I am trying to find the lengths of one side of a non parrallel four bar linkage. Currently I am fiddleing with a couple pieces of erector set (I don’t have a personal vex kit) and drawing pictures in a notebook. What Grant High School Lancers did for the Peaucellier linkage seems to be a faster and more accureate method. How do I preform geometry optimization in Exel? Thanks
Good question. I posted the excel Peaucellier and I do most of my 2D work using its graphics capability. I use it basically as a ruler and compass to draw loci of line end points and then determine where they intersect to give me the geometric solution. Excel uses the same MS shape commands as other programs such as Power Point and Word. The key is to use the **formatting capabilites **for each shape object added. I typically select a convient scaling for the shape and this allows good relative scaling of many objects contained on a robot. Once you have a subsystem drawn then you just group the shapes and you have a mechanism that can now be moved or rotated.
I find it most useful when determining arm geometry. After I draw the arm, I group the shapes. Then I draw a few game objects and goals which allows me to easily determine whether the arm reach is adequate. There are many tutorials online re Excel shapes. Just search GOOGLE on Excel shape tutorials , maybe youtube also.
For a 4 bar with different lengths A,B,C and D and vertices AB,BC,CD,AD. Draw a line to set the position of the base link , A. Lets say its vertical with end point AB on top and end point AD on the bottom. Centered on point AB, draw a circle with radius equal to the length of the bar B. Repeat for the bar D that attaches to point AD. So you now have the base bar A with a circle on each end. Next simply draw another circle with radius equal to the length of C bar and using the click and drag function , move the center of this circle onto any point of the B radius circle. This point will be the BC vertex. The point where the C circle intersects the D circle becomes the CD vertex. You now have all points of the linkage. This is a little slow but works great.
Other examples of how I use excel in Robot design:
Vex Gateway:http://dl.dropbox.com/u/17455717/Gateway2011.xls
Vex Roundup http://dl.dropbox.com/u/17455717/grant%20round%20up%20design.xls
FRC Lunacy http://dl.dropbox.com/u/17455717/Lunacy%20Robot%20Geometry.xls
There are of course linkage simulations which you can purchase and even try out with 30 day demos.
Cinderella
CH. Mechanism 2.5
Any program that can do vector simulation
3D modeling programs with simulation capability (Autocad, Solidworks etc)
Thanks, I have turboCAD. I understand what you did now.