A method for parameter calibration of a lifting mechanism

Abstract

The application discloses a kind of lifting mechanism parameter calibration methods, comprising the following steps: lifting mechanism is lifted and controlled, the control end position information of open loop system is collected, motor is driven ball screw to rotate by speed reducer, the distance between each fulcrum is changed by the lateral movement of the matching nut of ball screw;During the process of lifting mechanism ascending and descending, the angle of each connecting rod in connecting rod group and ground, the vector of each connecting rod group changed is recorded;According to the number of motor rotation, the ground clearance of roller butt joint surface is obtained, the height of lifting mechanism upper hinge point to roller butt joint surface and the ground clearance of lifting mechanism lower hinge point are established equation set to carry out compensation calculation, and the calibration parameter value is obtained, the present application can avoid the influence of assembly and parts machining precision, reduce dimensional error, greatly improve the precision of open loop control.

Description

Technical Field

[0001] This invention relates to the field of lifting mechanism technology, specifically to a method for calibrating lifting mechanism parameters. Background Technology

[0002] AMR / AGVs (Autonomous Mobile Robots / Automatic Guided Vehicles) typically require a lifting mechanism to perform tasks such as picking up, placing, and docking goods. A scissor lift mechanism can be used to raise and lower the AMR / AGV's top plate. Lifting mechanisms are used in roller AMR / AGVs, usually for docking with conveyor lines. Docking a roller AMR / AGV with a production line typically only requires using the lowest and highest lifting positions to transfer materials. When the heights of the docking conveyor lines are inconsistent, to achieve smoother transport, the AMR / AGV needs to be able to drive the lifting drive motor to stop at any height and provide more accurate feedback on the ground clearance of the current roller docking surface.

[0003] However, due to limitations in the machining precision of the lifting mechanism components and the continuous accumulation of dimensional errors, the open-loop control method described above often fails to obtain an accurate height relationship between the number of rotations of the drive motor and the roller mating surface. Closed-loop control, on the other hand, is more expensive and makes the system more complex. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for calibrating lifting mechanism parameters that can improve the open-loop control accuracy of the lifting mechanism.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for calibrating the parameters of a lifting mechanism, wherein the lifting mechanism is used in an AMR / AGV, the AMR / AGV is equipped with rollers, the lifting mechanism includes an open-loop system, the open-loop system includes a lifting top plate, a motor, and a ball screw, a reducer is installed under the lifting top plate, and the motor is driven by the ball screw through the reducer. The method for calibrating the parameters of the lifting mechanism includes the following steps:

[0007] The lifting mechanism is subjected to lifting and lowering control, and the control end position information of the open-loop system is collected. The control end position information includes the distance between each support point in the lifting mechanism linkage group and the distance between the upper hinge point and the lower hinge point of the lifting mechanism.

[0008] The motor drives the ball screw to rotate through the reducer, and the mating nut of the ball screw moves laterally to change the distance between each support point;

[0009] During the lifting mechanism's ascent and descent, record the angles between each link in the linkage group and the ground, as well as the vector formed by the changing links.

[0010] The height of the roller docking surface from the ground is obtained based on the number of motor rotations. A set of equations is established to compensate for the height of the upper hinge point of the lifting mechanism from the roller docking surface and the height of the lower hinge point of the lifting mechanism from the ground. The calibration parameter values ​​are obtained and recorded. When controlling the operation of the lifting mechanism, the transportation docking is more accurate.

[0011] Furthermore, the method also includes defining the fulcrum of each link in the linkage group, defining the fulcrum of each link as the first fulcrum, the second fulcrum, the third fulcrum, the fourth fulcrum, and the fifth fulcrum, denoted as Link1, Link2, Link3, and Link4, respectively, connecting the first fulcrum and the fifth fulcrum.

[0012] Furthermore, the first fulcrum is slidably connected to the lifting mechanism, the second fulcrum is fixed on the lifting mechanism, and the first, second, fourth, and fifth fulcrums are respectively connected to the third fulcrum. The third fulcrum is a hinge point, and the height of the lifting mechanism is adjusted through the third fulcrum.

[0013] Furthermore, the vector formed by the links is:

[0014] v_Linkx = [l x θ x ] T θ x ∈[0,π], where, l x Let θ be the length between the fulcrums of each link. x v_Linkx represents the angle between each link and the ground, and x is the vector formed by each link. The value of x ranges from 1 to 4. The length between the fulcrums of each link changes during the operation of the lifting mechanism. Therefore, the changes in length and direction are recorded by a vector.

[0015] Furthermore, the length of the connecting rod between the fourth and fifth fulcrums is:

[0016]

[0017] Where l0 is the initial length of Link4, N is the number of rotations of the motor, P is the lead of the ball screw, i is the reduction ratio of the reducer, and l4 is the length of the link between the fourth and fifth fulcrums.

[0018] Furthermore, the height between the upper hinge point and the lower hinge point of the lifting mechanism is calculated as follows:

[0019]

[0020] Where l1 is the length of Link1, and θ1 is the angle between Link3 and the ground.

[0021] Furthermore, the height of the roller mating surface above the ground is:

[0022] h = h0 + h1 + h x ;

[0023] Where h0 is the height of the lower hinge point of the lifting mechanism from the ground, h1 is the height of the upper hinge point of the lifting mechanism from the roller mating surface, and h is the height of the roller mating surface from the ground.

[0024] Furthermore, the calibration parameter values ​​are the height from the upper hinge point of the lifting mechanism to the roller mating surface and the height of the lower hinge point of the lifting mechanism above the ground. The compensation calculation for the calibration parameter values ​​is as follows:

[0025]

[0026] Where Δh is the combined compensation value of h1 and h0, and Δl is the length compensation value of l1.

[0027] Furthermore, the system of equations is established as follows:

[0028]

[0029] Where hc1 is the minimum height above the ground of the roller mating surface, and hc2 is the maximum height above the ground of the roller mating surface.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] This invention compensates for the height of the upper hinge point of the lifting mechanism from the roller mating surface and the height of the lower hinge point of the lifting mechanism from the ground by calculating and establishing a system of equations to obtain a comprehensive compensation value Δh and a length compensation value Δl. This avoids the influence of assembly and component machining accuracy, reduces dimensional errors, and obtains an accurate height relationship between the number of rotations of the drive motor and the roller mating surface through the above open-loop control method. This reduces the cost of closed-loop control. Without the need for precise measurement of components with errors, parameter calibration can be completed through the execution results of the mechanism, greatly improving the accuracy of open-loop control. For the open-loop control of the lifting mechanism, lower machining accuracy requirements are imposed on the lifting mechanism and AMR / AGV, reducing the machining cost of the AMR / AGV body. This paper only calibrates two imprecise values. When three or more values ​​need to be calibrated, a similar method can be used to establish a system of equations for calculation. Attached Figure Description

[0032] Figure 1 A flowchart of a method for calibrating lifting mechanism parameters;

[0033] Figure 2 A perspective view of an AMR equipped with roller attachments;

[0034] Figure 3 Left view of the AMR equipped with roller attachment;

[0035] Figure 4 This is a schematic diagram of the lifting mechanism structure;

[0036] Figure 5 for Figure 2 A cross-sectional view taken along section AA;

[0037] Figure 6 This is a schematic diagram showing the height of the roller docking surface from the ground.

[0038] Figure 7 This is a schematic diagram showing the height of the lower hinge point of the lifting mechanism from the ground.

[0039] Figure 8 This is a schematic diagram showing the height between the upper and lower hinge points of the lifting mechanism.

[0040] Figure 9 This is a schematic diagram of an open-loop system.

[0041] Among them, 1-lifting mechanism, 2-roller, 3-first fulcrum, 4-second fulcrum, 5-third fulcrum, 6-fourth fulcrum, 7-fifth fulcrum, 8-roller mating surface, 9-lifting top plate, 10-reducer, 11-motor, 12-ball screw. Detailed Implementation

[0042] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] It should be noted that the terms "comprising," "including," and "having," and any variations thereof, in the specification, claims, and accompanying drawings of this invention, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses. In the claims, specification, and accompanying drawings of this invention, relational terms such as "first" and "second" are used merely to distinguish one entity / operation / object from another entity / operation / object, and do not necessarily require or imply any such actual relationship or order between these entities / operations / objects.

[0045] like Figure 1 , Figure 2 and Figure 9 As shown, a method for calibrating the parameters of a lifting mechanism 1 is disclosed. The lifting mechanism 1 is applied in an AMR / AGV, which is equipped with a roller 2. The lifting mechanism 1 includes an open-loop system, which includes a lifting top plate 9, a motor 11, and a ball screw 12. A reducer 10 is installed under the lifting top plate 9. The motor 11 is connected to the ball screw 12 via the reducer 10. The method for calibrating the parameters of the lifting mechanism 1 includes the following steps: performing lifting control on the lifting mechanism 1; collecting the control end position information of the open-loop system, wherein the control end position information includes the distance between each support point in the lifting mechanism linkage group and the distance between the upper hinge point and the lower hinge point of the lifting mechanism 1; the motor 11 is connected to the ball screw 12 via the reducer 10. 0 drives the ball screw 12 to rotate, and the mating nut of the ball screw 12 moves laterally to change the distance between each support point; during the rising and falling process of the lifting mechanism 1, the angle between each link in the linkage group and the ground, and the vector formed by the changing links are recorded; the height of the roller docking surface 8 above the ground is obtained according to the number of rotations of the motor 11, and a set of equations is established to compensate for the height from the upper hinge point of the lifting mechanism 1 to the roller docking surface 8 and the height of the lower hinge point of the lifting mechanism 1 above the ground, and the calibration parameter values ​​are obtained. The obtained calibration parameter values ​​are recorded, and when the lifting mechanism 1 is controlled to operate, the transportation docking is more accurate and the conveying is more stable. The AMR / AGV can drive the lifting mechanism 1 to stop at any height and provide feedback on the current more accurate height of the roller docking surface 8 above the ground.

[0046] like Figure 3As shown, in one embodiment, the method further includes defining the fulcrum of each link in the linkage group. The fulcrum of each link is defined as first fulcrum 3, second fulcrum 4, third fulcrum 5, fourth fulcrum 6, and fifth fulcrum 7. The length between first fulcrum 3 and second fulcrum 4 is denoted as Link1, the link between first fulcrum 3 and fifth fulcrum 7 is denoted as Link2, the link between second fulcrum 4 and fourth fulcrum 6 is denoted as Link3, and the link between fourth fulcrum 6 and fifth fulcrum 7 is denoted as Link4. First fulcrum 3 is slidably connected to lifting mechanism 1, second fulcrum 4 is fixed on lifting mechanism 1, and first fulcrum 3, second fulcrum 4, fourth fulcrum 6, and fifth fulcrum 7 are respectively connected to third fulcrum 5. Third fulcrum 5 is a hinge point, and the height of lifting mechanism 1 is adjusted through third fulcrum 5. The fulcrums cooperate, and when first fulcrum 3 moves, the distance between first fulcrum 3 and second fulcrum 4 changes.

[0047] The vector formed by the links is:

[0048] v_Linkx = [l x θ x ] T θ x ∈[0,π], where, where, l x Let θ be the length between the fulcrums of each link. x v_Linkx is the angle between each link and the ground, and x is the vector formed by each link. The value of x ranges from 1 to 4. The length between the fulcrums of each link changes when the lifting mechanism 1 is in operation. Therefore, the changes in length and direction are recorded by vector.

[0049] The length of the link between the fourth fulcrum 6 and the fifth fulcrum 7 is:

[0050]

[0051] Where l0 is the initial length of Link4, N is the number of rotations of motor 11, P is the lead of ball screw 12, i is the reduction ratio of reducer 10, and l4 is the length of the link between the fourth and fifth fulcrums.

[0052] The height between the upper and lower hinge points of lifting mechanism 1 is calculated as follows:

[0053]

[0054] Where l1 is Link1 and θ1 is the angle between Link3 and the ground. During the operation of lifting mechanism 1, the length of Link1 is unknown. In order to improve the accuracy of l1, compensation calculations are required for l1. for Inverse cosine function.

[0055] like Figure 5 and Figure 6 As shown, the height of the roller mating surface 8 above the ground is:

[0056] h = h0 + h1 + h x ;

[0057] Where h0 is the height of the lower hinge point of the lifting mechanism 1 from the ground, h1 is the height of the upper hinge point of the lifting mechanism 1 from the roller mating surface 8, and h x The height between the upper and lower hinge points of the lifting mechanism 1 is given. As the position of the hinge points changes, h0 and h1 will also change, but the total value of the height h of the roller mating surface 8 above the ground remains unchanged.

[0058] like Figure 7 and Figure 8 As shown, the calibration parameter values ​​are the height from the upper hinge point of the lifting mechanism 1 to the roller mating surface 8 and the height of the lower hinge point of the lifting mechanism 1 from the ground. The compensation calculation for the calibration parameter values ​​is as follows:

[0059]

[0060] Where Δh is the combined compensation value of h1 and h0, and Δl is the length compensation value of l1.

[0061] The system of equations is established as follows:

[0062]

[0063] Where hc1 is the minimum height above the ground of the roller mating surface 8 and hc2 is the maximum height above the ground of the roller mating surface 8, equations are established to obtain the precise values ​​of Δh and Δl, thereby calculating the minimum height above the ground of the roller mating surface 8 and the maximum height above the ground of the roller mating surface 8, improving the open-loop control accuracy. In this embodiment, only two imprecise values ​​are calibrated. When three or more values ​​need to be calibrated, a similar method can be used to establish a system of equations to calculate the values.

[0064] It should be noted that the above specific embodiments are merely preferred embodiments of the present invention and the technical principles applied thereunder. Within the scope of the technology disclosed in the present invention, any changes, modifications, substitutions, combinations, or simplifications made by those skilled in the art without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be covered within the protection scope of the present invention.

Claims

1. A method for calibrating parameters of a lifting mechanism, wherein the lifting mechanism is used in an AMR / AGV, the AMR / AGV is equipped with rollers, the lifting mechanism includes an open-loop system, the open-loop system includes a lifting top plate, a motor, and a ball screw, a reducer is installed under the lifting top plate, and the motor is connected to the ball screw via the reducer, characterized in that... The method for calibrating the lifting mechanism parameters includes the following steps: The lifting mechanism is subjected to lifting and lowering control, and the control end position information of the open-loop system is collected. The control end position information includes the distance between each support point in the lifting mechanism linkage group and the distance between the upper hinge point and the lower hinge point of the lifting mechanism. The motor drives the ball screw to rotate through the reducer, and the mating nut of the ball screw moves laterally to change the distance between each support point; During the lifting mechanism's ascent and descent, record the angles between each link in the linkage group and the ground, as well as the vector formed by the changing links. The height of the roller mating surface above the ground is obtained based on the number of motor rotations. A set of equations is established to calculate the height from the upper hinge point of the lifting mechanism to the roller mating surface and the height of the lower hinge point of the lifting mechanism above the ground, and the calibration parameter values ​​are obtained.

2. The method for calibrating lifting mechanism parameters according to claim 1, characterized in that: The method further includes defining the fulcrum of each link in the linkage group, defining the fulcrum of each link as the first fulcrum, the second fulcrum, the third fulcrum, the fourth fulcrum, and the fifth fulcrum, denoted as Link1, Link2, Link3, and Link4, respectively, connecting the first fulcrum and the second fulcrum, the link between the first fulcrum and the fifth fulcrum, and Link4, respectively.

3. The method for calibrating lifting mechanism parameters according to claim 2, characterized in that: The first fulcrum is slidably connected to the lifting mechanism, the second fulcrum is fixed on the lifting mechanism, and the first, second, fourth, and fifth fulcrums are respectively connected to the third fulcrum.

4. The method for calibrating lifting mechanism parameters according to claim 3, characterized in that: The vector formed by the links is: v_Linkx=[l x i x ] T ,the x ∈[0,π]; Among them, l x Let θ be the length between the fulcrums of each link. x v_Linkx is the angle between each link and the ground, and x is the vector formed by the links, with x ranging from 1 to 4.

5. The method for calibrating lifting mechanism parameters according to claim 4, characterized in that: The length of the connecting rod between the fourth and fifth fulcrums is: Where l0 is the initial length of Link4, N is the number of rotations of the motor, P is the lead of the ball screw, i is the reduction ratio of the reducer, and l4 is the length of the link between the fourth and fifth fulcrums.

6. The method for calibrating lifting mechanism parameters according to claim 5, characterized in that: The distance between the upper hinge point and the lower hinge point of the lifting mechanism is calculated as follows: Where l1 is the length of Link1, θ1 is the angle between Link3 and the ground, and h x This is the distance between the upper and lower hinge points of the lifting mechanism.

7. The method for calibrating lifting mechanism parameters according to claim 6, characterized in that: The height of the roller docking surface above the ground is: h=h0+h1+h x ; Where h0 is the height of the lower hinge point of the lifting mechanism from the ground, h1 is the height of the upper hinge point of the lifting mechanism from the roller mating surface, and h is the height of the roller mating surface from the ground.

8. The method for calibrating lifting mechanism parameters according to claim 7, characterized in that: The calibration parameter values ​​are the height from the upper hinge point of the lifting mechanism to the roller mating surface and the height of the lower hinge point of the lifting mechanism above the ground. The compensation calculation for the calibration parameter values ​​is as follows: Where Δh is the combined compensation value of h1 and h0, and Δl is the length compensation value of l1.

9. The method for calibrating lifting mechanism parameters according to claim 8, characterized in that: The system of equations is established as follows: Where hc1 is the minimum height above the ground of the roller mating surface, and hc2 is the maximum height above the ground of the roller mating surface.

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