Professor Ross -- Great videos and lecture notes. I took Professor Kane's dynamics courses at Stanford many years ago(1986). I think after all these years it is great to see your lectures and enhance my appreciation and understanding of three -dimensional rigid body motion. Thank you very much.
Very cool! I'm glad the videos are helping your appreciation of 3D rigid body mechanics -- it's a fascinating subject. I have another series of lectures that cover this at the Lagrangian level as well, where I also cover Kane's Method: th-cam.com/video/ooS6RHBk5y4/w-d-xo.html
In short, yes. ErrorPhiDeg, at 41:43, is a single number that represents the error of our spacecraft attitude estimate. It is the Euler principal rotation angle between the true [BN] matrix and our estimated [BN] matrix, based on imperfect (noisy) measurements. In the made-up example, we 'secretly' know the true attitude of the spacecraft from the beginning, at 34:26 so we have a benchmark to compare to (which would not be the case in a real-life situation). We could also describe the error between the true [BN] matrix and our estimated [BN] matrix in terms of yaw, pitch and roll angles (which would all be small, around 1 deg), but my approach is to summarize with one number. Best would be ErrorPhiDeg = 0 deg and worst would be ErrorPhiDeg = 180 deg.
I’m working with a satellite system that is currently fielded and am trying to understand some phrases and get some definitions. What is “Incident” and “coincident”? The sensors are also not on a fixed or tidally locked vehicle but one that is in a rotisserie. So the sun only passes over the sensor once per rotation and measures an aspect angle.
Sorry if this is a little late, but the incident angle is the angle the target (like the Sun, for example) makes with the direction normal to the sensor. So for example, if the flat sensor is "looking" directly at the sun, the incident angle is zero degrees. As the Sun drifts out of the sensor's field of view, the angle decreases.
It's from Chapter 4 of "Introduction to Attitude Dynamics and Control", by Christopher Hall. It's based on a 1995 article, so the accuracies may be out of date. You can find the chapter and table here: dokumen.tips/documents/chapter-4-attitude-determination-virginia-cdhallcoursesaoe4140attdepdf4-2.html?page=8
If I want to introduce some "real error" based in the sensor accuracy ranges, what could I do? I am getting sun and magnetic measurments from STK, but I want to introduce some error.
Here's a procedure: You could take, for example, the "true" sun vector as seen the spacecraft frame, what I call s_B_true at 35:26, and you could pre-multiply that by a 3x3 rotation matrix, C_error, which is a random small rotation. For instance, choose a yaw, pitch, and roll each from a random uniform distribution in the range -1 deg to 1 deg, or you could take them from a gaussian distribution. In any case, from that, you get your 3x3 matrix C_error. You could the use as your simulated erroneous measurement, s_B = C_error*s_B_true. Note that if the yaw, pitch, and roll where all zero, then C_error = 3x3 identity, and so s_B = s_B_true, but because you have small random values for yaw, pitch, and roll, s_B will be slightly different from s_B_true.
Professor Ross -- Great videos and lecture notes. I took Professor Kane's dynamics courses at Stanford many years ago(1986). I think after all these years it is great to see your lectures and enhance my appreciation and understanding of three -dimensional rigid body motion. Thank you very much.
Very cool! I'm glad the videos are helping your appreciation of 3D rigid body mechanics -- it's a fascinating subject. I have another series of lectures that cover this at the Lagrangian level as well, where I also cover Kane's Method: th-cam.com/video/ooS6RHBk5y4/w-d-xo.html
Thank you very much sir. This is an extremely helpful video!
You're welcome. I hope your spacecraft studies go well!
Genuinely this was so helpful, this method of explaining it was so much better than what I was originally told. Thank you so much
I'm so glad!
Thank you for that clear explanation, it will be useful!!! Merci
Dear Dr Ross, Thank you very much for providing such useful information on youtube
So nice of you
Hello professor, does the ErrorPhiDeg means something physically? Like the angle between both rot mat for example?
In short, yes. ErrorPhiDeg, at 41:43, is a single number that represents the error of our spacecraft attitude estimate. It is the Euler principal rotation angle between the true [BN] matrix and our estimated [BN] matrix, based on imperfect (noisy) measurements. In the made-up example, we 'secretly' know the true attitude of the spacecraft from the beginning, at 34:26 so we have a benchmark to compare to (which would not be the case in a real-life situation). We could also describe the error between the true [BN] matrix and our estimated [BN] matrix in terms of yaw, pitch and roll angles (which would all be small, around 1 deg), but my approach is to summarize with one number. Best would be ErrorPhiDeg = 0 deg and worst would be ErrorPhiDeg = 180 deg.
@@ProfessorRoss got it, thank you professor!
This was very helpful!
Glad you think so!
I’m working with a satellite system that is currently fielded and am trying to understand some phrases and get some definitions. What is “Incident” and “coincident”? The sensors are also not on a fixed or tidally locked vehicle but one that is in a rotisserie. So the sun only passes over the sensor once per rotation and measures an aspect angle.
Sorry if this is a little late, but the incident angle is the angle the target (like the Sun, for example) makes with the direction normal to the sensor. So for example, if the flat sensor is "looking" directly at the sun, the incident angle is zero degrees. As the Sun drifts out of the sensor's field of view, the angle decreases.
Hello, frome which book is the table seen in 22:50?
Great content!
It's from Chapter 4 of "Introduction to Attitude Dynamics and Control", by Christopher Hall. It's based on a 1995 article, so the accuracies may be out of date. You can find the chapter and table here: dokumen.tips/documents/chapter-4-attitude-determination-virginia-cdhallcoursesaoe4140attdepdf4-2.html?page=8
@@ProfessorRoss Thank you so much Professor!
2013 version of mathlab is not supporting please help me out
If I want to introduce some "real error" based in the sensor accuracy ranges, what could I do?
I am getting sun and magnetic measurments from STK, but I want to introduce some error.
Here's a procedure: You could take, for example, the "true" sun vector as seen the spacecraft frame, what I call s_B_true at 35:26, and you could pre-multiply that by a 3x3 rotation matrix, C_error, which is a random small rotation. For instance, choose a yaw, pitch, and roll each from a random uniform distribution in the range -1 deg to 1 deg, or you could take them from a gaussian distribution. In any case, from that, you get your 3x3 matrix C_error. You could the use as your simulated erroneous measurement, s_B = C_error*s_B_true. Note that if the yaw, pitch, and roll where all zero, then C_error = 3x3 identity, and so s_B = s_B_true, but because you have small random values for yaw, pitch, and roll, s_B will be slightly different from s_B_true.
@@ProfessorRoss Thanks professor Ross!