Development of humanoid robot platform khr-2 (kaist humanoid robot 2)

The mechanical and electrical system designs and system integration including controllers and sensory devices of the humanoid KHR-2 are presented. The design concept and the objective are also discussed. Since 2003, we have been developing KHR-2, which has 41 DOF (degrees of freedom). Each arm of KHR-2 has 11 DOF in total: 5 DOF/hand (i.e. fingers), 2 DOF/wrist, and 4 DOF/arm. Each leg constitutes 6 DOF. The head constitutes 6 DOF (2 DOF for eyes and 2 DOF at the neck), and the trunk has 1 DOF. KHR-2 has been mechanically designed to have a human friendly appearance and also wide ranges of angular motion. Its joint actuators have been designed in order to reduce motion uncertainties such as backlash. All axes of KHR-2 are under distributed control, which reduces the computational burden on the main controller and also to facilitate device expansions. We have developed a microprocessor-based sub-controller for servo motor operations, onto which sensory feedback is interfaced. The main controller, which is mounted on the back of the robot communicates with sub-controllers in real-time through CAN (Controller Area Network). Windows XP is used as the OS (Operating System), which enables rapid program development. RTX (Real Time eXtension) HAL extension software is used to realize the real-time control in the Windows XP environment. KHR-2 has several sensor types such as 3-axis F/T (Force/Torque) sensors at the foot and wrist, an inertia sensor system (accelerometer and rate gyro), and a CCD camera. The F/T sensor at the foot is crucially important for stable walking. The inertia sensor system is essential for determining the inclination of the robot with respect to the ground.