Editing Humanoid robot (section)

==Actuators==
[[Actuator]]s are the motors responsible for motion in the robot.<ref name=":20">{{cite journal |doi=10.1016/j.sna.2016.06.010 |title=A survey on actuators-driven surgical robots |date=2016 |last1=Le |first1=Huu Minh |last2=Do |first2=Thanh Nho |last3=Phee |first3=Soo Jay |journal=Sensors and Actuators A: Physical |volume=247 |pages=323–354 |bibcode=2016SeAcA.247..323L |hdl=10356/138026 |hdl-access=free }}</ref>

Humanoid robots are constructed in such a way that they mimic the human body. They use actuators that perform like [[muscle]]s and [[joint]]s, though with a different structure.<ref name=":20" /> The actuators of humanoid robots can be either electric, [[pneumatic]], or [[hydraulic]].<ref name=":21">{{cite journal |last1=Hashimoto |first1=Kenji |title=Mechanics of humanoid robot |journal=Advanced Robotics |date=16 November 2020 |volume=34 |issue=21–22 |pages=1390–1397 |doi=10.1080/01691864.2020.1813624 |doi-access=free }}</ref><ref name=":22">{{cite book |doi=10.1007/978-3-319-93870-7_13 |chapter=An Overview of Humanoid Robots Technologies |title=Biomechanics of Anthropomorphic Systems |series=Springer Tracts in Advanced Robotics |date=2019 |last1=Stasse |first1=O. |last2=Flayols |first2=T. |volume=124 |pages=281–310 |isbn=978-3-319-93869-1 |chapter-url=https://hal.laas.fr/hal-01759061 }}</ref> It is ideal for these actuators to have high power, low mass, and small dimensions.<ref name=":22" />

=== Electric ===
Electric actuators are the most popular types of actuators in humanoid robots.<ref name=":21" /> These actuators are smaller in size, and a single electric actuator may not produce enough power for a human-sized joint.<ref name=":21" /> Therefore, it is common to use multiple electric actuators for a single joint in a humanoid robot.<ref name=":21" /> An example of a humanoid robot using electric actuators is [[HRP-2]].<ref name=":22" />

=== Hydraulic ===
Hydraulic actuators produce higher power than electric actuators and pneumatic actuators, and they have the ability to control the torque they produce better than other types of actuators.<ref name=":22" /> However, they can become very bulky in size.<ref name=":21" /><ref name=":22" /> One solution to counter the size issue is [[Electro-hydraulic actuator|electro-hydrostatic actuators]] (EHA).<ref name=":22" /> The most popular example of a humanoid robot using hydraulic actuators is the [[Atlas (robot)|ATLAS]] robot made by [[Boston Dynamics]].<ref name=":22" />

=== Pneumatic ===
Pneumatic actuators operate on the basis of [[gas]] [[compressibility]].<ref name=":21" /><ref name=":22" /> As they are inflated, they expand along the axis, and as they deflate, they contract. If one end is fixed, the other will move in a linear [[trajectory]]. A popular example of a pneumatic actuator is the [[Pneumatic artificial muscles|Mac Kibben muscle]].<ref name=":22" />