Cheol-Ho Yun

A High Power Ultrasonic Linear Motor Using a Longitudinal and Bending Hybrid Bolt-Clamped Langevin Type Transducer

A hybrid transducer type ultrasonic linear motor using the 1st longitudinal and the 2nd bending vibration modes of a bolt-clamped Langevin type transducer has been proposed and studied for accomplishing high mechanical output. The longitudinal vibration generates the mechanical driving force and the bending vibration controls the frictional force. To obtain large vibration amplitude and large mechanical output, a method of tuning the longitudinal resonance frequency to the bending one was investigated using finite element simulations, and demonstrated experimentally. To avoid magnetic interaction, we employed phosphor bronze for the bolt of the transducer. The prototype motor achieved the no-load velocity of 0.47 m/s and the maximum output mechanical force of 92 N.

Application of a multi-DOF ultrasonic servomotor in an auditory tele-existence robot

A multi-degree-of-freedom (DOF) ultrasonic motor can rotate in three DOFs and does not generate noise. In addition, with an appropriate preloading mechanism, it can generate high torque for its size. The multi-DOF ultrasonic motor is, therefore, anticipated for use as a servomotor in the next generation of robots. However, for several reasons, there have been few applications of multi-DOF ultrasonic motors. One reason is the difficulty in designing a proper preloading mechanism for the motor and the limitation of the size of the stators. Another is the difficulty in developing a control algorithm, due to the motors complex and changing dynamical characteristics, and the serious jaggy motion caused by its very quick response. This paper proposes a preloading mechanism and control algorithm for a multi-DOF ultrasonic motor, considering the motors application to an actual auditory tele-existence robot, TeleHead. TeleHead is an elaborate dummy head robot that has a 3-DOF neck mechanism. The proposed methods achieve smooth and fast multi-DOF rotating motion of the dummy head with little time delay. In the preloading method, tensioned springs generate high preloading force and make up for the lack of torque by compensating for the resistance torque generated by the inclining motion of the dummy head. In the control algorithm, high-DOF motion is managed by high-frequency switching of the rotating axis, and smooth and quick trajectory tracking motion is achieved by introducing feed-forward control using an inverse model, with multiresolution acquired by feedback-error learning. Experimental results verify the high performance of these methods.

A piezoelectric ultrasonic linear micromotor using a slotted stator

A novel ultrasonic micro linear motor that uses 1st longitudinal and 2nd bending modes, derived from a bartype stator with a rectangular slot cut through the stator length, has been proposed and designed for end-effect devices of microrobotics and bio-medical applications. The slot structure plays an important role in the motor design, and can be used not only to tune the resonance frequency of the two vibration modes but also to reduce the undesirable longitudinal coupling displacement caused by bending vibration at the end of the stator. By using finite element analysis, the optimal slot dimension to improve the driving tip motion was determined, resulting in the improvement of the motor performance. The trial linear motor, with a weight of 1.6 g, gave a maximum driving velocity of 1.12 m/s and a maximum driving force of 3.4 N. A maximum mechanical output power of 1.1 W was obtained at force of 1.63 N and velocity of 0.68 m/s. The output mechanical power per unit weight was 688 W/kg.

An Ultrasonic Suction Pump with No Physically Moving Parts

A new ultrasonic suction pump is described in this paper. The pump uses the suction force of a rigid cylinder tube vibrating at an ultrasonic frequency and has no physically moving parts. The pump consists of a longitudinal bolt-clamped Langevin transducer (BLT) combined with a stepped horn working at a resonance frequency of 24 kHz. A glass tube with the length of the half-wavelength-resonance is glued at the tip of the horn. To enhance pump performance, we introduced a reflection plate and a thin rod installed to the end of the glass tube with a small gap. Maximum pressures of 7.2 kPa and 23.5 kPa were recorded using the reflection plate and the thin rod, respectively. In this study, we experimentally investigate the characteristics of the pump and the operating physics. The maximum pressure is a function of the vibration velocity of the end surface of the glass tube and of the gap.

Support Mechanism for the Ball Rotor in the Three-Degree-of-Freedom Ultrasonic Motor

Three types of support mechanism for the ball rotor of a three-degree-of-freedom ultrasonic motor with a single stator have been proposed and studied in order to achieve a large output torque. These support mechanisms could apply a sufficient preload to the ball rotor, and the three-degree-of-freedom rotational movements of the ball rotor were possible. The output torque were 1.7 kgf(.)cm for the z-axis rotation and 2.8 kgf(.)cm for the x-axis rotation at a preload of 4 kgf. The no-load maximum rotation speeds were 5 rps for the z-axis rotation and 4.3 rps for the x-axis rotation

Nano Positioning of a High Power Ultrasonic Linear Motor

In this paper, we present an investigation of the noble linear stage for high power and high precision positioning. The stage is driven by a hybrid-bolt clamped Langevin-type ultrasonic linear motor, which is vibrated at its different modes of resonance frequencies in both the lateral and longitudinal directions. To obtain a high power and high-accuracy motion, the driving frequencies of the two vibration modes must be simultaneous. In this study, to obtain well-matched vibration frequencies, the contact stiffness in the tangential and the normal directions are carefully considered in designing the actuator. In addition, deviations of the electro-mechanical characteristics of the lead zirconate titanate (PZT) actuator are considered in the bolt clamping process of PZT, and the exciting frequencies are adjusted through modification of the actuator length. Finally, the stage is controlled via proportional-integral-derivative (PID) control. As a result, positioning with a resolution of 20 nm and a moving speed of 78 mm/s was achieved with a linear sensor resolution of 15 nm.

Holding Mechanism Using a Resonance System for a High-Power Ultrasonic Linear Motor

To improve the operating stability and controllability of a high-power ultrasonic linear motor, the authors propose a mechanism to hold the vibrator using the resonance of stepped horns. The new holding system can support the motor firmly, without affecting the longitudinal and bending vibration modes. The resonance frequency of the supporting system is designed to be very near to that of the motor. By using the proposed system, the residual vibrations and the settling time in the transient state have been reduced markedly. When supported by the resonance support mechanism, the no-load speed and the maximum thrust force of the motor were not changed even after 8000 complete back-and-forth cycles, while with the one-point support system, the no-load speed fell rapidly and the motor failed after 20 to 30 cycles.

Multi-degree-of-freedom ultrasonic micromotor for guidewire and catheter navigation: The NeuroGlide actuator

A 240-μm diameter ultrasonic micromotor is presented as a potential solution for an especially difficult task in minimally invasive neurosurgery, navigating a guidewire to an injury in the neurovasculature as the first step of surgery. The peak no-load angular velocity and maximum torque were 600u2009rad/s and 1.6 nN-m, respectively, and we obtained rotation about all three axes. By using a burst drive scheme, open-loop position and speed control were achieved. The construction method and control scheme proposed in this study remove most of the current limitations in minimally invasive, catheter-based actuation, enabling minimally invasive vascular surgery concepts to be pursued for a broad variety of applications.

Development of stem structure for flower robot using SMA actuators

As a smart home service robot, the flower robot has various intelligent functions, such as moving mechanism, sensing ability, and home appliance functions. Especially, the moving function is very important function among the various function. The moving function of flower robot consists of the blooming of flower, the swaying of the stem and the stirring of the leaves in the wind. In this paper, we focused on the swaying of the stem structure. As an actuator for stem structure, we adopted coil type SMA and then proposed silicone stem structure with 3 coil type SMA. Using SMA actuator, we designed and fabricated the stem structure with 8 mm of diameter and 50 mm of length. Firstly, we calculated the displacement of the stem structure through mathematical analysis. Secondly, by using numerical simulation, the displacements of the stem structure are simulated. Thirdly, through the experiment of the fabricated stem structure, the displacements can be measured. In addition, the results from the mathematical analysis, the numerical simulation and the experiment are compared. Finally, through the various experiments of the stem structure, its performances are evaluated.

Improved Design for Driving Characteristics in Single Phase Induction Motor with Concentrated Winding

The distributed winding method is generally applied for induction motor to attain the sinusoidal flux distribution. However, in recent years, the concentrated winding method is being investigated as an alternative to lower the material cost of copper coils. To realize, the by-products of the concentrated winding induction motor such as the harmonic flux and the torque deterioration must be addressed. To restrain negative effects of harmonic flux distribution of concentrated winding, the skew of rotor conduction bar that is a very important design variable must be properly chosen. This study is focused on the optimal design of rotor bars skew and winding turns for concentrated winding induction motor. In this study, the control method of harmonic parasitic torque in concentrated winding induction motor is proposed and validated its practicality through the experiment.