To enhance robustness to model uncertainty and to attenuate disturbance and sensor noise, the design of the stabilizing controller is formulated as a problem of the mixed H2/H∞ control, which is then solved using the linear matrix inequality (LMI) approach.
As discussed previously, e.g. by Davydov et al. 6, the concept of resilience entails on one hand a process of sustainability that prevents and attenuates disturbance of mental health and wellbeing after exposure to severe adversity, and on the other hand a process of rapid recovery from mental health disturbance following exposure to adversity.
Based on the rationale behind cascade control, the secondary controller is designed based on disturbance rejection to quickly attenuate disturbances.
DFC can be added to existing controllers as an additional control loop, to attenuate disturbances and model uncertainties.
A Hybrid Active Noise Control (HANC) system is used to attenuate disturbances in a scenario where a portion of noise is captured by reference sensors.
This approach can guarantee that the closed-loop control systems is asymptotically stable and the H-infinite norm of the transfer function from the disturbance to the output of a controlled system is less than a given constant to attenuate disturbances.
A continuous control input is used to attenuate disturbances and force the plant to follow a reference trajectory, whereas the operation point of the plant is adjusted by an event-based component of the controller, determining a discrete-valued input signal.
By constructing a smooth dead-zone inverse and applying the backstepping recursive design technique, a robust adaptive backstepping controller is proposed, in which adaptive control law is synthesized to handle parametric uncertainties and a novel robust control law to attenuate disturbances.
The proposed control design method is applied in the feedback servo loop design for a lead-zirconate-titanate (PZT) micro-actuator in hard disk drives (HDDs) to attenuate disturbances at 650 Hz and 2 kHz and also minimize the positioning error such that the system positioning accuracy is enhanced ultimately.
Briefly, for a given system, one can calculate a frequency-dependent function S - the sensitivity function - that captures the ability of feedback control to attenuate disturbances of different frequencies (see Box 1).
The objective of designing controllers is to guarantee the asymptotic stability of closed-loop systems and attenuate disturbance from earthquake excitation.
