Accurate Trajectory Tracking for a 3D-Plotter Using Optimal Preview Control and Unknown Input Observer

This paper presents the design of a control strategy for the tracking control problem of a three-axis cartesian-robot based on optimal preview control, where the current and future desired position of the robot are used to calculate the control signal which allows accurate tracking of the desired trajectory. In order to give robustness to external disturbances, an observer capable to estimate any state vector for linear systems with unknown inputs is designed. The effectiveness of the proposed control strategy is verified by simulation for linear and nonlinear trajectories, where preview control improves the tracking accuracy. Likewise, the effectiveness of the unknown input observer is verified by applying a disturbance as an additional input to the system.