The dynamic control method of the weight cargo transported lifting machinery

The problem of improving the safety of the use of lifting machinery is particularly relevant for regions where intensive industrial and civil construction is carried out. To date, a significant amount of work has been done, designed at the theoretical level to justify the design and safe operation of lifting machinery. However, the existing methods of control of the total weight of the cargo transported by the lifting machinery are based mainly on the strain measurement methods developed in the second half of the twentieth century. The main disadvantage of systems that implement the strain measurement method is the need to integrate the weighing module directly into the design of the lifting machinery. A significant number of accidents of hoisting machines indicates the fuzzy operation of the protection systems of hoisting machines from overload, made on the basis of tensometric methods. As shown by the results of studies in the operation of various types of electric motors under load torque fluctuations occur at the rated speed. The use of this pattern allows weighing the cargo by the dynamic method transported by a lifting machinery. This article is devoted to the development and scientific and technical substantiation of the method of dynamic control of the weight of the cargo transported by the lifting machinery, based on the analysis of the dynamics of the angular accelerations of the rotor of the electric motor of the lifting drive.


Introduction
The problem of increasing the safety of using lifting machinery is particularly relevant for regions in which intensive industrial and civil construction is carried out [1,2].
To date, a significant amount of work has been carried out, designed at the theoretical level to substantiate the design and safe operating modes of lifting machinery [3,4].
However, the existing methods of controlling the total weight of cargo transported by a lifting machinery are based mainly on strain gauge measurement methods [5,6], developed in the second half of the twentieth century. The main disadvantage of systems that implement strain gauge measurement is the need to integrate the weighing module directly into the design of a lifting machinery. A significant number of accidents of lifting machines indicates a lack of clarity in the operation of systems for protecting lifting machines against overload, based on strain gauge methods. Thus, to date, the actual task is the development of methods for controlling the weight of the cargo transported by a lifting machine, including those development on the basis of new physical principles.

The development dynamic method of controlling the weight of the cargo transported lifting machinery
As the results of studies [7][8][9][10][11] show, when various types of electric motors are operating under load, torque oscillations occur at the nominal speed. The use of this pattern allows weighing of the cargo by the dynamic method transported by a lifting machinery.
Consider a system of lifting cargo with a lifting device (figure 1). According to [12], the reduced moment of inertia of the system of rotating loads is the moment of inertia of the system, consisting only of elements rotating with the angular velocity of the electric motor shaft but having a kinetic energy reserve equal to the kinetic energy reserve of the actual system.
From the condition of invariance of the kinetic energy it follows that for a system consisting of an electric motor 1, a clutch with an electromagnetic brake 2, a reducer 3, a gear coupling 4, a drum 5, assuming a small resistance to movement from the air in comparison with other components, we obtain  From here the required reduced moment of inertia of the system is ; The gear ratio between the motor and the drum is i . Then (2) can be represented as The dependence of the motor torque on the rotor speed of the motor, expressed through the angular acceleration of the rotor of the motor and reduced to the axis of rotation of the rotor of the motor, is the inertia moment of the rotating and translational movement cargo of the lifting machinery, where ) ( 1   -angular acceleration of the rotor of the electric motor during acceleration of the electric motor 1 of the lifting machinery without cargo 6.
The calculated equation of torque during acceleration of the electric motor 1 of the lifting machinery with a cargo of 6 weight т: where ) ( 2   -angular acceleration of the rotor of the electric motor during acceleration of the electric motor 1 of the lifting machinery with a cargo of 6 weight тcargo. Equating (5) and (6), we determine the weight of the cargo тcargo: Similarly, the dynamic method of controlling the weight of the cargo transported by the lifting machinery, based on the equality of the traction forces developed by the drum during acceleration without cargo and with the cargo, can be solved on the basis of the analysis of the dynamics of linear acceleration. Figure 2 shows the implementation of the proposed dynamic method of controlling the weight of the cargo lifting machinery. The lifting machinery 1 is equipped with a cargo fixing device 2, on which a cargo of unknown weight 3 is fixed.
Implemented the proposed dynamic method of controlling the weight of the cargo transported lifting machinery as follows.
At the initial stage, the cargo securing device 2 does not fix the cargo of an unknown weight 3. The cargo securing device 2 weight тCSD when lifting in a given altitude interval with a specific law of change in the frequency of the power supply drive motor voltage rise is reported acceleration a.
Then the cargo securing device 2 with weight тCSD is returned to the height of the beginning of the implementation of the initial stage and the cargo 3 of unknown weight тcargo is fixed on it. The device for fixing the cargo 2 and a cargo of unknown weight 3 rigidly fixed on it when lifting in the same predetermined height range with the same specific law of changing the frequency of the power supply motor driving the voltage increase is reported by acceleration a1.
The force applied to the cargo securing device 2 and the cargo of an unknown weight 3, from the side of the lifting motor drive, we denote by F.
We write the projections of the acting forces on the axis Oy for the first and second lifts: where g -acceleration of gravity.
Since the law of voltage variation in the supply network during the first and second lifts was identical, the force applied by the sides of the drive electric motor of lift F developed during the first and second lift the same.

Conclusion
The dynamic method of controlling the weight of the cargo lifting device will allow you to signal the excess of the permissible weight of the cargo directly at the beginning of the lifting of the cargo. An application for the invention of the Russian Federation was submitted to the presented dynamic method for controlling the weight of the cargo on a lifting device based on the analysis of vertical accelerations [13].