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When J 1 and J 2 are not 0), changes in J 2 or J 3 do not affect p by performing the corresponding rotation A or K on it. However, these rotations are very useful because the forward kinematics function can be defined as K F (J ) = R(A(K ( p 0 , J 3 ), J 2 ), J 1 ). 1) This formulation is based on the idea that for any set of angles J , the foot can be moved from p 0 to its final position by rotating the knee, abductor, and rotator by J 3 , J 2 , and J 1 , respectively, in that order. This formulation works because when the rotations are done in that order they are always the rotations K , A, and R.

When each robot shares its Global Map (see Chapter 11) with its teammates, these data get communicated. When the robot receives data from its teammates, a similar process is incorporated. , one that was updated in the current cycle) that is communicated by a teammate and tries to merge it with one of its own estimates. If it fails to do so and it has fewer than four opponent estimates, it accepts the communicated estimate as such and adds it to its own list of opponent estimates. But if it already has four opponent estimates, it replaces its oldest estimate (the one with the largest variance which is larger than robotics Mobk082 July 9, 2007 5:34 VISION 25 the variance of the communicated estimate too) with the communicated estimate.

In many of the fastest and most stable walks, the front legs touch the ground with their elbows when they step. Apparently, this is far more effective than just having the feet touch the ground. We enable the elbows to touch the ground by setting the height of the front shoulders to be lower than that of the back shoulders. However, this ability requires one more computation to be performed on the foot coordinates before the inverse kinematics equations are applied. That is, when the AIBO’s body is tilted forward, we still want the feet to move in half-ellipses that run parallel to the ground.