Design and characterization of a thrust vane position controller for exhaust flow deflection TVC with dynamically changing loads
Sobering, Jacob Grey
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Missiles serve many purposes in the modern world and their control poses many complex problems. Flight paths must be followed by autopilots while position commands must be tracked by inner control loops in order to implement the missile's method of thrust vector control (TVC). There are many different methods of TVC that can be used, but for our research, exhaust flow deflection using thrust vanes was chosen. In our application, the location and material of the thrust vanes makes them susceptible to degradation due to heat and pressure. This adds additional disturbances to the system that must be addressed and characterized. Through extensive modeling and simulation, we are able to reduce the large number of disturbance variables to the most critical one: the location of the center of pressure. The force acting around this point can cause significant increases in settling time, or even instabilities, as it moves farther from the rotational axis of the thrust vane. By designing a system consisting of a position controller surrounding a torque controller, we can accurately and robustly command the thrust vane to a desired position. We can also treat the load due to the thrust vane as a disturbance acting on the system. This method simplifies the controller design and allows us more freedom when simulating the degradation effects. Once all of the system dynamics are modeled and the controllers are designed, a hardware-in-the-loop (HWIL) setup will be used to verify simulation models and controller response. This setup was designed for future HWIL use on full missile flight paths using detailed thrust vane models to qualify flight hardware. Once the hardware is complete, it will be tested against the simulation code. This combined simulation and HWIL setup allows us to explore how a change in the location of the center of pressure affects the response of the position controller and determines the steps necessary to implement further improvements in the test setup.