Based on the invariance principle of differential equations a simple, systematic and rigorous adaptive-feedback controller is proposed to stabilize nonlinearly any chaotic systems.

Further more, based on the estimator a high order differential feedback controller is designed, which does not rely on the model of the nonlinear system, and has well stability and robustness.

A signal (termed the "measured value") which is proportional to the pressure difference is then transmitted by means of a "differential pressure transmitter" to the recorder-controller.