前野 隆司

This paper describes a development of an ultrasonic clutch as a new passive element for a haptic device using passive force feedback. The ultrasonic clutch can solve conventional problems of passive elements such as time delay, instability, and large size by using unique characteristics of ultrasonic motor such as high response, silent motion, and nonmagnetic feature. It is also designed to be smaller than conventional ones by cogitating its structure. The clutch fixes or unfixes the rotor by use of ultrasonic levitation phenomenon. First, we designed the structure of the ultrasonic clutch using an equation of ultrasonic levitation phenomenon, and results of both structural analysis and frequency analysis of the stator. Then we manufactured the ultrasonic clutch and conducted a driving experiment. Finally, we successfully verified that the maximum value of the levitation force was around 20N and the static friction torque of the ultrasonic clutch was up to 0.14Nm.

多自由度超音波モータを用いた内視鏡下手術用多自由度鉗子を開発した。すなわち, 術者動作検出のための入力部, ヒト手首と同等の自由度を有する鉗子部およびマスタ・スレーブ制御法から成るシステムを提案し, 動作を確認した。

フィンガの関節に弾性要素を用いた, ワイヤ駆動のロボットハンドを開発した。弾性要素を線形ねじりばねで近似したフィードフォワード制御法とワイヤ張力を計測して, ニューラルネットワークを構成する制御法を提案し, 関節の角度制御を行った。

脚型移動ロボットの運動パターン生成に対して, 進化的計算を適用する場合のシミュレーションから実機に移行する際の問題点と, 実環境下での自律行動中に新たな学習が行えないという問題点を解決するために, ヒトのイメージトレーニングを模倣した手法を提案した。本手法は, 実環境下でロボットと環境との相互作用に関するモデルをニューラルネットワークにより学習し, このモデルを用いたシミュレーション上で進化的計算により運動パターンを生成するという手法である。また, シミュレーションにより提案手法の有効性を確認した。

本研究では, 小型で多自由度な運動を実現するロボットハンドを開発するために, 関節に弾性ヒンジを用いたワイヤ駆動機構を提案する。提案した機構を用いて18自由度の小型ロボットハンドを開発する。

本研究では, 人間と同等の形状および自由度を有する超音波モータ内蔵型ロボットフィンガの開発を行う。本フィンガは, 弾性要素を用いたワイヤ駆動機構を特徴とし, 柔軟で安定した動作を実現する。

Linear ultrasonic motors have been formerly designed by trial and error of designers. Therefore, the geometry of the vibrator for these linear ultrasonic motors is generally limited to simple one. The output power of the linear ultrasonic motor is not maximized by optimization for designing the geometry of the vibrator. In the present study, a linear ultrasonic motor having high power is designed using optimum geometry design method. The design method is based on a contact analysis between slider and vibrator, finite element method and genetic algorithms. The designed vibrator is manufactured and the characteristics of the motor are measured. As a result, measured natural frequencies of the vibrator agree well with the calculated ones. The maximum unloaded velocity and maximum thrust are 300 mm/s and 1.96N at the driving voltage to be 30V and the pre-load to be 4.58N, which are larger than those for previously developed linear ultrasonic motors.

Two methods are proposed for grasping object with unknown weight and the friction coefficient by robot hands in recent years. First method is to detect partial incipient slip region at the contact surface. Another one is to detect the friction coefficient between robot hands and object. The latter method have demerit that needs entire slippage of an object. In the present study, new method is proposed for detecting a friction coefficient between an object and a curved surface elastic finger only by indenting the finger into the object. First, a contact condition between a plate and a elastic finger having curbed surface is calculated using finite element analysis. The deformation of the elastic finger, and strain distribution inside the elastic finger are calculated for different friction coefficients between finger and plate. Results show that strain distribution inside the finger differs when the friction coefficient differs. Experimental results show similar tendency to calculation. From these results, the method is confined that friction coefficient can be measured by elastic finger having curved surface.

マスタ・スレーブシステムにおける従来のバイラテラル制御方式は, 繊細で臨場感のある操作を可能にするが, 力覚を提示することに伴う装置の大型化や制御系の複雑化の問題は, 制御を実現する際に大きな障害となる。そこで本稿では, 超音波モータとクラッチおよび弾性要素を用いた新たな制御手法の提案を行い, その有用性を確認する。この手法はスレーブが対象物に接触する前後で位置制御と力制御を切り換えることで, 簡便な装置と単純な制御系によって, オペレータに力覚提示を行なう。

本研究では従来の問題点を解決できるマスタハンドを開発した。本マスタハンドは3指型であり, 12自由度を有する。親指, 人差指, 中指それぞれの指先位置と姿勢の計測が可能であり, 指先への力覚を提示できる。本マスタハンドは指先位置と指先への力覚提示の両方を, 1つのリンク機構によって実現できる。力覚提示には弾性要素を用いた新しい手法を用いている。リンク機構の軸をそのまま弾性要素として用いることでこの手法を実現し, 装置も小型化している。また, 本マスタハンドを用いた心理物理実験を行い, その有用性を確かめた。

Ultrasonic motors have large and non-linear parameter space in geometry design. So it is difficult to optimize the geometry of the vibrator. In the present study, a new geometric design method for designing a linear ultrasonic motor is proposed. It is based on a contact analysis between slider and vibrator, finite element method and genetic algorithms. As a fitness function, only an output power of the vibrator obtained by contact analysis is evaluated. In this process, design parameters concerned with driving characteristics such as natural frequencies, amplitude of vibration, direction of displacement at contact points, arrangement of PZTs and factor of electro-mechanical transmission are taken into account. The proposed method is applied to a design problem in which designer might have difficulty in estimating the ideal condition of design parameters. Results of analysis show that the geometry of the vibrator having high output power is designed.

A multi-DOF ultrasonic motor we developed can generate a multi-DOF rotation of a spherical rotor using three natural vibrations of a bar-shaped stator. However, the driving state of rotor has not been estimated when the three natural vibrations are voluntarily combined. In this study, a numerical simulation method for obtaining driving characteristics of the multi-DOF ultrasonic motor is proposed. First, the contact area and elasticity between the rotor and stator are modeled using nodes and linear springs, respectively. Then, a rotational axis is estimated considering frictional forces between the rotor and stator. Next, a rotational speed and an efficiency of the motor around the estimated rotational axis are calculated. Using the proposed method, the driving state of rotor is clarified. An appropriateness of the proposed simulation method is confirmed by comparing the calculated driving characteristics with the measured ones.

Stators for the formerly developed multi-degree-of-freedom ultrasonic motors are not small enough compared with their rotors. In this study, a new type of multi-degree-of-freedom ultrasonic motor, whose stator is relatively small, is developed. First, the stator is designed in detail using a finite element analysis. An outline of the stator is square plate, which has four projections to be in contact with a spherical rotor. The rotor rotates around three perpendicular axes using three natural vibrations of the stator. Second, the designed stator is actually produced, and motion tests of the rotor are conducted. As a result, it is confirmed that the multi-degree-of-freedom motion of the rotor is experimentally produced.

筆者らはこれまでに, 単一振動子によって球状回転子を互いに直交する3軸周りに回転駆動させることができる多自由度超音波モータを開発した。本講演では, 本超音波モータを腹腔鏡下手術支援ロボットへ応用し, その有効性を示す。初めに, 手術支援ロボットへの応用のために本超音波モータの駆動特性向上と多自由度位置制御実験を行った。次に, 本超音波モータを用いて, 複雑な動作が発生できる多自由度鉗子を製作したので報告する。