to optimize the structure parameters,and the modal analysis of the stator was carried out.2.The prototype was manufactured and assembled,and its weight is 2 grams.The experimental results of the prototype show that it has the characteristics of low driving voltage,easy control of output and so on.Its optimal working frequency band is from 98.3kHz to 98.7kHz,and the optimal preload is0.5N.The optimization of stator was carried out which significantly improved the output performance of the optimized prototype.The unloaded rotational speed and torque of the prototype reaches 3340rpm and 0.284 mN·m respectively when 20 V_pp driving voltage applied.The driving voltage of the USM is significantly lower than existing high-speed rotary actuators and the power efficiency is 51%which is much higher than similar-sized DC motors,of which the typical power efficiency is about 20%.3.In view of the application in MAV,a suitable rotor wing was selected and its dynamic characteristics were analyzed experimentally.The rotational speed reaches 1760rpm at 20V_pp driving voltage.When driving voltage reaches 50V_pp,the rotor wing can provide about 2.87g lift force,which can maintain the prototype hovering on the guide rail.The experimental results indicate that the USM has good output performance and it is expected to be used as powerplant of micro rotor aircraft.