The SPACECRAFT SIMULATOR robust control through H∞-based linear matrix inequality (LMI) and robust adaptive method is implemented. The SPACECRAFT attitude control subsystem SIMULATOR consists of a platform, an air-bearing and a set of four reaction wheels. This set up provides a free real-time three degree of freedom rotation. SPACECRAFT SIMULATORs are applied in upgrading and checking the control algorithms' performance in the real space conditions. The LMI controller is designed, through linearized model. The robust adaptive controller is designed based on nonlinear dynamics in order to overcome a broader range of model uncertainties. The stability of robust adaptive controller is analysed through Lyapunov theorem. Based on these two methods, a series of the laboratory and computer simulation are made. The tests’ results indicate the accuracy and validity of these designed controllers in the experimental tests. It is observed that, these controllers match the computer simulation results. The SPACECRAFT attitude is converged in a limited time. The laboratory test results indicate the controller ability in composed uncertainty conditions (existence of disturbances, uncertainty and sensor noise).

In this paper, the performance of two robust control algorithms, μ-synthesis and high order sliding mode are evaluated on a SPACECRAFT attitude control subsystem SIMULATOR as the hardware in the loop. This tabular SIMULATOR is placed on a spherical air bearing to validate real-time environment. All actuators and sensors on the platform of SPACECRAFT SIMULATOR prepare real conditions as attitude control test bed. Beginning, both designed controllers are simulated by Matlab software, next they are applied on the subsystem. At first, μ-synthesis robust controller is designed for SIMULATOR. In this method, weighting matrix are chosen such that the controller becomes robust in combined uncertain condition such as system uncertainties, environmental disturbances and sensor noises. Uncertainty, performance, actuator saturation, disturbance and noise weighting functions are designed based on the dynamics and environmental platform properties. At least high order sliding mode controller based on super twisting algorithm is designed to reduce chattering effects. Contrary to the other second order sliding mode algorithms, in the super twisting method sliding surface derivatives are not used. The Computer and experimental hard ware in the loop simulations are compared together.

In order to perform attitude control ground experiments, it is crucial to ensure the center of mass of the platform coincides with the center of rotation as accurately as possible. In this paper, a linearized dynamic model of the imbalanced attitude platform is derived, and a linear controller is methodically designed to stabilize the system by mass relocation. The stability conditions of the system under the proposed controller are derived. The balancing procedure starts with a parameter estimation method to estimate the center of mass offsets. Next, the PD controller is applied to align the platform’s horizontal plane with the local horizontal level. Finally, the imbalance in the vertical axis can be estimated and compensated to complete the automatic mass balancing. Actuator limitations and nonlinear equations of motion are implemented in numerical simulations, and the results demonstrate the effectiveness of the proposed method in significantly reducing the residual imbalance torque on the simulated platform.

This study deals with the design and experimental implementation of an adaptive actuator failure compensator for a SPACECRAFT attitude control SIMULATOR in the presence of unknown actuator failures and uncertainties. The adaptive actuator failure compensation controller is designed using the backstepping method, which considers uncertainties in the time of occurrence, values, and failure patterns. The adaptive backstepping control method is designed to compensate for the uncertainties of the actuator failure by incorporating the inertia matrix and the distribution matrix. The stability analysis of the proposed adaptive controller for the dynamics of the SPACECRAFT SIMULATOR with actuator failures has been carried out. Simulation results and laboratory studies are presented to show the effectiveness of the proposed controller in the presence of stuck, sinusoidal, and complete failures in the SPACECRAFT attitude control SIMULATOR system. The results indicate the good performance of the proposed method in the presence of unknown actuator failures and model uncertainties in the system.

This article describes the details of a Tri-axial SPACECRAFT SIMULATOR Testbed (TSST) that has been developed as part of a research program on SPACECRAFT multi-body rotational dynamics and control in Space Research Laboratory (SRL) at K. N. Toosi University of Technology. This dumbbell style SIMULATOR includes a variety of components: spherical air-bearing, inertial measurement unit (IMU), rechargeable battery, reaction wheels (RW), on-board computer (OBC) and balancing masses. In this paper, an attitude control problem for the SPACECRAFT SIMULATOR actuated by three reaction wheels is studied. Under the assumption of uniform gravity and frictionless air-bearing environment, reaction wheels generate control moments about the roll, pitch and yaw axes of the base body. The control objective is to perform attitude commands sent from users with the least power consumption and a high precision. To handle the non-linear model, a Linear Quadratic Ricatti (LQR) controller has been programmed and it efficaciously controlled the computer-modeled SIMULATOR for any given slewing maneuver.This control approach has been developed to facilitate the system to accomplish largeangle, three-axis slewing maneuvers using RWs as effective actuators.

In this paper, the effect of using various intelligent algorithms to optimize the adaptive neuro-fuzzy disturbance observer has been investigated. First, a model reference adaptive control is designed for the SPACECRAFT SIMULATOR. Then, in order to reduce the disturbance effect, an adaptive neuro-fuzzy disturbance observer is used. In this paper, the fuzzy system is optimized using Intelligent Genetic Algorithm, Particle Swarm Optimization, Imperialist Competitive Algorithm, Bee Colony, Ant Colony Optimization, and especially Policy Gradient Particle Swarm Algorithm, which speeds up and optimizes the response. The Policy Gradient Particle Swarm algorithm is a combination of gradient policy reinforcement learning and particle swarming ideas and is a hybrid optimization method to control a nonlinear complex system with many applications in the real world. In this method, influenced by reinforcement idea, the policy gradient for a non-fossilized system is calculated, and in the optimization of particle swarm relations, optimization is performed in addition to the factors included in the congestion methods in the direction of the policy gradient. It is intended to optimize the fuzzy neuro system parameters and input and output data in the cost function. Finally, the neuro-fuzzy systems optimized by these algorithms are compared and it is shown that the gradient particle swarm algorithm performs better than the particle swarm algorithm.

Several optimal three-dimensional orbital transfer problems are solved for thrust-limited SPACECRAFTs using collocation and nonlinear programming techniques. The solutions for full nonlinear equations of motion are obtained where the integrals of the free Keplerian motion in three dimensions are utilized for coasting arcs. In order to limit the solution space, interior-point constraints are used which proved to be beneficial in finding the optimal results by making initial estimates more sensible. The application of this methodology to the design of several three dimensional optimal trajectories is also investigated. The results indicate that the method is suitable for any 3D transfer between non-coplanar and non-coaxial orbits.

In this paper, the problem of attitude control of a 1D non-linear flexible SPACECRAFT is investigated. Three controllers are presented. The first is a non-linear dynamic inversion, the second is a linear m-synthesis and the third is a composition of dynamic inversion and a m-synthesis controller. It is assumed only one reaction wheel is used. Actuator saturation is considered in the design of controllers. The performances of the proposed controllers are compared in terms of nominal performance, robustness to uncertainties, vibration suppression of panels, sensitivity to measurement noise, environment disturbance and non-linearity in large maneuvers. To evaluate the performance of the proposed controllers, an extensive number of simulations on a non-linear model of the SPACECRAFT are performed. Simulation results show the ability of the proposed controller in tracking the attitude trajectory and damping panel vibration. It is also verified that the perturbations, environment disturbance and measurement errors have only slight effects on the tracking and damping responses.