Kinematic Modeling of Bird Locomotion from Experimental Data

We present the design of a bird-like kinematics model for a biped robot as an alternative to the human model. The starting point of the research consists of analyzing the walking motion of quail birds using biological data obtained by X-ray radiography. The 3-D-motion analysis allows identification of the number of degrees of freedom (DOF) and the rotation mechanism for each leg, especially the main rotation axis. Leg joints are located at the hip, knee, ankle, and foot. The ankle is off the ground. Using this analysis, we have designed a biped kinematics model with a minimum of actuated joints and with the original orientation of hip and ankle main rotary joints, which are not horizontally and vertically oriented as in classical biped robotics. Given a reference-foot trajectory, we carry out simulations to compare internal-joint trajectories with the ones obtained from biological measurements. We show that the proposed model can be used to reproduce the kinematics of bird locomotion with a minimum of four actuated joints per leg, i.e., two at the hip and one at the knee, and one at the ankle, which is less than the usual six joints per leg that drive anthropomorphic legs.