Hydraulic cylinder telescopic length prediction method and system for crane tip positioning

Abstract

The present application relates to the technical field of lifting machine, especially to a hydraulic cylinder telescopic length prediction method and system for end positioning of a lifting machine, comprising constructing a kinematics model of the lifting machine, defining the position and motion parameters of each joint of the lifting machine; calculating the pose matrix between adjacent link members by using homogeneous transformation, and calculating the transformation matrix from the working platform coordinate system to the base coordinate system of the lifting machine according to the pose matrix between adjacent link members; obtaining the geometric relationship between the end position of the lifting machine and the joint rotation angle in the base coordinate system according to the transformation matrix; obtaining the joint rotation angle by inverse kinematics calculation, and predicting the telescopic length of the hydraulic cylinder through the joint rotation angle; inputting the coordinates of the target to be tracked into the controller, adjusting the telescopic length of the hydraulic cylinder, and moving the working platform to the position of the target to be tracked. The present application solves the problem of inaccurate spatial positioning caused by the existing method, i.e. the actual lifting height may deviate from the expected target due to the hysteresis and steady-state error.

Description

Technical Field

[0001] This invention relates to the field of lift technology, and in particular to a method and system for predicting the extension and retraction of a hydraulic cylinder for end-positioning of a lift. Background Technology

[0002] Lifts use mechanical principles for lifting and lowering, and are usually quite fast. They can quickly lift heavy objects to a suitable height. Compared to manual handling, mechanical lifts are much more efficient, saving a lot of time and labor costs. Lifts are relatively simple to operate, requiring only a few basic operating skills.

[0003] Publication No. CN117069022A: A method and device for controlling the safe operating range of a high-altitude work vehicle with variable boom amplitude. The method requires acquiring the outrigger extension amplitude, boom luffing angle, chassis tilt angle, and current boom extension / retraction amount of the lift vehicle. Based on the outrigger extension amplitude, boom luffing angle, and chassis tilt angle, the required boom extension / retraction amount is obtained. This method for lift end-positioning has the following drawbacks:

[0004] 1. Because the length of the lifting hydraulic cylinder cannot be accurately predicted, operators need to make constant adjustments and calibrations, which increases the complexity and difficulty of operation.

[0005] 2. Using a vision system to determine the position of the work platform requires a large amount of data for effective model training, which places a high demand on resources and increases the operating cost of the lift.

[0006] 3. During operation, the lifting machine needs to consider multiple parameters, such as boom luffing angle and tilt angle. Controlling these parameters requires tedious manual adjustment, especially when performing complex tasks. Summary of the Invention

[0007] To address the shortcomings of existing methods, this invention solves the problems of inaccurate spatial positioning caused by hysteresis and steady-state error, which may lead to deviations between the actual lifting height and the expected target; and the inability to accurately predict the length of the lifting hydraulic cylinder, which requires fine-tuning by the operator, resulting in complex operation and high work difficulty.

[0008] The technical solution adopted in this invention is: a method for predicting the extension and retraction of a hydraulic cylinder for positioning the end of a lift, comprising the following steps:

[0009] Step 1: Construct the kinematic model of the lift and define the position and motion parameters of each joint of the lift;

[0010] In a preferred embodiment of the present invention, the lift includes four turntables, a base, and three hydraulic cylinders.

[0011] Step 2: Calculate the pose matrix between adjacent links using the homogeneous transformation matrix, and calculate the transformation matrix from the lifting platform coordinate system to the base coordinate system based on the pose matrix between adjacent links.

[0012] In a preferred embodiment of the present invention, the formula for the transformation matrix from the lift platform coordinate system to the base coordinate system is:

[0013]

[0014] In the formula, s0 = sinθ0; c0 = cosθ0; c1 = cosθ1; s 12 =sin(θ1+θ2); c 12 =cos(θ1+θ2); s 123 =sin(θ1+θ2+θ3); c 123 =cos(θ1+θ2+θ3); l0 is the length of the first turntable link; l1 is the length of the second turntable link; l2 is the length of the third turntable link; l3 is the length of the fourth turntable link; θ0 is the initial rotation angle of the base; θ1 is the angle between the second turntable link and the x1 axis of the local coordinate system; θ2 is the angle between the third turntable link and the x2 axis of the local coordinate system; θ3 is the angle between the fourth turntable link and the x3 axis of the local coordinate system.

[0015] In a preferred embodiment of the present invention, the angle θ3 between the fourth turntable member and the x3 axis of the local coordinate system is 0.

[0016] Step 3: Obtain the geometric relationship between the lift end position and the joint rotation angle in the base coordinate system based on the transformation matrix;

[0017] In a preferred embodiment of the present invention, the formula for the geometric relationship is:

[0018]

[0019] Where, x d ,y d ,z d d0 represents the coordinates of the end position of the lift, and d0 represents the offset of the connecting perpendicular.

[0020] Step 4: Obtain the joint angle through inverse kinematics calculation, and predict the extension and retraction of the hydraulic cylinder based on the joint angle;

[0021] In a preferred embodiment of the present invention, the formula for calculating the joint rotation angle using inverse kinematics is as follows:

[0022]

[0023] Where σ1=x d l1-l0l1+zd l1-d0l1;σ2=(x d -l0) 2 +(z d -d0) 2 -(l2+l3) 2 .

[0024] In a preferred embodiment of the present invention, the formula for the extension and retraction of the hydraulic cylinder is:

[0025]

[0026] Where, α1=2(l1d0-l1x) d -l1z d ),

[0027]

[0028] l CO1 Let l be the length from point C to point O1 on the first turntable. BO1 Let l be the length from point B to point O1 of the first hydraulic cylinder. AC Let l be the length from point A to point C on the first turntable. FO2 The length from point F to point O2 of the second hydraulic cylinder, l EO2 The length from point E to point O2 of the second hydraulic cylinder.

[0029] Step 5: Input the coordinates of the target to be tracked into the controller, adjust the extension and retraction of the hydraulic cylinder, and move the work platform to the position of the target to be tracked.

[0030] As a preferred embodiment of the present invention, a hydraulic cylinder extension / retraction prediction system for end-of-lift positioning includes: a memory for storing instructions executable by a processor; and a processor for executing the instructions to implement a hydraulic cylinder extension / retraction prediction method for end-of-lift positioning.

[0031] In a preferred embodiment of the present invention, a computer-readable medium storing computer program code implements a method for predicting the extension and retraction of a hydraulic cylinder for positioning the end of a lift when executed by a processor.

[0032] The beneficial effects of this invention are:

[0033] 1. Improve spatial positioning accuracy: By predicting the length of the lifting hydraulic cylinder, the lift can achieve more precise spatial positioning;

[0034] 2. Simplified operation process: By predicting the length of the lifting hydraulic cylinder, operators no longer need to manually adjust and calibrate the lifting action, which simplifies the operation process, reduces the workload of operators, reduces the risk of operational errors, and improves work efficiency.

[0035] 3. Reduced operation and maintenance costs: More accurate positioning of the lifting space can reduce damage to goods or incorrect placement caused by errors, thereby reducing operation and maintenance costs;

[0036] 4. Improved safety: Precise positioning of the lifting space can reduce the risk of accidents involving the lifting machine and ensure the safety of staff and the surrounding environment; at the same time, operators do not need to make frequent manual adjustments, which also reduces potential safety hazards caused by human factors. Attached Figure Description

[0037] Figure 1 This is a flowchart of the hydraulic cylinder extension and retraction prediction method for end-positioning of a lift according to the present invention;

[0038] Figure 2 This is a schematic diagram of an existing lift structure;

[0039] Figure 3 This invention compares the x-axis coordinates of the target to be tracked, the actual value of the extension and retraction of the first hydraulic cylinder, and the predicted value.

[0040] Figure 4 This invention compares the x-axis coordinates of the target to be tracked and the actual and predicted values ​​of the extension and retraction of the second hydraulic cylinder.

[0041] Figure 5 This invention compares the z-axis coordinate of the target to be tracked, the actual value of the extension and retraction of the first hydraulic cylinder, and the predicted value.

[0042] Figure 6 This invention compares the z-axis coordinate of the target to be tracked and the actual and predicted values ​​of the extension and retraction of the second hydraulic cylinder.

[0043] Figure 2 In the diagram, 0 is the base; 1 is the first turntable link; 2 is the second turntable link; 3 is the third turntable link; 4 is the fourth turntable link; 5 is the first hydraulic cylinder; 6 is the second hydraulic cylinder; 7 is the third hydraulic cylinder; and 8 is the working platform. Detailed Implementation

[0044] The present invention will be further described below with reference to the accompanying drawings and embodiments. The drawings are simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.

[0045] The method for predicting the extension and retraction of hydraulic cylinders used for end-positioning of a lift includes the following steps:

[0046] like Figure 1 Step 1: Establish the kinematic model of the lift and define the position and motion parameters of each joint of the lift.

[0047] like Figure 2 Define a three-axis coordinate system of x, y, and z. Establish a local coordinate system at the ends of the base and the turntable. The x-axis is the direction of the main axis of the turntable, which represents the left and right displacement of the lift. Since the base is fixed, the y-axis represents rotation. The rotation of the base is not considered, so the y-axis is ignored. The z-axis is perpendicular to the xy plane, which represents the lifting displacement of the lift.

[0048] The lift includes a base 0, a first turntable link 1, a second turntable link 2, a third turntable link 3, and a fourth turntable link 4, a first hydraulic cylinder 5, a second hydraulic cylinder 6, a third hydraulic cylinder 7, and a working platform 8. The turntable and base include five endpoints O0-O4; where O0 is the vertex of base 0, with local coordinates (x0, z0); O1 is the endpoint of the first turntable link 1, with local coordinates (x1, z1); O2 is the endpoint of the second turntable link 2, with local coordinates (x0, z0); The coordinates are (x2, z2); O3 is the endpoint of the third turntable link 3, with local coordinates (x3, z3); ​​O4 is the endpoint of the fourth turntable link 4, with local coordinates (x4, z4); the length l0 of the first turntable link 1 represents the distance between O0 and O1; the length l1 of the second turntable link 2 represents the length of O1 and O2; the length l2 of the third turntable link 3 represents the length of O2 and O3; and the length l3 of the fourth turntable link 4 represents the length of O3 and O4.

[0049] The angle between the turntable link and the x-axis of the local coordinate system is the joint angle; where θ0 is the initial rotation angle of the base 0, that is, the base 0 rotates from the initial position to the working position; θ1 is the angle between the second turntable link 2 and the x1 axis of the local coordinate system; θ2 is the angle between the third turntable link 3 and the x2 axis of the local coordinate system; and θ3 is the angle between the fourth turntable link 4 and the x3 axis of the local coordinate system.

[0050] Establish the pose matrix, and based on the set joint angles and link lengths, use robotics principles and homogeneous transformation rules to calculate the pose matrix between each adjacent link. Multiplying the pose matrices between all adjacent links yields the transformation matrix from the entire lifting platform coordinate system O4 to the base coordinate system O0; the formula for the pose matrix between adjacent links is:

[0051]

[0052]

[0053]

[0054]

[0055] The formula for the transformation matrix is:

[0056]

[0057] In the formula, This is the transformation matrix from the local coordinate system O4 to O0; This is the transformation matrix from the local coordinate system O1 to O0; This is the transformation matrix from the local coordinate system O2 to O1; This is the transformation matrix from the local coordinate system O3 to O2; Here are the transformation matrices from local coordinate system O4 to O3; s0 = sinθ0; c0 = cosθ0; c1 = cosθ1; s 12 =sin(θ1+θ2); c 12 =cos(θ1+θ2); s 123 =sin(θ1+θ2+θ3); c 123 =cos(θ1+θ2+θ3); d0 is the distance between the two axes from x0 to x1; transformation matrix Used to describe the positional changes of the working platform relative to the base during the movement of the lift.

[0058] Specifically, the transformation matrix operation rules are as follows: a transformation is defined as a motion in space. Given the coordinates of a point in a rectangular coordinate system, the coordinates of that point in another rectangular coordinate system are obtained through homogeneous coordinate transformation. Transformations are divided into the following forms: pure translation, pure rotation, and a combination of translation and rotation. The pose matrix is ​​a mathematical tool for describing the rotational posture of an object in a three-dimensional coordinate system. It is a matrix composed of three mutually perpendicular unit vectors, representing the rotation of the object on the x-axis, y-axis, and z-axis of the coordinate system, respectively. In robotics, it is a mathematical tool for describing the rotation of a robot in three-dimensional space.

[0059] Step 2: Convert the target position of work platform 8 into the length of the lifting hydraulic cylinder;

[0060] This includes: Prediction algorithm transmission: Based on work requirements, the target position coordinates of the lift are given, and the target position coordinates are transmitted to the prediction algorithm;

[0061] Parameter passing: Initialize l1, l2, and other relevant parameters based on the provided lift kinematic parameters;

[0062] Predicted extension / retraction: Based on the established kinematic model, inverse kinematics calculations are used to convert the target position into the length of the first and second stage variable-amplitude hydraulic cylinders, thus obtaining the predicted extension / retraction of the hydraulic cylinder.

[0063] Considering the steady-state error of the hydraulic control system, optimization and correction are carried out. Based on accumulated practical operating experience, a feedback control algorithm is used to dynamically adjust the predicted hydraulic cylinder extension and retraction amount. This aims to ensure that the lifting platform tracks the target position with high precision, thereby meeting the work requirements, effectively dealing with the characteristics of the hydraulic control system, and using the feedback control algorithm to enable the lifting platform to accurately track and position the target position while considering steady-state error.

[0064] According to formula (5), the geometric relationship between the end position of the lift and the joint rotation angle in the base coordinate system is as follows:

[0065]

[0066] Where, x d ,y d ,z d d0 represents the coordinates of the end position of the lift, which is the coordinates of the target to be tracked. d0 is the offset of the connecting perpendicular line, which is the vertical distance from the x0 axis to the x1 axis.

[0067] Based on (6), inverse kinematics calculations are performed. Using the kinematic parameters of the lift, the lengths l1 of the second turntable link 2 and l2 of the third turntable link 3 are initialized. In trajectory control, the first hydraulic cylinder 5 and the second hydraulic cylinder 6 are the main variables, and the third hydraulic cylinder 7 is the secondary variable. The third hydraulic cylinder 7 is set to its maximum extension and locked. Figure 2 l in GH The maximum value; l GH When θ3 is at its maximum value, θ3 = 0. Substituting θ3 = 0 into equation (6) yields the joint rotation angles θ1 and θ2, as shown in the formula:

[0068]

[0069] Where σ1=x d l1-l0l1+z d l1-d0l1;σ2=(x d -l0) 2 +(z d -d0) 2 -(l2+l3) 2 .

[0070] The extension / retraction amount l of the first hydraulic cylinder 5 is calculated based on θ1 and θ2. AB The extension / retraction amount of the second hydraulic cylinder 6 EF The formula is:

[0071]

[0072] Where, α1=2(l1d0-l1x) d -l1z d ),

[0073]

[0074] The first turntable has three endpoints A, C, and O1. Point A is also one endpoint of the first hydraulic cylinder 5; the length from endpoint A to C is l. AC , representing the length of AC; the first hydraulic cylinder 5 has endpoints A and B; the second hydraulic cylinder 6 has endpoints E and F; the third hydraulic cylinder 7 has endpoints G and H; the length l from endpoint B of the first hydraulic cylinder 5 to point O1. BO1 , representing the length of BO1; the length l from point C to point O1 on the first turntable. CO1 , representing the length of CO1; the length l from point E to point O2 of the secondary hydraulic cylinder. EO2 , indicating the length of EO2; the length l from the end point F of the second hydraulic cylinder 6 to point O2. FO2 , indicating the length of FO2.

[0075] This invention only requires providing the coordinates of the target to be tracked to obtain l AB and l EF It allows for easy scaling without requiring multiple parameters or joint angles to be entered separately, reducing the possibility of input errors and improving ease of use. If the system needs to exchange data with other devices or software, using the standard xyz coordinate representation makes integration and interaction easier.

[0076] Lift control: The output results are sent to the controller to control the lift.

[0077] The output is sent to the controller. Specifically, the hydraulic cylinder extension and retraction amount obtained by the prediction method is transmitted to the hydraulic controller. The hydraulic system adjusts the length of the first hydraulic cylinder 5 and the second hydraulic cylinder 6 so that the working platform 8 runs along the predetermined trajectory. During the operation, the position and attitude of the working platform 8 are monitored in real time. The extension and retraction amount of the two hydraulic cylinders obtained by the prediction algorithm is controlled in real time. The feedback control system continuously corrects the extension and retraction amount of the hydraulic cylinders so that the working platform 8 can achieve accurate trajectory tracking.

[0078] Table 1. Kinematic parameters of the lifting machine (mm)

[0079]

[0080]

[0081] Substituting the kinematic parameters from Table 1 and the coordinates of the target to be tracked into equation (7), the extension length l is calculated using MATLAB simulation. AB and l EF ;

[0082] Table 2 Predicted Expansion / Contraction Length (mm)

[0083]

[0084] like Figure 3-6 As shown, a total of 10 rows of data were collected, and the method of this invention was used to predict the l based on the actual coordinates of the target to be tracked. AB and l EF The value will predict l AB and l EF The value is input to the controller to obtain the predicted coordinates of the end of the lift. It can be seen that the predicted coordinates are basically consistent with the measured values, indicating that the method of the present invention has a certain degree of accuracy.

[0085] In summary, the advantages of this invention are that it improves the accuracy of spatial positioning at the end of the lifting machine, reduces errors in the motion control process, and allows operators to more precisely control the lifting action of the lifting machine by predicting the length of the lifting hydraulic cylinder, ensuring the safe lifting and placement of goods. This invention has great application potential and can improve work efficiency and safety in the lifting machine industry.

[0086] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for predicting the extension and retraction of a hydraulic cylinder used for end-positioning of a lifting machine, characterized in that, Includes the following steps: Step 1: Construct the kinematic model of the lift and define the position and motion parameters of each joint of the lift; The lift includes a base, a first turntable link, a second turntable link, a third turntable link and a fourth turntable link, a first hydraulic cylinder, a second hydraulic cylinder, a third hydraulic cylinder and a working platform. The turntable and the base include five endpoints O0-O4. Where O0 is the vertex of the base, and its local coordinates are ( x 0, z 0); O1 is the endpoint of the first turntable member, and its local coordinates are ( x 1, z 1); O2 is the endpoint of the second turntable member, and its local coordinates are ( x 2, z 2); O3 is the endpoint of the third turntable member, and its local coordinates are ( x 3, z 3); O4 is the endpoint of the fourth turntable member, and its local coordinates are ( x 4, z 4) The length of the first turntable member ,express The distance; the length of the second turntable link ,express Length; length of the third turntable link ,express Length; length of the fourth turntable link ,express Length; Turntable members and local coordinate system x The angle between the axes is the joint angle; where, This is the initial rotation angle of the base; For the second turntable member and the local coordinate system x The included angle of axis 1; For the third turntable members and the local coordinate system x The included angle between the two axes; For the fourth turntable member and the local coordinate system x The included angle of the three axes; Step 2: Calculate the pose matrix between adjacent links using homogeneous transformation. The pose matrix between adjacent links includes: local coordinate system. arrive Transformation matrix Local coordinate system arrive Transformation matrix Local coordinate system arrive Transformation matrix Local coordinate system arrive Transformation matrix ; the pose matrix between adjacent links , , , Multiplying them yields the transformation matrix from the lift platform coordinate system to the base coordinate system. ; Step 3: The geometric relationship between the lift end position and the joint rotation angle in the base coordinate system is... The values ​​in the first row, fourth column, the second row, fourth column, and the third row, fourth column are used as the coordinates of the lift's end position (x). d ,y d ,z d The value of ); The formula for the transformation matrix from the lift platform coordinate system to the base coordinate system is: = = （5） wherein, =sin ; =cos ; =cos ; =sin ; =cos ; =sin ; =cos ; The formula for the geometric relationship is: （6） Where, x d ,y d ,z d The coordinates of the end position of the lift are as follows: The offset for connecting the common perpendicular; Step 4: For (x) d ,y d ,z d Joint rotation angles are obtained by performing inverse kinematic calculations. and ,pass and Predict the extension / retraction amount l of the first hydraulic cylinder AB The extension / retraction amount of the second hydraulic cylinder l EF ; The formula for the extension and retraction of a hydraulic cylinder is: （8） in, , + , l CO1 Let l be the length from point C to point O1 on the first turntable. BO1 Let l be the length from point B to point O1 of the first hydraulic cylinder. AC Let l be the length from point A to point C on the first turntable. FO2 The length from point F to point O2 of the second hydraulic cylinder, l EO2 The length from point E to point O2 of the second hydraulic cylinder; Step 5: Input the coordinates of the target to be tracked into the controller, adjust the extension and retraction of the hydraulic cylinder, and move the work platform to the position of the target to be tracked.

2. The method for predicting the extension and retraction of a hydraulic cylinder for end-positioning of a lift according to claim 1, characterized in that, The formula for calculating joint rotation angles using inverse kinematics is: （7） in, = - + - = ( - ) +( - ) -( + ) .

3. The method for predicting the extension and retraction of a hydraulic cylinder for end-positioning of a lift according to claim 1, characterized in that, The lift consists of four turntables, a base, and three hydraulic cylinders.

4. The method for predicting the extension and retraction of a hydraulic cylinder for end-positioning of a lift according to claim 1, characterized in that, Fourth turntable members and local coordinate system x Angle between the three axes =0.

5. A hydraulic cylinder extension / retraction prediction system for end-positioning of a lifting machine, characterized in that, include: Memory is used to store instructions that can be executed by the processor; A processor for executing instructions to implement the method for predicting the extension and retraction of a hydraulic cylinder for end-positioning of a lift as described in any one of claims 1-4.

6. A computer-readable medium storing computer program code, characterized in that, The computer program code, when executed by a processor, implements the hydraulic cylinder extension / retraction prediction method for end-of-lift positioning as described in any one of claims 1-4.

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