Fuzzy logic controller for injection ram velocity

Injection ram velocity has strong influences on the quality molded parts in such areas as shrinkage, warpage, and impact strength. An injection molding machine operates under such different operating conditions as different molds and materials. This causes the velocity dynamics to vary significantly and consequently results in poor control performance for a typical PI controller. This paper discusses a computer control system for injection ram velocity using a real-time fuzzy logic controller (FLC). The rules of FLC are optimized by analyzing the phase plane characteristics. The membership functions are determined based on the 2^k factorial design technique. The experimental results reveal that the fuzzy logic controller (FLC) together with a feedforward control has superior performance over the conventional PI controller in the response speed, set-point tracking ability, and robustness.