| The principle of Variable Structure Control (VSC) and adaptive methods for control have been developed all over the world during the last three decades. The needs of the industry to deal with uncertainties in modeling and to control systems which tend to become unstable on account of variations in the plant and environmental parameters, have made these techniques more in demand.; The first algorithm called the Single Structure Change Controller (SSCC) is derived from VSC. Its advantage over the VSC system is that chattering is eliminated. A reachable switching surface is designed which causes the trajectory to reach its vicinity. The plant input is obtained using state feedback to provide complex conjugate eigenvalues during the reaching phase and faster eigenvectors during the post switching phase; this ensures reachability as well as improves the response time.; The second algorithm called the Gain Modified Adaptive Control (GMAC) is based on adaptive feedback control theory and continuous feedback gain calculation based on state identification. An online state estimation is utilized to gauge the position of the state trajectory; an appropriate feedback gain calculation is utilized to move the poles of the system such that the trajectory follows its intended path and the desired output is obtained, in spite of changes in the system parameters. This method is advantageous for control of plants with uncertain parameters as well as those that have a tendency to become unstable on parameter variations.; Simulink and Matlab toolboxes were used to produce the simulations. A comparison of existing and proposed methods is provided. |
