Large size extension mechanism and control system based on multi-cylinder driving

Abstract

The application belongs to the field of stretching mechanism deployment control, and particularly relates to a large-size stretching mechanism based on multiple hydraulic cylinder driving and a control system. The stretching mechanism comprises a framework, a scissor system and a mounting part. Multiple parallel frameworks are connected with the scissor system and can be deployed and retracted under the action of the scissor system. Multiple mounting parts are arranged on each framework. The scissor system comprises a sliding rod, a sliding block, a scissor mechanism and a hydraulic cylinder. The scissor mechanism comprises multiple series-connected secondary scissor units. Each secondary scissor unit comprises four racks with the same length. One end of the hydraulic cylinder is connected with one of the first rack and the second rack, and the other end of the hydraulic cylinder is connected with one of the third rack and the fourth rack. Multiple secondary scissor units are connected in series to realize the multiple-cylinder driving of the stretching mechanism and the erection of the large expansion ratio, and face the deployment demand of large-area laying.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of deployment control of deployment mechanism, and relates to a multi-hydraulic-cylinder position layout optimization method and a deployment mechanism control system design, in particular to a large-size deployment mechanism driven by multiple hydraulic cylinders and a control system. BACKGROUND

[0002] A deployment mechanism is a kind of kinematic structure with structural morphological change characteristics. In its working state, its morphology can be divided into the following three categories: folding state, stretching and folding motion state, and unfolded holding state. The deployment mechanism usually has the characteristics of unitization, and its constituent units have various types, such as scissor units, parallel four-edge units, and polyhedral units, etc. When the deployment mechanism is applied to the field of large-size deployment or large load conditions, hydraulic transmission is generally used to realize the driving deployment of the deployment mechanism, which can output large thrust or torque. At present, most of the deployment mechanisms (such as telescopic jibs, lifting machines, and truck cranes) in China adopt a single hydraulic cylinder driving scheme. However, the output power of the single-drive deployment mechanism cannot meet the working requirements of large-size mechanism deployment, and the structure size of the single hydraulic cylinder is large, which is not conducive to the overall mechanism layout. The emergence of the multi-hydraulic-cylinder synchronous driving system solves the problem of insufficient output power. However, once the multi-hydraulic-cylinder synchronous driving system is out of synchronization, it will cause the deployment mechanism to be blocked, and even the mechanical structure may be damaged due to jamming during expansion. In addition, due to the large expansion ratio of the mechanism, the influence of the gravity of the mechanism itself is amplified, the travel trajectories of the multiple cylinders are different, and thus the multiple cylinders are blocked when driving each other. Therefore, the design of a large-size deployment mechanism driven by multiple hydraulic cylinders and the coordinated synchronous deployment control method can not only improve the driving capacity, but also improve the service life, and has important safety significance. SUMMARY

[0003] The present application aims to provide a scissor-type deployment mechanism driven by multiple cylinders based on optimized layout, and a coordinated control deployment method considering the influence of the gravity of the structure itself and the deformation of the hanging load, so as to achieve the coordinated driving effect of the large-size scissor-type deployment mechanism. Specifically, the present application provides a large-size deployment mechanism driven by multiple cylinders, which comprises multiple parallel skeletons, a scissor system, and a hanging load, wherein the multiple parallel skeletons are connected with the scissor system and can be unfolded and retracted under the action of the scissor system, and multiple hanging loads are arranged on each skeleton.

[0004] The scissor lift system includes a slide bar, a slider, a scissor lift mechanism, and a hydraulic cylinder. The scissor lift mechanism comprises multiple series-connected secondary scissor lift units. Each secondary scissor lift unit includes four forks of equal length: a first fork, a second fork, a third fork, and a fourth fork. The first and second forks are intersected and hinged at the intersection to form a first hinge point; the third and fourth forks are intersected and hinged at the intersection to form a second hinge point. The second end of the first fork is hinged to the first end of the fourth fork; the second end of the second fork is hinged to the first end of the third fork; the second end of the fourth fork is hinged to the first end of the first fork of an adjacent secondary scissor lift unit; and the second end of the third fork is hinged to the first end of the second fork of an adjacent secondary scissor lift unit.

[0005] In this configuration, the first end of the first fork of the first secondary scissor lift unit is hinged to the slide bar, and the first end of the second fork of the first secondary scissor lift unit is hinged to the slider; the slider can slide on the slide bar; each frame is connected to the second hinge point of the corresponding secondary scissor lift unit and can move with the displacement of the second hinge point; each secondary scissor lift unit is provided with a hydraulic cylinder, wherein the first end of the hydraulic cylinder is connected to one of the first fork and the second fork, and the other end of the hydraulic cylinder is connected to one of the third fork and the fourth fork.

[0006] In one embodiment, at least one of the hydraulic cylinders is arranged at an angle.

[0007] In one embodiment, all the hydraulic cylinders are arranged at an angle.

[0008] In one embodiment, the first end of the hydraulic cylinder is connected between the first end of the second fork and the first hinge point; the second end of the hydraulic cylinder is connected between the second end of the third fork and the second hinge point.

[0009] In one embodiment, the first end of the hydraulic cylinder is closer to the first end of the second fork, and the second end of the hydraulic cylinder is closer to the second hinge point.

[0010] In one embodiment, the first end of the hydraulic cylinder is connected between the first end of the first fork and the first hinge point; the second end of the hydraulic cylinder is connected between the second end of the fourth fork and the second hinge point.

[0011] In one embodiment, the first end of the hydraulic cylinder is closer to the first end of the first fork, and the second end of the hydraulic cylinder is closer to the second hinge point.

[0012] In one implementation, the hydraulic cylinders of multiple series-connected secondary scissor lift units are arranged alternately, that is, starting from the secondary scissor lift unit closest to the slide bar end, the two ends of the hydraulic cylinders of the odd-numbered secondary scissor lift units are respectively connected to the second fork and the third fork; the two ends of the hydraulic cylinders of the even-numbered secondary scissor lift units are respectively connected to the first fork and the fourth fork.

[0013] In one implementation, the multiple cascaded secondary scissor units are three, namely a first secondary scissor unit, a second secondary scissor unit, and a third secondary scissor unit.

[0014] The present invention also provides a control system for a large-size extension mechanism based on multi-cylinder drive, including a controller, a control circuit, and a large-size extension mechanism as described in any of the above embodiments.

[0015] This invention optimizes the hinge point arrangement under a multi-hydraulic cylinder drive scheme and proposes a multi-cylinder coordinated synchronous drive control system considering the deformation of a large-size scissor-type extension mechanism. First, the multi-cylinder position layout of the scissor-type extension mechanism is optimized to reduce the driving force requirements of the hydraulic cylinders. Second, considering the deformation of the large-size extension mechanism under the influence of gravity and mounting components, the stroke trajectory of the multi-cylinders during the deployment process is planned. Furthermore, by combining equivalent sliding mode control, the entire machine deploys in a coordinated manner, avoiding the problem of multi-cylinder drive stagnation caused by deformation. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the unfolding mechanism of the present invention;

[0017] Figure 2 This is a structural diagram of the scissor lift system of the present invention;

[0018] Figure 3 Force diagram of the simplified scissor lift model of the present invention;

[0019] Figure 4 This is a side view of the extension mechanism of the present invention deformed under its own weight;

[0020] Figure 5 This is a schematic diagram showing the positions of multiple cross sections of the extension mechanism of the present invention;

[0021] Figure 6 for Figure 5 A cross-sectional view at the mid-section, where A is at section 1 and B is at section 2;

[0022] Figure 7 The present invention considers the ideal extension stroke trajectory diagram of each cylinder under deformation;

[0023] Figure 8 This is a schematic diagram of the valve-controlled asymmetric hydraulic cylinder structure of the present invention;

[0024] Figure 9 This is a block diagram of the valve-controlled asymmetric hydraulic cylinder system of the present invention;

[0025] Figure 10 This is a schematic diagram illustrating the multi-cylinder coordinated synchronous deployment control principle for the present invention, considering deformation under the influence of gravity and load.

[0026] Figure 11 This is a block diagram of the multi-cylinder synchronous control system of the present invention;

[0027] Figure 12 The actual extension stroke trajectory of each cylinder under deformation is considered in the present invention.

[0028] Figure 13 This is a schematic diagram illustrating the synchronization error of the coordinated deployment of each cylinder in this invention;

[0029] Figure 14 This is a schematic diagram showing the synchronization error of each cylinder before optimization. Detailed Implementation

[0030] To make the technical solutions and advantages of the present invention clearer, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Some technical terms and expressions used herein have the same meaning as understood by those skilled in the art to which this application pertains.

[0031] like Figures 1-2 As shown, a large-size scissor-type extension mechanism of the present invention includes a frame 100, a mounting member 300, and a scissor system 200, wherein the multiple parallel frames 100 are connected to the scissor system 200 and can be extended and retracted under the action of the scissor system 200, and multiple mounting members 300 are provided on each frame 100.

[0032] The scissor lift system 200 includes a slide bar 210, a slider 220, a scissor lift mechanism 230, and a hydraulic cylinder 240. The scissor lift mechanism 230 includes multiple series-connected secondary scissor lift units 400. Each secondary scissor lift unit 400 includes four forks of equal length: a first fork, a second fork, a third fork, and a fourth fork. The first and second forks are intersected and hinged at the intersection to form a first hinge point; the third and fourth forks are intersected and hinged at the intersection to form a second hinge point; the second end of the first fork is hinged to the first end of the fourth fork; the second end of the second fork is hinged to the first end of the third fork; the second end of the fourth fork is hinged to the first end of the first fork of an adjacent secondary scissor lift unit 400; and the second end of the third fork is hinged to the first end of the second fork of an adjacent secondary scissor lift unit 400.

[0033] In this unit, the first end of the first fork of the first secondary scissor lift unit 400 is hinged to the slide bar 210, and the first end of the second fork of the first secondary scissor lift unit 400 is hinged to the slider 220; the slider 220 can slide on the slide bar 210.

[0034] Each frame 100 is connected to the second hinge point of the secondary scissor unit 400 and can move with the displacement of the second hinge point;

[0035] A hydraulic cylinder 240 is provided in each secondary scissor lift unit 400, wherein the first end of the hydraulic cylinder 240 is connected to one of the first fork and the second fork, and the other end of the hydraulic cylinder 240 is connected to one of the third fork and the fourth fork.

[0036] This invention employs multiple secondary scissor lift units 400 connected in series to achieve multi-drive and high extension ratio of the extension mechanism, meeting the deployment requirements of large-size extension mechanisms. Furthermore, each secondary scissor lift unit 400 is equipped with a hydraulic cylinder 240 for drive, thus enabling a multi-cylinder distributed synchronous drive solution for large-size scissor lift mechanisms.

[0037] In one embodiment, at least one of the hydraulic cylinders 240 is arranged at an angle. Preferably, all of the hydraulic cylinders 240 are arranged at an angle. That is, the hydraulic cylinders 240 are arranged at an angle relative to the slide bar 210, not parallel or perpendicular. With a parallel arrangement, the hydraulic cylinder 240 experiences a larger force under the same load in the initial position; with a perpendicular arrangement, the expansion ratio is smaller and the overall structure appears bulky. Using an angled arrangement results in less force, a less bulky structure, and the extension length of the scissor lift unit can reach more than twice the stroke of the hydraulic cylinder 240.

[0038] In one embodiment, the first end of the hydraulic cylinder 240 is connected between the first end of the second fork and the first hinge point; the second end of the hydraulic cylinder 240 is connected between the second end of the third fork and the second hinge point. Preferably, the first end of the hydraulic cylinder 240 is closer to the first end of the second fork, and the second end of the hydraulic cylinder 240 is closer to the second hinge point. Alternatively, the first end of the hydraulic cylinder 240 is connected between the first end of the first fork and the first hinge point; the second end of the hydraulic cylinder 240 is connected between the second end of the fourth fork and the second hinge point. Preferably, the first end of the hydraulic cylinder 240 is closer to the first end of the first fork, and the second end of the hydraulic cylinder 240 is closer to the second hinge point. With this design, the installation distance and stroke of the hydraulic cylinder 240 are greater, and the extension force output and extension length are also better, satisfying the large extension ratio requirement of the extension mechanism and achieving large load drive under large size conditions.

[0039] In one embodiment, the extension mechanism includes two sets of scissor systems 200, which are identical in structure and arranged in parallel alignment, with each of the frame 100 simultaneously connected to both sets of scissor systems 200.

[0040] In one embodiment, the hydraulic cylinders 240 of the multiple series-connected secondary scissor lift units 400 are arranged alternately. That is, starting from the secondary scissor lift unit 400 closest to the slide bar 210, the two ends of the hydraulic cylinders 240 of the odd-numbered secondary scissor lift units 400 (i.e., the first, third, fifth, etc.) are respectively connected to the second fork and the third fork; the two ends of the hydraulic cylinders 240 of the even-numbered secondary scissor lift units 400 (the second, fourth, sixth, etc.) are respectively connected to the first fork and the fourth fork.

[0041] The difference between odd and even number arrangements lies in the installation position of the hinge point of the bottom hydraulic cylinder 240. In the odd number arrangement, the hinge point of the hydraulic cylinder 2401 is arranged on the sliding block 220 and will move accordingly, while in the even number arrangement, the hinge point of the hydraulic cylinder 2401 is arranged on the fixed hinge point and cannot move.

[0042] The two arrangement methods in the implementation plan are analyzed to determine which arrangement has lower driving requirements for the hydraulic cylinder 240 in the initial extended state. Under both arrangement methods, the relationship between the thrust F of the hydraulic cylinder 240 and the load force P is determined using the principle of virtual displacement:

[0043] Odd number arrangement:

[0044]

[0045] Even number arrangement

[0046]

[0047] Comparing the two equations, we can see that at the same expansion angle... Below are:

[0048]

[0049] In the formula: The hydraulic cylinder 240 drives the load force;

[0050] The length of the fork arm;

[0051] For the unfolding angle of the extension mechanism;

[0052] The distance between the left end of hydraulic cylinder 240 and the first hinge point of the secondary fork unit where the hydraulic cylinder is located;

[0053] This is the distance from the right end of hydraulic cylinder 240 to the second hinge point of the secondary fork unit where the hydraulic cylinder is located.

[0054] Therefore, in the preferred embodiment, the first hydraulic cylinder 240 on the left is arranged with both ends on the second and third forks of the secondary scissor lift unit 400, which can further reduce the driving requirements of the hydraulic cylinder 240 and help to reduce the size of the hydraulic cylinder 240.

[0055] In one implementation, the multiple cascaded secondary scissor lift units 400 are divided into three, namely a first secondary scissor lift unit, a second secondary scissor lift unit, and a third secondary scissor lift unit, as shown below. Figure 3 As shown, the four forks of the first secondary scissor lift unit are AD, BC, CF, and DE (corresponding to the first to fourth forks respectively), and their two hinge points are O1 and O2 respectively; the four forks of the second secondary scissor lift unit are EH, FG, GJ, and HI (corresponding to the first to fourth forks respectively), and their two hinge points are O3 and O4 respectively; the four forks of the third secondary scissor lift unit are IL, JK, KV, and LU (corresponding to the first to fourth forks respectively), and their two hinge points are O5 and O6 respectively.

[0056] In this design, the hydraulic cylinder 240 of the first and second-stage scissor lift units is a first hydraulic cylinder 240. The first end of the first hydraulic cylinder 240 is connected to point M on the fork carriage BC, with a distance 'a' between point M and point O1. The second end of the first hydraulic cylinder 240 is connected to point N on the fork carriage CF, with a distance 'b' between point N and point O2. The angle between the first hydraulic cylinder 240 (represented by MN for simplicity) and the slide rod 210 (represented by line AB in the diagram for simplicity) is β, and the angle between the fork carriage AD and the slide rod 210AB is α. The position and posture of the third hydraulic cylinder 240 in the third and second-stage scissor lift units are the same as those of the first hydraulic cylinder 240 in the first-stage scissor lift units. The position and posture of the second hydraulic cylinder 240 in the second-stage scissor lift units are mirror images of those of the first hydraulic cylinder 240 in the first-stage scissor lift units.

[0057] The hydraulic cylinder 240 of the second-stage scissor lift unit is a second hydraulic cylinder 240. The first end of the second hydraulic cylinder 240 is connected to point P on the fork carriage EH, and the second end of the second hydraulic cylinder 240 is connected to point Q on the fork carriage HI. The angle between the second hydraulic cylinder 240 (PQ) and the slide rod 210 (AB) is β, and the direction of this angle is opposite to the direction of the angle between the first hydraulic cylinder 240 and the slide rod 210 (e.g., ...). Figure 3As shown, the angle between the first hydraulic cylinder 240 and the slide rod 210 opens downwards, while the angle between the second hydraulic cylinder 240 and the slide rod 210 opens upwards. The distances between point P and O3, and between point R and O5, are all equal to 'a'; the distances between point Q and O4, and between point S and O6, are all equal to 'b'.

[0058] The hydraulic cylinder 240 of the third-level scissor lift unit is a third hydraulic cylinder 240. The first end of the third hydraulic cylinder 240 is connected to point R on the fork carriage JK, and the second end of the third hydraulic cylinder 240 is connected to point S on the fork carriage KV. The included angle between the third hydraulic cylinder 240 (RS) and the slide rod 210 (AB) is β.

[0059] In the preferred embodiment, the positions of points M and N are determined by the following method:

[0060] According to the principle of virtual work:

[0061]

[0062] In the formula: , , —Institutions in , , The direction of the external force;

[0063] , , —Institutions in , , Virtual displacement in direction;

[0064] Release the constraints of hydraulic cylinders 240MN, PQ, and RS with the fork, and replace them with a pair of forces F. According to the formula of the virtual displacement principle, we get:

[0065]

[0066] In the formula:

[0067] F represents the thrust of the hydraulic cylinder, which is 240.

[0068] F For load capacity;

[0069] —Points M, N, P, Q, R, and S are located at Component of force in direction;

[0070] —Points M, N, P, Q, R, and S are located at Component of force in direction;

[0071] —Points M, N, P, Q, R, and S are located at Virtual displacement in direction;

[0072] —Points M, N, P, Q, R, and S are located at Virtual displacement in direction;

[0073] —The virtual displacement of the end of the scissor mechanism 230 in the unfolding direction;

[0074] Based on the structural parameters of the scissor mechanism 230, the coordinates of each hinge point M, N, P, Q, R, and S of the hydraulic cylinder 240 are obtained, and the virtual displacements of each point are obtained through variational calculations.

[0075] Point M:

[0076] Point N:

[0077] Point P:

[0078] Q point:

[0079] Point R: xx

[0080] Point S:

[0081] Similarly, calculate the virtual displacement at the end and the magnitude of the component of the hydraulic cylinder's 240 thrust:

[0082]

[0083]

[0084] In the formula: The angle between the installation position of hydraulic cylinder 240 and the horizontal direction;

[0085] The distance between the left end of hydraulic cylinder 240 and the first hinge point of the secondary fork unit where the hydraulic cylinder is located;

[0086] This is the distance from the right end of hydraulic cylinder 240 to the second hinge point of the secondary fork unit where the hydraulic cylinder is located.

[0087] Furthermore, based on the structural parameters, we know that:

[0088]

[0089] The relationship between the thrust F of hydraulic cylinder 240 and the load P is determined as follows:

[0090]

[0091] in:

[0092]

[0093] The minimum installation dimensions of hydraulic cylinder 240 are

[0094]

[0095] In optimizing the installation position of hydraulic cylinder 240, this study utilizes the local optimization function fmincon in Matlab software. This function can find the optimal solution satisfying the given constraints from a given starting point by using the derivative information of the objective function and the constraint function. In this invention, a scissor-type horizontal mechanism with the following structural parameters is used as an example to optimize the layout of the hydraulic cylinder 240, and the optimized hinge point arrangement parameters and results of the hydraulic cylinder 240 are presented.

[0096] Structural parameters used in this invention

[0097]

[0098] Results of optimized arrangement of 240 hinge points in hydraulic cylinder:

[0099]

[0100] In a preferred embodiment, the length variation of the first hydraulic cylinder 240 during its working stroke is controlled according to the following formula:

[0101] MN:

[0102] The length variation of the second hydraulic cylinder 240 during its working stroke is controlled according to the following formula:

[0103] PQ:

[0104] The length variation of the third hydraulic cylinder 240 during its working stroke is controlled according to the following formula:

[0105] RS:

[0106] The parameters are explained below:

[0107] Total length of scissor lift

[0108] Fork length

[0109] Hydraulic cylinder 240 optimized arrangement of hinge point position

[0110] Hydraulic cylinder 240 optimized arrangement of hinge point position

[0111] Hydraulic cylinder 240 mass

[0112] Single mount weight 300

[0113] gravitational acceleration

[0114] Forklift thickness

[0115] Fork width

[0116] Forklift material density

[0117] Forklift material elastic modulus

[0118] This approach enables truly coordinated and synchronous driving of large-size scissor lift mechanisms. This is because, after the scissor lift mechanism 230 is horizontally deployed, it will exhibit a drooping deformation due to gravity. The amount of drooping deformation gradually increases from the base to the end. If the strokes of the three hydraulic cylinders 240 are identical, coordinated and synchronous deployment of the entire mechanism cannot be achieved, resulting in a multi-cylinder drive stagnation problem. The above conclusion is reached in this invention based on the following considerations:

[0119] The scissor-type horizontal deployment mechanism can be equivalent to a cantilever beam structure, and the effect of gravity can be regarded as a distributed load. Its stress-deformation diagram in the side view is shown below. Figure 4 As shown:

[0120] Cantilever beam deflection equation

[0121] Extension angle

[0122]

[0123] Because the cross-section of the scissor mechanism 230 changes at every point during its deployment as the scissor tip moves, the moments of inertia of the equivalent cantilever beam are considered in calculating the moments of inertia of the cross-sections at both the central hinge point and the outer hinge point. The calculation of the moments of inertia of the two sections is as follows: Figure 5 , 6 As shown:

[0124] Since these two types of cross sections alternate in the scissor lift mechanism 230, and their moments of inertia are not significantly different, the median of these two moments of inertia is taken as the moment of inertia of the equivalent cantilever beam. The fork frame is made of #45 steel, and its elastic modulus is... The moments of inertia of the two sections are as follows:

[0125] Moment of inertia of section 1:

[0126] Moment of inertia of section 2:

[0127] Therefore, the equivalent moment of inertia of the equivalent cantilever beam can be obtained as follows: ,in It's the width of the fork. It's the thickness of the fork. It's the length of the fork, and also... It is the extension length of the scissor lift mechanism 230.

[0128] Based on the deflection formula, and considering that the hydraulic cylinder 240 is spatially tilted due to the sag of the scissor mechanism 230, the relative deflection at the two hinge points of the hydraulic cylinder 240 needs to be considered to calculate the extension length of the hydraulic cylinder 240. Finally, the extension length of each hydraulic cylinder 240 can be calculated:

[0129] MN:

[0130] PQ:

[0131] RS:

[0132] In one implementation, the values ​​of the parameters are shown in the table below.

[0133]

[0134] Substituting the above mechanism parameters into the formula for calculating the synchronous extension length of hydraulic cylinder 240, we can obtain:

[0135] MN:

[0136] PQ:

[0137] RS:

[0138] As can be seen from the above formula, the length of the hydraulic cylinder 240 and the length of the extension mechanism exhibit a non-linear relationship as the extension mechanism unfolds. Therefore, when controlling the coordinated unfolding of the whole machine, the length of the hydraulic cylinder 240 should be determined based on the extension mechanism's unfolding length in order to ensure that the multi-cylinder drive's hindrance is avoided under the influence of deformation.

[0139] In one implementation, the total length of the deployment mechanism is extended from the original 12m to 20m, and the length of the hydraulic cylinder 240 is also extended from approximately 3m to 5m. Combining the above formula, the stroke trajectory of the multiple hydraulic cylinders 240 that coordinate and synchronize the deployment of the extension mechanism can be obtained, such as... Figure 7 As shown. An equivalent sliding mode control method is employed during the control process to achieve high-precision tracking and extension of the hydraulic cylinder 240, ensuring coordinated and synchronous deployment of the entire machine under deformation caused by gravity and load.

[0140] In one embodiment, the hydraulic cylinder 240 is controlled according to the following formula:

[0141]

[0142] in, The total equivalent mass of the piston and the load;

[0143] This refers to the effective working area of ​​the 240 piston in the hydraulic cylinder.

[0144] The damping coefficient for the hydraulic cylinder is 240.

[0145] For load elastic stiffness;

[0146] For hydraulic cylinder 240 load;

[0147] The elastic modulus of the oil;

[0148] The total volume of the two chambers of the hydraulic cylinder 240 is ,

[0149] This represents the initial volume within chamber 240 of the hydraulic cylinder.

[0150] The volume of the oil inlet chamber of the hydraulic cylinder is 240. The volume of the return oil chamber of the hydraulic cylinder is 240.

[0151] The total flow rate minus the pressure coefficient. , :

[0152] Flow pressure coefficient ;

[0153] The total leakage coefficient is... ;

[0154] It has two input quantities, namely control quantities. and driving load force When two input quantities act on a linear system simultaneously, they can be processed separately, and then the superposition principle can be applied to obtain the total output response of the closed-loop control system.

[0155] Specifically:

[0156] Based on the driving parameters of hydraulic cylinder 240, the transfer function of each component is determined. The control quantity is the control command calculated and given by the controller. The driving load force is the load pressure on hydraulic cylinder 240 when the scissor mechanism 230 is extended. This input remains basically constant throughout the entire extension process of scissor mechanism 230, and can be simplified by treating it as a constant driving load force input.

[0157] like Figure 8 The hydraulic cylinder 240 of the scissor lift mechanism 230 includes a servo amplifier, an electro-hydraulic servo valve, and a displacement sensor. The piston's position movement (i.e., the unfolding movement of the scissor lift mechanism 230) is controlled by an input voltage. The input voltage is transmitted to the servo valve according to the required position, thereby generating a controller signal to control the servo valve, causing the position of the spool valve to change. The piston's movement is controlled by the oil supplied to each chamber of the cylinder. A position transfer function model of the system is established based on the flow continuity equation of the valve-controlled asymmetric cylinder, the valve's flow equation, the force balance equation of the hydraulic cylinder 240 and the load, and the transfer functions of the main components. In this invention, the hydraulic cylinder 240 is a valve-controlled asymmetric hydraulic cylinder 240, such as... Figure 8 As shown, without considering leakage, the continuity equations for the two chambers of hydraulic cylinder 240 are established based on the principle of mass conservation of hydraulic systems.

[0158] Left cavity continuity equation:

[0159] (1.1)

[0160] Right-cavity continuity equation:

[0161] (1.2)

[0162] In formula (1.1) The external leakage coefficient of hydraulic cylinder 240. ;

[0163] The external leakage coefficient of hydraulic cylinder 240. ;

[0164] The pressure in the left chamber of hydraulic cylinder 240. ;

[0165] For the right chamber pressure of hydraulic cylinder 240, ;

[0166] The volume of the oil inlet chamber of the hydraulic cylinder is 240. ;

[0167] The volume of the return oil chamber of the hydraulic cylinder is 240.

[0168] The hydraulic cylinder has an oil inlet flow rate of 240.

[0169] For the hydraulic cylinder, the return oil flow rate is 240. ;

[0170] The elastic modulus of the oil.

[0171] The volume of the oil inlet chamber of the hydraulic cylinder 240 is

[0172] The return oil chamber volume of hydraulic cylinder 240 is

[0173] In the formula , The initial volume of the two chambers of the hydraulic cylinder 240 is considered to be a constant.

[0174] The total volume of the two chambers of the hydraulic cylinder 240 is

[0175] In the formula This represents the volume of the left and right chambers when the piston is in the middle position.

[0176] Differentiating equation (4.4) yields

[0177] Differentiating equation (4.5) yields

[0178] The pressure difference between the two chambers of hydraulic cylinder 240 is

[0179] The oil pump's supply pressure is

[0180] Adding equation (4.8) to equation (4.9) yields

[0181] Subtracting equation (4.8) from equation (4.9) yields

[0182] If the oil pump's oil supply pressure is constant, then = constant.

[0183] Differentiating equation (4.10), we get

[0184] Differentiating equation (4,11), we get

[0185] Subtracting equation (4.3) from equation (4.2), and substituting equations (4.6), (4.7), (4.12), and (4.13) into the equation, we obtain...

[0186]

[0187] Take the formula The total leakage coefficient, (This represents the average flow rate in the pipeline; if leakage is not considered, then...) ) and combined with the previous formula

[0188] From the above formula, we get

[0189]

[0190] The force balance equations for hydraulic cylinder 240 are established based on the physical model.

[0191]

[0192] In the formula The total equivalent mass of the piston and load. The damping coefficient for the hydraulic cylinder is 240. For load elastic stiffness, For hydraulic cylinder 240 load.

[0193] Servo valve load flow With valve core displacement Pressure difference between the two chambers of the hydraulic cylinder There is a non-linear relationship; the valve coefficient changes with the valve's operating point. and It is also changing, and in order to build a system model, it needs to be linearized. By expanding the servo valve into a linear form at its rated operating point, we can obtain:

[0194]

[0195] Thus, the following basic equations can be obtained.

[0196]

[0197] Taking the Laplace transform of the above equation and setting the initial conditions to zero, we get

[0198]

[0199] System block diagrams can be drawn as follows Figure 9 As shown, where :

[0200] Thus, we can obtain

[0201]

[0202] In one implementation, a tracking controller is provided for each hydraulic cylinder 240, wherein the tracking control law of the tracking controller is:

[0203]

[0204] in, The integral coefficient is... The sliding mode coefficient is , These are the coefficients of the saturation function. To switch the gain coefficient, a custom coefficient is defined based on the parameters of hydraulic cylinder 240:

[0205]

[0206] For equivalent control quantity, To switch robust control inputs

[0207] Specifically: Based on the various parameters of hydraulic cylinder 240, the transfer function of hydraulic cylinder 240 can be established, and the parameters in the tracking control law can be determined. , , as well as The controller bases its decisions on the system state variables. After calculating the control quantity, the total control quantity output is given. The hydraulic cylinder 240 is executed as a control command for the servo valve.

[0208] like Figure 10 This is a schematic diagram of the multi-cylinder coordinated synchronous deployment control principle considering deformation under the influence of gravity and load.

[0209] The displacement command for the multi-hydraulic cylinder 240 is Enter the first The displacement command signal for hydraulic cylinder 240 is Then the first Tracking error of 240 hydraulic cylinders Define 3 state variables. The state-space model for the tracking error of hydraulic cylinder 240 is then:

[0210]

[0211] In the formula:

[0212] generalized disturbance

[0213] A tracking controller is designed for each channel to eliminate the following error of the hydraulic cylinder 240, which can achieve the following results: Figure 11 The multi-cylinder controller shown.

[0214] The control input for each valve-controlled cylinder is determined by a 240° stroke plan of the hydraulic cylinder, taking into account the effects of gravity and load. An integral sliding surface design is used for the sliding surface of the tracking controller.

[0215]

[0216] In the formula: The sliding mode coefficient; The integral coefficient; The time variable is used. The dynamic quality of the sliding mode is determined by... The decision can be determined through pole configuration. The value;

[0217] A tracking controller is designed using equivalent sliding mode control, and an exponential reaching law is employed. Its control law can be derived from the equivalent control... and switching robust control Composition. Ignoring interference and uncertainty for now, by taking... The equivalent control term of the tracking controller can be easily obtained. Then let Through analysis and will Substitute, make This establishes the switching robustness term of the sliding mode control law. ,

[0218] The exponential reaching law is modified to reduce chattering when the system enters the sliding surface. The modified reaching law and switching robust control term are as follows:

[0219]

[0220]

[0221] in Let be a saturation function, and its expression is: These are the coefficients of the saturation function. The saturation coefficient is... The threshold value is the saturation function threshold.

[0222]

[0223] The present invention first optimizes the positional layout of the multiple hydraulic cylinders 240, effectively reducing the minimum thrust requirement of the hydraulic cylinders 240. Under the condition of an effective load of 2000N, the minimum thrust requirement under the optimized layout can be reduced to 12164N. Then, based on this optimized layout, considering the deformation under the influence of gravity and load, the stroke trajectory of the hydraulic cylinders 240 during the deployment process is planned. Furthermore, the equivalent sliding mode control algorithm is combined to ensure the coordinated and synchronous deployment of the large-size scissor-type extension mechanism.

[0224] To verify the effectiveness of the method of the present invention, the following simulation experiment was conducted: The performance of the predictive controller was simulated and designed in MATLAB. The parameters of the electro-hydraulic servo valve-controlled asymmetric hydraulic cylinder 240 system were selected as follows: hydraulic cylinder 240 flow gain. Flow-pressure gain coefficient Hydraulic cylinder 240 effective area The total volume of the two chambers of the hydraulic cylinder 240 Equivalent mass of load Load viscous damping coefficient Equivalent load stiffness The overall leakage coefficient of hydraulic oil Oil elastic modulus .

[0225] The output is predicted based on the mathematical model of the hydraulic servo system, and simulation is performed in MATLAB. The simulation parameters of the tracking error controller are designed using equivalent sliding mode control: sliding mode hyperplane coefficient. Integral coefficient saturation function coefficients saturation function threshold Switching gain coefficient The simulation examines the stroke changes of each hydraulic cylinder 240 during the deployment process and the coordination and synchronization errors during deployment.

[0226] The multi-cylinder coordinated drive control method for a large-size scissor lift mechanism, considering deformation under gravity and load, proposed in this invention enables coordinated deployment under gravitational deformation fields. The multi-cylinder stroke trajectory during deployment is as follows: Figure 12 As shown, the synchronization error during unfolding is less than 10mm, as... Figure 13 As shown. However, without considering deformation under gravity, the driving load of the hydraulic cylinder 240 will increase, and the synchronization error during deployment can reach 28mm. Furthermore, due to mutual obstruction, the error fluctuation is significant, such as... Figure 14 As shown.

[0227] The present invention also provides a control system for a large-size extension mechanism based on a multi-cylinder drive, specifically implemented using the above-described unfolding mechanism.

[0228] In one implementation, the control system controls the hydraulic system according to the following formula:

[0229]

[0230] In one implementation, a tracking controller is provided for each hydraulic cylinder 240, wherein the tracking control law of the tracking controller is as follows:

[0231]

[0232] like Figures 1-2 As shown, a large-size scissor-type extension mechanism of the present invention includes a frame 100, a mounting member 300, and a scissor system 200, wherein the multiple parallel frames 100 are connected to the scissor system 200 and can be extended and retracted under the action of the scissor system 200, and multiple mounting members 300 are provided on each frame 100.

[0233] The scissor lift system 200 includes a slide bar 210, a slider 220, a scissor lift mechanism 230, and a hydraulic cylinder 240. The scissor lift mechanism 230 includes multiple series-connected secondary scissor lift units 400. Each secondary scissor lift unit 400 includes four forks of equal length: a first fork, a second fork, a third fork, and a fourth fork. The first and second forks are intersected and hinged at the intersection to form a first hinge point; the third and fourth forks are intersected and hinged at the intersection to form a second hinge point; the second end of the first fork is hinged to the first end of the fourth fork; the second end of the second fork is hinged to the first end of the third fork; the second end of the fourth fork is hinged to the first end of the first fork of an adjacent secondary scissor lift unit 400; and the second end of the third fork is hinged to the first end of the second fork of an adjacent secondary scissor lift unit 400.

[0234] In this unit, the first end of the first fork of the first secondary scissor lift unit 400 is hinged to the slide bar 210, and the first end of the second fork of the first secondary scissor lift unit 400 is hinged to the slider 220; the slider 220 can slide on the slide bar 210.

[0235] Each frame 100 is connected to the second hinge point of the secondary scissor unit 400 and can move with the displacement of the second hinge point;

[0236] A hydraulic cylinder 240 is provided in each secondary scissor lift unit 400, wherein the first end of the hydraulic cylinder 240 is connected to one of the first fork and the second fork, and the other end of the hydraulic cylinder 240 is connected to one of the third fork and the fourth fork.

[0237] This invention employs multiple secondary scissor lift units 400 connected in series to achieve multi-drive and high extension ratio of the extension mechanism, meeting the deployment requirements of large-size extension mechanisms. Furthermore, each secondary scissor lift unit 400 is equipped with a hydraulic cylinder 240 for drive, thus enabling a multi-cylinder distributed synchronous drive solution for large-size scissor lift mechanisms.

[0238] In one embodiment, at least one of the hydraulic cylinders 240 is arranged at an angle. Preferably, all of the hydraulic cylinders 240 are arranged at an angle. That is, the hydraulic cylinders 240 are arranged at an angle relative to the slide bar 210, not parallel or perpendicular. With a parallel arrangement, the hydraulic cylinder 240 experiences a larger force under the same load in the initial position; with a perpendicular arrangement, the expansion ratio is smaller and the overall structure appears bulky. Using an angled arrangement results in less force, a less bulky structure, and the extension length of the scissor lift unit can reach more than twice the stroke of the hydraulic cylinder 240.

[0239] In one embodiment, the first end of the hydraulic cylinder 240 is connected between the first end of the second fork and the first hinge point; the second end of the hydraulic cylinder 240 is connected between the first end of the third fork and the second hinge point. Preferably, the first end of the hydraulic cylinder 240 is closer to the first end of the second fork, and the second end of the hydraulic cylinder 240 is closer to the second hinge point. Alternatively, the first end of the hydraulic cylinder 240 is connected between the first end of the first fork and the first hinge point; the second end of the hydraulic cylinder 240 is connected between the first end of the fourth fork and the second hinge point. Preferably, the first end of the hydraulic cylinder 240 is closer to the first end of the second fork, and the second end of the hydraulic cylinder 240 is closer to the second hinge point. With this design, the installation distance and stroke of the hydraulic cylinder 240 are greater, and the extension force output and extension length are also better, satisfying the large extension ratio requirement of the extension mechanism and achieving large load drive under large size conditions.

[0240] In one embodiment, the extension mechanism includes two sets of scissor systems 200, which are identical in structure and arranged in parallel alignment, with each of the frame 100 simultaneously connected to both sets of scissor systems 200.

[0241] In one embodiment, the hydraulic cylinders 240 of the multiple series-connected secondary scissor lift units 400 are arranged alternately. That is, starting from the secondary scissor lift unit 400 closest to the slide bar 210, the two ends of the hydraulic cylinders 240 of the odd-numbered secondary scissor lift units 400 (i.e., the first, third, fifth, etc.) are respectively connected to the second fork and the third fork; the two ends of the hydraulic cylinders 240 of the even-numbered secondary scissor lift units 400 (the second, fourth, sixth, etc.) are respectively connected to the first fork and the fourth fork.

[0242] The difference between odd and even number arrangements lies in the installation position of the hinge point of the bottom hydraulic cylinder 240. In the odd number arrangement, the hinge point of the hydraulic cylinder 2401 is arranged on the sliding block 220 and will move accordingly, while in the even number arrangement, the hinge point of the hydraulic cylinder 2401 is arranged on the fixed hinge point and cannot move.

[0243] The two arrangement methods in the implementation plan are analyzed to determine which arrangement has lower driving requirements for the hydraulic cylinder 240 in the initial extended state. Under both arrangement methods, the relationship between the thrust F of the hydraulic cylinder 240 and the load force P is determined using the principle of virtual displacement:

[0244] Odd number arrangement:

[0245]

[0246] Even number arrangement

[0247]

[0248] Comparing the two equations, we can see that at the same expansion angle... Below are:

[0249]

[0250] In the formula: The hydraulic cylinder 240 drives the load force;

[0251] The length of the fork arm;

[0252] For the unfolding angle of the extension mechanism;

[0253] The distance between the left end of hydraulic cylinder 240 and the first hinge point of the secondary fork unit where the hydraulic cylinder is located;

[0254] This is the distance from the right end of hydraulic cylinder 240 to the second hinge point of the secondary fork unit where the hydraulic cylinder is located.

[0255] Therefore, in the preferred embodiment, the first hydraulic cylinder 240 on the left is arranged with both ends on the second and third forks of the secondary scissor lift unit 400, which can further reduce the driving requirements of the hydraulic cylinder 240 and help to reduce the size of the hydraulic cylinder 240.

[0256] In one implementation, the multiple cascaded secondary scissor lift units 400 are divided into three, namely a first secondary scissor lift unit, a second secondary scissor lift unit, and a third secondary scissor lift unit, as shown below. Figure 3As shown, the four forks of the first secondary scissor lift unit are AD, BC, CF, and DE (corresponding to the first to fourth forks respectively), and their two hinge points are O1 and O2 respectively; the four forks of the second secondary scissor lift unit are EH, FG, GJ, and HI (corresponding to the first to fourth forks respectively), and their two hinge points are O3 and O4 respectively; the four forks of the third secondary scissor lift unit are IL, JK, KV, and LU (corresponding to the first to fourth forks respectively), and their two hinge points are O5 and O6 respectively.

[0257] In this design, the hydraulic cylinder 240 of the first and second-stage scissor lift units is a first hydraulic cylinder 240. The first end of the first hydraulic cylinder 240 is connected to point M on the fork carriage BC, with a distance 'a' between point M and point O1. The second end of the first hydraulic cylinder 240 is connected to point N on the fork carriage CF, with a distance 'b' between point N and point O2. The angle between the first hydraulic cylinder 240 (represented by MN for simplicity) and the slide rod 210 (represented by line AB in the diagram for simplicity) is β, and the angle between the fork carriage AD and the slide rod 210AB is α. The position and posture of the third hydraulic cylinder 240 in the third and second-stage scissor lift units are the same as those of the first hydraulic cylinder 240 in the first-stage scissor lift units. The position and posture of the second hydraulic cylinder 240 in the second-stage scissor lift units are mirror images of those of the first hydraulic cylinder 240 in the first-stage scissor lift units.

[0258] The hydraulic cylinder 240 of the second-stage scissor lift unit is a second hydraulic cylinder 240. The first end of the second hydraulic cylinder 240 is connected to point P on the fork carriage EH, and the second end of the second hydraulic cylinder 240 is connected to point Q on the fork carriage HI. The angle between the second hydraulic cylinder 240 (PQ) and the slide rod 210 (AB) is β, and the direction of this angle is opposite to the direction of the angle between the first hydraulic cylinder 240 and the slide rod 210 (e.g., ...). Figure 3 As shown, the angle between the first hydraulic cylinder 240 and the slide rod 210 opens downwards, while the angle between the second hydraulic cylinder 240 and the slide rod 210 opens upwards. The distances between point P and O3, and between point R and O5, are all equal to 'a'; the distances between point Q and O4, and between point S and O6, are all equal to 'b'.

[0259] The hydraulic cylinder 240 of the third-level scissor lift unit is a third hydraulic cylinder 240. The first end of the third hydraulic cylinder 240 is connected to point R on the fork carriage JK, and the second end of the third hydraulic cylinder 240 is connected to point S on the fork carriage KV. The included angle between the third hydraulic cylinder 240 (RS) and the slide rod 210 (AB) is β.

[0260] In the preferred embodiment, the positions of points M and N are determined by the following method:

[0261] According to the principle of virtual work:

[0262]

[0263] In the formula: , , —Institutions in , , The direction of the external force;

[0264] , , —Institutions in , , Virtual displacement in direction;

[0265] Release the constraints of hydraulic cylinders 240MN, PQ, and RS with the fork, and replace them with a pair of forces F. According to the formula of the virtual displacement principle, we get:

[0266]

[0267] In the formula:

[0268] F represents the thrust of the hydraulic cylinder, which is 240.

[0269] F For load capacity;

[0270] —Points M, N, P, Q, R, and S are located at Component of force in direction;

[0271] —Points M, N, P, Q, R, and S are located at Component of force in direction;

[0272] —Points M, N, P, Q, R, and S are located at Virtual displacement in direction;

[0273] —Points M, N, P, Q, R, and S are located at Virtual displacement in direction;

[0274] —The virtual displacement of the end of the scissor mechanism 230 in the unfolding direction;

[0275] Based on the structural parameters of the scissor mechanism 230, the coordinates of each hinge point M, N, P, Q, R, and S of the hydraulic cylinder 240 are obtained, and the virtual displacements of each point are obtained through variational calculations.

[0276] Point M:

[0277] Point N:

[0278] Point P:

[0279] Q point:

[0280] Point R:

[0281] Point S:

[0282] Similarly, calculate the virtual displacement at the end and the magnitude of the component of the hydraulic cylinder's 240 thrust:

[0283]

[0284]

[0285] In the formula: The angle between the installation position of hydraulic cylinder 240 and the horizontal direction;

[0286] The distance between the left end of hydraulic cylinder 240 and the first hinge point of the secondary fork unit where the hydraulic cylinder is located;

[0287] This is the distance from the right end of hydraulic cylinder 240 to the second hinge point of the secondary fork unit where the hydraulic cylinder is located.

[0288] Furthermore, based on the structural parameters, we know that:

[0289]

[0290] The relationship between the thrust F of hydraulic cylinder 240 and the load P is determined as follows:

[0291]

[0292] in:

[0293]

[0294] The minimum installation dimensions of hydraulic cylinder 240 are

[0295]

[0296] In optimizing the installation position of hydraulic cylinder 240, this study utilizes the local optimization function fmincon in Matlab software. This function can find the optimal solution satisfying the given constraints from a given starting point by using the derivative information of the objective function and the constraint function. In this invention, a scissor-type horizontal mechanism with the following structural parameters is used as an example to optimize the layout of the hydraulic cylinder 240, and the optimized hinge point arrangement parameters and results of the hydraulic cylinder 240 are presented.

[0297] Structural parameters used in this invention

[0298]

[0299] Results of optimized arrangement of 240 hinge points in hydraulic cylinder:

[0300]

[0301] In a preferred embodiment, the length variation of the first hydraulic cylinder 240 during its working stroke is controlled according to the following formula:

[0302] MN:

[0303] The length variation of the second hydraulic cylinder 240 during its working stroke is controlled according to the following formula:

[0304] PQ:

[0305] The length variation of the third hydraulic cylinder 240 during its working stroke is controlled according to the following formula:

[0306] RS:

[0307] The parameters are explained below:

[0308] Total length of scissor lift

[0309] Fork length

[0310] Hydraulic cylinder 240 optimized arrangement of hinge point position

[0311] Hydraulic cylinder 240 optimized arrangement of hinge point position

[0312] Hydraulic cylinder 240 mass

[0313] Single mount weight 300

[0314] gravitational acceleration

[0315] Forklift thickness

[0316] Fork width

[0317] Forklift material density

[0318] Forklift material elastic modulus

[0319] This approach enables truly coordinated and synchronous driving of large-size scissor lift mechanisms. This is because, after the scissor lift mechanism 230 is horizontally deployed, it will exhibit a drooping deformation due to gravity. The amount of drooping deformation gradually increases from the base to the end. If the strokes of the three hydraulic cylinders 240 are identical, coordinated and synchronous deployment of the entire mechanism cannot be achieved, resulting in a multi-cylinder drive stagnation problem. The above conclusion is reached in this invention based on the following considerations:

[0320] The scissor-type horizontal deployment mechanism can be equivalent to a cantilever beam structure, and the effect of gravity can be regarded as a distributed load. Its stress-deformation diagram in the side view is shown below. Figure 4 As shown:

[0321] Cantilever beam deflection equation

[0322] Extension angle

[0323]

[0324] Because the cross-section of the scissor mechanism 230 changes at every point during its deployment as the scissor tip moves, the moments of inertia of the equivalent cantilever beam are considered in calculating the moments of inertia of the cross-sections at both the central hinge point and the outer hinge point. The calculation of the moments of inertia of the two sections is as follows: Figure 5 , 6 As shown:

[0325] Since these two types of cross sections alternate in the scissor lift mechanism 230, and their moments of inertia are not significantly different, the median of these two moments of inertia is taken as the moment of inertia of the equivalent cantilever beam. The fork frame is made of #45 steel, and its elastic modulus is... The moments of inertia of the two sections are as follows:

[0326] Moment of inertia of section 1:

[0327] Moment of inertia of section 2:

[0328] Therefore, the equivalent moment of inertia of the equivalent cantilever beam can be obtained as follows: ,in It's the width of the fork. It's the thickness of the fork. It's the length of the fork, and also... It is the extension length of the scissor lift mechanism 230.

[0329] Based on the deflection formula, and considering that the hydraulic cylinder 240 is spatially tilted due to the sag of the scissor mechanism 230, the relative deflection at the two hinge points of the hydraulic cylinder 240 needs to be considered to calculate the extension length of the hydraulic cylinder 240. Finally, the extension length of each hydraulic cylinder 240 can be calculated:

[0330] MN:

[0331] PQ:

[0332] RS:

[0333] In one implementation, the values ​​of the parameters are shown in the table below.

[0334]

[0335] Substituting the above mechanism parameters into the formula for calculating the synchronous extension length of hydraulic cylinder 240, we can obtain:

[0336] MN:

[0337] PQ:

[0338] RS:

[0339] As can be seen from the above formula, the length of the hydraulic cylinder 240 and the length of the extension mechanism exhibit a non-linear relationship as the extension mechanism unfolds. Therefore, when controlling the coordinated unfolding of the whole machine, the length of the hydraulic cylinder 240 should be determined based on the extension mechanism's unfolding length in order to ensure that the multi-cylinder drive's hindrance is avoided under the influence of deformation.

[0340] In one implementation, the total length of the deployment mechanism is extended from the original 12m to 20m, and the length of the hydraulic cylinder 240 is also extended from approximately 3m to 5m. Combining the above formula, the stroke trajectory of the multiple hydraulic cylinders 240 that coordinate and synchronize the deployment of the extension mechanism can be obtained, such as... Figure 7 As shown. An equivalent sliding mode control method is employed during the control process to achieve high-precision tracking and extension of the hydraulic cylinder 240, ensuring coordinated and synchronous deployment of the entire machine under deformation caused by gravity and load.

[0341] In one embodiment, the hydraulic cylinder 240 is controlled according to the following formula:

[0342]

[0343] in, The total equivalent mass of the piston and the load;

[0344] This refers to the effective working area of ​​the 240 piston in the hydraulic cylinder.

[0345] The damping coefficient for the hydraulic cylinder is 240.

[0346] For load elastic stiffness;

[0347] For hydraulic cylinder 240 load;

[0348] The elastic modulus of the oil;

[0349] The total volume of the two chambers of the hydraulic cylinder 240 is ,

[0350] This represents the initial volume within chamber 240 of the hydraulic cylinder.

[0351] The volume of the oil inlet chamber of the hydraulic cylinder is 240. The volume of the return oil chamber of the hydraulic cylinder is 240.

[0352] The total flow rate minus the pressure coefficient. , :

[0353] Flow pressure coefficient ;

[0354] The total leakage coefficient is... ;

[0355] It has two input quantities, namely control quantities. and driving load force When two input quantities act on a linear system simultaneously, they can be processed separately, and then the superposition principle can be applied to obtain the total output response of the closed-loop control system.

[0356] Specifically:

[0357] Based on the driving parameters of hydraulic cylinder 240, the transfer function of each component is determined. The control quantity is the control command calculated and given by the controller. The driving load force is the load pressure on hydraulic cylinder 240 when the scissor mechanism 230 is extended. This input remains basically constant throughout the entire extension process of scissor mechanism 230, and can be simplified by treating it as a constant driving load force input.

[0358] like Figure 8 The hydraulic cylinder 240 of the scissor lift mechanism 230 includes a servo amplifier, an electro-hydraulic servo valve, and a displacement sensor. The piston's position movement (i.e., the unfolding movement of the scissor lift mechanism 230) is controlled by an input voltage. The input voltage is transmitted to the servo valve according to the required position, thereby generating a controller signal to control the servo valve, causing the position of the spool valve to change. The piston's movement is controlled by the oil supplied to each chamber of the cylinder. A position transfer function model of the system is established based on the flow continuity equation of the valve-controlled asymmetric cylinder, the valve's flow equation, the force balance equation of the hydraulic cylinder 240 and the load, and the transfer functions of the main components. In this invention, the hydraulic cylinder 240 is a valve-controlled asymmetric hydraulic cylinder 240, such as... Figure 8 As shown, without considering leakage, the continuity equations for the two chambers of hydraulic cylinder 240 are established based on the principle of mass conservation of hydraulic systems.

[0359] Left cavity continuity equation:

[0360] (1.1)

[0361] Right-cavity continuity equation:

[0362] (1.2)

[0363] In formula (1.1) The external leakage coefficient of hydraulic cylinder 240. ;

[0364] The external leakage coefficient of hydraulic cylinder 240. ;

[0365] The pressure in the left chamber of hydraulic cylinder 240. ;

[0366] For the right chamber pressure of hydraulic cylinder 240, ;

[0367] The volume of the oil inlet chamber of the hydraulic cylinder is 240. ;

[0368] The volume of the return oil chamber of the hydraulic cylinder is 240.

[0369] The hydraulic cylinder has an oil inlet flow rate of 240.

[0370] For the hydraulic cylinder, the return oil flow rate is 240. ;

[0371] The elastic modulus of the oil.

[0372] The volume of the oil inlet chamber of the hydraulic cylinder 240 is

[0373] The return oil chamber volume of hydraulic cylinder 240 is

[0374] In the formula , The initial volume of the two chambers of the hydraulic cylinder 240 is considered to be a constant.

[0375] The total volume of the two chambers of the hydraulic cylinder 240 is

[0376] In the formula This represents the volume of the left and right chambers when the piston is in the middle position.

[0377] Differentiating equation (4.4) yields

[0378] Differentiating equation (4.5) yields

[0379] The pressure difference between the two chambers of hydraulic cylinder 240 is

[0380] The oil pump's supply pressure is

[0381] Adding equation (4.8) to equation (4.9) yields

[0382] Subtracting equation (4.8) from equation (4.9) yields

[0383] If the oil pump's oil supply pressure is constant, then = constant.

[0384] Differentiating equation (4.10), we get

[0385] Differentiating equation (4,11), we get

[0386] Subtracting equation (4.3) from equation (4.2), and substituting equations (4.6), (4.7), (4.12), and (4.13) into the equation, we obtain...

[0387]

[0388] Take the formula The total leakage coefficient, (This represents the average flow rate in the pipeline; if leakage is not considered, then...) ) and combined with the previous formula

[0389] From the above formula, we get

[0390]

[0391] The force balance equations for hydraulic cylinder 240 are established based on the physical model.

[0392]

[0393] In the formula The total equivalent mass of the piston and load. The damping coefficient for the hydraulic cylinder is 240. For load elastic stiffness, For hydraulic cylinder 240 load.

[0394] Servo valve load flow With valve core displacement Pressure difference between the two chambers of the hydraulic cylinder There is a non-linear relationship; the valve coefficient changes with the valve's operating point. and It is also changing, and in order to build a system model, it needs to be linearized. By expanding the servo valve into a linear form at its rated operating point, we can obtain:

[0395]

[0396] Thus, the following basic equations can be obtained.

[0397]

[0398] Taking the Laplace transform of the above equation and setting the initial conditions to zero, we get

[0399]

[0400] System block diagrams can be drawn as follows Figure 9 As shown, where :

[0401] Thus, we can obtain

[0402]

[0403] In one implementation, a tracking controller is provided for each hydraulic cylinder 240, wherein the tracking control law of the tracking controller is:

[0404]

[0405] in, The integral coefficient is... The sliding mode coefficient is , These are the coefficients of the saturation function. To switch the gain coefficient, a custom coefficient is defined based on the parameters of hydraulic cylinder 240:

[0406]

[0407] For equivalent control quantity, To switch robust control inputs

[0408] Specifically: Based on the various parameters of hydraulic cylinder 240, the transfer function of hydraulic cylinder 240 can be established, and the parameters in the tracking control law can be determined. , , as well as The controller bases its decisions on the system state variables. After calculating the control quantity, the total control quantity output is given. The hydraulic cylinder 240 is executed as a control command for the servo valve.

[0409] like Figure 10 This is a schematic diagram of the multi-cylinder coordinated synchronous deployment control principle considering deformation under the influence of gravity and load.

[0410] The displacement command for the multi-hydraulic cylinder 240 is Enter the first The displacement command signal for hydraulic cylinder 240 is Then the first Tracking error of 240 hydraulic cylinders Define 3 state variables. The state-space model for the tracking error of hydraulic cylinder 240 is then:

[0411]

[0412] In the formula:

[0413] generalized disturbance

[0414] A tracking controller is designed for each channel to eliminate the following error of the hydraulic cylinder 240, which can achieve the following results:Figure 11 The multi-cylinder controller shown.

[0415] The control input for each valve-controlled cylinder is determined by a 240° stroke plan of the hydraulic cylinder, taking into account the effects of gravity and load. An integral sliding surface design is used for the sliding surface of the tracking controller.

[0416]

[0417] In the formula: The sliding mode coefficient; The integral coefficient; The time variable is used. The dynamic quality of the sliding mode is determined by... The decision can be determined through pole configuration. The value;

[0418] A tracking controller is designed using equivalent sliding mode control, and an exponential reaching law is employed. Its control law can be derived from the equivalent control... and switching robust control Composition. Ignoring interference and uncertainty for now, by taking... The equivalent control term of the tracking controller can be easily obtained. Then let Through analysis and will Substitute, make This establishes the switching robustness term of the sliding mode control law. ,

[0419] The exponential reaching law is modified to reduce chattering when the system enters the sliding surface. The modified reaching law and switching robust control term are as follows:

[0420]

[0421]

[0422] in Let be a saturation function, and its expression is: These are the coefficients of the saturation function. The saturation coefficient is... The threshold value is the saturation function threshold.

[0423]

[0424] The present invention first optimizes the positional layout of the multiple hydraulic cylinders 240, effectively reducing the minimum thrust requirement of the hydraulic cylinders 240. Under the condition of an effective load of 2000N, the minimum thrust requirement under the optimized layout can be reduced to 12164N. Then, based on this optimized layout, considering the deformation under the influence of gravity and load, the stroke trajectory of the hydraulic cylinders 240 during the deployment process is planned. Furthermore, the equivalent sliding mode control algorithm is combined to ensure the coordinated and synchronous deployment of the large-size scissor-type extension mechanism.

[0425] To verify the effectiveness of the method of the present invention, the following simulation experiment was conducted: The performance of the predictive controller was simulated and designed in MATLAB. The parameters of the electro-hydraulic servo valve-controlled asymmetric hydraulic cylinder 240 system were selected as follows: hydraulic cylinder 240 flow gain. Flow-pressure gain coefficient Hydraulic cylinder 240 effective area The total volume of the two chambers of the hydraulic cylinder 240 Equivalent mass of load Load viscous damping coefficient Equivalent load stiffness The overall leakage coefficient of hydraulic oil Oil elastic modulus .

[0426] The output is predicted based on the mathematical model of the hydraulic servo system, and simulation is performed in MATLAB. The simulation parameters of the tracking error controller are designed using equivalent sliding mode control: sliding mode hyperplane coefficient. Integral coefficient saturation function coefficients saturation function threshold Switching gain coefficient The simulation examines the stroke changes of each hydraulic cylinder 240 during the deployment process and the coordination and synchronization errors during deployment.

[0427] The multi-cylinder coordinated drive control method for a large-size scissor lift mechanism, considering deformation under gravity and load, proposed in this invention enables coordinated deployment under gravitational deformation fields. The multi-cylinder stroke trajectory during deployment is as follows: Figure 12 As shown, the synchronization error during unfolding is less than 10mm, as... Figure 13 As shown. However, without considering deformation under gravity, the driving load of the hydraulic cylinder 240 will increase, and the synchronization error during deployment can reach 28mm. Furthermore, due to mutual obstruction, the error fluctuation is significant, such as... Figure 14 As shown.

[0428] The present invention also provides a control system for a large-size extension mechanism based on a multi-cylinder drive, specifically implemented using the above-described unfolding mechanism.

[0429] In one implementation, the control system controls the hydraulic system according to the following formula:

[0430]

[0431] In one implementation, a tracking controller is provided for each hydraulic cylinder 240, wherein the tracking control law of the tracking controller is as follows:

[0432]

[0433] It should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them; although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A control system for a large-size extension mechanism based on multi-cylinder drive, comprising a controller, a control circuit, and a large-size extension mechanism based on multi-cylinder drive, characterized in that: The large-size extension mechanism based on multi-cylinder drive includes multiple parallel frames, a scissor system, and mounting components. The multiple parallel frames are connected to the scissor system and can be extended and retracted under the action of the scissor system. Multiple mounting components are provided on each frame. The scissor lift system includes a slide bar, a slider, a horizontally deployable scissor lift mechanism, and a hydraulic cylinder. The horizontally deployable scissor lift mechanism comprises multiple series-connected secondary scissor lift units. Each secondary scissor lift unit includes four forks of equal length: a first fork, a second fork, a third fork, and a fourth fork. The first and second forks are intersected and hinged at the intersection to form a first hinge point. The third and fourth forks are also intersected and hinged at the intersection to form a second hinge point. The second end of the first fork is hinged to the first end of the fourth fork. The second end of the second fork is hinged to the first end of the third fork. The second end of the fourth fork is hinged to the first end of the first fork of an adjacent secondary scissor lift unit. The second end of the third fork is hinged to the first end of the second fork of an adjacent secondary scissor lift unit. In this configuration, the first end of the first fork of the first secondary scissor lift unit is hinged to the slide bar, and the first end of the second fork of the first secondary scissor lift unit is hinged to the slider; the slider can slide on the slide bar; each frame is connected to the second hinge point of the corresponding secondary scissor lift unit and can move with the displacement of the second hinge point; each secondary scissor lift unit is provided with a hydraulic cylinder, wherein the first end of the hydraulic cylinder is connected to one of the first fork and the second fork, and the other end of the hydraulic cylinder is connected to one of the third fork and the fourth fork; at least one of the hydraulic cylinders is arranged at an angle; wherein: The first end of the hydraulic cylinder is connected between the first end of the second fork and the first hinge point; the second end of the hydraulic cylinder is connected between the second end of the third fork and the second hinge point, with the first end of the hydraulic cylinder being closer to the first end of the second fork and the second end of the hydraulic cylinder being closer to the second hinge point. Alternatively, the first end of the hydraulic cylinder is connected between the first end of the first fork and the first hinge point; the second end of the hydraulic cylinder is connected between the second end of the fourth fork and the second hinge point, with the first end of the hydraulic cylinder being closer to the first end of the first fork and the second end of the hydraulic cylinder being closer to the second hinge point. The multiple series-connected two-stage scissor lift units are three in total, namely a first-stage scissor lift unit, a second-stage scissor lift unit, and a third-stage scissor lift unit; the hydraulic cylinder of the first-stage scissor lift unit is a first hydraulic cylinder, the hydraulic cylinder of the second-stage scissor lift unit is a second hydraulic cylinder, and the hydraulic cylinder of the third-stage scissor lift unit is a third hydraulic cylinder. The length variation of the first hydraulic cylinder during its working stroke is controlled according to the following formula: MN: The length variation of the second hydraulic cylinder during its working stroke is controlled according to the following formula: PQ: The length variation of the third hydraulic cylinder during its working stroke is controlled according to the following formula: RS: The parameters are explained below: Total length of scissor lift Fork length Distance from the left end of the hydraulic cylinder to the first hinge point of the secondary fork unit where the hydraulic cylinder is located Distance from the right end of the hydraulic cylinder to the second hinge point of the secondary fork unit where the hydraulic cylinder is located Hydraulic cylinder quality Single mount weight gravitational acceleration Forklift thickness Fork width Forklift material density Elastic modulus of fork frame material.

2. The control system for a large-size extension mechanism based on multi-cylinder drive according to claim 1, characterized in that: All of the hydraulic cylinders are arranged at an angle.

3. The control system for a large-size extension mechanism based on multi-cylinder drive as described in claim 1, characterized in that: The hydraulic cylinders of multiple series-connected secondary scissor lift units are arranged alternately. Starting from the secondary scissor lift unit closest to the slide bar end, the hydraulic cylinders of odd-numbered secondary scissor lift units are connected at both ends to the second and third forks, respectively; the hydraulic cylinders of even-numbered secondary scissor lift units are connected at both ends to the first and fourth forks, respectively.

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