Synchronisation of two axes

[macbahi]

Hi!
I am new in this forum and sorry for my english.

Please I have two linear actuators with potentiometers.
I use them to deplace two arms as robot.
First I fix the first arm (actuateur A) to one position vertically. Secondly I will move actuator_B but when I will move it, the actuator_A must move in order to stay in same position vertically as in the begining. So I need help to realize this project.

Please Have you some ideas or if you have any reference as this work.

thanks in advance for your help and collaboration

mac