Inertial measurement system for biped robots that takes scheduled centrifugal effect into consideration

This paper presents an inertial measurement system for bipedal humanoid robots that takes centrifugal force into consideration during walking. Attitude relative to the gravity direction should be measured at 0.01[rad] (approx. 0.5[deg]) accuracy in the dynamic environment in order to realize walking control on uneven terrain whose profile is unknown in advance. Combination of fiber optic gyroscopes and servo accelerometers are adopted in order to achieve the required accuracy. As the centrifugal force during turning walk causes unignorable effect to the gravity direction calculated by the outputs of accelerometers, we introduced a cancellation method of centrifugal effect. The effect is estimated by translational and rotational velocity of the sensor unit which is calculated from the planned walking trajectory. Measurement accuracy smaller than 0.01[rad.] is accomplished at the condition that the error would become more than 0.03[rad] when the effect is not considered.