E~ = (m/M)^D (v1/v2)^(D-1)
F~ = tau^2 (m/M) ⊙ (a / (x - x_c))
P~ = (h/H) ⊙ (g/G)
F~r = −mu_f ⊙ (N/Nref) ⊙ sgn(v)
F~net = F~ + P~ + F~r
S = tanh(lambda · (F~net_x + F~net_y)/2)
M ← (1−mu)M + muS