Performance Of Disturbance Observer Research Articles

Delay robustness-constrained control of integrating processes with optimal tracking and quantified disturbance rejection

Regarding a general class of integrating processes subject to uncertain delays, this paper investigates a two-degree-of-freedom (2-Dof) control scheme with a proportional–derivative (PD) controller and disturbance observer (DOB). Relative delay margin is introduced as a paramount metric to evaluate the delay robustness, with which a set of novel and explicit tuning formulae for PD controller is analytically derived under the single external loop. In this individual frame, the stability boundaries associated with the governing parameters are first studied, indicating the nominal stability conditions for the 2-Dof control system. Then the optimal tracking problem is formulated and addressed with such delay robustness constraints. For the design of the internal loop, the performance of DOB will be quantified by the trade-off between the external relative delay margin and the disturbance rejection, thus retaining the original PD controller design. Besides, the stability in the nominal delay range is primarily concerned when demarcating the low-pass filter in DOB, based on which a critical time constant is obtained through exhaustive testing. Following the route of combining analytical design with quantitative adjustment, the synthetic tuning rules can provide prescribed robustness against delay uncertainty for integrating processes. Through conducting illustrative simulations and a water tank experiment, the efficiency and merit of the proposed scheme are demonstrated.

Design of a New Multi-Loop Disturbance Observer for Optical Disk Drive Systems

The disturbance observer (DOB) is known to be effective in enhancing the performance of dynamic systems in the presence of disturbances. In general, the disturbance rejection performance and robustness of DOBs depend on the order of the Q-filter, which is a low pass filter, and its time constant. In this paper, a new multi-loop DOB, improving the performance of DOB, is presented and its robust stability is proven using linear fractional transformation. It is possible to improve the sensitivity function with additional external-loop DOBs which do not significantly affect the complementary sensitivity function. The proposed new multi-loop DOB is applied to a commercial optical disk drive tracking servo system. Experimental results show that the proposed multi-loop DOB is an effective method in rejecting disturbance as well as improving the tracking performance.