Adaptive attitude control of satellite

The present work aims at a study of Attitude tracking and control of a rigid spacecraft model. The plant (spacecraft model) is a sixth order nonlinear multi-input-multi-output system. The plant is stabilized using state feed-back. The stability of the closed-loop is assured using Routh-Hurwitz criterion and a Lyapunov function. The step response of the closed-loop is used to design two PID controllers using standard classical techniques (Ziegler-Nichols and Cohen-Coon). Two adaptive control structures are proposed for the spacecraft model such that the output of the spacecraft model follows the desired input (attitude trajectory). The first structure is Feed forward learning based adaptive control structure. Attitude tracking is established using this structure by incorporating an adaptive filter with the PID controller using normalized least mean square adaptation algorithm. The second structure is an Internal Model Control (IMC) based adaptive structure. The IMC structure consists of an explicit model of the plant along with the feed forward PID controller. The model of the plant is computed using normalized least mean square adaptation algorithm. The adaptive control structures are independent of the plant parameters and do not require a priori knowledge of the spacecraft inertia matrix. The overall closed-loop is such that the controllers design depends on the output of the plant. Computer simulation results are done to illustrate the effectiveness of the proposed control structures and showed good control and tracking characteristics.; Finally an experiment is performed to illustrate the idea of attitude control in satellites. A Cube-Sat model is designed and is shown to track a light source demonstrating the idea of attitude tracking. The light source represents the sun's light in space. The objective of this work is to detect the location of the sun and rotate the Cube-Sat towards the sun's position, so that maximum solar power can be utilized. Stepper Motor is used to drive the Cube-Sat, which receives signal from a light sensing device. The system is designed such that, when the light source moves the Cube-Sat also moves towards the light source's direction. When the required face is positioned towards the Sun, the supply to the motor is disconnected. The total system, including Stepper motor that drives the Cube-Sat, operates at 12V DC. For the demonstration purpose 12V DC is derived from a power supply kit. In this project work LDR (light dependent resistor) is used as a light sensing device. They are used for detecting the direction of Sunlight. The motion of the motor is bi-directional acquiring the nearest possible path to the sun. To serve this purpose a second LDR is used which changes the direction of the stepper motor when it senses light. The complete setup is stand alone and the setup photos illustrate the work carried out.