Dynamical system theory for engineers
COM-502
Media
COM-502 Dynamical system theory for engineers - complementary video at the blackboard
COM-502 Chap.7 Bifurcations: Transcritical Bifurcation Part 2
19.11.2020, 11:07
Example of Transcritical Bifurcation: SIS Epidemics
COM-502 Chap.7 Bifurcations: Transcritical Bifurcation Part 1.
19.11.2020, 10:46
Note - the video covers some tedious technical details explaining the change coordinates to simplify the Taylor expansion of F(x,\mu), which may be skipped.
COM-502 Chap.5 Stability of Discrete time periodic solutions
23.10.2020, 16:12
COM-502 Chap.5 Small scale stability Part.1
05.10.2020, 11:39
COM-502 Chap.5 Small scale stability Part.2 equilibrium point
05.10.2020, 11:39
COM-502 Chap.5 Small scale stability: gradient systems
05.10.2020, 11:39
COM-502 Chap.5 Large scale stability Part.1
29.09.2020, 16:43
COM-502 Chap.5 Large scale stability Part.2
29.09.2020, 16:14
COM-502 Chap.1 Introduction Part.2
28.09.2020, 14:48
COM-502 Chap.1 Introduction Part.1
28.09.2020, 14:40
Course description: Establishing the theoretical basis of linear and nonlinear dynamical systems in both continuous and discrete time. Learning how to anticipate the qualitative behavior of the time-evolution of linear and nonlinear dynamical systems. Introduce the students to some tools from ergodic theory and/or stochastic approximation and their relation to dynamical systems. The course is fairly abstract and mathematical, and does not cover applications (other than some examples used for illustration purposes).
Lectures: Wednesday 8:15 - 11:00 in ELA 1. Teaching is in class (most classes are taught on the blackboard). Do NOT take this course if you have a conflict of schedule and cannot attend the lectures. A
few video recordings are available on this channel, but the course
format has evolved and these videos do NOT cover only a portion of the
course material. They are NOT meant to replace the lectures.
Exercises: Wednesday 11:00 - 12:00 in ELA 1 Teaching Assistant: Paula Mürmann.
- The exercise set will be posted on moodle for the week where the exercises are assigned.
Prerequisites:
- Linear Algebra (MATH-111 or equivalent),
- Calculus (MATH-101, -102 and -103 or equivalent),
- Signals & Systems and/or Signal Processing (COM-202, EE 205 or an equivalent linear circuits/systems/signals class),
- Probability (MATH-232 or equivalent).
These are mandatory prerequisites: Do NOT take this course unless you have followed successfully all these classes. Complex analysis (MATH-104 or equivalent), Stochastic processes (COM-300 or equivalent) are very strongly recommended prerequisites. Some chapters of the course will require some notions of general topology and measure theory.
Midterm: Wednesday April 9, 8h15am-10h15am. The midterm (max 30 points) covers all the material seen in class until and including Chapter 5, Section 5.3.4. You may use only the extended class notes summary available on the moodle site that you should print yourself. No device with communication capabilities,
thus no calculator, computer, and mobile phones have to be stowed away.
Final exam: Monday June 30, 15h15-18h15. Room CE 1 105. The exam (max 70 points) covers all the material seen in class during the semester and is made of two parts:
- the
first part (20 points) is completely "closed book" : no document is allowed. This
part will only have questions calling for a true/false answer with a
short justification.
- the second part (50 points) is partially "open book", but you may use only the extended class notes summary uploaded on moodle. No class notes, no exercise set, no solution of exercise sets, nor any other material are allowed.
Final grade (100%) = Midterm (30%) + Final exam (70%).
Office hour. We will hold an extra office hour for last minute questions on Wednesday June 25 from 1h30pm until 3pm in Room INF 211.
- Summary allowed during midterm and the open question part of the final (File)
- Books on dynamical systems (File)
- News forum (Forum)
Subjects Covered during Week 1:
0. Introduction to the course
- Objectives, content, logistics
1. Introduction:
- Notion of dynamical systems
- Examples
- General form of the state equations
- Notion of state
- Notion of flow
- Existence and uniqueness of the solutions
- Asymptotic behavior
- Invariant sets
- Omega- and alpha-limit sets
- Attractors
- Course Notes: Introduction (File)
- Copied from the book of J.K.Hale: Omega and alpha limit sets (File)
Subjects covered during week 2:
2. Linear Systems
- Time domain solution
- Stability: Definition
- Exponential of a diagonalizable matrix
- Stability of a linear system with a diagonalizable state matrix
- Jordan normal form
- Stability of a linear system with a non-diagonalizable state matrix
- General form of the free solution of linear systems
- Stability of linear discrete-time systems
Exercises:
- Existence and unicity of solutions, Asymptotic Behavior
- Course Notes: Stability of Linear Systems (File)
- Slides Linear Systems Part 1 (File)
- Exercise Set 1 (File)
- Solutions of exercises set 1 (File)
- Nineteen dubious ways to compute the exponential of a matrix (not exam material) (File)
Subjects covered during week 3:
2. Linear systems (continued):
- Classification of the flows of 2-d autonomous continuous-time systems
- Phase portraits of 2-dim and 3-dim autonomous systems.
- Stability of linear systems: general case
- Link with Frequency Domain Analysis
- BIBO-stability
Exercises:
- Asymptotic Behavior
- Solution of linear autonomous systems
- Slides Linear Systems Part 2 (File)
- Slides Linear Systems Part 3 (File)
- Exercise Set 2 (File)
- Solutions of exercises set 2 (File)
- Copied from the book of Strogatz: Romeo & Juliet: Love affairs example (File)
- Copied from the book of Brauer and Nohel: Linear Systems (File)
Subjects covered during week 4:
- Observability
- Controllability
4. Introduction to nonlinear systems
- Introduction to nonlinear systems
- Van der Pol oscillator
- Strange attractors
- Fractals
Exercises
- Jordan normal form
- Stability of linear systems
- Classification of equilibria and sketching of phase portraits
- Course notes: Observability and Controllability (File)
- Course notes: Introduction to Nonlinear Systems (File)
- Slides Introduction to Nonlinear Systems (File)
- Exercise Set 3 (File)
- Python File (File)
- Solutions of exercise set 3 (File)
5. Stability of nonlinear systems
-
Large-scale notions of (in)stability
-
Boundedness and asymptotic uniform boundedness of solutions
-
Lyapunov functions for proving boundedness and asymptotic uniform boundedness of the solutions
- Special class of systems: Hamiltonian systems
Exercises:
- Solutions of linear discrete-time systems.
- BIBO Stability
- Observability and controllability
- Course notes: Stability of Nonlinear Systems (File)
- Exercise Set 4 (File)
- Solutions of exercise set 4 (File)
Subjects covered during week 6:
5. Stability of nonlinear systems (continued)
- Small-scale notions of (in)stability
- Stability of a solution
- Criterion for stability of a fixed/equilibrium point
- Sketching the flow in the vicinity of a fixed/equilibrium point in 2 dimensions
Exercises:
- Large-scale notions of stability.
- Exercise Set 5 (File)
- Solutions of exercise set 5 (File)
- Slides (examples, small scale stability) (File)
5. Stability of Nonlinear Systems (continued)
- Lyapunov functions for estimating the basin of attraction of an asymptotically stable equilibrium/fixed point and for proving global asymptotic stability of an equilibrium/fixed point.
- Special class of systems: Gradient systems.
- Additional Example: Physarum can
Compute Shortest Paths.
Exercises
- Stability of equilibrium/fixed points
- Vincenzo Bonifaci, Kurt Mehlhorn and Girish Varma, ``Physarum can compute shortest paths", Journal of Theoretical Biology, vol. 309, pp. 121-133, 2012 (File)
- Vincenzo Bonifaci, ``Physarum can compute shortest paths: a shorter proof", Information Processing Letters, vol. 113, pp. 4-7, 2013. (File)
- Slides Additional Example: Physarum can Compute Shortest Paths (File)
- Physarum can compute shortest paths: example with 2 links in parallel (File)
- Exercise Set 6 (File)
- Solutions of exercise set 6 (File)
- Sample Midterm of a previous year (File)
- Sample Midterm from previous year: Solution. (File)
- Another Sample Midterm (File)
- Another Sample Midterm : Solution (File)
Midterm on Chapters 1, 2, 3, 4 and 5 (until and including Section 5.3.4). (max 30 points)
- Wednesday April 9, 8h15-10h15 in the usual room ELA1.
- Material allowed: only the extended class notes summary (which is the same summary as the one allowed during the open question part of the final) and which is posted on this moodle site. The summary must not be annotated (you can highlight some text in color if you wish so, but cannot add any other information). No other class-notes, hand-written notes, exercises nor other textbook material are allowed.
- No device with communication capabilities,
thus no calculator, computer, and mobile phones have to be stowed away.
No other exercise assignment this week.
Extra office hours: We will hold an (optional) extra-office hour on Tuesday April 8, 16h30-17h30, in room INF211, for last-minute questions before the midterm.
5. Stability of Nonlinear Systems (end)
6. Existence of Periodic Solutions in Planar Nonlinear Systems
- Course notes: Existence of Periodic Solutions in Planar Systems (File)
- Slides Stability of Periodic Solutions in Continuous-time Systems (File)
- Exercise Set 7 (File)
- Solution of exercise set 7 (File)
Subjects covered during week 10:
Transcritical bifurcation in dimension 1.
- Correction of midterm
- Local and Global Stability of Non-linear Systems.
- Course notes: Bifurcations (File)
- Slides bifurcation (Part 1) (File)
- Exercise Set 8 (File)
- Solution of Exercise set 8 (File)
- Slides correction Midterm 2025 (File)
- Transcritical bifurcation in dimension 1.
- Pitchfork bifurcation in dimension 1.
- Flip bifurcation in dimension 1.
- Andronov-Hopf bifurcation in dimension 2.
- Existence of periodic solutions
- Stability of periodic solutions
Subjects covered during week 12:
8. Introduction to chaos
- Property 1: Irregular and aperiodic trajectories
- Property 2: Sensitivity to initial conditions
- Elements from the theory of ergodic dynamical systems: probability space, measurable and measure-preserving transformations, ergodic transformations.
- Lyapunov Exponents.
- Bifurcations
Subjects covered during week 13:
8. Introduction to chaos
Sharkovskii's theorem
Exercises:
- Elements from ergodic theory.
- Course notes: Chaos (File)
- Slides Chaos (File)
- Exercise Set 11 (File)
- Solution of Exercise set 11 (File)
- Lyapunov exponents by Anna Rapoport (File)
Program for week 14:
8. Introduction to chaos (End, Only 1 hour 8h15- 9h00)
Property 3: Presence of a dense set of unstable periodic solutions.Symbolic analysisExercises (from 9h15)
- One-dimensional maps and chaos.
- Final exam of previous years (note: the material is expanded this year, as the course moved from 4ECTS to 6ECTS).
- Exercise Set 12 (File)
- Solution of exercise set 12 (File)
- Continued Fractions and Chaos by R. M. Corless (File)
- Sample Final Exam Part A (Closed Book Part) from Previous Year (File)
- Sample Final Exam Part B (Open Book Part) from Previous Year (File)
- Sample: Final Exam Part A (Closed Book Part) from Previous Year: Solution (File)
- Sample Final Exam Part B (Open Book Part) from Previous Year: Solution (File)
- Another Sample Final Exam Part A (Closed Book Part) from Previous Year (File)
- Another Sample Final Exam Part B (Open Book Part) from Previous Year (File)
- Another Sample Final Exam Part A (Closed Book Part) from Previous Year: Solution (File)
- Another Sample Final Exam Part B (Open Book Part) from Previous Year: Solution (File)
Additional office hours in case of a (very) last-minute question
- Friday June 17: Room BC 329, from 8h30am until 10am.
Final exam: Monday June 20 15:15 - 18:15, Room CE 1 106. The exam (max 80 points) covers all the material seen in class during the semester and is made of two parts:
- the
first part (20 points) is completely "closed book" : no document is allowed. This
part will only have questions calling for a true/false answer with a
short justification.
- the second part (60 points) is partially "open book", but you may use only the extended class notes summary that will be handed in during the exam (it is the same summary as the one allowed for the midterm). No class notes, no exercise set, no solution of exercise sets, nor any other material are allowed.
A few video recordings are available on this channel, but the course format has evolved and these videos do NOT cover only a portion of the course material. They are NOT meant to replace the lectures.
Back up links (to stay hidden from students)
- This chapter is pre-recorded and available at the links Chap.1 - Introduction Part.1 and Chap.1 - Introduction Part.2.
Subjects covered during week 12:
7. Bifurcations
- Transcritical bifurcation in dimension 1. This part of the chapter is pre-recorded and available at the links Chap.7 - Bifurcations: Transcritical Bifurcation Part 1 and Chap.7 - Bifurcations: Transcritical Bifurcation Part 2 . Part
1 describes the general result on trans-critical bifurcations, it
includes some rather tedious technical details explaining the change
coordinates to simplify the Taylor expansion of F(x,\mu), which may be
skipped (they are not in the class notes) but which I left in the video
so that you get the detailed computations. Part 2 covers an example of application to SIS epidemics.
- Pitchfork bifurcation in dimension 1. This part of the chapter is pre-recorded and available at the link Chap.7 - Bifurcations: Pitchfork Bifurcation. There
is a sign mistake in the computations I do for "case 2" from time 18:32
until 21:00 (notice my hesitation at 18:32). While deriving this case
on the lower blackboard, I pointed to the wrong Jacobian for the
equilibrium points on the upper blackboard. Therefore the sign of these
Jacobians, and hence the stability of the equilibrium points, should be
flipped.
- Flip bifurcation in dimension 1.
- Andronov-Hopf bifurcation in dimension 2.
- Both zoom recording are available here
- Existence of periodic solutions
- Stability of periodic solutions
Extra Office hours:
- Thursday June 22, 14h00-15h00, Room BC 229
- Friday June 23, 11h00-12h00, Room BC 229