Physics-based multivariable control design for real-time, command-driven and disturbance-driven systems. Emphasis on application to practical issues in multi-axis precision motion control, power electronics current and voltage control, motor drive torque and flux control. Nonlinear state feedback design based on active manipulation of physical properties. Observed-based estimation methodologies for accurate, wide bandwidth sensor replacement. Inherent parameter sensitivity and bandwidth properties of Luenberger- and Gopinath-style observer topologies. Disturbance estimation and disturbance input decoupling design via observers. Practical model reference adaptive control design methodologies.