Development of the skewed rotation plane (SRP) waist joint for humanoid robots

As humanoid robotics advances beyond bipedal walking, complex motions involving the whole body are necessary. Most recent humanoids represent the range of motion of the human spine with a single rotation joint. While this joint allows the body to swing during dynamic walking, any bending must be performed only with the legs. This paper develops a skewed rotation plane (SRP) waist joint to give a humanoid robot the same range of torso motion as a human. The SRP design reduces holding torque compared to a orthogonal-axis joint. An inverse kinematics solver using Jacobian Pseudo-inverse was developed to produce smooth torso orientation trajectories. Finally, a mechanical prototype developed and fitted to Drexel University's Jaemi Hubo to verify and validate the model.