For a system to be controled/regulated we have always an input and output. Due to the measurements of the outputs and the desired value the controller/regulator applies the input to the actuator.
In your question you do not mention which actuator would make the voltage increase or decrease.
The easiest controller my professor explained me in control theory was the bing-bang controller. If you know that increasing the input increases the output you might just increase the input till the comparision of desired value and measured value is zero or DB.
Now, a little bit more sophisticated would be a proportional controller, or if we would go further we would take a PI(D) controller.
There is actually a nice KB links which would explain
a little bit more about the PID controllers.
PID Control of Continuous Processes
Effects of the Proportional, Integral, and Derivative Components of the PID Algorithm on the System Response.
Refer as well to the link and especially to LabVIEW PID Control Toolset Manual.
Note: If you add a deadband criteria to your control loop the whole design might be more difficult an you have to encounter some non-linear control design. But this will end up in most cases, reducing the non-linearity to a linear control design and than you can apply all the linear control design rules.
In your case you might just have some logic which encouters the deadband to the desired value input.
Hope it give some of an idea where to start.
Roland
