Feedback gain, % per degree error Integration time seconds
Demanded temperature: Ambient 20

<![CDATA[ function setup(){ t=0; tmax = 200; demand=60; ambient=20; tank=ambient; pipe= Array(100); for(i=0;i<101;i++){pipe[i]=ambient;} tout=ambient; a=0.1; // Time constant about ten seconds b=7; // Will give 70 degrees temperature rise for u=1. dt = .1; integral=0; tint=20; fbgain=document.getElementById("fb").value/100; tint=document.getElementById("fi").value*100; ScaleWindow(-5,-5,tmax,110); DrawAxes(0,0,tmax,100); Label('Proportional+Integral',150,85); Colour("black"); Label('Output temperature',150,80); Colour("blue"); Label('Target temperature',150,75); Colour("magenta"); Label('Integral %',150,70); Colour("red"); Label('Power %',150,65); Colour("black"); t = 0; i=0; MoveTo(t,tank); loop(); } ]]>
<![CDATA[ function loop(){ integral=integral+(demand-tout)*dt/tint; if(integral>1){integral=1;} if(integral<0){integral=0;} u=(demand-tout)*fbgain+integral; if(u>1){u=1;} if(u<0){u=0;} tank=tank+(a*(ambient-tank)+b*u)*dt; tout=pipe[i]; pipe[i]=tank; i=i+1; if(i>99){i=0;} t = t + dt; Colour("blue"); Spot(t, demand); Colour("magenta"); Spot(t, integral*100); Colour("red"); Spot(t, u*100); Colour("black"); Spot(t, tout); if (t<tmax){setTimeout('loop()',10);} } ]]>