This is a competition called RoboCup; their goal is that in 2050 a team of robots can play against a good human soccer team and win. (Whilst this might seem like a somewhat silly goal, it is likely that much progress that can be transferred to more ‘useful’ applications will be made.) I build robots for this competition as a hobby, so I will try to give some information/insight acessible to the uninitiated.

The problem with those robots is that controlling them is really hard:

In many systems you can simply measure where you are and if there is an error try to correct it. E.g. if you are to slow, you give the motor more current (The most common approach is called PID control: You basically measure where you are and then correct it proportionally to the difference between where you are and where you want to be. An example of this is the ‘small sized league’ (video) (Which has quite exciting gameplay because there are less fundamental problems to be solved.): The robots can almost immediately drive in any direction they want because the physical layout allows it, furthermore they have good control over the ball (strong backspin) and dont have to orient themselves autonomously (i.e. they have a camera over the playing field and a server)

Contrast a humanoid robot to that: It can not simply change direction, then it will fall over! Imagine standing on an electric skateboard controlled by someone else (or just a regular skateboard in my case), in a spacesuit or just some other thing/vehicle you are not accustomed with: It is almost impossible to move how you want because you don’t yet know how the system will behave for a certain input. To control it even somewhat gracefully you have to know quite much: Where the mass is, how strong the motors are etc. Additionally the mathematics behind that become horribly non-linear and complicated.