{"id":3505,"date":"2025-04-18T10:36:50","date_gmt":"2025-04-18T10:36:50","guid":{"rendered":"https:\/\/webprojects.cloud\/wordpress\/splatco\/?post_type=spl_knowledgebase&#038;p=3505"},"modified":"2025-06-10T11:48:18","modified_gmt":"2025-06-10T11:48:18","slug":"pi-control-the-pid-alternative","status":"publish","type":"spl_knowledgebase","link":"https:\/\/webprojects.cloud\/wordpress\/splatco\/knowledgebase\/tutorials-application-notes-and-white-papers\/tutorial-pid-control-with-splat\/pi-control-the-pid-alternative\/","title":{"rendered":"PI Control &#8211; the PID alternative"},"content":{"rendered":"\n<p>PID control is hard.&nbsp; We&#8217;ve got a tutorial that I don&#8217;t understand, but there is something much simpler that&#8217;s drop dead easy to implement in SPLat or any other programming language.<\/p>\n\n\n\n<p>PI control is the way.&nbsp; When we&#8217;ve got some time I&#8217;ll draw some pictures and explain more about it, but our customers have used this for things as diverse as hot air temperature regulation and concrete truck barrel speed control.&nbsp; It works and isn&#8217;t hard to get running quickly.<\/p>\n\n\n\n<p>Here&#8217;s a graph collected from the hot air blower.&nbsp; In this instance:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Kc = 12<\/li>\n\n\n\n<li>Ti = 100<\/li>\n\n\n\n<li>Limit = 70<\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"707\" height=\"403\" src=\"https:\/\/webprojects.cloud\/wordpress\/splatco\/wp-content\/uploads\/2025\/04\/PI-Control.png\" alt=\"\" class=\"wp-image-3506\" srcset=\"https:\/\/webprojects.cloud\/wordpress\/splatco\/wp-content\/uploads\/2025\/04\/PI-Control.png 707w, https:\/\/webprojects.cloud\/wordpress\/splatco\/wp-content\/uploads\/2025\/04\/PI-Control-300x171.png 300w, https:\/\/webprojects.cloud\/wordpress\/splatco\/wp-content\/uploads\/2025\/04\/PI-Control-600x342.png 600w, https:\/\/webprojects.cloud\/wordpress\/splatco\/wp-content\/uploads\/2025\/04\/PI-Control-64x36.png 64w\" sizes=\"auto, (max-width: 707px) 100vw, 707px\" \/><\/figure>\n\n\n\n<p>Colour explanation:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Green = Temperature requested by the user<\/li>\n\n\n\n<li>Red = Measured temperature<\/li>\n\n\n\n<li>Pale Blue = The drive (%) sent to the heater.\u00a0 The heater control is not fully proportional, it only has 8 steps, about 12.5% each.<\/li>\n\n\n\n<li>Gray = The &#8220;<strong>reset<\/strong>&#8221; value &#8211; note it clips at 70 to prevent &#8220;wind-up&#8221;.<\/li>\n<\/ul>\n\n\n\n<p>For your own use, you&#8217;ll have to mess around tuning the kfKc and kfTi values, but it&#8217;s nowhere near as hard as doing a PID.<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\"><br>;algorithm constants<br>kfKc                    fEQU  12.0<br>kfTi                    fEQU  100.0<br>kfLimit                 fEQU  70.0                    ;prevent windup<br><br>;runtime values<br>fTarget                 defFLOAT                      ;target value<br>fMeasured               defFLOAT                      ;current measured value<br>fOutput                 defFLOAT                      ;current value to output<br><br>;algorithm vars<br>fReset                  defFLOAT<br>fError                  defFLOAT<br><br><br>;===============================================================================<br>;DESCRIPTION:<br>; This subroutine is called on a regular tick interval to calculate the next<br>; output value.<br>;PARAMETERS:<br>;  -&gt; Nil<br>;RETURNS:<br>; &lt;-  Nil<br>;===============================================================================<br>subDoPIAlgorithm:<br>   ; Error  = Setpoint - Measured<br>   fRecallQ       fTarget                             ;get the target value<br>   fRecallW       fMeasured                           ;get the actual value<br>   fSub                                               ;calc Target - Actual<br>   fStore         fError<br><br>   ; Reset  = Reset + Kc\/Ti * Error<br>   fLoadQ         kfKc<br>   fMul<br>   fWtoQ<br>   fLoadW         kfTi<br>   fDiv<br>   fRecallQ       fReset<br>   fAdd<br>   fLoadQ         kfLimit                             ;limit integral to..<br>   fGoIfWltQ      _THChkResetLow<br>   fSwap<br>_THChkResetLow<br>   fLoadQ         0.0<br>   fGoIfWgtQ      _THSaveReset<br>   fSwap                                              ;..prevent \"wind-up\"<br>_THSaveReset<br>   fStore         fReset<br><br>   ; Output = Kc * Error + Reset<br>   fLoadW         kfKc<br>   fRecallQ       fError<br>   fMul<br>   fRecallQ       fReset<br>   fAdd<br><br>   ; limit output to 0 - 100%<br>   fLoadQ         0.0<br>   fGoIfWgeQ      _THTestMax<br>   fSwap<br>_THTestMax<br>   fLoadQ         100.0<br>   fGoIfWleQ      _THDoDrive<br>   fSwap<br><br>_THDoDrive<br>   fStore         fOutput<br>   Return<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>PID control is hard.&nbsp; We&#8217;ve got a tutorial that I don&#8217;t understand, but there is something much simpler that&#8217;s drop dead easy to implement in&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":3503,"menu_order":0,"template":"","class_list":["post-3505","spl_knowledgebase","type-spl_knowledgebase","status-publish","hentry"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v25.6 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>PI Control - the PID alternative - SPLat Controls<\/title>\n<meta name=\"robots\" content=\"noindex, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"PI Control - the PID alternative - SPLat Controls\" \/>\n<meta property=\"og:description\" content=\"PID control is hard.&nbsp; 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