The possibilities of reducing the operational load of hoisting mechanisms in case of dynamic hoisting

Abstract

Article citation info: (*) Tekst artykułu w polskiej wersji językowej dostępny w elektronicznym wydaniu kwartalnika na stronie www.ein.org.pl IntroductionBesides the reliability, main requirements for vertical transport are positioning, use of power and reducing of the dynamic loads. For the hoisting mechanism the worst case in terms of appearing overloads is when the lifting operation starts when ropes have clearance. This case is called a jerk of a payload. The case when the ropes clearance is so big that when the ropes tensing began, the angular speed of the drum is near the reference speed. The research of overloads in drive systems usually comes up in the context of their impact on the steel structures of devices. For example in papers [1], [7] and [11] the tests of load dynamics of steel structures of the overhead cranes during payloads lifting were described. In [14], authors presented the model of the hoisting mechanism, where the stiffness of the girder has been taken into account. In these articles there were presented the studies of the behavior of the cranes structures under dynamic loads using FEM method. In [15] the influence of the hoisting mechanism operation on the crane structure was presented. There were presented waveforms of forces in ropes for different methods of increasing the drum speed from linear to inertial with various time constants. The problem of the crane structures load by vertical dynamic forces appeared also in [4] and [16], where the systems with moving mass were described. Reduction of dynamic overloads made by hoisting mechanisms operation provides measurable exploitation benefits, such as: minimization of the structure overload or reducing the power consumption. There were presented also methods of reduction of the steel structure loads by using dampers, eg. in [9]. Research of overloads of hoisting winches for varies cases of lifting were described in [12]. The authors of [10] worked on modeling of hoisting mechanisms equipped with different drive systems.The authors of [3] paid attention to necessity of consideration the various types of the loads of mechanisms caused eg. by the control methods and the limited scope of application of the cranes automation. The conclusion is that the control systems which reduce a temporary load should be used both for automatic and manual control of hoisting winches.In [5] authors pointed the specificity of drives of hoisting winches, which: "are distinguished with respect of their requirements, regarding the control of speed and position and the acceleration phase carried with an active load". The usage of modern drive systems based on frequency inverters, allows meet these requirements.As can be seen the problem of overloads of hoisting mechanisms appears mainly in context of dynamic loads of supporting structures or research of dynamics of hoisting mechanisms. In our opinion, which is based on reading the available literature, the issues of reduce dynamic loads is presented only in context described above.In the paper there is present...

Energy consumption and overloads of crane hoisting mechanism with system of reducing operational loads

“…The model of hoisting mechanism fed by inverter widely was described inter alia in [6] and model of inverter-motor stator system in [7]. In mechanical Some teams conducted a research of energetic efficiency of motors which were used in hoisting mechanisms fed by inverters.…”

“…The paper presents the continuation of research described in [6] in field of energy consumption in basic methods of payloads lifting, as well as energetic effectiveness of the developed method of dynamic overloads minimization with respect to standard methods of lifting. In addition to the basic methods of payload lifting, the solution to improve the winch operational parameters is included.…”

“…3. The methods of payload lifting sciENcE aNd tEchNology lifting of lifted payload (ropes pre-strained -introduced sign --pow) lifting a payload from the ground (ropes not strained -intro--duced sign -z) jerk of a payload (ropes with clearance, straining began when a -motor operate with steady speed -introduced sign -podr) In addition, the method allowing minimisation of dynamic -overloads of the drive using proper shape of input function, described in [6] was considered-introduced sign -podr_k Exemplary, taken from model tests time charts of input function and force in ropes for considered cases are presented in figure 3.…”

“…The tests could be carried out thanks to verification tests presented inter alia in [6]. The experimental data acquisited during tests on hoisting winch were used and compared with values calculated numerically with assumption of the same input functions.…”

Modeling the dynamics of cargo lifting process by overhead crane for dynamic overload factor estimation

“…In the performed simulations it was assumed, that pick up a load from the ground occurs when achieving the nominal speed of the motor. Article [24] presents a particular approach to the electric part of the hoisting mechanism and the associated algorithm for controlling the drive inverters. In the end, giving satisfactory results as to the reduction of the dynamic forces by signals related to the angular velocity of the motor shaft or measuring the force on the equalizing disc, which is confirmed by the results of tests on a real object.…”