Active vibration isolation systems with nonlinear compensation to account for actuator saturation

A vibration control module that compensates for actuator saturation. The control module includes a sensor that provides an output signal which corresponds to a movement of an element. The module also has an actuator that can move and isolate the element. The control module is controlled by a controller that performs a control routine. The control routine may include a first anti-windup stage that is coupled to the input and output of a nominal controller. The output of the nominal controller drives the actuator. The sum of the nominal controller and the actuator saturation value are provided to the input of the nominal controller. The first anti-windup stage may have a transfer function that replicates the transfer function of the control module. The first anti-windup stage provides stability for the module when the actuator is saturated. An output of a second anti-windup stage is provided as another input to the nominal controller. The inputs to the second anti-windup stage are a nominal controller state variable and the input to the first anti-windup stage.