Jun Satonobu

Improvement of the longitudinal vibration system for the hybrid transducer ultrasonic motor

This paper presents a symmetric hybrid transducer ultrasonic motor designed to produce large longitudinal vibration stress in the rotor/stator contact interface for high-torque operation. The nodal plane of the longitudinal vibration mode was adjusted to match the rotor/stator contact interface, and the piezoelectric ceramic disks for the longitudinal vibration were installed at the nodal plane of the longitudinal vibration mode for effective excitation. An experimental motor, 20 mm in diameter, using the first torsional vibration mode and the second longitudinal vibration mode was manufactured. A maximum torque of 0.8 N/spl middot/m was achieved in the prototype, an improvement over previous versions.

Construction of Megatorque Hybrid Transducer Type Ultrasonic Motor

A large hybrid transducer type ultrasonic motor has been studied for the purpose of achieving large output torque. The goal of our research is to realize a megatorque (i.e., 1000 kgf.cm) ultrasonic motor. The key to accomplishing this goal lies in obtaining sufficient longitudinal vibration in order to control the frictional force between the rotor and the stator. In this paper, a motor of 120 mm in diameter using the second longitudinal vibration mode is fabricated and investigated, as a preliminary step toward realization of the megatorque ultrasonic motor. As a result of our experiments, the maximum torque of 400 kgf.cm was achieved.

Traveling wave excitation in a flexural vibration ring by using a torsional-flexural composite transducer

This paper presents a new mechanism for traveling wave excitation of the flexural vibration in a ring. A torsional-flexural composite transducer was used to excite two degenerate flexural vibration modes spatially and temporally orthogonal to each other in the ring. The prototype, composed of a 32-mm diameter composite transducer attached along the outer edge of an 180-mm diameter aluminum annular ring, was designed, constructed, and tested. The ring was designed via finite element analysis to operate using a (0,8) transverse flexural traveling wave, and the motion was confirmed experimentally.

Numerical analysis of the symmetric hybrid transducer ultrasonic motor

In this paper, operation of a symmetric hybrid transducer ultrasonic motor with output produced by two rotors connected together via a drive shaft is numerically analyzed and compared with the traditional asymmetric hybrid transducer motor design that produces its output from only one rotor. A one-dimensional finite element model for torsional vibration in the stator and a Coulomb friction model for rotor/stator contact associated with the longitudinal vibration of the motor are introduced. The calculation results demonstrate that the symmetric design is capable of performance comparable with the traditional asymmetric design when an optimum static spring force in the rotor/stator contact interface is applied during operation.

Traveling Wave Ultrasonic Motor Using a Flexural Composite Transducer

This paper presents a new design for a traveling wave ultrasonic motor with a bolt-clamped Langevin transducer. A flexural composite transducer was attached to a ring around its circumference to excite two degenerate flexural vibration modes spatially and temporally orthogonal to each other in the ring for flexural traveling wave excitation. The prototype motor, composed of a 30-mm-diameter composite transducer attached along the outer edge of a 130-mm-diameter ring, was designed and tested. A maximum torque of 1.28 Nm with a maximum efficiency of 3.8% was achieved when driven at an applied voltage of approximately 200 Vrms and a preload of 172 N.

An optimum design for the hybrid transducer ultrasonic motor in symmetrical structure

This study is focused on the optimization of the longitudinal vibration system for a hybrid transducer ultrasonic motor in order to obtain effective friction control at the rotor/stator contacting interface. The basis of our design is that the piezoelectric elements for the longitudinal vibration are located just at the contacting interface, and the interface is tuned to the nodal plane of the longitudinal vibration mode. A prototype motor 20 mm in diameter achieved the maximum torque of 8 kgf/spl middot/cm, which was higher than that of other previously reported motors.

Development of the torque accumulation method for a torsional vibration system

This paper presents a new method to accumulate the output of several torsional transducers together into one output. The torsional transducers are connected around the circumference of a thick metal disk (the accumulator) in which the fundamental torsional mode is excited. The torque of each transducer is transmitted to the accumulator, and the accumulated torque appears on both the top and the bottom surfaces of the accumulator. The authors discuss the torque accumulation and the transformation mechanism analytically by using an equivalent electrical circuit model and obtaining the analytic expression of the torque factor, which represents the maximum output torque per unit voltage applied to the electrical port. In an experimental study, four Langevin torsional transducers 30 mm in diameter attached to an accumulator 100 mm in diameter was used as a prototype. The measured torque factor is found to be proportional to the number of connected transducers, and the calculated torque factor agrees well with the experimentally determined one.

Numerical analysis of the hybrid transducer ultrasonic motor: comparison of characteristics calculated by transmission-line and lumped-element models

In this paper, a hybrid transducer ultrasonic motor is numerically analyzed by using two equivalent electrical circuit models. A transmission-line model for the torsional vibration in the stator, which can model any torsional vibration mode and their combinations, was introduced and compared with a lumped-element model, which modeled the fundamental torsional resonance mode in the stator. The calculation result by using the transmission-line model demonstrated that the second harmonic torsional vibration increased either with the static spring force by which the rotor was pressed to the stator or with the load torque placed on the rotor. The difference in the calculated motor performance between the two models appeared when the second harmonic torsional vibration became large at a sufficient static spring force.