A variable structure control approach to friction force compensation

Describes a variable structure control approach to the compensation of friction force in two mechanical system control problems. The first one is the active control of sliding base isolator systems which are designed to protect civil structures from excessive ground excitations due to earthquakes. The second one addresses precision positioning, commonly encountered in precision manufacturing and optomechanical systems. This approach exploits the well known robustness and disturbance rejection capabilities of sliding mode control to deal with the discontinuity of friction force at zero velocity which is due to Coulomb friction, and with other nonlinear friction characteristics when the relative velocity of the mechanical parts in contact goes through different speed regimes