Change target as the model runs: target = 0

<![CDATA[ // Setup window tmax=20; ScaleWindow(-1,-20,tmax,20); DrawAxes(0,-20,tmax,20); Label('Predictive control - third order - twin models - no slugging',1,18); Colour("black"); t=0; x=10;v=0;a=0; MoveTo(t,x); StepModel(); ]]>
<![CDATA[ //function loop() var ufp = 1; var ufn = -1; //reset both models afp=a; vfp=v; xfp=x; afn=a; vfn=v; xfn=x; tf=0; do{ //step positive model afp = afp + ufp * dtf; vfp = vfp + afp * dtf; xfp = xfp + vfp * dtf; Colour("green"); Spot(t+tf, xfp); //step negative model afn = afn + ufn * dtf; vfn = vfn + afn * dtf; xfn = xfn + vfn * dtf; Colour("red"); Spot(t+tf, xfn); tf+=dtf; offp=(afp<0)|(vfp<0)|(xfp<xtarget); //positive offside? offn=(afn>0)|(vfn>0)|(xfn>xtarget); //negative offside? } while(offp&&offn); //loop while both are offside if(offp){u=1;}else if(offn){u=-1;} else {u=0;} //if one of them is still offside, that is the value for u dt=tf/ratio +.004; //plant step increases with time to decision Colour("black"); MoveTo(t, x); a = a + u * dt; v = v + a * dt; x = x + v * dt; t = t + dt; LineTo(t, x); Colour("blue"); Spot(t, 10*a); if (t<tmax){ setTimeout('StepModel()',4+1000*dt); } ]]>