Fine sensorless force control using stribeck model for injection molding machine

Injection molding is a common method for producing various resin products. The force control system of a typical injection molding machine obtains information about the force from the environment of the machine via a force sensor. However, because a force sensor often has disadvantages such as signal noise, high cost, and narrow bandwidth, a reaction force observer has been developed for electric injection molding machines. The high-order reaction force observer (HORFO) is developed which includes a friction compensation element and uses the dither signal insertion method. However, the static frictional force and dynamic friction force have been not considered in this reaction force estimation observer, and accurate force control is difficult because of estimation error. In this paper, we propose a new friction model that takes into account the stribeck effect in order to improve the estimation error problem in force sensorless estimation. In addition the effectiveness of the proposed method is investigated in actual experiments using an injection molding machine.