If you where to design a humanoid robot to beat Usain Bolt at running, how would you design it would you use air muscle, hydraulic, servo motor, or stepper motor and why ? How well you power it ? What leg design would you use ?
Air muscle / Pneumatic: needs an air compressor which itself needs either a battery pack or gasoline engine - because of the weight, it’s not practical. The forces involved are not significant.
Hydraulic: Same situation as pneumatics, but can generate tremendous forces - you need an electric or gasoline compressor.
Servo: Almost all humanoid robots are servo based (or smart servo)
Stepper: Usually not the first choice because of the more complex control, higher price (because you need to add gears) and they don’t have a zero position.