Taguchi methods without Schmidt expansion are introduced here. The methods require to select unit space members that all members of the group must have same or almost same output. The average output value of the unit group and average value of each variable are subtracted from each member of signal. Using the relation between variable values and output of signals we estimate the slope β and S/N ratio η to obtain an overall estimate the true value of output of each signal member. Finally we can calculate S/N ratio of the overall prediction.

Together with the tires, suspension, and other systems, the steering system is a key system determining the driving performance of an automobile. Using recent advances in electronic control technology, automobile manufacturers and related suppliers are developing a variety of next-generation steering systems. Because these new steering systems differ greatly from conventional systems in regard to the path and method of transmission of force from the steering wheel to the tires, setting the turning torque generated when the driver turns the steering wheel presents difficult technical problems which are of considerable importance. In the pioneering development of turning torque characteristics fbr these new steering systems, a combination of simulation with parameter design was used to make the development process more efficient. As a result, target turning torque characteristics were achieved in the short time of 1.5 months. Besides greatly improving the efficiency of the pioneering development phase,this study demonstrated the effectiveness and general applicability of an optimization process combining simulation with parameter design.

Toner concentration (toner content) is one of the quantities tested to evaluate dual-component toner used for electrophotography. Measurement of toner concentration is extremely simple: water and an activating agent are used for wet separation of the toner and carrier, which are then dried, and the value is calculated from the difference between their dry weight. During the drying process, the water is replaced with methanol. Although only a small amount of methanol is used, because methanol is a dangerous and highly toxic substance, a study was made to find the most stable conditions for measurement without using methanol. In this study, the measurement conditions were optimized through use of an L18×L9 orthogonal array, resulting in the discovery of conditions for making the measurement with better accuracy than by present methods, without methanol replacement. Measurement without use of methanol also benefits the environment.

As the spindle rotation speed of machine tools has increased from several thousands to several tens of thousands of revolutions per minute, higher precision,higher rigidity, and longer life have become necessary. Previous studies focused on the lubrication and cooling system of the bearing, but fabrication of the entire spindle assembly involves considerable time and expense, so in the present study, optimization experiments were carried out by fabricating only the spindle head. This led to efficient evaluation and quick results, including results that contradicted common wisdom about oil conditions, It was also found that the unbalanced load on the head was not large enough to be suitable as a noise factor,

The object of this study was the optimization of a powder measuring instrument. An L18 orthogonal array experiment was performed. To obtain better optimization under conditions in which the true value is unknown, the S/N ratio was calculated by using several methods of quantification and analysis. A particular method was identified as a result of the analysis, and it was shown that the method of quantification is a major factor in the optimization of the measuring instrument.

A new circuit configuration was proposed for the output amplifiers that drive LCD loads in mobiIe telephones, to reduce the power consumption of the LCD driver circuits. The objective function of these output amplifiers is current amplification of an input signal, but circuit simulation of the new configuration showed an unwanted input-output voltage difference, and it was confirmed that this difference increased with increasing temperature. The output voltage determines the transmittance of an LCD, so a voltage difference has a direct effect on image quality. The temperature dependency of this difference is a quality problem that lies beyond the scope of quality assurance. Parameter design was carried out by combining circuit simulation with quality engineering to reduce the voltage difference. Performance goals were attained in the short time of about thirty hours.

In thick-film hybrid ICs, the circuit wiring is provided through formation of glaze-film wiring patterns for electrodes, resistors, and other devices on an alumina-based substrate. As a patteming evaluation method, many case studies using current-voltage characteristics have been presented so far. Those case studies used variations in process conditions as noise factors. Based on the quality engineering concept that noise consists in differenees in usage in the field, we proposed noise conditions derived from assumed usage conditions of the product after shipment, and tried these conditions out in a patterning evaluation. With suitable test patterns and deterioration conditions, optimization of the formation of thick-film hybrid IC eleetrode film patterns was achieved efficiently in a short time. Since our company procures thick-film materials from several material manufacturers, we alse studied efficient methods of evaluating those materials. The result suggested that thick-film materials could be evaluated efficiently through a comparison of wiring performance by Using functionality evaluation,