Light Weight Research On Ultrasonic Motor Using Composite Bending Modes

Complex modal ultrasonic motor has a large force (torque), flexible structureand has a broad application prospect. To simplify the subsequent control circuit, thedesigners often degenerate the frequency. This largely limits the motor structureflexibility and performance. Mode degeneracy problem is the inevitable problem inthe process of the complex modal ultrasonic motor design. But we can adopt the sametype modal to solve this problem.Our laboratory proposed a kind of motor which is symmetric in the structure andusing the two orthogonal bending vibrations. It successfully avoided the modaldegenerate problem of the modal hybrid ultrasonic motor. The result of theexperimental prototypes also demonstrated that this type of motor has the advantageof mechanical output. But the bending vibration complex motor which is developedcurrently, it has a large quality and volume, and it need to be further optimized andimproved, to solve this problem. This paper presents a lighter ultrasonic motor usingcomposite bending vibration modes to achieve the purpose of the lower quality andthe increasing power density. The lighter ultrasonic motor can adapt the occasionwhich has a special requirements in quality.This paper analyzed the first-order and second order elliptical trajectory at thefoot of composite bending vibration mode ultrasonic motor and their consistency indriving. Then basing on the effective circuit theory, the effective electromechanicalcoupling coefficient keand mechanical quality factor Qmwere calculated. Basing onthe admittance circle theory, the characteristic frequency of the motor and equivalentcircuit parameters were gained. And this paper analyzed the effect of the equivalentcircuit parameters on keand Qm. Then proposed the basic structure of the first orderbending vibration lightweight composite mode ultrasonic motor, and select theappropriate materials, and conduct the ANSYS finite element simulation analysis.Finally, produced two prototypes using PZT-4and using PZT-8separately to do theexperimental tests. The tests results of the two prototypes’ vibration testing andelectrical characteristics are in a good agreement with the and theoretical analysis,and then do the mechanical properties test.