Linkages criss-cross at position rep

[luiww]

I am trying to carry out an animation of the walking gait of a humanoid.  When I input the angle of 30 deg to the link, the link criss-cross.  At 10 deg, the link does not criss cross.  How could one avoid such problem. My intend is to show the walking gait using Inventor Studio after placing the angles in the position reps. Attached is the assembly.

The files are in Inventor 2011.

[davecarrington5097]

Just a quick hunch on this one - I haven't looked at the files yet.  Are you using the explicit reference vector option to define you angle constraints?  If not, you might give that a shot.

- Carrington

[luiww]

No and how could I do that.  Any examples for me to follow. 

[davecarrington5097]

When adding the angle constraint, you'll select the two faces that are angular to each other and also an axis that runs along the 'hinge axis.'  Inventor help describes to as follows: An Angle constraint positions edges or planar faces on two components at a specified angle to define a pivot point. Removes one degree of freedom in rotation or two degrees of angular rotation between planar surfaces.
	Directed Angle solution always applies the right-hand rule. Does not support user specified limits and resting position.
	Undirected Angle allows either orientation, thus resolving situations where component orientation flips during a constraint drive or drag. Supports user specified limits and resting position.
		Explicit Reference Vector Explicitly defines direction of Z axis vector (Cross Product) by adding a third pick to the selection process. Reduces tendency of angle constraint to switch to an alternate solution during a constraint drive or drag. This solution is the default. Supports user specified limits and resting position.

[luiww · Accepted solution]

Thanks for the guidance and I now know how to define the angle more explicitly.  I have been using only the direct angle all the time not know there are other options available.  It did not solve my problem using the angle proposed.  I simply added a parallel constrain to the 2 links and it apparently works.  Thanks.