Bu6ng thang cUa thang may cAn phai dting chinh xac so voi m~t bang cua Uing cAn dung sau khi iln nut dung. Neu buang thang dung khong chinh xac se gay ra cac hi~n tUQng sau :
- D6i v6i thang may cha kMch, lam cho hanh khAch ra, vao kho khAn, tAng- thai gian re, vilo cua hanh khach, dAn d~n giam nAng suilt.
- D6i v{Ji thang may chb hang, gAy kho khAn trong vi~ xep va Mc da hang. Trang mtit s6 trubng hQP c6 th~ kht"lng tht,!c hi~n dUQc vi~ x~ vA Mc da hang.
D~ kh~c phl,lc h(,-u qua do, co th€ c'(n nhAp nut ba:m d~ df).t dUQc dti chinh xac khi dung, nhung se dAn Mn cae vc'(n de kh6ng mong mu6n sau
- Hong thi(~"t bi di~u khi~n - GAy t6n th!t nling lUQng - GAy t6n th!t nling lUQng
- GAy h9ng hOc clk thi~t hi Cd khi - TAng thbi gian tu luc ham d~n dung.
D~ dung chinh xlie bu6ng thang, din dnh den m(jt ntra hi/[!u 56 cua hai quang duang truQt khi phanh buang thang dc'(y Uti va phanh bu6ng thang kht"lng tAi thea cung mQt huang di chuy~n. Cac yeu to anh huang d~n dung chinh xac bu6ng thang bao gam : momen cua co cllu phanh, mt"lmen quan dnh cua buang thang, t6c d¢ khi b~t dAu ham va mOt s6 yeu to phl,l khac.
Qua trlnh ham bu6ng thang xity ra nhu sau : khi bu6ng thang di dlin gan san tang, dIng tAc chuy€n d6i tang dip l~nh Mn h¢ th6ng dieu khi~n d(lng cd d~ dung buang
'.
thang. Trang quAng thbi ,gian 6.t (thbi man tac dQng cua thi~t bi di~u khi~n), bu6ng
thang di dUQc quAng dubng IA
S' = voAt , [m] (3-7)
Trang d6 : v 0 - T6c dQ hic bAt dllu ha.m, [m/s].
Khi co c!1'u phanh mc dQng IA qua trlnh hAm bu6ng thang. Trong thbi gian nAy, bu6ng thang di dUQc m¢t quang duong S".
mv'
S" = 0 , [m]
2(Fph ± FJ (3-8)
Trang do : m - kh6i IUQng cAc phl1n chuygn dQng cua bu6ng thang, [kg] F ph - h,1c phanh, [Nl
Fe - h,1c can dnh, [N]
Dau (+) ho~c tru (-) trong bieu thuc (3-8) phl:l thuQc va~ chh~u tac dvng clla h,tc Fe: Khi bu6ng thang di l@n (+) va khi bu6ng thang di xu6ng (-).
S" cung cd the vi~t duO'i df).ng sau :
S" = (3-9)
Trang do : J - mOmen quan dnh M quy d6i v~ chuy~n d¢ng Clla bu6ng thang, [kgm2] MPh - momen rna sat, [N]
Me - mOmen can tlnh, [N]
Wo - Mc dQ quay cua d¢ng co Iuc bAt dl1u phanh, [rad/s] D - dubng klnh puli keo cap, [m]