Dear Mr. Fu-Kwun Hwang, I have just subscribed for your forum. Thank you. I am looking for a suitable Java applet which can simulate gimbal movements. I need such a simulator to study the movement of HIV (the virus causing AIDS) when reaching close to the target cell (CD4+ T cell). Some information on our research and personal details as well you can obtain visiting my site included in my address at the bottom. I have tried to find such Java software in your site and the links there but I failed. In this regard I would greatly appreciate if you be so kind as to create and provide me with such simulator. Please have some ideas of the design (actually the layout) at the links below.

Thanking you very much in advance I am, Sincerely yours, Evgeni Gabev.

My address: Assoc. Prof. E. Gabev MD, PhD Institute of Experimental Pathology and Parasitology, Bulgarian Academy of Sciences, Acad. G. Bontchev street, Bl. 25, Sofia 1113, Bulgaria. email: egabev@gmail.com Internet site: http://sites.google.com/site/gabevshivaidstreatment/ Telephone: +3592/9792325, Fax: +3592/8710107. The simplest ideas are always the hardest to come up with.

I need to have a physics model in order to create the simulation.

Do you have the model in mind?

I found some model at http://epubl.ltu.se/1653-0187/2007/086/LTU-PB-EX-07086-SE.pdf Does the model in that pdf fit with your need? You also need to provide values for all the parameters so that the simulation can fit with the need of your system.

I need to have a physics model in order to create the simulation.

Do you have the model in mind?

I found some model at http://epubl.ltu.se/1653-0187/2007/086/LTU-PB-EX-07086-SE.pdf Does the model in that pdf fit with your need? You also need to provide values for all the parameters so that the simulation can fit with the need of your system.

Dear Mr. Fu-Kwun Hwang, Thank you very much for your reply and for your efforts to find a model for my gimbal request to you. Actually I need something more simple than that in the Masters Thesis (the .pdf file you sent to me). This is actually a gimbal with a gyroscope inside for the purpose of stabilization some systems, e.g.digital moove cameras etc. I need just a 3 circle gimbal (no gyroscopeinside) with one common axis (please see the attached figures) and to have the ability to move them independently having a meter for the rotation angle. Here below is a model which is OK for me but as you can see I can not use it. http://www.eng.auburn.edu/users/jzd0009/matlab/doc/help/toolbox/physmod/mech/gimbal.html The controls I need are: Start/Stop, Restart, Reset and the most important is the ability to rotate and to position the 3 circles as it is shown on the attached pictures. Please use the words Pitch, Roll and Yaw as they are written on the pictures for the type and direction of the rotation. The mathematics is given at: http://en.wikipedia.org/wiki/Gimbal_lock Please note that I am not a mathematcian and might be I am wrong giving you this matrices. Wishing you a nice weekend I am with kindest regards. PS. I will of course site your name and site in my publications using your applet.

Let me make sure one thing: Please provide the following information:

1. Dimension of the system (at least r1,r2,r3) 2. Does the outer most one can only rotate in YAW AXIS? 3. Is it a static system, only need to be able to set the angle for Pitch, Roll and Yaw angle? Or there is(are) initial angualr velocity for a dynamic system? What are those values? What are the differential equations according constraints for your system.

Because I have never play with such device before, I do not have any ideas about the physics model (constraints) for the system. I need physics model to create the simulation.

The rotation axes for the following two images are not the same. Which one is similar to your gimbal?

Dear Mr. F-Kwun Hwang, Huge thanks for the static version of the gimbal applet. That is exactly what I need for doing my research. I actually do not need animation. But I would like to ask you to add the following opportunities:Independent moving of each circle (Roll, Jaw and Pitch) without driving the others. Also please make the rotation angels of the same circles measured in degrees and please put 3 indicators to display the degree of rotation of each one. I also need that it will be possible to work with only 2 of the circles let say just Yaw and Pitch for example.The 3rd could be made (temporary) disabled and invisible from the applet by some kind of a button. This ability should be possible for each one of the 3 circles one each at a time by choice of the opperator. Actually I would like to investigate when a gimbal lock will appear with 2 and/or 3 circles in different experiments.

The gimbal lock on my humble oppinion is a constrain of the gimbal toolls at all. The equasions of the so called gimbal lock and detailed explanation of this phenomenon are given at the following sites ordered by importance:

Please excuse me that I can not give you a physics model and other constraint mathematics but I am a medical doctor and have only basic knowledge on that matter obtaining from the Internet sites. That is the reason of my request because I can not make such an applet by myself despite the EJS. I can just opperate it. Here are my answers of you questions below: 1/,The dimension of the system shoud be in degrees not in radians or arbitrary units 2/. Yes all 3 circles Yaw, Roll and Pitch should rotate in their one axis without moving the other one i.e. when I rotate the Pitch the Jaw and Roll should not move. Then I will need to rotate the othe 2 one at a time with changin the position of the rest circles. The axes should be perpendicular each other. 3/. This static applett is OK with my work. 4/. The left hand picture is my gimbal (the blue one). The animated one is not correct for my purposes.

Thanking you very much again for your time and efforts I am, With kindest regards, Evgeni.

Let me make sure one thing: Please provide the following information:

1. Dimension of the system (at least r1,r2,r3) 2. Does the outer most one can only rotate in YAW AXIS? 3. Is it a static system, only need to be able to set the angle for Pitch, Roll and Yaw angle? Or there is(are) initial angualr velocity for a dynamic system? What are those values? What are the differential equations according constraints for your system.

Because I have never play with such device before, I do not have any ideas about the physics model (constraints) for the system. I need physics model to create the simulation.

The rotation axes for the following two images are not the same. Which one is similar to your gimbal?

Dear Mr. Fu-Kwun Hwang, I can not open the file ejsuser/2/ejs_glimbal3.jar not found Please advise me how to proceed. Could you please make the new applet visible.Thank you. With best regards, Evgeni.

Thank you very much again. That is really the applet I need. You and your team are very, very kind and are superior experts in programming. I wish you, your familly and your team all the best during the New 2011 Year.

May I ask you kindly to update the gimbal java applet as such that the Roll ring (blue) is rotated accorging to the Roll of the figure from the attached file. At present it is rotated as the red one (Yaw) of your applet. Thanking you very much in advance I am, Sincerely yours, Evgeni Gabev.

There were two simulations created, are you asking for the third one?

Or you want to modify one of them? May I know which one: message #4 or message#6?

I would like that you modify the applet on message #6. Just the blue ring rotation. Thank you.

Dear Professor Fu-Kwun Hwang, I would like to asking you very kindly to modify your aplet (message #6) such that the blue ring (roll) rotates like as at the attached file direction (arrow) from today, i.e. different than the red (Yaw) and green (Pitch) one. I would greatly appreciate your efforts since I need your aplet for very serious research-a new drug for AIDS we have created in the Institute. If you agree I will give credits for your labor in the paper I am preparing at present. Thanking you very much in advance I am with kindest regards.

There were two simulations created, are you asking for the third one?

Or you want to modify one of them? May I know which one: message #4 or message#6?

I would like that you modify the applet on message #6. Just the blue ring rotation. Thank you.

Dear Professor Fu-Kwun Hwang, I would like to asking you very kindly to modify your aplet (message #6) such that the blue ring (roll) rotates like as at the attached file direction (arrow) from today, i.e. different than the red (Yaw) and green (Pitch) one. I would greatly appreciate your efforts since I need your aplet for very serious research-a new drug for AIDS we have created in the Institute. If you agree I will give credits for your labor in the paper I am preparing at present. Thanking you very much in advance I am with kindest regards.

Dear Professor Fu-Kwun Hwang, I apologize for bothering you again. I understand that you are very busy and are not able to modify the applet from #6 at that time. I have downloaded and installed EJS and try to work it out the problem but failed. Would you please be so kind as to give me your instruction steps and advice how to do it. I need just to change the rotation axes of the Roll (blue ring) as to be different than the other 2 (Yaw and Pitch). I beg you very kindly. Thanking you very much in advance I am, Sincerely yours. Evgeni Gabev.

I am sorry that I was not able to help you during the last few weeks. It was near the end of semester and there are many duty need to be carry out. I will have more free time during the summer. I will try to help when I am free.

Many, many huge thanks Dear Professor Fu-Kwun Hwang for your kindness. I will be waiting for your answer and help at your convenience. With best regards, Evgeni Gabev.

OOps! It was a upload mistake. The problem has been fixed. You should be able to view the simulation now.

Many, many warm thanks dear Professor Fu-Kwun Hwang. This is exactly what I need. The added arrows are really very helpful. When I will be ready with my new paper I will send you an email and if you are agreed I will acknowledge your work. I will cite your applett in my paper to your name, title and University address. Thanking you very much again I am with kindest regards and wishes for all the best. Evgeni Gabev.

OOps! It was a upload mistake. The problem has been fixed. You should be able to view the simulation now.

Many, many warm thanks dear Professor Fu-Kwun Hwang. This is exactly what I need. The added arrows are really very helpful. When I will be ready with my new paper I will send you an email and if you are agreed I will acknowledge your work. I will cite your applett in my paper to your name, title and University address. Thanking you very much again I am with kindest regards and wishes for all the best. Evgeni Gabev.

OOps. I have just mentioned that PITCH (the green circle) does not moving. I would like to beg you to make it to move as at the #6 above. Other circles (Roll and Yaw are OK). Please look at the bolted (pivoted) points at #4 figure (left static gimbal). Thank you very much in advance.

The green circle moves when pitch value change (when you drag slider). The rotating axes is the green arrow.

Do rotational axes for raw,pitch and yaw are three orthogonal axes? Please let me know the rotational axes for the pitch rotation you want.

Yes. Rotational axes for roll, pitch and yaw are 3 orthogonal axes or let say perpendicular to each other. Please make analogy with the airplane movings (attachments). Pich is simple up and down the nose of the plane; roll is wings up and down; yaw is rotation arround the vertical axis. Pitch is X axis; Yaw is Z and Roll is Y. I hope this will be helpful. Please note that my geometry is at the level of Medical University which is quite basic. I was waiting all the night at my office for your reply. Many thanks for your kindeness to reply very quickly.

Please have the second attachment (more clear view of the axes PRY). It was failed to appear by my previous submission.

The green circle moves when pitch value change (when you drag slider). The rotating axes is the green arrow.

Do rotational axes for raw,pitch and yaw are three orthogonal axes? Please let me know the rotational axes for the pitch rotation you want.

Yes. Rotational axes for roll, pitch and yaw are 3 orthogonal axes or let say perpendicular to each other. Please make analogy with the airplane movings (attachments). Pich is simple up and down the nose of the plane; roll is wings up and down; yaw is rotation arround the vertical axis. Pitch is X axis; Yaw is Z and Roll is Y. I hope this will be helpful. Please note that my geometry is at the level of Medical University which is quite basic. I was waiting all the night at my office for your reply. Many thanks for your kindeness to reply very quickly.

Please have the second attachment (more clear view of the axes PRY). It was failed to appear by my previous submission.

I think it is the naming convention that needs to be standardized tho the plane's picture. i change it for your convenience. is that closer to what you need egabev?

Please feel free to post your ideas about how to use the simulation for better teaching and learning.

Post questions to be asked to help students to think, to explore.

Upload worksheets as attached files to share with more users.

Let's work together. We can help more users understand physics conceptually and enjoy the fun of learning physics!

to view it. ***

author: Fu-Kwun Hwang, slightly edited by lookang changes made. naming convention change to suit airplanes as in picture made 19 closest instead of 361 set initial values to all zero range of slider -180 to 180 degree added play pause button axes implementation added instead of box for clearer orientation when talking about pitch roll and yaw

The green circle moves when pitch value change (when you drag slider). The rotating axes is the green arrow.

Do rotational axes for raw,pitch and yaw are three orthogonal axes? Please let me know the rotational axes for the pitch rotation you want.

Yes. Rotational axes for roll, pitch and yaw are 3 orthogonal axes or let say perpendicular to each other. Please make analogy with the airplane movings (attachments). Pich is simple up and down the nose of the plane; roll is wings up and down; yaw is rotation arround the vertical axis. Pitch is X axis; Yaw is Z and Roll is Y. I hope this will be helpful. Please note that my geometry is at the level of Medical University which is quite basic. I was waiting all the night at my office for your reply. Many thanks for your kindeness to reply very quickly.

Please have the second attachment (more clear view of the axes PRY). It was failed to appear by my previous submission.

I think it is the naming convention that needs to be standardized tho the plane's picture. i change it for your convenience. is that closer to what you need egabev?

*** Click

[ejsapplet]

to view it. ***

author: Fu-Kwun Hwang, slightly edited by lookang changes made. naming convention change to suit airplanes as in picture made 19 closest instead of 361 set initial values to all zero range of slider -180 to 180 degree added play pause button axes implementation added instead of box for clearer orientation when talking about pitch roll and yaw

Thank you very much for your efforts to modify the applet. It is really going closer to my needs. I beg you just 1 thing. You are correct. Roll (green circle) is rotating but arround its circumference. Thus it simulates the so called gimbal lock (see http://www.youtube.com/watch?v=rrUCBOlJdt4) I beg you very kindly to make the rotation of Roll such as its cross section to rotate instead just as the Roll at the picture on message #4 above. Also please make back the rotation from 0 to 360 degrees instead of +/- 180 degrees since I have to check combinations of virus (HIV) position such as Yaw 300 degrees, Roll 180 and Pitch 120 degrees. Thanking you once more I am with most firendly and warmest regards. egabev.

Gimbal Model by Hwang Fu-Kwun and remixed by lookang changes made: re-design the implementation to suit the physical Gimbal with support structures represented by cylinders using the 3D group method to ease the need to program in the codes as it is the outer ring's motion is automatically translated to the middle ring and the middle ring motion translation to inner ring. add cylinders to aid the visualization of the support of the Gimbal

made it animate and the slider values follow the motion now generated using ejs 4.2.7 load in MacOSX as the ejs4.3.3.2 didn't load in MacOSX.

the physics looks wrong though, see at the http://en.wikipedia.org/wiki/Gimbal. i suspect it is the inner ring that rotates in one direction, while the middle ring is coupled to inner ring and the outer ring is coupled to the middle ring. what you are think?

made it animate and the slider values follow the motion now generated using ejs 4.2.7 load in MacOSX as the ejs4.3.3.2 didn't load in MacOSX.

the physics looks wrong though, see at the http://en.wikipedia.org/wiki/Gimbal. i suspect it is the inner ring that rotates in one direction, while the middle ring is coupled to inner ring and the outer ring is coupled to the middle ring. what you are think?

Thanks again for your great attention to my research need of gimbal model. Yes you are correct. The model in the picture is not right. Sorry that I did not mentione it. I can immagine how many hours both of you spent on this project. I greatly appreciate all that and also think that adding the "cylinders" are very useful ldea of yourself. However, the three rings Roll, Yaw and Pitch should rotate independantly to each other. Your construction is quite sophisticated. I need actually more simple one as that at http://www.yb2normal.com/DIYsteadicam.html and the degree of freedom (actually mode of rotation of the rings) is given clearly at http://www.highballblog.com/2010/05/diy-glidecam-update-gimbal-handle.html Please look at the clip. Many thanks again and best regards. I hope you will be so kind as to modify your applet.egabev.

There are only two rotational axes for the device at the two URLs you have provided. The middle and outer rings can freely rotate along the same axes (with different angle). However, you have mentioned that those three axes should be perpendicular to each other. I am really confused!