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Originally Posted by Andrew Schuetze
How might the DAQ and LabVIEW help us to tune a PID control loop on say a two segmented arm which has a mimic controller on the OI? My conception is that we won't have real time data to view as we test the prototypes rather we can download inputs from the RC mounted device and possibly match them up to values in the PID code...ideally I would want to watch sensor values and the code run in real time.
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The short answer is, you can view sensor readings in real time, as well as record them for later analysis. LabVIEW allows you to create virtual instruments, like oscilloscopes, voltmeters, and whatnot, with all sorts of cool features, allowing very powerful real-time and/or after-the-fact analysis. Using it for recording a kind-of 'as-built archive' or performance curves isn't the purpose (but not a bad idea, might make a cool poster!)
To your specific question, you would provide a known stimulus and measure the response of the arm. For example, you might use a collection of switches and resistors to 'command' the arm to a specific position, and using the DAQ and LabVIEW, look at the actual positioning response of the arm. We've all seen the classic PID response curves - underdamped (oscillates), overdamped (takes too long to reach the position) and critically damped (just right...) - well, you'll be able to see that in real time, along with how 'much', allowing very quick and easy adjustments to the PID variables.
For example.
It gets even better, because during development you can use sensors that aren't 'legal' (or, for weight, might not be used in competition) to measure and characterize every aspect of the machine's operation, allowing optimization.
Ideas:
- Measure wheel slip during acceleration, to allow for a software limit to acceleration regardless of operator inputs
- Measure accelerations related to stability, to understand what positions can tip the machine, then compensate somehow in software
- Gather data to better understand 'real' movements versus 'commanded' movements, for better dead reckoning
- Optimize motions in Autonomous by measuring what's happening.
It looks to be awfully exciting.
Don