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  • Users: brango
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  1. brango

    Interfacing ANSYS with MATLAB

    Hello, I previously, interfaced ANSYS and MATLAB. I used finite element code in MATLAB for a certain design. After optimizing the design in MATLAB, I saved the results (thickness of each element) in a .dat file, and using APDL, I read that file and constructed the same design on ANSYS to...
  2. brango

    stiffness matrix is not positive definite

    yes it does because my upper bound is 3mm which isnt huge. So im dealing with small numbers. 1e-7 gives me a very good ratio of Output displacement/Input displacement which is around 14, 1e-10 gives me approx. dout/din = 22 which is much better than 14, if it wasnt for the warnings. Still 14 is...
  3. brango

    stiffness matrix is not positive definite

    I am using the MATLAB function FMINCON for optimization. As I mentioned earlier, upper bound is 3mm. Lower bound is 1e-7m or 1e-10m. Why is it not practical ? I want something that resembles 0 and has no effect on my design. Thank you.
  4. brango

    stiffness matrix is not positive definite

    To think of it now, I think you are right rb1957. The warnings appears once in a while after several generation runs, and therefore it must be the case that the optimizer is going too far, but then it is discarding those results. If this is truly the case, then I think there should be no...
  5. brango

    stiffness matrix is not positive definite

    Thank you all for your replies. First, I am saying I still get good results because the objective of my optimization is to maximize my output displacement and minimize the input displacement of my compliant gripper (Maximize Dout/Din). I get a larger ratio when I use 1e-10 as my lower bound...
  6. brango

    stiffness matrix is not positive definite

    Hello, I am working on optimizing a compliant gripper. I use 2d plane frame static analysis code. I have around 50 elements, and I am using Genetic Algorithms with thickness as the variable to be optimized. So, the code will find the best 50 thicknesses for my best gripper design. After I get...
  7. brango

    Minimizing a function

    Hello, If I have a function called Myfunc, and I want to minimize it. I am trying: [X fval] = fminsearch(@Myfunc, X0) It minimizes the result, but everytime I run it again it gives me a lower value. So im not reaching the local minimum. I tried [X fval] = fminunc(@Myfunc, X0), but the...
  8. brango

    Reducing the time for MATLAB code

    Hello. Yes, the functions Im using arent built-in. What I wanted to know is whether the time taken for "other lines and overhead" can be reduced or no. I dont even know what overhead is. It is taking %87 of the function time. Thanks.
  9. brango

    Reducing the time for MATLAB code

    Hello, Thanks for your reply. 35 secs for running the function once. The code runs 200 times in order to perform optimization, and each time it runs the function itself gets called more than once. So 35 secs which initially seems a very small time becomes 35secs x 200 x no. of calls per 1...
  10. brango

    Reducing the time for MATLAB code

    Hello, I am working on a code on MATLAB 7.0. It takes me about 5 hours for my program to run once. I am working on optimization, so I have some functions that are called thousands of times. I read about vectorizing the code, but im dealing with sophisticated loops and im not sure if they can...
  11. brango

    2D plane frame elements with different thicknesses to model a gripper

    Thank you for your willingness to help me. Yes, I am a beginner in ANSYS. I checked some tutorials but theres nothing similar to my application. I found typical problems like a truss structure. Also, I tried to search for tutorials on APDL, but i mostly found documentations that tell you what...
  12. brango

    2D plane frame elements with different thicknesses to model a gripper

    Hello, I tried the code but it didnt work. It tells me: "R is not a recognized BEGIN command" Please can you further explain ? Thank you.
  13. brango

    2D plane frame elements with different thicknesses to model a gripper

    Hello, I am working on a compliant gripper. I optimized the gripper for maximum displacement using MATLAB. The optimized parameter is the thickness of each element. I am having trouble modeling it with ansys. I have around 54 elements. I tried at first to create 1 plane82 element type and...
  14. brango

    How to model beam elements with different thicknesses

    Thank you for your help. I had no idea I could write code with ANSYS. I will give it a try. Thanks again.
  15. brango

    How to model beam elements with different thicknesses

    Hello, I have a system that I want to model as 2D beam elements. I already tried to model it, but I found out I can only specify one thickness for all the elements of "beam" type. The problem is that each element in my system has a different thickness. So, how can I resolve this issue ? Do I...
  16. brango

    Compliant Gripper in ANSYS

    I forgot to mention, an example of a gripper design is provided in the attachment of the previous post. The input forces can be shown equal to 100N each (force from human grip). And the output is at the spring (node 25). Thank you.
  17. brango

    Compliant Gripper in ANSYS

    Hello, This is my first post. Sorry if im posting in the wrong place, but I didnt know how to find an ANSYS forum. I need to model a compliant gripper with ANSYS. I got a set of optimum thicknesses (the best thickness for each element) which would produce maximum displacement at the output of...

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