Before revision:  Quaternion logarithmic map is integrated to generate complete rotational stiffness . Besides, the Dynamic Movement Primitives (DMPs) model is further developed to encode and schedule both the movement trajectory and stiffness profiles in task space simultaneously. Finally, the effectiveness of our approach is validated on a real-world 7 DoF robot with the variable impedance controller .
After revision:  Quaternion logarithmic map is integrated to generate complete rotational stiffness . Besides, with our stiffness estimation method, we generate not only translational stiffness profiles, but also rotational stiffness profiles that are ignored or incomplete in most learning VIC papers. Real-world experiments on a 7 DoF robot with the variable impedance controller .