Robust Image-Based Visual Servo Control of an Uncertain Missile Airframe

A nonlinear vision-based guidance law is presented for a missile-target scenario in the presence of model uncertainty and unknown target evasive maneuvers. To ease the readability of this thesis, detailed explanations of any relevant mathematical tools are provided, including stability definitions, the procedure of Lyapunov-based stability analysis, sliding mode control fundamentals, basics on visual servo control, and other basic nonlinear control tools. To develop the vision-based guidance law, projective geometric relationships are utilized to combine the image kinematics with the missile dynamics in an integrated visual dynamic system. The guidance law is designed using an image-based visual servo control method in conjunction with a sliding-mode control strategy, which is shown to achieve asymptotic target interception in the presence of the aforementioned uncertainties. A Lyapunov-based stability analysis is presented to prove the theoretical result, and numerical simulation results are provided to demonstrate the performance of the proposed robust controller for both stationary and non-stationary targets

Transoral endoscopic parathyroidectomy vestibular approach (TOEPVA) for primary hyperparathyroidism: Turkey's experience

Aim Parathyroid surgery has witnessed a significant evolution with the introduction of more efficacious preoperative localization imaging techniques and the use of rapid intraoperative parathormone assays. Parathyroid surgery can now be performed with the minimum of invasion. Through the adaptation of the transoral endoscopic thyroidectomy vestibular approach (TOETVA), the technique has now been adopted for parathyroid surgery, known as the transoral endoscopic parathyroidectomy vestibular approach (TOEPVA). We present here the initial experiences of 11 centers carrying out TOEPVA surgery in Turkey. Materials and methods Participating in the study were 11 centers, all of which were tertiary care institutions carrying out endocrine surgery. A retrospective review was made of 35 primary hyperparathyroidism patients who underwent the TOEPVA procedure between July 2017 and January 2020. Results Of the total 35 patients, 32 patients underwent the TOEPVA procedure successfully. All patients but one were female, and the mean age was 47.2 (20-73) years. According to localization studies, 18 of the lesions were lower left, 12 were lower right, 3 were upper right and 2 were upper left. The mean operative time was 116 (30-225) min, and three cases were converted to an open procedure. Simultaneous thyroidectomy was performed in seven cases. The average PTH level dropped to normal within 20 min. after the resection in all cases. The complication rate was 19% (ecchymosis, subcutaneous emphysema, nasal bleeding, surgical site infection and seroma). There were neither recurrent nerve palsies, nor mental nerve root or branch injuries. The average hospital stay was 1 day. No persistence was documented on follow up. Conclusion TOEPVA is a "hidden scar" parathyroidectomy procedure that can be safely performed on parathyroid adenomas, in cases that have scar-related concerns. Having its own procedure-related complications, the procedure provides satisfactory objective results, particularly in centers experienced in endoscopic and endocrine surgery