A novel frequency match method for resonant-type smooth impact drive mechanism with Langevin transducer

Resonant-type smooth impact drive mechanism (RSIDM) uses the resonant vibrations of piezoelectric transducer to synthesize approximate saw-tooth wave vibration with high frequency and amplitude, which extends the driving state of piezoelectric impact motor (PIM) from quasi-static state to resonant state with great increase of power driving capability. The key and difficulty for the design of RSIDMs is to seek out two available natural vibration modes and match their resonant frequencies with desired ratio. Although the material and structural parameters can be theoretically and numerically analyzed to obtain the exact ratio of resonant frequencies, there might be a significant gap in the actual situation due to material differences and manufacturing tolerances. A flexible method for the adjustment of frequency ratio is still a critical matter that requires to be solved. This paper proposes a symmetrical structure of Langevin transducer for the RSIDM with a simple frequency match method. The first and second longitudinal vibration modes in the free condition are used to synthesize the resonant saw-tooth wave vibrations in the ends of the transducer. The resonant frequency ratio of the two vibration modes is naturally close to the desired ratio of 1:2. By replacing the materials at the nodes of the two vibration modes, equivalent stiffnesses and masses of two vibration modes are changed in the opposite direction, which lead to a considerable adjusting range of the resonant frequency ratio around 1:2. With finite element simulation, the results of frequency adjustment process is carried out and the effectiveness of frequency match method is validated.