Data-driven iterative tuning based active disturbance rejection control for FOPTD model.

Active Disturbance Rejection Control (ADRC) emerges as a promising control method that can effectively handle uncertainties and disturbances. However, many model-based ADRC tuning methods turn laborious to achieve satisfactory control performance, when the critical process parameters are difficult to accurately obtain, especially the time delay information. To this end, this paper aims to propose a data-driven iterative tuning method for time-delayed ADRC (TD-ADRC). Based on parameter scaling technique, the quantitative correlation among control performance, robustness and normalized controller parameters are investigated. It is then used to design robust nominal controller. Then, based on the TD-ADRC inner-loop equivalent structure, an iterative feedback tuning (IFT) method is proposed to optimally obtain the nominal first order plus time delay (FOPTD) process model. Its unbiasedness and convergence are also described. With the empirical relations and the IFT stochastic approximation algorithm, a data-driven iterative tuning method for TA-ADRC is proposed, which allows a reasonable trade-off between system performance and robustness. Simulation results validate the efficacy of the proposed method, and a water-tank control experiment depicts a promising prospect in control practice.

[Check ligament suspension for correction of congenital severe blepharoptosis].

OBJECTIVE: To evaluate the clinical result of check ligament suspension for correction of congenital severe blepharoptosis. METHODS: Since Jan. 2010 to Nov. 2010, 15 eyes in 15 cases with congenital severe blepharoptosis were treated with the check ligament suspension. Palpebral aponeurosis was exposure by opening fascia palpebral during blepharoplasty. Palpebral aponeurosis was cut off about 5 mm above the tarsus. The check ligament was seen in the intermuscular space between the segment of levator and the anterior one third of superior rectus attached to the conjunctival fornix. Congenital blepharoptosis could be corrected by suturing the check ligament and levator palpebrae superior to the upper margin of tarsal plate with 3-0 silk thread. Double eyelid plasty was carried out in the end. RESULTS: The follow-up period was 3-11 months with good cosmetic result. All the cases could close their eyes in 15 to 30 days with no complication. CONCLUSIONS: In conclusion, this technique is quite successful in raising the level of the upper eyelid in severe congenital blepharoptosis. The check ligament moves in a similar direction as the natural movement of levator muscle, so both the postoperative static and dynamic appearance of the upper lid is more natural.