Vishniu Gopalakrishnan wrote:
actually the constraint equations are correct. I actually made a mistake in the diagram I sent you and the angle that i have shown as theta4 is actually theta4+atan(..).i have enclosed the new figure.The only constraints for a,b and c are that they should be greater than 0.
No, and thats the problem. There are more constraints you have to find out. As you have seen you don't get a solution for the angles with certains combinations of the arm lengths. This is due to the fact that your four-bar linkage will lock if e.g. a is too small. c would then not be able to move up to full 90° or down to 0°.
Another method would be that the function TT checks if you get a solution for theta4=0 and 90° and if not, it would yield a rather big result so that it will fall out of minimization. Quick and dirty but it may work.
Better of course you check your geometry and find some constraints for a, b and c which would guarantee that c can move in the range of 0 to 90 °.
