Today's automobiles are full of controllers, and many man-hours are spent in optimizing their control parameters. This study was aimed at reducing the man-hour requirement. When a controller is embedded in a product, engineers have been taught to optimize the product exclusive of the controller. Although more and more modern products cannot work without feedback control, quality engineering has never been applied to optimize feedback control itself. In this study, feedback colltrol was optimized by applying quality engineering with dynamic characteristics, using time history data as a noise factor and variation of the target value as a signal. Since optimizing a simple PID control of the type often found in textbooks failed to provide adequate stability and response, more complex logic was employed and the number of control factors was increased to 16. Despite large interaction effects, the main factor effects were identified and conditions providing good stability and response were found.

A small prototype running wheel was built for use in drug development, to measure drug-induced changes in the athletic ability of a small animal. The rotational function of the device was optimized by using a tachometer-generator to measure its rotational speed. The optimized device was then used to measure the athletic ability of a hamster by measuring the rotational speed when the hamster was fed and when its intake of food was decreased. Changes in rotational speed over time were obtained as changes in pattern distances by use of the RT method. A clear difference between the two conditions was detected,leading to the conclusion that this device is effective for evaluation of the athletic ability of an animal.

Coating materials degrade in ways such as yellowing and whitening through the effects of heat, ultraviolet radiation, water, etc. As the degradation seen in coating materials is caused by a complex se.ries of external factors, it is difficult to examine the individual effect of each external factor. In the product development stage, it is common to evaluate color change after long-term exposure in the open air, exposure to ultraviolet radiation and water for several months in an accelerated weathering machine, or immersion in several types of chemicals,but these procedures take a very long time. In this study, we used phototransmittance to evaluate the color change of a coating base made by mixing a polymer and additives. By also taking the environment in which the coating would be used into consideration and evaluating several factors at a time, we were able to reduce the evaluation time greatly.

Test conditions for evaluating the functionality of additives for sealants used for IC packaging were examined. New test conditions were established by use of a simple test piece, focusing on corrosion and increased resistance of wiring in the initial stages of degradation. Conventional test methods required repetitive measurement of 10 to 20 samples and took several hundred hours, but the new test conditions require essentially no repetition and the sealant was evaluated accurately in one tenth of the time required previously. The new conditions were used to develop an additive with high functionality. In an evaluation by a sealant manufacturer, the additive received a top quality rating.

As Japanese companies now commonly manufacture a wide variety of products in small lots, they frequently change the layouts of their factories. The paths of the automated guided vehicles (AGVs) that cruise the factory floors have to be changed accordingly, but it is difficult to change these paths flexibly when existing magnetic or optical vehicle guiding systems are used. However, moving AGVs play music for safety purposes. This study proposes a system that uses the music as a sound source for detecting vehicle position and guides the AGV using an external controller. In an attempt to develop technology for detecting the position of a sound source in a noisy factory environment, we used the parameter design techniques of quality engineering to optimize the characteristics of the emitted sound as well as methods of recording and processing the sound signals.

The objective lens actuator of an optical disk system tilts by varying amounts during operation because of non-uniform component parts, non-uniform assembly,environmental variations, and other such noise factors. Since tilt of the objective lens causes significant deterioration in the performance of the optical disk system, the amount of tilt during operation must be kept within specified limits. Conventional approaches to this problem, such as tighter part tolerances and assembly tolerances, lead to increased cost. A better approach is to design the actuator in full consideration of the variations that may occur in the field,but the more noise factors there are to consider, the longer it takes to work out the design. When simulation ahd quality engineering are combined, a more efficient design method can be obtained and a robust design in which a large number of noise factors are taken into consideration becomes possible. In the present robust design study, the noise factors were assigned to an L₁₂₈ orthogonal array and control factors were assigned to an L₃₆ orthogonal array. The resulting design improved the functionality of the lens actuator with respect to variable factors in the field, and the amount of tilt during operation was reduced.