Designing robot hands (or end effectors) can be a perilous task ... Sometimes the best solution is a clever mechanical design, one which ensures a gripper will conform to the object it is gripping.
Further details can be found in the following paper: “Hybrid Force-Impedance Control for Fast End-Effector Motions”, Maged Iskandar, Christian Ott, Alin Albu-Schäffer, Bruno Siciliano, and Alexander ...