Abstract: For the control of unmanned helicopter, different controllers have been designed in the literature. Model Predictive Control (MPC) was used in process industry for years. But its application to helicopters is new. In this study, six degrees of freedom nonlinear dynamical model of unmanned helicopter is used to control the translatory velocities and angular displacements. Additionally, two different controllers based on MPC and LQR (Linear Quadratic Control) are designed and numerically tested on the open loop unstable helicopter model. Simulation scenarios with different starting conditions are studied in detail and the outputs are compared. Results demonstrated that with equal or less control effort, MPC-type controller became more successful than LQR controller.
Abstract: Platforms simulated by Commercial frameworks, supporting Computer Generated Forces (CGF) and control architecture, generally have simple motion equations with inadequate fidelity. Consequently, the commercial framework based CGF applications are not always able to meet the needs of training-critical military simulations that use motion models with high-fidelity. Therefore, the integration of platforms with high-fidelity motion models into the CGF applications based on commercial frameworks occurs as a critical problem.
In this paper, we present the modeling of rotary wing platforms with realistic 6 degrees of freedom motion equations, control of the platform via LQR based control methods and their integration into a commercial framework based CGF application within a high-fidelity virtual military training simulation.
In this study, VR-Forces has been chosen as the commercial framework to build the CGF and control architecture, and C++ programming language has been used to implement the software module for the proposed motion model. Furthermore this software module has been integrated to the VR-Forces back-end as a composite object. Finally two scenarios were formed to realize the simulations.
Abstract: Realistic models and robust control are vital to reach a sufficient fidelity in military simulation projects including surface vessels. In this study, a nonlinear model including sea-state modelling is obtained and feedback linearization control is implemented in this model. To control the system, nonlinear analysis techniques are used. The model is integrated into a commercial framework based CGF application within a high-fidelity military training simulation.The simulation results are presented at the end of the study.
Abstract: Sonobuoys are relatively small, expandable sonar systems those are dropped or ejected from aircraft or ships, floating on the sea and serving as anti-submarine agents. Sonobuoys are subjected to high temperature differences in the storage conditions as well as vibration and/or shock loading during mission flights. Probably the most extreme case occurs when Sonobuoy hits the sea surface as it is dropped from an aircraft. In order to ensure the structural integrity and functionality of Sonobuoys, all these conditions should be considered carefully in design phase. The pressure-activated buoy mechanism should also be guaranteed to work properly, which would otherwise result in the failure of whole system.
In this work, the finite element analyses of a full-scale Sonobuoy model with more than 2 million degrees of freedom were accomplished. Having managed to build a proper finite element model of the Sonobuoy, some modal analyses were run. The modal analyses were followed by random vibration analysis. For shock loading, some transient analyses were carried using implicit time integration. The input parameters for random vibration and shock analyses were determined according to the test parameters as specified in MIL-STD-810F, which is the standard for âEnvironmental Engineering Considerations and Laboratory Testsâ. Sonobuoy
was also hold at two extreme storage temperatures; +60 oC and -20 oC respectively and resulting thermal expansions and stress fields were revealed . The strike of Sonobuoy as it gets into the sea water was also simulated including the fluid-structure interaction. Lastly, the analysis of pressure-activated buoy mechanism was carried in submodel scale. This highly nonlinear problem was solved explicitly as well as implicitly and results were compared.
Abstract: Controlling rotary wing platforms, especially on helicopters, is a difficult task because of the nonlinearity of the structure and strong coupled motion dynamics. In this paper, a linear, quadratic regulator method is used to control the trajectory and mission paths of the autonomous helicopter. Nonlinear motion dynamics is linearized at certain operating points and linear model is obtained by Taylorâs series expansion. This model is integrated into MATLAB® program. By using LQR (Linear Quadratic Regulator) methodology, the attitude of the autonomous Puma helicopter is controlled and two simulations are realized. The results show that thisapproach can effectively be applied to control rotary wing platforms on helicopters.
Abstract: High-fidelity modelling for motion, response to physical stimuli and attack behaviours along with realistic control are vital requirements for training-critical military simulations. In addition, whenever simulation components are built on different infrastructures, maintaining coordination becomes a challenging problem. There are several COTS frameworks that facilitate development of computer generated forces (CGF), scenario management and run control for distributed simulations. However, they may not always afford to meet the requirements of virtual military training simulation systems. In this paper, we present modeling and simulation of surface vessels, submarines and rotary wing platforms with complex motion equations, several sensors, weapons and fuzzy logic controllers within a high-fidelity virtual military training simulation. Modules and libraries for high-fidelity entity simulation are integrated into component architecture of a commercial CGF simulation engine, namely VR-Forces. An original control architecture, which is able to manage all kinds of simulation components with different infrastructures, has also been realized.
Abstract: Hydrophone, used to listening passively, has to be hold on motionless to be used efficiently. Thus, sonobuoy needs a suspension system.
In this study, sonobuoy suspesion system has been scrutinized; mathematical model has been modeled to model dynamically. A tool, called FST, has been developed by MATLAB to analyze dynamic behavior of the sonobuoy. This tool, geometry of the suspension system can defined by, is a simulation to observe the response of the sonobuoy line hydrophone suspension to surface wave-induced and to flow-induced motions. the results of simulation has been discussed.
Abstract: The subject of this study is the translatory speed and angular position control. Within the scope of this thesis first 6 degrees of freedom nonlinear helicopter model is developed. This model consists of 3 blocks which are called, rigid body equations, force and moment equations and flapping and thrust equations. Each block consists the equation set of relevant part. Model that was developed transferred to MATLAB software. For the helicopter which is open loop unstable and having high coupling between the axes two different controller was designed. First an LQR (Linear Quadratic Regulator) type controller was developed. By considering the basic movements of helicopter like forward flying, sideway flying, flying with pitch angle and vertical flying 8 different scenarios was formed. Due to these scenarios simulation results were obtained. For the same scenarios MPC (Model Predictive Controller) type controller was designed and simulations were made. For evaluating robustness of controller 3 different scenarios, having parameter uncertainity, alteration of system dynamics and disturbances, was formed and simulation results were achieved. Results that are obtained from two different controllers were discussed and suggestions made for future works.
Abstract: Su altı akustiÄi, deniz yataÄı ve su altında ses dalgalarının doÄrusal ve doÄrusal olmayan yayılımını, saçılımı ve etkileÅimini inceleyen ve buna dayalı pratik uygulama alanları geliÅtiren bir bilim dalıdır. Bu raporda sualtı akustiÄinin temel kavramlarından bahsedilecek ve uygulamalarından örnekler verilecektir.
