Here's an example of mapping a joystick to the range of a potentiometer.
This would force an arm to a particular setting of the potentiometer.
In this case we have a pot with a minimum value of 1.17v when the arm joint is in the lowest position.
The pot has a maximum value of 3.9v when the arm is in the highest position. (You never want to run your pot right up to it's physical limits, otherwise it can get broken very easily)
The joystick full range gets mapped to the pot's full range in the left box. In other words the joystick value gets converted into pot terms.
The right box applies the PID based on the joystick position (now in desired pot terms), and compares it to the current actual pot value, to produce a motor output that will force the arm in the direction it must go in order to make the actual pot value line up with the desired pot value.
