RU2803775C1 - Method of experimental determination of rigidity of the rope suspension for bridge type cranes - Google Patents

Abstract

FIELD: crane lifting.

SUBSTANCE: invention is related to hoisting and transport engineering and, above all, to overhead cranes. A load of nominal weight is lifted and at the same time the force in the ropes and their deformation are measured, on the basis of which the function of the rigidity of the rope suspension from the force in it is calculated, the dependence of the force in the ropes on their deformation, the dependence of the deformation of the ropes on the force in them, and the deformation of the ropes is determined by integration of data of the speed sensor of the electric motor of the drive of the lifting mechanism, taking into account the gear ratio of the gearbox, the diameter of the drum, the multiplicity of the chain hoist and the stiffness of the span metal structure according to the formula.

EFFECT: ability to obtain a real characteristic of the rigidity of the rope suspension in the entire range of working tensions of the rope.

3 cl, 6 dwg

Description

Field of technology

The invention relates to the field of hoisting and transport engineering and, above all, to overhead cranes.

State of the art

Existing safety devices for overhead cranes: load limiters and parameter recorders, use a linear characteristic of rope tension from their deformation, proportional to the movement of the rotating parts of the drive and, accordingly, the time of the stage until the load is lifted from the base, which leads to an error in predicting the load on the lifting mechanism. In addition, the representation of the rigidity of the rope suspension with a constant value causes an error in determining the moment of stopping the drive when trying to lift a load of unacceptable mass and the period of oscillation of loads of mass less than the nominal one, which contributes to a decrease in the quality of work of the load limiting algorithms and the accuracy of calculating the weight of the lifted load by parameter recorders.

Methods for determining the stiffness of ropes are known from the prior art. Patent RU 2435153 C1 (publication date: November 27, 2011) describes the design of a stand that provides simultaneous measurement of the tension of the elastic element and the movement of the collet clamp.

The disadvantage of the described approach is the bench design, which requires dismantling the rope every time there is a need to determine its rigidity. At the same time, the rigidity of the ropes, although it makes the main contribution to the overall rigidity of the rope suspension, is not the only component. Thus, the indirectness of the considered method causes an error in determining the parameter under study.

There is a known method for monitoring the technical condition of ropes in mine lifting installations, based on determining the rigidity of the rope during its elongation under the influence of gravity of a pre-loaded lifting vessel RU 2578732 C2 (publication date: 03/27/2016).

The disadvantage of this method is that it is not applicable in its original form to pulley systems, as well as the need to determine the amount of rope deformation by directly changing the movement of the lifting vessel.

In the method described in patent RU 2780959 C1 (publication date: 10/04/2022), the rope loading is determined by measuring the tension of the stationary branch of the tackle system, and the amount of rope elongation is calculated based on the change in the angle of rotation of the winch drum during the rope loading process. This method is adopted as a prototype.

The disadvantages of this method are:

1. Determination of the rigidity of the rope suspension as a constant value characterizing the current state of the rope, and depending only on the degree of wear, but not on the force in the rope.

2. A method for determining the deformation of ropes based on data on the angle of rotation of the winch drum. Since the movement of the drum is less than the corresponding movement of the motor shaft, the error when calculating the movement of the drum by similar equipment will be a number of times equal to the gear ratio greater than when calculating the movement of the motor shaft.

3. The method does not take into account the deformation of other elements of the elastic system. Thus, the applicability of the method for bridge-type cranes is limited to the position of the load trolley only above the bridge supports, since this position corresponds to the maximum rigidity of the supporting metal structure and the smallest error from the fact that the rigidity of this elastic element is not taken into account.

A feature of the prototype that is common to the claimed method is the determination of the rigidity of the rope suspension by an experimental method on a functioning lifting mechanism by simultaneously measuring the deformation of the rope suspension and the force in the rope.

Disclosure of the Invention

The objective of the invention is to increase the level of security of overhead cranes by improving the operation of existing load limiter algorithms by more accurately calculating the moment the drive stops and improving the operation of the operating parameters recorder by more accurately calculating the period of oscillation of the load based on the use of an experimental characteristic of the rigidity of the rope suspension, which depends on the force in the ropes.

The proposed method makes it possible to obtain a real characteristic of the rigidity of a rope suspension over the entire range of operating tensions of the rope, in contrast to existing methods that determine one value of rope stiffness for all levels of loads in it.

The problem is solved by the fact that the method of experimentally determining the rigidity of a rope suspension for bridge cranes is to lift a load of nominal weight and simultaneously measure the force in the ropes and their deformation, on the basis of which the function (dependence) of the rigidity of the rope suspension on the force in the ropes is calculated .

The function of the rigidity of a rope suspension from the force in the ropes is described by formula (1):

s _to (S) - experimental characteristic of the rigidity of the rope suspension;

S - force in ropes;

a _i is the i-th coefficient of a polynomial of the third degree, approximating the dependence of the force in the ropes on their deformation;

b _j - j-th coefficient of a third degree polynomial approximating

dependence of the deformation of ropes on the force in them.

In this case, the dependence of the force in the ropes on their deformation has the form (2):

x is the value of the current rope deformation,

and the dependence of the deformation of the ropes on the force in them has the form (3):

The coefficients a _i and b _j in expressions 2 and 3 are determined by approximating experimental data: the force in the rope and the speed of the electric motor.

The force in the ropes in the case of installing a force sensor in the drum support is determined by formula (4):

F - load on the force sensor;

p is the multiplicity of the pulley.

If a load cell is installed in a rope system, the force in the ropes is determined by direct measurement.

In this case, the deformation of the ropes is determined by integrating the data from the speed sensor of the electric motor of the drive of the lifting mechanism, taking into account the gear ratio of the gearbox, the diameter of the drum, the multiplicity of the pulley and the rigidity of the span metal structure in accordance with formula (5):

x(t) - function of rope deformation versus time;

n(t) - experimental function of the speed of the electric motor of the lifting mechanism versus time;

D - drum diameter;

and - gear ratio of the gearbox;

S(t) is the experimental function of the force in the rope versus time;

с _m - stiffness coefficient of the span metal structure.

The described method allows, by transitioning in the load limiter algorithm from a linear function of the force in the ropes from their deformation to the function described by expression (2), to increase the accuracy of determining the moment the drive stops, which makes it possible to fulfill the requirement of prohibiting the lifting of an unacceptable mass from the base of a load;

and also the method increases the accuracy of determining the mass of lifted loads by adjusting the buffer length parameters in the recorder algorithm by taking into account in the formula for calculating it the variable rigidity of the rope suspension according to formula (1).

List of figures

Fig. 1. Scheme of implementation of the method for experimentally determining the rigidity of a rope suspension for overhead cranes.

Fig. 2. Scheme of implementation of the method for experimentally determining the rigidity of a rope suspension for overhead cranes.

Fig. 3. Experimental graph of force in ropes versus time.

Fig. 4. Experimental graph of the speed of the electric motor, reduced to the translational motion of the rope suspension, versus time.

Fig. 5. Time dependence of the deformation of the span metal structure.

Fig. 6. Experimental characteristics of the rigidity of the rope suspension.

Carrying out the invention

The invention is illustrated in Fig. 1 diagram. The method for experimentally determining the rigidity of a rope suspension 1 is that during the process of lifting a load of nominal weight 2 by device 3, the force in the ropes and their deformation are simultaneously recorded in the memory. In this case, at the initial moment the ropes must sag, which is the condition for the absence of force in them, and at the final moment the load must come off the base. In this case, the resulting characteristic will describe the rigidity of the rope suspension over the entire range of permissible loads. In the case of symmetrical winding of the rope on the drum, the force in the rope is determined using sensor 4 installed in the drum support, according to formula 2.

When the rope is wound asymmetrically on the drum, the force is determined by direct measurement using a sensor installed in the rope system, for example, on the idle branch of rope 5.

It is rational to determine the deformation of the rope based on data on the movement of the electric motor shaft, which causes a smaller error when using similar measuring instruments in comparison with direct measurement of the movement of the end of the rope or the rotation of the rope drum.

When lifting with pick-up - a mode in which, at the moment the tension of the ropes begins, the electric motor operates on a stable branch of the natural characteristic - the speed of the electric motor changes slightly. In this case, the dependence of the rope deformation on time is calculated at the rated speed of the electric motor. However, most control systems for lifting mechanisms of real cranes do not allow lifting a load with pick-up, which causes the electric motor to operate at one of the permissible artificial mechanical characteristics. In this case, as the force in the ropes increases, the engine speed decreases proportionally. To take into account the decrease in the lifting speed, the electric motor 6 is equipped with a sensor 7 of the current speed of rotation of the output shaft.

To determine the deformation of the ropes, the data from the electric motor speed sensor is integrated, taking into account the gear ratio of the gearbox 8, the multiplicity of the pulley 9 according to formula 6:

In this form, the formula is applicable only for the position of the cargo trolley above the supports 10, since it does not take into account the deformation of the span metal structure 11. The universal type of dependence for the deformation of the rope at an arbitrary position of the cargo trolley in the crane span is represented by formula (5).

Having the dependence of the force in the ropes on time S(t) and their deformation on time x(t), by eliminating the common parameter - time - a graph of the force in the ropes on their deformation S(x) is obtained.

As a function that approximates the graph of the force in ropes from their deformation, a third-degree polynomial is used (formula 2), which makes it possible to implement two zones of curvature corresponding to theoretically fixed areas of large and small nonlinearity, and at the same time filter out parasitic high-frequency oscillations.

The dependence of the deformation of ropes on the force in them is similarly approximated (formula 3). Then, having the coefficients a _i and b _j of functions (2) and (3), by substituting them into formula (1), an experimental characteristic of the rigidity of the rope suspension is obtained. The proposed method for experimentally determining the rigidity of a rope suspension is implemented using a device, the functional diagram of which is presented in Fig. 2, where the digital computing unit (12) receives information from the information input unit (13), the engine speed sensor (14), the rope force sensor (15) and the real-time clock (16). There is two-way communication between the digital computing unit (12), the long-term memory unit (17) and the communication unit (18). The digital computing unit (12) outputs visual information through the display unit (19) to external equipment (20).

Using the information input block, identification information is set: the rigidity of the span metal structure, the gear ratio of the gearbox and the multiplicity of the pulley. During the lifting operation of the mechanism, with the help of engine rotation speed sensors and the force in the rope, the corresponding parameters are recorded in the memory depending on time by a digital computing unit: Fig. 3 and Fig.4. In this case, using the gear ratio and the multiplicity of the pulley, the engine speed is recalculated into the deformation rate of the ropes.

Using a real-time clock, the rate of change in rope deformation and the forces in the ropes are synchronized. Then, the digital computing unit carries out the procedure for integrating the engine speed data. The result of integration - a graph of the movement of rotating masses versus time, is presented in Fig. 5.

Next, the digital computing unit, based on recording the force in the ropes as a function of time and the deformation of the ropes as a function of time, constructs, by eliminating the general parameter (time), the dependence of the tension in the ropes on the deformation of the ropes and approximates this dependence with a third-degree polynomial: Fig. 6. The resulting dependence is stored in a long-term memory unit or transmitted via a communication unit to external equipment, for example, a load limiter or a crane operating parameters recorder. At the end of the process, an error message or a successful receipt of the dependence of the rigidity of the rope suspension is displayed on the display unit.

Examples of implementation of the invention

The implementation of the method was carried out on an overhead crane with a lifting capacity of 2 tons when lifting a nominal load. At the same time, using a DNA-1 clamp-on strain gauge and a DIY encoder mounted on the motor shaft of the lifting mechanism, the force in the rope (Fig. 3) and the engine rotation speed (Fig. 4) were recorded at the stage of tensioning the ropes until the load was lifted from the base. By integrating the encoder signal data taking into account the parameters of the drum diameter D=0.5 m, the gear ratio u=32 and the rigidity coefficient of the span metal structure with _m =1.92⋅10 ⁷ Based on dependence (5), a graph of rope deformation versus time was obtained (Fig. 5).

Based on the records of the force in the ropes versus time S(t)[H] (Fig. 3) and the deformation of the rope x(t)[m] (Fig. 5) by eliminating the general parameter - time - a graph of the force in the ropes versus their deformation is obtained S(x)[H] (Fig. 6). The graph (Fig. 6) is approximated by a third-degree polynomial according to formula (2); for the example under consideration, the values of the polynomial coefficients are equal to:

and the coefficients of the polynomial approximating the inverse graph - the deformation of the rope from the force in it - are equal to:

The rigidity of the rope suspension is determined by substituting into formula (1) the corresponding dimensionless coefficients of the approximating polynomials a _i and b _j :

Claims (26)

1. A method for experimentally determining the rigidity of a rope suspension for bridge-type cranes, which consists in lifting a load of nominal weight and simultaneously measuring the force in the ropes and their deformation, on the basis of which the function of the rigidity of the rope suspension from the force in the ropes is calculated, characterized in that the rigidity rope suspension is determined by the formula c _k is the experimental value of the rigidity of the rope suspension; S - force in ropes; a _i is the i-th coefficient of a third-degree polynomial, approximating the dependence of the force in the ropes on their deformation; b _j - jth coefficient of a third-degree polynomial, approximating the dependence of rope deformation on the force in them, in this case, the dependence of the force in the ropes on their deformation has the form: x - the magnitude of the current deformation of the rope, and the dependence of the deformation of the ropes on the force in them has the form: the coefficients of which (a _i and b _j ) are determined by approximating experimental data: the force in the rope and the speed of the electric motor; in this case, the deformation of the ropes is determined by integrating the data from the speed sensor of the electric motor of the drive of the lifting mechanism, taking into account the gear ratio of the gearbox, the diameter of the drum, the multiplicity of the pulley and the rigidity of the span metal structure in accordance with the formula: x(t) - experimental function of rope deformation versus time; n(t) - experimental function of the speed of the electric motor of the lifting mechanism versus time; D - drum diameter; p - pulley multiplicity; u is the gear ratio of the gearbox; S(t) is the experimental function of the force in the rope versus time; с _m - stiffness coefficient of the span metal structure. 2. The method according to claim 1, characterized in that if a load sensor is installed in the drum support, the force in the ropes is determined by the dependence: F - load on the force sensor. p is the multiplicity of the pulley. 3. The method according to claim 1, characterized in that if a load sensor is installed in the rope system, the force in the ropes is determined by direct measurement.