Actuators for Motion Control: Fine Actuator Force Control for Electric Injection Molding Machines

摘要

Currently, most plastic products are manufactured using injection molding machines, where the product quality largely depends on the injection force. In a typical injection molding machines force control system, force information from the machine environment is obtained by a force sensor. However, these sensors have a few disadvantages in terms of signal noise, sensor cost, and narrow bandwidth, and thus a sensorless force detection method is desirable. The use of a reaction force observer, based on the two-inertia resonant model, has been proposed, but this method suffers from some estimation errors due to the influence of nonlinear characteristics in the holding process and the screw back-pressure process. This article proposes a new injection force estimation method based on a high-order reaction force observer (HORFO) with Coulomb friction compensation, which is not significantly influenced by the nonlinear friction phenomenon. Moreover, this article evaluates the possibility and versatility of a sensorless force control system using the proposed HORFO with Coulomb friction compensation.