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Research on Weight Lightening and Optimal Design

■ Overview

The good thing of using an electric motor is that it is light, energy efficient and possible for high-speed; on the other hand, an electric motor has relatively lack of power compared to the other driving systems such as hydraulic system. Therefore decelerator with the high ratio of deceleration is generally used in the case of when high power is necessary. However at the same time, it could be limited by the fast movement caused by the high ratio of deceleration.  

To increase power and speed, the system's weight needs to be as light as possible. The best optimized design is necessary in order to maintain the maximum stiffness while reducing the system's weight. The Rainbow Corporation achieved the optimized design techniques through testing various system designs; and the techniques have been applied on HUBO 2 so that HUBO 2 is able to carry the sufficient power and speed. 

■ Case 1 : Push-Up motion

Except for the kind of humanoid robots developed by the concept of dynamic system except an electric motor, such as hydraulic system, all the full-sized humanoid robots activated by an electric motor couldn't keep their balance due to the control limit of the outputs. However HUBO 2, which has been built based on the optimized design, can perform those motions that the existing platforms couldn't perform. 

■ Case 2 : Fast ARM motion

HUBO 2 designed by the best optimization technique can perform the fast motion as well as those motions which require the high power like push-up. As the arms are maximally open (when the inertia is a maximum), the angular speed of the arm is 850 degrees/sec and its angular acceleration is more than 4,700 degrees/sec.  
Also the motion of throwing a ball is possible with the HUBO's hands. 

■ Case 3 : Long-term walking

Through improving the existing humanoid robot platform with the optimized design and control algorithm, long-term walking motion has become practicable. HUBO 2 can walk for two hours with the lithium polymer battery of 48V of a rated voltage and 7.5A of a rated current.