wats wrong with tis prog? plz help!!!

This is a discussion on wats wrong with tis prog? plz help!!! within the C Programming forums, part of the General Programming Boards category; This is a program to find robotic arm inv kinematics. my doubt is not in kine:-). My program executes but ...

  1. #1
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    Unhappy wats wrong with tis prog? plz help!!!

    This is a program to find robotic arm inv kinematics. my doubt is not in kine:-). My program executes but always prints "position unacheivable", even for a known value, it does the same. here I have used radians for angles since thats what c understands. Please tell me how to come across this or even tell me better method to implement this. Thank you.

    insert
    Code:
        #include<stdio.h>
        #include<math.h>
        #include<conio.h>
        void main()
        {
            float a, b, c, d;
            int x = 0, y = 0, z = 0;
             int x1 = 0, y1 = 0, z1 = 0;
             int i = 0;
             printf("Enter X value: \n");
             scanf("%d", &x);
             printf("Enter Y value: \n");
             scanf("%d", &y);
             printf("Enter Z value: \n");
             scanf("%d", &z);
             for (a = -1.74 ; a <= 1.74 ; a = a + 0.02)
             {
                  for (b = 0.0; b <= 3.14; b = b + 0.02)
                  {
                       for (c = -1.74; c <= 1.74; c = c + 0.02)
                       {
                            for (d = -0.784; d <= 0.784; d = d + 0.02)
                            {
                                 x1 = (int)((11*cos(d+c+b+a)+11*cos(d+c+b-a)+12*cos(c+b+a)+12*cos(c+b-a)+9*cos(b+a)+9*cos(b-a))/2);
                                 if(x1 == x)
                                 {
                                         y1 = (int)((11*sin(d+c+b+a)-11*sin(d+c+b-a)+12*sin(c+b+a)-12*sin(c+b-a)+9*sin(b+a)-9*sin(b-a))/2);
                                         if(y1 == y)
                                         {
                                                 z1 =  (int)(11*sin(d+c+b) + 12*sin(c+b) + 9*sin(b));
                                                 if(z1 == z)
                                                 {
                                                       i = 1;
                                                       goto status;
                                                  } 
                                         }
                                  }
                           }
                     }
                }
           }
        status:
        if(i == 0)
        printf("*****Positon unacheivable*****");
        else
        printf(" The joint angles for the desired positon are %d \t %d \t %d \t %d \n", a, b, c, d);
        getch();
        }
    Last edited by treehugger; 08-28-2012 at 12:12 AM.

  2. #2
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    It is working fine.

    # cc cpb7.c -lm
    cpb7.c: In function âmainâ:
    cpb7.c:5: warning: return type of âmainâ is not âintâ
    # ./a.out
    Enter X value:
    0
    Enter Y value:
    -1
    Enter Z value:
    29
    The joint angles for the desired positon are 1073741824 -1074014454 1073741824 1072273817

  3. #3
    Algorithm Dissector iMalc's Avatar
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    Your bug is probably due to floating point representation. Floating point values are not exact, they are essentially a binary form of scientific notation.
    Reading: What Every Computer Scientist Should Know About Floating-Point Arithmetic

    Furthermore, you're only written PI to 2dp, so you're introducing quite a bit of error there yourself as well.

    Edit: Oh and as someone else shows, you're using the wrong format specific to printf for floats.
    My homepage
    Advice: Take only as directed - If symptoms persist, please see your debugger

    Linus Torvalds: "But it clearly is the only right way. The fact that everybody else does it some other way only means that they are wrong"

  4. #4
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    Quote Originally Posted by sana.iitkgp View Post
    It is working fine.

    # cc cpb7.c -lm
    cpb7.c: In function âmainâ:
    cpb7.c:5: warning: return type of âmainâ is not âintâ
    # ./a.out
    Enter X value:
    0
    Enter Y value:
    -1
    Enter Z value:
    29
    The joint angles for the desired positon are 1073741824 -1074014454 1073741824 1072273817
    You are getting such a large values for a, b, c, d?

  5. #5
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    Welcome to the forum, Treehugger!

    FORMAT your code, if you want much help on the forums.

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    I didn't change anything, I executed same program and the output is what i have given last time.

    One morething, your a,b,c,d are float values but you are printing them as int.
    If you change in your last printf(), then the output is


    Enter X value:
    0
    Enter Y value:
    -1
    Enter Z value:
    29
    The joint angles for the desired positon are -1.740000 0.800000 0.939999 0.036000
    Last edited by sana.iitkgp; 08-28-2012 at 12:06 AM.

  7. #7
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    @imalc - i have written pi only to 2 dp coz tis isnt a practical prog, its only for training/testing and furthermore, at-least it should give some output right. instead of "position unacheivable" every time?

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    sorry i tried but couldnt edit...

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    Quote Originally Posted by sana.iitkgp View Post
    I didn't change anything, I executed same program and the output is what i have given last time.

    One morething, your a,b,c,d are float values but you are printing them as int.
    If you change in your last printf(), then the output is


    Enter X value:
    0
    Enter Y value:
    -1
    Enter Z value:
    29
    The joint angles for the desired positon are -1.740000 0.800000 0.939999 0.036000
    thanks sana. i changed printf statement back to %f, and i should say that was a blunder. but still i couldnt get. I dont know how you got it.. and could suggest me a better way of doing this if you may???

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    I can explain what I did. But the math part, frankly i don't have any idea.

    First i printed values of x1,y1,z1 for every a,b,c,d, then i took one triple i.e.(x1,y1,z1) and given that input. It worked.

  11. #11
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    Quote Originally Posted by sana.iitkgp View Post
    I can explain what I did. But the math part, frankly i don't have any idea.

    First i printed values of x1,y1,z1 for every a,b,c,d, then i took one triple i.e.(x1,y1,z1) and given that input. It worked.
    couldnt understand.. a little more briefly plz

  12. #12
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    Are you still getting "Positon unacheivable" ?

    For every a,b,c,d in their range we have x1,y1,z1 values. I printed all them using below code. Then for original program i have given input as one such triple.
    Code:
    #include<stdio.h>
    #include<math.h>
    #include<conio.h>
        void main()
        {
            float a, b, c, d;
            int x = 0, y = 0, z = 0;
             int x1 = 0, y1 = 0, z1 = 0;
             int i = 0;
             printf("Enter X value: \n");
             scanf("%d", &x);
             printf("Enter Y value: \n");
             scanf("%d", &y);
             printf("Enter Z value: \n");
             scanf("%d", &z);
             for (a = -1.74 ; a <= 1.74 ; a = a + 0.02)
             {
                  for (b = 0.0; b <= 3.14; b = b + 0.02)
                  {
                       for (c = -1.74; c <= 1.74; c = c + 0.02)
                       {
                            for (d = -0.784; d <= 0.784; d = d + 0.02)
                            {
                                  x1 = (int)((11*cos(d+c+b+a)+11*cos(d+c+b-a)+12*cos(c+b+a)+12*cos(c+b-a)+9*cos(b+a)+9*cos(b-a))/2);
                                  y1 = (int)((11*sin(d+c+b+a)-11*sin(d+c+b-a)+12*sin(c+b+a)-12*sin(c+b-a)+9*sin(b+a)-9*sin(b-a))/2);
              z1 =  (int)(11*sin(d+c+b) + 12*sin(c+b) + 9*sin(b));
             printf("x1 = %d  y1 = %d  z1 = %d  \n",x1,y1,z1);
                                               
                                         }
                                  }
                           }
                     }
                }
           }
        status:
        if(i == 0)
        printf("*****Positon unacheivable*****");
        else
        printf(" The joint angles for the desired positon are %f \t %f \t %f \t %f \n", a, b, c, d);
        getch();
        }

  13. #13
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    actually tis would print all possible values but not the specific for user input of x, y, z.... i have edited the program above and now it works fine but takes lot of time to execute. try running if you may.
    Code:
    #include<stdio.h>
    #include<math.h>
    #include<conio.h>
    int main()
    {
        float a, b, c, d;
        int a1, b1, c1, d1;
        int x = 0, y = 0, z = 0;
        int x1 = 0, y1 = 0, z1 = 0;
        int i = 0, j = 0;
        printf("Enter X value: \n");
        scanf("%d", &x);
        printf("Enter Y value: \n");
        scanf("%d", &y);
        printf("Enter Z value: \n");
        scanf("%d", &z);
        for (a1 = -100 ; a1 <= 100 ; a1++)
        {
                printf("%d \t", j++);
                for (b1 = 0; b1 <= 180; b1++)
            {
                for (c1 = -100; c1 <= 100; c1++)
                {
                                  for (d1 = -45; d1 <= 45; d1++)
                          {
                           a = a1 * 0.0174532925;
                           b = b1 * 0.0174532925;
                           c = c1 * 0.0174532925;
                           d = d1 * 0.0174532925;
                                   x1 = (11*cos(d+c+b+a)+11*cos(d+c+b-a)+12*cos(c+b+a)+12*cos(c+b-a)+9*cos(b+a)+9*cos(b-a))/2;
                                   if(x1 == x)
                                   {
                                               y1 =(11*sin(d+c+b+a)-11*sin(d+c+b-a)+12*sin(c+b+a)-12*sin(c+b-a)+9*sin(b+a)-9*sin(b-a))/2;
                                               if(y1 == y)
                                               {
                                                     z1 = 11*sin(d+c+b) + 12*sin(c+b) + 9*sin(b);
                                                     if(z1 == z)
                                                     {
                                  i = 1;
                                  goto status;
                                                     }
                                                }
                                      }
                    }
                }
            }
        }
        status:
        if(i == 0)
        printf("*****Positon unacheivable*****");
        else
            printf(" The joint angles for the desired positon are \n %d \t %d \t %d \t %d \n", a1, b1, c1, d1);
            getch();

  14. #14
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    any way of optimizing the above code for faster answer?

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