Hirokazu Osaki

A method for assembly line balancing with more than one worker in each station

The typical assembly line is serial with no paralleling of work elements and work stations allowed. The series assumption restricts the least cycle time to be the maximum work element time, thus limiting the production rate. An alternative way to increase the production rate (hence lowering the cycle time) is by assigning multiple workers to one work station. In this paper we propose the parallel assignment method (PAM) for achieving a higher production rate. In the first phase of PAM the work elements are assigned to work stations under the multi-stage upper time limits. But as two or more workers are assigned to one station, the operation time of each worker is longer in proportion to the number of workers at the station. Therefore, in the second phase of PAM work elements are assigned to the workers in each station so that each of the workers may perform shorter work elements where the work element is a minimum rational indivisible work item. Practical problems which cannot he solved by serial line bal...

Age-related decline in color perception and difficulties with daily activities–measurement, questionnaire, optical and computer-graphics simulation studies

Abstract In aging societies, the age-related decline in visual ability is a particularly important problem. To identify problems in daily living caused by this decline in visual ability, we simulated vision in the elderly using yellowed lenses. A questionnaire study was then conducted to investigate the population and age group that has visual deficits about issues identified in the optical study. Subjective responses related to yellowing in vision became prominent in people over 75 years old. A color judgment experiment was carried out using subjects aged 80 or older. Confusing color combinations are; yellow/white, blue/green, dark blue/black and purple/dark red. Based on this color confusion data, we used computer graphics to simulate vision in the elderly. Simulated views of public signs are shown. Relevance to industry This study shows what colors tend to be confused by the elderly and provides essential data for developing products for older adults. Color combinations on interfaces such as switches, indicators and displays have to be considered carefully. Optical and computer-graphics simulations of the yellowed vision of the elderly based on color tests are powerful tools for improvement through experience.

Independence of older adults in performing instrumental activities of daily living (IADLs) and the relation of this performance to visual abilities

A questionnaire study was undertaken of more than 2800 elderly people aged 60 years and over and living at home, to investigate the relationship between their performance of some instrumental activities of daily living (IADLs) and their visual abilities. The IADL measured the ability of elderly participants to pick up coins, manage monthly financial matters, use the telephone and take medication as recommended. Visual abilities were assessed by means of each subjects answers to questions relating to resolution, focus, adaptation to bright or to dim lighting, dynamic acuity, distance perception and colour vision. The types of visual functions that, together with age and gender, contribute to determining the level of independence in the performance of IADL activities were identified using logistic regression analysis. The results indicated that elderly participants who had problems with either distance perception or yellowish vision also tended to have difficulties in picking up coins, using the telephone and taking medication as recommended. In addition, problems with adaptation and dynamic acuity were associated with difficulty in managing monthly financial matters. From an analysis of all subjects, distance perception was the significant factor that determined whether an elderly subject could pick up coins or use a telephone unaided. Yellowish vision was also significantly associated with a need for assistance or with an inability to manage monthly financial matters, use the telephone or take medication as recommended.

The surgeon's technical skill in suturing : an analysis of the actual suture tracks

Ideal suturing was defined as advancing a needle along its curvature (needle circle) to minimize tissue trauma, while placing the suture with its intended span and tissue bite in the expected place. Actual suture tracks were analyzed to find the keys to produce such suturing. Correspondence of those tracks to the ideal track was then determined by the span, the initial needle angle (IA) into the tissue, and the center of the needle circle. Eight surgeons with 4–7 years of experience produced 22 ideal sutures in two types of tissue simulants: The entrance and exit points of the needle were level in flat suturing, while the entrance point was slanted 45 degrees for slant suturing. The correspondence was better with slant suturing than flat suturing (P<0.01). The IA in flat suturing was 49.0±2.0 (mean±SE) degrees versus 33.0 for ideal suturing (P<0.01), while that in slant suturing was 35.5±1.9 (P: ns). In conclusion, the IA was the key to good results, and was optimized in slant suturing, which was instinctively utilized in practice by using forceps. The forceps avoided a derangement of suturing stemming from the configuration of the needle employed and from the range of motion of the surgeons arm (human engineering), while satisfying the surgeons inclination to take a large IA.

The Flicker Control Chart Method

The purpose of this paper is to outline a simple method of checking the variation of critical flicker fusion frequency (CFF) in working hours. It has been named the flicker control chart method, and consists of two parts. One involves the charting of CFF itself, the other the charting of CFF range. This method is applied to the CFF of bus drivers. It is found that CFF can be checked easily every day, and that factors which strongly influence its variation can be identified.

An approach to the automation of the assembly of flexible belt-shaped objects

A robot system was developed for the assembly of flexible belt-shaped objects, and the assembly procedures employed by workers in using it were analysed. A multi-fingered hand was developed to hold the objects at several points, and to move them into the proper position for attachment to a part. In addition, an image processing method that can recognize the gripping positions on source objects and conditions after the source objects are attached is proposed.

An Inspection Method for Three-Dimensional Surface and Volume of Minute Subject by Image Processing

In this paper, we propose an inspection system of subject with three dimensional surface and volume by image processing using the distribution of brightness and section curves. The distribution of brightness on image depends on the inclination of subjects surface from an optical axis of the camera unit. Therefore, it is possible to inspect the three dimensional surface based on it. The sample is classified into some patterns by the visual inspection of worker. Next, the brightness pattern of a sample is measured, and its standard index is calculated. The weighting coefficient is determined based on the standard deviation of width of bright area on the sample. The volume of inspection subject is measured using a line laser device, and a control chart method is applied to maintain the quality of shape and volume of subjects through the production line. The proposed method is applied to soldering on electric device, and weight of lead in soldering is estimated from the measured volume.

A study of estimation method for mouth position using image processing technique

Abstract In this paper, we propose the method of estimating the coordination of the mouth position with the head movement. This is done by using image processing technology. The mouth position will be able to use the human interface to control the meal support robot. The estimation method for the coordinate of the mouth position is as follows. Firstly, we extract the area of the mouth from the time series images by two video cameras. Secondly, we describe the method to estimate the head movement from the coordinate of the mouth center. Finally, we calculate the 3D coordinate of the mouth center to apply to some parallel images.

Recognition Method by Image Processing Using 3D CAD Figure Information.

We propose a method for recognizing a subject from the image taken by a CCD camera and comparing with the CAD figure. The three-dimensional CAD figure is transformed into a two-dimensional figure in which some color is added inside the contour. The transformed figure is used as the input of image processing. The two-dimensional CAD figure and an image of the recognized subject from one camera are represented by characteristics, that is, the center of gravity, contour, the distance between them, and FFT. The figure of the subject is estimated from these characteristics by comparing with the database of CAD figure.

Development of a Scooping up Robot System.

In this paper we develop a robot system which scoops up food and helps the aged and the handicapped to eat. We classify the objects (food) into three types : liquid, jelly and grains. By using a video camera we measure how a human being scoops the above-mentioned types of objects with a spoon. Next, the motion of the spoon and its rotating angle are formulated. The results are recorded in a data base and used to determine the motion of a robotic arm. Finally, we perform an applicative experiment to determine the amount of food which can be scooped at one time and where to insert the spoon in the objects. The results of the experiment are input to a controller, and the scooping robot system is developed.