example of a pneumatic actuator is the Mac Kibben muscle. Planning and control Planning in robots is the process of planning out motions and trajectories for the robot to carry out. Control is the actual execution of these planned motions and trajectories. In humanoid robots, the planning must carry out biped motions, meaning that robots should plan motions similar to a human. Since one of the main uses of humanoid robots is to interact with humans, it is important for the planning and control mechanisms of humanoid robots to work in a variety of terrain and environments. The question of walking biped robots stabilization on the surface is of great importance. Maintenance of the robot's gravity center over the center of bearing area for providing a stable position can be chosen as a goal of control. To maintain dynamic balance during the walk, a robot needs information about contact force and its current and desired motion. The solution to this problem relies on a major concept, the Zero Moment Point (ZMP). Another characteristic of humanoid robots is that they move, gather information (using sensors) on the "real world", and interact with it. They do not stay still like factory manipulators and other robots that work in highly structured environments. To allow humanoids to move in complex environments, planning and control must focus on self-collision detection, path planning and obstacle avoidance. Humanoid robots do not yet have some features of the human body. They include structures with variable flexibility, which provide safety (to the robot itself and to the people), and redundancy of movements, i.e. more degrees of freedom and therefore wide task availability. Although these characteristics are desirable to humanoid robots, they will bring more complexity and new problems to planning and control. The field of whole-body control deals with these issues and addresses the proper coordination of numerous degrees of freedom, e.g. to realize several control tasks simultaneously while following a given order of priority. Timeline of developments In science fiction A common theme for the depiction of humanoid robots in science fiction pertains to how they can help humans in society or serve as threats to humanity. This theme essentially questions whether artificial intelligence is a force of good or bad for mankind. Humanoid robots that are depicted as good for society and benefit humans are Commander Data in Star Trek and C-3PO in Star Wars. Opposite portrayals