moorepants
commented
6 years ago Notes take by Jason (and others?) while chatting with Shubankar:
- only saw design in the milineimum bridge in the homework and in project. should have gotten to taipei notebook, would have brought more deisgn into class. walk through in class would have been helpful,they need to see how real engineers make decisions. need us to do design problems in class as demos
- students that finish in class exercises early get bored and look at other things on the internet (pair programming?)
- students shy about asking kenny or me to come over (much more comfortable asking nearby student)
- novel experience to have TA in class that can ask questions
- never had live exercises in class
- use the exercise method sin “workload” classes and physics discussions
- rossler hall first floor has room full of boards for discussions
- linear algebra makes it really intense, never understood why modal analysis was important
- didn’t know why the modeshapes needed to be visualized
- could we do a design problem that motivates the need for modal analysis
- need something that adds in specifics of things like “Use langrage method to model multi dof planar systems”, the main learning objectives
- some systems were not exciting: for example the book on the cup was not exciting, pony tail of runner was good because it was a weird thing (not only one answer) with weird chaosy graphs, shubankar like the inverted pendulum cause you just learned to model and could apply it to this system
- didn’t have the washing machine before the homework on quartercar
- thought everyone would have same unsteady behvioar in the ponytail one was confusing but learning exprience on chaos
- shubankar liked lagrangians and sympy the most in the class, lagrangians gave huge confidence
- thought fourier transforms were super useful (was able to apply to other classes)
- project was fun because it was a real problem, could change the road whatever you wanted. gave satisfication that you actually made something
- lagrangians, python, sumpy, fouier transforms
- two occasions: first time i spoke about transmissible he missed it because he was behind, didn’t get the last bicycle plot fro same reason, basically because he was behind in the exercise
- sometimes i wouldn’t explain the solutions to the exercises
- (So students would keep working while lecture continued)
- the exercises seemed more like exercises in python but the output was useful to think about
- could add exercises that aren’t just python, explain things
kenny: lots of work on board, need vinod posts a skeleton of the notes and would fill it in on the tablet (but in ben’s and kenny’s folks didn’t like that) need to figure out surface notes and so students can take notes need better classroom shubankar would never add notes to the jupyter notebook (the notebook) we have a mismatch in that we want a book and that we need something that works for class
Stated Objectives:
Overall course premise and top level learning objectives (see syllabus https://moorepants.github.io/eng122/ for objectives)
Review of the three portions of the class: 1) analysis, 2) modeling, 3) design
Review of each class notebook
NB 2
How does inertia relate to periods? (i.e. using a vibrational concept to infer a physical property of a system) Given a file with data, curve fit a mathematical model to it.
NB 3
Effect of damping on a system. Damping regimes. Log decrement. Stated objective but not addressed: how does natural frequency relate to mass/inertia or stiffness. Center of percussion.
NB 4
State the three fundamental characteristics that make a system vibrate (not addressed). Identify damping regime by looking at free response. This notebook repeats a lot with notebook 3.
NB 5
Non-linear pendulum introduced. The idea of small-angle approximations demonstrated very well. Sort of the first brush with linearization. Also added damping and tried curve fit. I remember having an issue with this notebook early on where we struggled with some notation used for Coulomb friction.
NB 6
Forcing at/below/above natural frequency. Natural frequency defined explicitly for the first time, ought to have happened in NB 3. This notebook had alignment issues. Cells were misaligned for a lot of people causing them to fall behind while the class moved on. Frequency response and phase shift plots introduced but I remember not understanding phase shift very well until much later when I studied it for the project by myself. Never used autocorrelation to determine period although the local objectives said we would. Also, did not explicitly see time series introduced.
NB 7
Stated objectives don’t do justice to this NB. We learned a lot more than what was stated. Also, transmissibility could be more elaborately taught here. The penny dropped for me when I worked on transmissibility for the project, not when it was taught in class here. Extremely useful Fourier expansion was taught here. In addition, Sympy was introduced. Sawtooth example used and quarter-car forced.
NB 8
This NB was the first time in the course that we collectively modeled a system in class. The Lagrangian was introduced. A lot of the work was done on the blackboard/surface but the notes weren’t uploaded. It would have been better to stick to the surface rather than split screens with the board. Simulation of the non-linear model was introduced using SingleDoFNonLinearSystem(). eval_rhs was hard to understand. Linearization using small-angles was introduced. Comparison against the linear system was made. The NB does not have stated objectives.
NB 9
This NB was not worked on in class. It ought to have been considering it is the only time we are exposed to the Lagrangian of the second kind, a concept that was used in the homework for that week. Other students (Nic) set up the DE using Newton’s laws which is fine but doesn’t provide an opportunity to use the power of the Lagrangian. The coordinates in the washing machine model are a little hard to understand as well, since they are adjusted around the static equilibrium, a concept we didn’t get to in class until NB 10. No stated objectives.
NB 10
No stated objectives. Again, a lot worked out on the surface and board. Especially the matrix math could use a nice LaTex based guide. For instance, this NB forced me to mindlessly use the code in it, which would have been fine had I known what the code did. eg. Jacobian to linearize was used but the matrices lesson did not teach me very well why it worked. The state-space model is tricky for folks without controls experience. I guess the NBs could be illustrated with graphics to show the stuff that we did on the board. L2K used.
NB 11
Identically named as NB 10. Expands the modeling from NB 10 to introduce modal analysis.
NB 12 / NB 13
Introduce the modes of a vibrating building. These notebooks did a good job of teaching me that the final response of a system is a linear combination of its modes. I did, however, have trouble with understanding concepts like the Cholesky decomposition, spectral matrix etc. Visualizing the modes helps understand what was added to the mix, but I am not sure why that is important. NB 13 adds forcing. Poke the building at A and see what happens. Poke it at B and see what happens.
NB 14
A good notebook to generalize the ideas from the state-space model to a real complex system. Did not understand the utility of the phasor plots. In general, starting NB 10, I felt disoriented with the math in the class. Relating the ideas from the state-space model to their physical analogs was hard for me. Why are modal shapes important? What exactly do eigenvectors say? What does the last plot with the ‘X’ shaped curves say physically?
Review of the homeworks