Position Control of Servo Drive with a State Observer

The paper is dedicated to the design and comparison of properties of the positional servo drive with two control structures. PD controller and a state observer are used in both. But the presented structures differ in type of state observer. The state observer in the first control structure contains a disturbance observer with an inverse model of plant and the filters of the position and velocity signals (DO-FPID control). The order of filters in the disturbance observer and the feedback is optional. The state observer of the second structure includes an extended state observer (ESO), which also filters the position and velocity signals, but the order of filters is not optional and it is given by the structure of ESO (ESO-PID control). In addition, the setpoint feedforward is utilised in both structures. The purpose of the feedforward is to minimize the control error during continuous change of position reference. The tuning of controller parameters, state observer and feedforward is presented in the paper. The properties of the position control loop were verified through simulations.