RU2267458C1 - System for checking load stability of mobile load-lifting machine - Google Patents

Abstract

FIELD: mechanical engineering; load-lifting machinery; safeguards.

SUBSTANCE: strain-gauge transducers are installed on outriggers. Analog-digital converter is connected to outputs of strain-gauge transducers. On-board microprocessor is installed for processing data array formed by analog digital converter, control of hydraulic cylinders of support circuit by hydraulic distributor and putting out required information to operator's display. Moreover, on-board microprocessor is furnished with relay module, and mathematical model of load-lifting machine made with possibility of changing, depending on type of load-lifting machine used, is entered into its memory. Additionally hydraulic distributor is connected in parallel with said hydraulic distributor coupled through system of controllers with relay module of on-board microprocessor and designed for re-distribution of liquid from piston spaces of hydraulic cylinders in case of danger of turnover of load-lifting machine.

EFFECT: increased capacity of machine, improved safety at load-handling operations.

2 cl, 3 dwg

Description

The invention relates to the field of crane construction and can be used to control the cargo stability of mobile lifting equipment, mainly boom self-propelled cranes.

A known system of protection of a jib self-propelled crane (see ed. St. N698903. The protection system of a jib self-propelled crane. Zaitsev L.V., Pankrashkin P.V., Kopeikina N.N., Vasin B.G., Lifshits M.I. , Makhorkin N.N., Sysin R.I., Ulitenko I.P. Bull. 43 of 11.25.79), containing threshold transducers of load sensors of the outriggers of the four-support crane, each of which are connected in two in series and two on diametrically located supports parallel circuits, one of the electrical circuits is made of series-connected series and parallel oh chains, and another - of serially connected second serial and second parallel chains connected in series with the output member, the output of which is connected with the alarm unit, consisting of a light (red, yellow and green), and audio elements, and the crane control system.

The protection system of the jib crane is as follows. When the crane is operating, as the tipping moment approaches the restoring pressure, the pressure in the hydraulic cylinders of the outriggers located outside the tipping line drops, and two adjacent supports are unloaded and two contacts of the additional preliminary alarm output element open. In this case, the contact of the green light element opens and the contact closes, including the yellow light element, warning that the tipping moment of the crane is approaching a critical value. With a further increase in the overturning moment, the aforementioned supports are even more unloaded and threshold threshold converters are activated, turning off the yellow light element and including the red one.

A disadvantage of the known system is the low reliability, which reduces the efficiency of the crane, and the inability to form a directed stabilizing effect in the event of an emergency in automatic mode.

The objective of the invention is to increase the productivity and safety level of loading operations performed using mobile lifting machines and providing easily perceptible information to the operator about the current stability of the system in real time in a continuous technological cycle of loading operations. The set of problems is solved by the use of the load stability control system of mobile hoisting machines, which registers signals and provides the necessary information on the scoreboard to the driver and, if there is no reaction on his part, sends a command to the control system equipment that responds accordingly to these signals.

This problem is solved in that the load stability control system of mobile hoisting machines, containing strain gauges and an onboard microprocessor, is made in the form of parallel lines of hydraulic cylinder power pipelines connected to a processor-controlled distributor through a controller system.

To implement the task of monitoring the crane's stable position during operation, it is most appropriate to use the method of determining the crane's cargo stability by the position of the resultant of all forces (projection of the center of mass) acting on the crane relative to the crane support circuit.

In this method, additional effects on the crane are also taken into account: inertia forces, wind, the slope of the working platform, etc., and the numerical value of the cargo stability coefficient of the crane is determined by the formula:

where b 'is the distance from the axis of rotation to the direction line of the resultant of all loads affecting the stability of the loaded crane, l is the distance from the axis of rotation of the crane to the tipping edge.

The invention is illustrated in the drawing (figure 1), which shows a diagram of the reference plane of the crane installation. Figure 1 shows: 1, 2, 3, 4 - supporting hydraulic cylinders; a, b are the distances from the tipping ribs to the center of the support contour; About - the center of the slewing ring; O '- axis of symmetry of the frame; W is the boom suspension plane; C is the position of the center of mass; X is the distance from the center of the slewing ring to the center of the support loop.

Considering the supports as material points at which a certain part of the installation mass is concentrated, the current position of the projection of the center of mass of the system can be determined as follows:

, - полная масса системы; х_i, у_i - координаты i-й опоры.Where

, is the total mass of the system; x _i , y _i - coordinates of the i-th support.

In order to take into account the influence on the stability of dynamic processes, instead of mass, we will consider the total load G _k reduced to the supports, including loads from the dead weight of the crane, cargo, wind and inertial loads. Since this load is distributed as a result along the crane supports, then

G _r = ΣG _i ,

where ΣG _i is the sum of the loads reduced to the ith supports.

The coordinates of the application of the reduced load will be determined by the expressions

where G _i is the load reduced to the i-th support.

The coordinates of the supports will be equal (see figure 1)

x ₁ = x ₄ = -α; x ₂ = x ₄ = α;

y ₁ = y ₂ = b; y ₃ = y ₄ = -b.

Coordinates of the intersection of the axes of symmetry of the frame O '(0; 0).

The coordinates of the projection of the axis of rotation on the reference plane O (-X ₀ ; 0).

Then, starting from (1), we obtain

Similarly

Based on these values, you can also get information about the current values:

- angle of rotation of the boom:

- linear speed of movement:

where T is the polling period of load sensors by the control system, during which point C changes its coordinates from x _cj , y _cj to x _{c (j + 1)} , y _{c (j + 1)} ;

- boom rotation speed

- расстояние от точки С до центра опорного контура;Where

- the distance from point C to the center of the reference contour;

- frame angle

where In _i is the transverse base of the support contour, With _i is the stiffness of the supports.

Accumulating data on the values of these quantities during the process of lifting operations, the control system can form the dependences φ (t), v (t), ω (t), φ ₀ (t) and, by extrapolating, with a certain probability to judge their further change .

(фиг.2).By choosing the position of the projection of the center of mass as a controlled parameter (see Fig. 1) it is easy to show that the maximum value of the safety factor (k = 2) corresponding to the guaranteed stability of the crane installation will be at С _x = 0 and С _y = 0, and the minimum value (k = 1.2) corresponding to a dangerous decrease in stability margin will be at

(figure 2).

The rules of the device and the safe operation of cranes provide for the calculation of the stability of the GPM without dynamic loads. The safety factor for static loads k≥1.4. The value of the safety factor, within 1.2 <k <1.4, corresponds to the control zone, which serves to prevent emergency situations. The area of this control zone will be within the reference contour with a range of coordinates

Figure 2 shows: 1 - region of guaranteed stability; 2 - area of dangerous reduction in stability margin; 3 - control zone. Finding the projection of the center of mass of C inside region 1 ensures a steady state of PMG.

When the projection of the center of mass projection is shifted to the control zone 2, it is necessary to change the parameters of the working operations (reduce the speed of movement, limit the reach of the boom, reduce the moment on the motor shaft), thereby preventing the center of mass from falling into the area of dangerous stability margin reduction.

(k<1,2) проекция центра масс крана (С' на фиг.2) попадает в область опасного снижения запаса устойчивости 2 и ситуация считается аварийной. Создается угроза опрокидывания ГПМ, для предотвращения которой необходимо блокировать все исполнительные системы и осуществить перераспределение (слив) определенного объема рабочей жидкости из поршневых полостей гидроцилиндров, противоположных возможному ребру опрокидывания. Тем самым произойдет равномерная осадка опорного контура крана, что позволит вывести проекцию центра масс в область гарантированной устойчивости.At

(k <1,2) the projection of the center of mass of the crane (C 'in Fig. 2) falls into the area of dangerous reduction of stability margin 2 and the situation is considered emergency. A GPM overturning threat is created, to prevent which it is necessary to block all executive systems and redistribute (drain) a certain volume of the working fluid from the piston cavities of the hydraulic cylinders opposite to the possible overturning rib. Thus, a uniform settlement of the crane support contour will occur, which will allow to bring the projection of the center of mass into the region of guaranteed stability.

The control system functioning algorithm will be as follows:

1. The control system receives information from load sensors mounted on outriggers.

2. According to the formula (2), the current coordinates of the point of application of the reduced load C are determined.

3. The condition for finding this point inside the region of guaranteed stability (1) is verified.

4. The value of the margin of stability determines the maximum allowable increase in load relative to the current value.

5. The control signal to the operating mechanisms of the crane is formed in such a way that this margin remains within the limits allowed by condition (1).

Constant monitoring of the parameters that determine the stability of the crane is carried out by load sensors, the signals from which are fed to the converter for the purpose of presentation in a convenient (digital) form for processing.

The information array thus formed characterizing the state of the system allows one to determine, based on the mathematical model of crane stability, the current value of the safety factor.

The support loads are fixed with the help of integral semiconductor pressure strain gauges of the membrane type installed in the pressure head hydraulic line of the hydraulic jacks of the supports.

Processing of incoming information is carried out using a microprocessor module based on a microprocessor with read-only memory and random access memory.

The implementation of the executive part of the system (installation of the reference circuit) requires minimal modernization of the design of the hydraulic equipment of the reference circuit: a valve controlled by the relay module of the on-board processor is installed in parallel with the existing valve. The modernization of the hydraulic circuit of the reference circuit is shown in figure 3 (shown by a dotted line). The diagram contains the hydraulic cylinders of the outriggers 1, the hydraulic cylinders of the outrigger 2, parallel hydraulic valves 3, hydraulic valves 4, a bypass valve 5.

Distinctive features of the system are: the load moment is not limited by turning off the working mechanisms when the critical value is reached, but by their active control, which does not allow to go beyond the permissible limits; the operator gets rid of the tedious process of frequent switching of the handles and constant monitoring of the parameters on which the accuracy of the performance of the given functions and labor safety depend; the system is universal, since the basis of the algorithms for its operation is the mathematical model of the GPM, located in the memory of the on-board microprocessor device, and can be changed depending on the type of crane and complicated (taking into account the vibrations of the load on the rope, the elasticity of the elements of the metal structure, the deformation of hydraulic cylinders, etc. ) upon presentation of more stringent requirements and as research progresses (i.e. it is resistant to moral aging).

Claims (2)

1. A system for monitoring the cargo stability of mobile hoisting machines, containing strain gauge load sensors mounted on outriggers, an analog-to-digital converter connected to the outputs of the load sensors, an on-board microprocessor installed with the ability to process the information array generated by the analog-to-digital converter, and control the hydrodistributor of the reference hydraulic cylinders circuit and the issuance of the necessary information on the scoreboard to the driver, characterized in that the onboard microprocessor with it is equipped with a relay module, a mathematical model of a load-lifting machine is introduced in the memory of the on-board microprocessor, made with the possibility of changing depending on the type of the load-lifting machine, and an additional hydraulic distributor is connected in parallel with the hydrodistributor connected through the controller system to the relay module of the on-board microprocessor and designed to redistribute the volume of fluid from the piston areas of hydraulic cylinders with the threat of overturning of the lifting machine. 2. The system according to claim 1, characterized in that the on-board microprocessor is configured to periodically determine the position of the projection of the center of mass on the plane of the support contour relative to the tipping edge within the reference contour of the system, to identify the direction of displacement of the projection of the center of mass outside the guaranteed stability region, generating a signal dangerous reduction in the margin of stability and the formation of directional effects of a stabilizing nature to limit speeds or block movements of those technologically equipment.

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