retrolefty:
I would think the single most efficient control algorithm would be to use an internal humidity sensor to tell the controller that the cloths are dry enough now and to cut the heat source (gas or electric) and start the tumble cooling cycle. I believe that there are dryers that have that control option available all ready?
Every unit I saw did not measure humidity directly. Either capacitive sensors, temperature, etc. I presume fouling has to do with it. The nice aspect of the "bar" sensors typically found in the back wall of dryers is that they cannot foul easily. How accurate they are is another question. However, you can supplement that info with exit temperature info to hopefully not over- or under-dry too much.