Describe a process problem you have experienced and how you solved it?

The Problem Solving process consists of a sequence: 1-Problem Definition.
2-Problem Analysis.
3-Generating possible Solutions.
4-Analyzing the Solutions.
5-Selecting the best Solution(s).
6-Planning the next course of action

it was a twin pump feeds chiller , this pump works as master and slave , the slave one runs according to the master in two modes .

1- main and standby
2- parallel in the first mode the slave pump run only when the master is failure .and it run in full speed at 50 HZ and con't changed.
in the second mode the slave run in variable speed according to the speed of the master and the slave pump con't run in variable speed except in this mode only.
the problem is that i need to make each pump runs individually with variable speed * the steps i take to solve this problem - i put the slave pump on parallel mode because its the mode that the slave can only run in variable speed - check the signal comes from the master to control the speed i found it's 0 to 10 VDC - canceled all connections between the two pumps - install external potentiometer in slave pump and applied 10 VDc on its input - then the potentiometer output will gives me the volt i need from 0 to 10 VDC - replaced the signal comes from master by the output of the potentiometer so i can run the slave pump individual and control its speed without any need of master one