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Nonhyperbolic Equilibria, Hamiltonian & Gradient Systems, Lyapunov Function, Ideal & Damped Pendulum
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Bill Kinney's Differential Equations and Linear Algebra Course, Lecture 33A.
(a.k.a. Differential Equations with Linear Algebra, Lecture 33A, a.k.a. Continuous and Discrete Dynamical Systems, Lecture 33A).
#hamiltoniansystems #lyapunovfunction #pendulum
(0:00) Lecture plans
(1:20) What can happen at non-hyperbolic equilibrium points?
(1:58) One-parameter family of nonlinear (cubic) ODEs where the polar coordinate “r” is relevant
(4:01) Use Mathematica to see what happens
(9:00) Transformed differential equation for dr/dt (differential equations in the polar coordinate r)
(12:45) Transformed differential equation for dθ/dt (differential equations in the polar coordinate θ)
(15:53) General Hamiltonian systems, Hamiltonian functions, and their properties
(18:16) General gradient systems, potential functions, and their properties
(21:20) Lyapunov function for a gradient system is the negative of the potential function
(22:36) What does it mean to be a Lyapunov function?
(25:23) Lyapunov functions and trapping regions for gradient systems (Lyapunov functions can be used to define trapping regions)
(28:34) Theorem about closed and bounded trapping region (there is at least one solution curve inside the trapping region for all time t)
(32:51) Ideal Pendulum (Undamped) Nonlinear and Unforced ODE
(36:37) This is a Hamiltonian system with Hamiltonian function representing total mechanical energy
(39:25) Physical interpretation of solutions (including separatrices)
(40:54) Damped Pendulum (include friction)
(46:33) Visualize the pendulum motion on Mathematica
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