D	internal diameter of a derrick cylinder
lB	Initial length before boom extension
lB 1	distance from point O to the center of mass of the first boom
lB 2	distance from point O to the center of mass of the second boom
ldl	distance after the derrick cylinder extends
ldl_i	initial distance before the derrick cylinder extends
lTR	distance from point O to the center of mass of a telescopic cylinder (rod)
lTS	length after boom extension
lTT	distance from point O to the center of mass of a telescopic cylinder (tube)
MB	moment of force caused by the boom’s own weight
MD	moment of force caused by the derrick cylinder’s own weight
O	rotation center of the boom
P	center point connecting a derrick cylinder with a boom
R	rotational radius of a derrick cylinder
W	lifting load of a cargo crane
WB 1	weight of the first boom
WB 2	weight of the second boom
Wmax	maximum lifting load of a crane
Wmax_bc	best-fit curve of the maximum lifting load
WTR	rod weight of a telescopic cylinder
WTT	tube weight of a telescopic cylinder
α	assembly angle of a derrick cylinder
β	angle between the centerline of the derrick cylinder and an imaginary line connecting points o and p
ΔP	tube pressure of a derrick cylinder
θ	luffing angle of the boom
θ 1	luffing angle variable to find the maximum lifting weight
θc	luffing angle at which the boom can descend the lowest based on its current angle
θnew	luffing angle of the boom measured in real time