Comparison of Continuous and Discrete PI Control on Clamp Positioning of an Industrial Robot

This paper presents a comparison between a continuous and a discrete PI control, applied on an industrial robot. The industrial robot is used in a hot rolling process and is designed to precisely catch and unload billets from inside a rotary hearth furnace. The process to be controlled is a positioning one, meaning that the clamp of the industrial robot must reach an exact position, that of the billet to be unloaded. Both a continuous and a discrete version of PI controllers are implemented using computer software, and the control structures are compared at different step input signals to determine if a discrete form of the controller is any different than the continuous one and if it can be applicable on the real process. Multiple discussions are made, such as load disturbance rejection and output performances improvement.