CN112551398A - Self-weight amplitude-falling hydraulic control method and system and crane - Google Patents

Self-weight amplitude-falling hydraulic control method and system and crane Download PDF

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Publication number
CN112551398A
CN112551398A CN202011444918.7A CN202011444918A CN112551398A CN 112551398 A CN112551398 A CN 112551398A CN 202011444918 A CN202011444918 A CN 202011444918A CN 112551398 A CN112551398 A CN 112551398A
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amplitude
pressure
maximum
falling
current
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CN112551398B (en
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杨耀祥
陆晓兵
杨浩波
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Sany Automobile Hoisting Machinery Co Ltd
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Sany Automobile Hoisting Machinery Co Ltd
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B66HOISTING; LIFTING; HAULING
    • B66CCRANES; LOAD-ENGAGING ELEMENTS OR DEVICES FOR CRANES, CAPSTANS, WINCHES, OR TACKLES
    • B66C23/00Cranes comprising essentially a beam, boom, or triangular structure acting as a cantilever and mounted for translatory of swinging movements in vertical or horizontal planes or a combination of such movements, e.g. jib-cranes, derricks, tower cranes
    • B66C23/62Constructional features or details
    • B66C23/82Luffing gear
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/02Systems essentially incorporating special features for controlling the speed or actuating force of an output member
    • F15B11/04Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/08Servomotor systems without provision for follow-up action; Circuits therefor with only one servomotor

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • General Engineering & Computer Science (AREA)
  • Fluid-Pressure Circuits (AREA)

Abstract

The invention relates to the technical field of engineering machinery, and provides a self-weight amplitude-falling hydraulic control method and system and a crane. The self-weight amplitude falling hydraulic control method comprises the following steps: acquiring the pressure of a rodless cavity of the luffing cylinder in real time, and correcting the maximum control current in real time according to the pressure of the rodless cavity; acquiring the opening of an electric control handle, and determining a control current according to the corrected maximum control current and the opening of the electric control handle; and the amplitude-variable balance valve communicated with the rodless cavity adjusts the opening degree of a valve core of the amplitude-variable balance valve according to the control current. According to the self-weight amplitude falling hydraulic control method provided by the invention, the maximum control current is corrected in real time according to the real-time pressure of the rodless cavity, so that any opening of the electric control handle corresponds to a constant amplitude falling speed, and the operation of uniform amplitude falling is greatly simplified under the condition of ensuring uniform amplitude falling.

Description

Self-weight amplitude-falling hydraulic control method and system and crane
Technical Field
The invention relates to the field of engineering machinery, in particular to a self-weight amplitude-falling hydraulic control method and system and a crane.
Background
The dropping amplitude performance of the automobile crane is one of important indexes for measuring the maneuverability of the automobile crane. At present, medium and small tonnage automobile cranes all adopt a dead weight amplitude falling mode, namely, a rod cavity of an amplitude-changing oil cylinder does not feed oil, and amplitude falling is realized by generating a vertically downward component force completely depending on the gravity of a large arm. In the amplitude falling process, the amplitude falling speed is adjusted by adjusting the opening degree of a valve core of an amplitude variation balance valve communicated with the rodless cavity of the amplitude variation oil cylinder.
Under the condition that the opening of the amplitude variation balance valve is unchanged, the downward component force of the gravity of the large arm is gradually increased along with the change of the angle of the large arm, and the amplitude falling speed is gradually increased. In order to ensure uniform amplitude falling, the opening degree of the amplitude-variable balance valve needs to be adjusted in real time along with the reduction of the amplitude-falling angle. The opening degree of the variable amplitude balance valve is determined by the opening degree of the electric control handle, namely the opening degree of the electric control handle needs to be adjusted in real time. However, in actual operation, it is difficult to realize uniform width falling through manual operation of the electric control handle, and the operation difficulty of uniform width falling is high.
Disclosure of Invention
The invention provides a self-weight amplitude-falling hydraulic control method and system and a crane, which are used for solving the problem that a crane self-weight amplitude-falling system in the prior art is difficult to realize uniform amplitude falling through manual operation of an electric control handle.
The invention provides a self-weight amplitude-falling hydraulic control method, which comprises the following steps:
acquiring the pressure of a rodless cavity of the luffing cylinder according to a preset time interval, and correcting the maximum control current in real time according to the pressure of the rodless cavity;
acquiring the opening of an electric control handle, and determining a control current according to the corrected maximum control current and the opening of the electric control handle;
and the amplitude-variable balance valve communicated with the rodless cavity adjusts the opening degree of a valve core of the amplitude-variable balance valve according to the control current.
According to the self-weight amplitude falling hydraulic control method provided by the invention, the maximum control current is corrected in real time according to the pressure of the rodless cavity, and a current compensation coefficient is determined according to the pressure of the rodless cavity and a preset maximum amplitude falling speed;
correcting the maximum control current in real time according to the current compensation coefficient, wherein the maximum control current corrected in real time is preferably as follows:
Figure BDA0002823953920000021
wherein,
Figure BDA0002823953920000022
the maximum control current of the electric control handle corrected at the ith moment,
Figure BDA0002823953920000023
is the original maximum control current, P, corresponding to the maximum opening of the electric control handleiPressure of said rodless chamber, K, obtained for moment iiAnd (3) determining a current compensation coefficient for the ith moment, wherein i is more than or equal to 1 and less than or equal to n, i is a positive integer, and acquiring the pressure of the rodless cavity for n times in the whole amplitude falling process.
According to the self-weight amplitude-falling hydraulic control method provided by the invention, the current compensation coefficient is determined according to the pressure of the rodless cavity and the preset maximum amplitude-falling speed, and the method specifically comprises the following steps:
respectively according to the pressure P of the rodless cavity obtained at the current momentiAnd the pressure P of the rodless chamber obtained at the previous momenti-1Determining the control current I required for maintaining the maximum amplitude falling speed at the current momentiAnd a control current I required for maintaining the maximum amplitude falling speed at the last momenti-1
The pressure P of the rodless cavity obtained according to the current momentiLast moment obtained pressure P of said rodless chamberi-1The control current I required for keeping the maximum amplitude falling speed at the current momentiAnd a control current I required for maintaining the maximum amplitude falling speed at the last momenti-1Determining the current compensation coefficient, preferably the current compensation coefficient is:
Figure BDA0002823953920000031
according to the self-weight amplitude-falling hydraulic control method provided by the invention, the pressure P of the rodless cavity is respectively obtained according to the current timeiAnd the said none obtained at the last momentPressure P of the rod cavityi-1Determining the control current I required for maintaining the maximum amplitude falling speed at the current momentiAnd a control current I required for maintaining the maximum amplitude falling speed at the last momenti-1The method specifically comprises the following steps:
determining the maximum flow demand of the rodless cavity according to the size of the amplitude-variable oil cylinder and the preset maximum amplitude-falling speed;
according to the flow formula
Figure BDA0002823953920000032
And determining the control current I required for keeping the maximum amplitude falling speed at the current moment according to the relation between the overcurrent area A of the amplitude variation balance valve and the control current IiAnd a control current I required for maintaining the maximum amplitude falling speed at the last momenti-1
Q is the flow of the rodless cavity, C is a flow coefficient, A is the flow area of the variable amplitude balance valve, rho is the density of hydraulic oil, and P is the pressure of the rodless cavity.
According to the self-weight amplitude-falling hydraulic control method provided by the invention, the maximum flow demand of the rodless cavity is determined according to the size of the amplitude-changing oil cylinder and the preset maximum amplitude-falling speed, and the method specifically comprises the following steps:
determining the cropping time according to the preset maximum cropping speed;
and determining the maximum flow demand of the rodless cavity according to the cylinder diameter of the luffing cylinder, the cylinder stroke and the luffing time.
The invention also provides a self-weight amplitude-falling hydraulic system, which comprises an amplitude-changing oil cylinder, an amplitude-changing balance valve, a pressure detection unit, an electric control handle and a controller;
the rod cavity of the variable-amplitude oil cylinder is communicated with an oil tank, the rodless cavity of the variable-amplitude oil cylinder is communicated with the working oil port of the variable-amplitude balance valve, the pressure detection unit is used for detecting the pressure of the rodless cavity of the variable-amplitude oil cylinder, and the variable-amplitude balance valve, the pressure detection unit and the electric control handle are respectively connected with the controller;
the controller is used for acquiring the pressure of the rodless cavity of the luffing cylinder at preset time intervals and correcting the maximum control current in real time according to the pressure of the rodless cavity; and the control circuit is also used for obtaining the opening of the electric control handle and determining the control current according to the corrected maximum control current and the opening of the electric control handle.
According to the self-weight amplitude-falling hydraulic system provided by the invention, the pressure detection unit is a pressure sensor.
The self-weight amplitude-falling hydraulic system further comprises an electric proportional pressure reducing valve, the electric proportional pressure reducing valve is in communication connection with the controller, and a working oil port of the electric proportional pressure reducing valve is communicated with a pilot oil port of the amplitude-changing balance valve.
The self-weight amplitude-falling hydraulic system further comprises an electro-hydraulic proportional reversing valve, a working oil port of the electro-hydraulic proportional reversing valve is communicated with an oil inlet of the amplitude-changing balance valve, and a pilot oil port of the electro-hydraulic proportional reversing valve is communicated with a pilot oil port of the amplitude-changing balance valve to form the same pilot oil.
The invention also provides a crane which comprises any one of the dead weight amplitude falling hydraulic systems.
According to the self-weight amplitude falling hydraulic control method, the system and the crane, the maximum control current is corrected in real time according to the real-time pressure of the rodless cavity, so that the control current corresponding to any opening of the electric control handle is corrected, and uniform amplitude falling is ensured without manually adjusting the opening of the electric control handle in real time. Any opening degree of the electric control handle corresponds to a constant amplitude falling speed, and during operation, the amplitude falling speed is determined and the electric control handle is adjusted to the corresponding opening degree. And the operation of uniform amplitude falling is greatly simplified under the condition of ensuring uniform amplitude falling.
Drawings
In order to more clearly illustrate the technical solutions of the present invention or the prior art, the drawings needed for the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.
FIG. 1 is a flow chart of a hydraulic control method for self-weight amplitude falling provided by the invention;
FIG. 2 is a schematic structural diagram of a self-weight amplitude-falling hydraulic system provided by the invention;
FIG. 3 is a block diagram of the self-weight drop hydraulic system provided by the present invention;
reference numerals:
1. a variable amplitude oil cylinder; 11. a rod cavity; 12. a rodless cavity; 2. a variable amplitude balance valve; 3. a pressure sensor; 4. an electric control handle; 5. a controller; 6. an oil tank; 7. an electro-hydraulic proportional directional valve; 8. an electro proportional pressure reducing valve.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The following describes the self-weight drop amplitude hydraulic control method, system and crane of the invention with reference to fig. 1-3.
The embodiment of the invention provides a self-weight amplitude falling hydraulic control method for realizing uniform amplitude falling control. Fig. 1 is a schematic flow chart of a hydraulic control method for self-weight amplitude falling provided by the present invention, and the hydraulic control method for self-weight amplitude falling comprises the following steps:
s100, acquiring the pressure of a rodless cavity of the luffing cylinder according to a preset time interval, and correcting the maximum control current in real time according to the pressure of the rodless cavity.
S200, acquiring the opening of an electric control handle, and determining a control current according to the corrected maximum control current and the opening of the electric control handle;
and S300, adjusting the opening degree of a valve core of the variable amplitude balance valve communicated with the rodless cavity according to the control current.
Specifically, a certain opening degree of the electric control handle corresponds to a certain control current and a certain opening degree of the variable amplitude balance valve. According to the embodiment of the invention, the maximum control current is corrected in real time according to the real-time pressure of the rodless cavity, so that the maximum control current changes along with the change of the pressure of the rodless cavity, namely, the maximum control current is corrected to gradually decrease along with the gradual increase of the pressure of the rodless cavity in the process of gradually increasing the pressure of the rodless cavity; because the maximum control current corresponds to the opening degree of the handle, the corrected maximum control current is multiplied by the opening degree value to obtain the control current corresponding to the opening degree value, and the control current corresponding to the opening degree value is reduced, so that the real-time correction of the control current corresponding to any opening degree value of the electric control handle is realized. And the amplitude-variable balance valve adjusts the opening of the valve core of the amplitude-variable balance valve according to the corrected control current so as to realize uniform amplitude drop. At the moment, different opening degrees of the electric control handle correspond to different amplitude falling speeds.
According to the self-weight amplitude falling hydraulic system provided by the embodiment of the invention, the maximum control current is corrected in real time according to the real-time pressure of the rodless cavity, so that the maximum control current is gradually reduced along with the increase of the pressure of the rodless cavity, and the control current corresponding to any opening of the electric control handle is also gradually reduced along with the increase of the pressure of the rodless cavity, so that any opening of the electric control handle corresponds to a constant amplitude falling speed, and the uniform amplitude falling is ensured without manually adjusting the opening of the electric control handle in real time. During operation, the required amplitude falling speed is determined and the electric control handle is adjusted to the corresponding opening. Under the condition of ensuring uniform amplitude falling, the operation of uniform amplitude falling is simplified to a great extent, and the operation difficulty is reduced.
In step S100, the correcting the maximum control current in real time according to the pressure of the rod-less cavity specifically includes:
s110, determining a current compensation coefficient according to the pressure of the rodless cavity and a preset maximum amplitude falling speed;
and S120, correcting the maximum control current in real time according to the current compensation coefficient.
In the self-weight amplitude-falling hydraulic system, under the action of the gravity of the large arm, the rodless cavity returns oil to the amplitude-changing balance valve, and the uniform amplitude-falling speed can be ensured due to the constant flow of the rodless cavity. The pressure in the rodless chamber gradually increases as the angle of the large arm decreases. According to the flow formula:
Figure BDA0002823953920000061
q is the flow of the rodless cavity, C is a flow coefficient, A is the flow area of the variable amplitude balance valve, rho is the density of hydraulic oil, and P is the pressure of the rodless cavity.
It can be known that, when the pressure of the rodless cavity is gradually increased, the opening degree of the variable amplitude balance valve needs to be reduced to ensure the constant flow of the rodless cavity, and then the control current needs to be reduced.
The preset maximum amplitude falling speed is a value manually set according to actual operation requirements, and corresponds to the control current corresponding to the maximum opening of the electric control handle. The embodiment of the invention aims to ensure that the maximum control current of the electric control handle at the maximum opening can always ensure the maximum amplitude falling speed to be constant, and the maximum control current is corrected in real time.
Specifically, the maximum control current corrected in real time is:
Figure BDA0002823953920000071
wherein,
Figure BDA0002823953920000072
is the maximum control current after the modification at the ith moment,
Figure BDA0002823953920000073
is the original maximum control current, P, corresponding to the maximum opening of the electric control handleiPressure of said rodless chamber, K, obtained for moment iiAnd (3) determining a current compensation coefficient for the ith moment, wherein i is more than or equal to 1 and less than or equal to n, i is a positive integer, and acquiring the pressure of the rodless cavity for n times in the whole amplitude falling process.
The pressure of a rodless cavity of the luffing oil cylinder can be acquired in real time through the pressure sensor, a real-time compensation coefficient is calculated according to the real-time pressure, then the maximum control current is corrected in real time through the correction formula on the basis of the original maximum control current corresponding to the maximum opening of the electric control handle according to the real-time pressure value and the real-time compensation coefficient of the rodless cavity, the maximum control current which is gradually reduced along with the gradual increase of the pressure of the rodless cavity is obtained, on the basis, the uniform amplitude of the rodless cavity at the set maximum amplitude falling speed can be guaranteed when the electric control handle is at the maximum opening, and similarly, the uniform amplitude of the rodless cavity at a certain speed which is less than the maximum amplitude falling speed can be guaranteed when the.
In step S110, the determining a current compensation coefficient according to the pressure of the rodless cavity and a preset maximum amplitude-falling speed specifically includes:
s111, respectively obtaining the pressure P of the rodless cavity at the current momentiAnd the pressure P of the rodless chamber obtained at the previous momenti-1Determining the control current I required for maintaining the maximum amplitude falling speed at the current momentiAnd a control current I required for maintaining the maximum amplitude falling speed at the last momenti-1
S112, obtaining the pressure P of the rodless cavity according to the current momentiLast moment obtained pressure P of said rodless chamberi-1The control current I required for keeping the maximum amplitude falling speed at the current momentiAnd a control current I required for maintaining the maximum amplitude falling speed at the last momenti-1Determining the current compensation factor.
After the pressure of the rodless cavity is collected at each moment, the control current required for keeping the maximum amplitude falling speed at the moment is calculated according to the pressure, and the pressure of the rodless cavity and the corresponding control current at each moment are stored for calling when the current compensation coefficient is calculated at the next moment.
Specifically, in the embodiment of the present invention, the current compensation coefficient is:
Figure BDA0002823953920000081
i before the rodless cavity pressure is collected at the first moment0And P0Respectively, the initialization of the systemThe current and the initial voltage of the rodless cavity are controlled. When the maximum control current is corrected at each moment, the pressure of the rodless cavity at the current moment is collected, the control current required for keeping the maximum amplitude falling speed at the current moment is calculated according to the pressure, the pressure of the rodless cavity at the previous moment and the corresponding control current are obtained at the same time, the current compensation coefficient at each moment is calculated according to the formula, and the corrected maximum control current at each moment can be obtained.
In step S111, the pressure P of the rodless chamber is obtained according to the current timeiAnd the pressure P of the rodless chamber obtained at the previous momenti-1Determining the control current I required for maintaining the maximum amplitude falling speed at the current momentiAnd a control current I required for maintaining the maximum amplitude falling speed at the last momenti-1The method specifically comprises the following steps:
determining the maximum flow demand of the rodless cavity according to the size of the amplitude-variable oil cylinder and the preset maximum amplitude-falling speed;
according to the flow formula
Figure BDA0002823953920000082
And determining the control current I required for keeping the maximum amplitude falling speed at the current moment according to the relation between the overcurrent area A of the amplitude variation balance valve and the control current IiAnd a control current I required for maintaining the maximum amplitude falling speed at the last momenti-1
Q is the flow of the rodless cavity, C is a flow coefficient, A is the flow area of the variable amplitude balance valve, rho is the density of hydraulic oil, and P is the pressure of the rodless cavity.
Specifically, the relationship between the flow area of the variable amplitude balance valve and the control current can be determined according to a valve core displacement-flow area curve of the variable amplitude balance valve and the relationship between the valve core displacement of the variable amplitude balance valve and the control current, namely, a is k · I, k is a flow area coefficient, and I is the control current. There is a definite relationship between the control current and the pressure in the rodless chamber with a constant flow in the rodless chamber.
The method comprises the following steps of determining the maximum flow demand of the rodless cavity according to the size of the luffing cylinder and the preset maximum amplitude falling speed, and specifically comprises the following steps:
determining the cropping time according to the preset maximum cropping speed;
and determining the maximum flow demand of the rodless cavity according to the cylinder diameter of the luffing cylinder, the cylinder stroke and the luffing time.
Specifically, the maximum amplitude falling speed corresponds to the maximum flow of the rodless cavity;
Figure BDA0002823953920000091
wherein Q ismThe maximum flow of the rodless cavity is shown, D is the cylinder diameter of the amplitude-variable oil cylinder, L is the stroke of the amplitude-variable oil cylinder, and T is the amplitude falling time.
The invention also provides a self-weight amplitude-dropping hydraulic system, which is shown in fig. 2 as a structural schematic diagram of the self-weight amplitude-dropping hydraulic system provided by the invention, and comprises an amplitude-dropping oil cylinder 1, an amplitude-dropping balance valve 2, a pressure detection unit, an electric control handle 4 and a controller 5. The rod cavity 11 of the variable amplitude oil cylinder 1 is communicated with the oil tank 6, and the rodless cavity 12 of the variable amplitude oil cylinder 1 is communicated with the working oil port of the variable amplitude balance valve 2. The pressure detection unit is used for detecting the pressure of the rodless cavity 12 of the luffing cylinder 1. The amplitude-variable balance valve 2, the pressure detection unit and the electric control handle 4 are respectively connected with a controller 5. The controller 5 is used for acquiring the pressure of the rodless cavity 12 of the luffing cylinder 1 according to a preset time interval and correcting the maximum control current in real time according to the pressure of the rodless cavity 12; and the control circuit is also used for obtaining the opening of the electric control handle and determining the control current according to the corrected maximum control current and the opening of the electric control handle.
Wherein the pressure detection unit may be a pressure sensor 3. The amplitude-variable balance valve 2 can be an electric proportional balance valve which is directly in communication connection with the controller 5, directly receives the control current output by the controller 5, and adjusts the opening of the valve core according to the control current. In the embodiment of the invention, the variable amplitude balance valve further comprises an electric proportional pressure reducing valve 8 serving as a pilot valve, the electric proportional pressure reducing valve 8 is in communication connection with the controller 5, a working oil port of the electric proportional pressure reducing valve 8 is communicated with a pilot oil port of the variable amplitude balance valve 2, the controller 5 transmits control current to the electric proportional pressure reducing valve 8, and the pilot oil is controlled by the electric proportional pressure reducing valve 8 to adjust the valve core opening of the variable amplitude balance valve 2.
As shown in fig. 2, a working oil port of the electro-hydraulic proportional reversing valve 7 is communicated with an oil inlet of the variable amplitude balance valve 2, a pilot oil port of the variable amplitude balance valve 2 is communicated with a pilot oil port of the electro-hydraulic proportional reversing valve 7, for example, a working oil port of the electro-proportional pressure reducing valve 8 is respectively communicated with the variable amplitude balance valve 2 and the pilot oil port of the electro-hydraulic proportional reversing valve 7. The oil drain ports of the variable amplitude oil cylinder 1, the variable amplitude balance valve 2 and the electro-hydraulic proportional reversing valve 7 are all communicated with an oil tank 6.
The dead weight hydraulic system that falls a width of cloth that this embodiment provided at during operation, operating personnel controls the aperture of automatically controlled handle 4. The controller 5 reads the pressure value of the rodless cavity 12 acquired by the pressure detection unit in real time, and corrects the maximum control current in real time according to the pressure value. Meanwhile, the controller 5 reads the opening value of the electric control handle 4, calculates a control current according to the opening value of the electric control handle 4 and the maximum control current of the electric control handle 4, and outputs the control current to the electro-proportional pressure reducing valve 8. The electric proportional pressure reducing valve 8 adjusts the opening degrees of the variable amplitude balance valve 2 and the electro-hydraulic proportional reversing valve 7 according to the control current, so that the crane boom falls at a constant speed in the vertical direction. The method for correcting the maximum control current by the controller 5 can be referred to the above embodiments, and is not described herein again.
The invention also provides a crane which comprises the self-weight amplitude-falling hydraulic system. The maximum control current can be corrected in real time, so that the control current corresponding to any opening of the electric control handle is corrected, and uniform amplitude falling is ensured without manually adjusting the opening of the electric control handle in real time. Any opening degree of the electric control handle corresponds to a constant amplitude falling speed, and during operation, the amplitude falling speed is determined and the electric control handle is adjusted to the corresponding opening degree. And the operation of uniform amplitude falling is simplified to a great extent under the condition of ensuring uniform amplitude falling.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims (10)

1. A self-weight amplitude-falling hydraulic control method is characterized by comprising the following steps:
acquiring the pressure of a rodless cavity of the luffing cylinder according to a preset time interval, and correcting the maximum control current in real time according to the pressure of the rodless cavity;
acquiring the opening of an electric control handle, and determining a control current according to the corrected maximum control current and the opening of the electric control handle;
and the amplitude-variable balance valve communicated with the rodless cavity adjusts the opening degree of a valve core of the amplitude-variable balance valve according to the control current.
2. The self-gravity amplitude-falling hydraulic control method according to claim 1, wherein the real-time correction of the maximum control current according to the pressure of the rodless cavity specifically comprises:
determining a current compensation coefficient according to the pressure of the rodless cavity and a preset maximum amplitude falling speed;
correcting the maximum control current in real time according to the current compensation coefficient, wherein the maximum control current corrected in real time is preferably as follows:
Figure FDA0002823953910000011
wherein,
Figure FDA0002823953910000012
the maximum control current of the electric control handle corrected at the ith moment,
Figure FDA0002823953910000013
is the original maximum control current, P, corresponding to the maximum opening of the electric control handleiPressure of said rodless chamber, K, obtained for moment iiAnd (3) determining a current compensation coefficient for the ith moment, wherein i is more than or equal to 1 and less than or equal to n, i is a positive integer, and acquiring the pressure of the rodless cavity for n times in the whole amplitude falling process.
3. The self-gravity amplitude-falling hydraulic control method according to claim 2, wherein the determining of the current compensation coefficient according to the pressure of the rodless chamber and a preset maximum amplitude-falling speed specifically comprises:
respectively according to the pressure P of the rodless cavity obtained at the current momentiAnd the pressure P of the rodless chamber obtained at the previous momenti-1Determining the control current I required for maintaining the maximum amplitude falling speed at the current momentiAnd a control current I required for maintaining the maximum amplitude falling speed at the last momenti-1
The pressure P of the rodless cavity obtained according to the current momentiLast moment obtained pressure P of said rodless chamberi-1The control current I required for keeping the maximum amplitude falling speed at the current momentiAnd a control current I required for maintaining the maximum amplitude falling speed at the last momenti-1Determining the current compensation coefficient, preferably the current compensation coefficient is:
Figure FDA0002823953910000021
4. the hydraulic control method for self-weight drop amplitude according to claim 3, wherein the pressure P of the rodless chamber obtained according to the current time is respectivelyiAnd the pressure P of the rodless chamber obtained at the previous momenti-1Determining the control current I required for maintaining the maximum amplitude falling speed at the current momentiAnd a control current I required for maintaining the maximum amplitude falling speed at the last momenti-1The method specifically comprises the following steps:
determining the maximum flow demand of the rodless cavity according to the size of the amplitude-variable oil cylinder and the preset maximum amplitude-falling speed;
according to the flow formula
Figure FDA0002823953910000022
And determining the control current I required for keeping the maximum amplitude falling speed at the current moment according to the relation between the overcurrent area A of the amplitude variation balance valve and the control current IiAnd a control current I required for maintaining the maximum amplitude falling speed at the last momenti-1
Q is the flow of the rodless cavity, C is a flow coefficient, A is the flow area of the variable amplitude balance valve, rho is the density of hydraulic oil, and P is the pressure of the rodless cavity.
5. The self-weight amplitude-falling hydraulic control method according to claim 4, wherein the determining of the maximum flow demand of the rodless chamber according to the size of the amplitude-falling cylinder and a preset maximum amplitude-falling speed specifically comprises:
determining the cropping time according to the preset maximum cropping speed;
and determining the maximum flow demand of the rodless cavity according to the cylinder diameter of the luffing cylinder, the cylinder stroke and the luffing time.
6. A self-weight amplitude-falling hydraulic system comprises an amplitude-changing oil cylinder and is characterized by further comprising an amplitude-changing balance valve, a pressure detection unit, an electric control handle and a controller;
the rod cavity of the variable-amplitude oil cylinder is communicated with an oil tank, the rodless cavity of the variable-amplitude oil cylinder is communicated with the working oil port of the variable-amplitude balance valve, the pressure detection unit is used for detecting the pressure of the rodless cavity of the variable-amplitude oil cylinder, and the variable-amplitude balance valve, the pressure detection unit and the electric control handle are respectively connected with the controller;
the controller is used for acquiring the pressure of the rodless cavity of the luffing cylinder at preset time intervals and correcting the maximum control current in real time according to the pressure of the rodless cavity; and the control circuit is also used for obtaining the opening of the electric control handle and determining the control current according to the corrected maximum control current and the opening of the electric control handle.
7. The self-gravity amplitude-falling hydraulic system according to claim 6, wherein the pressure detection unit is a pressure sensor.
8. The self-weight amplitude-falling hydraulic system as recited in claim 6, further comprising an electric proportional pressure reducing valve, wherein the electric proportional pressure reducing valve is in communication connection with the controller, and a working oil port of the electric proportional pressure reducing valve is communicated with a pilot oil port of the amplitude-falling balance valve.
9. The self-weight amplitude-falling hydraulic system as recited in claim 6, further comprising an electro-hydraulic proportional directional valve, wherein a working oil port of the electro-hydraulic proportional directional valve is communicated with an oil inlet of the amplitude-changing balance valve, and a pilot oil port of the electro-hydraulic proportional directional valve is communicated with a pilot oil port of the amplitude-changing balance valve to form the same pilot oil.
10. A crane comprising a self-gravity amplitude-falling hydraulic system as claimed in any one of claims 6 to 9.
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