Research Of Friction Controlled Inertial Piezoelectric Rotary Actuator

Piezoelectric actuators are widely used in aerospace,optical engineering,bio-medicine,ultra-precision processing and other fields due to their advantages of high resolution,compact structure,convenient control,and no electromagnetic interference.Compared with other types of actuators,inertial piezoelectric actuators have the advantages of high resolution,compact structure,simple control circuit,large stroke,and low cost.However,they also have problems such as difficult adjustment of friction,insufficient driving capacity,and low stability.In order to solve the above problems,based on the working principle of inertial piezoelectric actuators that cooperate inertial impact force/torque and frictional force/torque to achieve directional movement,two types of friction-controlled inertial piezoelectric rotary actuators are proposed.The static and dynamic characteristics of the driving element-piezoelectric bimorph vibrator were analyzed;different friction models were compared,and the Lu Gre friction model was selected to express the friction force/torque of the actuator;mechanical and electromagnetic friction-controlled inertial piezoelectric rotary actuators were designed,the working principles of different actuators were discussed,theoretical analysis,simulation and experimental verification on two actuators with different friction-controlled structures were carried out.1.Research on basic theory of inertial piezoelectric actuatorFirstly,the static and dynamic characteristics of the piezoelectric bimorph vibrator are explored.A variety of dynamic friction models are introduced,and the Lu Gre friction model is chosen in combination with the actual situation to express the friction force/torque that the actuator receives during the motion process.According to the working principle of the friction adjustment structure,the mechanical friction adjustment structure and the electromagnetic control friction adjustment structure are designed respectively.A friction model that can describe the magnitude of frictional force/torque and its effect is introduced,and it is simulated and calculated by SIMULINK.Secondly,based on the dynamic model of the piezoelectric bimorph vibrator and the Lu Gre friction model,the dynamic model of the whole actuator is built.The simulation results verify the feasibility of the inertial piezoelectric actuator,and provide a theory basis for the structural design and experimental test of the actuator.2.Research on mechanical friction-controlled inertial piezoelectric rotary actuatorTo solve the problem that difficult adjustment of friction of the inertial piezoelectric rotary actuator and the weak driving ability,a mechanical friction-controlled inertial piezoelectric rotary actuator was designed and manufactured.The actuator was explored from three aspects: structural design,mechanical analysis,and performance testing.The results show that the friction torque of the actuator is adjustable,combined with the asymmetric piezoelectric bimorph vibrator,under the same signal excitation,the angular velocity is increased from 1.88mrad/s to 130.23mrad/s,which is increased to 6.5 times compared with the original one.And the maximum angular velocity of 6.87rad/s can be obtained,the resolution is increased from 7.98?rad to 2.80?rad,which is increased to 2.8times,but the actuator also has the problem of serious frictional wear,and the stability of actuator is not high due to the discontinuous adjustable friction torque.3.Research on electromagnetically controlled friction-controlled inertial piezoelectric rotary actuatorAiming at the problem of low output stability of mechanical friction-controlled inertial piezoelectric rotary actuators,an electromagnetically controlled friction-controlled inertial piezoelectric rotary actuators was designed and manufactured.The working mechanism and movement process of the actuators were introduced,and the dynamic model of the whole actuator was established.The performance test of the actuator was carried out.The test results show that the friction torque of the actuator is continuously adjustable,which reduces frictional wear.Under certain signal excitation,the displacement linearity determination coefficient of is 0.99.Under different voltages,the fluctuation rate r and standard deviation S of 10 experiments are 10.7%,4.6%,2.9% and 0.016 mrad,0.011 mrad and 0.008 mrad,respectively.The friction torque of the mechanical friction-controlled inertial piezoelectric rotary actuator proposed in this paper is adjustable,and the drive capability of the actuator is improved.However,the actuator also has problems such as frictional wear,inconvenient adjustment of the friction torque,and low stability.The proposed electromagnetic control friction-adjusting structure is able to realize continuous adjustment of friction torque,reduce frictional,and effectively improve the stability of the actuator.