Control Area Expansion Using Null Space Vector Injection Under Current Limit in Magnetic Manipulation System

This paper proposes a current reference adjustment method of multiple coil magnetic manipulation system that controls a magnetized object, so-called micro-robot. This method adjusts the current references exceeding the current rating to be in the current rating by injecting a null space current vector based on the actuation matrix characteristic. This method expands the area in which a micro-robot can operate without decreasing given control command. Therefore, the proposed method maximizes micro-robot control performance in current limit situation. The current reference for each coil is calculated on PC and controlled by eight independent full bridge inverters. Advantages of the proposed method are confirmed by control area analysis and the effectiveness is verified by experimental results.