Mohammad A. Ayoubi

Analytical Solutions for Thrusting, Spinning Spacecraft Subject to Constant Forces

A spinning, nearly axisymmetric rigid body is subject to constant, body-fixed forces and transverse body-fixed torques. Because no torque is applied along the spin axis and the rigid body is nearly axisymmetric, the spin rate remains nearly constant. By further assuming small angular excursions of the spin axis (with respect to an inertially fixed direction), approximate closed-form analytical solutions are obtained for attitude, rotational, and translational motion. The compact solutions in complex form are eminently suitable for analyzing maneuvers of spinning spacecraft. Numerical simulations confirm that the solutions are highly accurate when applied to typical motion of a spacecraft such as the Galileo spacecraft.

Analytical Solutions for Translational Motion of Spinning-Up Rigid Bodies Subject to Constant Body-Fixed Forces and Moments

The problem of a spinning, axisymmetric, or nearly axisymmetric rigid body subject to constant body-fixed forces and moments about three axes is considered. Approximate closed-form analytical solutions are derived for velocity and for the transverse displacement. The analytical solutions are valid when the excursion of the spin axis with respect to an inertially fixed direction is small (which is usually the case for spin-stabilized spacecraft and rockets). Numerical simulations confirm that the solutions are highly accurate when applied to typical motion of a spacecraft, such as the Galileo.

Fuzzy model-based pitch stabilization and wing vibration suppression of flexible aircraft

This paper presents a fuzzy nonlinear controller to regulate the longitudinal dynamics of an aircraft and suppress the bending and torsional vibrations of its flexible wings. The fuzzy controller utilizes full-state feedback with input constraint. First, the Takagi-Sugeno fuzzy linear model is developed which approximates the coupled aeroelastic aircraft model. Then, based on the fuzzy linear model, a fuzzy controller is developed to utilize a full-state feedback and stabilize the system while it satisfies the control input constraint. Linear matrix inequality (LMI) techniques are employed to solve the fuzzy control problem. Finally, the performance of the proposed controller is demonstrated on the NASA Generic Transport Model (GTM).

An Optimal Fuzzy-PID Controller for Aircraft Pitch Control

This paper presents a simple-structured Fuzzy-PID controller for pitch control of a linearized, full-scale, generic transport aircraft model. Particle swarm optimization (PSO) is applied to oine optimize the Fuzzy-PID controller scaling gains as well as simultaneously optimize parameters within the rst order Takagi-Sugeno (TS) type inference system. The performance of the controller is tested against a baseline state feedback and ne-tuned PID (PSO-PID) controller. Numerical simulations are conducted comparing the Fuzzy-PID controller to the other linear controllers when linear and nonlinear models of uncertainty are added post-optimization. The results demonstrate the robustness of the proposed nonlinear, oine optimized Fuzzy-PID controller.

Attitude Motion of a Spinning Spacecraft with Fuel Sloshing and Nutation Damping

We use Kane’s method to derive the equations of motion of a spinning spacecraft with three momentum wheels, a nutation damper, and a spherical pendulum. The spherical pendulum is adopted as a simple mechanical equivalent of fuel sloshing in partially filled tanks. The proposed model is an extension of existing models in the literature. We verify and validate our model for two cases: flat spin and a simple reorientation maneuver. Numerical simulations are in agreement with existing results in the literature. The results confirm the accuracy of the model for a typical spacecraft.

Analytical Solution for Spinning Thrusting Spacecraft with Transverse Ramp-Up Torques

During axial thrusting of a spin-stabilized spacecraft undergoing orbital injections or control maneuvers, misalignments and center of mass offset create undesired body-fixed torques. The effects of the body-fixed torques, which in turn cause velocity pointing errors, can be reduced by ramping up (and then ramping down) the thruster. Closed-form solutions for the angular velocity, Euler angles, inertial velocity, and inertial displacement solutions with nonzero initial conditions are given. Using the closed-form solutions, the effect of variations in the spin axis moment of inertia and spin rate on the spacecraft velocity pointing error are shown. The analytical solutions closely match numerical simulations.

Takagi-Sugeno Fuzzy Model-Based Attitude Control of Spacecraft with Partially-Filled Fuel Tank

This paper presents a Takagi-Sugeno fuzzy model-based controller which stabilizes the attitude of spacecraft with a partially-filled fuel tank. First, the nonlinear equations of motion of spacecraft containing a liquid fuel store is presented briefly. Then, the fuzzy modeling and the parallel distributed compensation control technique are applied. The proposed fuzzy controller is a nonlinear controller which utilizes full-state feedback with bounded control input. Using a quadratic Lyapunov function, the fuzzy control design problem can be formulated in terms of linear matrix inequalities. In the end, we evaluate the proposed control system performance via numerical simulation results.

Fuzzy Model-Based Optimal Variance Control of Flexible Aircraft with Actuator Amplitude and Rate Constraints

This paper presents the study of a fuzzy optimal covariance control problem for wing shaping control of coupled aeroelastic aircraft models at various flight conditions and subject to actuator amplitude and rate constraints. Using Takagi-Sugeno fuzzy modeling and Parallel Distributed Compensation techniques, the stability and the constraints can be cast as a multi-objective optimization problem in the form of Linear Matrix Inequalities. By utilizing the formulations and solutions for the output covariance constrained problems, we develop a fuzzy full-state feedback controller and a fuzzy full-order observer for aeroelastic aircraft with flexible wings. The efficacy of the proposed controllers are examined on the NASA Generic Transport Model which is configured with the Variable Camber Continuous Trailing Edge Flaps.

Robust-Optimal Fuzzy Model-Based Control of Flexible Spacecraft With Actuator Amplitude and Rate Constraints

This paper presents a robust-optimal fuzzy controller for position and attitude stabilization, and vibration suppression of a flexible spacecraft during antenna retargeting maneuver. The fuzzy controller is based on Takagi-Sugeno (T-S) fuzzy model and uses the dynamic parallel distributed compensator (DPDC) technique to quadratically stabilize the closed-loop system. The proposed controller is robust to parameter and unstructured uncertainties of the model. We improve the performance and the efficiency of the controller by minimizing the upper bound of the actuators amplitude and rate, and maximizing the uncertainties terms included in the T-S fuzzy model. In addition to actuator amplitude and rate constraints, a fuzzy model-based observer is considered for estimating unmeasurable states. Using Lyapunov stability theory and linear matrix inequalities (LMIs), we formulate the problem of designing an optimal-robust fuzzy controller/observer with actuator amplitude and rate constraints as a convex optimization problem. Numerical simulation is provided to demonstrate and compare the stability, performance, and robustness of the proposed fuzzy controller with a baseline nonlinear controller.© 2015 ASME

Optimized Fuzzy-Proportional/Integral/Derivative Controller for Aircraft Pitch Control

This paper presents a simple-structured fuzzy-proportional/integral/derivative controller for pitch control of a linearized full-scale generic transport aircraft model. Particle swarm optimization is applied to offline optimize the fuzzy-proportional/integral/derivative controller scaling gains as well as simultaneously optimize parameters within the first-order Takagi–Sugeno-type inference system. The performance of the controller is tested against a baseline state feedback and fine-tuned proportional/integral/derivative (particle swarm optimization–proportional/integral/derivative) controller. Numerical simulations are conducted comparing the fuzzy-proportional/integral/derivative controller to the other linear controllers when linear and nonlinear models of uncertainty are added post-optimization. The results demonstrate the robustness of the proposed nonlinear offline optimized fuzzy-proportional/integral/derivative controller.