Currently, most plastic products are manufactured by using injection molding machines. The quality of plastic products depends largely on the injection force. In a typical force control system of an injection molding machine, force information from the machine environment is obtained by a force sensor. However, force sensors have a few disadvantages in terms of signal noise, sensor cost and narrow bandwidth. So, a sensor-less force detection method is desirable for electric injection molding machines. We have proposed the use of a reaction force observer based on the two-inertia resonant model. However, this method has some estimated error because of the influence of nonlinear characteristics of the holding process and the screw back-pressure process. This paper proposes a new injection force estimation method based on a proposed high-order reaction force observer (HORFO), which is not influenced by the nonlinear friction phenomenon significantly. This paper evaluates the possibility and versatility of the proposed sensor-less force control system by using proposed HORFO through experiments.
展开▼
