System Identification of Hydraulic Actuators is critical for analyzing their performance and designing a suitable Control System. Hydraulic actuators are extensively used in many applications, ranging from flight simulators, robotics, orthopaedic surgery, material testing, construction and many other industrial types of machinery. In the aviation industry, hydraulic actuators are currently being used in full flight simulators used for controlling the position and orientation of the motion platform. Every actuator has its own characteristics, therefore, the choice of excitation signals for System Identification must take into account the dynamics of the actuator under consideration. This work proposes the selection of excitation signals based on bandwidth of the hydraulic actuator. Validation of the proposed selection is done by performing system identification, obtaining a mathematical model and comparing it with a nonlinear hydraulic actuator model designed in Simscape. After validation, a nonlinear PID control has been tuned on the identified model and tested on the nonlinear model. Extensive simulations have been run and results show accurate mathematical modelling, as well as precise control has been achieved through the proposed methodology. INDEX TERMS Black-box model, controller design, electro-hydraulic actuator (EHA), flight simulator, NPID, hydraulic actuator, system identification.

Objective: To compare the negative appendectomy in the females of reproductive and non-reproductive age groups. Study Design: Cross-sectional study. Place and Duration of Study: Department of Pathology, Diagnostic and Research Laboratory, Liaquat University of Medical and Health Sciences, Hyderabad, Pakistan, from January 2018 to December 2019. Methodology: A total of 1126 appendectomy specimens were enrolled irrespective of age and gender. The biodata of patients was retrieved from the database. Statistical analysis was done using SPSS version 22. Results: Out of total 1126 reported cases, 787 (69.9%) were males and 339 (30.1%) were females. The mean age was calculated to be 24.43 ± 12.42 years ranging from 2-94 years. Histopathological examination revealed cases of acute appendicitis 374 (33.2%), acute appendicitis with peri-appendicitis 478 (42.5%), fibrous obliteration 28 (2.5%) and parasitic infestation 7 (0.6%). Overall negative appendectomies were 219 (19.4%) and were prominent in females 100 (29.5%) than males 119 (15.1%). Also it was higher in females of reproductive age group 77 (30.4%) than in non-reproductive age group 23 (27.9%). Conclusion: In our study negative appendectomy in females of reproductive age groups was found to be higher than expected. Clinical scoring systems, biochemical markers, imaging modalities, and second opinion from other specialties like internal medicine, gynae and obstetric have been introduced to substantiate the diagnosis of acute appendicitis and thereby decreases the negative appendectomy.

No abstract