MULTICRITERIA STEEPEST ASCENT

A simple multiresponse steepest ascent procedure has been developed by combining the standard steepest ascent method with multicriteria deci sion making. The steepest ascent method is one of the older methods in response surface methodology. It can be applied in optimization where the operability region is so large that a very complex function would be needed to fit an empirical function. With steepest ascent, local d esigns and local models in a part of the operability region are used t o find a direction where the response is improved most. Experiments pe rformed along a line in that direction will reveal the region of inter est. There the response may be fitted with a second degree equation. T he problem of multiresponse steepest ascent is that directions of impr ovement have to be combined into one direction. In general, the direct ions of improvement indicated by the individual responses are differen t and they may even be opposite. In this paper, steepest ascent has be en adapted to the use of more responses are different and they of the directions of steepest ascent to a simultaneous direction of interest. The combination is made by consideration of the obtainable improvemen ts of the responses in the response space. These improvements can be c alculated from the centre point (of the local design) response values and the response values at a fixed distance of the centre point. As an example, the method has been applied to a tablet optimization. This o ptimization problem had two responses and two independent variables.