Millimeter-level synchronous control method for multiple hydraulic control axes and lifting platform

Abstract

The present invention relates to a millimeter-level synchronous control method for multiple hydraulic control axes and a lifting platform, wherein the control method comprises the following steps: S1, placing cargo on the lifting platform, controlling the valve opening of the proportional valve corresponding to each hydraulic cylinder to be the same, and driving each hydraulic cylinder to first rise to a preset height; S2, obtaining the actual lifting height of each hydraulic cylinder, defining one of the hydraulic cylinders as a reference hydraulic cylinder, and calculating the pressure difference ratio between the other hydraulic cylinders and the reference hydraulic cylinder through the actual lifting heights of the other hydraulic cylinders and the actual lifting height of the reference hydraulic cylinder; S3, on the premise that the lifting preset heights of the other hydraulic cylinders and the reference hydraulic cylinder are the same, calculating the valve opening ratio of the other hydraulic cylinders and the reference hydraulic cylinder through the pressure difference ratio; S4, adjusting the valve opening of the proportional valve of the other hydraulic cylinders according to the valve opening ratio, and driving each hydraulic cylinder to continue rising to the target height.

Description

Technical Field

[0001] The present invention relates to the field of lifting platform control, and in particular to a millimeter-level synchronous control method for multiple hydraulic control axes and a lifting platform. Background Art

[0002] With the rapid development of the logistics industry, the volume of cargo transported continues to increase, and the requirements for loading and unloading efficiency are becoming increasingly higher. Traditional loading and unloading methods can no longer meet the needs of modern logistics. Therefore, loading is achieved through loading systems. A lifting platform is a system for automated loading of cargo. The cargo is placed on the lifting platform, and then the lifting platform rises to lift the cargo to a certain height to facilitate the cargo to enter the container.

[0003] During each lifting process, the lifting platform drives each leg up and down through the hydraulic cylinders, and the position of the cargo on the lifting platform, the weight of the cargo and other parameters are different, so the load pressure on each hydraulic cylinder is different. During the lifting process of the hydraulic cylinder, the heavier the load, the slower the lifting speed of the hydraulic cylinder. The automatic loading scene is changeable, and the cargo load fluctuates each time, with no load, full load, and overload, resulting in synchronous speed differences. The existing technology generally adopts PID control, that is, during the lifting process, the lifting height of each hydraulic cylinder is obtained, and the lifting speed is increased if the lifting height does not reach the expected height, and the lifting speed is reduced if the lifting height exceeds the expected height. Since there is a certain delay in PID control, the hydraulic cylinders of the lifting platform are prone to jumping back and forth between acceleration and deceleration, causing jitter in the lifting synchronization adjustment process of the lifting platform and the lifting heights of the hydraulic cylinders to be asynchronous.

[0004] The purpose of the present invention is to design a millimeter-level synchronous control method and a lifting platform for multiple hydraulic control axes in order to solve the problems existing in the prior art. Summary of the Invention

[0005] In response to the problems existing in the above-mentioned prior art, the present invention provides a millimeter-level synchronous control method for multiple hydraulically controlled axes and a lifting platform, which can effectively solve at least one problem existing in the above-mentioned prior art.

[0006] The technical solution of the present invention is:

[0007] A millimeter-level synchronous control method for multiple hydraulically controlled axes is used for a lifting platform. The lifting platform is provided with outriggers, each outrigger is lifted and lowered by a corresponding hydraulic cylinder, and the hydraulic cylinders are respectively connected to a hydraulic station via a proportional valve;

[0008] The control method comprises the following steps:

[0009] S1, placing cargo on the lifting platform, controlling the valve opening of the proportional valve corresponding to each hydraulic cylinder to be the same, controlling the hydraulic station to output hydraulic oil to the hydraulic cylinder through the proportional valve, and driving each hydraulic cylinder to first raise to a preset height;

[0010] S2, obtaining the actual lifting height of each hydraulic cylinder, defining one of the hydraulic cylinders as a reference hydraulic cylinder, and calculating the pressure difference ratios of the other hydraulic cylinders and the reference hydraulic cylinder based on the actual lifting heights of the other hydraulic cylinders and the actual lifting height of the reference hydraulic cylinder;

[0011] S3, on the premise that the other hydraulic cylinders and the reference hydraulic cylinder are raised to the same preset height, calculating the valve opening ratio of the other hydraulic cylinders and the reference hydraulic cylinder based on the pressure difference ratio;

[0012] S4, adjusting the valve openings of the proportional valves of other hydraulic cylinders according to the valve opening ratio, and driving each of the hydraulic cylinders to continue to rise to the target height.

[0013] Furthermore, defining one of the hydraulic cylinders as a reference hydraulic cylinder includes:

[0014] Select the hydraulic cylinder whose actual lifting height is closest to the preset height as the reference hydraulic cylinder.

[0015] Furthermore, calculating the pressure difference ratios of the other hydraulic cylinders and the reference hydraulic cylinder respectively based on the actual lifting heights of the other hydraulic cylinders and the actual lifting height of the reference hydraulic cylinder includes:

[0016] In the process of raising the preset height, the hydraulic oil flow rate flowing through the hydraulic cylinder is defined as Q. is the flow coefficient; is the valve opening area, is the pressure difference between the two ends of the hydraulic cylinder, is the density of the hydraulic oil, r is the radius of the hydraulic cylinder, and L is the actual lifting height of the hydraulic cylinder, then:

[0017] ;

[0018] Since the valve opening of the proportional valve corresponding to each hydraulic cylinder is the same, the pressure difference ratio is: , Where is the pressure difference at both ends of other hydraulic cylinders, Where is the pressure difference between the two ends of the reference hydraulic cylinder, is the radius of other hydraulic cylinders, is the radius of the base hydraulic cylinder, is the actual lifting height of other hydraulic cylinders, The actual lifting height of the reference hydraulic cylinder.

[0019] Furthermore, on the premise that the preset lifting heights of the other hydraulic cylinders and the reference hydraulic cylinder are the same, calculating the valve opening ratio of the other hydraulic cylinders and the reference hydraulic cylinder by using the pressure difference ratio includes:

[0020] according to ,get: ,in is the valve opening of the proportional valve of other hydraulic cylinders, The valve opening of the proportional valve of the reference hydraulic cylinder, The preset lifting height of other hydraulic cylinders, The preset lifting height of the reference hydraulic cylinder;

[0021] Since the other hydraulic cylinders and the reference hydraulic cylinder have the same preset lifting height, the valve opening ratio is obtained: .

[0022] Furthermore, driving each of the hydraulic cylinders to continue to rise to the target height includes:

[0023] The target height is divided into a lifting start section, a steady-state lifting section, and a lifting stop section, and each hydraulic cylinder is driven to rise to the height corresponding to the lifting start section, the steady-state lifting section, and the lifting stop section in sequence.

[0024] Furthermore, a microphone array is provided around the lifting platform, and the goods are placed on a pallet;

[0025] In step S1, after placing the cargo on the lifting platform, the following steps are performed:

[0026] The microphone array collects the sound generated during the lowering of the tray;

[0027] Identify whether the sound contains the sound characteristics of a damaged pallet, and if so, proceed to the next step;

[0028] Analyzing the coordinates of a damage sound source of the sound of the pallet being damaged;

[0029] In step S4, after adjusting the valve openings of the proportional valves of other hydraulic cylinders according to the valve opening ratio, the following steps are executed:

[0030] Obtaining or calculating the placement coordinates of the pallet;

[0031] The valve opening corresponding to the lifting start section and the steady-state lifting section of each hydraulic cylinder is adjusted according to the damage sound source coordinates and the placement coordinates.

[0032] Furthermore, obtaining or calculating the placement coordinates of the tray includes:

[0033] A camera is provided above the lifting platform, and the camera obtains an image of the lifting platform and obtains the placement coordinates of the pallet through image analysis.

[0034] Furthermore, adjusting the valve opening of each hydraulic cylinder in the lifting start-up section and the steady-state lifting section according to the damage sound source coordinates and the placement coordinates includes:

[0035] Obtaining a pointing direction from the placement coordinates to the coordinates of the damaged sound source;

[0036] Obtaining the hydraulic cylinder with the shortest distance to the pointing direction;

[0037] Reduce the valve opening of the hydraulic cylinder with the shortest distance to the pointing direction in the lifting start-up section, increase the valve opening of the hydraulic cylinder diagonally opposite the hydraulic cylinder with the shortest distance to the pointing direction in the lifting start-up section, increase the valve opening of the hydraulic cylinder with the shortest distance to the pointing direction in the steady-state lifting section, and reduce the valve opening of the hydraulic cylinder diagonally opposite the hydraulic cylinder with the shortest distance to the pointing direction in the steady-state lifting section.

[0038] Furthermore, a distance sensor is provided at the bottom of each support leg, and the distance sensor obtains the distance between the bottom of the support leg and the lifting platform to obtain the actual lifting height.

[0039] A lifting platform with millimeter-level synchronization of multiple hydraulically controlled axes is further provided, which implements the millimeter-level synchronization control method of multiple hydraulically controlled axes during operation.

[0040] Therefore, the present invention provides the following effects and / or advantages:

[0041] In the process of lifting multiple hydraulic cylinders, the present application first places the cargo and then raises it to a preset height. In the process of raising it to the preset height, the valve openings of the proportional valves are controlled to be the same, so that the pressure difference ratio and the valve opening ratio are calculated by assuming different conditions. The valve openings of the proportional valves of each hydraulic cylinder can be controlled according to the valve opening ratio, so that the lifting process of the hydraulic cylinders remains synchronized.

[0042] The present application identifies the placement coordinates and the coordinates of the damage sound source, thereby being able to intelligently adjust the valve openings of each hydraulic cylinder in the lifting start section and the steady-state lifting section during the process of controlling the lifting of multiple legs, and concentrate the lifting force of the lifting platform on the pallet toward the lower left position of the pallet. By concentrating the force on the undamaged position of the pallet, the pallet can be prevented from being squeezed, deformed, and damaged by the goods, and the initial impact force of the hydraulic cylinder on the damaged position of the pallet when it is started is reduced, thereby avoiding the expansion of cracks.

[0043] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description and the drawings.

[0044] It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 A schematic diagram of a flow chart provided for an embodiment of the present invention.

[0046] Figure 2 It is a schematic diagram of the state of the pointing direction from the placement coordinate to the damaged sound source coordinate.

[0047] Figure 3 Schematic diagram of experimental data of the present invention.

[0048] Figure 4 Schematic diagram of experimental data of the prior art. DETAILED DESCRIPTION

[0049] In order to facilitate understanding by those skilled in the art, the present invention is now described in further detail with reference to the following examples:

[0050] refer to Figure 1 A millimeter-level synchronous control method for multiple hydraulically controlled axes is provided for a lifting platform, wherein the lifting platform is provided with outriggers, each outrigger is lifted and lowered by a corresponding hydraulic cylinder, and the hydraulic cylinders are respectively connected to a hydraulic station through a proportional valve;

[0051] The control method comprises the following steps:

[0052] S1, placing cargo on the lifting platform, controlling the valve opening of the proportional valve corresponding to each hydraulic cylinder to be the same, controlling the hydraulic station to output hydraulic oil to the hydraulic cylinder through the proportional valve, and driving each hydraulic cylinder to first raise to a preset height;

[0053] In this embodiment, cargo is first placed on the lifting platform. During the lifting process, the unbalanced load imposed by the cargo on the lifting platform is determined, as is its weight. Therefore, all conditions of the lifting platform at this point are known. This embodiment performs subsequent calculations after the cargo is placed on the platform. Furthermore, in this step, each hydraulic cylinder is initially driven to a preset height, enabling the acquisition of various hydraulic cylinder parameters during the lifting process. This single calculation results in sufficient accuracy for subsequent lifting synchronization.

[0054] Specifically, the preset height is 5-50 mm. The hydraulic cylinders are connected to the hydraulic station via proportional valves. The hydraulic station controls each hydraulic cylinder independently, and the pressure received by each hydraulic cylinder does not affect each other. The valve opening of the proportional valve in this step is fixed and the same, and the opening can be any value between 50% and 80%.

[0055] S2, obtaining the actual lifting height of each hydraulic cylinder, defining one of the hydraulic cylinders as a reference hydraulic cylinder, and calculating the pressure difference ratios of the other hydraulic cylinders and the reference hydraulic cylinder based on the actual lifting heights of the other hydraulic cylinders and the actual lifting height of the reference hydraulic cylinder;

[0056] In step S1, the valve openings of each proportional valve are set to be identical and fixed. Due to the unbalanced load of cargo on the lift platform, the position and weight of the cargo will affect the load-bearing pressure of each hydraulic cylinder. The pressure differential is the difference between the oil inlet and outlet pressures of the hydraulic cylinder—that is, the difference between the oil pressure applied to the hydraulic station by the hydraulic cylinder and the pressure applied to the lift platform by the hydraulic station. The pressure differential ratio can be calculated by reverse engineering based on the actual lift height and the assumption that the valve openings of each proportional valve are identical.

[0057] S3, on the premise that the other hydraulic cylinders and the reference hydraulic cylinder are raised to the same preset height, calculating the valve opening ratio of the other hydraulic cylinders and the reference hydraulic cylinder based on the pressure difference ratio;

[0058] In this step, the valve opening ratio can be adjusted according to the pressure difference ratio between the two hydraulic cylinders.

[0059] S4, adjusting the valve openings of the proportional valves of other hydraulic cylinders according to the valve opening ratio, and driving each of the hydraulic cylinders to continue to rise to the target height.

[0060] In this step, based on the preset height already raised in step S1, the hydraulic cylinder is continued to be controlled to rise, so as to reach the target height.

[0061] Furthermore, defining one of the hydraulic cylinders as a reference hydraulic cylinder includes:

[0062] Select the hydraulic cylinder whose actual lifting height is closest to the preset height as the reference hydraulic cylinder.

[0063] In this step, the hydraulic cylinder whose actual lifting height is closest to the preset height is the hydraulic cylinder closest to the ideal state, so this hydraulic cylinder is selected as the basic hydraulic cylinder.

[0064] The specific process and principle of steps S2 and S3 are received below.

[0065] Furthermore, calculating the pressure difference ratios of the other hydraulic cylinders and the reference hydraulic cylinder respectively based on the actual lifting heights of the other hydraulic cylinders and the actual lifting height of the reference hydraulic cylinder includes:

[0066] In the process of raising the preset height, the hydraulic oil flow rate flowing through the hydraulic cylinder is defined as Q. is the flow coefficient; is the valve opening area, is the pressure difference between the two ends of the hydraulic cylinder, is the density of the hydraulic oil, r is the radius of the hydraulic cylinder, and L is the actual lifting height of the hydraulic cylinder, then:

[0067] ;

[0068] Since the valve opening of the proportional valve corresponding to each hydraulic cylinder is the same, the pressure difference ratio is: , Where is the pressure difference at both ends of other hydraulic cylinders, Where is the pressure difference between the two ends of the reference hydraulic cylinder, is the radius of other hydraulic cylinders, is the radius of the base hydraulic cylinder, is the actual lifting height of other hydraulic cylinders, The actual lifting height of the reference hydraulic cylinder.

[0069] The derivation process is as follows:

[0070] ;

[0071] ;

[0072] ;

[0073] The valve opening of the proportional valve is the same, so the above formula can be further simplified to obtain .in 、 It can be measured, 、 This can be obtained in advance from the specifications of the hydraulic cylinder.

[0074] in Please refer to the product manual of the hydraulic cylinder.

[0075] Furthermore, on the premise that the other hydraulic cylinders and the reference hydraulic cylinder have the same preset lifting height, calculating the valve opening ratio of the other hydraulic cylinders and the reference hydraulic cylinder by using the pressure difference ratio includes:

[0076] according to ,get: ,in is the valve opening of the proportional valve of other hydraulic cylinders, The valve opening of the proportional valve of the reference hydraulic cylinder, The preset lifting height of other hydraulic cylinders, The preset lifting height of the reference hydraulic cylinder;

[0077] Since the other hydraulic cylinders and the reference hydraulic cylinder have the same preset lifting height, the valve opening ratio is obtained: .

[0078] Specifically, the pressure difference ratio is obtained in step S2. This step calculates the valve opening ratio by the pressure difference ratio. In this formula, since 、 Same, so:

[0079] ;

[0080] Further deduction of the deformation yields ,in Substituting the value calculated in the previous step into this formula yields the valve opening ratio. Using this ratio, along with the preset reference hydraulic cylinder valve opening, the individual valve openings can be calculated. This allows the valve opening to be determined to achieve the target height, eliminating the need to continuously adjust the valve opening based on the actual lift height during the lift process.

[0081] For example, if the valve opening ratio between one hydraulic cylinder and the reference hydraulic cylinder is 1.05, and the valve opening of the reference hydraulic cylinder is set to 80%, then the valve opening of this hydraulic cylinder is 84%.

[0082] And, in other embodiments,

[0083] Furthermore, driving each of the hydraulic cylinders to continue to rise to the target height includes:

[0084] The target height is divided into a lifting start section, a steady-state lifting section, and a lifting stop section, and each hydraulic cylinder is driven to rise to the height corresponding to the lifting start section, the steady-state lifting section, and the lifting stop section in sequence.

[0085] In this embodiment, the lift-start phase is the hydraulic cylinder's initial stage. During this phase, the hydraulic station must build up oil pressure in the hydraulic cylinder to overcome the static friction of the piston rod inside the cylinder. This then accelerates the piston rod to achieve the desired lifting speed. This phase is prone to vibration and other issues. The steady-state lift phase is the phase in which the piston rod rises at a constant speed. During this phase, the piston rod has overcome static friction, the acceleration is zero, and the piston rod moves at a constant speed. The lift-stop phase is the opposite of the lift-start phase, requiring the removal of oil pressure and the deceleration of the piston rod to reduce its lifting speed to zero.

[0086] Furthermore, a microphone array is provided around the lifting platform, and the goods are placed on a pallet;

[0087] In step S1, after placing the cargo on the lifting platform, the following steps are performed:

[0088] The microphone array collects the sound generated during the lowering of the tray;

[0089] Identify whether the sound contains the sound characteristics of a damaged pallet, and if so, proceed to the next step;

[0090] Analyzing the coordinates of a damage sound source of the sound of the pallet being damaged;

[0091] In step S4, after adjusting the valve openings of the proportional valves of other hydraulic cylinders according to the valve opening ratio, the following steps are executed:

[0092] Obtaining or calculating the placement coordinates of the pallet;

[0093] The valve opening corresponding to the lifting start section and the steady-state lifting section of each hydraulic cylinder is adjusted according to the damage sound source coordinates and the placement coordinates.

[0094] In this step, if the pallet is damaged or cracked during placement on the lifting platform via the handling system, it will emit a specific sound, such as a squeaking or humming sound. Furthermore, the pallet has a certain support area, and the location where the crack or damage appears on the pallet is generally located at a certain position on the pallet, such as a leg or a connection on the pallet. The coordinates of the damage sound source can be identified using the microphone array, and the location of the damage can be inferred from the coordinates of the damage sound source. During the lifting process, the lifting platform should avoid applying force to the pallet that tends to be directed towards the damaged location.

[0095] By obtaining the pallet's placement coordinates and combining them with the coordinates of the damage sound source, the location of the damage can be determined. By adjusting the opening of each proportional valve, the lifting force of the lifting platform on the pallet can be concentrated on the undamaged side of the pallet, thereby protecting the pallet.

[0096] Furthermore, obtaining or calculating the placement coordinates of the tray includes:

[0097] A camera is provided above the lifting platform, and the camera obtains an image of the lifting platform and obtains the placement coordinates of the pallet through image analysis.

[0098] Obtaining the placement coordinates of the tray through image analysis allows direct adoption of existing technologies, such as pattern recognition algorithms.

[0099] Furthermore, adjusting the valve opening of each hydraulic cylinder in the lifting start-up section and the steady-state lifting section according to the damage sound source coordinates and the placement coordinates includes:

[0100] Obtaining a pointing direction from the placement coordinates to the coordinates of the damaged sound source;

[0101] Obtaining the hydraulic cylinder with the shortest distance to the pointing direction;

[0102] Reduce the valve opening of the hydraulic cylinder with the shortest distance to the pointing direction in the lifting start-up section, increase the valve opening of the hydraulic cylinder diagonally opposite the hydraulic cylinder with the shortest distance to the pointing direction in the lifting start-up section, increase the valve opening of the hydraulic cylinder with the shortest distance to the pointing direction in the steady-state lifting section, and reduce the valve opening of the hydraulic cylinder diagonally opposite the hydraulic cylinder with the shortest distance to the pointing direction in the steady-state lifting section.

[0103] refer to Figure 2 , Figure 2 The black dots in the figure represent the placement coordinates (x1, y1), the hollow dots represent the damage source coordinates (x2, y2), and the arrows point in the direction from the placement coordinates to the damage source coordinates. By establishing a two-dimensional coordinate system on the upper surface of the lifting platform, the coordinates of each leg, that is, the corners of the lifting platform, can be obtained. Through the two-dimensional coordinate system and the coordinates of each hydraulic cylinder, the distance from the direction can be calculated. For example Figure 2 In the example, the distance between the lower right leg and the direction is D1, and the distance between the upper right leg and the direction is D2. If D2 is less than D1, then the hydraulic cylinder in the upper right corner is the hydraulic cylinder with the shortest distance to the pointing direction. Note that in this embodiment, the hydraulic cylinder with the shortest distance from the damage sound source coordinates to the pointing direction of the placement coordinates is not obtained.

[0104] Then, in the lifting start-up stage, by lowering the valve opening of the upper right hydraulic cylinder in the lifting start-up section and increasing the valve opening of the lower left hydraulic cylinder in the lifting start-up section, the starting speed of the lower left hydraulic cylinder can be slightly accelerated in the starting section, and the starting speed of the upper right hydraulic cylinder can be reduced, thereby concentrating the lifting force of the lifting platform on the pallet toward the lower left position of the pallet. By concentrating the force on the undamaged position of the pallet, the pallet can be prevented from being squeezed, deformed, and damaged by the goods, reducing the initial impact force of the hydraulic cylinder startup on the damaged position of the pallet, and avoiding crack expansion.

[0105] At the same time, due to the valve opening setting mentioned above, during the lifting start-up phase, the lifting path of the upper right hydraulic cylinder is reduced, and the lifting path of the lower left hydraulic cylinder is increased. Therefore, compensation is required in the steady-state lifting section. By increasing the valve opening of the upper right hydraulic cylinder in the steady-state lifting section and reducing the valve opening of the lower left hydraulic cylinder in the steady-state lifting section, the total lifting path of all hydraulic cylinders is finally made the same.

[0106] Specifically, in this step, the lifting start stage and the lifting stop stage can be set to 3-5 cm, and the rest is the steady-state lifting stage, which is generally more than 20 cm.

[0107] Preferably, the valve opening of the hydraulic cylinder shortest in the pointing direction is reduced by 10%-15% during the lift start-up phase, the valve opening of the hydraulic cylinder diagonally opposite the hydraulic cylinder shortest in the pointing direction is increased by 10%-15% during the lift start-up phase, the valve opening of the hydraulic cylinder shortest in the pointing direction is increased by 2%-5% during the steady-state lift phase, and the valve opening of the hydraulic cylinder diagonally opposite the hydraulic cylinder shortest in the pointing direction is reduced by 2%-5% during the steady-state lift phase. By ensuring that all hydraulic cylinders have the same total lift path during the longer steady-state lift phase, the height difference between the lift start-up phase and the steady-state lift phase can be slowly compensated, protecting the pallet and cargo.

[0108] Furthermore, a distance sensor is provided at the bottom of each support leg, and the distance sensor obtains the distance between the bottom of the support leg and the lifting platform to obtain the actual lifting height.

[0109] Furthermore, this embodiment divides the target height into several equal small segments, and executes a multi-hydraulic control axis millimeter-level synchronization control method in each segment, which can accurately control the millimeter-level synchronization of the multi-hydraulic control axes.

[0110] A lifting platform with millimeter-level synchronization of multiple hydraulically controlled axes is further provided, which implements the millimeter-level synchronization control method of multiple hydraulically controlled axes during operation.

[0111] Through the millimeter-level synchronous control method of multiple hydraulic control axes provided by this embodiment, the lifting curve of the hydraulic cylinder of each leg is referenced to Figure 3During the lifting process, the height difference of the hydraulic cylinders of each leg is always less than 2 mm. The overall lifting process is smooth and the lifting height of each leg tends to be consistent.

[0112] Compared with the PID control of the existing technology, the lifting curve of the hydraulic cylinder of each leg is referenced Figure 4 ,The maximum height difference of the existing technology is greater than 4 mm, and the overall lifting process vibrates, for example Figure 4 The leg represented by the middle brown curve lags behind the other legs several times, and then suddenly rises quickly to a height close to that of the other legs.

[0113] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0114] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0115] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0116] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0117] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms should not be understood as necessarily referring to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

Claims

1. A millimeter-level synchronous control method for multiple hydraulically controlled axes, characterized by: Used for lifting platform, the lifting platform is provided with outriggers, each outrigger is lifted and lowered by a corresponding hydraulic cylinder, and the hydraulic cylinders are respectively connected to the hydraulic station through proportional valves; The control method comprises the following steps: S1, placing cargo on the lifting platform, controlling the valve opening of the proportional valve corresponding to each hydraulic cylinder to be the same, controlling the hydraulic station to output hydraulic oil to the hydraulic cylinder through the proportional valve, and driving each hydraulic cylinder to first raise to a preset height; S2, obtaining the actual lifting height of each hydraulic cylinder, defining one of the hydraulic cylinders as a reference hydraulic cylinder, and calculating the pressure difference ratios of the other hydraulic cylinders and the reference hydraulic cylinder based on the actual lifting heights of the other hydraulic cylinders and the actual lifting height of the reference hydraulic cylinder; S3, on the premise that the other hydraulic cylinders and the reference hydraulic cylinder are raised to the same preset height, calculating the valve opening ratio of the other hydraulic cylinders and the reference hydraulic cylinder based on the pressure difference ratio; S4, adjusting the valve openings of the proportional valves of the other hydraulic cylinders according to the valve opening ratio, and driving each of the hydraulic cylinders to continue to rise to the target height; Driving each of the hydraulic cylinders to continue to rise to the target height includes: Divide the target height into a lifting start section, a steady-state lifting section, and a lifting stop section, and drive each hydraulic cylinder to sequentially rise to the heights corresponding to the lifting start section, the steady-state lifting section, and the lifting stop section; A microphone array is provided around the lifting platform, and the goods are placed on a pallet; In step S1, after placing the cargo on the lifting platform, the following steps are performed: The microphone array collects the sound generated during the lowering of the tray; Identify whether the sound contains the sound characteristics of a damaged pallet, and if so, proceed to the next step; Analyzing the coordinates of a damage sound source of the sound of the pallet being damaged; In step S4, after adjusting the valve openings of the proportional valves of other hydraulic cylinders according to the valve opening ratio, the following steps are executed: Obtaining or calculating the placement coordinates of the pallet; Adjust the valve opening corresponding to the lifting start section and the steady-state lifting section of each hydraulic cylinder according to the damage sound source coordinates and the placement coordinates; Adjusting the valve opening of each hydraulic cylinder in the lifting start-up section and the steady-state lifting section by using the damage sound source coordinates and the placement coordinates includes: Obtaining a pointing direction from the placement coordinates to the coordinates of the damaged sound source; Obtaining the hydraulic cylinder with the shortest distance to the pointing direction; Reduce the valve opening of the hydraulic cylinder with the shortest distance to the pointing direction in the lifting start-up section, increase the valve opening of the hydraulic cylinder diagonally opposite the hydraulic cylinder with the shortest distance to the pointing direction in the lifting start-up section, increase the valve opening of the hydraulic cylinder with the shortest distance to the pointing direction in the steady-state lifting section, and reduce the valve opening of the hydraulic cylinder diagonally opposite the hydraulic cylinder with the shortest distance to the pointing direction in the steady-state lifting section.

2. The millimeter-level synchronous control method for multiple hydraulically controlled axes according to claim 1, characterized in that: Defining one of the hydraulic cylinders as the reference hydraulic cylinder includes: Select the hydraulic cylinder whose actual lifting height is closest to the preset height as the reference hydraulic cylinder.

3. The millimeter-level synchronous control method for multiple hydraulically controlled axes according to claim 1, characterized in that: Calculating the pressure difference ratios of the other hydraulic cylinders and the reference hydraulic cylinder respectively based on the actual lifting heights of the other hydraulic cylinders and the actual lifting height of the reference hydraulic cylinder includes: In the process of raising the preset height, the hydraulic oil flow rate flowing through the hydraulic cylinder is defined as Q. is the flow coefficient; is the valve opening area, is the pressure difference between the two ends of the hydraulic cylinder, is the density of the hydraulic oil, r is the radius of the hydraulic cylinder, and L is the actual lifting height of the hydraulic cylinder, then: ； Since the valve opening of the proportional valve corresponding to each hydraulic cylinder is the same, the pressure difference ratio is: , Where is the pressure difference at both ends of other hydraulic cylinders, Where is the pressure difference between the two ends of the reference hydraulic cylinder, is the radius of other hydraulic cylinders, is the radius of the base hydraulic cylinder, is the actual lifting height of other hydraulic cylinders, The actual lifting height of the reference hydraulic cylinder.

4. The millimeter-level synchronous control method for multiple hydraulically controlled axes according to claim 3, characterized in that: On the premise that the preset lifting heights of the other hydraulic cylinders and the reference hydraulic cylinder are the same, calculating the valve opening ratio of the other hydraulic cylinders and the reference hydraulic cylinder by using the pressure difference ratio includes: according to ,get: ,in is the valve opening of the proportional valve of other hydraulic cylinders, The valve opening of the proportional valve of the reference hydraulic cylinder, The preset lifting height of other hydraulic cylinders, The preset lifting height of the reference hydraulic cylinder; Since the other hydraulic cylinders and the reference hydraulic cylinder have the same preset lifting height, the valve opening ratio is obtained: .

5. The millimeter-level synchronous control method for multiple hydraulically controlled axes according to claim 1, characterized in that: Obtaining or calculating the placement coordinates of the pallet includes: A camera is provided above the lifting platform, and the camera obtains an image of the lifting platform and obtains the placement coordinates of the pallet through image analysis.

6. The millimeter-level synchronous control method for multiple hydraulically controlled axes according to claim 1, characterized in that: A distance sensor is provided at the bottom of each support leg, and the distance sensor obtains the distance between the bottom of the support leg and the lifting platform to obtain the actual lifting height.

7. A lifting platform with millimeter-level synchronization of multiple hydraulically controlled axes, characterized by: When working, a millimeter-level synchronous control method for multiple hydraulically controlled axes as described in any one of claims 1-6 is implemented.

Images