Inertial rotation center position estimation for a perching treaded vehicle

A method for estimating the rotation center position (RCP) of a rigid body in the x-y plane using two offset accelerometers is presented. RCP estimation via inertial measurement is motivated by the related problems of detecting foot slippage of legged robots and detecting stair edges for treaded robots, for applications in which alternative methods such as discontinuity recognition, visual tracking, and/or tactile feedback are impractical. The RCP may be directly solved for as a function of the two offset tangential acceleration measurements, when the RCP is colinear with the two accelerometers, and when the common-mode tangential accelerations, due to linear acceleration and/or gravity, can be independently measured or estimated. Angular velocity estimates may be enhanced by combining calculated angular acceleration with gyroscope measurements, even when both the RCP and common-mode tangential accelerations cannot be independently measured. An input variance modulated variable cutoff low-pass filter is also proposed for RCP estimation in the absence of independent measurements, which is validated on a balance-beam inverted-pendulum apparatus.