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

The most important characteristic of a variable-structure system (VSS) is its insensitivity to parameter variations in the sliding mode. In this paper three methods of VSS are used to implement dc-motor velocity-control. The conventional VSS uses only a sliding line. The adaptive VSS uses multiple switching lines. The modern method uses a sliding curve. The modern method makes a system trajectory following the sliding curve which has been set up in the controller from the initial state to the origin in 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, then the modern VSS is the right method to be considered to overcome the problem of parameter variations.