Bipedal Robot MABEL Traverses Uneven Terrain Using Touch Instead of Sight

This video presents a feedback controller that allows MABEL, a kneed planar bipedal robot with 1 m-long legs, to accommodate terrain that presents large unexpected increases and decreases in height. The robot is provided information on neither where the change in terrain height occurs, nor by how much. A finite-state machine was designed to manage the transitions among controllers for flat-ground walking, stepping-up and down, and a trip reflex. When the robot completes a step, the depth of a step-down or height of a step-up can be immediately estimated at impact from the lengths of the legs and the angles of the robot's joints. The change in height can be used to invoke a proper control response. On the other hand, if the swing leg impacts an obstacle during a step, or has a premature impact with the ground, a trip reflex is triggered on the basis of specially designed contact switches on the robot's shins, contact switches on the end of each leg, and the current configuration of the robot. The design of each control mode and the transition conditions among them are illustrated.

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