1. A method for reducing sensed physical variables including the steps of: a) generating a plurality of control commands as a function of the sensed physical variables; b) generating an estimate of a relationship between the sensed physical variables and the control commands, wherein the estimate is used in said step a) in generating the plurality of control commands; c) updating the estimate of the relationship in said step b) based upon a response by the sensed physical variables to the control commands, wherein the control command in said step a) includes a normalization factor on the convergence rate that depends on said estimate in step b), and wherein said normalization factor is updated based on the update to the estimate.