Homework 3
ME5659 Fall 2024
Due: See Canvas, turn in on Gradescope
Problem 1 (9 points)
Consider the following linear systems ẋ = Ax, x(0) = x0 , where
0 1 −0.2
(i) A = , x0 = .
−14 −4 0.1
0 1 0.01
(ii) A = , x0 = .
−14 4 0.02
0 1 0
(iii) A = , x0 = .
−14 0 0
(a) 3 points. Characterize the stability of the equilibrium point from the eigenvalues of A.
(b) 3 points. Use Lyapunov stability analysis to determine whether the system equilibrium state xeq = 0
is asymptotically stable. Use Q = I in the Lyapunov equation. (Do all calculations by hand.)
(c) 3 points. Use MATLAB to plot the state trajectories x(t) vs. time t with the initial condition x0 .
Each plot has two trajectories x1 (t), x2 (t). Hand in your plots and your code.
1
Problem 2 (6 points)
Consider the inverted pendulum (Figure 1) which is characterized by
ml2 θ̈ = mglsinθ − bθ̇ + T
where T denotes a torque applied at the base and g is the gravitational acceleration. We assume that u = T
and y = θ are its input and output, respectively.
Figure 1: Simple pendulum
(a) (3 points) Perform local linearization of this system around the equilibrium point θ = π, derive the
linear state-space models and determine whether it is stable or not.
(b) (3 points) Perform local linearization of this system around the equilibrium point θ = 0, derive the
linear state-space models and determine whether it is stable or not.
2
Problem 3 (10 points)
Consider the following linear system ẋ = Ax, x(0) = x0 , where
0 1
A=
a b
(a) (4 points) Under what conditions on a, b is the system equilibrium, xeq = 0, asymptotically stable?
Use Lyapunov stability analysis.
(b) (3 points) Write the Lyapunov function V (x) and its time derivative V̇ (x). Use the P matrix
obtained in (a) to evaluate stability.
(c) (3 points) If b = 0, a < 0, show that the linear system is stable but not asymptotically stable.