.PS
gen_init
  linewid = linewid*0.8
  circlerad = 0.35/2
  bw = boxwid/2
  bh = boxht/2

Nonlinear: [boxwid = boxwid*3/2; boxht = boxht*3/2
  thicklines_
  scale = 0.8
  circlerad = 0.3/2
R: box "reference" "$R$"
   arrow right linewid*4/3 "${y_c}_{\hbox{\scriptsize ref}}$" above
Gh: box "```inverse'''" "$\hat G$"
   arrow from Gh.s down "${y_m}_{\hbox{\scriptsize ref}}$" ljust
E: circle
   arrow from E.e right "$e$" above
   box "stabilizer" "$K$"
   arrow "$\delta u$" above
D: circle
   line from Gh.e to (D,Gh.e) "$u_{\hbox{\scriptsize ref}}$" above; corner
   arrow to D.n
   arrow from D.e right "$u$" above
G: box "plant" "$G$"
   arrow <- from G.n up boxht/2 
   "disturbance $z$" above
   arrow right from G.e + (0,boxht/4)
   "$y_c$" ljust
   arrow right from G.e + (0,-boxht/4)
   "$y_m$" ljust
   move to last arrow.c
   arrow down Here.y-G.s.y+boxht*2/3 then left Here.x-E.x then to E.s
   "$-$" at Here + (-0.15,-0.1)
   arrow <- down from R.s
   "$W$ control input" at Here - (0,0.1)
UL:R.nw +(-boxht/2,boxht/2)
UR:(D.e,UL) + (0.1,0)
   line dashed from UL to UR then to (UR,G.s+(0,-boxht*3/2))
   line dashed to (Gh.w,Here) "Controller" above
   line dashed to (Here,Gh.s+(0,-boxht/2))
   line dashed to (UL,Here) then to UL
] #with .nw at last [].sw + (0,-0.25)
# "Nonlinear feedforward (for performance) and small-signal feedback
#    (for stability)" below ljust at Nonlinear.sw+(0,-5pt__)
.PE