Transducer for an ultrasonic linear motor with flexible driving part

An ultrasonic motor using two sandwich-type vibrators is a high-speed and large-thrust motor. The maximum speed is 3.5 m/s and the maximum thrust is 51 N. But the maximum efficiency is low, 28%. We thought a slip between the driving part and the rotor was a cause of the low efficiency. The slip is caused by a speed difference between the driving part whose speed changes like a sine curve and the rotor whose speed is almost constant. Then we made a transducer for an ultrasonic linear motor with a flexible driving part. The flexible driving part has 4 cuts and can bend slightly so that the speed difference should decrease. The decrease was verified by a distortion of the sine curve of the flexible driving part and meant a decrease of the slip.