HRP-4C, Dancing Robot Girl

Like other mechanical robots, humanoid refer to the following basic components too: Sensing, Actuating and Planning and Control. Since they try to simulate the human structure and behavior and they are autonomous systems, most the times humanoid robots are more complex than other kinds robots.
This complexity affects all robotic scales (mechanical, spatial, time, power density, system and computational complexity), but it is more noticeable on power density and system complexity scales. In the first place, most current humanoids aren’t strong enough even to jump and this happens because the power/weight ratio is not as good as in the human body. The dynamically balancing Dexter can jump, but poorly so far. On the other hand, there are very good algorithms for the several areas humanoid construction, but it is very difficult to merge all them into one efficient system (the system complexity is very high). Nowadays, these are the main difficulties that humanoid robots development has to deal with.
Humanoid robots are created to imitate some the same physical and mental tasks that humans undergo daily. Scientists and specialists from many different fields including engineering, cognitive science, and linguistics combine their efforts to create a robot as human-like as possible. Their creators' goal for the robot is that one day it will be able to both understand human intelligence, reason and act like humans. If humanoids are able to do so, they could eventually work in cohesion with humans to create a more productive and higher quality future. Another important benefit developing androids is to understand the human body's biological and mental processes, from the seemingly simple act walking to the concepts consciousness and spirituality. Right now they are used for welding. In the future they can greatly assist humans by welding and mining for coal.
There are currently two ways to model a humanoid robot. The first one models the robot like a set rigid links, which are connected with joints. This kind structure is similar to the one that can be found in industrial robots. Although this approach is used for most the humanoid robots, a new one is emerging in some research works that use the knowledge acquired on biomechanics. In this one, the humanoid robot's bottom line is a resemblance the human skeleton.