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The Master version of this course will be Vision for Autonomous Robots, so the rest of the development can be followed on this labbook.
February 2, 2025
- Finished all lectures on Chapter 3, now time for the problem set.
- I like in Chapter 3.2 how the two constraint equations are slowly build up for the four wheel-types, I like from the EDX-lectures how they simplify the complex to simple equation of the fixed wheel. Maybe I should do both in my lecture: first build up slowly, thereafter break down again.
- I also like how the mobility comes from the rank of the constraint-matrix.
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February 1, 2025
- The lecture on stacking the rolling constraints and the sliding constraints gives different forms of maneuverability. The comparison of the omni-drive example and the two-steer example is quite intuitive: same movement, but more time is needed to get the wheels into position. (slide 12 vs 13)
January 31, 2025
January 30, 2025
- Finished, Create Symbolic Matrices tutorial, continue with Create Symbolic Matrix Variables.
- Next is Use Symbolic Objects to Represent Mathematical Objects, which is using inverse trigonometric functions as example. Alos include systems of linear equations.
- Continue with Perform Symbolic Computations. Not only partial differentiation is possible, but also integration.
- Last tutorial is Use Assumptions on Symbolic Variables.
- I created rotation matrices with symmatrix([cos(alpha),sin(alpha),0;-sin(alpha),cos(alpha),0;0,0,1]) (x-axis) and symmatrix([cos(beta),0,sin(beta);0,1,0;-sin(beta),0,cos(beta)]), but this doesn't pass the test (no feedback).
- Tried a Devanit Hartenberg representation, but now I got the feedback that a 3x3 matrix is expected.
- Tried again, but now without symmatrix. Get feedback that R_B1 is wrong. Should try other direction (direction of angle).
- Now I see the error, rotated around z-axis, instead of the x-axis. Still R_B1 is wrong.
- Looked at this example. No ',' where used.
- That helped, I only expected another sign for gamma in R_23.
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- Next assignment, I only have not seen the track to add another column to a matrix, so looking at video tutorial. Learned nothing new.
- Got a good hint from matrix in matlab.
- Looks all good, but I tried all 6 configurations, but r_3F_in3 stays wrong. Problem was that although I did subsitude, the class is still 'sym'. So, I first did tr_3F_in3 = [0 0 -l3]';, followed by r_3F_in3 = double(subs(tr_3F_in3,1)); (assume unit-lenght vectors).
- Next problems is that the Jacobian is defined with a function handle, trick was to convert to sym and also explcitly define the symbols for alpha, beta, gamma. Made a trivial implementation, by 8x code-repetition. The dr went down, until [0;0;0].
- The trajectory following makes a circle, but lags behind. Should use a PID, or watch the instruction-video again:
- Forgot to take the deltaT in acount (dr/dT), and to look at desired speed drGoal(t):
- Yet, this were all optional problems, so I finished 10% of the course but passing grade is still 0%. I finished Locomotion concepts, next section is Mobile Robot kinematics.
January 29, 2025
January 22, 2025
- On nb-dual I still have Matlab 2022a installed, although it have to be activated again.
- Activated it with my academic account.
- The symbolic toolbox was not installed, but I had that option. Could also upgrade to R2024b (not done yet).
January 17, 2025
- Explored the AMR at EDX already three times (2014, 2017, 2025).
- The 2017 progress was still 0%. 2014 is no longer working.
- Started with 2025 Introduction. They used three videos:
- So, all from the previous decade.
- Youtube gave me Inside the Lab: Taking Atlas From Sim to Scaffold (2024), which could replace the video Herke used.
- The introduction still used Lena (slide 7). The introduction focuses on three questions:
- Where am I?
- Where am I going?
- How do I get there?
- Followed by the see-think-act cycle. Each of the four components are shortly introduced.
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- Next is Locomotion. Next to the textbook, also the following material is mentioned:
- Part A, Chapter 1 (Kinematics) of
B. Siciliano and O. Khatib, Springer handbook of robotics, Part A, Chapter 1 Kinematics. Berlin: Springer, 2008.
- Chapter 3 (Kinematics) and Chapter 4 (Rigid Multibody Systems) of
H. Bremer, Elastic Multibody Systems, Springer Netherlands, 2008.
- The How to Engineer a Dog would also be nice for Behavior-Baed Robotics.
- I like the final wrap up of the first segment of Introduction to Legged Robotics by Marco Hutter (slide 9) - 4% completed.
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- I like the animations in slide 2 of Segment 2, which describes translation, rotation and screw motion.
- On slide 4 Tait-Bryan/Cardan angles (z-y-x) are defined (yaw, pitch and roll).
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- The 3rd segment introduces generalize coordinates, which contains the un-actuated base and actuated joints in one vector.
- Marco goes fast, but I found his 2nd working example nice, where he gives an example of the Jacobian for a simple 3-Link arm.
- I like the animation of slide 4 showing the different solutions of inverse kinematics.
- No guidance on how to use the symbolic toolbox of Matlab before the first problem. (7% completed)
- The material in this course is not explictly govered in the book. Check Herke's lectures.
January 16, 2025
- Checked the presentations of last year.
- First lecture is course logistics and legs vs wheels.
- Looked at the Links
- The book's webpage still exists, but Slides links is broken (since Nov. 2015)
- The EDX version of course still exists. Could still enroll. Material is mostly video's, problem sets and Quizes. Last update seems 2020. The problem sets are in Matlab. First problem is to define three rotation matrices for a single leg. Tried just to fill in rotx(alpha), but they want the symbolic equation. Nice, but that would require to do Get Started with Symbolic Math toolbox.
- The Videos page still works, but contains videos from 2010.
- Also the Links page still works, didn't check them.
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- The latest ETZH course is Spring 2021.
Previous Labbooks
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Labbook2008.html
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Labbook2007.html