This can be a basic question but according to my knowledge I don’t know answer.
We can use control system theories to control the position of motor. Considering two motor joint leg it can model and can control position with disturbances. (Consider Linkage to Hip and Hip motors)
But how to control external disturbances to robot by control system.
See this Video https://youtu.be/xNeZWP5Mx9s at 0.45 minute.
This man give external disturbances by kick to MIT mini cheetah robot. Then that robot move to side by activating linkage to hip and hip motor. How it is possible to do by control system?
According to my knowledge control system do more margin to robust and use PID control. (Also can be use feed forward etc.) it use to control position by input voltage signal to Motor to stable the system. Not work like above video (Side move) to stable.