what are all the ranks? and is there a way to get a better rank 
Ranks, which appear below your username, indicate the number of posts you have made or identify certain users, e.g. moderators and administrators. In general, you cannot directly change the wording of any board ranks as they are set by the board administrator. Please do not abuse the board by posting unnecessarily just to increase your rank. Most boards will not tolerate this and the moderator or administrator will simply lower your post count.
To my knowledge, their are three regular ranks robot lurker, roboteer, and robot guru. Robot Lurker(which is half of the lynx commmunity)means you have a post count of zero, roboteer(pretty much the other half of the lynx community)has 1-999 post count, and robot gurus(13 experts in robotics) have at least 1000 posts.