Lifting platform based on parallel levers and linear actuator

U ovom radu predstavljen je koncept podizne platforme na bazi paralelnih poluga s linearnim aktuatorom, pri čemu je za aktuator predložen inverzni mehanizam koji opisuje inverznu funkciju u odnosu na prijenosnu funkciju osnovnog dijamantnog mehanizma. Osnovni dijamantni mehanizam je dakle zrcaljen iz x – y ravnine u x – z ravninu, sve u svrhu postizanja konstantnog prijenosnog omjera. Pri sintezi mehanizma, postavljena su ograničenja raspona kuta poluge te je izveden izraz za odnos između zadanog raspona visine i duljine poluge. Također još jedan od uvjeta pri odabiru duljine poluge je bio i udaljenost oslonca platforme od ruba platforme, jer se za velike udaljenosti između ruba i oslonca pojavljuju velike sile u sustavu kada je sila tereta na rubu platforme. Nakon odabira duljine poluge, izvršen je približni izračun sile u osloncima s obzirom da je nosiva platforma statički neodređena. S izračunatom približnom proračunskom silom dimenzionirali su se konstrukcijski elementi i članovi mehanizma, te je provedena kontrola čvrstoće i krutosti kritičnih dijelova mehanizma. Za linearni pogon odabran je teleskopski hidraulični cilindar koji ima jako male gabaritne dimenzije, nasuprot elektromotornom pogonu s navojnim vretenom koji sadrži puno više komponenata i zauzima puno veći prostor. Naposlijetku, napravljena je FEM analiza kritičnih komponenti članova mehanizma, u kojoj je potvrđeno da maksimalna naprezanja ne prelaze dopuštena naprezanja prema HMH teoriji. U konstrukcijskoj razradi korišteni su gotovi standardni čelični profili, te klizni i samoudesivi klizni ležaji u zglobovima poluga. Također, izrađena je i tehnička dokumentacija podizne platforme.This paper presents the concept of a lifting platform based on parallel levers with a linear actuator, whereby an inverse mechanism is proposed for the actuator, which describes the inverse function in relation to the transmission function of the basic diamond mechanism. The basic diamond mechanism is therefore mirrored from the x-y plane in x-z plane, all for the purpose of achieving a constant gear ratio. When synthesizing the mechanism, the limits of the range of the angle of the lever were set and an expression was derived for the relationship between the given height range and the length of the lever. Also another of the conditions when choosing the length of the lever was the distance of the support of the platform from the edge of the platform, since for long distances between the edge and the support, large forces appear in the system when the load force is on the edge of the platform. After selecting the length of the lever, an approximate calculation of the force in the supports was carried out, since the platform is statically indeterminate. With the calculated approximate force that appear in supports, the structural elements and members of the mechanism were designed, and a control of the strength and rigidity of the critical parts of the mechanism was carried out. For linear drive, a telescopic hydraulic cylinder is selected, which has very small gabarite dimensions, opposite an electric motor drive with a screw spindle that contains much more components and takes up much more space. After all, a FEM analysis of the critical components of the members of the mechanism was made, in which it was confirmed that the maximum stresses do not exceed the permissible stresses according to HMH theory. In the construction elaboration, ready-made standard steel profiles were used, as well as plain and spherical plain bearings in the joints of the levers. Also, technical documentation of the lifting platform was made