APPLICATION OF VARIABLE-STRUCTURE SYSTEM IN DC-MOTOR VELOCITY-CONTROL.

The most important characteristics of a variable-structure system (VSS) is its insensitivity to parameter variations in the sliding mode. Three methods of VSS are used to implement DC-motor velocity control. The conventional VSS used only a sliding line. The adaptive VSS used multiple switching lines. The modern method used a sliding curve. The modern method makes system trajectory following the sliding curve which has been set up in the controller from the initial state to the origin in the phase plane. Hence it is insensitive to parameter variations from the initial state to the steady state. If parameter variations are the most critical factors, the modern VSS is the right method to be considered to overcome the problem of parameter variations.