Because humanoid robots can adapt to changes in its environment or itself, in order to reach its goals or fulfill its purpose, they are called autonomous systems.
Their technology (mechanical, spatial, time, power density, system and computational) are therefore usually much more complex than other kinds of robots.
In addition, humanoid robots are created to imitate some or all of the same physical and mental tasks that humans perform daily, which is a very difficult goal to achieve.
This complexity is more noticeable on power density and system complexity scales:
Because the power/weight ratio is not as good as in the human body it means, for example, that most humanoid robots are not even strong enough to jump yet.
And although very good algorithms exist for several areas of humanoid robot construction (engineering, cognitive science and linguistics), it remains extremely hard to merge all of them into one efficient system.
Humanoid robot tech consist of three basic components:
Sensors are important devices in robotic paradigms, that “connect” the humanoid robot to the outside – they allow it to take in and measures attributes of the external world.
Sensors are sometimes classified according to the type of measurement information that they give as output:
Proprioceptive sensors that sense the position, orientation and speed of the humanoid robot’s body and joints.
Exteroceptive sensors give the humanoid robot information about the surrounding environment allowing it to interact with the world, and include proximity sensors, tactels (for “touch”), vision and sound sensors.
Actuating Actuators (electric, pneumatic, hydraulic, piezoelectric or ultrasonic) are the motors responsible for robotic motion, and they mimic the human body.
Planning and Control One main difference between humanoid robots and other kinds of robots is that its movement has to be human-like. Humanoid robots normally use legged locomotion, especially biped gait and have to maintain dynamic balance during walking or running.
Another humanoid robot characteristic is that they have to interact with the “real” (human) world. Planning and control thus have to focus on factors like self-collision detection, path planning and obstacle avoidance.
There are also complex features in the human body that are desirable in humanoid robots, but (will) result in more/new planning and control problems. Examples of these desired features include variable flexibility (for safety), and redundancy of movement (more degrees of freedom).