Hello everyone, how are you?

Well, I built a tutorial teaching how to make a robot arm from scratch, but a problem arose: my servants are very unstable and I can't make their movement less abrupt.

How can I do to correct this problem?

The tutorial Braço Robotico Arduino: 

https://flaviobabos.com.br/braco-robotico-arduino/

on how to make a robotic arm is perfect, contains many images step by step with a didactic that I would like everyone to understand.

Thank you guys!