Abstract:  In this paper, we propose a control law in a linear active disturbance rejection control (LADRC) for removal of ramp disturbance. We use plant inverse characteristics as a control law. We calculate the steady-state error of the conventional method and that of the proposed method using the final-value theorem. In a conventional and a proposed LADRC, each plant output has no steady-state error when a step signal is assumed as a plant input-side disturbance. However, in a conventional LADRC, the plant output has a steady-state error when a ramp signal is assumed as a plant input-side disturbance. On the other hand, in a proposed method, the plant output has no steady-state error. In comparison with a conventional method, the proposed method has almost the same control performance for a plant with a modeling error.

Keywords: Active disturbance rejection control. Extended state observer. Steady-state error. Plant inverse characteristics.