LMIs in Control/Matrix and LMI Properties and Tools/Negative Imaginary System DC Constraint
Introduction[edit | edit source]
These systems are often related to systems involving energy dissipation. But the standard Positive real theory will not be helpful in establishing closed-loop stability. However, transfer functions of systems with a degree more than one can be satisfied with the negative imaginary conditions for all frequency values and such systems are called systems with negative imaginary frequency response.
The System[edit | edit source]
Consider a square continuous time Linear Time invariant system, with the state space realization
The Data[edit | edit source]
The LMI[edit | edit source]
Consider an NI transfer matrix and an NI transfer matrix . The condition λ̅ is satisfied if and only if
- ,
- ,
Conclusion[edit | edit source]
The above equation holds true if and only if .
Implementation[edit | edit source]
This can be implemented in any LMI solver such as YALMIP, using an algorithmic solver like Gurobi.