Objective function $f (X)$	Iteration curve
$\begin{array}{l} f_{1} (X) = - [{(S L L_l)}^{2} + {(S L L_r)}^{2}] \\ θ_{i} = 90^{\circ} \end{array}$
$\begin{array}{l} f_{2} (X) = {(S L L_l - S L L_i)}^{2} + {(S L L_r - S L L_i)}^{2} \\ θ_{i} = 90^{\circ} \end{array}$
$\begin{array}{l} f_{3} (X) = s q r t (s u m ({(Δ E - m e a n (Δ E))}^{2}) / m) \\ θ_{i} = 90^{\circ} \end{array}$
$\begin{array}{l} f_{4} (X) = s q r t (s u m ({(Δ E - m e a n (Δ E))}^{2}) / m) \\ θ_{i} = 20^{\circ} \end{array}$