Displacements of respective joints corresponding to respective joint
elements (J9 and the like) of a rigid link model (S1) representing a
two-legged walking mobile body (1) are sequentially grasped. Also at the
same time, values, in a body coordinate system (BC), of an acceleration
vector of the origin of the body coordinate system (BC) fixed to a waist
(6) as a rigid element, a floor reaction force vector acting on each leg
(2), and a position vector of the point of application of the floor
reaction force vector are sequentially grasped. With the use of the
grasped values, joint moments respectively generated in an ankle joint
(13), a knee joint (14), and a hip joint (9) of each leg (2) are
sequentially estimated based on an inverse dynamics model using the body
coordinate system. The estimation accuracy of the joint moments of the
leg can be enhanced by reducing arithmetic processing using tilt
information of the two-legged walking mobile body relative to the gravity
direction as much as possible.