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Walking Cycle


The walking cycle for FOBO is composed of 100 frames that are derived from 10 key positions.  Each of the key frames are statically balanced, meaning that the robot won't fall over if it stops.  

Spline based interpolation is used to compute the joint positions for the frames in between the key positions.   These extra frames are important to ensure smooth motion.




The walking cycle can be broken into two main sections, one for the right leg and one for the left leg.  These two sections are identical except that they are mirrored about the central axis of the robot.   Each leg section can further be divided into subsections, one for the leg lifting up, another for the leg moving down, and a third where the weight is transferred to the opposite leg.  The most difficult part of the walking cycle is the transfer of weight from one leg to another.  For a static walking cycle the center of mass must be completely over the load bearing foot before the other foot may be moved. To accomplish the weight transfer FOBO uses the hip and ankle servos to move its body from side to side which changes its center of mass. 

  
FOBO has a vertical clearance apex of 0.68" and a step length of 0.85".  Its stride length, the distance between successive points of initial contact of the same foot, is 1.7". A full walking cycle is completed in 3.2 seconds which gives a forward walking speed of 0.53 inches/second.  This speed could be increased but will make the robot less stable.  Currently the playback delay between each frame of the walking cycle is equal, however this is almost certainly sub-optimal.  There is some optimal sequence of frame delays that minimizes the inter-frame momentum that would allow for a much faster walking speed.