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Autopilot PID controller tuning resources: Difference between revisions
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Autopilot PID controller tuning resources (view source)
Revision as of 20:52, 30 November 2010
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Knowing the algorithm is mandatory, certain values are forbidden, for example they can lead to a division by zero. Then you will have to understand where the parameters apply to act on the chosen correction module. See the schema which is a good reminder while testing. | Knowing the algorithm is mandatory, certain values are forbidden, for example they can lead to a division by zero. Then you will have to understand where the parameters apply to act on the chosen correction module. See the schema which is a good reminder while testing. | ||
[[ | [[File:pid_controler.png|thumb|PID parameter's application]] | ||
[[ | [[File:pid_cotroler_data_graph.png|thumb|Datas of an Auto-trim PID Controller displayed as graphs]] | ||
You can find good explanations on how to practically tune the controller. [http://en.wikipedia.org/wiki/PID_controller Wikipedia's article on the PID Controller] | You can find good explanations on how to practically tune the controller. [http://en.wikipedia.org/wiki/PID_controller Wikipedia's article on the PID Controller] | ||
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</pre> | </pre> | ||
[[ | [[File:Live-graph-datafile-settings.png|thumb|Setting the Logfile input]] | ||
[[ | [[File:Livegraph-graph-settings.png|thumb|Setting the visuals]] | ||
[[ | [[File:Livegraph-dataseries-settings.png|thumb|Finetuning the visuals]] | ||
[[ | [[File:Livegraph-plot.png|thumb|Livegraph plotted data]] | ||
The first 4 lines prepare a kind of "header" in the Logfile so that the Grapher can use it. In the while-part I added the pipe sign as separator so that Live-Graph can use the output. Copy and paste these lines into your favorite ASCII text editor and save it to your FG directory (e.g. save as "fgfsparser.pl"). Next you need to install a Perl Interpreter (e.g. [http://www.activestate.com/activeperl Activestate's Active Perl]). Now start Flightgear the following way: | The first 4 lines prepare a kind of "header" in the Logfile so that the Grapher can use it. In the while-part I added the pipe sign as separator so that Live-Graph can use the output. Copy and paste these lines into your favorite ASCII text editor and save it to your FG directory (e.g. save as "fgfsparser.pl"). Next you need to install a Perl Interpreter (e.g. [http://www.activestate.com/activeperl Activestate's Active Perl]). Now start Flightgear the following way: | ||
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After installing it start Live-Graph and set the Data file to your output logfile (e.g. "my_file"). Be aware that you don't have an output file before you did not start the process of debug output at least one time. In this case start Flight Gear first and activate the AP function on the autopilot where you activated the debug=true output. Back to Live-Graph: The update frequency works fine with updates at 1 Hz or 2 Hz (every 1 or 2 seconds). Activate "Show tail data" so that your graph will not be overcrowding during the time and keep caching data active or you will experience loss of data which will make your tests useless. | After installing it start Live-Graph and set the Data file to your output logfile (e.g. "my_file"). Be aware that you don't have an output file before you did not start the process of debug output at least one time. In this case start Flight Gear first and activate the AP function on the autopilot where you activated the debug=true output. Back to Live-Graph: The update frequency works fine with updates at 1 Hz or 2 Hz (every 1 or 2 seconds). Activate "Show tail data" so that your graph will not be overcrowding during the time and keep caching data active or you will experience loss of data which will make your tests useless. | ||
Next you need to define the visual output: set the viewport on the Y-axis from min. -1.5 to max. +1.5. Leaving the scaling to "auto" will create a graph which will not be very easy to read. X-axis set to auto on both sides. | Next you need to define the visual output: set the viewport on the Y-axis from min. -1.5 to max. +1.5. Leaving the scaling to "auto" will create a graph which will not be very easy to read. X-axis set to auto on both sides. It's quite handy to set the horizontal grid (I prefer a grid size of 0.2 to 0.5). And last but not least on X-Axis set "Dataset numbers" as type for the input. | ||
In the Data series window you can switch the single values on and off and define the way how the program should plot the data. Here in the image I acquire the data of a simple wing leveler and therefor I normalize all data to values between 0 and 1. Be aware that my settings are not mandatory. Be creative and play around with different settings until you feel satisfied with the plotted data. | In the Data series window you can switch the single values on and off and define the way how the program should plot the data. Here in the image I acquire the data of a simple wing leveler and therefor I normalize all data to values between 0 and 1. Be aware that my settings are not mandatory. Be creative and play around with different settings until you feel satisfied with the plotted data. | ||
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To tune a controller you would typically display the setpoint property and the controlled property in the same graph. Another property that is interesting too look at is the actuating property, which can be for example the aileron control or the elevator control. | To tune a controller you would typically display the setpoint property and the controlled property in the same graph. Another property that is interesting too look at is the actuating property, which can be for example the aileron control or the elevator control. | ||
[[Category:Resource]] | [[Category:Resource]] | ||