Design of a New Torso-Joint for the Humanoid Robot ARMAR

The development of a humanoid robot within the scope of the Collaborative Research Center 588 (SFB 588) has the objective of creating a machine that can cooperate with humans closely. For designers, computer scientists and me- chanical and electrical engineers this development area presents great challenges. In contrast to commercial industrial ro- bots - for which mechanical rigidity, precision, high velocities and accelerations are primary requirements - the key aspects here are prevention of hazards to users, a motion space that corresponds to that of human beings, and a lightweight design. In order to meet these requirements, the robot must have humanlike appearance, motion space, and dexterity. Additionally, its kinematics should be familiar to the user, and its motions predictable, so as to encourage inexperienced persons to inter- act with the machine. The human spine offers great flexibility and is loaded with the weight of at least the whole upper body. On this account the emulation of the human upper body movement describes one of the most advanced issues in hu- manoid robot design. For the next generation of the humanoid robot ARMAR, a new concept to achieve a better flexibility in the robot's upper body movement has been done. This new torso-joint offers high stiffness, better accuracy and simulta- neously reduces weight and construction volume. Spring elements are used to save energy and to support the engines. In this paper the new mechanical design and first calculated results, considering energy saving potential and stiffness, are de- scribed in detail.