wats wrong with this code? plz help!!!

Question

0.00/5 (No votes)

See more:

This is a program to find robotic arm inv kinematics.

My doubt is not in kinematics :-).

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.

C++

 #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();
}

Posted 27-Aug-12 18:20pm

Member 9386932

Updated 27-Aug-12 19:49pm

Joan M

v3

Add a Solution

Comments

mbue 29-Aug-12 18:38pm

This is a hint not a solution! Most common mistakes are the mixed usage of integer and floating point values. The most common errors base on rounding differences by a simple cast from double to int.
I see in your code alway on the left side: 11 or 12 or 9 these are int types. Most c compilers casts from right to left. Thats the function with cos and sin are always casted to int (left value). You should use 11.0*sin 12.0*sin and so on.
Regards.

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Sandeep Mewara · Answer 1 · 2012-08-27T19:17:00

This is the proper formatted code of your inner most for loop:

C#

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;
			}
		}
	}
}

If you see, you modify i, only after 3 conditions are met, i.e. x1=x, y1=y, z1=z.
As long as any one of them are not same, i is never modified and you land up in the if condition that satisfies i=0

If you debug, you should find that i might not be getting reassigned to 1 from 0.