1. A method for a virtual sensor system, comprising: establishing a first process model indicative of interrelationships between a plurality of input parameters and a plurality of output parameters; establishing a second process model indicative of interrelationships between at least the plurality of input parameters and modeling errors of the first process model; operating the first process model to generate values of the plurality of output parameters; simultaneously operating the second model to generate estimated deviations between the values of the plurality of output parameters and desired values of the plurality of output parameters; and compensating the values of the plurality of output parameters with the estimated deviations to generate the desired values of the plurality of output parameters.