The invention discloses a forward and
inverse kinematics calculation method for a 2-SPS-1U parallel mechanism of a
humanoid robot, and relates to the technical field of humanoid robots.
Inverse kinematics calculation includes the steps that the
pitch angle and the roll angle of a
wrist, the inherent position of a spherical
hinge point at the
tail end of an SPS branched chain and the fixed translation vector of a
wrist rotating shaft base coordinate
system relative to a driving motor coordinate
system are obtained; and constructing an attitude
rotation matrix to convert the
tail end spherical
hinge point to a real-time coordinate, converting the real-time coordinate to a driving motor coordinate
system by combining a fixed translation vector, and calculating a
coordinate vector modulus length to obtain a branched chain telescopic length. The
forward kinematics solution comprises the steps of obtaining the actually measured length and constant parameters of the branched chain, and constructing a nonlinear equation set by taking a roll angle and a
pitch angle as unknown quantities; and solving by combining a two-dimensional residual vector with a Newton iteration method, estimating a Jacobian matrix by using a
finite difference method in iteration, and outputting an attitude angle when the residual is smaller than a threshold value. The method is accurate and stable in calculation and adapts to the
robot wrist joint control requirement.