Motion Planning for Closed-Chain Mechanisms

Problem statement:

Given start (purple) and goal (red) configurations of a closed polygonal chain, determine an optimal trajectory connecting the start to the goal.

We have developed a low-order polynomial-time complete algorithm for solving this problem; if a solution exists, it will be found; if not, nonexistence will be reported. We ignore link-link collisions and assume no joint limits. You can see some of our initial solutions in action by clicking on the images below.
Here are some related papers: theory, algorithm description, conference version of algorithm description.