Chapter I Problem Sheet 9 (Lectures 18–19)

  • 1. Consider the first order scalar differential equation

    \[ \dot {x}=x+u, \]

    and the performance output

    \[ y=\bbm {x\\u}, \]

    i.e.

    \[ A=2,\qquad B=1,\qquad C=\bbm {1\\0},\qquad D=\bbm {0\\1}. \]

    • (a) Determine whether or not \(D\) is injective;

    • (b) Determine whether or not \((A,B)\) is stabilizable ;

    • (c) Determine whether or not the Rosenbrock injectivity condition holds;

    • (d) Determine all symmetric positive semidefinite solutions of the algebraic Riccati equation (18.2), the corresponding state feedback matrices \(F\) and the corresponding closed-loop matrices \(A+BF\).

  • 2. Consider the undamped second order scalar differential equation

    \[ \ddot {q}(t)+q(t)=u(t), \]

    with the state \(x=\sbm {q\\\dot {q}}\) and the performance output

    \[ y=\bbm {q\\\varepsilon u}, \]

    where \(\varepsilon >0\), i.e.

    \[ A=\bbm {0&1\\-1&0},\quad B=\bbm {0\\1},\quad C=\bbm {1&0\\0&0},\qquad D=\bbm {0\\\varepsilon }. \]

    • (a) Determine whether or not \(D\) is injective;

    • (b) Determine whether or not \((A,B)\) is stabilizable ;

    • (c) Determine whether or not the Rosenbrock injectivity condition holds;

    • (d) Determine all symmetric positive semidefinite solutions of the algebraic Riccati equation (18.2) and the corresponding state feedback matrices;

    • (e) Write down the closed-loop system in second order form.