Basically I got system with a sensor and an output. I want to apply a digital implemented feedback controller. The problem in this setup is the sensor. The specifications of the module says that the sampletime of the sensor does change in wide range, depending on the usecase; from 1.3 second to 10 second. But it stays constant until the system is disabled.
My first approach was tuning a digital PID-Controller for the longest sampletime. This works fine. Even if I change the sampletime to the shortest the system stays stable, which was expected because I'm still in ROC. The problem now is that the system's response is pretty slow.
If I design the controller for my fastest samplingrate the results are satisfying but become instable for the slowest samplerate, which can be explained again by the ROC
I could use some kind of adaptive predefined gains which I change depending on the samplerate but I was wondering if there are control strategies which are able to handle the sampletime changes?
To give a better overview I will add some details:
I'm talking about a heating system which heats with radiation. As a sensor I use a pyrometer module with a samplingrate of up 1kHz. The problem is, that the pyrometer is not able to produce reasonable readings whenever the radiator is turned on. (Yes there are other alternatives to the pyrometer, but they start at $50k and are too expensive). The radiator has to be pulsed to operate it. So to maintain a decent heat up time and steady-state temperature the "duty-cycle" has to be at a decent rate(target is 95%). The minimum "off-time" of the radiator is 0.2 seconds before the measured values are reasonable. So at the end my sensor got an effective sampletime of 1-10seconds (by varying the duty cycle).
The hardware is hard too change, radiator and sensor have been evaluted for months right now. Therefore I try to improve the results by "just" changing the control algorithm.