CN113942963B - Load-sensitive forklift load port independent control system and method - Google Patents

Load-sensitive forklift load port independent control system and method Download PDF

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Publication number
CN113942963B
CN113942963B CN202111129740.1A CN202111129740A CN113942963B CN 113942963 B CN113942963 B CN 113942963B CN 202111129740 A CN202111129740 A CN 202111129740A CN 113942963 B CN113942963 B CN 113942963B
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control
hydraulic cylinder
valve
pressure
valve group
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CN113942963A (en
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童水光
吴双双
童哲铭
李元松
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Zhejiang University ZJU
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Zhejiang University ZJU
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66F—HOISTING, LIFTING, HAULING OR PUSHING, NOT OTHERWISE PROVIDED FOR, e.g. DEVICES WHICH APPLY A LIFTING OR PUSHING FORCE DIRECTLY TO THE SURFACE OF A LOAD
    • B66F9/00—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes
    • B66F9/06—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes movable, with their loads, on wheels or the like, e.g. fork-lift trucks
    • B66F9/075—Constructional features or details
    • B66F9/20—Means for actuating or controlling masts, platforms, or forks
    • B66F9/22—Hydraulic devices or systems
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66F—HOISTING, LIFTING, HAULING OR PUSHING, NOT OTHERWISE PROVIDED FOR, e.g. DEVICES WHICH APPLY A LIFTING OR PUSHING FORCE DIRECTLY TO THE SURFACE OF A LOAD
    • B66F9/00—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes
    • B66F9/06—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes movable, with their loads, on wheels or the like, e.g. fork-lift trucks
    • B66F9/075—Constructional features or details
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66F—HOISTING, LIFTING, HAULING OR PUSHING, NOT OTHERWISE PROVIDED FOR, e.g. DEVICES WHICH APPLY A LIFTING OR PUSHING FORCE DIRECTLY TO THE SURFACE OF A LOAD
    • B66F9/00—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes
    • B66F9/06—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes movable, with their loads, on wheels or the like, e.g. fork-lift trucks
    • B66F9/075—Constructional features or details
    • B66F9/0755—Position control; Position detectors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/16—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B13/00—Details of servomotor systems ; Valves for servomotor systems
    • F15B13/02—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors
    • F15B13/06—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with two or more servomotors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B19/00—Testing; Calibrating; Fault detection or monitoring; Simulation or modelling of fluid-pressure systems or apparatus not otherwise provided for
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B21/00—Common features of fluid actuator systems; Fluid-pressure actuator systems or details thereof, not covered by any other group of this subclass
    • F15B21/08—Servomotor systems incorporating electrically operated control means
    • F15B21/087—Control strategy, e.g. with block diagram

Abstract

The invention provides a forklift load port independent control system and method with sensitive load to solve the problem that the prior art can not meet the requirements of forklift control performance and energy-saving performance at the same time, so that the working reliability of a forklift under any working condition is guaranteed, and the energy-saving characteristic and the control characteristic of a forklift hydraulic system are improved. In order to realize the purpose, the following technical scheme is adopted: the hydraulic control system comprises a portal lifting hydraulic cylinder, an operating rod, a portal tilting hydraulic cylinder, a load sensitive pump, a regulator, an ECU controller, a fork side shifting hydraulic cylinder, a lifting valve group, a tilting valve group and a side shifting valve group, wherein the lifting valve group, the tilting valve group and the side shifting valve group are respectively configured to be used for controlling the flow, the pressure and the flow speed of hydraulic oil in a rodless cavity and a rod cavity of the portal lifting hydraulic cylinder, the portal tilting hydraulic cylinder and the fork side shifting hydraulic cylinder; a step-back adaptive robust control algorithm is adopted to solve the problem of low control precision caused by nonlinearity and uncertainty of a hydraulic system; and the combined pump valve compositely controls each hydraulic cylinder to meet the flow demand under any working condition.

Description

Load-sensitive forklift load port independent control system and method
Technical Field
The invention relates to the field of transport vehicle control, in particular to a load-sensitive forklift load port independent control system and method.
Background
Fork truck plays an important role in modern commodity circulation and storage and distribution, and hydraulic system is as the actuating system that fork truck function realized, and its performance is good and bad to fork truck's working property decisively influence.
The hydraulic system of the forklift mainly comprises subsystems such as gantry lifting, gantry inclining and pallet fork side moving, and the designated action is realized by controlling the extension and retraction of hydraulic cylinders (namely hydraulic cylinders) of the subsystems. At present, a forklift hydraulic system mostly adopts a load sensitive control system with a single pump for supplying oil and a plurality of hydraulic cylinders working simultaneously, namely, the flow of the pump is adaptively adjusted by monitoring the pressure and the flow according to the pressure margin between the outlet pressure of the pump and the load pressure so as to reduce the throttling loss of a bypass. However, under the condition of large difference of load inertia, the flow saturation phenomenon is easy to occur, namely the sum of the flow required by each hydraulic cylinder is larger than the maximum output flow of the pump, so that the flow is preferentially supplied to the hydraulic cylinder with a small load, and the hydraulic cylinder with a large load decelerates or even stops working due to insufficient flow supply. In addition, when the working condition changes, the load sensitive systems at different working points under a single control strategy cannot simultaneously meet the requirements of control performance and energy-saving performance. Therefore, it is particularly important to design a forklift hydraulic system and a control method which can meet the working requirements of each hydraulic cylinder under any working condition and improve the energy-saving characteristic and the control performance at the same time.
Modern forklifts mostly adopt a load-sensitive control system with a single pump for supplying oil and multiple hydraulic cylinders working simultaneously, and under the condition of large load inertia difference, the flow and pressure matching of the load-sensitive systems at different working points under a single control strategy can not meet the requirements of control performance and energy-saving performance simultaneously.
The forklift has complex and variable working conditions, the flow saturation phenomenon easily occurs under the condition that the load inertia difference is large, namely the sum of the flow required by each hydraulic cylinder is larger than the maximum output flow of the pump, so that the flow is preferentially supplied to the hydraulic cylinder with a small load, and the large-load hydraulic cylinder decelerates or even stops working due to insufficient flow supply.
The control method comprises the following steps of load sensitive multi-way valve core coupling linkage, hydraulic system nonlinearity problem, hydraulic oil characteristic dynamic change and hydraulic cylinder control accuracy reduction caused by load external interference.
The prior art of the prior art for a forklift hydraulic load sensitive control system is as follows: (1) Taking the chinese patent 201410365226.1 as an example, the multi-way valve structure is optimized to improve the working stability of the load sensitive system and reduce the energy loss, but the multi-way valve has a mechanical linkage phenomenon, only one oil port of the oil inlet and the oil outlet can be controlled, and the control precision and the energy utilization rate also improve the space. (2) Taking Zhao Junwei as an example, the research on the split-flow control of the multi-hydraulic-cylinder load-sensitive system improves the working reliability of each hydraulic cylinder of the load-sensitive system by researching the flow distribution algorithm of each hydraulic cylinder, but the adopted control algorithm is greatly influenced by the nonlinearity of the system, and the design of the control algorithm can be further optimized.
Disclosure of Invention
The invention provides a forklift load port independent control system and method with sensitive load to solve the problem that the prior art cannot meet the requirements of forklift control performance and energy-saving performance at the same time, so as to guarantee the working reliability of a forklift under any working condition and improve the energy-saving characteristic and the control characteristic of a forklift hydraulic system.
In order to achieve the purpose, the invention adopts the following technical scheme:
a load-sensitive forklift load port independent control system is characterized by comprising a gantry lifting hydraulic cylinder, an operating lever, a gantry tilting hydraulic cylinder, a load-sensitive pump, a regulator, an ECU controller and a pallet fork side shifting hydraulic cylinder;
the lifting valve group is configured to be used for controlling the flow, pressure and flow speed of hydraulic oil in a rodless cavity and a rod cavity of the gantry lifting hydraulic cylinder;
the tilting valve group is configured to be used for controlling the flow, pressure and flow rate of hydraulic oil in a rodless cavity and a rod cavity of the gantry tilting hydraulic cylinder;
the hydraulic control system further comprises a side shift valve group which is configured to be used for controlling the flow, pressure and flow rate of hydraulic oil in a rodless cavity and a rod cavity of the fork side shift hydraulic cylinder;
the control rod is connected with the ECU controller, the gantry lifting hydraulic cylinder is connected with the lifting valve group, the gantry tilting hydraulic cylinder is connected with the tilting valve group, the fork side shifting hydraulic cylinder is connected with the side shifting valve group, the lifting valve group, the tilting valve group and the side shifting valve group are connected in parallel to the load sensitive pump, the load sensitive pump is connected with the regulator, and the regulator is connected with the ECU controller.
Furthermore, the lifting valve group, the inclined valve group and the side shifting valve group all use three-position three-way electro-hydraulic proportional valves; a valve core position sensor is arranged on the valve body; all the three-position three-way electro-hydraulic proportional valves are independent of each other, the controller outputs electric signals to directly control the opening and the direction of a valve port according to the requirements of the system, and the gantry lifting hydraulic cylinder, the gantry tilting hydraulic cylinder and the pallet fork side shifting hydraulic cylinder are provided with displacement sensors and are configured to be used for detecting the position of a piston rod and transmitting position information back to the ECU controller.
Furthermore, the lifting valve group comprises a mast lifting hydraulic cylinder rodless cavity control valve and a mast lifting hydraulic cylinder rod cavity control valve which are respectively connected with a rodless cavity and a rod cavity of a mast lifting hydraulic cylinder, the tilting valve group comprises a mast tilting hydraulic cylinder rodless cavity control valve and a mast tilting hydraulic cylinder rod cavity control valve which are respectively connected with a rodless cavity and a rod cavity of a mast tilting hydraulic cylinder, and the side shifting valve group comprises a fork side shifting hydraulic cylinder rodless cavity control valve and a fork side shifting hydraulic cylinder rod cavity control valve which are respectively connected with a rodless cavity and a rod cavity of a fork side shifting hydraulic cylinder.
The forklift truck further comprises a plurality of pressure sensors which are respectively a first pressure sensor, a second pressure sensor, a third pressure sensor, a fourth pressure sensor, a fifth pressure sensor, a sixth pressure sensor and a pump outlet pressure sensor, wherein a rod cavity and a rodless cavity of the gantry lifting hydraulic cylinder are respectively connected with the ECU controller through the first pressure sensor and the second pressure sensor, a rodless cavity and a rod cavity of the gantry tilting hydraulic cylinder are respectively connected with the ECU controller through the third pressure sensor and the fourth pressure sensor, a rodless cavity and a rod cavity of the fork side-shifting hydraulic cylinder are respectively connected with the ECU controller through the fifth pressure sensor and the sixth pressure sensor, the lifting valve group, the tilting valve group and the pump outlet pressure sensor are connected in parallel, the pump outlet pressure sensor is connected with the ECU controller, and the pump outlet pressure sensor and the load-sensitive pump are in parallel relation.
The independent control method for the load port of the forklift with the load sensitivity by using the system is characterized by comprising the following steps of:
step 1: an ideal position control command is input, the ECU controller judges the load direction and the motion direction of each hydraulic cylinder, and ideal driving force F is calculated di I =1,2,3,1 represents a lifting valve group, 2 represents an inclined valve group and 3 represents a side shifting valve group, and the optimal working mode of each hydraulic cylinder is judged according to the values; the optimal working mode comprises the following steps: f di When the direction is consistent with the extending direction of the piston rod of the hydraulic cylinder, the speed control is carried out in the rodless cavity, and the pressure is carried out in the rod cavityForce control to maintain a lower pressure value; f di When the direction is opposite to the extending direction of the piston rod of the hydraulic cylinder, the rodless cavity is used for pressure control to keep a lower pressure value, and the rod cavity is used for speed control; f di When the value is zero, closing the valve group;
step 2: the pressure and position sensors of the respective hydraulic cylinders output data to the ECU controller in accordance with the desired driving force F di Respectively determining a control law of rodless cavity speed control, a control law of rod cavity speed control and ideal speed control flow, a control law of rodless cavity pressure control, a control law of rod cavity pressure control and ideal pressure control flow by adopting a backstepping self-adaptive robust position tracking control algorithm, and outputting the ideal control flow of each hydraulic cylinder according to the optimal working mode of each hydraulic cylinder in the step 1, wherein the ideal control flow comprises ideal speed control flow and ideal pressure control flow;
and step 3: based on the ideal control flow of the two cavities of each hydraulic cylinder output in the step 2, outputting a control signal u p The displacement of the load sensitive pump is adjusted to realize the main control of the flow; control signals of the lifting valve group, the inclined valve group and the side shifting valve group are output, the opening of the valve port of each valve group is adjusted, and the accurate control of the flow of the two cavities of each hydraulic cylinder is realized;
and 4, step 4: judging whether the actual flow meets the requirement, and finishing the control if the actual flow meets the requirement; and otherwise, feeding back the values of the pressure sensor and the displacement sensor by each hydraulic cylinder, and repeating the step 2 and the step 3 until the matching of the flow of each hydraulic cylinder and the ideal control flow is realized, and simultaneously, ensuring that the difference value of the system pressure and the load pressure is maintained at a set value, and realizing the function of electro-hydraulic load sensitivity.
Further, the specific method for judging whether the actual flow meets the requirement in the step 4 is to calculate the actual flow of each hydraulic cylinder in real time through a calibrated pressure-flow characteristic curve of the proportional valve according to the pressure difference between two ends of the valve port and the voltage of each electro-hydraulic proportional valve, and meet the control requirement if the absolute value of the difference between the actual flow and the ideal control flow is smaller than a preset error value.
Therefore, the invention has the following beneficial effects: (1) The two three-position three-way electro-hydraulic proportional valves are adopted to replace a multi-way valve in a traditional system, so that the system structure is simplified, the use cost of the valve piece is reduced, the degree of freedom of control of the hydraulic cylinder is increased, a better hardware basis is provided for a control strategy which is more in line with the actual working condition, and the control performance is improved; (2) The independent control technology for the load port of the forklift with the load sensitivity reduces energy loss caused by overlarge pressure difference of the valve port at the end of the low-pressure hydraulic cylinder in the traditional multi-hydraulic-cylinder load sensitivity system, and improves the energy utilization rate; (3) The problem of low control precision caused by nonlinearity and uncertainty of a hydraulic system can be effectively solved by adopting a back-stepping self-adaptive robust control algorithm; the flow and the pressure of two chambers of each hydraulic cylinder are accurately controlled by combining the compound control of the pump valve, and the flow requirements of each hydraulic cylinder under any working conditions are met.
Drawings
FIG. 1 is a control system connection diagram of the present invention.
Fig. 2 is a control method program diagram of the present invention.
In the figure: 1. a gantry lifting hydraulic cylinder, 2, an operating rod, 3, a gantry tilting hydraulic cylinder, 4, a pump outlet pressure sensor, 5, a load sensitive pump, 6, a regulator, 7, an ECU controller, 8 and a fork side shifting hydraulic cylinder,
1.1, a mast lifting hydraulic cylinder rodless cavity control valve, 1.2, a mast lifting hydraulic cylinder rodless cavity control valve, 3.1, a mast tilting hydraulic cylinder rodless cavity control valve, 8.1, a fork side shifting hydraulic cylinder rodless cavity control valve, 4.1, a first pressure sensor, 4.2, a second pressure sensor, 4.3, a third pressure sensor, 4.4, a fourth pressure sensor, 4.5, a fifth pressure sensor, 4.6 and a sixth pressure sensor.
Detailed Description
The invention is further described with reference to the following figures and embodiments.
In the embodiment shown in figures 1 and 2,
a load-sensitive forklift load port independent control system comprises a gantry lifting hydraulic cylinder 1, an operating rod 2, a gantry tilting hydraulic cylinder 3, a load-sensitive pump 5, a regulator 6 and an ECU (electronic control Unit) control systemThe hydraulic lifting device comprises a device 7, a fork side-shifting hydraulic cylinder 8, a lifting valve group, an inclination valve group and a side-shifting valve group, wherein the lifting valve group, the inclination valve group and the side-shifting valve group are respectively configured to be used for controlling the flow, the pressure and the flow speed of hydraulic oil in a rodless cavity and a rod cavity of the portal lifting hydraulic cylinder 1, the portal inclination hydraulic cylinder 3 and the fork side-shifting hydraulic cylinder 8; the mast lift cylinder 1, mast tilt cylinder 3 and fork side shift cylinder 8 are provided with displacement sensors and are configured to detect the piston rod position x 1 、x 2 、x 3 And transmits the position information back to the ECU controller 7. The control rod is connected with the ECU controller 7, the gantry lifting hydraulic cylinder 1 is connected with the lifting valve group, the gantry tilting hydraulic cylinder 3 is connected with the tilting valve group, the fork side shifting hydraulic cylinder 8 is connected with the side shifting valve group, the lifting valve group, the tilting valve group and the side shifting valve group are connected in parallel to the load sensitive pump 5, the load sensitive pump 5 is connected with the regulator 6, and the regulator 6 is connected with the ECU controller 7.
The lifting valve group, the inclined valve group and the side shifting valve group all use three-position three-way electro-hydraulic proportional valves; a valve core position sensor is arranged on the valve body; all the three-position three-way electro-hydraulic proportional valves are independent of each other, and the opening and the direction of a valve port are directly controlled by an electric signal output by a controller according to the requirements of a system. The lifting valve group comprises a mast lifting hydraulic cylinder rodless cavity control valve 1.1 and a mast lifting hydraulic cylinder rodless cavity control valve 1.2 which are respectively connected with a rodless cavity and a rod cavity of a mast lifting hydraulic cylinder 1, the tilting valve group comprises a mast tilting hydraulic cylinder rodless cavity control valve 3.1 and a mast tilting hydraulic cylinder rod cavity control valve 3.2 which are respectively connected with a rodless cavity and a rod cavity of a mast tilting hydraulic cylinder 3, and the side shifting valve group comprises a fork side shifting hydraulic cylinder rodless cavity control valve 8.1 and a fork side shifting hydraulic cylinder rod cavity control valve 8.2 which are respectively connected with a rodless cavity and a rod cavity of a fork side shifting hydraulic cylinder 8.
The forklift load port independent control system sensitive to loads further comprises a plurality of pressure sensors which are respectively a first pressure sensor 4.1, a second pressure sensor 4.2, a third pressure sensor 4.3, a fourth pressure sensor 4.4, a fifth pressure sensor 4.5, a sixth pressure sensor 4.6 and a pump outlet pressure sensor 4, wherein a rod cavity and a rodless cavity of the gantry lifting hydraulic cylinder 1 are respectively connected with the ECU controller 7 through the first pressure sensor 4.1 and the second pressure sensor 4.2, a rodless cavity and a rod cavity of the gantry tilting hydraulic cylinder 3 are respectively connected with the pump outlet 7 through the third pressure sensor 4.3 and the fourth pressure sensor 4.4, a rodless cavity and a rod cavity of the fork side-moving hydraulic cylinder 8 are respectively connected with the ECU controller 7 through the fifth pressure sensor 4.5 and the sixth pressure sensor 4.6, the lifting valve group, the tilting valve group, the side-moving valve group is connected with the pressure sensors 4 in parallel, the pressure sensors 4 are connected with the ECU controller 7, and the pressure sensors 4 and the load pump outlet 7 are in parallel relation.
The basic operation process of the system is as follows: the control lever 2 is manually operated and then outputs a control signal to the ECU controller 7 through the CAN bus; the pressure sensors monitor the pressure of two cavities, namely a rod cavity and a rodless cavity, of each hydraulic cylinder, and the valve core position sensor monitors the position of the valve core and transmits the position back to the ECU controller 7 through a CAN bus; the pressure sensors detect the pressure at the outlet of the load-sensitive pump 5 and transmit the pressure to the ECU controller 7 through a CAN bus; the ECU controller 7 outputs a control instruction according to a control algorithm, the regulator 6 receives the control instruction to regulate the pressure and the flow of the load sensitive pump 5, and each valve group receives the control instruction to regulate the opening and the direction of a valve port.
A load-sensitive forklift load port independent control method uses the system and comprises the following steps:
step 1: an ideal position control command is input, the ECU controller judges the load direction and the motion direction of each hydraulic cylinder, and ideal driving force F is calculated di I =1,2,3,1 represents a lifting valve group, 2 represents an inclined valve group and 3 represents a side shifting valve group, and the optimal working mode of each hydraulic cylinder is judged according to the values; the optimal working mode comprises the following steps: f di When the direction is consistent with the extending direction of the piston rod of the hydraulic cylinder, the rodless cavity is used for speed control, and the rod cavity is used for pressure control so as to keep a lower pressure value; f di When the direction is opposite to the extending direction of the piston rod of the hydraulic cylinder, the rodless cavity is used for pressure control to keep a lower pressure value, and the rod cavity is used for speed control; f di When the value is zero, closing the valve group;
step 2: the pressure and position sensors of each hydraulic cylinder output data to the ECU controller,according to the ideal driving force F di Respectively determining control law L of rodless cavity speed control by adopting backstepping self-adaptive robust position tracking control algorithm s，i1 And its ideal control flow rate Q sd,i1 (ii) a Control law L for speed control of rod cavity s，i2 And its ideal control flow Q sd,i2 And control law L of rodless cavity pressure control p，i1 And its ideal control flow Q pd,i1 Control law L for pressure control of rod cavity p，i2 And ideal control flow Q pd,i2 And simultaneously outputting the ideal control flow Q of each hydraulic cylinder according to the optimal working mode of each hydraulic cylinder in the step 1 d,ij Including speed control of desired flow rate Q sd，ij Sum pressure control of desired flow rate Q pd.ij ；
And 3, step 3: based on the ideal control flow of the two cavities of each hydraulic cylinder output in the step 2, outputting a control signal u p The displacement of the load sensitive pump is adjusted to realize the main control of the flow; control signals of the lifting valve group, the inclined valve group and the side shifting valve group are output, the opening degree of a valve port of each valve group is adjusted, and accurate control of flow of two cavities of each hydraulic cylinder is achieved;
and 4, step 4: judging whether the actual flow meets the requirement, and finishing the control if the actual flow meets the requirement; and otherwise, feeding back the values of the pressure sensor and the displacement sensor by each hydraulic cylinder, and repeating the step 2 and the step 3 until the matching of the flow of each hydraulic cylinder and the ideal control flow is realized, and simultaneously, ensuring that the difference value of the system pressure and the load pressure is maintained at a set value, and realizing the function of electro-hydraulic load sensitivity.
The specific method for judging whether the actual flow meets the requirement in the step 4 is to calculate the actual flow Q of each hydraulic cylinder in real time through a calibrated pressure-flow characteristic curve of the proportional valve according to the pressure difference between two ends of the valve port and the voltage of each electro-hydraulic proportional valve r,ij If | Q r,ij -Q d,ij |. Ltoreq.Z, Z is a preset error value, and the control requirement is met.
The above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and these modifications or substitutions do not depart from the spirit of the corresponding technical solutions of the embodiments of the present invention.

Claims (4)

1. A method for independently controlling a load port of a forklift with sensitive load is characterized in that,
the method adopts a load-sensitive independent control system of a forklift load port, wherein the control system comprises a gantry lifting hydraulic cylinder, an operating rod, a gantry tilting hydraulic cylinder, a load-sensitive pump, a regulator, an ECU controller and a pallet fork side shifting hydraulic cylinder; the lifting valve group is configured to be used for controlling the flow, pressure and flow rate of hydraulic oil in a rodless cavity and a rod cavity of the gantry lifting hydraulic cylinder; the tilting valve group is configured to be used for controlling the flow, pressure and flow rate of hydraulic oil in a rodless cavity and a rod cavity of the gantry tilting hydraulic cylinder; the hydraulic control system further comprises a side shift valve group which is configured to be used for controlling the flow, pressure and flow rate of hydraulic oil in a rodless cavity and a rod cavity of the fork side shift hydraulic cylinder; the fork side-shifting hydraulic cylinder is connected with the side-shifting valve group, the lifting valve group, the tilting valve group and the side-shifting valve group are connected in parallel to a load sensitive pump, the load sensitive pump is connected with an adjuster, and the adjuster is connected with the ECU controller;
the method comprises the following steps:
step 1: an ideal position control command is input, the ECU controller judges the load direction and the motion direction of each hydraulic cylinder, and ideal driving force F is calculated di I =1,2,3,1 represents a lifting valve group, 2 represents an inclined valve group and 3 represents a side shifting valve group, and the optimal working mode of each hydraulic cylinder is judged according to the values; the optimal working mode comprises the following steps: f di When the direction is consistent with the extending direction of the piston rod of the hydraulic cylinder, the rodless cavity is used for speed control, and the rod cavity is used for pressure control so as to keep a lower pressure value; f di When the direction is opposite to the extending direction of the piston rod of the hydraulic cylinder, the rodless cavity is used for pressure control to keep a lower pressure value, and the rod cavity is used for speed control; f di When the value is zero, closing the valve group;
and 2, step: the pressure and position sensors of the respective hydraulic cylinders output data to the ECU controller in accordance with the desired driving force F di Respectively determining control law L of rodless cavity speed control by adopting backstepping self-adaptive robust position tracking control algorithm s,i1 And its ideal control flow rate Q sd,i1 (ii) a Control law L for speed control of rod cavity s,i2 And its ideal control flow Q sd,i2 And control law L for rodless cavity pressure control p,i1 And its ideal control flow rate Q pd,i1 Control law L for pressure control of rod cavity p,i2 And ideal control flow Q pd,i2 And simultaneously outputting the ideal control flow Q of each hydraulic cylinder according to the optimal working mode of each hydraulic cylinder in the step 1 d,ij Including speed control of desired flow rate Q sd,ij Sum pressure control of desired flow rate Q pd.ij ；
And step 3: based on the ideal control flow of the two cavities of each hydraulic cylinder output in the step 2, outputting a control signal up to adjust the discharge capacity of the load sensitive pump, and realizing the main control of the flow; control signals of the lifting valve group, the inclined valve group and the side shifting valve group are output, the opening of the valve port of each valve group is adjusted, and the accurate control of the flow of the two cavities of each hydraulic cylinder is realized;
and 4, step 4: judging whether the actual flow meets the requirement, and finishing control if the actual flow meets the requirement; otherwise, feeding back the values of the pressure sensor and the displacement sensor by each hydraulic cylinder, and repeating the step 2 and the step 3 until the flow of each hydraulic cylinder is matched with the ideal control flow, and simultaneously ensuring that the difference value of the system pressure and the load pressure is maintained at a set value to realize the function of electro-hydraulic load sensitivity;
the specific method for judging whether the actual flow meets the requirement in the step 4 is to calculate the actual flow Q of each hydraulic cylinder in real time through a calibrated pressure-flow characteristic curve of the proportional valve according to the pressure difference between two ends of the valve port and the voltage of each electro-hydraulic proportional valve r,ij If | Q r,ij -Q d,ij And | is less than or equal to Z, and Z is a preset error value, the control requirement is met.
2. The method as claimed in claim 1, wherein the lift valve set, the tilt valve set and the side shift valve set all use three-position three-way electro-hydraulic proportional valves; a valve core position sensor is arranged on the valve body; all the three-position three-way electro-hydraulic proportional valves are independent of each other, the controller outputs electric signals to directly control the opening and the direction of a valve port according to the requirements of the system, and the portal lifting hydraulic cylinder, the portal tilting hydraulic cylinder and the fork side shifting hydraulic cylinder are provided with displacement sensors and are configured to be used for detecting the position of a piston rod and transmitting position information back to the ECU controller.
3. The method of claim 1, wherein the set of lift valves includes a mast lift cylinder rodless chamber control valve and a mast lift cylinder rodless chamber control valve connected to the rodless chamber and the rodless chamber of the mast lift cylinder, respectively, the tilt valve set includes a mast tilt cylinder rodless chamber control valve and a mast tilt cylinder rodless chamber control valve connected to the rodless chamber and the rodless chamber of the mast tilt cylinder, respectively, and the side shift valve set includes a fork side shift cylinder rodless chamber control valve and a fork side shift cylinder rodless chamber control valve connected to the rodless chamber and the rodless chamber of the fork side shift cylinder, respectively.
4. The method as claimed in claim 1, further comprising a plurality of pressure sensors respectively including a first pressure sensor, a second pressure sensor, a third pressure sensor, a fourth pressure sensor, a fifth pressure sensor, a sixth pressure sensor and a pump outlet pressure sensor, wherein the rod chamber and the rod-less chamber of the mast elevating hydraulic cylinder are connected to the ECU controller through the first pressure sensor and the second pressure sensor, the rod-less chamber and the rod chamber of the mast tilting hydraulic cylinder are connected to the ECU controller through the third pressure sensor and the fourth pressure sensor, respectively, the rod-less chamber and the rod chamber of the fork side-shifting hydraulic cylinder are connected to the ECU controller through the fifth pressure sensor and the sixth pressure sensor, respectively, wherein the elevating valve set, the tilting valve set, and the pump outlet valve set are connected in parallel to the pump outlet pressure sensor, the pressure sensors are connected to the ECU controller, and the pump outlet pressure sensors are connected to the load sensing pump in parallel.
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