Disturbance rejection control for Raymond mill grinding system based on disturbance observer

In the Raymond mill grinding processes, high-accuracy control for the current of Raymond mill is vital to enhance the product quality and production efficiency as well as cut down the consumption of spare parts. However, strong external disturbances, such as variations of ore hardness and ore size, always exist. It is not easy to make the current of Raymond mill constant due to these strong disturbances. Several control strategies have been proposed to control the grinding processes. However, most of them (such as PID and MPC) reject disturbances merely through feedback regulation and do not deal with the disturbances directly, which may lead to poor control performance when strong disturbances occur. To improve disturbance rejection performance, a control scheme based on PI and disturbance observer is proposed in this work. The scheme combines a feedforward compensation part based on disturbance observer and a feedback regulation part using PI. The test results illustrate that the proposed method can obtain remarkable superiority in disturbance rejection compared with PI method in the Raymond mill grinding processes.