Kazuya Okawa

Path planning of wheel loader type robot for scooping and loading operation by genetic algorithm

There is a demand of mining automation by heavy equipment in an open mine. Authors aim to automization of motion for wheel loader in scooping and loading operation. In this paper, we applied the optimization method by Genetic Algorithm to the path planning for the wheel loader on scooping and loading operation. We showed the quasi-optimized path and demonstrated by the miniature wheel loader robot.

High efficiency skill training of lathe boring operations by a virtual reality environment

In order to fabricate a machine part manually using a machine tool, special skills for its safe operation are necessary. Virtual reality (VR) technology is well known to provide novice operators with a safe and cost-effective performance training environment. Although an ordinary VR training environment simulates the actual environment as accurately as possible, more effective training environments can be built by taking advantage of the property that virtual reality can simulate even unrealistic situations. This paper deals with a high efficiency training of the boring skill using a manual lathe and a slender cutting tool where novice operators easily break the cutting tool because of its low stiffness. The research hypothesis is that if a stiff cutting tool is given in the beginning of the training and its stiffness is lowered gradually, novice operators will master the skill easily. The hypothesis was verified through trial tasks with novice operators. In conclusion, the proposed training method can reduce the amount of trial tasks and the fatigue of the operators.

Motion control for vehicle with unknown operating properties-on-line data acquisition and motion planning

This paper describes a sequence of methods for controlling the vehicle with unknown operating properties, such as an air cushion vehicle, a submarine and an airship. We took up Air Cushion Vehicle (ACV) as an example of such a vehicle, and studied its motion planning based on acquired data. ACV in this paper has three simple unit motions (left-turn, right-turn and an advance), and can execute one of the unit motions optionally. After the execution, ACV measures its own position by itself and acquires data of how it moved in the real environment. Then it plans the motion that arrives at a target position using the acquired data. In this paper, we propose a sequence of these approaches and show the effectiveness of them by experiments.

Development of a wireless electrical resistance detector for real-time particle volume fraction measurement in centrifuges

A wireless electrical resistance detector has been developed to measure the real-time particle volume fraction in a high speed centrifuge. The detector is composed of an AC (alternating current) generation device, a measurement circuit and a wireless transmission device. The square wave alternating AC signal is generated from batteries. To test the measurement accuracy, the developed detector is attached around a lab-scale centrifuge with a limited rotational velocity. With the developed detector, the real-time volume fraction of polymer pellets with an elliptic cylindrical shape in sodium chloride solution is measured at different positions under various rotational velocities and particle supply rates. The measurement results are compared with a numerical simulation by the volume-of-fluid (VOF) method for validation. A parabola-shaped phase boundary between particle and sodium chloride solution is detected. As the rotational velocity increases, more and more particles are pushed outward and raised along the cylindrical vessel because of the increased centrifugal force, which causes an increase of the particle volume fraction near the wall. Moreover, as the initial particle loading height increases, the parabola-shaped phase boundary shifts upward and increases the particle volume fraction near the wall.

Proposal of Link Composition for Rotational Parallel Mechanism with Pin Joints and Investigation of Movable Area

パラレルメカニズムは,ベースとエンドエフェクタとの間の 機械構造に複数の動力伝達経路を持った機構であり,産業用ロ ボットなど多くのマニピュレータに使われているシリアルメカ ニズムとは対照的な性質を持つ.パラレルメカニズムは,シリ アルメカニズムに比べて可動領域が狭いなどの問題はあるが, 特定の駆動装置に負荷が集中することが少ないためトルクの小 さい駆動装置でもシステム全体として大きな力を発生できる点 や,トラス構造を採ることができるためメカニズム全体として の剛性が向上する点などの利点がある.このため,パラレルメカ ニズムの研究が多く行われており [1]~[6],大型フライトシミュ レータやアミューズメント機器の揺動装置など,重量物を積載 し可動させる用途を中心に実用化されている. パラレルメカニズムは,駆動方式の違いによって,伸縮型 [1] [2] [7] [8],回転型 [11],直動型 [12],ワイヤ型 [13]の大きく 4種類に分けられるが,本論文では回転型パラレルメカニズム を対象とする.6自由度回転型パラレルメカニズムでは,Fig. 1 に示すように,ベース部にモータが配置され,5自由度の受動 関節を介してエンドエフェクタに接続されていることが多い. Fig. 1の連結連鎖を 6組並列的に配置し,ベース部に配置した

Evaluation of Vibration Finished Surfaces Using Image Processing Method

Vibration finishing which is often applied to the metal surfaces recently is the finishing method using a disk-type finishing tool with movements of rotational and orbital motion [1]. However, an application of this finishing method and an evaluation of finished surfaces require skills and sensory examinations. This is because the relations between finishing conditions and quality of finished surfaces are not clear. In recent years, image processing methods for evaluating finished surface roughness and texture analysis were proposed [2 - 5]. However, quantitative evaluation has not been fully done.

Processing Characteristics of Structured Lapping Films under Grinding Load Control

Pyramidal structured lapping film, which has minute pyramidal structures formed by abrasive grains and adhesives on polyester films, is newly developed finishing tool[1,2]. It is said that the tool has eminent grinding characteristics, mainly, good finished surface quality because chips generated during grinding process can escape into spaces between pyramidal structures, and high grinding efficiency because new abrasive grains come out from inside of the pyramidal structures during grinding process. However, finishing characteristics of this grinding tool have not yet been fully explained.　In this research, the grinding experiments were conducted, focusing on the efficiency of grinding. The grinding forces were measured to examine the state of the surface of the tool. In addition, to improve the grinding efficiency using this tool, a method for changing the grinding load continuously while processing was used. This method was intended to enhance the effective chip generation and new abrasive grain emergence. As a result, stock removal of the workpiece was increased more than when the grinding load was kept constant. Moreover, using scanning electron microscope, this new grinding tool surface was observed, and its effectiveness was examined.

Evaluation of Sharpness of Dental Scalers Using Optical Reflection of Blades Rotated in Two Directions

Dentists and dental hygienists remove dental calculus using a cutting tool called dental scaler. The evaluation of sharpness of dental scalers requires skill which depends on sensory examination. The aim of this research is to evaluate the sharpness of scalers objectively by estimating optical reflection images of blades rotated in two directions. For taking photos of blades at various angles using CCD camera, the scaler to be inspected was fixed on a turn table driven by a stepping motor. In this research, the angle of a scaler fixture on the turn table was also changed by a RC servo motor. As a result, the optical reflection patterns of the cutting edge could be obtained more precisely than before. Next, an image processing method was examined for calculating the area and the length of optical reflection patterns of the cutting edge from the photos obtained from various angles. And the relation between these values and the sensory evaluated values was examined using multiple regression analysis. As a result, it was confirmed that this method can evaluate the sharpness of scalers objectively and precisely. And it was also confirmed that the angle of the scaler fixture is also an important factor for this evaluation method as well as the angle of the scaler.