A Low-Cost Test Bench for Underwater Thruster Identification

International audienceUnderwater vehicles are increasingly being used for the inspection of marine structures , bathymetry and underwater intervention applications. The manoeuvring performance of these vehicles is critically dependant on the quality of the thruster model which must faithfully represent the relationship between the thruster inputs and corresponding outputs. Thruster manufacturers typically provide only the essential electrical, mechanical and thrust performance characteristics, for this reason the identification of the thruster's parameters is especially important for constructing a reliable control system for the underwater vehicle. Physical testing using some form of test bench is normally used for identifying the thruster parameters. These test benches usually consist of a water tank and the thruster which is clamped to some form of instrumented reaction frame for measuring the model parameters. The cost of a test bench varies according to two major factors which are the size and the instrumentation which strongly depends on the physical quantities that we are trying to measure. In this article we will make a state of the art survey of existing test benches in order to provide a technical basis that will allow us to build a low-cost test bench. A thruster will be modelled using the resulting test bench and the outcomes will be presented at the end of this paper

Modeling and control of a Wind Energy Conversion System based on DFIG driven by a Matrix Converter

This paper presents the control study of a variable speed Wind Energy Conversion System (WECS) based on the Doubly Fed Induction Generator (DFIG). The generator is connected directly to grid by its stator and fed by a Matrix Converter (MC) at its wound rotor. The indirect vector control is adopted. The stator flux is oriented for controlling the power and current, which are regulated by PI controller via the pole placement technique, and the Venturini Modulation Method (VMM) is applied to control the MC. The performance of the whole system is verified by Matlab/Simulink simulation. Results in transient and steady-state regimes are presented to validate the effectiveness of the proposed wind conversion system. Results confirm the high performance of the control

Kidney Lesions Associated with Systemic Vasculitis: Report of 25 Cases in Morocco

In this retrospective study, we report 25 patients with renal injury caused by systemic vasculitis. These patients were hospitalized at the department of nephrology-hemodialysis in Ibn Rochd hospital from 1985 to 1998. The mean age of the patients was 36 years (range 3 to 57 years) with male predominance (68%). The clinical presentations included cutaneous purpura in 80% of the patients, arthritis in 60% and pulmonary hemorrhage in 20%. The renal injury manifested as abnormal urinary sediment in 20 of the study patients (80%), nephritic syndrome in 14 (56%), renal failure in nine (36%). Three patients (12%) had renal failure as the initial presentation followed by the other manifestations of vasculitis. The anti-neutrophil cytoplasmic antibodies (ANCA) have been checked in only six patients of whom four were positive. Henoch-Schonlein purpura was the most common clinical sign in 11 patients (44%) followed by Behcet′s disease in five (20%). The treatment was variable in type and duration but generally included corticoids alone or in combination with immunosuppressants. The prognosis of the renal injury was variable. The renal function remained stable in those with Henoch-Schonlein purpura, but was less favorable with the other etiologies with more predominance of renal failure and end-stage renal disease. This retrospective analysis of our experience is given to throw light on the pattern of vasculitis in our region