In this note, we introduce the integral term of system outputs into an output feedback controller for sampled-data linear systems with unknown disturbances. The proposed method does not use any observer and can prevent the high gain actions in control inputs. Provided the variation of the disturbance in the two consecutive sampling instances is not changed significantly, it is shown that system states and system outputs are finally constrained in small bounded regions, respectively. Simulation results support the theoretical developments.

For time-delay systems with mismatched disturbances and uncertainties, this paper developed an integral sliding mode control algorithm using output information only to stabilize the system. An integral sliding surface is comprised of output vectors and an auxiliary full-order compensator. The proposed output feedback sliding mode controller can satisfy the reaching and sliding condition and maintain the system on the sliding surface from the initial moment. When the specific linear matrix inequality has a solution, our method can guarantee the stability of the closed-loop system and satisfy the property of disturbance attenuation. Moreover, the design parameters of the controller and compensator can be simultaneously determined by the solution to the linear matrix inequality. Finally, a numerical example illustrated the applicability of the proposed scheme.