The Fabrication And Experiment Of Screw-driven Piezoelectric Motor For Camera Focus

Nowadays, with the development of science and society, piezoelectricmotor which can meet the fast growing needs of high quality motor is used inevery field of our life, such as micronano technology, optical instrument,precise instrument, biomedical, aerospace, automotive electronics,semiconductor inspection and national defense. Piezoelectric motor has someexcellent performances, such as high energy density, simple structure, goodperformances in micro-scale, high pulling torque with low speed, highefficiency etc.With the development of camera system, piezoelectric motor graduallyshows its superiority over other types of motors. But it has its own problems:it may not have simple enough structure, so it will lead to bad performances infalling tests and reliability tests. Because of these reasons, piezoelectric motorcan not be wildly used in the field of camera and cellphone camera lens focus.To solve these problems, based on the previous research on contactdisk-pivot piezoelectric motor which has a rotate speed of over10000rpm anda short response time within1ms, thus, two types of extend and improvedscrew-driven piezoelectric motor used for camera and cellphone camera focususe are designed and fabricated. The piezoelectric motors have a stator withthe shape of straw hat to drive the rotor directly by screw thread structure inthe mode of B11, and use only one piezoelectric ceramic plate. In this study,the micro-vibration and mode shapes were measured and investigated using thefinite element method, Doppler Polytec300-F scanning vibrometer andHEWLETT PACKARD4192A LF Impedenc Analyser. Results showed thatfinite element method can conduct the design of the motor in this work, andwith the easy principle of work and compact structure the two types of motorhave good performances. the piezoelectric motor has a good outputperformance and superiority in controlling of lens zoom of cameras. A series of performance tests have been carried on the two motors, suchas speed test, start time test, and also the influence of working frequency,voltage and load mass are studied in this work, too. Additionally, theinfluence of detailed position of the rotor on its resonant frequency isdiscussed.High or low temperature test is also a very important part in this work, theresults offer good experimental support for the control method of motor undervarious temperatures.