Simple Biped

KISS - Keep It Simple Stupid. This is a good principle to follow when designing robots. Usually there is a well defined goal for a robotics project, so why make things more complicated? Alright, maybe we all want to make our projects really cool, and add extra bells and whistles in order to make it cooler. This new biped is not meant to do that though - it is meant to be a very robust biped that can carry a high payload. Once that is achieved it may become the platform for a competitive mech for http://www.mech-warfare.com/ 2012.

The robot features legs with 2 DOF each, with a 4-bar linkage on each DOF to maintain a level foot in any position. This eliminates the need for additional servo's. 2DOF is all that is required to make a leg move into any position in the plane of the leg. Turning is achieved by moving the legs in opposite directions from each other - similar to how a tank steers. This means that the feet must be able to slide on the surface it is walking on. The robot also must have a way to maintain balance when a leg is lifted. Traditionally bipeds will tilt their body weight using hip and ankle servo. In order to maintain balance, one of two methods will be used - either overlapping feet or a "tail" that moves to change the center of mass to be over the supporting foot as it walks.

These are the first generation of legs, designed to be made out of sheet metal.

In order to get things moving quickly though, I decided to print out the first prototype legs using my Makerbot 3d printer. This makes a quick way to test out the design and see how it acts, and to bring more insight into the walking motion.

A basic walking gait was created using Pypose ( http://code.google.com/p/arbotix/wiki/PyPose ). As you can see from the video, the legs drag when they return to the front, causing the robot to rotate back and forth as it walks forward. This is because biped does not have a way to balance itself yet, and when the leg lifts for the return step of the gait, the robot just tips. Once the overlapping feet, or balancing tail is implemented, it should walk a lot straighter and faster.