5 results on '"Flight Control Systems"'
Search Results
2. A method for specifying complex real-time systems with application to an experimental variable stability helicopter
- Author
-
Bradley, Roy
- Subjects
629.135 ,Flight control systems - Abstract
Engineering systems increasingly contain a significant element of embedded software. The specification of such systems causes problems because of the diversity of the sub-systems which they contain. For example, in modem aerospace systems a combination of mechanical, electrical, hydraulic and digital sub-systems need to function together in a safety-critical manner. The need is for a uniform means of specification which spans the whole diversity of sub-systems and which serves both to verify and to validate the functional aspects of the total system. more...
- Published
- 1992
Catalog
3. On-line identification investigation
- Author
-
Ture, M.
- Subjects
629.135 ,Flight control systems - Published
- 1992
4. Automatic Landing of a Rotary-Wing UAV in Rough Seas
- Author
-
Yang, Xilin
- Subjects
- Automatic shipboard landings : simulations, Rotary-wing unmanned aerial vehicles (RUAVs), Flight control systems, Vario helicopters
- Abstract
Rotary-wing unmanned aerial vehicles (RUAVs) have created extensive interest in the past few decades due to their unique manoeuverability and because of their suitability in a variety of flight missions ranging from traffic inspection to surveillance and reconnaissance. The ability of a RUAV to operate from a ship in the presence of adverse winds and deck motion could greatly extend its applications in both military and civilian roles. This requires the design of a flight control system to achieve safe and reliable automatic landings. Although ground-based landings in various scenarios have been investigated and some satisfactory flight test results are obtained, automatic shipboard recovery is still a dangerous and challenging task. Also, the highly coupled and inherently unstable flight dynamics of the helicopter exacerbate the difficulty in designing a flight control system which would enable the RUAV to attenuate the gust effect. This thesis makes both theoretical and technical contributions to the shipboard recovery problem of the RUAV operating in rough seas. The first main contribution involves a novel automatic landing scheme which reduces time, cost and experimental resources in the design and testing of the RUAV/ship landing system. The novelty of the proposed landing system enables the RUAV to track slow-varying mean deck height instead of instantaneous deck motion to reduce vertical oscillations. This is achieved by estimating the mean deck height through extracting dominant modes from the estimated deck displacement using the recursive Prony Analysis procedure. The second main contribution is the design of a flight control system with gust-attenuation and rapid position tracking capabilities. A feedback-feedforward controller has been devised for height stabilization in a windy environment based on the construction of an effective gust estimator. Flight tests have been conducted to verify its performance, and they demonstrate improved gust-attenuation capability in the RUAV. The proposed feedback-feedforward controller can dynamically and synchronously compensate for the gust effect. In addition, a nonlinear H1 controller has been designed for horizontal position tracking which shows rapid position tracking performance and gust-attenuation capability when gusts occur. This thesis also contains a description of technical contributions necessary for a real-time evaluation of the landing system. A high-infedlity simulation framework has been developed with the goal of minimizing the number of iterations required for theoretical analysis, simulation verification and flight validation. The real-time performance of the landing system is assessed in simulations using the C-code, which can be easily transferred to the autopilot for flight tests. All the subsystems are parameterized and can be extended to different RUAV platforms. The integration of helicopter flight dynamics, flapping dynamics, ship motion, gust effect, the flight control system and servo dynamics justifies the reliability of the simulation results. Also, practical constraints are imposed on the simulation to check the robustness of the flight control system. The feasibility of the landing procedure is confimed for the Vario helicopter using real-time ship motion data. more...
- Published
- 2011
5. The design of a hingeline electro-mechanical actuator
- Author
-
Kendrick, Kevin Stuart
- Subjects
- Aircraft control mechanisms, Flight control systems, Gear train
- Abstract
Aircraft control mechanisms, such as those that operate the flaps, ailerons, rudders, etc., are almost exclusively driven by hydraulic-based systems. Their popularity in flight control systems is not unfounded; hydraulic actuators are quite torque-dense and benefit from decades of development bringing operating performance to a high level. On the other hand the infrastructure to support this system increases weight, adds system development complexity, and reduces aircraft maintainability [Jensen et al, 2000]. Based on recent Electro-Mechanical Actuator (EMA) development and design efforts at the Robotics Research Group (RRG), a new opportunity exists to replace current hydraulic flight control systems with those powered by electricity through a national program [Tesar, 2005]. A literature review of the topic found a 30 year old effort by AiResearch to develop a similarly powered hingeline actuator with given traditional performance goals (torque capacity, redundancy, output speed, reliability). In this report,a thorough analysis is performed on each major component group to quantitatively evaluate this baseline device. Using component technologies developed at RRG, this report proposes a dual torque-summing electromechanical actuator, each with a star compound / hypocyclic combined gear train, designed to exceed the performance of the original (1976) AiResearch project. This preliminary design exercise includes a layout of the entire actuator along with an appropriate analysis of major components including bearings, gear train, motor, housing, and release mechanism. The performance of this gear train is critical to overall actuator success and fundamental analytics have already been developed in this area [Park and Tesar, 2005]. Finite Element Analysis on the gear train and housing provide early design feedback and verification of actuator performance characteristics. In particular, simulation results show the gear stiffness, load sharing, and torque capacities exceed analytical estimates. Finally, four different comparisons are presented that evaluate configuration variations of the two designs based on applicable performance criteria. Results show the RRG fault-tolerant actuator has a marked improvement over the baseline in average stiffness (14.2x), reflected inertia (3.2x) and nominal torque density (3.4x). The chapter next lists actuator test methods and aircraft qualification standards. Finally, a summary of future work is detailed in a ten step outline to bring this EMA technology to a level of early deployment in a large range of aircraft systems. more...
- Published
- 2006
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